Make XactLockTableWait() and ConditionalXactLockTableWait() interruptable more.

MasaoFujii · MasaoFujii · commit 24c5ad5be46d · 2025-05-31T00:14:07.000+09:00
Previously, XactLockTableWait() and ConditionalXactLockTableWait() could enter a non-interruptible loop when they successfully acquired a lock on a transaction but the transaction still appeared to be running. Since this loop continued until the transaction completed, it could result in long, uninterruptible waits. Although this scenario is generally unlikely since XactLockTableWait() and ConditionalXactLockTableWait() can basically acquire a transaction lock only when the transaction is not running, it can occur in a hot standby. In such cases, the transaction may still appear active due to the KnownAssignedXids list, even while no lock on the transaction exists. For example, this situation can happen when creating a logical replication slot on a standby. The cause of the non-interruptible loop was the absence of CHECK_FOR_INTERRUPTS() within it. This commit adds CHECK_FOR_INTERRUPTS() to the loop in both functions, ensuring they can be interrupted safely. Back-patch to all supported branches. Author: Kevin K Biju <kevinkbiju@gmail.com> Reviewed-by: Fujii Masao <masao.fujii@gmail.com> Discussion: https://postgr.es/m/CAM45KeELdjhS-rGuvN=ZLJ_asvZACucZ9LZWVzH7bGcD12DDwg@mail.gmail.com Backpatch-through: 13
diff --git a/src/backend/storage/lmgr/lmgr.c b/src/backend/storage/lmgr/lmgr.c
@@ -711,7 +711,10 @@ XactLockTableWait(TransactionId xid, Relation rel, ItemPointer ctid,
 		 * through, to avoid slowing down the normal case.)
 		 */
 		if (!first)
+		{
+			CHECK_FOR_INTERRUPTS();
 			pg_usleep(1000L);
+		}
 		first = false;
 		xid = SubTransGetTopmostTransaction(xid);
 	}
@@ -749,7 +752,10 @@ ConditionalXactLockTableWait(TransactionId xid)
 
 		/* See XactLockTableWait about this case */
 		if (!first)
+		{
+			CHECK_FOR_INTERRUPTS();
 			pg_usleep(1000L);
+		}
 		first = false;
 		xid = SubTransGetTopmostTransaction(xid);
 	}
