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Fix oversight in coding of _bt_start_vacuum: we can't assume that the LWLock 

will be released by transaction abort before _bt_end_vacuum gets called.
If either of these "can't happen" errors actually happened, we'd freeze up
trying to acquire an already-held lock.  Latest word is that this does
not explain Martin Pitt's trouble report, but it still looks like a bug.
This commit is contained in:
Tom Lane 2007-03-30 00:12:59 +00:00
parent 452427d0fd
commit 8875d0987d
1 changed files with 13 additions and 1 deletions
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14
src/backend/access/nbtree/nbtutils.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.82 2007/01/09 02:14:10 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.83 2007/03/30 00:12:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1214,13 +1214,25 @@ _bt_start_vacuum(Relation rel)
vac = &btvacinfo->vacuums[i];
if (vac->relid.relId == rel->rd_lockInfo.lockRelId.relId &&
vac->relid.dbId == rel->rd_lockInfo.lockRelId.dbId)
{
/*
* Unlike most places in the backend, we have to explicitly
* release our LWLock before throwing an error. This is because
* we expect _bt_end_vacuum() to be called before transaction
* abort cleanup can run to release LWLocks.
*/
LWLockRelease(BtreeVacuumLock);
elog(ERROR, "multiple active vacuums for index \"%s\"",
RelationGetRelationName(rel));
}
}
/* OK, add an entry */
if (btvacinfo->num_vacuums >= btvacinfo->max_vacuums)
{
LWLockRelease(BtreeVacuumLock);
elog(ERROR, "out of btvacinfo slots");
}
vac = &btvacinfo->vacuums[btvacinfo->num_vacuums];
vac->relid = rel->rd_lockInfo.lockRelId;
vac->cycleid = result;