linux-kernel - Re: 3.5-rc6 futex_wait_requeue

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Date:	Fri, 20 Jul 2012 08:10:05 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Dave Jones <davej@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Darren Hart <darren@...art.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: 3.5-rc6 futex_wait_requeue_pi oops.



On 07/20/2012 06:35 AM, Dave Jones wrote:
> On Thu, Jul 19, 2012 at 11:53:45PM -0700, Darren Hart wrote:
> 
>  
>  > >> I'll add a fix to that WARN_ON in my futex-fixes branch along with the
>  > >> fix for the bug Dan found.
>  > > 
>  > > I think I have root cause. futex_wait_requeue_pi() doesn't like having
>  > > uaddr == uaddr2. The handle_early_wakeup() doesn't detect a problem
>  > > because key2 IS the same as key1, I think. I've just discovered this and
>  > > quickly hacked in a "if (uaddr==uaddr2) return -EINVAL" fix and the test
>  > > continues to run (with just ops 0, 11, 12) for several minutes now
>  > > (typically fails in a few seconds). I'll let it run for a few hours and
>  > > contemplate the proper fix.
>  > 
>  > Dave, mind giving this a spin? It seems to be doing the trick here,
>  > at least for the *REQUEUE_PI futex op codes in trinity.
> 
> Yeah, looks like that does the trick!

It ran all night without an issue here too. I'll roll these up and send
them out shortly.

Dave, I love/hate trinity. ;-)

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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