sched: Simplify the idle scheduling class
[linux-2.6.git] / kernel / sched_idletask.c
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
9 static int
10 select_task_rq_idle(struct rq *rq, 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  */
18 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
19 {
20         resched_task(rq->idle);
21 }
22
23 static 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  */
34 static void
35 dequeue_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
43 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
44 {
45 }
46
47 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
48 {
49 }
50
51 static void set_curr_task_idle(struct rq *rq)
52 {
53 }
54
55 static void
56 switched_to_idle(struct rq *rq, struct task_struct *p, int running)
57 {
58         BUG();
59 }
60
61 static void prio_changed_idle(struct rq *rq, struct task_struct *p,
62                               int oldprio, int running)
63 {
64         BUG();
65 }
66
67 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
68 {
69         return 0;
70 }
71
72 /*
73  * Simple, special scheduling class for the per-CPU idle tasks:
74  */
75 static const struct sched_class idle_sched_class = {
76         /* .next is NULL */
77         /* no enqueue/yield_task for idle tasks */
78
79         /* dequeue is not valid, we print a debug message there: */
80         .dequeue_task           = dequeue_task_idle,
81
82         .check_preempt_curr     = check_preempt_curr_idle,
83
84         .pick_next_task         = pick_next_task_idle,
85         .put_prev_task          = put_prev_task_idle,
86
87 #ifdef CONFIG_SMP
88         .select_task_rq         = select_task_rq_idle,
89 #endif
90
91         .set_curr_task          = set_curr_task_idle,
92         .task_tick              = task_tick_idle,
93
94         .get_rr_interval        = get_rr_interval_idle,
95
96         .prio_changed           = prio_changed_idle,
97         .switched_to            = switched_to_idle,
98
99         /* no .task_new for idle tasks */
100 };