Re: lockup in parallel hash join on dikkop (freebsd 14.0-current)

On 1/28/23 13:05, Tomas Vondra wrote:
>
> FWIW I'll wait for dikkop to finish the current buildfarm run (it's
> currently chewing on HEAD) and then will try to do runs of the 'joins'
> test in a loop. That's where dikkop got stuck before.
>

So I did that - same configure options as the buildfarm client, and a
'make check' (with only tests up to the 'join' suite, because that's
where it got stuck before). And it took only ~15 runs (~1h) to hit this
again on dikkop.

As before, there are three processes - leader + 2 workers, but the query
is different - this time it's this one:

-- A couple of other hash join tests unrelated to work_mem management.
-- Check that EXPLAIN ANALYZE has data even if the leader doesn't
participate
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
set local parallel_leader_participation = off;
select * from hash_join_batches(
$$
select count(*) from simple r join simple s using (id);
$$);

I managed to collect the fstat/procstat stuff Thomas asked for, and the
backtraces - attached. I still have the core files, in case we look at
something. As before, running gcore on the second worker (29081) gets
this unstuck - it sends some signal that apparently wakes it up.

regards

--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company