From: Christoph Rohland <cr@sap.com>
To: Dave Gilbert <gilbertd@treblig.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: shmat returning NULL with 0 sized segment
Date: 26 Dec 2000 10:31:37 +0100 [thread overview]
Message-ID: <m3vgs8b9u5.fsf@linux.local> (raw)
In-Reply-To: <Pine.LNX.4.10.10012250109450.666-100000@tardis.home.dave>
In-Reply-To: <Pine.LNX.4.10.10012250109450.666-100000@tardis.home.dave>
Dave Gilbert <gilbertd@treblig.org> writes:
> I'm trying to debug a weird problem with Xine - its screwing up its use
> of shared memory for regions I haven't sussed yet. One odd consequence is
> that it has apparently successfully managed to allocate a 0 byte chunk of
> shared memory; shmat is then called with shmaddr=0 and shmflg=0; the
> result of shmat is 0
>
> Is this what shmat is supposed to do in this (admittedly odd)
> circumstance? The error behaviour is defined in the man page as returning
> -1 on error.
Yes, this should be competely legal and wanted. Some programs use
shmget (..,0,..) to test if the segment is there. Apparently Xine does
this while setting the IPC_CREATE flag. This is legal on 2.4 (wasn't
in 2.2) and gives you a 0 byte segment.
shmat will give you then the legal address 0 like mmap would.
Greetings
Christoph
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prev parent reply other threads:[~2000-12-26 9:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-12-25 1:13 shmat returning NULL with 0 sized segment Dave Gilbert
2000-12-26 9:31 ` Christoph Rohland [this message]
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