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Date:      Tue, 09 Apr 2002 19:23:40 +0200
From:      "Rogier R. Mulhuijzen" <drwilco@drwilco.net>
To:        Terry Lambert <tlambert2@mindspring.com>, callum.gibson@db.com
Cc:        hackers@FreeBSD.ORG
Subject:   Re: ipcrm/shmctl failure
Message-ID:  <5.1.0.14.0.20020409192018.01c667a0@mail.drwilco.net>
In-Reply-To: <3CB276CB.89703872@mindspring.com>
References:  <20020408225938.2069.qmail@merton.aus.deuba.com>

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At 22:06 8-4-2002 -0700, Terry Lambert wrote:
>All you are doing is marking the segment as removed.  The segment
>remains attached by the processes which have it open, and those
>references don't go awaya until the processes in question detach
>the segments, and the reference count goes to zero.

>It turns out that these segments are not proerly reference
>counted and tracked, so they are not deleted when the client
>"goes away".
>
>This is a bug in the MIT shared memory extension for X design,
>and can't be fixed for long running programs with lots of
>bitmaps.

I'd like to take a step further and say it's in SYSVSHM design. All a 
program has to do is forget to do a shm_detach() and you're f#$%ed.

Be glad it's just a few bitmaps, and not a 250 meg segment like I had with 
a certain version of Oracle.

>It's an X11 question, and it's been that way since at least 1994,
>so it's a long standing X11 FAQ.

You could say that X11 shouldn't use SHMs the way it does now yeah. =)


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