Re: GNU/Hurd portability patches

Hello hackers,

02.07.2025 02:53, Michael Paquier wrote:
> Catching up on this thread after-the-fact, specifically looking at
> 29213636e6cd as I did the original check tweaked here for O_RDONLY.
> Agreed that a backpatch should be OK as done. The buildfarm looks OK
> currently.

Three months later we can see a number of failures produced by that
animal on several branches, e.g. [1]:
timed out after 3600 secs
---

# +++ regress install-check in src/test/modules/test_shm_mq +++
# using postmaster on /home/demo/build-farm-19.1/buildroot/tmp/buildfarm-GBEDDQ, port 5678
---- hang ----

I've spun up Debian Hurd locally, using [2], and reproduced this, just by
running: `make -s check -C src/test/modules/test_shm_mq/` in a loop.

It's not that easy to see a backtrace of the running processes on that OS,
but with some debug logging (attached), I can see that the test backend
process or shm_mq background worker just gets stuck shortly after poll().
One example:
echo "
log_min_messages = DEBUG5
log_line_prefix = '%m [%p:%l] %q%a '
log_connections = 'true'
log_disconnections = 'true'
log_statement = 'all'
autovacuum = off
" > /tmp/extra.config

for i in {1..100}; do echo "ITERATION $i"; TEMP_CONFIG=/tmp/extra.config \
timeout 60 make -s check -C src/test/modules/test_shm_mq/ || break; done; \
ps -A | grep postgres

...

ITERATION 9
ok 1         - test_shm_mq                             14498 ms

ITERATION 10
ok 1         - test_shm_mq                             34759 ms

ITERATION 11
# +++ regress check in src/test/modules/test_shm_mq +++
# initializing database system by copying initdb template
# using temp instance on port 58928 with PID 28848
make: *** [../../../../src/makefiles/pgxs.mk:451: check] Terminated
demo     28848 p0 So    0:00.03 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28849  - Ssfo  0:00.06 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28850  - Ssfo  0:00.00 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28851  - Ssfo  0:00.00 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28852  - Ssfo  0:00.00 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28853  - Ssfo  0:00.00 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28855  - Ssfo  0:00.00 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28856  - Ssfo  0:00.00 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28862  - Ssfo  0:01.13 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ
demo     28866  - Ssfo  0:00.87 postgres -D /home/demo/postgresql/src/test/modules/test_shm_mq/tmp_check/data -F -c
listen_addresses= -k /tmp/pg_regress-McfSYJ

The process 28866 is stuck, it doesn't response to SIGTERM.

src/test/modules/test_shm_mq/log/postmaster.log contains:
2025-09-21 05:48:00.749 BST [28862:23] pg_regress/test_shm_mq LOG: statement: SELECT test_shm_mq(100, (select
string_agg(chr(32+(random()*95)::int), '') from generate_series(1,(100+200*random())::int)), 10000, 1);

2025-09-21 05:48:00.750 BST [28848:59] DEBUG:  postmaster received pmsignal signal
2025-09-21 05:48:00.750 BST [28848:60] DEBUG:  registering background worker ""
2025-09-21 05:48:00.750 BST [28848:61] DEBUG:  assigned pm child slot 240 for bgworker
2025-09-21 05:48:00.750 BST [28848:62] DEBUG:  starting background worker process ""
2025-09-21 05:48:00.751 BST [28866:1] DEBUG:  find_in_path: trying
"/home/demo/postgresql/tmp_install/usr/local/pgsql/lib/test_shm_mq"
2025-09-21 05:48:00.751 BST [28866:2] DEBUG:  find_in_path: trying
"/home/demo/postgresql/tmp_install/usr/local/pgsql/lib/test_shm_mq.so"
...
!!!shm_mq_receive_bytes[28866]| before WaitLatch
!!!WaitEventSetWaitBlock POLL[28866]| rc: 1
^^^ the last message from that process ^^^

Other run:
2025-09-21 06:03:21.041 BST [29427:23] pg_regress/test_shm_mq LOG: statement: SELECT test_shm_mq(100, (select
string_agg(chr(32+(random()*95)::int), '') from generate_series(1,(100+200*random())::int)), 10000, 1);

2025-09-21 06:03:21.042 BST [29412:64] DEBUG:  postmaster received pmsignal signal
2025-09-21 06:03:21.042 BST [29412:65] DEBUG:  registering background worker ""
2025-09-21 06:03:21.042 BST [29412:66] DEBUG:  assigned pm child slot 239 for bgworker
2025-09-21 06:03:21.042 BST [29412:67] DEBUG:  starting background worker process ""
2025-09-21 06:03:21.043 BST [29431:1] DEBUG:  find_in_path: trying
"/home/demo/postgresql/tmp_install/usr/local/pgsql/lib/test_shm_mq"
2025-09-21 06:03:21.043 BST [29431:2] DEBUG:  find_in_path: trying
"/home/demo/postgresql/tmp_install/usr/local/pgsql/lib/test_shm_mq.so"

!!!WaitEventSetWaitBlock POLL[29431]| rc: 1
!!!WaitEventSetWaitBlock[29431] 1
!!!WaitEventSetWaitBlock[29431] 2
!!!WaitEventSetWaitBlock[29431] 3
!!!WaitEventSetWaitBlock[29431] 4
!!!WaitEventSetWaitBlock[29431] 5
^^^ the last message from the process 29431 ^^^

So it seems to me that Hurd is not mature enough yet to test Postgres.

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=fruitcrow&dt=2025-09-19%2007%3A29%3A06
[2] https://cdimage.debian.org/cdimage/ports/latest/hurd-amd64/debian-hurd-amd64-20250807.img.tar.xz

Best regards,
Alexander