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Use LW_SHARED in walsummarizer.c for WALSummarizerLock lock where possible.

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Previously, we used LW_EXCLUSIVE in several places despite only reading
WalSummarizerCtl fields. This patch reduces the lock level to LW_SHARED
where we are only reading the shared fields.

Backpatch to 17, where wal summarization was introduced.

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://postgr.es/m/CAD21AoDdKhf_9oriEYxY-JCdF+Oe_muhca3pcdkMEdBMzyHyKw@mail.gmail.com
Backpatch-through: 17
This commit is contained in:
Masahiko Sawada
2025-08-28 17:06:42 -07:00
parent b8a1bdc458
commit fabd8b8e2a
1 changed files with 2 additions and 2 deletions
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4
src/backend/postmaster/walsummarizer.c
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@@ -644,7 +644,7 @@ WakeupWalSummarizer(void)
if (WalSummarizerCtl == NULL) if (WalSummarizerCtl == NULL)
return; return;
LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE); LWLockAcquire(WALSummarizerLock, LW_SHARED);
pgprocno = WalSummarizerCtl->summarizer_pgprocno; pgprocno = WalSummarizerCtl->summarizer_pgprocno;
LWLockRelease(WALSummarizerLock); LWLockRelease(WALSummarizerLock);
@@ -685,7 +685,7 @@ WaitForWalSummarization(XLogRecPtr lsn)
/* /*
* If the LSN summarized on disk has reached the target value, stop. * If the LSN summarized on disk has reached the target value, stop.
*/ */
LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE); LWLockAcquire(WALSummarizerLock, LW_SHARED);
summarized_lsn = WalSummarizerCtl->summarized_lsn; summarized_lsn = WalSummarizerCtl->summarized_lsn;
pending_lsn = WalSummarizerCtl->pending_lsn; pending_lsn = WalSummarizerCtl->pending_lsn;
LWLockRelease(WALSummarizerLock); LWLockRelease(WALSummarizerLock);