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From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Jones <davej@redhat.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Darren Hart <darren@dvhart.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: 3.5-rc6 futex_wait_requeue_pi oops.
Date: Fri, 13 Jul 2012 21:11:57 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.02.1207132108340.32033@ionos> (raw)
In-Reply-To: <20120713185402.GA1707@redhat.com>

On Fri, 13 Jul 2012, Dave Jones wrote:

> On Fri, Jul 13, 2012 at 08:47:38PM +0200, Thomas Gleixner wrote:
>  > On Fri, 13 Jul 2012, Dave Jones wrote:
>  > 
>  > > Looks like calling futex() with garbage makes things unhappy.
>  > 
>  >                 WARN_ON(!&q.pi_state);
>  >                 pi_mutex = &q.pi_state->pi_mutex;
>  >                 ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1);
>  >                 debug_rt_mutex_free_waiter(&rt_waiter);
>  > 
>  > So there is some weird way which causes q.pi_state = NULL. Dave, did
>  > you see the warning before the oops happened ?
> 
> No, that didn't seem to trigger.

Yuck. The rt_mutex is embedded in pi_state and not a pointer and the
thing explodes in __lock_acquire if the raw lock protecting the
rtmutex internals. 

Can you decode the exact code line ?

Thanks,

	tglx



  reply	other threads:[~2012-07-13 19:12 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-13 18:08 Dave Jones
2012-07-13 18:47 ` Thomas Gleixner
2012-07-13 18:54   ` Dave Jones
2012-07-13 19:11     ` Thomas Gleixner [this message]
2012-07-13 19:56       ` Dave Jones
     [not found]         ` <CAGChsmNnE_iEKWagULzewSPWsAbaA2A-mXg4CS+vyG3a8Pbj1A@mail.gmail.com>
2012-07-13 20:54           ` Dave Jones
2012-07-19 23:22     ` Darren Hart
2012-07-20  0:37       ` Darren Hart
2012-07-20  6:53         ` Darren Hart
2012-07-20 13:35           ` Dave Jones
2012-07-20 15:10             ` Darren Hart

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