From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix remaining race condition with CLOG truncation and LISTEN/NOT
Date: Wed, 12 Nov 2025 19:16:38 +0000
Message-ID: <E1vJGKc-006HeU-2J@gemulon.postgresql.org> (raw)
Fix remaining race condition with CLOG truncation and LISTEN/NOTIFY
Previous commit fixed a bug where VACUUM would truncate the CLOG
that's still needed to check the commit status of XIDs in the async
notify queue, but as mentioned in the commit message, it wasn't a full
fix. If a backend is executing asyncQueueReadAllNotifications() and
has just made a local copy of an async SLRU page which contains old
XIDs, vacuum can concurrently truncate the CLOG covering those XIDs,
and the backend still gets an error when it calls
TransactionIdDidCommit() on those XIDs in the local copy. This commit
fixes that race condition.
To fix, hold the SLRU bank lock across the TransactionIdDidCommit()
calls in NOTIFY processing.
Per Tom Lane's idea. Backpatch to all supported versions.
Reviewed-by: Joel Jacobson <joel@compiler.org>
Reviewed-by: Arseniy Mukhin <arseniy.mukhin.dev@gmail.com>
Discussion: https://www.postgresql.org/message-id/2759499.1761756503@sss.pgh.pa.us
Backpatch-through: 14
Branch
------
REL_17_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/c2682810ab7d7127b99b4ce0db73d5db28a67c3f
Modified Files
--------------
src/backend/commands/async.c | 123 ++++++++++++++++++++++---------------------
1 file changed, 62 insertions(+), 61 deletions(-)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-committers@postgresql.org
Cc: heikki.linnakangas@iki.fi, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix remaining race condition with CLOG truncation and LISTEN/NOT
In-Reply-To: <E1vJGKc-006HeU-2J@gemulon.postgresql.org>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox