postgres.git / summary / log / commit / refs

commit    514688656b8bca623bd2d1a28a549f8a56751612
Author:   Masahiko Sawada <msawada@postgresql.org>
Date:     Fri Aug 29 00:06:44 2025 +0000
First released in: 17.7, 18.0

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


 src/backend/postmaster/walsummarizer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index 0fec4f1f871..11857356ce4 100644
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -644,7 +644,7 @@ WakeupWalSummarizer(void)
 	if (WalSummarizerCtl == NULL)
 		return;
 
-	LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
+	LWLockAcquire(WALSummarizerLock, LW_SHARED);
 	pgprocno = WalSummarizerCtl->summarizer_pgprocno;
 	LWLockRelease(WALSummarizerLock);
 
@@ -685,7 +685,7 @@ WaitForWalSummarization(XLogRecPtr lsn)
 		/*
 		 * 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;
 		pending_lsn = WalSummarizerCtl->pending_lsn;
 		LWLockRelease(WALSummarizerLock);


[parent: 3aee6283709f]