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Fix race condition in relcache init file invalidation.

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The previous code tried to synchronize by unlinking the init file twice,
but that doesn't actually work: it leaves a window wherein a third process
could read the already-stale init file but miss the SI messages that would
tell it the data is stale.  The result would be bizarre failures in catalog
accesses, typically "could not read block 0 in file ..." later during
startup.

Instead, hold RelCacheInitLock across both the unlink and the sending of
the SI messages.  This is more straightforward, and might even be a bit
faster since only one unlink call is needed.

This has been wrong since it was put in (in 2002!), so back-patch to all
supported releases.
This commit is contained in:
Tom Lane
2011-08-16 13:11:54 -04:00
parent 1bb69245ab
commit 2ada6779c5
4 changed files with 57 additions and 49 deletions
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33
src/backend/utils/cache/inval.c vendored
View File

@ -854,24 +854,12 @@ xactGetCommittedInvalidationMessages(SharedInvalidationMessage **msgs,
return numSharedInvalidMessagesArray;
}
#define RecoveryRelationCacheInitFileInvalidate(dbo, tbo, tf) \
{ \
DatabasePath = GetDatabasePath(dbo, tbo); \
elog(trace_recovery(DEBUG4), "removing relcache init file in %s", DatabasePath); \
RelationCacheInitFileInvalidate(tf); \
pfree(DatabasePath); \
}
/*
* ProcessCommittedInvalidationMessages is executed by xact_redo_commit()
* to process invalidation messages added to commit records.
*
* Relcache init file invalidation requires processing both
* before and after we send the SI messages. See AtEOXact_Inval()
*
* We deliberately avoid SetDatabasePath() since it is intended to be used
* only once by normal backends, so we set DatabasePath directly then
* pfree after use. See RecoveryRelationCacheInitFileInvalidate() macro.
*/
void
ProcessCommittedInvalidationMessages(SharedInvalidationMessage *msgs,
@ -885,12 +873,25 @@ ProcessCommittedInvalidationMessages(SharedInvalidationMessage *msgs,
(RelcacheInitFileInval ? " and relcache file invalidation" : ""));
if (RelcacheInitFileInval)
RecoveryRelationCacheInitFileInvalidate(dbid, tsid, true);
{
/*
* RelationCacheInitFilePreInvalidate requires DatabasePath to be set,
* but we should not use SetDatabasePath during recovery, since it is
* intended to be used only once by normal backends. Hence, a quick
* hack: set DatabasePath directly then unset after use.
*/
DatabasePath = GetDatabasePath(dbid, tsid);
elog(trace_recovery(DEBUG4), "removing relcache init file in \"%s\"",
DatabasePath);
RelationCacheInitFilePreInvalidate();
pfree(DatabasePath);
DatabasePath = NULL;
}
SendSharedInvalidMessages(msgs, nmsgs);
if (RelcacheInitFileInval)
RecoveryRelationCacheInitFileInvalidate(dbid, tsid, false);
RelationCacheInitFilePostInvalidate();
}
/*
@ -931,7 +932,7 @@ AtEOXact_Inval(bool isCommit)
* unless we committed.
*/
if (transInvalInfo->RelcacheInitFileInval)
RelationCacheInitFileInvalidate(true);
RelationCacheInitFilePreInvalidate();
AppendInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
&transInvalInfo->CurrentCmdInvalidMsgs);
@ -940,7 +941,7 @@ AtEOXact_Inval(bool isCommit)
SendSharedInvalidMessages);
if (transInvalInfo->RelcacheInitFileInval)
RelationCacheInitFileInvalidate(false);
RelationCacheInitFilePostInvalidate();
}
else if (transInvalInfo != NULL)
{