linux-kernel - Re: [RFC][PATCH 13/13] perf: Rework the PMU methods

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Message-ID: <20100710133647.GA5306@nowhere>
Date:	Sat, 10 Jul 2010 15:36:52 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	paulus <paulus@...ba.org>,
	stephane eranian <eranian@...glemail.com>,
	Robert Richter <robert.richter@....com>,
	Will Deacon <will.deacon@....com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Yanmin <yanmin_zhang@...ux.intel.com>,
	Deng-Cheng Zhu <dengcheng.zhu@...il.com>,
	David Miller <davem@...emloft.net>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 13/13] perf: Rework the PMU methods

On Fri, Jul 09, 2010 at 10:21:30AM +0200, Peter Zijlstra wrote:
> -static void x86_pmu_pmu_enable(struct pmu *pmu)
> +static void x86_pmu_enable(struct pmu *pmu)
>  {
>  	struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
>  	struct perf_event *event;
> @@ -839,7 +839,14 @@ static void x86_pmu_pmu_enable(struct pm
>  			    match_prev_assignment(hwc, cpuc, i))
>  				continue;
>  
> -			x86_pmu_stop(event);
> +			/*
> +			 * Ensure we don't accidentally enable a stopped
> +			 * counter simply because we rescheduled.
> +			 */
> +			if (hwc->state & PERF_HES_STOPPED)
> +				hwc->state |= PERF_HES_ARCH;



So, if I understood well, this is to avoid enabling an event from perf_pmu_enable()
while the event was already stopped.

Looks good but why this ARCH name then? This should be a kind of PERF_HES_ONCPU
or so.

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