Date: Sun, 12 May 2013 13:58:24 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: =?iso-8859-1?Q?Bj=F8rn?= Mork <bjorn@mork.no>
Cc: Dipankar Sarma <dipankar@in.ibm.com>, linux-kernel@vger.kernel.org,
        rostedt@goodmis.org
Subject: Re: [v3.10-rc1] WARNING: at kernel/rcutree.c:502
Message-ID: <20130512205824.GL3648@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <87ip2opntp.fsf@nemi.mork.no>
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 <87li7kp50r.fsf@nemi.mork.no>
 <20130512172135.GJ3648@linux.vnet.ibm.com>
 <87a9o0ukll.fsf@nemi.mork.no>
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On Sun, May 12, 2013 at 08:19:34PM +0200, Bj?rn Mork wrote:
> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
> > On Sun, May 12, 2013 at 05:55:00PM +0200, Bj?rn Mork wrote:
> >> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
> >> > On Sun, May 12, 2013 at 11:08:50AM +0200, Bj?rn Mork wrote:
> >> >> Hello,
> >> >> 
> >> >> got the splat below when running powertop on plain v3.10-rc1
> >> >> (i.e. without my previously mentioned revert patch or any other extra
> >> >> patches).  Config attached.
> >> >
> >> > OK, it looks like you have context-tracking enabled, so you might be
> >> > hitting a bug that Steven Rostedt found a few days ago.  Could you
> >> > please try out his fix below?
> >> 
> >> Thanks for the quick reply, but I'm afraid that patch had no effect on
> >> the warning I got. It's still there.
> >
> > Other than wondering whether powertop has issues similar to the bug
> > Steven Rostedt located, I must confess myself clueless.  Here are some
> > diagnostics I can suggest:
> >
> > 1.	Run in 32-bit mode.  This disables some of the new adaptive-ticks
> > 	functionality, so might give a probabilistic indication of where
> > 	the bug lies.
> >
> > 2.	The standard fallback of bisection.
> >
> > Would you be willing to do either of these?
> 
> Willing, yes. But it will take some time before I am able to do either
> unless I can recreate the problem in a virtual machine.  I assume that
> you by " 32-bit mode" mean a 32bit kernel?  I'm not exactly set up to
> run that on my laptop.  Bisection will be less work.
> 
> To be honest, I don't even know how old this thing is.  It could be
> totally unrelated to your recent changes for all I know. Running
> powertop is something I do once every 6 kernel releases or something
> like that...
> 
> I'll see what I can come up with.  Thanks for your attention.

And thank you for the testing and information!

							Thanx, Paul

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