From d4d9f21b64d4290cc6695bcd93a8e4c5fc16badf Mon Sep 17 00:00:00 2001 From: Amit Kapila Date: Tue, 13 Nov 2018 11:09:44 +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 6f9aaa52fa..6ad504453b 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