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 cpu,int sd_flag,int flags)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 */
check_preempt_curr_idle(struct rq * rq,struct task_struct * p,int flags)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 *
pick_next_task_idle(struct rq * rq,struct task_struct * prev)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
dequeue_task_idle(struct rq * rq,struct task_struct * p,int flags)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
put_prev_task_idle(struct rq * rq,struct task_struct * prev)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
task_tick_idle(struct rq * rq,struct task_struct * curr,int queued)54 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
55 {
56 }
57
set_curr_task_idle(struct rq * rq)58 static void set_curr_task_idle(struct rq *rq)
59 {
60 }
61
switched_to_idle(struct rq * rq,struct task_struct * p)62 static void switched_to_idle(struct rq *rq, struct task_struct *p)
63 {
64 BUG();
65 }
66
67 static void
prio_changed_idle(struct rq * rq,struct task_struct * p,int oldprio)68 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
69 {
70 BUG();
71 }
72
get_rr_interval_idle(struct rq * rq,struct task_struct * task)73 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
74 {
75 return 0;
76 }
77
update_curr_idle(struct rq * rq)78 static void update_curr_idle(struct rq *rq)
79 {
80 }
81
82 /*
83 * Simple, special scheduling class for the per-CPU idle tasks:
84 */
85 const 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