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Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x

To: "Alexander Beregalov" <a.beregalov@xxxxxxxxx>, rjw@xxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, kernel-testers@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Subject: Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8
From: "Alexander Beregalov" <a.beregalov@xxxxxxxxx>
Date: Wed, 17 Sep 2008 22:33:28 +0400
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2008/9/16 Alexander Beregalov <a.beregalov@xxxxxxxxx>:
> 2008/9/16 Dave Chinner <david@xxxxxxxxxxxxx>:
>> On Sun, Sep 14, 2008 at 03:31:38AM +0400, Alexander Beregalov wrote:
>>> Hi
>>>
>>> [ INFO: possible circular locking dependency detected ]
>>> 2.6.27-rc6-00034-gd1c6d2e #3
>>> -------------------------------------------------------
>>> nfsd/1766 is trying to acquire lock:
>>>  (iprune_mutex){--..}, at: [<c01743fb>] shrink_icache_memory+0x38/0x1a8
>>>
>>>  but task is already holding lock:
>>>   (&(&ip->i_iolock)->mr_lock){----}, at: [<c021134f>]
>>>   xfs_ilock+0xa2/0xd6
>>>
>>>
>>> I read files through nfs and saw delay for few seconds.
>>> System is x86_32, nfs, xfs.
>>> The last working kernel is 2.6.27-rc5,
>>> I do not know yet is it reproducible or not.
>>
>> <sigh>
>>
>> We need a FAQ for this one. It's a false positive.  Google for an
>> explanation - I've explained it 4 or 5 times in the past year and
>> asked that the lockdep folk invent a special annotation for the
>> iprune_mutex (or memory reclaim) because of the way it can cause
>> recursion into the filesystem and hence invert lock orders without
>> causing deadlocks.....
>
> Hi Dave
>
> Yes, you already explained a similar message to me, but it was a bug,
> not false positive.
> http://lkml.org/lkml/2008/7/3/29
> http://lkml.org/lkml/2008/7/3/315
>
> I will try to bisect.
> It is not a OOM case.
>
I can not reproduce it.

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