linux-kernel - Re: [PATCH v3] ftrace: add a tracepoint for __raise_softirq

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Date:	Tue, 12 May 2009 17:50:47 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, fweisbec@...il.com, zhaolei@...fujitsu.com,
	laijs@...fujitsu.com, Li Zefan <lizf@...fujitsu.com>
Subject: Re: [PATCH v3] ftrace: add a tracepoint for	__raise_softirq_irqoff()



Mathieu Desnoyers wrote:
> * Steven Rostedt (rostedt@...dmis.org) wrote:
>>
>>
>> On Mon, 11 May 2009, Mathieu Desnoyers wrote:
>>
>>> * Steven Rostedt (rostedt@...dmis.org) wrote:
>>>> On Mon, 11 May 2009, Mathieu Desnoyers wrote:
>>>>> Yes, we should try to fix TRACE_EVENT, but we should fix it _before_ we
>>>>> start using it widely. Circular header dependencies is a real problem
>>>>> with TRACE_EVENT right now.

> Yes, but this would solve most of the include dependency problems at
> once. We would only have dependency on preempt.h left, which alone is
> easier to deal with. And if headers don't need to include any annoying
> headers, they don't need to use the ifdef BUILDING_EVENTS. But my point
> is that when it's needed (and we already see two cases where it's
> needed, with pvops instrumentation and softirq instrumentation, and I
> guess we'll see much more), it's good to have this infrastructure in
> place, so people don't end up trying to do hacks to the kernel code
> changing inlines for function calls to try to deal with the circular
> include issue.
> 
> I think it's
> 
> a) needed
> b) it does not hurt anyone who does not need it.
> 
> So I would definitely recommend adding such define.
> 

Sorry for my poor English.
Problem is not only in TP_printk, but also in TP_PROTO if we add a
tracer in header file.
So, it can't be solved only by "get rid of including ftrace parts"

Take v2 patch for example: 
(it is at: http://marc.info/?l=linux-kernel&m=124081169727739&w=2) 

In order to trace __raise_softirq_irqoff(), we should add 
a trace function in  __raise_softirq_irqoff() and include 
<include/trace/irq.h> in interrupte.h. 
If we put <include/trace/irq.h> on top of linux/irq.h,
we will see a warning of "struct softirq_action declared
inside parameter list" in compile. It is because struct irqaction's
definition is bypasswd before TP_PROTO.

To say it simple: 
sched.c:
include interrupte.h
	|
	|-->include irq.h
	|	|-->include interrupte.h (bypassed)
	|	|-->TP_PROTO(int irq, struct irqaction *action),
	|	    (but struct softirq_action is not declared before,
	|	     it raise a compile warning:struct softirq_action declared
	|	     inside parameter list.
	|-> ......
	
I can't see the solvent for this in your discuss or I understand wrong? 

Xiao

> Mathieu
> 
>> -- Steve
>>
>>> I think it should work, but it looks a bit too simple, so I may have
>>> missed something... ?
>>>
>>> Mathieu
>>>
>>>
>>> -- 
>>> Mathieu Desnoyers
>>> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
>>>
> 
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