Re: [Xen-devel] [PATCH V8 1/3] irq: Add flags to request_percpu_irq function

[Mark Rutland <mark.rutland@xxxxxxx>]

Hi Daniel,

On Thu, Mar 23, 2017 at 06:42:01PM +0100, Daniel Lezcano wrote:
> In the next changes, we track the interrupts but we discard the timers as
> that does not make sense. The next interrupt on a timer is predictable.

Sorry, but I could not parse this. 

[...]

> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 9612b84..0f5ab4a 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -661,7 +661,7 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, 
> irq_handler_t handler)
>  
>       irq = platform_get_irq(pmu_device, 0);
>       if (irq > 0 && irq_is_percpu(irq)) {
> -             err = request_percpu_irq(irq, handler, "arm-pmu",
> +             err = request_percpu_irq(irq, 0, handler, "arm-pmu",
>                                        &hw_events->percpu_pmu);
>               if (err) {
>                       pr_err("unable to request IRQ%d for ARM PMU counters\n",

Please Cc myself and Will Deacon when modifying the arm_pmu driver, as
per MAINTAINERS. I only spotted this patch by chance.

This conflicts with arm_pmu changes I have queued for v4.12 [1].

So, can we leave the prototype of request_percpu_irq() as-is?

Why not add a new request_percpu_irq_flags() function, and leave
request_percpu_irq() as a wrapper for that? e.g.

static inline int
request_percpu_irq(unsigned int irq, irq_handler_t handler,
                   const char *devname, void __percpu *percpu_dev_id)
{
        return request_percpu_irq_flags(irq, handler, devname,
                                        percpu_dev_id, 0);
}

... that would avoid having to touch any non-timer driver for now.

[...]

> -request_percpu_irq(unsigned int irq, irq_handler_t handler,
> -                const char *devname, void __percpu *percpu_dev_id);
> +request_percpu_irq(unsigned int irq, unsigned long flags,
> +                irq_handler_t handler,  const char *devname,
> +                void __percpu *percpu_dev_id);
>  

Looking at request_irq, the prototype is:

int __must_check
request_irq(unsigned int irq, irq_handler_t handler,
            unsigned long flags, const char *name,
            void *dev);

... surely it would be better to share the same argument order? i.e.

int __must_check
request_percpu_irq(unsigned int irq, irq_handler_t handler,
                   unsigned long flags, const char *devname,
                   void __percpu *percpu_dev_id);

Thanks,
Mark.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm/perf/refactoring

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