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help / color / mirror / Atom feedFrom: Alexander Korotkov <akorotkov@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Wake primary_flush waiters after implicit WAL flushes
Date: Sat, 12 Sep 2026 20:30:45 +0000
Message-ID: <E1x5UN3-000000003qq-02gk@gemulon.postgresql.org> (raw)
Wake primary_flush waiters after implicit WAL flushes
XLogWrite() can advance the flush position when it finishes a WAL
segment, even if its caller requested only a write. When this happens
while AdvanceXLInsertBuffer() recycles a buffer, primary_flush waiters
are not notified and can sleep until an unrelated flush or checkpoint.
Track such progress with a process-local pending flag and perform the
wakeup after releasing WAL write and insertion locks, keeping
WaitLSNLock acquisition outside the contended WAL path. Add a
deterministic injection-point test that forces this path and inspects
the registration directly in shared memory.
Author: Xuneng Zhou <xunengzhou@gmail.com>
Discussion: https://postgr.es/m/CABPTF7U0gW5%2B-4oL7-qdML-yerZxUb7ku4QXp7JxCYo0qyJ_Tw%40mail.gmail.com
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Backpatch-through: 19
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/d61f9c90f2ef96b38eceb592b63c688d74cf7611
Modified Files
--------------
src/backend/access/transam/xlog.c | 34 ++++++++
src/backend/access/transam/xlogwait.c | 3 +
src/backend/postmaster/walwriter.c | 3 +
src/test/recovery/t/049_wait_for_lsn.pl | 146 ++++++++++++++++++++++++++++++++
4 files changed, 186 insertions(+)
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To: pgsql-committers@postgresql.org
Cc: akorotkov@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Wake primary_flush waiters after implicit WAL flushes
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