linux-kernel - Re: [PATCH v0 01/71] perf: Disable all pmus on unthrottling and rescheduling

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Date:	Wed, 11 Dec 2013 12:53:36 -0800
From:	Andi Kleen <ak@...ux.intel.com>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v0 01/71] perf: Disable all pmus on unthrottling and
 rescheduling

On Wed, Dec 11, 2013 at 02:36:13PM +0200, Alexander Shishkin wrote:
> Currently, only one pmu in a context gets disabled during unthrottling
> and event_sched_{out,in}, however, events in one context may belong to
> different pmus, which results in pmus being reprogrammed while they are
> still enabled. This patch temporarily disables pmus that correspond to
> each event in the context while these events are being modified.

This is a generic bug fix and should be merged independent of the PT code.
This affects any setup using multiple PMUs at the same time.

Reviewed-by: Andi Kleen <ak@...ux.intel.com>

-Andi
> 
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> ---
>  kernel/events/core.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 403b781..d656cd6 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1396,6 +1396,9 @@ event_sched_out(struct perf_event *event,
>  	if (event->state != PERF_EVENT_STATE_ACTIVE)
>  		return;
>  
> +	if (event->pmu != ctx->pmu)
> +		perf_pmu_disable(event->pmu);
> +
>  	event->state = PERF_EVENT_STATE_INACTIVE;
>  	if (event->pending_disable) {
>  		event->pending_disable = 0;
> @@ -1412,6 +1415,9 @@ event_sched_out(struct perf_event *event,
>  		ctx->nr_freq--;
>  	if (event->attr.exclusive || !cpuctx->active_oncpu)
>  		cpuctx->exclusive = 0;
> +
> +	if (event->pmu != ctx->pmu)
> +		perf_pmu_enable(event->pmu);
>  }
>  
>  static void
> @@ -1652,6 +1658,7 @@ event_sched_in(struct perf_event *event,
>  		 struct perf_event_context *ctx)
>  {
>  	u64 tstamp = perf_event_time(event);
> +	int ret = 0;
>  
>  	if (event->state <= PERF_EVENT_STATE_OFF)
>  		return 0;
> @@ -1674,10 +1681,14 @@ event_sched_in(struct perf_event *event,
>  	 */
>  	smp_wmb();
>  
> +	if (event->pmu != ctx->pmu)
> +		perf_pmu_disable(event->pmu);
> +
>  	if (event->pmu->add(event, PERF_EF_START)) {
>  		event->state = PERF_EVENT_STATE_INACTIVE;
>  		event->oncpu = -1;
> -		return -EAGAIN;
> +		ret = -EAGAIN;
> +		goto out;
>  	}
>  
>  	event->tstamp_running += tstamp - event->tstamp_stopped;
> @@ -1693,7 +1704,11 @@ event_sched_in(struct perf_event *event,
>  	if (event->attr.exclusive)
>  		cpuctx->exclusive = 1;
>  
> -	return 0;
> +out:
> +	if (event->pmu != ctx->pmu)
> +		perf_pmu_enable(event->pmu);
> +
> +	return ret;
>  }
>  
>  static int
> @@ -2743,6 +2758,9 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
>  		if (!event_filter_match(event))
>  			continue;
>  
> +		if (ctx->pmu != event->pmu)
> +			perf_pmu_disable(event->pmu);
> +
>  		hwc = &event->hw;
>  
>  		if (hwc->interrupts == MAX_INTERRUPTS) {
> @@ -2752,7 +2770,7 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
>  		}
>  
>  		if (!event->attr.freq || !event->attr.sample_freq)
> -			continue;
> +			goto next;
>  
>  		/*
>  		 * stop the event and update event->count
> @@ -2774,6 +2792,9 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
>  			perf_adjust_period(event, period, delta, false);
>  
>  		event->pmu->start(event, delta > 0 ? PERF_EF_RELOAD : 0);
> +	next:
> +		if (ctx->pmu != event->pmu)
> +			perf_pmu_enable(event->pmu);
>  	}
>  
>  	perf_pmu_enable(ctx->pmu);
> -- 
> 1.8.5.1
> 

-- 
ak@...ux.intel.com -- Speaking for myself only
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