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Commit a37e5be2 authored by Raghavendra Rao Ananta's avatar Raghavendra Rao Ananta
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perf: Cancel the mux hrtimer during CPU hotplug to avoid migration 



The current design of hrtimers migrates the pinned timers to a
different CPU upon its hotplug. However, perf-core needs to
maintain the mux-hrtimers on a per CPU basis. That is, each
hrtimer carries the context for that particular CPU and would
lose this context if it gets migrated to a different CPU. As a
result, cancel the hrtimer for the CPU that's about to go down
and restart it (if required) when the perf-events are being created.

Change-Id: I7a1d0456208855e3a99a7d49e59c6dae811d146e
Signed-off-by: default avatarRaghavendra Rao Ananta <rananta@codeaurora.org>
parent 77257e46

kernel/events/core.c

+11 −0
Original line number Diff line number Diff line
@@ -11532,6 +11532,7 @@ static void perf_event_exit_cpu_context(int cpu) 
	struct perf_cpu_context *cpuctx;

	struct perf_event_context *ctx;

	struct perf_event *event, *event_tmp;

	unsigned long flags;

	struct pmu *pmu;



	mutex_lock(&pmus_lock);
@@ -11539,6 +11540,16 @@ static void perf_event_exit_cpu_context(int cpu) 
	list_for_each_entry(pmu, &pmus, entry) {

		cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);

		ctx = &cpuctx->ctx;



		/* Cancel the mux hrtimer to avoid CPU migration */

		if (pmu->task_ctx_nr != perf_sw_context) {

			raw_spin_lock_irqsave(&cpuctx->hrtimer_lock, flags);

			hrtimer_cancel(&cpuctx->hrtimer);

			cpuctx->hrtimer_active = 0;

			raw_spin_unlock_irqrestore(&cpuctx->hrtimer_lock,

							flags);

		}



		mutex_lock(&ctx->mutex);

		list_for_each_entry_safe(event, event_tmp, &ctx->event_list,

								event_entry) {