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Date: Thu, 14 Jul 2011 13:33:36 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Dave Jones <davej@redhat.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dipankar Sarma <dipankar@in.ibm.com>, linux-kernel@vger.kernel.org
Subject: Re: INFO: possible circular locking dependency detected
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On Thu, Jul 14, 2011 at 03:38:28PM -0400, Dave Jones wrote:
> On Thu, Jul 14, 2011 at 12:34:12PM -0700, Paul E. McKenney wrote:
> 
>  > Thank you -- you were indeed running with CONFIG_PREEMPT and
>  > CONFIG_RCU_BOOST, which would be the case for the bug that Steven Rostedt
>  > found.  On reproducing, yes, it could be a bit tough, as the race window
>  > is rather narrow.  I could probably add delays to force the situation htat
>  > Steven found, but it would be hard to prove that this is your situation.
>  > 
>  > Dave, was your lockdep splat also with CONFIG_PREEMPT and
>  > CONFIG_RCU_BOOST?
> 
> yeah. which might explain why I haven't seen it since. (I usually have it
> disabled, but turn it on occasionally for a 'lets see what breaks' test)

OK, thanks for the info.  For the time being, I will assume that you
were seeing this same bug.

							Thanx, Paul