linux-kernel - Re: [PATCH 00/12] perf: more fixes

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Date:	Thu, 17 Mar 2016 12:54:06 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Vince Weaver <vince@...ter.net>, mingo@...nel.org,
	alexander.shishkin@...ux.intel.com, eranian@...gle.com,
	linux-kernel@...r.kernel.org, dvyukov@...gle.com,
	andi@...stfloor.org, jolsa@...hat.com, panand@...hat.com,
	sasha.levin@...cle.com, oleg@...hat.com
Subject: Re: [PATCH 00/12] perf: more fixes

On Wed, Mar 16, 2016 at 11:59:33PM +0100, Peter Zijlstra wrote:
> On Tue, Mar 15, 2016 at 04:38:30PM +0100, Peter Zijlstra wrote:
> 
> > Running perf_fuzzer on that AMD box is still producing lots of fail, I
> > seen long strings of dazed and confused msgs, indicating we have a
> > 'spurious' NMI problem somewhere.
> > 
> > And occasionally it locks up..
> > 
> > So we're not there yet.
> 
> So the below appears to alleviate some of this; but the hangs are
> quicker now, so maybe I just made it worse.
> 
> ---
> Subject: perf, ibs: Fix race with IBS_STARTING state
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Wed Mar 16 23:55:21 CET 2016
> 
> While tracing the IBS bits I saw the NMI hitting between clearing
> IBS_STARTING and the actual MSR writes to disable the counter.
> 
> Since IBS_STARTING was cleared, the handler assumed these were spurious
> NMIs and because STOPPING wasn't set yet either, insta-triggered an
> "Unknown NMI".
> 
> Cure this by clearing IBS_STARTING after disabling the hardware.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Tested-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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