sleep-to-expose-shmat-race-condition.patch

diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c
index a9d7bf9..d390ba4 100644
--- a/src/backend/port/sysv_shmem.c
+++ b/src/backend/port/sysv_shmem.c
@@ -387,6 +387,8 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
 	if (stat(DataDir, &statbuf) < 0)
 		return SHMSTATE_ANALYSIS_FAILURE;	/* can't stat; be conservative */
 
+	pg_usleep(100000);
+
 	/*
 	 * Attachment fails if we have no write permission.  Since that will never
 	 * happen with Postgres IPCProtection, such a failure shows the segment is
@@ -398,8 +400,9 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
 	{
 		if (errno == EACCES)
 			return SHMSTATE_FOREIGN;
-		else
-			return SHMSTATE_ANALYSIS_FAILURE;
+		elog(LOG, "shmat(0x%lx) failed: %m, nattch had been %ld",
+			 (long) shmId, (long) shmStat.shm_nattch);
+		return SHMSTATE_ANALYSIS_FAILURE;
 	}
 	*addr = hdr;