1#include "sched.h"
2
3/*
4 * idle-task scheduling class.
5 *
6 * (NOTE: these are not related to SCHED_IDLE tasks which are
7 *  handled in sched/fair.c)
8 */
9
10#ifdef CONFIG_SMP
11static int
12select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
13{
14	return task_cpu(p); /* IDLE tasks as never migrated */
15}
16#endif /* CONFIG_SMP */
17
18/*
19 * Idle tasks are unconditionally rescheduled:
20 */
21static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
22{
23	resched_curr(rq);
24}
25
26static struct task_struct *
27pick_next_task_idle(struct rq *rq, struct task_struct *prev)
28{
29	put_prev_task(rq, prev);
30
31	schedstat_inc(rq, sched_goidle);
32	return rq->idle;
33}
34
35/*
36 * It is not legal to sleep in the idle task - print a warning
37 * message if some code attempts to do it:
38 */
39static void
40dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
41{
42	raw_spin_unlock_irq(&rq->lock);
43	printk(KERN_ERR "bad: scheduling from the idle thread!\n");
44	dump_stack();
45	raw_spin_lock_irq(&rq->lock);
46}
47
48static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
49{
50	idle_exit_fair(rq);
51	rq_last_tick_reset(rq);
52}
53
54static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
55{
56}
57
58static void set_curr_task_idle(struct rq *rq)
59{
60}
61
62static void switched_to_idle(struct rq *rq, struct task_struct *p)
63{
64	BUG();
65}
66
67static void
68prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
69{
70	BUG();
71}
72
73static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
74{
75	return 0;
76}
77
78static void update_curr_idle(struct rq *rq)
79{
80}
81
82/*
83 * Simple, special scheduling class for the per-CPU idle tasks:
84 */
85const struct sched_class idle_sched_class = {
86	/* .next is NULL */
87	/* no enqueue/yield_task for idle tasks */
88
89	/* dequeue is not valid, we print a debug message there: */
90	.dequeue_task		= dequeue_task_idle,
91
92	.check_preempt_curr	= check_preempt_curr_idle,
93
94	.pick_next_task		= pick_next_task_idle,
95	.put_prev_task		= put_prev_task_idle,
96
97#ifdef CONFIG_SMP
98	.select_task_rq		= select_task_rq_idle,
99#endif
100
101	.set_curr_task          = set_curr_task_idle,
102	.task_tick		= task_tick_idle,
103
104	.get_rr_interval	= get_rr_interval_idle,
105
106	.prio_changed		= prio_changed_idle,
107	.switched_to		= switched_to_idle,
108	.update_curr		= update_curr_idle,
109};
110