From c76734f1b8ee9b1a4496eda1f6bb3c66499f6217 Mon Sep 17 00:00:00 2001 From: Amit Kapila Date: Fri, 9 Nov 2018 09:58:27 +0530 Subject: [PATCH] Fix the initialization of atomic variable introduced by the group clearing mechanism. Commit 0e141c0fbb introduced initialization of atomic variable in InitProcess which means that it's not safe to look at it for backends that aren't currently in use. Fix that by initializing them during postmaster startup. Reported-by: Andres Freund Author: Amit Kapila Backpatch-through: 9.6 Discussion: https://postgr.es/m/20181027104138.qmbbelopvy7cw2qv@alap3.anarazel.de --- src/backend/storage/lmgr/proc.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c index bfa8499..5188264 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -266,6 +266,12 @@ InitProcGlobal(void) /* Initialize lockGroupMembers list. */ dlist_init(&procs[i].lockGroupMembers); + + /* + * Initialize the atomic variable, otherwise, it won't be safe to + * access it for backends that aren't currently in use. + */ + pg_atomic_init_u32(&(procs[i].procArrayGroupNext), INVALID_PGPROCNO); } /* @@ -399,7 +405,7 @@ InitProcess(void) /* Initialize fields for group XID clearing. */ MyProc->procArrayGroupMember = false; MyProc->procArrayGroupMemberXid = InvalidTransactionId; - pg_atomic_init_u32(&MyProc->procArrayGroupNext, INVALID_PGPROCNO); + Assert(pg_atomic_read_u32(&MyProc->procArrayGroupNext) == INVALID_PGPROCNO); /* Check that group locking fields are in a proper initial state. */ Assert(MyProc->lockGroupLeader == NULL); -- 1.8.3.1