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

[Cong Wang <amwang@redhat.com>]

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?  :-)
>> 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:
> 
> [    0.397123] 
> [    0.397124] =============================================
> [    0.397359] [ INFO: possible recursive locking detected ]
> [    0.397480] 2.6.33-rc6-mm1 #1
> [    0.397596] ---------------------------------------------
> [    0.397717] swapper/1 is trying to acquire lock:
> [    0.397836]  (&dev->mutex){+.+...}, at: [<c12662e4>] __driver_attach+0x38/0x63
> [    0.398162] 
> [    0.398162] but task is already holding lock:
> [    0.398393]  (&dev->mutex){+.+...}, at: [<c12662d8>] __driver_attach+0x2c/0x63
> [    0.399999] 

Alan already provided a patch for this issue earlier in this thread.

Thanks.