1 files changed, 108 insertions, 0 deletions

diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c
new file mode 100644
index 000000000000..45bddc0c1048
--- /dev/null
+++ b/kernel/sched_stoptask.c
@@ -0,0 +1,108 @@
+/*
+ * stop-task scheduling class.
+ *
+ * The stop task is the highest priority task in the system, it preempts
+ * everything and will be preempted by nothing.
+ *
+ * See kernel/stop_machine.c
+ */
+
+#ifdef CONFIG_SMP
+static int
+select_task_rq_stop(struct rq *rq, struct task_struct *p,
+                    int sd_flag, int flags)
+{
+        return task_cpu(p); /* stop tasks as never migrate */
+}
+#endif /* CONFIG_SMP */
+
+static void
+check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
+{
+        resched_task(rq->curr); /* we preempt everything */
+}
+
+static struct task_struct *pick_next_task_stop(struct rq *rq)
+{
+        struct task_struct *stop = rq->stop;
+
+        if (stop && stop->state == TASK_RUNNING)
+                return stop;
+
+        return NULL;
+}
+
+static void
+enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
+{
+}
+
+static void
+dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
+{
+}
+
+static void yield_task_stop(struct rq *rq)
+{
+        BUG(); /* the stop task should never yield, its pointless. */
+}
+
+static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
+{
+}
+
+static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
+{
+}
+
+static void set_curr_task_stop(struct rq *rq)
+{
+}
+
+static void switched_to_stop(struct rq *rq, struct task_struct *p,
+                             int running)
+{
+        BUG(); /* its impossible to change to this class */
+}
+
+static void prio_changed_stop(struct rq *rq, struct task_struct *p,
+                              int oldprio, int running)
+{
+        BUG(); /* how!?, what priority? */
+}
+
+static unsigned int
+get_rr_interval_stop(struct rq *rq, struct task_struct *task)
+{
+        return 0;
+}
+
+/*
+ * Simple, special scheduling class for the per-CPU stop tasks:
+ */
+static const struct sched_class stop_sched_class = {
+        .next                   = &rt_sched_class,
+
+        .enqueue_task           = enqueue_task_stop,
+        .dequeue_task           = dequeue_task_stop,
+        .yield_task             = yield_task_stop,
+
+        .check_preempt_curr     = check_preempt_curr_stop,
+
+        .pick_next_task         = pick_next_task_stop,
+        .put_prev_task          = put_prev_task_stop,
+
+#ifdef CONFIG_SMP
+        .select_task_rq         = select_task_rq_stop,
+#endif
+
+        .set_curr_task          = set_curr_task_stop,
+        .task_tick              = task_tick_stop,
+
+        .get_rr_interval        = get_rr_interval_stop,
+
+        .prio_changed           = prio_changed_stop,
+        .switched_to            = switched_to_stop,
+
+        /* no .task_new for stop tasks */
+};