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Fix failure to guarantee that a checkpoint will write out pg_clog updates

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for transaction commits that occurred just before the checkpoint.  This is
an EXTREMELY serious bug --- kudos to Satoshi Okada for creating a
reproducible test case to prove its existence.
This commit is contained in:
Tom Lane
2004-08-11 04:08:02 +00:00
parent a1dd58e509
commit d508e0ddd2
3 changed files with 47 additions and 10 deletions
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18
src/backend/access/transam/xlog.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.125.2.1 2004/02/23 23:03:43 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.125.2.2 2004/08/11 04:08:00 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -3159,6 +3159,15 @@ CreateCheckPoint(bool shutdown, bool force)
checkPoint.ThisStartUpID = ThisStartUpID;
checkPoint.time = time(NULL);
/*
* We must hold CheckpointStartLock while determining the checkpoint
* REDO pointer. This ensures that any concurrent transaction commits
* will be either not yet logged, or logged and recorded in pg_clog.
* See notes in RecordTransactionCommit().
*/
LWLockAcquire(CheckpointStartLock, LW_EXCLUSIVE);
/* And we need WALInsertLock too */
LWLockAcquire(WALInsertLock, LW_EXCLUSIVE);
/*
@ -3191,6 +3200,7 @@ CreateCheckPoint(bool shutdown, bool force)
ControlFile->checkPointCopy.redo.xrecoff)
{
LWLockRelease(WALInsertLock);
LWLockRelease(CheckpointStartLock);
LWLockRelease(CheckpointLock);
END_CRIT_SECTION();
return;
@ -3258,11 +3268,13 @@ CreateCheckPoint(bool shutdown, bool force)
#endif
/*
* Now we can release insert lock, allowing other xacts to proceed
* even while we are flushing disk buffers.
* Now we can release insert lock and checkpoint start lock, allowing
* other xacts to proceed even while we are flushing disk buffers.
*/
LWLockRelease(WALInsertLock);
LWLockRelease(CheckpointStartLock);
/*
* Get the other info we need for the checkpoint record.
*/