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Commit8d86a96

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Adjust CreateCheckpoint so that buffer dumping activities and cleanup of
dead xlog segments are not considered part of a critical section. It isnot necessary to force a database-wide panic if we get a failure in theseoperations. Per recent trouble reports.
1 parent199f24e commit8d86a96

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1 file changed

+31
-4
lines changed
  • src/backend/access/transam

1 file changed

+31
-4
lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 31 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
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*
10-
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.114 2003/04/25 19:45:08 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.115 2003/05/10 18:01:31 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -2973,11 +2973,13 @@ CreateCheckPoint(bool shutdown, bool force)
29732973
elog(ERROR,"CreateCheckPoint: cannot be called inside transaction block");
29742974

29752975
/*
2976+
* Acquire CheckpointLock to ensure only one checkpoint happens at a time.
2977+
*
29762978
* The CheckpointLock can be held for quite a while, which is not good
29772979
* because we won't respond to a cancel/die request while waiting for
29782980
* an LWLock. (But the alternative of using a regular lock won't work
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* for background checkpoint processes, which are not regular
2980-
* backends.) So, rather than use a plain LWLockAcquire, use this
2982+
* backends.)So, rather than use a plain LWLockAcquire, use this
29812983
* kluge to allow an interrupt to be accepted while we are waiting:
29822984
*/
29832985
while (!LWLockConditionalAcquire(CheckpointLock,LW_EXCLUSIVE))
@@ -2986,6 +2988,9 @@ CreateCheckPoint(bool shutdown, bool force)
29862988
sleep(1);
29872989
}
29882990

2991+
/*
2992+
* Use a critical section to force system panic if we have trouble.
2993+
*/
29892994
START_CRIT_SECTION();
29902995

29912996
if (shutdown)
@@ -3056,6 +3061,13 @@ CreateCheckPoint(bool shutdown, bool force)
30563061
/*
30573062
* Here we update the shared RedoRecPtr for future XLogInsert calls;
30583063
* this must be done while holding the insert lock AND the info_lck.
3064+
*
3065+
* Note: if we fail to complete the checkpoint, RedoRecPtr will be
3066+
* left pointing past where it really needs to point. This is okay;
3067+
* the only consequence is that XLogInsert might back up whole buffers
3068+
* that it didn't really need to. We can't postpone advancing RedoRecPtr
3069+
* because XLogInserts that happen while we are dumping buffers must
3070+
* assume that their buffer changes are not included in the checkpoint.
30593071
*/
30603072
{
30613073
/* use volatile pointer to prevent code rearrangement */
@@ -3094,6 +3106,9 @@ CreateCheckPoint(bool shutdown, bool force)
30943106
*/
30953107
LWLockRelease(WALInsertLock);
30963108

3109+
/*
3110+
* Get the other info we need for the checkpoint record.
3111+
*/
30973112
LWLockAcquire(XidGenLock,LW_SHARED);
30983113
checkPoint.nextXid=ShmemVariableCache->nextXid;
30993114
LWLockRelease(XidGenLock);
@@ -3107,10 +3122,18 @@ CreateCheckPoint(bool shutdown, bool force)
31073122
/*
31083123
* Having constructed the checkpoint record, ensure all shmem disk
31093124
* buffers and commit-log buffers are flushed to disk.
3125+
*
3126+
* This I/O could fail for various reasons. If so, we will fail to
3127+
* complete the checkpoint, but there is no reason to force a system
3128+
* panic. Accordingly, exit critical section while doing it.
31103129
*/
3130+
END_CRIT_SECTION();
3131+
31113132
CheckPointCLOG();
31123133
FlushBufferPool();
31133134

3135+
START_CRIT_SECTION();
3136+
31143137
/*
31153138
* Now insert the checkpoint record into XLOG.
31163139
*/
@@ -3166,6 +3189,12 @@ CreateCheckPoint(bool shutdown, bool force)
31663189
UpdateControlFile();
31673190
LWLockRelease(ControlFileLock);
31683191

3192+
/*
3193+
* We are now done with critical updates; no need for system panic if
3194+
* we have trouble while fooling with offline log segments.
3195+
*/
3196+
END_CRIT_SECTION();
3197+
31693198
/*
31703199
* Delete offline log files (those no longer needed even for previous
31713200
* checkpoint).
@@ -3185,8 +3214,6 @@ CreateCheckPoint(bool shutdown, bool force)
31853214
PreallocXlogFiles(recptr);
31863215

31873216
LWLockRelease(CheckpointLock);
3188-
3189-
END_CRIT_SECTION();
31903217
}
31913218

31923219
/*

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