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commit    b4f14d2e433bf9f2499f07bcaca07b9ff13d641b
Author:   Masahiko Sawada <msawada@postgresql.org>
Date:     Wed Jul 26 05:41:23 2023 +0000
First released in: 17.0, 16.0

    Fix crash with RemoveFromWaitQueue() when detecting a deadlock.
    
    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


 src/backend/storage/lmgr/lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index f595bce31b9..ec6240fbaee 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/src/backend/storage/lmgr/lock.c
@@ -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);


[parent: 35c85c3c9b90]