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Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Thu, 21 Aug 2008 07:37:51 +1000
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Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
	linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>, linuxppc-dev@ozlabs.org,
	Steven Rostedt <srostedt@redhat.com>, Alan Modra <amodra@au1.ibm.com>,
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	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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> Hmm... so whats now?
> 
> Is there a way to prove this scenario is indeed the one that caused the 
> opps?

I've verified in sim that the crash in do_lookup() I was seeing (similar
backtrace) was indeed caused by an interrupt coming between those two
instructions and clobbering the saved GPRs.

So I think it's very likely our problem.

Ben.