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Commit 9768e7af authored by Patrick Fay's avatar Patrick Fay
Browse files

Perf: arm: disable perf_event_read during hotplug 



core.c should not allow perf_event_read access during hotplug.
DCVS may try to read events during hotplug startup or
shutdown. Set a flag to not allow access during hotplug.

Change-Id: I3c5f1f532d451a096d2d3ee976e0a15fca826e8b
Signed-off-by: default avatarPatrick Fay <pfay@codeaurora.org>
parent dc62e315

arch/arm64/kernel/perf_event.c

+48 −3
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ 
#include <linux/perf/arm_pmu.h>

#include <linux/platform_device.h>



static DEFINE_PER_CPU(bool, is_hotplugging);



/*

 * ARMv8 PMUv3 Performance Events handling code.

 * Common event types (some are defined in asm/perf_event.h).
@@ -982,6 +984,9 @@ static void armv8pmu_idle_update(struct arm_pmu *cpu_pmu) 
	if (!cpu_pmu)

		return;



	if (__this_cpu_read(is_hotplugging))

		return;



	hw_events = this_cpu_ptr(cpu_pmu->hw_events);



	if (!hw_events)
@@ -1031,14 +1036,13 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu) 


	pmu_idle_nb->cpu_pmu = cpu_pmu;

	pmu_idle_nb->perf_cpu_idle_nb.notifier_call = perf_cpu_idle_notifier;

	idle_notifier_register(&pmu_idle_nb->perf_cpu_idle_nb);



	ret = smp_call_function_any(&cpu_pmu->supported_cpus,

				    __armv8pmu_probe_pmu,

				    cpu_pmu, 1);



	if (ret)

		idle_notifier_unregister(&pmu_idle_nb->perf_cpu_idle_nb);

	if (!ret)

		idle_notifier_register(&pmu_idle_nb->perf_cpu_idle_nb);



	return ret;

}
@@ -1140,6 +1144,37 @@ static const struct of_device_id armv8_pmu_of_device_ids[] = { 
	{},

};



#ifdef CONFIG_HOTPLUG_CPU

static int perf_event_hotplug_coming_up(unsigned int cpu)

{

	per_cpu(is_hotplugging, cpu) = false;

	return 0;

}



static int perf_event_hotplug_going_down(unsigned int cpu)

{

	per_cpu(is_hotplugging, cpu) = true;

	return 0;

}



static int perf_event_cpu_hp_init(void)

{

	int ret;



	ret = cpuhp_setup_state_nocalls(CPUHP_AP_NOTIFY_ONLINE,

				"PERF_EVENT/CPUHP_AP_NOTIFY_ONLINE",

				perf_event_hotplug_coming_up,

				perf_event_hotplug_going_down);

	if (ret)

		pr_err("CPU hotplug notifier for perf_event.c could not be registered: %d\n",

		       ret);



	return ret;

}

#else

static int perf_event_cpu_hp_init(void) { return 0; }

#endif



/*

 * Non DT systems have their micro/arch events probed at run-time.

 * A fairly complete list of generic events are provided and ones that
@@ -1152,6 +1187,16 @@ static const struct pmu_probe_info armv8_pmu_probe_table[] = { 


static int armv8_pmu_device_probe(struct platform_device *pdev)

{

	int ret, cpu;



	for_each_possible_cpu(cpu)

		per_cpu(is_hotplugging, cpu) = false;



	ret = perf_event_cpu_hp_init();



	if (ret)

		return ret;



	if (acpi_disabled)

		return arm_pmu_device_probe(pdev, armv8_pmu_of_device_ids,

					    NULL);

kernel/events/core.c

+41 −45
Original line number Diff line number Diff line
@@ -373,6 +373,7 @@ static DEFINE_PER_CPU(atomic_t, perf_cgroup_events); 
static DEFINE_PER_CPU(int, perf_sched_cb_usages);

static DEFINE_PER_CPU(struct pmu_event_list, pmu_sb_events);

static DEFINE_PER_CPU(bool, is_idle);

static DEFINE_PER_CPU(bool, is_hotplugging);



static atomic_t nr_mmap_events __read_mostly;

static atomic_t nr_comm_events __read_mostly;
@@ -3495,6 +3496,9 @@ static void __perf_event_read(void *info) 
	struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

	struct pmu *pmu = event->pmu;



	if (__this_cpu_read(is_hotplugging))

		return;



	/*

	 * If this is a task context, we need to check whether it is

	 * the current task context of this cpu.  If not it has been
@@ -3619,7 +3623,8 @@ static int perf_event_read(struct perf_event *event, bool group) 
			return 0;

		if (cpu_isolated(event_cpu) ||

			(event->attr.exclude_idle &&

				per_cpu(is_idle, event_cpu)))

				per_cpu(is_idle, event_cpu)) ||

				per_cpu(is_hotplugging, event_cpu))

			active_event_skip_read = true;

	}
@@ -3649,7 +3654,8 @@ static int perf_event_read(struct perf_event *event, bool group) 
		preempt_enable();

		ret = data.ret;

	} else if (event->state == PERF_EVENT_STATE_INACTIVE ||

			active_event_skip_read) {

			(active_event_skip_read &&

			!per_cpu(is_hotplugging, event_cpu))) {

		struct perf_event_context *ctx = event->ctx;

		unsigned long flags;
@@ -10711,6 +10717,8 @@ static void __init perf_event_init_all_cpus(void) 
		raw_spin_lock_init(&per_cpu(pmu_sb_events.lock, cpu));



		INIT_LIST_HEAD(&per_cpu(sched_cb_list, cpu));

		per_cpu(is_hotplugging, cpu) = false;

		per_cpu(is_idle, cpu) = false;

	}

}
@@ -10734,19 +10742,10 @@ int perf_event_init_cpu(unsigned int cpu) 
static void

check_hotplug_start_event(struct perf_event *event)

{

	if (event->attr.type == PERF_TYPE_SOFTWARE) {

		switch (event->attr.config) {

		case PERF_COUNT_SW_CPU_CLOCK:

			cpu_clock_event_start(event, 0);

			break;

		case PERF_COUNT_SW_TASK_CLOCK:

			break;

		default:

			if (event->pmu->start)

	if (event->pmu->events_across_hotplug &&

	    event->attr.type == PERF_TYPE_SOFTWARE &&

	    event->pmu->start)

		event->pmu->start(event, 0);

			break;

		}

	}

}



static int perf_event_start_swevents(unsigned int cpu)
@@ -10767,6 +10766,7 @@ static int perf_event_start_swevents(unsigned int cpu) 
		mutex_unlock(&ctx->mutex);

	}

	srcu_read_unlock(&pmus_srcu, idx);

	per_cpu(is_hotplugging, cpu) = false;

	return 0;

}
@@ -10783,22 +10783,13 @@ check_hotplug_remove_from_context(struct perf_event *event, 
			   struct perf_cpu_context *cpuctx,

			   struct perf_event_context *ctx)

{

	if (!event->pmu->events_across_hotplug) {

	if (event->pmu->events_across_hotplug &&

	    event->attr.type == PERF_TYPE_SOFTWARE &&

	    event->pmu->stop)

		event->pmu->stop(event, PERF_EF_UPDATE);

	else if (!event->pmu->events_across_hotplug)

		__perf_remove_from_context(event, cpuctx,

			ctx, (void *)DETACH_GROUP);

	} else if (event->attr.type == PERF_TYPE_SOFTWARE) {

		switch (event->attr.config) {

		case PERF_COUNT_SW_CPU_CLOCK:

			cpu_clock_event_stop(event, 0);

			break;

		case PERF_COUNT_SW_TASK_CLOCK:

			break;

		default:

			if (event->pmu->stop)

				event->pmu->stop(event, 0);

			break;

		}

	}

}



static void __perf_event_exit_context(void *__info)
@@ -10837,6 +10828,7 @@ static void perf_event_exit_cpu_context(int cpu) { } 


int perf_event_exit_cpu(unsigned int cpu)

{

	per_cpu(is_hotplugging, cpu) = true;

	perf_event_exit_cpu_context(cpu);

	return 0;

}
@@ -10880,6 +10872,24 @@ static struct notifier_block perf_event_idle_nb = { 
	.notifier_call = event_idle_notif,

};



#ifdef CONFIG_HOTPLUG_CPU

static int perf_cpu_hp_init(void)

{

	int ret;



	ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ONLINE,

				"PERF/CORE/CPUHP_AP_PERF_ONLINE",

				perf_event_start_swevents,

				perf_event_exit_cpu);

	if (ret)

		pr_err("CPU hotplug notifier for perf core could not be registered: %d\n",

		       ret);



	return ret;

}

#else

static int perf_cpu_hp_init(void) { return 0; }

#endif



void __init perf_event_init(void)

{
@@ -10896,6 +10906,8 @@ void __init perf_event_init(void) 
	perf_event_init_cpu(smp_processor_id());

	idle_notifier_register(&perf_event_idle_nb);

	register_reboot_notifier(&perf_reboot_notifier);

	ret = perf_cpu_hp_init();

	WARN(ret, "core perf_cpu_hp_init() failed with: %d", ret);



	ret = init_hw_breakpoint();

	WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
@@ -10949,22 +10961,6 @@ static int __init perf_event_sysfs_init(void) 
}

device_initcall(perf_event_sysfs_init);



#ifdef CONFIG_HOTPLUG_CPU

static int perf_cpu_hp_init(void)

{

	int ret;



	ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ONLINE,

				"PERF/CORE/AP_PERF_ONLINE",

				perf_event_start_swevents,

				perf_event_exit_cpu);

	if (ret)

		pr_err("CPU hotplug notifier for perf core could not be registered: %d\n",

		       ret);

	return ret;

}

subsys_initcall(perf_cpu_hp_init);

#endif



#ifdef CONFIG_CGROUP_PERF

static struct cgroup_subsys_state *