From 1a8bde490c982cbdd9d174e72d42f6042e9bf4ee Mon Sep 17 00:00:00 2001 From: Amit Kapila Date: Tue, 13 Nov 2018 10:43:35 +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 the same 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 cb6e1e3e5b..3f80c82288 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -268,6 +268,12 @@ 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); } /* @@ -401,7 +407,7 @@ 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);