]> 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 19:01:45 +0000 (21:01 +0200)
commit44e8c60be66c7c174431c4cd7948c1ff015fe516
tree7de1cdbaddb88f8eef1c373b7568a293ba869b5d
parent053e1868b7ee1eacc5c09b11f5a18cab57285a50
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