linux-kernel - Re: [Patch 0/2] sysfs: fix s

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Date:	Mon, 08 Feb 2010 11:08:45 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Dave Young <hidave.darkstar@...il.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Alan Stern <stern@...land.harvard.edu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg KH <gregkh@...e.de>, Thomas Gleixner <tglx@...utronix.de>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Miles Lane <miles.lane@...il.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Larry Finger <Larry.Finger@...inger.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Patch 0/2] sysfs: fix s_active lockdep warning

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.

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