From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Tue, 6 Dec 2011 19:11:09 +0000
Subject: [PATCH] ARM: futex: fix clobbering oldval
In-Reply-To: <1323197914.11696.30.camel@constitution.bos.jonmasters.org>
References: <1316660015.6872.1.camel@puffmine-laptop>
 <20110922172653.GH13572@e102144-lin.cambridge.arm.com>
 <1323197914.11696.30.camel@constitution.bos.jonmasters.org>
Message-ID: <20111206191109.GB5385@mudshark.cambridge.arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Jon,

On Tue, Dec 06, 2011 at 06:58:34PM +0000, Jon Masters wrote:
> On Thu, 2011-09-22 at 18:26 +0100, Will Deacon wrote:
> > Hi,
> > 
> > On Thu, Sep 22, 2011 at 03:53:35AM +0100, mhban wrote:
> > > This patch fixes clobbering oldval bug. oldval should be preserved for next
> > > compare operation.
> > > 
> > > Change-Id: I2a63bc1bdb8de330eb9e1ac02d7da1f77e6e8c3c
> > > Signed-off-by: Minho Ban <mhban@samsung.com>
> > 
> > It would have been nice to have been CC'd on this...
> > 
> > I ran LTP tests on this, so I'm surprised that this was broken (the tests
> > passed). Well spotted anyway!
> 
> This appears to be the cause of our "stuck builder" problem in Fedora
> building certain large packages, such as OpenJDK. Some of our guys are
> still monitoring the situation in case there's a secondary issue.
> 
> Was there ever any additional followup on this topic?

Yup, check commit df77abca ("ARM: 7099/1: futex: preserve oldval in SMP
__futex_atomic_op"). It should be in stable for all affected kernels too.

Cheers,

Will