From afec6ba0bae0258835b81fcc0eeed3ff9c455427 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 4 Sep 2020 12:40:28 -0400 Subject: [PATCH] Fix rare deadlock failure in create_am regression test. The "DROP ACCESS METHOD gist2" test will require locking the index to be dropped and then its table; while most ordinary operations lock a table first then its index. While no concurrent test scripts should be touching fast_emp4000, autovacuum might chance to be processing that table when the DROP runs, resulting in a deadlock failure. This is pretty rare but we see it in the buildfarm from time to time. To fix, acquire a lock on fast_emp4000 before issuing the DROP. Since the point of the exercise is mostly to prevent buildfarm failures, back-patch to 9.6 where this test was introduced. Discussion: https://postgr.es/m/839004.1599185607@sss.pgh.pa.us --- src/test/regress/expected/create_am.out | 5 +++++ src/test/regress/sql/create_am.sql | 5 +++++ 2 files changed, 10 insertions(+) diff --git a/src/test/regress/expected/create_am.out b/src/test/regress/expected/create_am.out index 84da403afc..b9dc82dd3c 100644 --- a/src/test/regress/expected/create_am.out +++ b/src/test/regress/expected/create_am.out @@ -102,8 +102,13 @@ ERROR: cannot drop access method gist2 because other objects depend on it DETAIL: index grect2ind2 depends on operator class box_ops for access method gist2 HINT: Use DROP ... CASCADE to drop the dependent objects too. -- Drop access method cascade +-- To prevent a (rare) deadlock against autovacuum, +-- we must lock the table that owns the index that will be dropped +BEGIN; +LOCK TABLE fast_emp4000; DROP ACCESS METHOD gist2 CASCADE; NOTICE: drop cascades to index grect2ind2 +COMMIT; -- -- Test table access methods -- diff --git a/src/test/regress/sql/create_am.sql b/src/test/regress/sql/create_am.sql index a7f6de7e9b..97df244d17 100644 --- a/src/test/regress/sql/create_am.sql +++ b/src/test/regress/sql/create_am.sql @@ -70,7 +70,12 @@ ROLLBACK; DROP ACCESS METHOD gist2; -- Drop access method cascade +-- To prevent a (rare) deadlock against autovacuum, +-- we must lock the table that owns the index that will be dropped +BEGIN; +LOCK TABLE fast_emp4000; DROP ACCESS METHOD gist2 CASCADE; +COMMIT; --