Scheduler is now selectable in make menuconfig in kernel hacking.
[projects/modsched/linux.git] / kernel / sched / cfs / idle_task.c
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
11 static int
12 select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)
13 {
14         return task_cpu(p); /* IDLE tasks as never migrated */
15 }
16 #endif /* CONFIG_SMP */
17 /*
18  * Idle tasks are unconditionally rescheduled:
19  */
20 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
21 {
22         resched_task(rq->idle);
23 }
24
25 static struct task_struct *pick_next_task_idle(struct rq *rq)
26 {
27         schedstat_inc(rq, sched_goidle);
28         return rq->idle;
29 }
30
31 /*
32  * It is not legal to sleep in the idle task - print a warning
33  * message if some code attempts to do it:
34  */
35 static void
36 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
37 {
38         raw_spin_unlock_irq(&rq->lock);
39         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
40         dump_stack();
41         raw_spin_lock_irq(&rq->lock);
42 }
43
44 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
45 {
46 }
47
48 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
49 {
50 }
51
52 static void set_curr_task_idle(struct rq *rq)
53 {
54 }
55
56 static void switched_to_idle(struct rq *rq, struct task_struct *p)
57 {
58         BUG();
59 }
60
61 static void
62 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
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 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 };