From 8686ae4d71a9d3aab9acc7aa515880e9aa1b75b1 Mon Sep 17 00:00:00 2001 From: Amit Kapila Date: Fri, 9 Nov 2018 09:30:59 +0530 Subject: [PATCH] Fix the initialization of atomic variables introduced by the group clearing mechanism. Commits 0e141c0fbb and baaf272ac9 introduced initialization of atomic variables in InitProcess which means that it's not safe to look at those 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 | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c index 6f9aaa5..6ad5044 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -267,6 +267,13 @@ InitProcGlobal(void) /* Initialize lockGroupMembers list. */ dlist_init(&procs[i].lockGroupMembers); + + /* + * Initialize the atomic variables, otherwise, it won't be safe to + * access them for backends that aren't currently in use. + */ + pg_atomic_init_u32(&(procs[i].procArrayGroupNext), INVALID_PGPROCNO); + pg_atomic_init_u32(&(procs[i].clogGroupNext), INVALID_PGPROCNO); } /* @@ -401,7 +408,7 @@ 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); @@ -416,7 +423,7 @@ InitProcess(void) MyProc->clogGroupMemberXidStatus = TRANSACTION_STATUS_IN_PROGRESS; MyProc->clogGroupMemberPage = -1; MyProc->clogGroupMemberLsn = InvalidXLogRecPtr; - pg_atomic_init_u32(&MyProc->clogGroupNext, INVALID_PGPROCNO); + Assert(pg_atomic_read_u32(&MyProc->clogGroupNext) == INVALID_PGPROCNO); /* * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch -- 1.8.3.1