Date: Thu, 31 Oct 2013 15:43:17 +0100
From: Andres Freund <andres@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
 Heikki Linnakangas <hlinnakangas@vmware.com>,
 Andrew Dunstan <andrew@dunslane.net>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: Something fishy happening on frogmouth
Message-ID: <20131031144317.GA24221@alap2.anarazel.de>
References: <6557.1383073940@sss.pgh.pa.us>
 <CA+Tgmob859sdnDuHAF31BE55qEoREnCzzWeqDbgkNB0d_F+zmA@mail.gmail.com>
 <27889.1383139602@sss.pgh.pa.us>
 <20131030133718.GB11429@awork2.anarazel.de>
 <28492.1383140966@sss.pgh.pa.us>
 <CA+TgmobOqYVBD=xdWHF12R4+dxeBDS3ruxware7ZWtD5mfSO5Q@mail.gmail.com>
 <527223E8.2020207@vmware.com>
 <20131031095021.GA31628@alap2.anarazel.de>
 <CA+Tgmoa6gJAPeMKCK77xzUbhqriO0C+24Ow7ezz4GP8wHCF-EA@mail.gmail.com>
 <22875.1383229757@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <22875.1383229757@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

On 2013-10-31 10:29:17 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Thu, Oct 31, 2013 at 5:50 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> >> On 2013-10-31 11:33:28 +0200, Heikki Linnakangas wrote:
> >>> Wait, that sounds horrible. If you kill -9 the server, and then rm -rf
> >>> $PGDATA, the shared memory segment is leaked until next reboot?
> 
> >> Our main shared memory segment works the same way, doesn't it? And it
> >> has for a long time.
> 
> > It does, and what's the alternative, anyway?
> 
> Well, what we expect from the existing shmem code is that restarting the
> postmaster will clean things up, ie find and destroy the leaked shmem.
> It sounds to me like this may not work like that, in which case I agree
> with Heikki that it's not really acceptable.

The code writes a state file containing the identity of the dsm "control
segment" used last time. That state file is read at startup and if it
still exists used to attach to the control segment which contains a list
of "user defined" dsm segments so they can be cleaned up

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers