postgres.git / summary / log / commit / refs

commit    dba6e75c1113dbfc7b10d93cc6c0babd8b7d852b
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Tue Nov 28 17:05:52 2017 +0000
First released in: 11.0, 10.2

    Fix ReinitializeParallelDSM to tolerate finding no error queues.
    
    Commit d4663350646ca0c069a36d906155a0f7e3372eb7 changed things so
    that shm_toc_lookup would fail with an error rather than silently
    returning NULL in the hope that such failures would be reported
    in a useful way rather than via a system crash.  However, it
    overlooked the fact that the lookup of PARALLEL_KEY_ERROR_QUEUE
    in ReinitializeParallelDSM is expected to fail when no DSM segment
    was created in the first place; in that case, we end up with a
    backend-private memory segment that still contains an entry for
    PARALLEL_KEY_FIXED but no others.  Consequently a benign failure
    to initialize parallelism can escalate into an elog(ERROR);
    repair.
    
    Discussion: http://postgr.es/m/CA+Tgmob8LFw55DzH1QEREpBEA9RJ_W_amhBFCVZ6WMwUhVpOqg@mail.gmail.com


 src/backend/access/transam/parallel.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index e1a6a75a872..afef608d70f 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -399,9 +399,10 @@ ReinitializeParallelDSM(ParallelContext *pcxt)
 	fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
 	fps->last_xlog_end = 0;
 
-	/* Recreate error queues. */
+	/* Recreate error queues (if they exist). */
 	error_queue_space =
-		shm_toc_lookup(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, false);
+		shm_toc_lookup(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, true);
+	Assert(pcxt->nworkers == 0 || error_queue_space != NULL);
 	for (i = 0; i < pcxt->nworkers; ++i)
 	{
 		char	   *start;


[parent: ec7629dfb98a]