Re: [RFC][PATCH 2/2] [PATCH 2/2] tracing: Make event based trace_printk()

From: Lai Jiangshan <laijs@cn.fujitsu.com>
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>,
	Darren Hart <dvhart@linux.intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"jason.wessel" <jason.wessel@windriver.com>,
	"Ted Ts'o" <tytso@mit.edu>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [RFC][PATCH 2/2] [PATCH 2/2] tracing: Make event based trace_printk()
Date: Thu, 18 Nov 2010 13:50:06 +0800	[thread overview]
Message-ID: <4CE4BE8E.8060509@cn.fujitsu.com> (raw)
In-Reply-To: <20101118040949.782054673@goodmis.org>

On 11/18/2010 11:58 AM, Steven Rostedt wrote:
> +#define trace_printk(fmt, args...)					\
> +	do {								\
> +		static struct event_printk_struct			\
> +		__attribute__((__aligned__(4)))				\
> +		__attribute__((section("_trace_printk")))		\
> +		______t = {						\
> +			.format = fmt,					\

if fmt is not constant, the compiler will complain...

> +			.func = __func__,				\
> +			.file = __FILE__,				\
> +			.line = __LINE__,				\
> +		};							\
> +		__trace_printk_check_format(fmt, ##args);		\
> +		if (!__builtin_constant_p(fmt))				\
> +			trace_printk_can_only_have_constant_format();	\

so this is not need.

> +		if (unlikely(__event_printk_test(&______t.enable)))	\
> +			__trace_bprintk(_THIS_IP_, fmt, ##args); \
> +	} while (0)