67ad4e7f506a2509a0493138662c0fec7dc4d7fa
[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 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  */
21 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
22 {
23         resched_curr(rq);
24 }
25
26 static struct task_struct *
27 pick_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  */
39 static void
40 dequeue_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
48 static 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
54 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
55 {
56 }
57
58 static void set_curr_task_idle(struct rq *rq)
59 {
60 }
61
62 static void switched_to_idle(struct rq *rq, struct task_struct *p)
63 {
64         BUG();
65 }
66
67 static void
68 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
69 {
70         BUG();
71 }
72
73 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
74 {
75         return 0;
76 }
77
78 /*
79  * Simple, special scheduling class for the per-CPU idle tasks:
80  */
81 const struct sched_class idle_sched_class = {
82         /* .next is NULL */
83         /* no enqueue/yield_task for idle tasks */
84
85         /* dequeue is not valid, we print a debug message there: */
86         .dequeue_task           = dequeue_task_idle,
87
88         .check_preempt_curr     = check_preempt_curr_idle,
89
90         .pick_next_task         = pick_next_task_idle,
91         .put_prev_task          = put_prev_task_idle,
92
93 #ifdef CONFIG_SMP
94         .select_task_rq         = select_task_rq_idle,
95 #endif
96
97         .set_curr_task          = set_curr_task_idle,
98         .task_tick              = task_tick_idle,
99
100         .get_rr_interval        = get_rr_interval_idle,
101
102         .prio_changed           = prio_changed_idle,
103         .switched_to            = switched_to_idle,
104 };