1/*
 2 * idle-task scheduling class.
 3 *
 4 * (NOTE: these are not related to SCHED_IDLE tasks which are
 5 *  handled in sched_fair.c)
 6 */
 7
 8#ifdef CONFIG_SMP
 9static int
10select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)
11{
12	return task_cpu(p); /* IDLE tasks as never migrated */
13}
14#endif /* CONFIG_SMP */
15/*
16 * Idle tasks are unconditionally rescheduled:
17 */
18static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
19{
20	resched_task(rq->idle);
21}
22
23static struct task_struct *pick_next_task_idle(struct rq *rq)
24{
25	schedstat_inc(rq, sched_goidle);
26	calc_load_account_idle(rq);
27	return rq->idle;
28}
29
30/*
31 * It is not legal to sleep in the idle task - print a warning
32 * message if some code attempts to do it:
33 */
34static void
35dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
36{
37	raw_spin_unlock_irq(&rq->lock);
38	printk(KERN_ERR "bad: scheduling from the idle thread!\n");
39	dump_stack();
40	raw_spin_lock_irq(&rq->lock);
41}
42
43static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
44{
45}
46
47static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
48{
49}
50
51static void set_curr_task_idle(struct rq *rq)
52{
53}
54
55static void switched_to_idle(struct rq *rq, struct task_struct *p)
56{
57	BUG();
58}
59
60static void
61prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
62{
63	BUG();
64}
65
66static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
67{
68	return 0;
69}
70
71/*
72 * Simple, special scheduling class for the per-CPU idle tasks:
73 */
74static const struct sched_class idle_sched_class = {
75	/* .next is NULL */
76	/* no enqueue/yield_task for idle tasks */
77
78	/* dequeue is not valid, we print a debug message there: */
79	.dequeue_task		= dequeue_task_idle,
80
81	.check_preempt_curr	= check_preempt_curr_idle,
82
83	.pick_next_task		= pick_next_task_idle,
84	.put_prev_task		= put_prev_task_idle,
85
86#ifdef CONFIG_SMP
87	.select_task_rq		= select_task_rq_idle,
88#endif
89
90	.set_curr_task          = set_curr_task_idle,
91	.task_tick		= task_tick_idle,
92
93	.get_rr_interval	= get_rr_interval_idle,
94
95	.prio_changed		= prio_changed_idle,
96	.switched_to		= switched_to_idle,
97};