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To: Dave Chinner <david@fromorbit.com>
Cc: Tejun Heo <tj@kernel.org>, "Rafael J. Wysocki" <rjw@sisk.pl>,
       =?utf-8?Q?Am=C3=A9rico?= Wang <xiyou.wangcong@gmail.com>,
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       Arjan van de Ven <arjan@infradead.org>,
       Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>
Subject: Re: 2.6.33-rc3 -- INFO: possible recursive locking -- (s_active){++++.+}, at: [<c10d2941>] sysfs_hash_and_remove+0x3d/0x4f
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	<m11vhw6u3k.fsf@fess.ebiederm.org>
	<20100112030134.GA17483@discord.disaster>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: Tue, 12 Jan 2010 01:22:31 -0800
In-Reply-To: <20100112030134.GA17483@discord.disaster> (Dave Chinner's message of "Tue\, 12 Jan 2010 14\:01\:34 +1100")
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Dave Chinner <david@fromorbit.com> writes:

> On Mon, Jan 11, 2010 at 04:32:31PM -0800, Eric W. Biederman wrote:
>> Tejun Heo <tj@kernel.org> writes:
>> 
>> > On 01/11/2010 11:26 AM, Eric W. Biederman wrote:
>> >> From: Eric W. Biederman <ebiederm@xmission.com>
>> >> Date: Sun, 10 Jan 2010 18:13:35 -0800
>> >> Subject: [PATCH] sysfs: Add support for lockdep subclasses to s_active
>> >> 
>> >> We have apparently valid cases where the code for a sysfs attribute
>> >> removes other sysfs attributes.  Without support for subclasses
>> >> lockdep flags a possible recursive lock problem as it figures
>> >> the first sysfs attribute could be attempting to remove itself.
>> >> 
>> >> By adding support for sysfs subclasses we can teach lockdep to
>> >> distinguish between different types of sysfs attributes and not
>> >> get confused.
>> >> 
>> >> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
>> >
>> > Acked-by: Tejun Heo <tj@kernel.org>
>> 
>> Now if I can just get a Tested-by  this patch will be all set ;)
>
> Hi Eric,
>
> Is this the same locking problem that this patch fixes?
>
> http://lkml.org/lkml/2010/1/11/26

It certainly looks similar.   The sysfs file that is being written
is different so I can't tell if that is a false positive because
sysfs is used for everything, or if it is a real issue.

Eric
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