linux-kernel - Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift

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Message-ID: <1290094707.2109.1524.camel@laptop>
Date:	Thu, 18 Nov 2010 16:38:27 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Don Zickus <dzickus@...hat.com>,
	Robert Richter <robert.richter@....com>, ying.huang@...el.com,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift

On Thu, 2010-11-18 at 14:17 +0100, Peter Zijlstra wrote:
> On Thu, 2010-11-18 at 06:47 -0600, Jason Wessel wrote:
> > More specifically
> > when another subsystem injects an NMI event the perf NMI code returns
> > NOTIFY_STOP. 
> 
> Not unconditionally, right? We only do so when the previous NMI was from
> the PMU and nobody claimed this one (NOTIFY_STOP from DIE_NMIUNKNOWN).
> 
> Or are you hitting the other one, where !handled but pmu_nmi.handled >
> 1 ?

I'm just thinking here, shouldn't we do that (!handle && pmu_nmi.handle
> 1) case from DIE_NMIUNKNOWN as well? and only ever return NOTIFY_STOP
when handled != 0?

That way all NMIs at least traverse the regular DIE_NMI chain once and
we only kill redundant NMIs
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