Don't call set_tsk_need_resched() on remote LITMUS^RT task

This patch fixes a BUG_ON() in litmus/preempt.c:33 reported by Felipe
Cerqueira & Manohar Vanga.

1 files changed, 7 insertions, 2 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c202f946f54f..344855ef752d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -529,9 +529,14 @@ void resched_task(struct task_struct *p)
         if (test_tsk_need_resched(p))
                 return;
 
-        set_tsk_need_resched(p);
-
         cpu = task_cpu(p);
+
+        /* Cannot call set_tsk_need_resched() on LITMUS^RT task
+         * on remote core. Only policy plugins may do this via
+         * litmus_reschedule(). */
+        if (!is_realtime(p) || cpu == smp_processor_id())
+                set_tsk_need_resched(p);
+
         if (cpu == smp_processor_id())
                 return;