linux-kernel - Re: [PATCH v2 1/7] ARM: perf_event: Support percpu irqs for the CPU PMU

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Date:	Fri, 17 Jan 2014 09:54:36 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Will Deacon <will.deacon@....com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/7] ARM: perf_event: Support percpu irqs for the CPU
 PMU

On 01/17/14 07:04, Will Deacon wrote:
> Hi Stephen,
>
> On Wed, Jan 15, 2014 at 08:54:27PM +0000, Stephen Boyd wrote:
>> On 01/15, Stephen Boyd wrote:
>>> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
>>> index 789d846a9184..e76750980b38 100644
>>> --- a/arch/arm/kernel/perf_event.c
>>> +++ b/arch/arm/kernel/perf_event.c
>>> @@ -295,9 +297,15 @@ validate_group(struct perf_event *event)
>>>  
>>>  static irqreturn_t armpmu_dispatch_irq(int irq, void *dev)
>>>  {
>>> -	struct arm_pmu *armpmu = (struct arm_pmu *) dev;
>>> -	struct platform_device *plat_device = armpmu->plat_device;
>>> -	struct arm_pmu_platdata *plat = dev_get_platdata(&plat_device->dev);
>>> +	struct arm_pmu *armpmu;
>>> +	struct platform_device *plat_device;
>>> +	struct arm_pmu_platdata *plat;
>>> +
>>> +	if (irq_is_percpu(irq))
>>> +		dev = *(struct arm_pmu_cpu **)dev;
>> Oh. I just realized that struct arm_pmu_cpu doesn't even exist. This
>> still compiles though because we're dealing with a void pointer.
>>
>> Perhaps its better to just do
>>
>> 	dev = *(void **)dev;
>>
>> here. Can you fix that up when applying? Otherwise I'll do it on
>> the next send if there are more comments.
> Shouldn't that actually be some per_cpu accessor like this_cpu_ptr?
>

Nope. The genirq layer unwraps the per_cpu pointer and passes it to the
handler.

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