Integrate LITMUS^RT with try_to_wake_up() path

1 files changed, 19 insertions, 1 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8c23af255271..42b4e32ec494 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1635,7 +1635,12 @@ static void ttwu_queue(struct task_struct *p, int cpu)
         struct rq *rq = cpu_rq(cpu);
 
 #if defined(CONFIG_SMP)
-        if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
+        /*
+         * LITMUS^RT: whether to send an IPI to the remote CPU is plugin
+         * specific.
+         */
+        if (!is_realtime(p) &&
+            sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
                 sched_clock_cpu(cpu); /* sync clocks x-cpu */
                 ttwu_queue_remote(p, cpu);
                 return;
@@ -1668,6 +1673,9 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
         unsigned long flags;
         int cpu, success = 0;
 
+        if (is_realtime(p))
+                TRACE_TASK(p, "try_to_wake_up() state:%d\n", p->state);
+
         /*
          * If we are going to wake up a thread waiting for CONDITION we
          * need to ensure that CONDITION=1 done by the caller can not be
@@ -1697,6 +1705,12 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
          */
         smp_rmb();
 
+        /* LITMUS^RT: once the task can be safely referenced by this
+         * CPU, don't mess with Linux load balancing stuff.
+         */
+        if (is_realtime(p))
+                goto litmus_out_activate;
+
         p->sched_contributes_to_load = !!task_contributes_to_load(p);
         p->state = TASK_WAKING;
 
@@ -1708,12 +1722,16 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
                 wake_flags |= WF_MIGRATED;
                 set_task_cpu(p, cpu);
         }
+
+litmus_out_activate:
 #endif /* CONFIG_SMP */
 
         ttwu_queue(p, cpu);
 stat:
         ttwu_stat(p, cpu, wake_flags);
 out:
+        if (is_realtime(p))
+                TRACE_TASK(p, "try_to_wake_up() done state:%d\n", p->state);
         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
 
         return success;