linux-kernel - Re: [PATCH v4 1/5] irq: add tracepoint to softirq

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Date:	Mon, 06 Sep 2010 10:46:12 +0900
From:	Koki Sanagi <sanagi.koki@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Steven Rostedt <rostedt@...dmis.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, davem@...emloft.net,
	kaneshige.kenji@...fujitsu.com, izumi.taku@...fujitsu.com,
	kosaki.motohiro@...fujitsu.com, nhorman@...driver.com,
	laijs@...fujitsu.com, scott.a.mcmillan@...el.com,
	eric.dumazet@...il.com, mathieu.desnoyers@...ymtl.ca
Subject: Re: [PATCH v4 1/5] irq: add tracepoint to softirq_raise

(2010/09/04 0:50), Frederic Weisbecker wrote:
> On Fri, Sep 03, 2010 at 11:43:12AM -0400, Steven Rostedt wrote:
>> On Fri, 2010-09-03 at 17:29 +0200, Frederic Weisbecker wrote:
>>
>>>>  /*
>>>>   * These correspond to the IORESOURCE_IRQ_* defines in
>>>> @@ -407,7 +408,12 @@ asmlinkage void do_softirq(void);
>>>>  asmlinkage void __do_softirq(void);
>>>>  extern void open_softirq(int nr, void (*action)(struct softirq_action *));
>>>>  extern void softirq_init(void);
>>>> -#define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)
>>>> +static inline void __raise_softirq_irqoff(unsigned int nr)
>>>> +{
>>>> +	trace_softirq_raise((struct softirq_action *)&nr, NULL);
>>
>> Perhaps doing:
>>
>> 	trace_softirq_raise((struct softirq_action *)((unsigend long)nr),
>> 				NULL);
>>
>> and ...
>>
>>>> +	or_softirq_pending(1UL << nr);
>>>> +}
>>>> +
>>>>  extern void raise_softirq_irqoff(unsigned int nr);
>>>>  extern void raise_softirq(unsigned int nr);
>>>>  extern void wakeup_softirqd(void);
>>>> diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
>>>> index 0e4cfb6..3ddda02 100644
>>>> --- a/include/trace/events/irq.h
>>>> +++ b/include/trace/events/irq.h
>>>> @@ -5,7 +5,9 @@
>>>>  #define _TRACE_IRQ_H
>>>>  
>>>>  #include <linux/tracepoint.h>
>>>> -#include <linux/interrupt.h>
>>>> +
>>>> +struct irqaction;
>>>> +struct softirq_action;
>>>>  
>>>>  #define softirq_name(sirq) { sirq##_SOFTIRQ, #sirq }
>>>>  #define show_softirq_name(val)				\
>>>> @@ -93,7 +95,10 @@ DECLARE_EVENT_CLASS(softirq,
>>>>  	),
>>>>  
>>>>  	TP_fast_assign(
>>>> -		__entry->vec = (int)(h - vec);
>>>> +		if (vec)
>>>> +			__entry->vec = (int)(h - vec);
>>>> +		else
>>>> +			__entry->vec = *((int *)h);
>>
>> 			__entry->vec = (int)h;
>>
>> would be better.
>>
>>
>>>>  	),
>>>
>>>
>>>
>>> It seems that this will break softirq_entry/exit tracepoints.
>>> __entry->vec will deref vec->action() for these two, which is not
>>> what we want.
>>>
>>> If you can't have the same tracepoint signature for the three, just
>>> split the new one in a seperate TRACE_EVENT().
>>
>> Doing the above will at least be a bit safer.
> 
> 
> Agreed, I'm going to change that in the patch.
> 
> Thanks.
> 

I agree.

Thanks,
Koki Sanagi.

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