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Subject: Re: Linux kernel file offset pointer races
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Pavel Kankovsky <peak@argo.troja.mff.cuni.cz>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Fri, 06 Aug 2004 13:56:36 +0100
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On Mer, 2004-08-04 at 21:36, Pavel Kankovsky wrote:
> IMHO, the proper fix is to serialize all operations modifying a shared
> file pointer (file->f_pos): read(), readv(), write(), writev(),
> lseek()/llseek(). As far as I can tell, this is required by POSIX:

Not if you want to get any useful work done. No Unix does this. The
situation with multiple parallel lseek/read/writes is somewhat undefined
anyway since you don't know if the seek or the write occurred first in
user space.

O_APPEND is a bit different, as are pread/pwrite but those are dealt
with using locking for files.