Date: Sun, 6 Jul 2008 01:11:48 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Frans Pop <elendil@planet.nl>,
       "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] parport/ppdev: fix registration of sysctl entries
Message-ID: <20080706001148.GX28946@ZenIV.linux.org.uk>
References: <20080705131924.GA2083@joi> <20080705235148.GW28946@ZenIV.linux.org.uk>
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On Sun, Jul 06, 2008 at 12:51:48AM +0100, Al Viro wrote:

> I don't believe that it's right.  Note that if you *do* race there, you
> are fucked regardless of sysctls - ppdev.c::register_device() racing
> with itself will do tons of fun things all by itself (starting with two
> threads allocating different pdev and both setting pp->pdev).
> 
> IOW, *if* that's what we are hitting here, you've only papered over the
> visible symptom.

BTW, with your patch you'll have 100% reproducible double registration if
you do PPCLAIM/PPRELEASE/PPCLAIN on one file descriptor.
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