From 4fd05bb55b40a3c9dde2b19942f275fc31b5225a Mon Sep 17 00:00:00 2001 From: Thomas Munro <tmunro@postgresql.org> Date: Tue, 2 Apr 2019 09:08:15 +1300 Subject: [PATCH] Fix deadlock in heap_compute_xid_horizon_for_tuples(). We can't call code that uses syscache while we hold buffer locks on a catalog relation. If passed such a relation, just fall back to the general effective_io_concurrency GUC rather than trying to look up the containing tablespace's IO concurrency setting. We might find a better way to control prefetching in follow-up work, but for now this is enough to avoid the deadlock introduced by commit 558a9165e0. Reviewed-by: Andres Freund Diagnosed-by: Peter Geoghegan Discussion: https://postgr.es/m/CA%2BhUKGLCwPF0S4Mk7S8qw%2BDK0Bq65LueN9rofAA3HHSYikW-Zw%40mail.gmail.com Discussion: https://postgr.es/m/962831d8-c18d-180d-75fb-8b842e3a2742%40chrullrich.net --- src/backend/access/heap/heapam.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index de5bb9194e..05ceb6550d 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -6976,8 +6976,15 @@ heap_compute_xid_horizon_for_tuples(Relation rel, * more prefetching in this case, too. It may be that this formula is too * simplistic, but at the moment there is no evidence of that or any idea * about what would work better. + * + * Since the caller holds a buffer lock somewhere in rel, we'd better make + * sure that isn't a catalog relation before we call code that does + * syscache lookups, to avoid risk of deadlock. */ - io_concurrency = get_tablespace_io_concurrency(rel->rd_rel->reltablespace); + if (IsCatalogRelation(rel)) + io_concurrency = effective_io_concurrency; + else + io_concurrency = get_tablespace_io_concurrency(rel->rd_rel->reltablespace); prefetch_distance = Min((io_concurrency) + 10, MAX_IO_CONCURRENCY); /* Start prefetching. */ -- 2.40.0