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Commit fd64280e authored by Neil Leeder's avatar Neil Leeder
Browse files

Perf: arm64: fix disable of pmu irq during hotplug 



PMU irq is disabled when a cpu is hotplugged off
and perf is running. Using cpu_pmu->active_events
to determine if the pmu is running left a window
where it is decremented to 0 in hw_perf_event_destroy,
and then armpmu_release_hardware is called. If a cpu
is hotplugged off in this window it may not disable
its irq. Use a separate flag which is not cleared
until after the irq is released by all online cpus.

The variable needs to be tristate because of the possibility
of a cpu being hotplugged in during this window. In that
case it should not enable its irq when the pmu is being
shut down. Having the GOING_DOWN state allows correct
behavior for cpus both going down and coming up.

Change-Id: I934ba5dec34e681ce8defd7fa7e311b4a2a92c1a
Signed-off-by: default avatarNeil Leeder <nleeder@codeaurora.org>
parent 3311f658

arch/arm64/include/asm/pmu.h

+7 −0
Original line number Diff line number Diff line
@@ -21,6 +21,12 @@ 


#ifdef CONFIG_HW_PERF_EVENTS



enum arm_pmu_state {

	ARM_PMU_STATE_OFF       = 0,

	ARM_PMU_STATE_GOING_DOWN,

	ARM_PMU_STATE_RUNNING,

};



/* The events for a given PMU register set. */

struct pmu_hw_events {

	/*
@@ -64,6 +70,7 @@ struct arm_pmu { 
	void			(*free_irq)(struct arm_pmu *);

	int			(*map_event)(struct perf_event *event);

	int			num_events;

	int			pmu_state;

	atomic_t		active_events;

	struct mutex		reserve_mutex;

	u64			max_period;

arch/arm64/kernel/perf_debug.c

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ static char *descriptions = 
	" 9 Perf: arm64: make request irq pmu-dependent\n"

	"10 Perf: arm64: tracectr: initialize counts after hotplug\n"

	"11 Perf: arm64: Refine disable/enable in tracecounters\n"

	"12 Perf: arm64: fix disable of pmu irq during hotplug\n"

;



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

arch/arm64/kernel/perf_event.c

+12 −4
Original line number Diff line number Diff line
@@ -440,6 +440,9 @@ armpmu_reserve_hardware(struct arm_pmu *armpmu) 
		armpmu_release_hardware(armpmu);

		return err;

	}



	armpmu->pmu_state = ARM_PMU_STATE_RUNNING;



	return 0;

}
@@ -1146,6 +1149,12 @@ static void armv8pmu_free_irq(struct arm_pmu *cpu_pmu) 
	if (irq <= 0)

		return;



	/*

	 * If a cpu comes online during this function, do not enable its irq.

	 * If a cpu goes offline, it should disable its irq.

	 */

	cpu_pmu->pmu_state = ARM_PMU_STATE_GOING_DOWN;



	if (irq_is_percpu(irq)) {

		if (msm_pmu_use_irq) {

			on_each_cpu(armpmu_disable_percpu_irq, &irq, 1);
@@ -1161,6 +1170,7 @@ static void armv8pmu_free_irq(struct arm_pmu *cpu_pmu) 
				free_irq(irq, cpu_pmu);

		}

	}

	cpu_pmu->pmu_state = ARM_PMU_STATE_OFF;

}



irqreturn_t armv8pmu_handle_irq(int irq_num, void *dev)
@@ -1465,7 +1475,6 @@ static int __cpuinit cpu_pmu_notify(struct notifier_block *b, 
	struct pmu *pmu;

	u64 lcpu = (u64)hcpu;

	int cpu = (int)lcpu;

	int perf_running;

	unsigned long masked_action = action & ~CPU_TASKS_FROZEN;

	int ret = NOTIFY_DONE;
@@ -1479,13 +1488,12 @@ static int __cpuinit cpu_pmu_notify(struct notifier_block *b, 
	if (!cpu_pmu)

		return ret;



	perf_running = atomic_read(&cpu_pmu->active_events);

	switch (masked_action) {

	case CPU_DOWN_PREPARE:

		if (cpu_pmu->save_pm_registers)

			smp_call_function_single(cpu,

				cpu_pmu->save_pm_registers, hcpu, 1);

		if (perf_running) {

		if (cpu_pmu->pmu_state != ARM_PMU_STATE_OFF) {

			if (cpu_has_active_perf(cpu))

				smp_call_function_single(cpu,

					armpmu_update_counters, NULL, 1);
@@ -1504,7 +1512,7 @@ static int __cpuinit cpu_pmu_notify(struct notifier_block *b, 
			cpu_pmu->reset(NULL);

		if (cpu_pmu->restore_pm_registers)

			cpu_pmu->restore_pm_registers(hcpu);

		if (perf_running) {

		if (cpu_pmu->pmu_state == ARM_PMU_STATE_RUNNING) {

			/* Arm the PMU IRQ before appearing. */

			if (msm_pmu_use_irq && cpu_pmu->plat_device) {

				irq = platform_get_irq(cpu_pmu->plat_device, 0);