linux-kernel - Re: drm_vm.c:drm_mmap: possible circular locking dependency detected

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Message-ID: <4B427547.5070109@kernel.org>
Date:	Tue, 05 Jan 2010 08:09:59 +0900
From:	Tejun Heo <tj@...nel.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Borislav Petkov <petkovbb@...glemail.com>,
	David Airlie <airlied@...ux.ie>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>, Al Viro <viro@...IV.linux.org.uk>
Subject: Re: drm_vm.c:drm_mmap: possible circular locking dependency detected

Hello,

On 01/05/2010 04:43 AM, Eric W. Biederman wrote:
>>> So it is unlikely but possible to deadlock by accessing a serio
>>> attribute of a serio device that is being removed.
>>
>> Hmm, I guess I was too quick dismissing lockdep complaints here. Now
>> that sysfs remove waits deadlock indeed is possible. Actually the locks
>> on serio->drv_mutex in attributes were added to make sure we don't
>> access device that was unbound from the driver through stale sysfs
>> attributes.
> 
> Cool.  So we have solved the problem generically but we have left over
> layer specific solutions.  That seems like a good problem to have.

This is way too cool.  Only if we can have more moments like this.  :-)

-- 
tejun
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