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From: Peter Zijlstra <peterz@infradead.org>
To: Michael Wu <flamingice@sourmilk.net>
Cc: "Luis R. Rodriguez" <mcgrof@gmail.com>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	"John W. Linville" <linville@tuxdriver.com>,
	Ingo Molnar <mingo@redhat.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	linux-kernel@vger.kernel.org
Subject: Re: RFC: Reproducible oops with lockdep on count_matching_names()
Date: Fri, 02 Nov 2007 11:58:40 +0100	[thread overview]
Message-ID: <1194001120.27652.353.camel@twins> (raw)
In-Reply-To: <200711011926.07641.flamingice@sourmilk.net>

On Thu, 2007-11-01 at 19:26 -0400, Michael Wu wrote:
> On Thursday 01 November 2007 15:17:16 Luis R. Rodriguez wrote:
> > mcgrof@pogo:~/devel/wireless-2.6$ git-describe
> > v2.6.24-rc1-146-g2280253
> >
> > So I hit segfault with lockdep on count_matching_names() on the
> > strcmp() multiple times now. This is reproducible and with different
> > wireless drivers.
> >
> I've found the problem. It appears to be in lockdep. struct lock_class has a 
> const char *name field which points to a statically allocated string that 
> comes from the code which uses the lock. If that code/string is in a module 
> and gets unloaded, the pointer in |name| is no longer valid. Next time this 
> field is dereferenced (count_matching_names, in this case), we crash.
> 
> The following patch fixes the issue but there's probably a better way.

Thanks, and indeed. From my understanding lockdep_free_key_range()
should destroy all classes of a module on module unload.

So I'm not quite sure what has gone wrong here..



  reply	other threads:[~2007-11-02 10:58 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-01 19:17 RFC: Reproducible oops with lockdep on count_matching_names() Luis R. Rodriguez
2007-11-01 19:49 ` John W. Linville
2007-11-01 21:29   ` Luis R. Rodriguez
2007-11-01 23:26 ` Michael Wu
2007-11-02 10:58   ` Peter Zijlstra [this message]
2007-11-03 19:58     ` Luis R. Rodriguez
2007-11-03 20:06       ` Michael Buesch
2007-11-03 20:06         ` Michael Buesch
2007-11-05 12:00         ` Peter Zijlstra
2007-11-05 12:00           ` Peter Zijlstra
2007-11-05 12:23           ` Pekka Enberg
2007-11-05 12:23             ` Pekka Enberg
2007-11-05 13:03             ` Michael Buesch
2007-11-05 13:03               ` Michael Buesch
2007-11-05 13:56               ` Pekka Enberg
2007-11-05 13:56                 ` Pekka Enberg
2007-11-05 14:26                 ` Michael Buesch
2007-11-05 14:26                   ` Michael Buesch
2007-11-05 18:47                   ` Christoph Lameter

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