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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/
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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=m3vgs8b9u5.fsf@linux.local \
--to=cr@sap.com \
--cc=gilbertd@treblig.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.