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Be more wary about partially-valid LOCALLOCK data in RemoveLocalLock().

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RemoveLocalLock() must consider the possibility that LockAcquireExtended()
failed to palloc the initial space for a locallock's lockOwners array.
I had evidently meant to cope with this hazard when the code was originally
written (commit 1785acebf2ed14fd66955e2d9a55d77a025f418d), but missed that
the pfree needed to be protected with an if-test.  Just to make sure things
are left in a clean state, reset numLockOwners as well.

Per low-memory testing by Andreas Seltenreich.  Back-patch to all supported
branches.
This commit is contained in:
Tom Lane 2015-09-20 16:48:44 -04:00
parent 85eda7e92c
commit ba51774d87
1 changed files with 4 additions and 2 deletions
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6
src/backend/storage/lmgr/lock.c
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@ -753,7 +753,7 @@ LockAcquireExtended(const LOCKTAG *locktag,
locallock->numLockOwners = 0;
locallock->maxLockOwners = 8;
locallock->holdsStrongLockCount = FALSE;
locallock->lockOwners = NULL;
locallock->lockOwners = NULL; /* in case next line fails */
locallock->lockOwners = (LOCALLOCKOWNER *)
MemoryContextAlloc(TopMemoryContext,
locallock->maxLockOwners * sizeof(LOCALLOCKOWNER));
@ -1222,7 +1222,9 @@ RemoveLocalLock(LOCALLOCK *locallock)
if (locallock->lockOwners[i].owner != NULL)
ResourceOwnerForgetLock(locallock->lockOwners[i].owner, locallock);
}
pfree(locallock->lockOwners);
locallock->numLockOwners = 0;
if (locallock->lockOwners != NULL)
pfree(locallock->lockOwners);
locallock->lockOwners = NULL;
if (locallock->holdsStrongLockCount)