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Commit af66abfe authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon
Browse files

arm: perf: fold hotplug notifier into arm_pmu 



Handling multiple PMUs using a single hotplug notifier requires a list
of PMUs to be maintained, with synchronisation in the probe, remove, and
notify paths. This is error-prone and makes the code much harder to
maintain.

Instead of using a single notifier, we can dynamically allocate a
notifier block per-PMU. The end result is the same, but the list of PMUs
is implicit in the hotplug notifier list rather than within a perf-local
data structure, which makes the code far easier to handle.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Reviewed-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent abdf655a

arch/arm/include/asm/pmu.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -116,6 +116,7 @@ struct arm_pmu { 
	u64		max_period;

	u64		max_period;

	struct platform_device	*plat_device;

	struct platform_device	*plat_device;

	struct pmu_hw_events	__percpu *hw_events;

	struct pmu_hw_events	__percpu *hw_events;

	struct notifier_block	hotplug_nb;

};

};





#define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu))

#define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu))

arch/arm/kernel/perf_event_cpu.c

+34 −35
Original line number Original line Diff line number Diff line
@@ -160,8 +160,31 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler) 
	return 0;

	return 0;

}

}





/*

 * PMU hardware loses all context when a CPU goes offline.

 * When a CPU is hotplugged back in, since some hardware registers are

 * UNKNOWN at reset, the PMU must be explicitly reset to avoid reading

 * junk values out of them.

 */

static int cpu_pmu_notify(struct notifier_block *b, unsigned long action,

			  void *hcpu)

{

	struct arm_pmu *pmu = container_of(b, struct arm_pmu, hotplug_nb);



	if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)

		return NOTIFY_DONE;



	if (pmu->reset)

		pmu->reset(pmu);

	else

		return NOTIFY_DONE;



	return NOTIFY_OK;

}



static int cpu_pmu_init(struct arm_pmu *cpu_pmu)

static int cpu_pmu_init(struct arm_pmu *cpu_pmu)

{

{

	int err;

	int cpu;

	int cpu;

	struct pmu_hw_events __percpu *cpu_hw_events;

	struct pmu_hw_events __percpu *cpu_hw_events;
@@ -169,6 +192,11 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) 
	if (!cpu_hw_events)

	if (!cpu_hw_events)

		return -ENOMEM;

		return -ENOMEM;





	cpu_pmu->hotplug_nb.notifier_call = cpu_pmu_notify;

	err = register_cpu_notifier(&cpu_pmu->hotplug_nb);

	if (err)

		goto out_hw_events;



	for_each_possible_cpu(cpu) {

	for_each_possible_cpu(cpu) {

		struct pmu_hw_events *events = per_cpu_ptr(cpu_hw_events, cpu);

		struct pmu_hw_events *events = per_cpu_ptr(cpu_hw_events, cpu);

		raw_spin_lock_init(&events->pmu_lock);

		raw_spin_lock_init(&events->pmu_lock);
@@ -188,37 +216,18 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) 
		cpu_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;

		cpu_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;





	return 0;

	return 0;



out_hw_events:

	free_percpu(cpu_hw_events);

	return err;

}

}





static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)

static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)

{

{

	unregister_cpu_notifier(&cpu_pmu->hotplug_nb);

	free_percpu(cpu_pmu->hw_events);

	free_percpu(cpu_pmu->hw_events);

}

}





/*

 * PMU hardware loses all context when a CPU goes offline.

 * When a CPU is hotplugged back in, since some hardware registers are

 * UNKNOWN at reset, the PMU must be explicitly reset to avoid reading

 * junk values out of them.

 */

static int cpu_pmu_notify(struct notifier_block *b, unsigned long action,

			  void *hcpu)

{

	if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)

		return NOTIFY_DONE;



	if (cpu_pmu && cpu_pmu->reset)

		cpu_pmu->reset(cpu_pmu);

	else

		return NOTIFY_DONE;



	return NOTIFY_OK;

}



static struct notifier_block cpu_pmu_hotplug_notifier = {

	.notifier_call = cpu_pmu_notify,

};



/*

/*

 * PMU platform driver and devicetree bindings.

 * PMU platform driver and devicetree bindings.

 */

 */
@@ -344,16 +353,6 @@ static struct platform_driver cpu_pmu_driver = { 




static int __init register_pmu_driver(void)

static int __init register_pmu_driver(void)

{

{

	int err;

	return platform_driver_register(&cpu_pmu_driver);



	err = register_cpu_notifier(&cpu_pmu_hotplug_notifier);

	if (err)

		return err;



	err = platform_driver_register(&cpu_pmu_driver);

	if (err)

		unregister_cpu_notifier(&cpu_pmu_hotplug_notifier);



	return err;

}

}

device_initcall(register_pmu_driver);
 
device_initcall(register_pmu_driver);