Fix oversight from 9e149c8 with spin-lock handling

michaelpq · michaelpq · commit f8795d2ec863 · 2018-06-12T06:52:34.000+09:00
Calling an external function while a pin-lock is held is a bad idea as those are designed to be short-lived. The stress of a first commit into a large git history may contribute to that. Reported-by: Andres Freund Discussion: https://postgr.es/m/20180611164952.vmxdpdpirdtkdsz6@alap3.anarazel.de
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
@@ -999,6 +999,7 @@ ReplicationSlotReserveWal(void)
 	while (true)
 	{
 		XLogSegNo	segno;
+		XLogRecPtr	restart_lsn;
 
 		/*
 		 * For logical slots log a standby snapshot and start logical decoding
@@ -1016,8 +1017,9 @@ ReplicationSlotReserveWal(void)
 			XLogRecPtr	flushptr;
 
 			/* start at current insert position */
+			restart_lsn = GetXLogInsertRecPtr();
 			SpinLockAcquire(&slot->mutex);
-			slot->data.restart_lsn = GetXLogInsertRecPtr();
+			slot->data.restart_lsn = restart_lsn;
 			SpinLockRelease(&slot->mutex);
 
 			/* make sure we have enough information to start */
@@ -1028,8 +1030,9 @@ ReplicationSlotReserveWal(void)
 		}
 		else
 		{
+			restart_lsn = GetRedoRecPtr();
 			SpinLockAcquire(&slot->mutex);
-			slot->data.restart_lsn = GetRedoRecPtr();
+			slot->data.restart_lsn = restart_lsn;
 			SpinLockRelease(&slot->mutex);
 		}
 

Original file line number	Diff line number	Diff line change
`@@ -999,6 +999,7 @@ ReplicationSlotReserveWal(void)`
`999`	`999`	`while (true)`
`1000`	`1000`	`{`
`1001`	`1001`	`XLogSegNo segno;`
	`1002`	`+ XLogRecPtr restart_lsn;`
`1002`	`1003`
`1003`	`1004`	`/*`
`1004`	`1005`	`* For logical slots log a standby snapshot and start logical decoding`
`@@ -1016,8 +1017,9 @@ ReplicationSlotReserveWal(void)`
`1016`	`1017`	`XLogRecPtr flushptr;`
`1017`	`1018`
`1018`	`1019`	`/* start at current insert position */`
	`1020`	`+ restart_lsn = GetXLogInsertRecPtr();`
`1019`	`1021`	`SpinLockAcquire(&slot->mutex);`
`1020`		`- slot->data.restart_lsn = GetXLogInsertRecPtr();`
	`1022`	`+ slot->data.restart_lsn = restart_lsn;`
`1021`	`1023`	`SpinLockRelease(&slot->mutex);`
`1022`	`1024`
`1023`	`1025`	`/* make sure we have enough information to start */`
`@@ -1028,8 +1030,9 @@ ReplicationSlotReserveWal(void)`
`1028`	`1030`	`}`
`1029`	`1031`	`else`
`1030`	`1032`	`{`
	`1033`	`+ restart_lsn = GetRedoRecPtr();`
`1031`	`1034`	`SpinLockAcquire(&slot->mutex);`
`1032`		`- slot->data.restart_lsn = GetRedoRecPtr();`
	`1035`	`+ slot->data.restart_lsn = restart_lsn;`
`1033`	`1036`	`SpinLockRelease(&slot->mutex);`
`1034`	`1037`	`}`
`1035`	`1038`