linux-kernel - Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

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Message-ID: <20100819123926.GW26154@erda.amd.com>
Date:	Thu, 19 Aug 2010 14:39:26 +0200
From:	Robert Richter <robert.richter@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Don Zickus <dzickus@...hat.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"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 -v3] perf, x86: try to handle unknown nmis with running
 perfctrs

On 19.08.10 06:45:53, Peter Zijlstra wrote:
> I queued it with that part changed to:
> 
> +       this_nmi = percpu_read(irq_stat.__nmi_count);
> +       if ((handled > 1) ||
> +               /* the next nmi could be a back-to-back nmi */
> +           ((__get_cpu_var(nmi).marked == this_nmi) &&
> +            (__get_cpu_var(nmi).handled > 1))) {
> +               /*
> +                * We could have two subsequent back-to-back nmis: The
> +                * first handles more than one counter, the 2nd
> +                * handles only one counter and the 3rd handles no
> +                * counter.
> +                *
> +                * This is the 2nd nmi because the previous was
> +                * handling more than one counter. We will mark the
> +                * next (3rd) and then drop it if unhandled.
> +                */
> +               __get_cpu_var(nmi).marked       = this_nmi + 1;
> +               __get_cpu_var(nmi).handled      = handled;
> +       }
> 
>         return NOTIFY_STOP;
>  }

I am fine with this. Thanks Peter.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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