sched: turn on the use of unstable events

make use of sched-clock-unstable events.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -67,13 +67,6 @@ unsigned long long __attribute__((weak)) sched_clock(void)
 	return (unsigned long long)jiffies * (1000000000 / HZ);
 }
 
-/*
- * CPU frequency is/was unstable - start new by setting prev_clock_raw:
- */
-void sched_clock_unstable_event(void)
-{
-}
-
 /*
  * Convert user-nice values [ -20 ... 0 ... 19 ]
  * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
@@ -629,6 +622,20 @@ static inline struct rq *this_rq_lock(void)
 	return rq;
 }
 
+/*
+ * CPU frequency is/was unstable - start new by setting prev_clock_raw:
+ */
+void sched_clock_unstable_event(void)
+{
+	unsigned long flags;
+	struct rq *rq;
+
+	rq = task_rq_lock(current, &flags);
+	rq->prev_clock_raw = sched_clock();
+	rq->clock_unstable_events++;
+	task_rq_unlock(rq, &flags);
+}
+
 /*
  * resched_task - mark a task 'to be rescheduled now'.
  *