sched/rt: Keep period timer ticking when rt throttling is active

When a runqueue is throttled we cannot disable the period timer
because that timer is the only way to undo the throttling.

We got stale throttling entries when a rq was throttled and then the
global sysctl was disabled, which stopped the timer.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[ Added changelog ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-nuj34q52p6ro7szapuz84i0v@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 5 deletions

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index f70206c2c802..6d1eb0be1870 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -778,12 +778,9 @@ static inline int balance_runtime(struct rt_rq *rt_rq)
 
 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 {
-        int i, idle = 1;
+        int i, idle = 1, throttled = 0;
         const struct cpumask *span;
 
-        if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
-                return 1;
-
         span = sched_rt_period_mask();
         for_each_cpu(i, span) {
                 int enqueue = 0;
@@ -818,12 +815,17 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
                         if (!rt_rq_throttled(rt_rq))
                                 enqueue = 1;
                 }
+                if (rt_rq->rt_throttled)
+                        throttled = 1;
 
                 if (enqueue)
                         sched_rt_rq_enqueue(rt_rq);
                 raw_spin_unlock(&rq->lock);
         }
 
+        if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
+                return 1;
+
         return idle;
 }
 
@@ -884,7 +886,8 @@ static void update_curr_rt(struct rq *rq)
         if (unlikely((s64)delta_exec < 0))
                 delta_exec = 0;
 
-        schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec));
+        schedstat_set(curr->se.statistics.exec_max,
+                      max(curr->se.statistics.exec_max, delta_exec));
 
         curr->se.sum_exec_runtime += delta_exec;
         account_group_exec_runtime(curr, delta_exec);