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

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 originallywritten (commit1785ace), but missed thatthe pfree needed to be protected with an if-test. Just to make sure thingsare left in a clean state, reset numLockOwners as well.Per low-memory testing by Andreas Seltenreich. Back-patch to all supportedbranches.

1 parent44297a0 commiteed5bbcCopy full SHA for eed5bbc

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src/backend/storage/lmgr
- lock.c

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`‎src/backend/storage/lmgr/lock.c`

Lines changed: 5 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -644,7 +644,7 @@ LockAcquireExtended(const LOCKTAG *locktag,`
`644`	`644`	`locallock->nLocks=0;`
`645`	`645`	`locallock->numLockOwners=0;`
`646`	`646`	`locallock->maxLockOwners=8;`
`647`		`-locallock->lockOwners=NULL;`
	`647`	`+locallock->lockOwners=NULL;/* in case next line fails */`
`648`	`648`	`locallock->lockOwners= (LOCALLOCKOWNER*)`
`649`	`649`	`MemoryContextAlloc(TopMemoryContext,`
`650`	`650`	`locallock->maxLockOwners*sizeof(LOCALLOCKOWNER));`
`@@ -994,8 +994,11 @@ LockAcquireExtended(const LOCKTAG *locktag,`
`994`	`994`	`staticvoid`
`995`	`995`	`RemoveLocalLock(LOCALLOCK*locallock)`
`996`	`996`	`{`
`997`		`-pfree(locallock->lockOwners);`
	`997`	`+locallock->numLockOwners=0;`
	`998`	`+if (locallock->lockOwners!=NULL)`
	`999`	`+pfree(locallock->lockOwners);`
`998`	`1000`	`locallock->lockOwners=NULL;`
	`1001`	`+`
`999`	`1002`	`if (!hash_search(LockMethodLocalHash,`
`1000`	`1003`	`(void*)&(locallock->tag),`
`1001`	`1004`	`HASH_REMOVE,NULL))`

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Commiteed5bbc

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`‎src/backend/storage/lmgr/lock.c`

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