From 6adc13f8c096736957444ffa2aa11421b5671aef Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Mon, 9 Feb 2015 16:32:19 -0500 Subject: tracing: Add TRACE_EVENT_FN example 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 --- samples/trace_events/trace-events-sample.c | 51 ++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) (limited to 'samples/trace_events/trace-events-sample.c') diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c index c396a49b5d78..39d4484aef53 100644 --- a/samples/trace_events/trace-events-sample.c +++ b/samples/trace_events/trace-events-sample.c @@ -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); -- cgit v1.2.3-59-g8ed1b