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

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Date:	Mon, 18 Nov 2013 14:40:32 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Vinayak Kale <vkale@....com>
Cc:	Will Deacon <will.deacon@....com>, patches <patches@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>, <jcm@...hat.com>,
	tglx <tglx@...utronix.de>, Tuan Phan <tphan@....com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V3 2/2] arm64: perf: add support for percpu pmu interrupt

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?
Do you call that a normal use of the API? Humfff....

         M.
-- 
Fast, cheap, reliable. Pick two.
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