Re: [PATCH V3 2/2] arm64: perf: add support for percpu pmu interrupt

[Marc Zyngier <marc.zyngier@arm.com>]

Vinayak,

On 2013-11-18 13:22, Vinayak Kale wrote:
> Add support for irq registration when pmu interrupt is percpu.
>
> Signed-off-by: Vinayak Kale <vkale@apm.com>
> Signed-off-by: Tuan Phan <tphan@apm.com>
> ---
>  arch/arm64/kernel/perf_event.c |  102
> +++++++++++++++++++++++++++++-----------
>  1 file changed, 74 insertions(+), 28 deletions(-)
>
> diff --git a/arch/arm64/kernel/perf_event.c 
> b/arch/arm64/kernel/perf_event.c
> index cea1594..23475f6 100644
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -22,6 +22,7 @@
>
>  #include <linux/bitmap.h>
>  #include <linux/interrupt.h>
> +#include <linux/irq.h>
>  #include <linux/kernel.h>
>  #include <linux/export.h>
>  #include <linux/perf_event.h>
> @@ -363,22 +364,51 @@ validate_group(struct perf_event *event)
>  }
>
>  static void
> +armpmu_disable_percpu_irq(void *data)
> +{
> +	struct arm_pmu *armpmu = data;
> +	struct platform_device *pmu_device = armpmu->plat_device;
> +	int irq = platform_get_irq(pmu_device, 0);
> +
> +	cpumask_test_and_clear_cpu(smp_processor_id(), 
> &armpmu->active_irqs);
> +	disable_percpu_irq(irq);
> +}
> +
> +static void
>  armpmu_release_hardware(struct arm_pmu *armpmu)
>  {
>  	int i, irq, irqs;
>  	struct platform_device *pmu_device = armpmu->plat_device;
>
> -	irqs = min(pmu_device->num_resources, num_possible_cpus());
> +	irq = platform_get_irq(pmu_device, 0);
>
> -	for (i = 0; i < irqs; ++i) {
> -		if (!cpumask_test_and_clear_cpu(i, &armpmu->active_irqs))
> -			continue;
> -		irq = platform_get_irq(pmu_device, i);
> -		if (irq >= 0)
> -			free_irq(irq, armpmu);
> +	if (irq_to_desc(irq) && irq_is_percpu(irq)) {

Why do you need to check the irq_desc here? It really looks like a 
misuse of the API.
Instead, you should check the value of irq itself (it should be 
strictly positive).

> +		on_each_cpu(armpmu_disable_percpu_irq, armpmu, 1);
> +		free_percpu_irq(irq, &cpu_hw_events);
> +	} else {
> +		irqs = min(pmu_device->num_resources, num_possible_cpus());
> +
> +		for (i = 0; i < irqs; ++i) {
> +			if (!cpumask_test_and_clear_cpu(i, &armpmu->active_irqs))
> +				continue;
> +			irq = platform_get_irq(pmu_device, i);
> +			if (irq >= 0)

irq == 0 means "no-irq". You should handle it as an error case.

> +				free_irq(irq, armpmu);
> +		}
>  	}
>  }
>
> +static void
> +armpmu_enable_percpu_irq(void *data)
> +{
> +	struct arm_pmu *armpmu = data;
> +	struct platform_device *pmu_device = armpmu->plat_device;
> +	int irq = platform_get_irq(pmu_device, 0);
> +
> +	enable_percpu_irq(irq, 0);
> +	cpumask_set_cpu(smp_processor_id(), &armpmu->active_irqs);
> +}
> +
>  static int
>  armpmu_reserve_hardware(struct arm_pmu *armpmu)
>  {
> @@ -396,34 +426,50 @@ armpmu_reserve_hardware(struct arm_pmu *armpmu)
>  		return -ENODEV;
>  	}
>
> -	for (i = 0; i < irqs; ++i) {
> -		err = 0;
> -		irq = platform_get_irq(pmu_device, i);
> -		if (irq < 0)
> -			continue;
> +	irq = platform_get_irq(pmu_device, 0);
>
> -		/*
> -		 * If we have a single PMU interrupt that we can't shift,
> -		 * assume that we're running on a uniprocessor machine and
> -		 * continue. Otherwise, continue without this interrupt.
> -		 */
> -		if (irq_set_affinity(irq, cpumask_of(i)) && irqs > 1) {
> -			pr_warning("unable to set irq affinity (irq=%d, cpu=%u)\n",
> -				    irq, i);
> -			continue;
> -		}
> +	if (irq_to_desc(irq) && irq_is_percpu(irq)) {

Same comment about irq_to_desc.

> +		err = request_percpu_irq(irq, armpmu->handle_irq,
> +				"arm-pmu", &cpu_hw_events);
>
> -		err = request_irq(irq, armpmu->handle_irq,
> -				  IRQF_NOBALANCING,
> -				  "arm-pmu", armpmu);
>  		if (err) {
> -			pr_err("unable to request IRQ%d for ARM PMU counters\n",
> -				irq);
> +			pr_err("unable to request percpu IRQ%d for ARM PMU counters\n",
> +					irq);
>  			armpmu_release_hardware(armpmu);
>  			return err;
>  		}
>
> -		cpumask_set_cpu(i, &armpmu->active_irqs);
> +		on_each_cpu(armpmu_enable_percpu_irq, armpmu, 1);
> +	} else {
> +		for (i = 0; i < irqs; ++i) {
> +			err = 0;
> +			irq = platform_get_irq(pmu_device, i);
> +			if (irq < 0)

Same comment about irq == 0.

> +				continue;
> +
> +			/*
> +			 * If we have a single PMU interrupt that we can't shift,
> +			 * assume that we're running on a uniprocessor machine and
> +			 * continue. Otherwise, continue without this interrupt.
> +			 */
> +			if (irq_set_affinity(irq, cpumask_of(i)) && irqs > 1) {
> +				pr_warning("unable to set irq affinity (irq=%d, cpu=%u)\n",
> +						irq, i);
> +				continue;
> +			}
> +
> +			err = request_irq(irq, armpmu->handle_irq,
> +					IRQF_NOBALANCING,
> +					"arm-pmu", armpmu);
> +			if (err) {
> +				pr_err("unable to request IRQ%d for ARM PMU counters\n",
> +						irq);
> +				armpmu_release_hardware(armpmu);
> +				return err;
> +			}
> +
> +			cpumask_set_cpu(i, &armpmu->active_irqs);
> +		}
>  	}
>
>  	return 0;

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