linux-kernel - Re: [PATCH V4 2/2] arm64: perf: add support for percpu pmu interrupt

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Date:	Wed, 20 Nov 2013 18:00:12 +0000
From:	Will Deacon <will.deacon@....com>
To:	Vinayak Kale <vkale@....com>
Cc:	Marc Zyngier <Marc.Zyngier@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"jcm@...hat.com" <jcm@...hat.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Tuan Phan <tphan@....com>
Subject: Re: [PATCH V4 2/2] arm64: perf: add support for percpu pmu interrupt

On Wed, Nov 20, 2013 at 05:28:50PM +0000, Vinayak Kale wrote:
> In Will's existing code, I think he was taking care of 'no IRQ' case
> by comparing pmu_device->num_resources. Do you think this is not
> enough and we must enforce the check after each platform_get_irq()?
> Existing driver code snippet as below for quick reference.
> 
> [snip]
> static int
> armpmu_reserve_hardware(struct arm_pmu *armpmu)
> {
>         int i, err, irq, irqs;
>         struct platform_device *pmu_device = armpmu->plat_device;
> 
>         if (!pmu_device) {
>                 pr_err("no PMU device registered\n");
>                 return -ENODEV;
>         }
> 
>         irqs = min(pmu_device->num_resources, num_possible_cpus());
>         if (irqs < 1) {
>                 pr_err("no irqs for PMUs defined\n");
>                 return -ENODEV;
>         }

This bit is fine.

>         for (i = 0; i < irqs; ++i) {
>                 err = 0;
>                 irq = platform_get_irq(pmu_device, i);
>                 if (irq < 0)
>                          continue;

This is a bug, which you can fix in your patch. IRQ0 isn't valid.

Will
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