Commit 37b502f1 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Ingo Molnar
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arm/perf: Fix hotplug state machine conversion 



Mark Rutland pointed out that this commit is incomplete:

  7d88eb69 ("arm/perf: Convert to hotplug state machine")

The problem is that:

 > We may have multiple PMUs (e.g. two in big.LITTLE systems), and
 > __oprofile_cpu_pmu only contains one of these. So this conversion is not
 > correct.
 >
 > We were relying on the notifier list implicitly containing a list of
 > those PMUs. It seems like we need an explicit list here.
 >
 > We keep __oprofile_cpu_pmu around for legacy 32-bit users of OProfile
 > (on non-hetereogeneous systems), and that's all that the variable should
 > be used for.

Introduce arm_pmu_list to correctly handle multiple PMUs in the system.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-tip-commits@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160719111733.GA22911@linutronix.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c76c15e6

drivers/perf/arm_pmu.c

+37 −16
Original line number Diff line number Diff line
@@ -685,6 +685,9 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler) 
	return 0;

}



static DEFINE_MUTEX(arm_pmu_mutex);

static LIST_HEAD(arm_pmu_list);



/*

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

 * When a CPU is hotplugged back in, since some hardware registers are
@@ -693,12 +696,17 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler) 
 */

static int arm_perf_starting_cpu(unsigned int cpu)

{

	if (!__oprofile_cpu_pmu)

		return 0;

	if (!cpumask_test_cpu(cpu, &__oprofile_cpu_pmu->supported_cpus))

		return 0;

	if (__oprofile_cpu_pmu->reset)

		__oprofile_cpu_pmu->reset(__oprofile_cpu_pmu);

	struct arm_pmu *pmu;



	mutex_lock(&arm_pmu_mutex);

	list_for_each_entry(pmu, &arm_pmu_list, entry) {



		if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))

			continue;

		if (pmu->reset)

			pmu->reset(pmu);

	}

	mutex_unlock(&arm_pmu_mutex);

	return 0;

}
@@ -810,11 +818,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) 
	if (!cpu_hw_events)

		return -ENOMEM;



	err = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_STARTING,

					"AP_PERF_ARM_STARTING",

					arm_perf_starting_cpu, NULL);

	if (err)

		goto out_hw_events;

	mutex_lock(&arm_pmu_mutex);

	list_add_tail(&cpu_pmu->entry, &arm_pmu_list);

	mutex_unlock(&arm_pmu_mutex);



	err = cpu_pm_pmu_register(cpu_pmu);

	if (err)
@@ -850,8 +856,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) 
	return 0;



out_unregister:

	cpuhp_remove_state_nocalls(CPUHP_AP_PERF_ARM_STARTING);

out_hw_events:

	mutex_lock(&arm_pmu_mutex);

	list_del(&cpu_pmu->entry);

	mutex_unlock(&arm_pmu_mutex);

	free_percpu(cpu_hw_events);

	return err;

}
@@ -859,7 +866,9 @@ out_hw_events: 
static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)

{

	cpu_pm_pmu_unregister(cpu_pmu);

	cpuhp_remove_state_nocalls(CPUHP_AP_PERF_ARM_STARTING);

	mutex_lock(&arm_pmu_mutex);

	list_del(&cpu_pmu->entry);

	mutex_unlock(&arm_pmu_mutex);

	free_percpu(cpu_pmu->hw_events);

}
@@ -1019,8 +1028,6 @@ int arm_pmu_device_probe(struct platform_device *pdev, 
	if (ret)

		goto out_destroy;



	WARN(__oprofile_cpu_pmu, "%s(): missing PMU strucure for CPU-hotplug\n",

	     __func__);

	if (!__oprofile_cpu_pmu)

		__oprofile_cpu_pmu = pmu;
@@ -1038,3 +1045,17 @@ out_free: 
	kfree(pmu);

	return ret;

}



static int arm_pmu_hp_init(void)

{

	int ret;



	ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_STARTING,

					"AP_PERF_ARM_STARTING",

					arm_perf_starting_cpu, NULL);

	if (ret)

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

		       ret);

	return ret;

}

subsys_initcall(arm_pmu_hp_init);

include/linux/perf/arm_pmu.h

+1 −0
Original line number Diff line number Diff line
@@ -109,6 +109,7 @@ struct arm_pmu { 
	DECLARE_BITMAP(pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);

	struct platform_device	*plat_device;

	struct pmu_hw_events	__percpu *hw_events;

	struct list_head	entry;

	struct notifier_block	cpu_pm_nb;

};

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