Subject: [PATCH v1 4/8] convert PROC_HDR->startupBufferPinWaitBufId to an atomic

From: Nathan Bossart <[email-masked]>
Date: Thu, 9 Jul 2026 14:26:49 -0500

---
 src/backend/storage/lmgr/proc.c | 12 +++---------
 src/include/storage/proc.h      |  2 +-
 2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 9d6e69175a5..5f314efb289 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -239,7 +239,7 @@ ProcGlobalShmemInit(void *arg)
 	dlist_init(&ProcGlobal->autovacFreeProcs);
 	dlist_init(&ProcGlobal->bgworkerFreeProcs);
 	dlist_init(&ProcGlobal->walsenderFreeProcs);
-	ProcGlobal->startupBufferPinWaitBufId = -1;
+	pg_atomic_init_u32(&ProcGlobal->startupBufferPinWaitBufId, -1);
 	pg_atomic_init_u32(&ProcGlobal->avLauncherProc, INVALID_PROC_NUMBER);
 	pg_atomic_init_u32(&ProcGlobal->walwriterProc, INVALID_PROC_NUMBER);
 	pg_atomic_init_u32(&ProcGlobal->checkpointerProc, INVALID_PROC_NUMBER);
@@ -768,10 +768,7 @@ InitAuxiliaryProcess(void)
 void
 SetStartupBufferPinWaitBufId(int bufid)
 {
-	/* use volatile pointer to prevent code rearrangement */
-	volatile PROC_HDR *procglobal = ProcGlobal;
-
-	procglobal->startupBufferPinWaitBufId = bufid;
+	pg_atomic_write_u32(&ProcGlobal->startupBufferPinWaitBufId, bufid);
 }
 
 /*
@@ -780,10 +777,7 @@ SetStartupBufferPinWaitBufId(int bufid)
 int
 GetStartupBufferPinWaitBufId(void)
 {
-	/* use volatile pointer to prevent code rearrangement */
-	volatile PROC_HDR *procglobal = ProcGlobal;
-
-	return procglobal->startupBufferPinWaitBufId;
+	return pg_atomic_read_u32(&ProcGlobal->startupBufferPinWaitBufId);
 }
 
 /*
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 03a1a466fa8..e2034255124 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -499,7 +499,7 @@ typedef struct PROC_HDR
 	/* Current shared estimate of appropriate spins_per_delay value */
 	int			spins_per_delay;
 	/* Buffer id of the buffer that Startup process waits for pin on, or -1 */
-	int			startupBufferPinWaitBufId;
+	pg_atomic_uint32 startupBufferPinWaitBufId;
 } PROC_HDR;
 
 extern PGDLLIMPORT PROC_HDR *ProcGlobal;
-- 
2.50.1 (Apple Git-155)

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