2 files changed, 40 insertions, 30 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index cc1d558406f8..5b307da827ef 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7697,7 +7697,6 @@ static void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
         else
                 rt_se->rt_rq = parent->my_q;
 
-        rt_se->rt_rq = &rq->rt;
         rt_se->my_q = rt_rq;
         rt_se->parent = parent;
         INIT_LIST_HEAD(&rt_se->run_list);
@@ -8420,7 +8419,7 @@ static unsigned long to_ratio(u64 period, u64 runtime)
 #ifdef CONFIG_CGROUP_SCHED
 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
 {
-        struct task_group *tgi, *parent = tg->parent;
+        struct task_group *tgi, *parent = tg ? tg->parent : NULL;
         unsigned long total = 0;
 
         if (!parent) {
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index f721b52acd8d..fee5fa7c72db 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -571,14 +571,20 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 #endif
 }
 
-static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
+static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
 {
         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
         struct rt_prio_array *array = &rt_rq->active;
         struct rt_rq *group_rq = group_rt_rq(rt_se);
         struct list_head *queue = array->queue + rt_se_prio(rt_se);
 
-        if (group_rq && rt_rq_throttled(group_rq))
+        /*
+         * Don't enqueue the group if its throttled, or when empty.
+         * The latter is a consequence of the former when a child group
+         * get throttled and the current group doesn't have any other
+         * active members.
+         */
+        if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
                 return;
 
         if (rt_se->nr_cpus_allowed == 1)
@@ -591,7 +597,7 @@ static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
         inc_rt_tasks(rt_se, rt_rq);
 }
 
-static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
+static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
 {
         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
         struct rt_prio_array *array = &rt_rq->active;
@@ -607,11 +613,10 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
  * Because the prio of an upper entry depends on the lower
  * entries, we must remove entries top - down.
  */
-static void dequeue_rt_stack(struct task_struct *p)
+static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
 {
-        struct sched_rt_entity *rt_se, *back = NULL;
+        struct sched_rt_entity *back = NULL;
 
-        rt_se = &p->rt;
         for_each_sched_rt_entity(rt_se) {
                 rt_se->back = back;
                 back = rt_se;
@@ -619,7 +624,26 @@ static void dequeue_rt_stack(struct task_struct *p)
 
         for (rt_se = back; rt_se; rt_se = rt_se->back) {
                 if (on_rt_rq(rt_se))
-                        dequeue_rt_entity(rt_se);
+                        __dequeue_rt_entity(rt_se);
+        }
+}
+
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
+{
+        dequeue_rt_stack(rt_se);
+        for_each_sched_rt_entity(rt_se)
+                __enqueue_rt_entity(rt_se);
+}
+
+static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
+{
+        dequeue_rt_stack(rt_se);
+
+        for_each_sched_rt_entity(rt_se) {
+                struct rt_rq *rt_rq = group_rt_rq(rt_se);
+
+                if (rt_rq && rt_rq->rt_nr_running)
+                        __enqueue_rt_entity(rt_se);
         }
 }
 
@@ -633,32 +657,15 @@ static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
         if (wakeup)
                 rt_se->timeout = 0;
 
-        dequeue_rt_stack(p);
-
-        /*
-         * enqueue everybody, bottom - up.
-         */
-        for_each_sched_rt_entity(rt_se)
-                enqueue_rt_entity(rt_se);
+        enqueue_rt_entity(rt_se);
 }
 
 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
 {
         struct sched_rt_entity *rt_se = &p->rt;
-        struct rt_rq *rt_rq;
 
         update_curr_rt(rq);
-
-        dequeue_rt_stack(p);
-
-        /*
-         * re-enqueue all non-empty rt_rq entities.
-         */
-        for_each_sched_rt_entity(rt_se) {
-                rt_rq = group_rt_rq(rt_se);
-                if (rt_rq && rt_rq->rt_nr_running)
-                        enqueue_rt_entity(rt_se);
-        }
+        dequeue_rt_entity(rt_se);
 }
 
 /*
@@ -669,9 +676,13 @@ 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_del_init(&rt_se->run_list);
-        list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
+        if (on_rt_rq(rt_se)) {
+                list_del_init(&rt_se->run_list);
+                list_add_tail(&rt_se->run_list,
+                              array->queue + rt_se_prio(rt_se));
+        }
 }
 
 static void requeue_task_rt(struct rq *rq, struct task_struct *p)