sched: add latency tracer callbacks to the scheduler

add 3 lightweight callbacks to the tracer backend.

zero impact if tracing is turned off.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/sched.c b/kernel/sched.c
index cfa222a..463dcdb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2467,6 +2467,7 @@
 
 out_activate:
 #endif /* CONFIG_SMP */
+	ftrace_wake_up_task(p, rq->curr);
 	schedstat_inc(p, se.nr_wakeups);
 	if (sync)
 		schedstat_inc(p, se.nr_wakeups_sync);
@@ -2611,6 +2612,7 @@
 		p->sched_class->task_new(rq, p);
 		inc_nr_running(rq);
 	}
+	ftrace_wake_up_new_task(p, rq->curr);
 	check_preempt_curr(rq, p);
 #ifdef CONFIG_SMP
 	if (p->sched_class->task_wake_up)
@@ -2783,6 +2785,7 @@
 	struct mm_struct *mm, *oldmm;
 
 	prepare_task_switch(rq, prev, next);
+	ftrace_ctx_switch(prev, next);
 	mm = next->mm;
 	oldmm = prev->active_mm;
 	/*