Hook into SCHED_DEADLINE to protect LITMUS^RT tasks

SCHED_DEADLINE should not preempt LITMUS^RT tasks, as the LITMUS^RT
scheduling class is positioned above the SCHED_DEADLINE policy.

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 5e95145088fd..089331a5236b 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -16,6 +16,8 @@
  */
 #include "sched.h"
 
+#include <litmus/litmus.h>
+
 #include <linux/slab.h>
 
 struct dl_bandwidth def_dl_bandwidth;
@@ -615,14 +617,14 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
         enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
         if (dl_task(rq->curr))
                 check_preempt_curr_dl(rq, p, 0);
-        else
+        else if (!is_realtime(rq->curr))
                 resched_curr(rq);
 #ifdef CONFIG_SMP
         /*
          * Queueing this task back might have overloaded rq,
          * check if we need to kick someone away.
          */
-        if (has_pushable_dl_tasks(rq))
+        if (has_pushable_dl_tasks(rq) && is_realtime(rq->curr))
                 push_dl_task(rq);
 #endif
 unlock:
@@ -1710,7 +1712,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
         if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
                 return;
 
-        if (pull_dl_task(rq))
+        if (pull_dl_task(rq) && !is_realtime(rq->curr))
                 resched_curr(rq);
 }
 
@@ -1722,7 +1724,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
         int check_resched = 1;
 
-        if (task_on_rq_queued(p) && rq->curr != p) {
+        if (task_on_rq_queued(p) && rq->curr != p && !is_realtime(rq->curr)) {
 #ifdef CONFIG_SMP
                 if (p->nr_cpus_allowed > 1 && rq->dl.overloaded &&
                         push_dl_task(rq) && rq != task_rq(p))