On Sat, Jun 09, 2007 at 03:49:46PM +0900, Tejun Heo wrote:

quoted text
> Tejun Heo wrote:

> > Tejun Heo wrote:

> >> Greg KH wrote:

> >>> 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?

> >> I'll resend with S-O-B after someone verifies it fixes the problem.

> >

> > Have been trying to reproduce the problem on the latest -rc but haven't

> > succeeded yet.  It seems I lost my magic recipe for these races.  Did

> > anyone succeed?

>

> Alright, overnight test finally hit the race condition.  It takes me

> much longer now but the race condition is definitely still there.  I'll

> verify each proposed patch and send it for 2.6.22 inclusion and if

> they're accepted to -stable.

Ok, thanks for doing this.
greg k-h

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