linux-kernel - Re: [PATCH 02/11] tracing: Introduce TRACE_EVENT

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Message-ID: <20100210100440.GA5035@nowhere>
Date:	Wed, 10 Feb 2010 11:04:43 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Li Zefan <lizf@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH 02/11] tracing: Introduce TRACE_EVENT_INJECT

On Sat, Feb 06, 2010 at 08:19:30AM -0500, Steven Rostedt wrote:
> On Sat, 2010-02-06 at 13:20 +0100, Frederic Weisbecker wrote:
> 
> > I agree with you that creating a new trace event macro is a bit
> > insane. ftrace.h is already a nightmare. I just thought that
> > having the injector set inside the same macro that the synchronous
> > event is defined helped to make it clear about its nature: that
> > it needs a secondary async catch up thing.
> > 
> > But a register_event_injector thing will work too, we probably
> > better want that, given the maintainance pain otherwise.
> 
> We can add a register_event_injector later. For now, why not just add
> the TRACE_EVENT() and then hook to it in perf using the normal
> tracepoint mechanism.
> 
> You could add some macro around the trace_init_lock_class() call that
> would facilitate finding all the locks you need. This would probably be
> a bit more straight forward than to overload TRACE_EVENT() again.



I'm not sure what you mean by that.


 
> > 
> > I really would like to make something useful for everyone, could
> > you tell me more about johill needs?
> 
> Well, basically he needed a way to cause polling to happen using an
> event. From what I understood, the polling called the trace point. Just
> enabling the trace point did nothing because the polling did not take
> place. I thought about ways to enable this command when the trace point
> was enabled. But in the end, it was specific to a driver and another
> debugfs file seemed a better fit to initiate it.


Ok, thanks.

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