postgres.git / summary / log / commit / refs

commit    4e277b424a5312cdee468d92078a5359f3e7d4e7
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Thu Sep 24 15:20:32 2026 +0000

    Fix ShmemInitStruct() reattachment in single-user mode
    
    ShmemInitStruct() only looked for an existing allocation when
    IsUnderPostmaster was true.  Because of that, you could not reattach
    to an existing shmem area in a standalone backend.
    
    Usually, you only call ShmemInitStruct() for the same shmem area once
    in a process and hold onto the returned pointer, but there was no rule
    that you couldn't call it twice for the same area if you wanted to,
    and before commit 283e823f9d, it worked.  To fix, check for an
    existing allocation regardless of process type, like the old
    implementation did.
    
    Author: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
    Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
    Discusssion: https://www.postgresql.org/message-id/CAJTYsWXREGXCnWdZJsXt8pT2UY_Y2GSx+HOUu2X3s8YDCLj0_A@mail.gmail.com
    Backpatch-through: 19


 src/backend/storage/ipc/shmem.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index 6037f469acd..0e827344462 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -1131,12 +1131,8 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 
 	LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE);
 
-	/*
-	 * During postmaster startup, look up the existing entry if any.
-	 */
-	*foundPtr = false;
-	if (IsUnderPostmaster)
-		*foundPtr = AttachShmemIndexEntry(&request, true);
+	/* Look up the existing entry if any */
+	*foundPtr = AttachShmemIndexEntry(&request, true);
 
 	/* Initialize it if not found */
 	if (!*foundPtr)