linux-kernel - Re: [RFC patch 3/5] ftrace trace event add missing semicolumn

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Message-ID: <20110105001837.GA9737@Krystal>
Date:	Tue, 4 Jan 2011 19:18:37 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC patch 3/5] ftrace trace event add missing semicolumn

* Frederic Weisbecker (fweisbec@...il.com) wrote:
> On Tue, Jan 04, 2011 at 06:16:32PM -0500, Mathieu Desnoyers wrote:
> > Add a missing semicolumn at the end of a ftrace definition.
> > 
> > We currently are not seeing any impact of this missing semicolumn because extra
> > semicolumns appear all over the place in the code generated from TRACE_EVENT
> > within ftrace stages.
> > 
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> > CC: Steven Rostedt <rostedt@...dmis.org>
> > CC: Frederic Weisbecker <fweisbec@...il.com>
> > CC: Ingo Molnar <mingo@...e.hu>
> > CC: Thomas Gleixner <tglx@...utronix.de>
> > ---
> >  include/trace/ftrace.h |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > Index: linux-2.6-lttng/include/trace/ftrace.h
> > ===================================================================
> > --- linux-2.6-lttng.orig/include/trace/ftrace.h
> > +++ linux-2.6-lttng/include/trace/ftrace.h
> > @@ -69,7 +69,7 @@
> >  #undef DEFINE_EVENT
> >  #define DEFINE_EVENT(template, name, proto, args)	\
> >  	static struct ftrace_event_call	__used		\
> > -	__attribute__((__aligned__(4))) event_##name
> > +	__attribute__((__aligned__(4))) event_##name;
> 
> But DEFINE_EVENT() calls are supposed to be ";" terminated, no?

Currently yes, but if you look at the preprocessor output currently generated by
the current TRACE_EVENT()/DEFINE_EVENT() scheme, there are useless ";" added all
over the place. I have a patch later in my queue that proposes removal of these
extra ";" as a cleanup of the TRACE_EVENT() semantic, but I'm keeping it for
later because it removes the extra ";" at the end of each TRACE_EVENT()
instance (and thus is more intrusive code-wise).

Adding this semicolumn here ensures that all Ftrace macros are consistent wrt
semicolumns. We can get away without consistency currently exactly because the
current scheme adds many useless semicolumns between each TRACE_EVENT().

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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