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Date: Wed, 25 Feb 2009 17:07:02 +0800
From: Lai Jiangshan <laijs@cn.fujitsu.com>
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To: Steven Rostedt <rostedt@goodmis.org>
CC: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>,
       Frederic Weisbecker <fweisbec@gmail.com>, Theodore Tso <tytso@mit.edu>,
       Arjan van de Ven <arjan@infradead.org>, Pekka Paalanen <pq@iki.fi>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Jason Baron <jbaron@redhat.com>, Martin Bligh <mbligh@google.com>,
       Mathieu Desnoyers <compudj@krystal.dyndns.org>,
       "Frank Ch. Eigler" <fche@redhat.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Jens Axboe <jens.axboe@oracle.com>,
       Masami Hiramatsu <mhiramat@redhat.com>,
       Steven Rostedt <srostedt@redhat.com>
Subject: Re: [PATCH 2/4] tracing: add event trace infrastructure
References: <20090225025608.956691460@goodmis.org> <20090225025753.798204550@goodmis.org>
In-Reply-To: <20090225025753.798204550@goodmis.org>
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a very nice infrastructure!

Two comments about format:

Steven Rostedt 写道:
> From: Steven Rostedt <srostedt@redhat.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.

> +#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

--------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);				\
}

#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