linux-kernel - Re: 3.5-rc6 futex_wait_requeue

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Message-ID: <20120720133501.GA30826@redhat.com>
Date:	Fri, 20 Jul 2012 09:35:01 -0400
From:	Dave Jones <davej@...hat.com>
To:	Darren Hart <dvhart@...ux.intel.com>
Cc:	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 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!

thanks,

	Dave
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