1 files changed, 27 insertions, 0 deletions

diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c
index 938d52f80a2..9fb65628315 100644
--- a/kernel/sched_autogroup.c
+++ b/kernel/sched_autogroup.c
@@ -27,6 +27,11 @@ static inline void autogroup_destroy(struct kref *kref)
 {
         struct autogroup *ag = container_of(kref, struct autogroup, kref);
 
+#ifdef CONFIG_RT_GROUP_SCHED
+        /* We've redirected RT tasks to the root task group... */
+        ag->tg->rt_se = NULL;
+        ag->tg->rt_rq = NULL;
+#endif
         sched_destroy_group(ag->tg);
 }
 
@@ -55,6 +60,10 @@ static inline struct autogroup *autogroup_task_get(struct task_struct *p)
         return ag;
 }
 
+#ifdef CONFIG_RT_GROUP_SCHED
+static void free_rt_sched_group(struct task_group *tg);
+#endif
+
 static inline struct autogroup *autogroup_create(void)
 {
         struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
@@ -72,6 +81,19 @@ static inline struct autogroup *autogroup_create(void)
         init_rwsem(&ag->lock);
         ag->id = atomic_inc_return(&autogroup_seq_nr);
         ag->tg = tg;
+#ifdef CONFIG_RT_GROUP_SCHED
+        /*
+         * Autogroup RT tasks are redirected to the root task group
+         * so we don't have to move tasks around upon policy change,
+         * or flail around trying to allocate bandwidth on the fly.
+         * A bandwidth exception in __sched_setscheduler() allows
+         * the policy change to proceed.  Thereafter, task_group()
+         * returns &root_task_group, so zero bandwidth is required.
+         */
+        free_rt_sched_group(tg);
+        tg->rt_se = root_task_group.rt_se;
+        tg->rt_rq = root_task_group.rt_rq;
+#endif
         tg->autogroup = ag;
 
         return ag;
@@ -106,6 +128,11 @@ task_wants_autogroup(struct task_struct *p, struct task_group *tg)
         return true;
 }
 
+static inline bool task_group_is_autogroup(struct task_group *tg)
+{
+        return tg != &root_task_group && tg->autogroup;
+}
+
 static inline struct task_group *
 autogroup_task_group(struct task_struct *p, struct task_group *tg)
 {