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

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Date:	Mon, 18 Nov 2013 20:26:15 +0530
From:	Vinayak Kale <vkale@....com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Will Deacon <will.deacon@....com>, patches <patches@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"jcm@...hat.com" <jcm@...hat.com>, tglx <tglx@...utronix.de>,
	Tuan Phan <tphan@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V3 2/2] arm64: perf: add support for percpu pmu interrupt

On Mon, Nov 18, 2013 at 8:10 PM, Marc Zyngier <marc.zyngier@....com> wrote:
> On 2013-11-18 14:18, Vinayak Kale wrote:
>>
>> On Mon, Nov 18, 2013 at 7:16 PM, Marc Zyngier <marc.zyngier@....com>
>> wrote:
>>>
>>> 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@....com>
>>>> Signed-off-by: Tuan Phan <tphan@....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.
>>
>> I don't think it's being misused. In case of invalid irq number, the
>> API would return null.
>
>
> And feeding an error code to irq_to_desc() doesn't disturb you?
Since the API handles the error condition and returns null, so it
won't break stuff.
But I think your earlier suggestion of checking invalid irq number
beforehand is better, since it would help to avoid wasting time in
searching the irq desc.
> Do you call that a normal use of the API? Humfff....
>
>         M.
>
> --
> Fast, cheap, reliable. Pick two.
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