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From: Jonathan Rudenberg <jonathan@titanous.com>
To: Robert Haas <robertmhaas@gmail.com>,
 Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Andreas Seltenreich <seltenreich@gmx.de>,
 Pg Hackers <pgsql-hackers@postgresql.org>
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In-Reply-To: 
 <CA+TgmoZfPOu62bR71bahf90ivOUxXpYOh0RqDiue0+dVVPNrWg@mail.gmail.com>
Subject: Re: [sqlsmith] Unpinning error in parallel worker
References: <87h92g83t3.fsf@credativ.de>
 <CAEepm=1sLjHyauGZoXM3KCT2Gv+CHPEWQcxob_1Oo0KshRp7-Q@mail.gmail.com>
 <CAEepm=2VvKCVXjg-REHTikoBUOhtfvfCyiJrT=zHDJyvMNd9pw@mail.gmail.com>
 <CAEepm=23=vGz=CgVurPxBGV6SeOJ7YxSaAJKr_aH+f2cV4zrow@mail.gmail.com>
 <CA+TgmoZfPOu62bR71bahf90ivOUxXpYOh0RqDiue0+dVVPNrWg@mail.gmail.com>
Date: Tue, 17 Apr 2018 16:52:31 -0400
Precedence: bulk

On Wed, Mar 29, 2017, at 10:50, Robert Haas wrote:
> On Wed, Mar 29, 2017 at 1:31 AM, Thomas Munro
> <thomas.munro@enterprisedb.com> wrote:
> > I considered whether the error message could be improved but it
> > matches the message for an existing similar case (where you try to
> > attach to an unknown handle).
> 
> Ugh, OK.  I committed this, but I think this whole file needs a visit
> from the message style police.

I ran into an issue that matches the symptoms of this bug on a production cluster running 10.3 (Ubuntu 10.3-1.pgdg16.04+1) twice in the past week.

Hundreds of queries stuck with a wait_event of DynamicSharedMemoryControlLock and pg_terminate_backend did not terminate the queries.

In the log:

> FATAL:  cannot unpin a segment that is not pinned

I don't have a backtrace yet, but I will provide them if/when the issue happens again.

Jonathan