From: Andi Kleen <ak@suse.de>
Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)
To: Trond Myklebust <Trond.Myklebust@netapp.com>
Subject: Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote_llseek
Date: Mon, 28 Jan 2008 05:38:25 +0100
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Cc: Steve French <smfrench@gmail.com>, swhiteho@redhat.com, sfrench@samba.org,
       vandrove@vc.cvut.cz, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org, akpm@osdl.org
References: <20080127317.043953000@suse.de> <200801280358.14024.ak@suse.de> <1201493589.8132.7.camel@heimdal.trondhjem.org>
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On Monday 28 January 2008 05:13:09 Trond Myklebust wrote:
> 
> On Mon, 2008-01-28 at 03:58 +0100, Andi Kleen wrote:
> > The problem is that it's not a race in who gets to do its thing first, but a 
> > parallel reader can actually see a corrupted value from the two independent 
> > words on 32bit (e.g. during a 4GB). And this could actually completely corrupt 
> > f_pos when it happens with two racing relative seeks or read/write()s
> > 
> > I would consider that a bug.
> 
> I disagree. The corruption occurs because this isn't a situation that is
> allowed by either POSIX or SUSv2/v3. Exactly what spec are you referring
> to here?

No specific spec, just general quality of implementation. We normally don't have
non thread safe system calls even if it was in theory allowed by some specification.

-Andi
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