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

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Message-ID: <20140117180825.GV16003@mudshark.cambridge.arm.com>
Date:	Fri, 17 Jan 2014 18:08:26 +0000
From:	Will Deacon <will.deacon@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
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 Fri, Jan 17, 2014 at 05:54:36PM +0000, Stephen Boyd wrote:
> 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.

Ah yeah, I forget the dispatcher is what genirq sees as the handler. In
which case your idea looks right.

Sorry for the noise.

Will
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