Subject: [PATCH v2 1/3] Allow wait event set to be registered to resource owner

From: Kyotaro Horiguchi <[email-masked]>
Date: Mon, 22 May 2017 12:42:58 +0900

WaitEventSet needs to be released using resource owner for a certain
case. This change adds WaitEventSet reowner and allow the creator of a
WaitEventSet to specify a resource owner.
---
 src/backend/libpq/pqcomm.c                    |  2 +-
 src/backend/storage/ipc/latch.c               | 18 ++++-
 src/backend/storage/lmgr/condition_variable.c |  2 +-
 src/backend/utils/resowner/resowner.c         | 67 +++++++++++++++++++
 src/include/storage/latch.h                   |  4 +-
 src/include/utils/resowner_private.h          |  8 +++
 6 files changed, 96 insertions(+), 5 deletions(-)

diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index 7717bb2719..16aefb03ee 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -218,7 +218,7 @@ pq_init(void)
 				(errmsg("could not set socket to nonblocking mode: %m")));
 #endif
 
-	FeBeWaitSet = CreateWaitEventSet(TopMemoryContext, 3);
+	FeBeWaitSet = CreateWaitEventSet(TopMemoryContext, NULL, 3);
 	AddWaitEventToSet(FeBeWaitSet, WL_SOCKET_WRITEABLE, MyProcPort->sock,
 					  NULL, NULL);
 	AddWaitEventToSet(FeBeWaitSet, WL_LATCH_SET, -1, MyLatch, NULL);
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index 046ca5c6c7..9c10bd5fcf 100644
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -56,6 +56,7 @@
 #include "storage/latch.h"
 #include "storage/pmsignal.h"
 #include "storage/shmem.h"
+#include "utils/resowner_private.h"
 
 /*
  * Select the fd readiness primitive to use. Normally the "most modern"
@@ -84,6 +85,8 @@ struct WaitEventSet
 	int			nevents;		/* number of registered events */
 	int			nevents_space;	/* maximum number of events in this set */
 
+	ResourceOwner	resowner;	/* Resource owner */
+
 	/*
 	 * Array, of nevents_space length, storing the definition of events this
 	 * set is waiting for.
@@ -393,7 +396,7 @@ WaitLatchOrSocket(Latch *latch, int wakeEvents, pgsocket sock,
 	int			ret = 0;
 	int			rc;
 	WaitEvent	event;
-	WaitEventSet *set = CreateWaitEventSet(CurrentMemoryContext, 3);
+	WaitEventSet *set = CreateWaitEventSet(CurrentMemoryContext, NULL, 3);
 
 	if (wakeEvents & WL_TIMEOUT)
 		Assert(timeout >= 0);
@@ -560,12 +563,15 @@ ResetLatch(Latch *latch)
  * WaitEventSetWait().
  */
 WaitEventSet *
-CreateWaitEventSet(MemoryContext context, int nevents)
+CreateWaitEventSet(MemoryContext context, ResourceOwner res, int nevents)
 {
 	WaitEventSet *set;
 	char	   *data;
 	Size		sz = 0;
 
+	if (res)
+		ResourceOwnerEnlargeWESs(res);
+
 	/*
 	 * Use MAXALIGN size/alignment to guarantee that later uses of memory are
 	 * aligned correctly. E.g. epoll_event might need 8 byte alignment on some
@@ -680,6 +686,11 @@ CreateWaitEventSet(MemoryContext context, int nevents)
 	StaticAssertStmt(WSA_INVALID_EVENT == NULL, "");
 #endif
 
+	/* Register this wait event set if requested */
+	set->resowner = res;
+	if (res)
+		ResourceOwnerRememberWES(set->resowner, set);
+
 	return set;
 }
 
@@ -725,6 +736,9 @@ FreeWaitEventSet(WaitEventSet *set)
 	}
 #endif
 
+	if (set->resowner != NULL)
+		ResourceOwnerForgetWES(set->resowner, set);
+
 	pfree(set);
 }
 
diff --git a/src/backend/storage/lmgr/condition_variable.c b/src/backend/storage/lmgr/condition_variable.c
index 37b6a4eecd..fcc92138fe 100644
--- a/src/backend/storage/lmgr/condition_variable.c
+++ b/src/backend/storage/lmgr/condition_variable.c
@@ -70,7 +70,7 @@ ConditionVariablePrepareToSleep(ConditionVariable *cv)
 	{
 		WaitEventSet *new_event_set;
 
-		new_event_set = CreateWaitEventSet(TopMemoryContext, 2);
+		new_event_set = CreateWaitEventSet(TopMemoryContext, NULL, 2);
 		AddWaitEventToSet(new_event_set, WL_LATCH_SET, PGINVALID_SOCKET,
 						  MyLatch, NULL);
 		AddWaitEventToSet(new_event_set, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET,
diff --git a/src/backend/utils/resowner/resowner.c b/src/backend/utils/resowner/resowner.c
index 3c39e48825..035e83f4f8 100644
--- a/src/backend/utils/resowner/resowner.c
+++ b/src/backend/utils/resowner/resowner.c
@@ -128,6 +128,7 @@ typedef struct ResourceOwnerData
 	ResourceArray filearr;		/* open temporary files */
 	ResourceArray dsmarr;		/* dynamic shmem segments */
 	ResourceArray jitarr;		/* JIT contexts */
+	ResourceArray wesarr;		/* wait event sets */
 
 	/* We can remember up to MAX_RESOWNER_LOCKS references to local locks. */
 	int			nlocks;			/* number of owned locks */
@@ -175,6 +176,7 @@ static void PrintTupleDescLeakWarning(TupleDesc tupdesc);
 static void PrintSnapshotLeakWarning(Snapshot snapshot);
 static void PrintFileLeakWarning(File file);
 static void PrintDSMLeakWarning(dsm_segment *seg);
+static void PrintWESLeakWarning(WaitEventSet *events);

 /*****************************************************************************
@@ -444,6 +446,7 @@ ResourceOwnerCreate(ResourceOwner parent, const char *name)
 	ResourceArrayInit(&(owner->filearr), FileGetDatum(-1));
 	ResourceArrayInit(&(owner->dsmarr), PointerGetDatum(NULL));
 	ResourceArrayInit(&(owner->jitarr), PointerGetDatum(NULL));
+	ResourceArrayInit(&(owner->wesarr), PointerGetDatum(NULL));
 
 	return owner;
 }
@@ -553,6 +556,16 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 
 			jit_release_context(context);
 		}
+
+		/* Ditto for wait event sets */
+		while (ResourceArrayGetAny(&(owner->wesarr), &foundres))
+		{
+			WaitEventSet *event = (WaitEventSet *) DatumGetPointer(foundres);
+
+			if (isCommit)
+				PrintWESLeakWarning(event);
+			FreeWaitEventSet(event);
+		}
 	}
 	else if (phase == RESOURCE_RELEASE_LOCKS)
 	{
@@ -701,6 +714,7 @@ ResourceOwnerDelete(ResourceOwner owner)
 	Assert(owner->filearr.nitems == 0);
 	Assert(owner->dsmarr.nitems == 0);
 	Assert(owner->jitarr.nitems == 0);
+	Assert(owner->wesarr.nitems == 0);
 	Assert(owner->nlocks == 0 || owner->nlocks == MAX_RESOWNER_LOCKS + 1);
 
 	/*
@@ -728,6 +742,7 @@ ResourceOwnerDelete(ResourceOwner owner)
 	ResourceArrayFree(&(owner->filearr));
 	ResourceArrayFree(&(owner->dsmarr));
 	ResourceArrayFree(&(owner->jitarr));
+	ResourceArrayFree(&(owner->wesarr));
 
 	pfree(owner);
 }
@@ -1346,3 +1361,55 @@ ResourceOwnerForgetJIT(ResourceOwner owner, Datum handle)
 		elog(ERROR, "JIT context %p is not owned by resource owner %s",
 			 DatumGetPointer(handle), owner->name);
 }
+
+/*
+ * wait event set reference array.
+ *
+ * This is separate from actually inserting an entry because if we run out
+ * of memory, it's critical to do so *before* acquiring the resource.
+ */
+void
+ResourceOwnerEnlargeWESs(ResourceOwner owner)
+{
+	ResourceArrayEnlarge(&(owner->wesarr));
+}
+
+/*
+ * Remember that a wait event set is owned by a ResourceOwner
+ *
+ * Caller must have previously done ResourceOwnerEnlargeWESs()
+ */
+void
+ResourceOwnerRememberWES(ResourceOwner owner, WaitEventSet *events)
+{
+	ResourceArrayAdd(&(owner->wesarr), PointerGetDatum(events));
+}
+
+/*
+ * Forget that a wait event set is owned by a ResourceOwner
+ */
+void
+ResourceOwnerForgetWES(ResourceOwner owner, WaitEventSet *events)
+{
+	/*
+	 * XXXX: There's no property to show as an identier of a wait event set,
+	 * use its pointer instead.
+	 */
+	if (!ResourceArrayRemove(&(owner->wesarr), PointerGetDatum(events)))
+		elog(ERROR, "wait event set %p is not owned by resource owner %s",
+			 events, owner->name);
+}
+
+/*
+ * Debugging subroutine
+ */
+static void
+PrintWESLeakWarning(WaitEventSet *events)
+{
+	/*
+	 * XXXX: There's no property to show as an identier of a wait event set,
+	 * use its pointer instead.
+	 */
+	elog(WARNING, "wait event set leak: %p still referenced",
+		 events);
+}
diff --git a/src/include/storage/latch.h b/src/include/storage/latch.h
index 46ae56cae3..b1b8375768 100644
--- a/src/include/storage/latch.h
+++ b/src/include/storage/latch.h
@@ -101,6 +101,7 @@
 #define LATCH_H
 
 #include <signal.h>
+#include "utils/resowner.h"
 
 /*
  * Latch structure should be treated as opaque and only accessed through
@@ -163,7 +164,8 @@ extern void DisownLatch(Latch *latch);
 extern void SetLatch(Latch *latch);
 extern void ResetLatch(Latch *latch);
 
-extern WaitEventSet *CreateWaitEventSet(MemoryContext context, int nevents);
+extern WaitEventSet *CreateWaitEventSet(MemoryContext context,
+										ResourceOwner res, int nevents);
 extern void FreeWaitEventSet(WaitEventSet *set);
 extern int	AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd,
 							  Latch *latch, void *user_data);
diff --git a/src/include/utils/resowner_private.h b/src/include/utils/resowner_private.h
index a781a7a2aa..7d19dadd57 100644
--- a/src/include/utils/resowner_private.h
+++ b/src/include/utils/resowner_private.h
@@ -18,6 +18,7 @@
 
 #include "storage/dsm.h"
 #include "storage/fd.h"
+#include "storage/latch.h"
 #include "storage/lock.h"
 #include "utils/catcache.h"
 #include "utils/plancache.h"
@@ -95,4 +96,11 @@ extern void ResourceOwnerRememberJIT(ResourceOwner owner,
 extern void ResourceOwnerForgetJIT(ResourceOwner owner,
 								   Datum handle);
 
+/* support for wait event set management */
+extern void ResourceOwnerEnlargeWESs(ResourceOwner owner);
+extern void ResourceOwnerRememberWES(ResourceOwner owner,
+						 WaitEventSet *);
+extern void ResourceOwnerForgetWES(ResourceOwner owner,
+					   WaitEventSet *);
+
 #endif							/* RESOWNER_PRIVATE_H */
-- 
2.18.2

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