Commit 7496946a authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt

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: 's avatarSteven Rostedt <>
parent 6adc13f8
......@@ -35,7 +35,13 @@ static void simple_thread_func(int cnt)
trace_foo_bar("hello", cnt, array, random_strings[len],
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)
......@@ -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);
TP_PROTO(const char *foo, int bar),
TP_ARGS(foo, bar),
__string( foo, foo )
__field( int, bar )
__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));
/***** NOTICE! The #if protection ends here. *****/
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