linux-kernel - Re: sysfs: use a separate locking class for open files depending on mmap

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Date:	Tue, 3 Dec 2013 16:36:49 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	gregkh@...uxfoundation.org
Subject: Re: sysfs: use a separate locking class for open files depending on
 mmap

Hey,

On Tue, Dec 03, 2013 at 04:15:15PM -0500, Dave Jones wrote:
>  > > Somehow I just triggered this trace again, even with this commit applied.
>  > > The trace is pretty much identical to the old one.
>  > 
>  > Hah, ain't that weird.  That's the trace you reported on the other
>  > mail, right?  I'll follow up on that one.
> 
> just so there's no doubt, here's a fresh one.

Argh, found the culprit.  The unified mmap path grabs of->mutex to
check whether the file implements mmap, which means that if you try to
mmap a file which doesn't implement mmap, you still add the locking
dependency.  I'm working on the fix.

Thanks.

-- 
tejun
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