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

Hi Mark,

On Thu, Mar 23, 2017 at 06:54:52PM +0000, Mark Rutland wrote:

Hi Daniel,

On Thu, Mar 23, 2017 at 06:42:01PM +0100, Daniel Lezcano wrote:

quoted

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. 

I meant we are measuring when are happening the interrupts by getting the local
clock in the interrupt handler. But if the interrupts are coming from a timer, it
is not necessary to do that because we already know when they will occur.

So, in order to sort out which interrupt we measure, we use the IRQF_TIMER flag.

Unfortunately, this flag is missing when we do a request_percpu_irq. The
purpose of this patch is to fix that.

quoted

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.

Ah, ok, sorry for that. Thanks for spotting this, you should have been Cc'ed by
my cccmd script. I will check that.

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.

Mmh, yes. That's a good suggestion.

[...]

quoted

-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);

Agree.

Thanks for the review.

  -- Daniel


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