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Date: Thu, 14 May 2009 20:01:20 -0400 (EDT)
From: Steven Rostedt <rostedt@goodmis.org>
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To: Frederic Weisbecker <fweisbec@gmail.com>
cc: LKML <linux-kernel@vger.kernel.org>, Christoph Hellwig <hch@infradead.org>,
       Ingo Molnar <mingo@elte.hu>,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC] tracing: adding flags to events
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On Fri, 15 May 2009, Frederic Weisbecker wrote:

> On Thu, May 14, 2009 at 07:18:23PM -0400, Steven Rostedt wrote:
> > > > +
> > > >  #undef TRACE_EVENT
> > > >  #define TRACE_EVENT(call, proto, args, tstruct, assign, print)		\
> > > >  enum print_line_t							\
> > > > @@ -127,6 +132,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags)	\
> > > >  	struct trace_seq *s = &iter->seq;				\
> > > >  	struct ftrace_raw_##call *field;				\
> > > >  	struct trace_entry *entry;					\
> > > > +	struct trace_seq *p;						\
> > > >  	int ret;							\
> > > >  									\
> > > >  	entry = iter->ent;						\
> > > > @@ -138,7 +144,9 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags)	\
> > > >  									\
> > > >  	field = (typeof(field))entry;					\
> > > >  									\
> > > > +	p = &get_cpu_var(ftrace_event_seq);				\
> > > >  	ret = trace_seq_printf(s, #call ": " print);			\
> > > > +	put_cpu();							\
> > > 
> > > 
> > > 
> > > I don't understand the role of this per-cpu trace_seq variable.
> > > It doesn't seem to be used.
> > 
> > See it now? ;-)
> 
> 
> Still not :-)
> 
> I don't understand, it doesn't seem to be used. May be I'm too
> much sleepy to understand...

That's because you cut out an important detail ;-)

> > +#define __print_flags(flag, x...) ftrace_print_flags_seq(p, flag, x)


-- Steve