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Check RecoveryInProgress() while holding ProcArrayLock during snapshots.

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This prevents a rare, yet possible race condition at the exact moment
of transition from recovery to normal running.
This commit is contained in:
Simon Riggs 2010-04-19 18:03:38 +00:00
parent 39bf46384b
commit 7bc76d51fb
1 changed files with 9 additions and 4 deletions
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13
src/backend/storage/ipc/procarray.c
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@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.63 2010/04/18 18:05:55 sriggs Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.64 2010/04/19 18:03:38 sriggs Exp $
*
*-------------------------------------------------------------------------
*/
@ -1074,8 +1074,6 @@ GetSnapshotData(Snapshot snapshot)
errmsg("out of memory")));
}
snapshot->takenDuringRecovery = RecoveryInProgress();
/*
* It is sufficient to get shared lock on ProcArrayLock, even if we are
* going to set MyProc->xmin.
@ -1091,8 +1089,15 @@ GetSnapshotData(Snapshot snapshot)
globalxmin = xmin = xmax;
/*
* If in recovery get any known assigned xids.
* If we're in recovery then snapshot data comes from a different place,
* so decide which route we take before grab the lock. It is possible
* for recovery to end before we finish taking snapshot, and for newly
* assigned transaction ids to be added to the procarray. Xmax cannot
* change while we hold ProcArrayLock, so those newly added transaction
* ids would be filtered away, so we need not be concerned about them.
*/
snapshot->takenDuringRecovery = RecoveryInProgress();
if (!snapshot->takenDuringRecovery)
{
/*