Re: Query on pg_stat_activity table got stuck

neeraj kumar <neeru(dot)cse(at)gmail(dot)com> writes:
> Took some time to get stack trace as we didn't had root permission.
> Attaching stack trace of two process (out of many) stuck for same query
> below[1][2]

Hmm, the line numbers in your stack traces don't agree with either v10
or HEAD branches for me. But assuming that you've correctly identified
where it's stuck:

> Seems like call is unable to come out of this loop :
> https://github.com/postgres/postgres/blob/master/src/backend/postmaster/pgstat.c#L3361-L3400

the only really obvious theory is that some process left its
st_changecount odd, which would more or less have to imply that
something threw an error between pgstat_increment_changecount_before
and pgstat_increment_changecount_after. There's only one place
where that seems very plausible, namely pgstat_bestart, which is
doing a rather scary amount of stuff in between. Are you using
either SSL or GSS?

regards, tom lane