linux-kernel - Re: [PATCH 2/4] tracing: add event trace infrastructure

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Date:	Wed, 25 Feb 2009 08:50:31 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Theodore Tso <tytso@....edu>,
	Arjan van de Ven <arjan@...radead.org>,
	Pekka Paalanen <pq@....fi>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jason Baron <jbaron@...hat.com>,
	Martin Bligh <mbligh@...gle.com>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 2/4] tracing: add event trace infrastructure


On Wed, 25 Feb 2009, Lai Jiangshan wrote:

> a very nice infrastructure!
> 
> Two comments about format:
> 
> Steven Rostedt ??:
> > From: Steven Rostedt <srostedt@...hat.com>
> > +#undef TPFMT
> > +#define TPFMT(fmt, args...)	fmt "\n", ##args
> 
> Where is other TPFMT's definition?
> I think TPFMT should be defined in tracepoint.h, because trace/<type>.h
> uses it.

I was thinking that. But in may just end up being a nop.

#define TPFMT(fmt, args)	/* define me */


> 
> > +#define DEFINE_TRACE_FMT(call, proto, args, fmt)			\
> > +static void ftrace_event_##call(proto)					\
> > +{									\
> > +	event_trace_printk(_RET_IP_, "(" #call ") " fmt);		\
> > +}									\
> > +									\
> > +static int ftrace_reg_event_##call(void)				\
> > +{									\
> > +	int ret;							\
> > +									\
> > +	ret = register_trace_##call(ftrace_event_##call);		\
> > +	if (!ret)							\
> > +		pr_info("event trace: Could not activate trace point "	\
> > +			"probe to " #call);				\
> > +	return ret;							\
> > +}									\
> > +									\
> > +static void ftrace_unreg_event_##call(void)				\
> > +{									\
> > +	unregister_trace_##call(ftrace_event_##call);			\
> > +}									\
> > +									\
> > +static struct ftrace_event_call __used					\
> > +__attribute__((section("_ftrace_events"))) event_##call = {		\
> > +	.name 			= #call,				\
> > +	.regfunc		= ftrace_reg_event_##call,		\
> > +	.unregfunc		= ftrace_unreg_event_##call,		\
> > +}
> > +
> > +void event_trace_printk(unsigned long ip, const char *fmt, ...);
> 
> add format checking here:
> __attribute__ ((format (printf, 2, 3)))
> 
> If user does not use this infrastructure(he uses trace/<type>.h only),
> this checking is not work, so I think we can add format checking
> in DEFINE_TRACE_FMT in tracepoint.h

Darn! You are correct. That was what I forgot to fix since the RFC
announcement. I had that on my TODO list and simply forgot.

Thanks!

> 
> --------example:
> 
> static inline void  __tp_check_format(const char *fmt, ...)
> 		__attribute__ ((format (printf, 1, 2)));
> static inline void __tp_check_format(const char *fmt, ...) {}
> 
> #define DECLARE_TRACE_FORMAT_CHECK(name, proto, fmt, fmt_args...)	\
> static inline void ftrace_event_check_format_##name(proto)		\
> {									\
> 	__tp_check_format(fmt, ##fmt_args);				\

Cool, thanks, I'll add that.

-- Steve

> }
> 
> #define DEFINE_TRACE_FMT(name, proto, args, fmt)			\
> 	DECLARE_TRACE_FORMAT_CHECK(name, TPPROTO(proto), fmt)		\
> 	DECLARE_TRACE(name, TPPROTO(proto), TPARGS(args))
> 
> ---------
> 
> Thanks, Lai
> 
> 
> 
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