postgres.git / summary / log / commit / refs

commit    ede6acef49673df0a880edae405ca69393bb48d0
Author:   Alexander Korotkov <akorotkov@postgresql.org>
Date:     Sat Nov 15 10:16:23 2025 +0000

    Fix WaitLSNWakeup() fast-path check for InvalidXLogRecPtr
    
    WaitLSNWakeup() incorrectly returned early when called with
    InvalidXLogRecPtr (meaning "wake all waiters"), because the fast-path
    check compared minWaitedLSN > 0 without validating currentLSN first.
    This caused WAIT FOR LSN commands to wait indefinitely during standby
    promotion until random signals woke them.
    
    Add an XLogRecPtrIsValid() check before the comparison so that
    InvalidXLogRecPtr bypasses the fast-path and wakes all waiters immediately.
    
    Discussion: https://postgr.es/m/CABPTF7UieOYbOgH3EnQCasaqcT1T4N6V2wammwrWCohQTnD_Lw%40mail.gmail.com
    Author: Xuneng Zhou <xunengzhou@gmail.com>
    Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>


 src/backend/access/transam/xlogwait.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/xlogwait.c b/src/backend/access/transam/xlogwait.c
index 34fa41ed9b2..78de93db47f 100644
--- a/src/backend/access/transam/xlogwait.c
+++ b/src/backend/access/transam/xlogwait.c
@@ -270,8 +270,12 @@ WaitLSNWakeup(WaitLSNType lsnType, XLogRecPtr currentLSN)
 
 	Assert(i >= 0 && i < (int) WAIT_LSN_TYPE_COUNT);
 
-	/* Fast path check */
-	if (pg_atomic_read_u64(&waitLSNState->minWaitedLSN[i]) > currentLSN)
+	/*
+	 * Fast path check.  Skip if currentLSN is InvalidXLogRecPtr, which means
+	 * "wake all waiters" (e.g., during promotion when recovery ends).
+	 */
+	if (XLogRecPtrIsValid(currentLSN) &&
+		pg_atomic_read_u64(&waitLSNState->minWaitedLSN[i]) > currentLSN)
 		return;
 
 	wakeupWaiters(lsnType, currentLSN);


[parent: 446568c22207]