linux-kernel - Re: [PATCH 06/10] tracing: add print

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Date:	Thu, 10 Dec 2009 19:25:04 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Jason Baron <jbaron@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/10] tracing: add print_fmt field

On Wed, 2009-12-09 at 15:15 +0800, Lai Jiangshan wrote:
> Add print_fmt field and the initialization codes.
> It will be used for replacing ->show_format().

This change log is very lacking. I don't even know what this patch is
doing. I'm guessing other patches will depend on it. But this patch
alone should have a change log that describes the goal that will happen
to give it rational.

If I'm bisecting the kernel and I come across this change, I want the
change log to explain why this change exists, and not have to spend time
searching the logs for other patches that may depend on this one.


-- Steve

> 
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> ---
> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
> index f883406..58db567 100644
> --- a/include/linux/ftrace_event.h
> +++ b/include/linux/ftrace_event.h
> @@ -120,6 +120,7 @@ struct ftrace_event_call {
>  	int			(*regfunc)(struct ftrace_event_call *);
>  	void			(*unregfunc)(struct ftrace_event_call *);
>  	int			id;
> +	const char		*print_fmt;
>  	int			(*raw_init)(struct ftrace_event_call *);
>  	int			(*show_format)(struct ftrace_event_call *,
>  					       struct trace_seq *);
> diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> index 54258a0..eb63c97 100644
> --- a/include/trace/ftrace.h
> +++ b/include/trace/ftrace.h
> @@ -723,8 +723,20 @@ static struct trace_event ftrace_event_type_##call = {			\
>  
>  #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
>  
> +#undef __entry
> +#define __entry REC
> +
> +#undef __print_flags
> +#undef __print_symbolic
> +#undef __get_dynamic_array
> +#undef __get_str
> +
> +#undef TP_printk
> +#define TP_printk(fmt, args...) #fmt ", "  __stringify(args)
> +
>  #undef DECLARE_EVENT_CLASS
> -#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)
> +#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
> +static const char print_fmt_##call[] = print;
>  
>  #undef DEFINE_EVENT
>  #define DEFINE_EVENT(template, call, proto, args)			\
> @@ -738,6 +750,7 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  	.raw_init		= trace_event_raw_init,			\
>  	.regfunc		= ftrace_raw_reg_event_##call,		\
>  	.unregfunc		= ftrace_raw_unreg_event_##call,	\
> +	.print_fmt		= print_fmt_##template,			\
>  	.show_format		= ftrace_format_##template,		\
>  	.define_fields		= ftrace_define_fields_##template,	\
>  	_TRACE_PROFILE_INIT(call)					\
> @@ -746,6 +759,8 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  #undef DEFINE_EVENT_PRINT
>  #define DEFINE_EVENT_PRINT(template, call, proto, args, print)		\
>  									\
> +static const char print_fmt_##call[] = print;				\
> +									\
>  static struct ftrace_event_call __used					\
>  __attribute__((__aligned__(4)))						\
>  __attribute__((section("_ftrace_events"))) event_##call = {		\
> @@ -755,6 +770,7 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  	.raw_init		= trace_event_raw_init,			\
>  	.regfunc		= ftrace_raw_reg_event_##call,		\
>  	.unregfunc		= ftrace_raw_unreg_event_##call,	\
> +	.print_fmt		= print_fmt_##call,			\
>  	.show_format		= ftrace_format_##call,			\
>  	.define_fields		= ftrace_define_fields_##template,	\
>  	_TRACE_PROFILE_INIT(call)					\
> @@ -838,6 +854,16 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  
>  #ifdef CONFIG_EVENT_PROFILE
>  
> +#undef __entry
> +#define __entry entry
> +
> +#undef __get_dynamic_array
> +#define __get_dynamic_array(field)	\
> +		((void *)__entry + (__entry->__data_loc_##field & 0xffff))
> +
> +#undef __get_str
> +#define __get_str(field) (char *)__get_dynamic_array(field)
> +
>  #undef __perf_addr
>  #define __perf_addr(a) __addr = (a)
>  
> diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
> index 9978a4f..95d14b6 100644
> --- a/kernel/trace/trace_export.c
> +++ b/kernel/trace/trace_export.c
> @@ -203,6 +203,9 @@ static int ftrace_raw_init_event(struct ftrace_event_call *call)
>  	return 0;
>  }
>  
> +#undef __entry
> +#define __entry REC
> +
>  #undef __field
>  #define __field(type, item)
>  
> @@ -218,6 +221,9 @@ static int ftrace_raw_init_event(struct ftrace_event_call *call)
>  #undef __dynamic_array
>  #define __dynamic_array(type, item)
>  
> +#undef F_printk
> +#define F_printk(fmt, args...) #fmt ", "  __stringify(args)
> +
>  #undef FTRACE_ENTRY
>  #define FTRACE_ENTRY(call, struct_name, type, tstruct, print)		\
>  									\
> @@ -228,6 +234,7 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  	.id			= type,					\
>  	.system			= __stringify(TRACE_SYSTEM),		\
>  	.raw_init		= ftrace_raw_init_event,		\
> +	.print_fmt		= print,				\
>  	.show_format		= ftrace_format_##call,			\
>  	.define_fields		= ftrace_define_fields_##call,		\
>  };									\
> 
> 


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