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
select_task_rq_idle(struct task_struct * p,int sd_flag,int flags)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 */
check_preempt_curr_idle(struct rq * rq,struct task_struct * p,int flags)20 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
21 {
22 resched_task(rq->idle);
23 }
24
pick_next_task_idle(struct rq * rq)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
dequeue_task_idle(struct rq * rq,struct task_struct * p,int flags)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
put_prev_task_idle(struct rq * rq,struct task_struct * prev)44 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
45 {
46 }
47
task_tick_idle(struct rq * rq,struct task_struct * curr,int queued)48 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
49 {
50 }
51
set_curr_task_idle(struct rq * rq)52 static void set_curr_task_idle(struct rq *rq)
53 {
54 }
55
switched_to_idle(struct rq * rq,struct task_struct * p)56 static void switched_to_idle(struct rq *rq, struct task_struct *p)
57 {
58 BUG();
59 }
60
61 static void
prio_changed_idle(struct rq * rq,struct task_struct * p,int oldprio)62 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
63 {
64 BUG();
65 }
66
get_rr_interval_idle(struct rq * rq,struct task_struct * task)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 };
99