From: Thomas Munro <tmunro@postgresql.org>
Date: Mon, 30 May 2022 23:38:19 +0000 (+1200)
Subject: Add debugging help in OwnLatch().
X-Git-Tag: REL_15_BETA2~84
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=12e28aac8e8eb76cab13a4e9b696e3dab17f1c99;p=thirdparty%2Fpostgresql.git

Add debugging help in OwnLatch().

Build farm animal gharial recently failed a few times in a parallel
worker's call to OwnLatch() with "ERROR:  latch already owned".  Let's
turn that into a PANIC and show the PID of the owner, to try to learn
more.

Discussion: https://postgr.es/m/CA%2BhUKGJ_0RGcr7oUNzcHdn7zHqHSB_wLSd3JyS2YC_DYB%2B-V%3Dg%40mail.gmail.com
---

diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index 78c6a892713..41d359d68ed 100644
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -402,6 +402,8 @@ InitSharedLatch(Latch *latch)
 void
 OwnLatch(Latch *latch)
 {
+	int			owner_pid;
+
 	/* Sanity checks */
 	Assert(latch->is_shared);
 
@@ -410,8 +412,9 @@ OwnLatch(Latch *latch)
 	Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
 #endif
 
-	if (latch->owner_pid != 0)
-		elog(ERROR, "latch already owned");
+	owner_pid = latch->owner_pid;
+	if (owner_pid != 0)
+		elog(PANIC, "latch already owned by PID %d", owner_pid);
 
 	latch->owner_pid = MyProcPid;
 }