sched: rt-group: refure unrunnable tasks

Refuse to accept or create RT tasks in groups that can't run them.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 15 insertions, 0 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index d2f4398c5e6f..f28f19e65b59 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4584,6 +4584,15 @@ recheck:
                         return -EPERM;
         }
 
+#ifdef CONFIG_RT_GROUP_SCHED
+        /*
+         * Do not allow realtime tasks into groups that have no runtime
+         * assigned.
+         */
+        if (rt_policy(policy) && task_group(p)->rt_runtime == 0)
+                return -EPERM;
+#endif
+
         retval = security_task_setscheduler(p, policy, param);
         if (retval)
                 return retval;
@@ -8028,9 +8037,15 @@ static int
 cpu_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
                       struct task_struct *tsk)
 {
+#ifdef CONFIG_RT_GROUP_SCHED
+        /* Don't accept realtime tasks when there is no way for them to run */
+        if (rt_task(tsk) && cgroup_tg(cgrp)->rt_runtime == 0)
+                return -EINVAL;
+#else
         /* We don't support RT-tasks being in separate groups */
         if (tsk->sched_class != &fair_sched_class)
                 return -EINVAL;
+#endif
 
         return 0;
 }