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Commit 7496946a authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add samples of DECLARE_EVENT_CLASS() and DEFINE_EVENT() 



Add to samples/trace_events/ the macros DECLARE_EVENT_CLASS() and
DEFINE_EVENT() and recommend using them over multiple TRACE_EVENT()
macros if the multiple events have the same format.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 6adc13f8

samples/trace_events/trace-events-sample.c

+7 −0
Original line number Diff line number Diff line
@@ -35,7 +35,13 @@ static void simple_thread_func(int cnt) 
	trace_foo_bar("hello", cnt, array, random_strings[len],

		      tsk_cpus_allowed(current));



	trace_foo_with_template_simple("HELLO", cnt);



	trace_foo_bar_with_cond("Some times print", cnt);



	trace_foo_with_template_cond("prints other times", cnt);



	trace_foo_with_template_print("I have to be different", cnt);

}



static int simple_thread(void *arg)
@@ -58,6 +64,7 @@ static void simple_thread_func_fn(int cnt) 


	/* More silly tracepoints */

	trace_foo_bar_with_fn("Look at me", cnt);

	trace_foo_with_template_fn("Look at me too", cnt);

}



static int simple_thread_fn(void *arg)

samples/trace_events/trace-events-sample.h

+81 −0
Original line number Diff line number Diff line
@@ -314,6 +314,87 @@ TRACE_EVENT_FN(foo_bar_with_fn, 
	foo_bar_reg, foo_bar_unreg

);



/*

 * Each TRACE_EVENT macro creates several helper functions to produce

 * the code to add the tracepoint, create the files in the trace

 * directory, hook it to perf, assign the values and to print out

 * the raw data from the ring buffer. To prevent too much bloat,

 * if there are more than one tracepoint that uses the same format

 * for the proto, args, struct, assign and printk, and only the name

 * is different, it is highly recommended to use the DECLARE_EVENT_CLASS

 *

 * DECLARE_EVENT_CLASS() macro creates most of the functions for the

 * tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those

 * functions. This DEFINE_EVENT() is an instance of the class and can

 * be enabled and disabled separately from other events (either TRACE_EVENT

 * or other DEFINE_EVENT()s).

 *

 * Note, TRACE_EVENT() itself is simply defined as:

 *

 * #define TRACE_EVENT(name, proto, args, tstruct, assign, printk)  \

 *  DEFINE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \

 *  DEFINE_EVENT(name, name, proto, args)

 *

 * The DEFINE_EVENT() also can be declared with conditions and reg functions:

 *

 * DEFINE_EVENT_CONDITION(template, name, proto, args, cond);

 * DEFINE_EVENT_FN(template, name, proto, args, reg, unreg);

 */

DECLARE_EVENT_CLASS(foo_template,



	TP_PROTO(const char *foo, int bar),



	TP_ARGS(foo, bar),



	TP_STRUCT__entry(

		__string(	foo,    foo		)

		__field(	int,	bar		)

	),



	TP_fast_assign(

		__assign_str(foo, foo);

		__entry->bar	= bar;

	),



	TP_printk("foo %s %d", __get_str(foo), __entry->bar)

);



/*

 * Here's a better way for the previous samples (except, the first

 * exmaple had more fields and could not be used here).

 */

DEFINE_EVENT(foo_template, foo_with_template_simple,

	TP_PROTO(const char *foo, int bar),

	TP_ARGS(foo, bar));



DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond,

	TP_PROTO(const char *foo, int bar),

	TP_ARGS(foo, bar),

	TP_CONDITION(!(bar % 8)));





DEFINE_EVENT_FN(foo_template, foo_with_template_fn,

	TP_PROTO(const char *foo, int bar),

	TP_ARGS(foo, bar),

	foo_bar_reg, foo_bar_unreg);



/*

 * Anytime two events share basically the same values and have

 * the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT()

 * when ever possible.

 */



/*

 * If the event is similar to the DECLARE_EVENT_CLASS, but you need

 * to have a different output, then use DEFINE_EVENT_PRINT() which

 * lets you override the TP_printk() of the class.

 */



DEFINE_EVENT_PRINT(foo_template, foo_with_template_print,

	TP_PROTO(const char *foo, int bar),

	TP_ARGS(foo, bar),

	TP_printk("bar %s %d", __get_str(foo), __entry->bar));



#endif



/***** NOTICE! The #if protection ends here. *****/