[PATCH v17 1/8] Row pattern recognition patch for raw parser.

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[PATCH v17 1/8] Row pattern recognition patch for raw parser.
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* [PATCH v17 1/8] Row pattern recognition patch for raw parser.
@ 2024-04-28 11:00 Tatsuo Ishii <ishii@postgresql.org>
  0 siblings, 0 replies; 267+ messages in thread

From: Tatsuo Ishii @ 2024-04-28 11:00 UTC (permalink / raw)

---
 src/backend/parser/gram.y       | 221 ++++++++++++++++++++++++++++++--
 src/include/nodes/parsenodes.h  |  67 ++++++++++
 src/include/parser/kwlist.h     |   8 ++
 src/include/parser/parse_node.h |   1 +
 4 files changed, 285 insertions(+), 12 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e8b619926e..c09a0f7e4f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -680,6 +680,21 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				json_object_constructor_null_clause_opt
 				json_array_constructor_null_clause_opt
 
+%type <target>	row_pattern_measure_item
+				row_pattern_definition
+%type <node>	opt_row_pattern_common_syntax
+				opt_row_pattern_skip_to
+				row_pattern_subset_item
+				row_pattern_term
+%type <list>	opt_row_pattern_measures
+				row_pattern_measure_list
+				row_pattern_definition_list
+				opt_row_pattern_subset_clause
+				row_pattern_subset_list
+				row_pattern_subset_rhs
+				row_pattern
+%type <boolean>	opt_row_pattern_initial_or_seek
+				first_or_last
 
 /*
  * Non-keyword token types.  These are hard-wired into the "flex" lexer.
@@ -723,7 +738,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	CURRENT_TIME CURRENT_TIMESTAMP CURRENT_USER CURSOR CYCLE
 
 	DATA_P DATABASE DAY_P DEALLOCATE DEC DECIMAL_P DECLARE DEFAULT DEFAULTS
-	DEFERRABLE DEFERRED DEFINER DELETE_P DELIMITER DELIMITERS DEPENDS DEPTH DESC
+	DEFERRABLE DEFERRED DEFINE DEFINER DELETE_P DELIMITER DELIMITERS DEPENDS DEPTH DESC
 	DETACH DICTIONARY DISABLE_P DISCARD DISTINCT DO DOCUMENT_P DOMAIN_P
 	DOUBLE_P DROP
 
@@ -739,7 +754,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
 	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
-	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
+	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIAL INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
 
@@ -752,7 +767,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MERGE MERGE_ACTION METHOD
+	MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MEASURES MERGE MERGE_ACTION METHOD
 	MINUTE_P MINVALUE MODE MONTH_P MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NESTED NEW NEXT NFC NFD NFKC NFKD NO
@@ -764,9 +779,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	ORDER ORDINALITY OTHERS OUT_P OUTER_P
 	OVER OVERLAPS OVERLAY OVERRIDING OWNED OWNER
 
-	PARALLEL PARAMETER PARSER PARTIAL PARTITION PARTITIONS PASSING PASSWORD PATH
-	PERIOD PLACING PLAN PLANS POLICY
-
+	PARALLEL PARAMETER PARSER PARTIAL PARTITION PARTITIONS PASSING PASSWORD PAST
+	PATH PATTERN_P PERIOD PERMUTE PLACING PLAN PLANS POLICY
 	POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
 	PRIOR PRIVILEGES PROCEDURAL PROCEDURE PROCEDURES PROGRAM PUBLICATION
 
@@ -777,12 +791,13 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
-	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
+	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SEEK SELECT
 	SEQUENCE SEQUENCES
+
 	SERIALIZABLE SERVER SESSION SESSION_USER SET SETS SETOF SHARE SHOW
 	SIMILAR SIMPLE SKIP SMALLINT SNAPSHOT SOME SPLIT SOURCE SQL_P STABLE STANDALONE_P
 	START STATEMENT STATISTICS STDIN STDOUT STORAGE STORED STRICT_P STRING_P STRIP_P
-	SUBSCRIPTION SUBSTRING SUPPORT SYMMETRIC SYSID SYSTEM_P SYSTEM_USER
+	SUBSCRIPTION SUBSET SUBSTRING SUPPORT SYMMETRIC SYSID SYSTEM_P SYSTEM_USER
 
 	TABLE TABLES TABLESAMPLE TABLESPACE TARGET TEMP TEMPLATE TEMPORARY TEXT_P THEN
 	TIES TIME TIMESTAMP TO TRAILING TRANSACTION TRANSFORM
@@ -891,6 +906,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %nonassoc	UNBOUNDED NESTED /* ideally would have same precedence as IDENT */
 %nonassoc	IDENT PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP
 			SET KEYS OBJECT_P SCALAR VALUE_P WITH WITHOUT PATH
+			MEASURES AFTER INITIAL SEEK PATTERN_P
 %left		Op OPERATOR		/* multi-character ops and user-defined operators */
 %left		'+' '-'
 %left		'*' '/' '%'
@@ -16333,7 +16349,8 @@ over_clause: OVER window_specification
 		;
 
 window_specification: '(' opt_existing_window_name opt_partition_clause
-						opt_sort_clause opt_frame_clause ')'
+						opt_sort_clause opt_row_pattern_measures opt_frame_clause
+						opt_row_pattern_common_syntax ')'
 				{
 					WindowDef  *n = makeNode(WindowDef);
 
@@ -16341,10 +16358,12 @@ window_specification: '(' opt_existing_window_name opt_partition_clause
 					n->refname = $2;
 					n->partitionClause = $3;
 					n->orderClause = $4;
+					n->rowPatternMeasures = $5;
 					/* copy relevant fields of opt_frame_clause */
-					n->frameOptions = $5->frameOptions;
-					n->startOffset = $5->startOffset;
-					n->endOffset = $5->endOffset;
+					n->frameOptions = $6->frameOptions;
+					n->startOffset = $6->startOffset;
+					n->endOffset = $6->endOffset;
+					n->rpCommonSyntax = (RPCommonSyntax *)$7;
 					n->location = @1;
 					$$ = n;
 				}
@@ -16368,6 +16387,31 @@ opt_partition_clause: PARTITION BY expr_list		{ $$ = $3; }
 			| /*EMPTY*/								{ $$ = NIL; }
 		;
 
+/*
+ * ROW PATTERN_P MEASURES
+ */
+opt_row_pattern_measures: MEASURES row_pattern_measure_list	{ $$ = $2; }
+			| /*EMPTY*/								{ $$ = NIL; }
+		;
+
+row_pattern_measure_list:
+			row_pattern_measure_item
+					{ $$ = list_make1($1); }
+			| row_pattern_measure_list ',' row_pattern_measure_item
+					{ $$ = lappend($1, $3); }
+		;
+
+row_pattern_measure_item:
+			a_expr AS ColLabel
+				{
+					$$ = makeNode(ResTarget);
+					$$->name = $3;
+					$$->indirection = NIL;
+					$$->val = (Node *) $1;
+					$$->location = @1;
+				}
+		;
+
 /*
  * For frame clauses, we return a WindowDef, but only some fields are used:
  * frameOptions, startOffset, and endOffset.
@@ -16527,6 +16571,143 @@ opt_window_exclusion_clause:
 			| /*EMPTY*/				{ $$ = 0; }
 		;
 
+opt_row_pattern_common_syntax:
+opt_row_pattern_skip_to opt_row_pattern_initial_or_seek
+				PATTERN_P '(' row_pattern ')'
+				opt_row_pattern_subset_clause
+				DEFINE row_pattern_definition_list
+			{
+				RPCommonSyntax *n = makeNode(RPCommonSyntax);
+				n->rpSkipTo = ((RPCommonSyntax *)$1)->rpSkipTo;
+				n->rpSkipVariable = ((RPCommonSyntax *)$1)->rpSkipVariable;
+				n->initial = $2;
+				n->rpPatterns = $5;
+				n->rpSubsetClause = $7;
+				n->rpDefs = $9;
+				$$ = (Node *) n;
+			}
+			| /*EMPTY*/		{ $$ = NULL; }
+	;
+
+opt_row_pattern_skip_to:
+			AFTER MATCH SKIP TO NEXT ROW
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_NEXT_ROW;
+					n->rpSkipVariable = NULL;
+					$$ = (Node *) n;
+			}
+			| AFTER MATCH SKIP PAST LAST_P ROW
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_PAST_LAST_ROW;
+					n->rpSkipVariable = NULL;
+					$$ = (Node *) n;
+				}
+			| AFTER MATCH SKIP TO first_or_last ColId
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = $5? ST_FIRST_VARIABLE : ST_LAST_VARIABLE;
+					n->rpSkipVariable = $6;
+					$$ = (Node *) n;
+				}
+/*
+			| AFTER MATCH SKIP TO LAST_P ColId		%prec LAST_P
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_LAST_VARIABLE;
+					n->rpSkipVariable = $6;
+					$$ = n;
+				}
+			| AFTER MATCH SKIP TO ColId
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					n->rpSkipTo = ST_VARIABLE;
+					n->rpSkipVariable = $5;
+					$$ = n;
+				}
+*/
+			| /*EMPTY*/
+				{
+					RPCommonSyntax *n = makeNode(RPCommonSyntax);
+					/* temporary set default to ST_NEXT_ROW */
+					n->rpSkipTo = ST_PAST_LAST_ROW;
+					n->rpSkipVariable = NULL;
+					$$ = (Node *) n;
+				}
+	;
+
+first_or_last:
+			FIRST_P		{ $$ = true; }
+			| LAST_P	{ $$ = false; }
+	;
+
+opt_row_pattern_initial_or_seek:
+			INITIAL			{ $$ = true; }
+			| SEEK
+				{
+					ereport(ERROR,
+							(errcode(ERRCODE_SYNTAX_ERROR),
+							 errmsg("SEEK is not supported"),
+							 errhint("Use INITIAL."),
+							 parser_errposition(@1)));
+				}
+			| /*EMPTY*/		{ $$ = true; }
+		;
+
+row_pattern:
+			row_pattern_term							{ $$ = list_make1($1); }
+			| row_pattern row_pattern_term				{ $$ = lappend($1, $2); }
+		;
+
+row_pattern_term:
+			ColId	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "", (Node *)makeString($1), NULL, @1); }
+			| ColId '*'	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "*", (Node *)makeString($1), NULL, @1); }
+			| ColId '+'	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "+", (Node *)makeString($1), NULL, @1); }
+			| ColId '?'	{ $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "?", (Node *)makeString($1), NULL, @1); }
+		;
+
+opt_row_pattern_subset_clause:
+			SUBSET row_pattern_subset_list	{ $$ = $2; }
+			| /*EMPTY*/												{ $$ = NIL; }
+		;
+
+row_pattern_subset_list:
+			row_pattern_subset_item									{ $$ = list_make1($1); }
+			| row_pattern_subset_list ',' row_pattern_subset_item	{ $$ = lappend($1, $3); }
+			| /*EMPTY*/												{ $$ = NIL; }
+		;
+
+row_pattern_subset_item: ColId '=' '(' row_pattern_subset_rhs ')'
+			{
+				RPSubsetItem *n = makeNode(RPSubsetItem);
+				n->name = $1;
+				n->rhsVariable = $4;
+				$$ = (Node *) n;
+			}
+		;
+
+row_pattern_subset_rhs:
+			ColId								{ $$ = list_make1(makeStringConst($1, @1)); }
+			| row_pattern_subset_rhs ',' ColId	{ $$ = lappend($1, makeStringConst($3, @1)); }
+			| /*EMPTY*/							{ $$ = NIL; }
+		;
+
+row_pattern_definition_list:
+			row_pattern_definition										{ $$ = list_make1($1); }
+			| row_pattern_definition_list ',' row_pattern_definition	{ $$ = lappend($1, $3); }
+		;
+
+row_pattern_definition:
+			ColId AS a_expr
+				{
+					$$ = makeNode(ResTarget);
+					$$->name = $1;
+					$$->indirection = NIL;
+					$$->val = (Node *) $3;
+					$$->location = @1;
+				}
+		;
 
 /*
  * Supporting nonterminals for expressions.
@@ -17737,6 +17918,7 @@ unreserved_keyword:
 			| INDEXES
 			| INHERIT
 			| INHERITS
+			| INITIAL
 			| INLINE_P
 			| INPUT_P
 			| INSENSITIVE
@@ -17765,6 +17947,7 @@ unreserved_keyword:
 			| MATCHED
 			| MATERIALIZED
 			| MAXVALUE
+			| MEASURES
 			| MERGE
 			| METHOD
 			| MINUTE_P
@@ -17810,8 +17993,11 @@ unreserved_keyword:
 			| PARTITIONS
 			| PASSING
 			| PASSWORD
+			| PAST
 			| PATH
+			| PATTERN_P
 			| PERIOD
+			| PERMUTE
 			| PLAN
 			| PLANS
 			| POLICY
@@ -17864,6 +18050,7 @@ unreserved_keyword:
 			| SEARCH
 			| SECOND_P
 			| SECURITY
+			| SEEK
 			| SEQUENCE
 			| SEQUENCES
 			| SERIALIZABLE
@@ -17892,6 +18079,7 @@ unreserved_keyword:
 			| STRING_P
 			| STRIP_P
 			| SUBSCRIPTION
+			| SUBSET
 			| SUPPORT
 			| SYSID
 			| SYSTEM_P
@@ -18086,6 +18274,7 @@ reserved_keyword:
 			| CURRENT_USER
 			| DEFAULT
 			| DEFERRABLE
+			| DEFINE
 			| DESC
 			| DISTINCT
 			| DO
@@ -18249,6 +18438,7 @@ bare_label_keyword:
 			| DEFAULTS
 			| DEFERRABLE
 			| DEFERRED
+			| DEFINE
 			| DEFINER
 			| DELETE_P
 			| DELIMITER
@@ -18326,6 +18516,7 @@ bare_label_keyword:
 			| INDEXES
 			| INHERIT
 			| INHERITS
+			| INITIAL
 			| INITIALLY
 			| INLINE_P
 			| INNER_P
@@ -18380,6 +18571,7 @@ bare_label_keyword:
 			| MATCHED
 			| MATERIALIZED
 			| MAXVALUE
+			| MEASURES
 			| MERGE
 			| MERGE_ACTION
 			| METHOD
@@ -18437,8 +18629,11 @@ bare_label_keyword:
 			| PARTITIONS
 			| PASSING
 			| PASSWORD
+			| PAST
 			| PATH
+			| PATTERN_P
 			| PERIOD
+			| PERMUTE
 			| PLACING
 			| PLAN
 			| PLANS
@@ -18497,6 +18692,7 @@ bare_label_keyword:
 			| SCROLL
 			| SEARCH
 			| SECURITY
+			| SEEK
 			| SELECT
 			| SEQUENCE
 			| SEQUENCES
@@ -18531,6 +18727,7 @@ bare_label_keyword:
 			| STRING_P
 			| STRIP_P
 			| SUBSCRIPTION
+			| SUBSET
 			| SUBSTRING
 			| SUPPORT
 			| SYMMETRIC
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index af80a5d38e..7e7dcf3c77 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -550,6 +550,48 @@ typedef struct SortBy
 	ParseLoc	location;		/* operator location, or -1 if none/unknown */
 } SortBy;
 
+/*
+ * AFTER MATCH row pattern skip to types in row pattern common syntax
+ */
+typedef enum RPSkipTo
+{
+	ST_NONE,					/* AFTER MATCH omitted */
+	ST_NEXT_ROW,				/* SKIP TO NEXT ROW */
+	ST_PAST_LAST_ROW,			/* SKIP TO PAST LAST ROW */
+	ST_FIRST_VARIABLE,			/* SKIP TO FIRST variable name */
+	ST_LAST_VARIABLE,			/* SKIP TO LAST variable name */
+	ST_VARIABLE					/* SKIP TO variable name */
+}			RPSkipTo;
+
+/*
+ * Row Pattern SUBSET clause item
+ */
+typedef struct RPSubsetItem
+{
+	NodeTag		type;
+	char	   *name;			/* Row Pattern SUBSET clause variable name */
+	List	   *rhsVariable;	/* Row Pattern SUBSET rhs variables (list of
+								 * char *string) */
+}			RPSubsetItem;
+
+/*
+ * RowPatternCommonSyntax - raw representation of row pattern common syntax
+ *
+ */
+typedef struct RPCommonSyntax
+{
+	NodeTag		type;
+	RPSkipTo	rpSkipTo;		/* Row Pattern AFTER MATCH SKIP type */
+	char	   *rpSkipVariable; /* Row Pattern Skip To variable name, if any */
+	bool		initial;		/* true if <row pattern initial or seek> is
+								 * initial */
+	List	   *rpPatterns;		/* PATTERN variables (list of A_Expr) */
+	List	   *rpSubsetClause; /* row pattern subset clause (list of
+								 * RPSubsetItem), if any */
+	List	   *rpDefs;			/* row pattern definitions clause (list of
+								 * ResTarget) */
+}			RPCommonSyntax;
+
 /*
  * WindowDef - raw representation of WINDOW and OVER clauses
  *
@@ -565,6 +607,9 @@ typedef struct WindowDef
 	char	   *refname;		/* referenced window name, if any */
 	List	   *partitionClause;	/* PARTITION BY expression list */
 	List	   *orderClause;	/* ORDER BY (list of SortBy) */
+	List	   *rowPatternMeasures; /* row pattern measures (list of
+									 * ResTarget) */
+	RPCommonSyntax *rpCommonSyntax; /* row pattern common syntax */
 	int			frameOptions;	/* frame_clause options, see below */
 	Node	   *startOffset;	/* expression for starting bound, if any */
 	Node	   *endOffset;		/* expression for ending bound, if any */
@@ -1533,6 +1578,11 @@ typedef struct GroupingSet
  * the orderClause might or might not be copied (see copiedOrder); the framing
  * options are never copied, per spec.
  *
+ * "defineClause" is Row Pattern Recognition DEFINE clause (list of
+ * TargetEntry). TargetEntry.resname represents row pattern definition
+ * variable name. "patternVariable" and "patternRegexp" represents PATTERN
+ * clause.
+ *
  * The information relevant for the query jumbling is the partition clause
  * type and its bounds.
  */
@@ -1564,6 +1614,23 @@ typedef struct WindowClause
 	Index		winref;			/* ID referenced by window functions */
 	/* did we copy orderClause from refname? */
 	bool		copiedOrder pg_node_attr(query_jumble_ignore);
+	/* Row Pattern AFTER MACH SKIP clause */
+	RPSkipTo	rpSkipTo;		/* Row Pattern Skip To type */
+	char	   *rpSkipVariable; /* Row Pattern Skip To variable */
+	bool		initial;		/* true if <row pattern initial or seek> is
+								 * initial */
+	/* Row Pattern DEFINE clause (list of TargetEntry) */
+	List	   *defineClause;
+	/* Row Pattern DEFINE variable initial names (list of String) */
+	List	   *defineInitial;
+	/* Row Pattern PATTERN variable name (list of String) */
+	List	   *patternVariable;
+
+	/*
+	 * Row Pattern PATTERN regular expression quantifier ('+' or ''. list of
+	 * String)
+	 */
+	List	   *patternRegexp;
 } WindowClause;
 
 /*
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f9a4afd472..df49492629 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -129,6 +129,7 @@ PG_KEYWORD("default", DEFAULT, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("defaults", DEFAULTS, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("deferrable", DEFERRABLE, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("deferred", DEFERRED, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("define", DEFINE, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("definer", DEFINER, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("delete", DELETE_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("delimiter", DELIMITER, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -215,6 +216,7 @@ PG_KEYWORD("index", INDEX, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("indexes", INDEXES, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inherit", INHERIT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inherits", INHERITS, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("initial", INITIAL, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("initially", INITIALLY, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inline", INLINE_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("inner", INNER_P, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
@@ -273,6 +275,7 @@ PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("matched", MATCHED, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("measures", MEASURES, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("merge", MERGE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("merge_action", MERGE_ACTION, COL_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -338,8 +341,11 @@ PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("partitions", PARTITIONS, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("past", PAST, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("path", PATH, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("pattern", PATTERN_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("period", PERIOD, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("permute", PERMUTE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("plan", PLAN, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -401,6 +407,7 @@ PG_KEYWORD("scroll", SCROLL, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("search", SEARCH, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("second", SECOND_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("security", SECURITY, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("seek", SEEK, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("select", SELECT, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("sequence", SEQUENCE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("sequences", SEQUENCES, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -435,6 +442,7 @@ PG_KEYWORD("strict", STRICT_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("string", STRING_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("strip", STRIP_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("subscription", SUBSCRIPTION, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("subset", SUBSET, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("substring", SUBSTRING, COL_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("support", SUPPORT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("symmetric", SYMMETRIC, RESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/parser/parse_node.h b/src/include/parser/parse_node.h
index 5b781d87a9..66935afff8 100644
--- a/src/include/parser/parse_node.h
+++ b/src/include/parser/parse_node.h
@@ -51,6 +51,7 @@ typedef enum ParseExprKind
 	EXPR_KIND_WINDOW_FRAME_RANGE,	/* window frame clause with RANGE */
 	EXPR_KIND_WINDOW_FRAME_ROWS,	/* window frame clause with ROWS */
 	EXPR_KIND_WINDOW_FRAME_GROUPS,	/* window frame clause with GROUPS */
+	EXPR_KIND_RPR_DEFINE,		/* DEFINE */
 	EXPR_KIND_SELECT_TARGET,	/* SELECT target list item */
 	EXPR_KIND_INSERT_TARGET,	/* INSERT target list item */
 	EXPR_KIND_UPDATE_SOURCE,	/* UPDATE assignment source item */
-- 
2.25.1


----Next_Part(Sun_Apr_28_20_28_26_2024_444)--
Content-Type: Text/X-Patch; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="v17-0002-Row-pattern-recognition-patch-parse-analysis.patch"



^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

* [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup.
@ 2024-05-18 01:41 Thomas Munro <thomas.munro@gmail.com>
  0 siblings, 0 replies; 267+ messages in thread

From: Thomas Munro @ 2024-05-18 01:41 UTC (permalink / raw)

When backend processes were launched in EXEC_BACKEND builds, they would
run LocalProcessControlFile() to read in pg_control and extract several
important settings.

This happens too early to acquire ControlFileLock, and the postmaster is
also not allowed to acquire ControlFileLock, so it can't safely take a
copy to give to the child.

Instead, pass down the "proto-controlfile" that was read by the
postmaster in LocalProcessControlFile().  Introduce functions
ExportProtoControlFile() and ImportProtoControlFile() to allow that.
Subprocesses will extract information from that, and then later attach
to the current control file in shared memory.

Reported-by: Melanie Plageman <melanieplageman@gmail.com> per Windows CI failure
Discussion: https://postgr.es/m/CAAKRu_YNGwEYrorQYza_W8tU%2B%3DtoXRHG8HpyHC-KDbZqA_ZVSA%40mail.gmail.com
---
 src/backend/access/transam/xlog.c       | 46 +++++++++++++++++++++++--
 src/backend/postmaster/launch_backend.c | 21 +++++++----
 src/include/access/xlog.h               |  5 +++
 3 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 13ec6225b85..e52517eb9c1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -575,6 +575,10 @@ static WALInsertLockPadded *WALInsertLocks = NULL;
  */
 static ControlFileData *ControlFile = NULL;
 
+#ifdef EXEC_BACKEND
+static ControlFileData *ProtoControlFile = NULL;
+#endif
+
 /*
  * Calculate the amount of space left on the page after 'endptr'. Beware
  * multiple evaluation!
@@ -692,6 +696,7 @@ static bool PerformRecoveryXLogAction(void);
 static void InitControlFile(uint64 sysidentifier, uint32 data_checksum_version);
 static void WriteControlFile(void);
 static void ReadControlFile(void);
+static void ScanControlFile(void);
 static void UpdateControlFile(void);
 static char *str_time(pg_time_t tnow, char *buf, size_t bufsize);
 
@@ -4385,9 +4390,7 @@ WriteControlFile(void)
 static void
 ReadControlFile(void)
 {
-	pg_crc32c	crc;
 	int			fd;
-	char		wal_segsz_str[20];
 	int			r;
 
 	/*
@@ -4420,6 +4423,15 @@ ReadControlFile(void)
 
 	close(fd);
 
+	ScanControlFile();
+}
+
+static void
+ScanControlFile(void)
+{
+	static char wal_segsz_str[20];
+	pg_crc32c	crc;
+
 	/*
 	 * Check for expected pg_control format version.  If this is wrong, the
 	 * CRC check will likely fail because we'll be checking the wrong number
@@ -4941,8 +4953,33 @@ LocalProcessControlFile(bool reset)
 	Assert(reset || ControlFile == NULL);
 	ControlFile = palloc_object(ControlFileData);
 	ReadControlFile();
+
+#ifdef EXEC_BACKEND
+	/* We need to be able to give this to subprocesses. */
+	ProtoControlFile = ControlFile;
+#endif
 }
 
+#ifdef EXEC_BACKEND
+void
+ExportProtoControlFile(ControlFileData *copy)
+{
+	*copy = *ProtoControlFile;
+}
+
+/*
+ * Like LocalProcessControlFile(), but used early in EXEC_BACKEND children's
+ * startup.  This receives the same file that the postmaster first read.
+ */
+void
+ImportProtoControlFile(const ControlFileData *copy)
+{
+	ControlFile = palloc(sizeof(ControlFileData));
+	*ControlFile = *copy;
+	ScanControlFile();
+}
+#endif
+
 /*
  * Get the wal_level from the control file. For a standby, this value should be
  * considered as its active wal_level, because it may be different from what
@@ -5061,7 +5098,12 @@ XLOGShmemInit(void)
 	if (localControlFile)
 	{
 		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+#ifdef EXEC_BACKEND
+		/* We still hold a reference to give to subprocesses. */
+		Assert(ProtoControlFile == localControlFile);
+#else
 		pfree(localControlFile);
+#endif
 	}
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 45690b11c99..e08a405f949 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -33,6 +33,9 @@
 
 #include <unistd.h>
 
+#include "access/xlog.h"
+#include "catalog/pg_control.h"
+#include "common/file_utils.h"
 #include "libpq/libpq-be.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -133,6 +136,14 @@ typedef struct
 
 	int			MyPMChildSlot;
 
+	/*
+	 * A copy of the ControlFileData from early in Postmaster startup.  We
+	 * need to access its contents it at a phase of initialization before we
+	 * are allowed to acquire LWLocks, so we can't just use shared memory or
+	 * read the file from disk.
+	 */
+	ControlFileData proto_controlfile;
+
 	/*
 	 * These are only used by backend processes, but are here because passing
 	 * a socket needs some special handling on Windows. 'client_sock' is an
@@ -659,12 +670,6 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	checkDataDir();
 
-	/*
-	 * (re-)read control file, as it contains config. The postmaster will
-	 * already have read this, but this process doesn't know about that.
-	 */
-	LocalProcessControlFile(false);
-
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
@@ -752,6 +757,8 @@ save_backend_variables(BackendParameters *param,
 	param->MaxBackends = MaxBackends;
 	param->num_pmchild_slots = num_pmchild_slots;
 
+	ExportProtoControlFile(&param->proto_controlfile);
+
 #ifdef WIN32
 	param->PostmasterHandle = PostmasterHandle;
 	if (!write_duplicated_handle(&param->initial_signal_pipe,
@@ -1026,6 +1033,8 @@ restore_backend_variables(BackendParameters *param)
 
 	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
 
+	ImportProtoControlFile(&param->proto_controlfile);
+
 	/*
 	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
 	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index fdfb572467b..f1f3ad4e96e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -208,6 +208,7 @@ typedef enum WALAvailability
 
 struct XLogRecData;
 struct XLogReaderState;
+struct ControlFileData;
 
 extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 								   XLogRecPtr fpw_lsn,
@@ -250,6 +251,10 @@ extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(uint32 data_checksum_version);
 extern void InitializeWalConsistencyChecking(void);
 extern void LocalProcessControlFile(bool reset);
+#ifdef EXEC_BACKEND
+extern void ExportProtoControlFile(struct ControlFileData *copy);
+extern void ImportProtoControlFile(const struct ControlFileData *copy);
+#endif
 extern WalLevel GetActiveWalLevelOnStandby(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
-- 
2.47.3


--dhbc6bswyy6qufwn--





^ permalink  raw  reply  [nested|flat] 267+ messages in thread

end of thread, other threads:[~2024-05-18 01:41 UTC | newest]

Thread overview: 267+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2024-04-28 11:00 [PATCH v17 1/8] Row pattern recognition patch for raw parser. Tatsuo Ishii <ishii@postgresql.org>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>
2024-05-18 01:41 [PATCH v2] Fix pg_control corruption in EXEC_BACKEND startup. Thomas Munro <thomas.munro@gmail.com>

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