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Re: Posix Shared Mem patch

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Magnus Hagander <magnus(at)hagander(dot)net>,"A(dot)M(dot)" <agentm(at)themactionfaction(dot)com>,Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Posix Shared Mem patch
Date: 2012-06-27 13:53:46
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
* Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> Right, but does it provide honest protection against starting two
> postmasters in the same data directory?  Or more to the point,
> does it prevent starting a new postmaster when the old postmaster
> crashed but there are still orphaned backends making changes?
> AFAIR we basically punted on those problems for the Windows port,
> for lack of an equivalent to nattch.

See my other mail, but, after talking to Magnus, it's my understanding
that we had that problem initially, but it was later solved by using a
named shared memory segment which the kernel will clean up when all
children are gone.  That, combined with a 'create-if-exists' call,
allows detection of lost children to be done.



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