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Subject: Re: [RFC][PATCH 13/19] perf: Per cpu-context rotation timer
From: Peter Zijlstra <peterz@infradead.org>
To: paulus <paulus@samba.org>
Cc: stephane eranian <eranian@googlemail.com>,
        Robert Richter <robert.richter@amd.com>,
        Will Deacon <will.deacon@arm.com>, Paul Mundt <lethal@linux-sh.org>,
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        Yanmin <yanmin_zhang@linux.intel.com>,
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	 <20100907165011.939993481@chello.nl>
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Date: Tue, 07 Sep 2010 19:08:51 +0200
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On Tue, 2010-09-07 at 18:46 +0200, Peter Zijlstra wrote:
> +static enum hrtimer_restart perf_event_context_tick(struct hrtimer
> *timer)
>  {
> +       enum hrtimer_restart restart = HRTIMER_NORESTART;
>         struct perf_cpu_context *cpuctx;
>         struct perf_event_context *ctx;
>         int rotate = 0;
>  
> +       cpuctx = container_of(timer, struct perf_cpu_context, timer);
>  
> +       if (cpuctx->ctx.nr_events) {
> +               restart = HRTIMER_RESTART;
> +               if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
> +                       rotate = 1;
> +       }
>  
> +       ctx = current->perf_event_ctxp;
> +       if (ctx && ctx->nr_events) {
> +               restart = HRTIMER_RESTART;
> +               if (ctx->nr_events != ctx->nr_active)
> +                       rotate = 1;
> +       } 

Note to self, this is probably racy against pmu_rotate_start().