1 files changed, 25 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 759f4bd52cd6..803c3bc274c4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3502,6 +3502,31 @@ asmlinkage __visible void __sched schedule(void)
 }
 EXPORT_SYMBOL(schedule);
 
+/*
+ * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
+ * state (have scheduled out non-voluntarily) by making sure that all
+ * tasks have either left the run queue or have gone into user space.
+ * As idle tasks do not do either, they must not ever be preempted
+ * (schedule out non-voluntarily).
+ *
+ * schedule_idle() is similar to schedule_preempt_disable() except that it
+ * never enables preemption because it does not call sched_submit_work().
+ */
+void __sched schedule_idle(void)
+{
+        /*
+         * As this skips calling sched_submit_work(), which the idle task does
+         * regardless because that function is a nop when the task is in a
+         * TASK_RUNNING state, make sure this isn't used someplace that the
+         * current task can be in any other state. Note, idle is always in the
+         * TASK_RUNNING state.
+         */
+        WARN_ON_ONCE(current->state);
+        do {
+                __schedule(false);
+        } while (need_resched());
+}
+
 #ifdef CONFIG_CONTEXT_TRACKING
 asmlinkage __visible void __sched schedule_user(void)
 {