Date: Tue, 2 Jan 2007 15:12:34 -0800
To: "Chen, Tim C" <tim.c.chen@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Steven Rostedt <rostedt@goodmis.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       "Bill Huey (hui)" <billh@gnuppy.monkey.org>
Subject: Re: [PATCH] lock stat for -rt 2.6.20-rc2-rt2 [was Re: 2.6.19-rt14 slowdown compared to 2.6.19]
Message-ID: <20070102231234.GA22627@gnuppy.monkey.org>
References: <20061229232618.GA11239@gnuppy.monkey.org> <9D2C22909C6E774EBFB8B5583AE5291C019FA2B5@fmsmsx414.amr.corp.intel.com>
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From: Bill Huey (hui) <billh@gnuppy.monkey.org>
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On Tue, Jan 02, 2007 at 02:51:05PM -0800, Chen, Tim C wrote:
> Bill,
> 
> I'm having some problem getting this patch to run stablely.  I'm
> encoutering errors like that in the trace that follow:
> 
> Thanks.
> Tim
> 
> Unable to handle kernel NULL pointer dereference at 0000000000000008

Yes, those are the reason why I have some aggressive asserts in the code
to try track down the problem. Try this:

http://mmlinux.sourceforge.net/public/patch-2.6.20-rc2-rt2.1.lock_stat.patch

It's got some cosmestic clean up in it to make it more Linux-ish instead
of me trying to reinvent some kind of Smalltalk system in the kernel. I'm
trying to address all of Ingo's complaints about the code so it's still a
work in progress, namely the style issues (I'd like help/suggestions on
that) and assert conventions.

It might the case that the lock isn't know to the lock stats code yet.
It's got some technical overlap with lockdep in that a lock might not be
known yet and is causing a crashing.

Try that patch and report back to me what happens.

bill

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