tracing: Add TRACE_EVENT_FN example

[cascardo/linux.git] / 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 c396a49..39d4484 100644 (file)
--- 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);