From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@lists.postgresql.org
Subject: Re: SIGQUIT handling, redux
In-reply-to: <20200909202201.unpjmshshu7sge6i@alap3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Wed, 09 Sep 2020 13:22:01 -0700"
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Date: Wed, 09 Sep 2020 16:30:37 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2020-09-09 16:09:00 -0400, Tom Lane wrote:
>> We could call it startup_packet_die or something?

> Yea, I think that'd be good.

I'll make it so.

>> We see backends going through this code on a very regular basis in the
>> buildfarm, but complete hangs are rare as can be.  I think you
>> overestimate the severity of the problem.

> I don't think the BF exercises the problmetic paths to a significant
> degree. It's mostly local socket connections, and where not it's
> localhost. There's no slow DNS, no more complicated authentication
> methods, no packet loss. How often do we ever actually end up even
> getting close to any of the paths but immediate shutdowns?

Since we're talking about quickdie(), immediate shutdown/crash restart
is exactly the case of concern, and the buildfarm exercises it all the
time.

> And in the
> SIGQUIT path, how often do we end up in the SIGKILL path, masking
> potential deadlocks?

True, we can't really tell that.  I wonder if we should make the
postmaster emit a log message when it times out and goes to SIGKILL.
After a few months we could scrape the buildfarm logs and get a
pretty good handle on it.

			regards, tom lane