+static ATOMIC_NOTIFIER_HEAD(idle_notifier);
+
+void idle_notifier_register(struct notifier_block *n)
+{
+ atomic_notifier_chain_register(&idle_notifier, n);
+}
+
+void idle_notifier_unregister(struct notifier_block *n)
+{
+ atomic_notifier_chain_unregister(&idle_notifier, n);
+}
+
+static DEFINE_PER_CPU(volatile unsigned long, idle_state);
+
+void enter_idle(void)
+{
+ /* needs to be atomic w.r.t. interrupts, not against other CPUs */
+ __set_bit(0, &__get_cpu_var(idle_state));
+ atomic_notifier_call_chain(&idle_notifier, IDLE_START, NULL);
+}
+
+static void __exit_idle(void)
+{
+ /* needs to be atomic w.r.t. interrupts, not against other CPUs */
+ if (__test_and_clear_bit(0, &__get_cpu_var(idle_state)) == 0)
+ return;
+ atomic_notifier_call_chain(&idle_notifier, IDLE_END, NULL);
+}
+
+void exit_idle(void)
+{
+ if (current->pid)
+ return;
+ __exit_idle();
+}
+