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commit    85cc9c4e2da88d7a1d160e091ec41f3fed7d271b
Author:   Amit Kapila <akapila@postgresql.org>
Date:     Fri Sep 28 11:24:40 2018 +0000
First released in: 12.0, 9.5.15, 9.6.11, 10.6, 11.0

    Fix assertion failure when updating full_page_writes for checkpointer.
    
    When the checkpointer receives a SIGHUP signal to update its configuration,
    it may need to update the shared memory for full_page_writes and need to
    write a WAL record for it.  Now, it is quite possible that the XLOG
    machinery has not been initialized by that time and it will lead to
    assertion failure while doing that.  Fix is to allow the initialization of
    the XLOG machinery outside critical section.
    
    This bug has been introduced by the commit 2c03216d83 which added the XLOG
    machinery initialization in RecoveryInProgress code path.
    
    Reported-by: Dilip Kumar
    Author: Dilip Kumar
    Reviewed-by: Michael Paquier and Amit Kapila
    Backpatch-through: 9.5
    Discussion: https://postgr.es/m/CAFiTN-u4BA8KXcQUWDPNgaKAjDXC=C2whnzBM8TAcv=stckYUw@mail.gmail.com


 src/backend/access/transam/xlog.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3fccb856adb..92a3b7954a9 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9219,6 +9219,7 @@ void
 UpdateFullPageWrites(void)
 {
 	XLogCtlInsert *Insert = &XLogCtl->Insert;
+	bool		recoveryInProgress;
 
 	/*
 	 * Do nothing if full_page_writes has not been changed.
@@ -9230,6 +9231,13 @@ UpdateFullPageWrites(void)
 	if (fullPageWrites == Insert->fullPageWrites)
 		return;
 
+	/*
+	 * Perform this outside critical section so that the WAL insert
+	 * initialization done by RecoveryInProgress() doesn't trigger an
+	 * assertion failure.
+	 */
+	recoveryInProgress = RecoveryInProgress();
+
 	START_CRIT_SECTION();
 
 	/*
@@ -9250,7 +9258,7 @@ UpdateFullPageWrites(void)
 	 * Write an XLOG_FPW_CHANGE record. This allows us to keep track of
 	 * full_page_writes during archive recovery, if required.
 	 */
-	if (XLogStandbyInfoActive() && !RecoveryInProgress())
+	if (XLogStandbyInfoActive() && !recoveryInProgress)
 	{
 		XLogBeginInsert();
 		XLogRegisterData((char *) (&fullPageWrites), sizeof(bool));


[parent: ed9d6d621a09]