linux-kernel - Re: [PATCH 2/2] sysfs: fix race condition around sd->s

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Date:	Tue, 22 May 2007 15:38:41 -0700
From:	Greg KH <greg@...ah.com>
To:	Maneesh Soni <maneesh@...ibm.com>
Cc:	Tejun Heo <htejun@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Clemens Schwaighofer <cs@...uila.co.jp>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Chuck Ebbert <cebbert@...hat.com>
Subject: Re: [PATCH 2/2] sysfs: fix race condition around sd->s_dentry,
	take#2

On Mon, May 21, 2007 at 10:31:01AM +0530, Maneesh Soni wrote:
> On Thu, May 17, 2007 at 08:16:10PM +0200, Tejun Heo wrote:
> > Allowing attribute and symlink dentries to be reclaimed means
> > sd->s_dentry can change dynamically.  However, updates to the field
> > are unsynchronized leading to race conditions.  This patch adds
> > sysfs_lock and use it to synchronize updates to sd->s_dentry.
> > 
> > Due to the locking around ->d_iput, the check in sysfs_drop_dentry()
> > is complex.  sysfs_lock only protect sd->s_dentry pointer itself.  The
> > validity of the dentry is protected by dcache_lock, so whether dentry
> > is alive or not can only be tested while holding both locks.
> > 
> > This is minimal backport of sysfs_drop_dentry() rewrite in devel
> > branch.
> > 
> > DONT APPLY JUST YET
> 
> Looks ok to me.. I have tested it it but unfortunately I couldn't
> recreate the race without the patch also. It would be helpful if
> people actually seeing the race, provide the test results.
> 
> Greg, please merge this one once we have some test results.

Can someone just resend it after those test results are in, with the
proper signed-off-by, so I know it's safe to apply?

thanks,

greg k-h
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