Schedule ShutdownXLOG() in single user mode using before_shmem_exit().

Previously on_shmem_exit() was used. The upcoming shared memory stats patch
uses DSM segments to store stats, which can not be used after the
dsm_backend_shutdown() call in shmem_exit().  There does not seem to be any
reason to do ShutdownXLOG() via on_shmem_exit(), so change it.

Author: Andres Freund <[email protected]>
Discussion: https://postgr.es/m/20210405092914[email protected]
Discussion: https://postgr.es/m/20210803023612[email protected]

diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index e37b86494e181a24b8afd96fac3a488be484ed65..87dc060b201551a492a1eb0b1b184a1c460dd2b0 100644 (file)
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -638,7 +638,11 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
                /* Reset CurrentResourceOwner to nothing for the moment */
                CurrentResourceOwner = NULL;
 
-               on_shmem_exit(ShutdownXLOG, 0);
+               /*
+                * Use before_shmem_exit() so that ShutdownXLOG() can rely on DSM
+                * segments etc to work (which in turn is required for pgstats).
+                */
+               before_shmem_exit(ShutdownXLOG, 0);
        }
 
        /*