linux-kernel - Re: [PATCH v3 1/2] irq: abstract irqaction handler invocation

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Date:   Thu, 15 Jul 2021 12:49:54 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, maz@...nel.org,
        paulmck@...nel.org
Subject: Re: [PATCH v3 1/2] irq: abstract irqaction handler invocation

On Thu, Jul 15, 2021 at 10:50:30AM +0100, Mark Rutland wrote:
> diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
> index 54363527feea..70a4694cc891 100644
> --- a/kernel/irq/internals.h
> +++ b/kernel/irq/internals.h
> @@ -11,6 +11,8 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/sched/clock.h>
>  
> +#include <trace/events/irq.h>
> +
>  #ifdef CONFIG_SPARSE_IRQ
>  # define IRQ_BITMAP_BITS	(NR_IRQS + 8196)
>  #else
> @@ -107,6 +109,32 @@ irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc, unsigned int *flags
>  irqreturn_t handle_irq_event_percpu(struct irq_desc *desc);
>  irqreturn_t handle_irq_event(struct irq_desc *desc);
>  
> +static inline irqreturn_t __handle_irqaction(unsigned int irq,
> +					     struct irqaction *action,
> +					     void *dev_id)
> +{
> +	irqreturn_t res;
> +
> +	trace_irq_handler_entry(irq, action);
> +	res = action->handler(irq, dev_id);
> +	trace_irq_handler_exit(irq, action, res);
> +
> +	return res;
> +}
> +
> +static inline irqreturn_t handle_irqaction(unsigned int irq,
> +					   struct irqaction *action)
> +{
> +	return __handle_irqaction(irq, action, action->dev_id);
> +}
> +
> +static inline irqreturn_t handle_irqaction_percpu_devid(unsigned int irq,
> +							struct irqaction *action)
> +{
> +	return __handle_irqaction(irq, action,
> +				  raw_cpu_ptr(action->percpu_dev_id));
> +}

So I like this patch, it's a nice cleanup.

However, you could implement the next patch as a module that hooks into
those two tracepoints. Quite possibly the existing IRQ latency tracer
would already work for what you need and also provide you a function
trace of WTH the CPU was doing.