[PATCH] ARM: perf: ensure the cpu is available to scheduler when set irq affinity

[PATCH] ARM: perf: ensure the cpu is available to scheduler when set irq affinity

[roy.qing.li]

From: Li RongQing <roy.qing.li@gmail.com> 

when there are 4 cpus, but only one is available to schedule, the warning
will be generated when run the below command:
    # perf record -g -e cpu-clock -- find / -name "*.ko"
    CPU PMU: unable to set irq affinity (irq=28, cpu=1)
    CPU PMU: unable to set irq affinity (irq=29, cpu=2)
    CPU PMU: unable to set irq affinity (irq=30, cpu=3)

so ensure the cpu is available to scheduler when set irq affinity

Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
---
 drivers/perf/arm_pmu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 2365a32..9401aa8 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -619,6 +619,9 @@ static void cpu_pmu_free_irq(struct arm_pmu *cpu_pmu)
 			if (cpu_pmu->irq_affinity)
 				cpu = cpu_pmu->irq_affinity[i];
 
+			if (!cpu_online(cpu))
+				continue;
+
 			if (!cpumask_test_and_clear_cpu(cpu, &cpu_pmu->active_irqs))
 				continue;
 			irq = platform_get_irq(pmu_device, i);
@@ -665,6 +668,9 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler)
 			if (cpu_pmu->irq_affinity)
 				cpu = cpu_pmu->irq_affinity[i];
 
+			if (!cpu_online(cpu))
+				continue;
+
 			/*
 			 * If we have a single PMU interrupt that we can't shift,
 			 * assume that we're running on a uniprocessor machine and
-- 
2.1.4

Re: [PATCH] ARM: perf: ensure the cpu is available to scheduler when set irq affinity

[Will Deacon]

On Wed, Oct 21, 2015 at 03:56:02PM +0800, roy.qing.li@gmail.com wrote:
> From: Li RongQing <roy.qing.li@gmail.com> 
> 
> when there are 4 cpus, but only one is available to schedule, the warning
> will be generated when run the below command:
>     # perf record -g -e cpu-clock -- find / -name "*.ko"
>     CPU PMU: unable to set irq affinity (irq=28, cpu=1)
>     CPU PMU: unable to set irq affinity (irq=29, cpu=2)
>     CPU PMU: unable to set irq affinity (irq=30, cpu=3)
> 
> so ensure the cpu is available to scheduler when set irq affinity
> 
> Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
> ---
>  drivers/perf/arm_pmu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 2365a32..9401aa8 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -619,6 +619,9 @@ static void cpu_pmu_free_irq(struct arm_pmu *cpu_pmu)
>  			if (cpu_pmu->irq_affinity)
>  				cpu = cpu_pmu->irq_affinity[i];
>  
> +			if (!cpu_online(cpu))
> +				continue;
> +
>  			if (!cpumask_test_and_clear_cpu(cpu, &cpu_pmu->active_irqs))
>  				continue;
>  			irq = platform_get_irq(pmu_device, i);
> @@ -665,6 +668,9 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler)
>  			if (cpu_pmu->irq_affinity)
>  				cpu = cpu_pmu->irq_affinity[i];
>  
> +			if (!cpu_online(cpu))
> +				continue;
> +

Isn't this all racy against concurrent hotplug events? We're probably
better off requesting the IRQs at PMU probe time, since we no longer have
to worry about sharing the IRQ lines with other subsystems such as oprofile,
which is why it was designed this way originally.

Will

Re: [PATCH] ARM: perf: ensure the cpu is available to scheduler when set irq affinity

[Li RongQing]

On Wed, Oct 28, 2015 at 12:47 AM, Will Deacon <will.deacon@arm.com> wrote:
>> +                             continue;
>> +
>
> Isn't this all racy against concurrent hotplug events? We're probably
> better off requesting the IRQs at PMU probe time, since we no longer have
> to worry about sharing the IRQ lines with other subsystems such as oprofile,
> which is why it was designed this way originally.


Could you write a patch?
Thanks

-Roy