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Commit fef52d93 authored by Sheetal Sahasrabudhe's avatar Sheetal Sahasrabudhe
Browse files

Perf: Fix hrtimer operation across hotplug 



Stop hrtimer associated with CPU clock event when
core goes down. Start the timer when core comes back up.
This is needed to ensure proper software timer operation
across hotplug.

Change-Id: I027bf2718d177fa31be2a7cfe7ef98f93cb4aeda
Signed-off-by: default avatarSheetal Sahasrabudhe <sheetals@codeaurora.org>
parent e7c6d026

arch/arm/mach-msm/perf_debug.c

+1 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ static char *descriptions = 
	"18 ARM: dts: msm: add perf-events support for msm8916\n"

	"19 Perf: Enable pmuv3 on 32 bit kernel\n"

	"20 msm: perf: set filter bits for cycle counter on krait\n"

	"21 Perf: Fix hrtimer operation across hotplug\n"

;



static ssize_t desc_read(struct file *fp, char __user *buf,

kernel/events/core.c

+47 −6
Original line number Diff line number Diff line
@@ -7471,6 +7471,17 @@ static void __perf_event_exit_context(void *__info) 
	rcu_read_unlock();

}



static void __perf_event_stop_swclock(void *__info)

{

	struct perf_event_context *ctx = __info;

	struct perf_event *event, *tmp;



	list_for_each_entry_safe(event, tmp, &ctx->event_list, event_entry) {

		if (event->attr.config == PERF_COUNT_SW_CPU_CLOCK)

			cpu_clock_event_stop(event, 0);

	}

}



static void perf_event_exit_cpu_context(int cpu)

{

	struct perf_event_context *ctx;
@@ -7479,20 +7490,45 @@ static void perf_event_exit_cpu_context(int cpu) 


	idx = srcu_read_lock(&pmus_srcu);

	list_for_each_entry_rcu(pmu, &pmus, entry) {

		ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;

		mutex_lock(&ctx->mutex);

		/*

		 * If keeping events across hotplugging is supported, do not

		 * remove the event list, but keep it alive across CPU hotplug.

		 * The context is exited via an fd close path when userspace

		 * is done and the target CPU is online.

		 * is done and the target CPU is online. If software clock

		 * event is active, then stop hrtimer associated with it.

		 * Start the timer when the CPU comes back online.

		 */

		if (!pmu->events_across_hotplug) {

			ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;



			mutex_lock(&ctx->mutex);

		if (!pmu->events_across_hotplug)

			smp_call_function_single(cpu, __perf_event_exit_context,

						 ctx, 1);

		else

			smp_call_function_single(cpu, __perf_event_stop_swclock,

						 ctx, 1);

		mutex_unlock(&ctx->mutex);

	}

	srcu_read_unlock(&pmus_srcu, idx);

}



static void perf_event_start_swclock(int cpu)

{

	struct perf_event_context *ctx;

	struct pmu *pmu;

	int idx;

	struct perf_event *event, *tmp;



	idx = srcu_read_lock(&pmus_srcu);

	list_for_each_entry_rcu(pmu, &pmus, entry) {

		if (pmu->events_across_hotplug) {

			ctx = &per_cpu_ptr(pmu->pmu_cpu_context, cpu)->ctx;

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

							event_entry) {

				if (event->attr.config ==

						PERF_COUNT_SW_CPU_CLOCK)

					cpu_clock_event_start(event, 0);

			}

		}

	}

	srcu_read_unlock(&pmus_srcu, idx);

}
@@ -7509,6 +7545,7 @@ static void perf_event_exit_cpu(int cpu) 
}

#else

static inline void perf_event_exit_cpu(int cpu) { }

static inline void perf_event_start_swclock(int cpu) { }

#endif



static int
@@ -7548,6 +7585,10 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) 
		perf_event_exit_cpu(cpu);

		break;



	case CPU_STARTING:

		perf_event_start_swclock(cpu);

		break;



	default:

		break;

	}