linux-kernel - Re: perf_fuzzer crash on pentium 4

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Date:	Thu, 8 May 2014 01:14:56 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Cyrill Gorcunov <gorcunov@...il.com>
cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, Don Zickus <dzickus@...hat.com>
Subject: Re: perf_fuzzer crash on pentium 4

On Thu, 8 May 2014, Cyrill Gorcunov wrote:

> > > The NMI issue is probably the only one that is p4 related, and I do get 
> > > the NMI warnings on other machines too, it's just the p4 is the only one 
> > > where it brings down the machine.
> > 
> > Vince, could you please provde more details on that? Is it possible
> > to somehow log which events were used by perf?
> 
> There were a bug in p4 pmu Don (CC'ed) fixed not that long ago but I fear
> not all corner cases might be covered yet.

I hit the NMI warnings somewhat often on Intel hardware (Haswell, Core2) 
but it usually doesn't make the system unusable like it does on p4.

I can try to get a trace, although I'm not sure it will be useful.  I 
spent a lot of time getting a reproducible test case for the same warnings 
on core2 and it was unclear what the proble was and it was never fixed.

The messages look like this:

[ 2944.203423] Uhhuh. NMI received for unknown reason 31 on CPU 0.
[ 2944.208006] Do you have a strange power saving mode enabled?
[ 2944.208006] Dazed and confused, but trying to continue
[ 2944.208006] Uhhuh. NMI received for unknown reason 21 on CPU 0.
[ 2944.208006] Do you have a strange power saving mode enabled?
[ 2944.208006] Dazed and confused, but trying to continue
[ 2944.208006] Uhhuh. NMI received for unknown reason 31 on CPU 0.
[ 2944.208006] Do you have a strange power saving mode enabled?
[ 2944.208006] Dazed and confused, but trying to continue

repeating forever, system is unusable.

Vince
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