linux-kernel - Re: [Patch 2/2] tracepoints for softirq entry/exit

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Date:	Mon, 16 Mar 2009 15:17:09 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jason Baron <jbaron@...hat.com>
cc:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	acme@...stprotocols.net, fweisbec@...il.com, fche@...hat.com,
	peterz@...radead.org, compudj@...stal.dyndns.org
Subject: Re: [Patch 2/2] tracepoints for softirq entry/exit - tracepoints


On Mon, 16 Mar 2009, Jason Baron wrote:

> hi,
> 
> ok, below is a re-spun patch 2/2 which converts to the TRACE_EVENT
> format.

Thanks, some comments though.

> 
> thanks,
> 
> -Jason
> 
> 
> Signed-off-by: Jason Baron <jbaron@...hat.com>
> 
> ---
> 
>  include/trace/irq_event_types.h |   36 ++++++++++++++++++++++++++++++++++++
>  kernel/softirq.c                |    7 ++++++-
>  2 files changed, 42 insertions(+), 1 deletions(-)
> 
> 
> diff --git a/include/trace/irq_event_types.h b/include/trace/irq_event_types.h
> index 214bb92..de1f2a9 100644
> --- a/include/trace/irq_event_types.h
> +++ b/include/trace/irq_event_types.h
> @@ -40,4 +40,40 @@ TRACE_EVENT(irq_handler_exit,
>  		  __entry->irq, __entry->ret ? "handled" : "unhandled")
>  );
>  
> +TRACE_EVENT(softirq_action_entry,
> +
> +	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
> +
> +	TP_ARGS(h, vec),
> +
> +	TP_STRUCT__entry(
> +		__array(	char,	softirq_name,	MAX_SOFTIRQ_NAME_LEN )
> +	),
> +
> +	TP_fast_assign(
> +		memcpy(__entry->softirq_name, softirq_to_name[h-vec],
> +			MAX_SOFTIRQ_NAME_LEN);

memcpy isn't fast ;-)

What you want is this:

	TP_STRUCT__entry(
		__field(	int,	vec	)
	),

	TP_fast_assign(
		__entry->vec = h - vec;
> +	),
> +
> +	TP_printk("softirq entry: %s", __entry->softirq_name)

	TP_printk("softirq entry: %s", softirq_to_name[__entry->vec])

> +);
> +
> +TRACE_EVENT(softirq_action_exit,
> +
> +	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
> +
> +	TP_ARGS(h, vec),
> +
> +	TP_STRUCT__entry(
> +		__array(	char,	softirq_name,	MAX_SOFTIRQ_NAME_LEN )
> +	),
> +
> +	TP_fast_assign(
> +		memcpy(__entry->softirq_name, softirq_to_name[h-vec],
> +			MAX_SOFTIRQ_NAME_LEN);
> +	),
> +
> +	TP_printk("softirq exit: %s", __entry->softirq_name)


And do the same here.

-- Steve

> +);
> +
>  #undef TRACE_SYSTEM
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 8f3ae57..5e96c77 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -24,6 +24,7 @@
>  #include <linux/ftrace.h>
>  #include <linux/smp.h>
>  #include <linux/tick.h>
> +#include <trace/irq.h>
>  
>  #include <asm/irq.h>
>  /*
> @@ -185,6 +186,9 @@ EXPORT_SYMBOL(local_bh_enable_ip);
>   */
>  #define MAX_SOFTIRQ_RESTART 10
>  
> +DEFINE_TRACE(softirq_action_entry);
> +DEFINE_TRACE(softirq_action_exit);
> +
>  asmlinkage void __do_softirq(void)
>  {
>  	struct softirq_action *h;
> @@ -211,8 +215,9 @@ restart:
>  		if (pending & 1) {
>  			int prev_count = preempt_count();
>  
> +			trace_softirq_action_entry(h, softirq_vec);
>  			h->action(h);
> -
> +			trace_softirq_action_exit(h, softirq_vec);
>  			if (unlikely(prev_count != preempt_count())) {
>  				printk(KERN_ERR "huh, entered softirq %td %s %p"
>  				       "with preempt_count %08x,"
> 
--
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