]> git.ipfire.org Git - thirdparty/postgresql.git/commit
Fix remaining race condition with CLOG truncation and LISTEN/NOTIFY
authorHeikki Linnakangas <heikki.linnakangas@iki.fi>
Wed, 12 Nov 2025 18:59:44 +0000 (20:59 +0200)
committerHeikki Linnakangas <heikki.linnakangas@iki.fi>
Wed, 12 Nov 2025 19:02:14 +0000 (21:02 +0200)
commit0c862646cf2aeba130222ec587702c331fbf3783
tree3e0fb335a06cc58336d08f27b9f9830f1592b501
parent1a469d7b5b7dac2dfa63835bb8313a6d0f267927
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
src/backend/commands/async.c