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