sched: rt-group: fix RR buglet

In tick_task_rt() we first call update_curr_rt() which can dequeue a runqueue
due to it running out of runtime, and then we try to requeue it, of it also
having exhausted its RR quota. Obviously requeueing something that is no longer
on the runqueue will not have the expected result.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Daniel K. <dk@uw.no>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 837241568d76..1dad5bbb59b6 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -549,8 +549,10 @@ static
 void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
 {
         struct rt_prio_array *array = &rt_rq->active;
+        struct list_head *queue = array->queue + rt_se_prio(rt_se);
 
-        list_move_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
+        if (on_rt_rq(rt_se))
+                list_move_tail(&rt_se->run_list, queue);
 }
 
 static void requeue_task_rt(struct rq *rq, struct task_struct *p)