Test of a partition with an incomplete detach has a timing issue

Hi


During my review of a patch in the community,
I've encountered failures of OSS HEAD'S make check-world in a continuous loop.
I just repeated make check-world. Accordingly, this should be an existing issue.
Make check-world fails once in about 20 times in my env. I'd like to report this.

The test itself ended with stderr messages below.

NOTICE:  database "regression" does not exist, skipping
make[2]: *** [check] Error 1
make[1]: *** [check-isolation-recurse] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [check-world-src/test-recurse] Error 2

Also, I've gotten some logs left.
* src/test/isolation/output_iso/regression.out

test detach-partition-concurrently-1 ... ok          682 ms
test detach-partition-concurrently-2 ... ok          321 ms
test detach-partition-concurrently-3 ... FAILED     1084 ms
test detach-partition-concurrently-4 ... ok         1078 ms
test fk-contention                ... ok           77 ms

* src/test/isolation/output_iso/regression.diffs

diff -U3 /(where/I/put/PG)/src/test/isolation/expected/detach-partition-concurrently-3.out
/(where/I/put/PG)/src/test/isolation/output_iso/results/detach-partition-concurrently-3.out
--- /(where/I/put/PG)/src/test/isolation/expected/detach-partition-concurrently-3.out     2021-05-24 03:30:15.735488295
+0000
+++ /(where/I/put/PG)/src/test/isolation/output_iso/results/detach-partition-concurrently-3.out   2021-05-24
04:46:48.851488295+0000 
@@ -12,9 +12,9 @@
 pg_cancel_backend

 t
-step s2detach: <... completed>
-error in steps s1cancel s2detach: ERROR:  canceling statement due to user request
 step s1c: COMMIT;
+step s2detach: <... completed>
+error in steps s1c s2detach: ERROR:  canceling statement due to user request
 step s1describe: SELECT 'd3_listp' AS root, * FROM pg_partition_tree('d3_listp')
                                          UNION ALL SELECT 'd3_listp1', * FROM pg_partition_tree('d3_listp1');
 root           relid          parentrelid    isleaf         level
.

The steps I did :
1 - ./configure --enable-cassert --enable-debug --enable-tap-tests --with-icu CFLAGS=-O0 --prefix=/where/I/put/binary
2 - make -j2 2> make.log # no stderr output at this stage, of course
3 - make check-world -j8 2> make_check_world.log
    For the 1st RT, I succeeded. But, repeating the make check-world failed.


Best Regards,
    Takamichi Osumi