Re: [PATCH V4 2/2] arm64: perf: add support for percpu pmu interrupt

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

[dropped patches@apm.com]

Vinayak,

Please keep reviewers on CC, as it makes easier to track the changes.

On 20/11/13 11:13, 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 |  108 ++++++++++++++++++++++++++++++----------
>  1 file changed, 81 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index cea1594..de12ba8 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 +364,55 @@ 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());
> +	if (irqs < 1)
> +		return;
>  
> -	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);
> +	irq = platform_get_irq(pmu_device, 0);
> +	if (irq < 0)

So I'm going to sound like a stuck record: irq == 0 is not a valid IRQ
number, full stop. This is how we express the fact that there is no IRQ.

If you're touching that code, you might as well fix this buglet.

> +		return;
> +
> +	if (irq_is_percpu(irq)) {
> +		on_each_cpu(armpmu_disable_percpu_irq, armpmu, 1);
> +		free_percpu_irq(irq, &cpu_hw_events);
> +	} else {
> +		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)

Same here.

> +				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 +430,54 @@ 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 (irq < 0) {

And here.

> +		pr_err("failed to get an irq for PMU device\n");
> +		return -ENODEV;
> +	}
>  
> -		/*
> -		 * 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_is_percpu(irq)) {
> +		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)

And here.

> +				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;
> 

	M.
-- 
Jazz is not dead. It just smells funny...