korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-23 12:14:10 +08:00
Code Issues Packages Projects Releases Wiki Activity

tracing: Add TRACE_EVENT_FN example

Browse Source 
If a function should be called before a tracepoint is enabled
and/or after it is disabled, the TRACE_EVENT_FN() serves this
purpose. But it is not well documented. Having it as a sample would
help developers to know how to use it.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2015-02-09 16:32:19 -05:00 committed by Steven Rostedt
parent c4c7eb2938
commit 6adc13f8c0
2 changed files with 95 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
samples/trace_events/trace-events-sample.c
View File

@ -49,6 +49,52 @@ static int simple_thread(void *arg)
}
static struct task_struct *simple_tsk;
static struct task_struct *simple_tsk_fn;
static void simple_thread_func_fn(int cnt)
{
set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(HZ);
/* More silly tracepoints */
trace_foo_bar_with_fn("Look at me", cnt);
}
static int simple_thread_fn(void *arg)
{
int cnt = 0;
while (!kthread_should_stop())
simple_thread_func_fn(cnt++);
return 0;
}
static DEFINE_MUTEX(thread_mutex);
void foo_bar_reg(void)
{
pr_info("Starting thread for foo_bar_fn\n");
/*
* We shouldn't be able to start a trace when the module is
* unloading (there's other locks to prevent that). But
* for consistency sake, we still take the thread_mutex.
*/
mutex_lock(&thread_mutex);
simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
mutex_unlock(&thread_mutex);
}
void foo_bar_unreg(void)
{
pr_info("Killing thread for foo_bar_fn\n");
/* protect against module unloading */
mutex_lock(&thread_mutex);
if (simple_tsk_fn)
kthread_stop(simple_tsk_fn);
simple_tsk_fn = NULL;
mutex_unlock(&thread_mutex);
}
static int __init trace_event_init(void)
{
@ -62,6 +108,11 @@ static int __init trace_event_init(void)
static void __exit trace_event_exit(void)
{
kthread_stop(simple_tsk);
mutex_lock(&thread_mutex);
if (simple_tsk_fn)
kthread_stop(simple_tsk_fn);
simple_tsk_fn = NULL;
mutex_unlock(&thread_mutex);
}
module_init(trace_event_init);

44
samples/trace_events/trace-events-sample.h
View File

@ -270,6 +270,50 @@ TRACE_EVENT_CONDITION(foo_bar_with_cond,
TP_printk("foo %s %d", __get_str(foo), __entry->bar)
);
void foo_bar_reg(void);
void foo_bar_unreg(void);
/*
* Now in the case that some function needs to be called when the
* tracepoint is enabled and/or when it is disabled, the
* TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT()
* but adds two more parameters at the end:
*
* TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg)
*
* reg and unreg are functions with the prototype of:
*
* void reg(void)
*
* The reg function gets called before the tracepoint is enabled, and
* the unreg function gets called after the tracepoint is disabled.
*
* Note, reg and unreg are allowed to be NULL. If you only need to
* call a function before enabling, or after disabling, just set one
* function and pass in NULL for the other parameter.
*/
TRACE_EVENT_FN(foo_bar_with_fn,
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),
foo_bar_reg, foo_bar_unreg
);
#endif
/***** NOTICE! The #if protection ends here. *****/