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Fix crash with RemoveFromWaitQueue() when detecting a deadlock.

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Commit 5764f611e used dclist_delete_from() to remove the proc from the
wait queue. However, since it doesn't clear dist_node's next/prev to
NULL, it could call RemoveFromWaitQueue() twice: when the process
detects a deadlock and then when cleaning up locks on aborting the
transaction. The waiting lock information is cleared in the first
call, so it led to a crash in the second call.

Backpatch to v16, where the change was introduced.

Bug: #18031
Reported-by: Justin Pryzby, Alexander Lakhin
Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/ZKy4AdrLEfbqrxGJ%40telsasoft.com
Discussion: https://postgr.es/m/18031-ebe2d08cb405f6cc@postgresql.org
Backpatch-through: 16
This commit is contained in:
Masahiko Sawada 2023-07-26 14:41:26 +09:00
parent d9eb92c7b1
commit bd88404d3c
1 changed files with 1 additions and 1 deletions
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2
src/backend/storage/lmgr/lock.c
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@ -1881,7 +1881,7 @@ RemoveFromWaitQueue(PGPROC *proc, uint32 hashcode)
Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
/* Remove proc from lock's wait queue */
dclist_delete_from(&waitLock->waitProcs, &proc->links);
dclist_delete_from_thoroughly(&waitLock->waitProcs, &proc->links);
/* Undo increments of request counts by waiting process */
Assert(waitLock->nRequested > 0);