Subject: Missing LWLock protection in pgstat_reset_replslot()

From: Bertrand Drouvot <[email-masked]>
Date: Fri, 1 Mar 2024 10:15:48 +0000

Hi hackers,

I think that pgstat_reset_replslot() is missing LWLock protection. Indeed, we
don't have any guarantee that the slot is active (then preventing it to be
dropped/recreated) when this function is executed.

Attached a patch to add the missing protection.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
>From 26007012272631a6d1024c143c8dd3eed9430c03 Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <[email-masked]>
Date: Fri, 1 Mar 2024 10:04:17 +0000
Subject: [PATCH v1] Adding LWLock protection in pgstat_reset_replslot()

pgstat_reset_replslot() is missing a LWLock protection as we don't have any
guarantee that the slot is active (then preventing it to be dropped/recreated)
when this function is executed.
---
 src/backend/utils/activity/pgstat_replslot.c | 4 ++++
 1 file changed, 4 insertions(+)
 100.0% src/backend/utils/activity/

diff --git a/src/backend/utils/activity/pgstat_replslot.c b/src/backend/utils/activity/pgstat_replslot.c
index 70cabf2881..a113e1c486 100644
--- a/src/backend/utils/activity/pgstat_replslot.c
+++ b/src/backend/utils/activity/pgstat_replslot.c
@@ -46,6 +46,8 @@ pgstat_reset_replslot(const char *name)
 
 	Assert(name != NULL);
 
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
 	/* Check if the slot exits with the given name. */
 	slot = SearchNamedReplicationSlot(name, true);
 
@@ -65,6 +67,8 @@ pgstat_reset_replslot(const char *name)
 	/* reset this one entry */
 	pgstat_reset(PGSTAT_KIND_REPLSLOT, InvalidOid,
 				 ReplicationSlotIndex(slot));
+
+	LWLockRelease(ReplicationSlotControlLock);
 }
 
 /*
-- 
2.34.1