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From: Justin Pryzby <pryzby@telsasoft.com>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Sergei Kornilov <sk@zsrv.org>
Cc: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
Subject: Re: pg11.1: dsa_area could not attach to segment
Date: Thu, 14 Feb 2019 10:20:10 -0600
Message-ID: <20190214162010.GM30291@telsasoft.com> (raw)
In-Reply-To: <CAEepm=22ug5qu5ZgHnbE9KUioKS7Dtv929tzCHN821gXFKaB_A@mail.gmail.com>
References: <20190206071940.GB29720@telsasoft.com>
	<CAEepm=18oK3LCKnPbMQeYumFVM=ZPA_v_RmsVBaP1eeF6LOB7Q@mail.gmail.com>
	<20190207014719.GJ29720@telsasoft.com>
	<20190211040132.GV31721@telsasoft.com>
	<67790871549896669@iva5-d3020dc3459d.qloud-c.yandex.net>
	<CAEepm=2=BFXs_+8X-eEyNBpG0OddaWe190KQaOX2TE5aS8UL-A@mail.gmail.com>
	<20190212024314.GC31721@telsasoft.com>
	<20190212050058.GF31721@telsasoft.com>
	<2614901549962899@sas1-4b7566131ec9.qloud-c.yandex.net>
	<CAEepm=22ug5qu5ZgHnbE9KUioKS7Dtv929tzCHN821gXFKaB_A@mail.gmail.com>

On Fri, Feb 15, 2019 at 01:12:35AM +1300, Thomas Munro wrote:
> The problem is that a DSM handle (ie a random number) can be reused
> for a new segment immediately after the shared memory object has been
> destroyed but before the DSM slot has been released.  Now two DSM
> slots have the same handle, and dsm_attach() can be confused by the
> old segment and give up.
> 
> Here's a draft patch to fix that.  It also clears the handle in a case
> where it wasn't previously cleared, but that wasn't strictly
> necessary.  It just made debugging less confusing.

Thanks.

Do you think that plausibly explains and resolves symptoms of bug#15585, too?

Justin




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