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

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Date:	Wed, 29 Sep 2010 14:53:01 +0200
From:	Robert Richter <robert.richter@....com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	"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>,
	"gorcunov@...il.com" <gorcunov@...il.com>,
	"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>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:perf/urgent] perf, x86: Catch spurious interrupts after
 disabling counters

Stephane,

On 29.09.10 08:26:41, Stephane Eranian wrote:
> You've applied the fix only to the generic X86 interrupt handler
> which is currently used by AMD64 processors.

(... and P4).

> It seems to me that this "in-flight interrupt after disable" problem
> may also happen on Intel and should therefore also be added
> to intel_pmu_handle_irq(). Don't you think so?

It only happens if the active_mask is used for checking single
counters for overflows.

Systems with Intel Architectural Perfmon use the status mask msr to
determine which counter overflowed. In intel_pmu_handle_irq() the
handled counter is incremented in this case even if the counter is not
active, so everything should be fine here.

-Robert

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

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