sched: rt-bandwidth group disable fixes

More extensive disable of bandwidth control. It allows sysctl_sched_rt_runtime
to disable full group bandwidth control.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 9a1ddb8..c1bee5f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -204,11 +204,13 @@
 	rt_b->rt_period_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
 }
 
+static inline int rt_bandwidth_enabled(void);
+
 static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
 {
 	ktime_t now;
 
-	if (rt_b->rt_runtime == RUNTIME_INF)
+	if (rt_bandwidth_enabled() && rt_b->rt_runtime == RUNTIME_INF)
 		return;
 
 	if (hrtimer_active(&rt_b->rt_period_timer))
@@ -839,6 +841,11 @@
 	return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
 }
 
+static inline int rt_bandwidth_enabled(void)
+{
+	return sysctl_sched_rt_runtime >= 0;
+}
+
 #ifndef prepare_arch_switch
 # define prepare_arch_switch(next)	do { } while (0)
 #endif