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pgsql: bufmgr: Fix order of operations in UnlockBufHdrExt 2+ messages / 1 participants [nested] [flat]
* pgsql: bufmgr: Fix order of operations in UnlockBufHdrExt @ 2026-07-10 17:27 Andres Freund <andres@anarazel.de> 0 siblings, 0 replies; 2+ messages in thread From: Andres Freund @ 2026-07-10 17:27 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org bufmgr: Fix order of operations in UnlockBufHdrExt In c75ebc657ffc I (Andres) introduced UnlockBufHdrExt() which can set and clear bits in the buffer state using CAS. Unfortunately I added bits before subtracting them, which means that a bit that was both removed and set would remain unset. Fix the order of operations. The only known case where that is a problem is that BM_IO_ERROR would not actually remain set. It's unfortunately not trivial to add a decent, race-free, test to verify that BM_IO_ERROR remains set. That's therefore left for the 20 cycle. Reported-by: Yura Sokolov <y.sokolov@postgrespro.ru> Discussion: https://postgr.es/m/ab0dcc9e-aba0-44e3-ac23-8d74c48888e6@postgrespro.ru Backpatch-through: 19, where c75ebc657ffc went in Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/c787c952bc882626c66ec64b1d35a664902bfa8b Modified Files -------------- src/include/storage/buf_internals.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
* pgsql: bufmgr: Fix order of operations in UnlockBufHdrExt @ 2026-07-10 17:27 Andres Freund <andres@anarazel.de> 0 siblings, 0 replies; 2+ messages in thread From: Andres Freund @ 2026-07-10 17:27 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org bufmgr: Fix order of operations in UnlockBufHdrExt In c75ebc657ffc I (Andres) introduced UnlockBufHdrExt() which can set and clear bits in the buffer state using CAS. Unfortunately I added bits before subtracting them, which means that a bit that was both removed and set would remain unset. Fix the order of operations. The only known case where that is a problem is that BM_IO_ERROR would not actually remain set. It's unfortunately not trivial to add a decent, race-free, test to verify that BM_IO_ERROR remains set. That's therefore left for the 20 cycle. Reported-by: Yura Sokolov <y.sokolov@postgrespro.ru> Discussion: https://postgr.es/m/ab0dcc9e-aba0-44e3-ac23-8d74c48888e6@postgrespro.ru Backpatch-through: 19, where c75ebc657ffc went in Branch ------ REL_19_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/a1b74b7279c24638c44f9d3d1af2da30cfb7068d Modified Files -------------- src/include/storage/buf_internals.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2026-07-10 17:27 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2026-07-10 17:27 pgsql: bufmgr: Fix order of operations in UnlockBufHdrExt Andres Freund <andres@anarazel.de> 2026-07-10 17:27 pgsql: bufmgr: Fix order of operations in UnlockBufHdrExt Andres Freund <andres@anarazel.de>
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