Date: Tue, 24 Apr 2018 07:06:46 +0000
From: Noah Misch <noah@leadboat.com>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Stephen Frost <sfrost@snowman.net>, Tom Lane <tgl@sss.pgh.pa.us>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: "could not reattach to shared memory" on buildfarm member dory
Message-ID: <20180424070646.GA2693533@rfd.leadboat.com>
References: <25495.1524517820@sss.pgh.pa.us>
 <20180423231855.GK27724@tamriel.snowman.net>
 <CAEepm=0kRF7Hrd2R72FJLdQneV1HATjJM_ArbjZw=-ZF3RT7+Q@mail.gmail.com>
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On Tue, Apr 24, 2018 at 11:37:33AM +1200, Thomas Munro wrote:
> On Tue, Apr 24, 2018 at 11:18 AM, Stephen Frost <sfrost@snowman.net> wrote:
> > Greetings,
> >
> > * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> >> So far, dory has failed three times with essentially identical symptoms:
> >>
> >> 2018-04-23 19:57:10.624 GMT [2240] FATAL:  could not reattach to shared memory (key=0000000000000190, addr=00000000018E0000): error code 487
> >> 2018-04-23 15:57:10.657 EDT [8836] ERROR:  lost connection to parallel worker
> >> 2018-04-23 15:57:10.657 EDT [8836] STATEMENT:  select count(*) from tenk1 group by twenty;
> >> 2018-04-23 15:57:10.660 EDT [3820] LOG:  background worker "parallel worker" (PID 2240) exited with exit code 1
> >>
> >> Now how can this be?  We've successfully reserved and released the address
> >> range we want to use, so it *should* be free at the instant we try to map.
> >
> > Yeah, that's definitely interesting.
> 
> I wondered if another thread with the right timing could map something
> between the VirtualFree() and MapViewOfFileEx() calls, but  we don't
> create the Windows signal handling thread until a bit later.  Could
> there be any any other threads active in the process?
> 
> Maybe try asking what's mapped there with VirtualQueryEx() on failure?

+1.  An implementation of that:
https://www.postgresql.org/message-id/20170403065106.GA2624300%40tornado.leadboat.com