Re: [Patch 0/2] sysfs: fix s_active lockdep warning

[Dave Young]

On Mon, Feb 8, 2010 at 11:08 AM, Cong Wang <amwang@xxxxxxxxxx> wrote:
> Dave Young wrote:
>>
>> On Fri, Feb 05, 2010 at 04:41:57PM +0100, Peter Zijlstra wrote:
>>>
>>> On Fri, 2010-02-05 at 10:30 -0500, Alan Stern wrote:
>>>>
>>>> On Fri, 5 Feb 2010, Peter Zijlstra wrote:
>>>>
>>>>> Right, so this device stuff is much more complicated than I was led to
>>>>> believe ;-)
>>>>
>>>> Haven't I told you all along that tree-structured locking is
>>>> complicated? Â:-)
>>>
>>> Well, regular tree's aren't all that complicated, but multiple
>>> inter-locking trees is a whole different story indeed.
>>>
>>
>> I ever tried converting device semaphore to mutex, but failed with same
>> issue.
>>
>> At least now there's no lockdep solution for it, so I recommend revert
>> the mutex converting patch.
>>
>> following lockdep warning with rc6-mm1:
>>
>> [ Â Â0.397123] [ Â Â0.397124]
>> =============================================
>> [ Â Â0.397359] [ INFO: possible recursive locking detected ]
>> [ Â Â0.397480] 2.6.33-rc6-mm1 #1
>> [ Â Â0.397596] ---------------------------------------------
>> [ Â Â0.397717] swapper/1 is trying to acquire lock:
>> [ Â Â0.397836] Â(&dev->mutex){+.+...}, at: [<c12662e4>]
>> __driver_attach+0x38/0x63
>> [ Â Â0.398162] [ Â Â0.398162] but task is already holding lock:
>> [ Â Â0.398393] Â(&dev->mutex){+.+...}, at: [<c12662d8>]
>> __driver_attach+0x2c/0x63
>> [ Â Â0.399999]
>
> Alan already provided a patch for this issue earlier in this thread.

Yes, but device locks can not be classified with regular tree style.
Please read the whole thread.

>
> Thanks.
>
>



-- 
Regards
dave
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