linux-kernel - Re: [PATCH] perf, x86: try to handle unknown nmis with running perfctrs

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Message-ID: <20100811123937.GB4879@redhat.com>
Date:	Wed, 11 Aug 2010 08:39:37 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Robert Richter <robert.richter@....com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] perf, x86: try to handle unknown nmis with running
 perfctrs

On Wed, Aug 11, 2010 at 04:44:55AM +0200, Frederic Weisbecker wrote:
> May be make it just a pending bit. I mean not something that can
> go further 1, because you can't have more than 1 pending anyway. I don't
> know how that could happen you get accidental perctr_skip > 1, may be
> expected pending NMIs that don't happen somehow, but better be paranoid with
> that, as it's about trying not to miss hardware errors.

I guess I was thinking about the SMI case where it drains the perfctr(s)
and then retriggers them but I guess even in that case the most you can
have is one extra NMI.  So yeah, you are probably right, I should have
used a flag instead of incrementing.

Cheers,
Don
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