linux-kernel - Re: [PATCH v1] softirq: Add tracepoint for tasklet

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Date:   Tue, 24 May 2022 21:07:09 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Junwen Wu <wudaemon@....com>
Cc:     mingo@...hat.com, tglx@...utronix.de, frederic@...nel.org,
        tannerlove@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] softirq: Add tracepoint for tasklet_entry/exit

On Sun,  8 May 2022 16:06:24 +0000
Junwen Wu <wudaemon@....com> wrote:

> --- a/include/trace/events/irq.h
> +++ b/include/trace/events/irq.h
> @@ -160,6 +160,38 @@ DEFINE_EVENT(softirq, softirq_raise,
>  	TP_ARGS(vec_nr)
>  );
>  
> +TRACE_EVENT(tasklet_entry,
> +
> +	TP_PROTO(void *func),
> +
> +	TP_ARGS(func),
> +
> +	TP_STRUCT__entry(
> +		__field(        void *,    func          )
> +	),
> +
> +	TP_fast_assign(
> +	__entry->func = func;
> +	),
> +
> +	TP_printk("function=%ps", __entry->func)
> +);
> +TRACE_EVENT(tasklet_exit,
> +
> +	TP_PROTO(void *func),
> +
> +	TP_ARGS(func),
> +
> +	TP_STRUCT__entry(
> +		__field(        void *,    func          )
> +	),
> +
> +	TP_fast_assign(
> +		__entry->func = func;
> +	),
> +
> +	TP_printk("function=%ps", __entry->func)

This needs an acked-by from Thomas, but regardless, the above two trace
events are identical. You need to have a DECLARE_EVENT_CLASS() followed by
two DEFINE_EVENT()s, otherwise you are wasting memory.

-- Steve


> +);
>  #endif /*  _TRACE_IRQ_H */
>  
>  /* This part must be outside protection */
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 41f470929e99..b3bce2b3b655 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -780,10 +780,14 @@ static void tasklet_action_common(struct softirq_action *a,
>  		if (tasklet_trylock(t)) {
>  			if (!atomic_read(&t->count)) {
>  				if (tasklet_clear_sched(t)) {
> +					trace_tasklet_entry(t->use_callback ? (void *)t->callback 
> +							: (void *)t->func);
>  					if (t->use_callback)
>  						t->callback(t);
>  					else
>  						t->func(t->data);
> +					trace_tasklet_exit(t->use_callback ? (void *)t->callback
> +							: (void *)t->func);
>  				}
>  				tasklet_unlock(t);
>  				continue;