linux-kernel - Re: [tip:perf/urgent] perf, x86: Catch spurious interrupts after disabling counters

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Message-ID: <20100929163118.GN13563@erda.amd.com>
Date:	Wed, 29 Sep 2010 18:31:18 +0200
From:	Robert Richter <robert.richter@....com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	Cyrill Gorcunov <gorcunov@...il.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"ying.huang@...el.com" <ying.huang@...el.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"ming.m.lin@...el.com" <ming.m.lin@...el.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [tip:perf/urgent] perf, x86: Catch spurious interrupts after
 disabling counters

On 29.09.10 11:33:07, Stephane Eranian wrote:
> There is something else bothering me with cpuc->running.
> 
> It is not reset outside of the interrupt handler. So what if
> event scheduling shuffles things around and an event is
> moved somewhere else. Don't you need to clear the
> cpuc->running[idx] for the old counter index?

We can clear it only in the NMI handler, because the next NMI after
stopping a counter must mark the counter as handled. This may cause
some false positives, but it is the best we can get.

-Robert

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

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