On Tue, Feb 19, 2013 at 8:24 PM, Jiri Olsa <jo...@redhat.com> wrote:
> On Mon, Feb 18, 2013 at 06:54:44PM +0100, Stephane Eranian wrote:
>
> SNIP
>
>> +perf_event_mux_interval_ms_store(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + struct pmu *pmu = dev_get_drvdata(dev);
>> + int timer, cpu, ret;
>> +
>> + ret = kstrtoint(buf, 0, &timer);
>> + if (ret)
>> + return ret;
>> +
>> + if (timer < 1)
>> + return -EINVAL;
>> +
>> + pmu->hrtimer_interval_ms = timer;
>> +
>> + /* update all cpuctx for this PMU */
>> + for_each_possible_cpu(cpu) {
>> + struct perf_cpu_context *cpuctx;
>> + cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
>> + cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
>> + }
>
> If we set the timer to some big value like few minutes,
> then run the meassurements and then set the value back to 1,
> we actually need to wait till the big timer is expired before
> the new value takes place.
>
> I think we need to cancel the possible running timer in here
> like in the atached patch, but maybe consider some locking.
>
I will fix that. Thanks for pointing this out.
> jirka
>
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 7c3f00f..ce9cd54 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6038,6 +6038,9 @@ perf_event_mux_interval_ms_store(struct device *dev,
> struct perf_cpu_context *cpuctx;
> cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
> cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
> +
> + if (hrtimer_active(&cpuctx->hrtimer))
> + hrtimer_cancel(&cpuctx->hrtimer);
> }
>
> return count;
--
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