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 calc_load_account_idle(rq);
29 return rq->idle;
30 }
31
32 /*
33 * It is not legal to sleep in the idle task - print a warning
34 * message if some code attempts to do it:
35 */
36 static void
dequeue_task_idle(struct rq * rq,struct task_struct * p,int flags)37 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
38 {
39 raw_spin_unlock_irq(&rq->lock);
40 printk(KERN_ERR "bad: scheduling from the idle thread!\n");
41 dump_stack();
42 raw_spin_lock_irq(&rq->lock);
43 }
44
put_prev_task_idle(struct rq * rq,struct task_struct * prev)45 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
46 {
47 }
48
task_tick_idle(struct rq * rq,struct task_struct * curr,int queued)49 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
50 {
51 }
52
set_curr_task_idle(struct rq * rq)53 static void set_curr_task_idle(struct rq *rq)
54 {
55 }
56
switched_to_idle(struct rq * rq,struct task_struct * p)57 static void switched_to_idle(struct rq *rq, struct task_struct *p)
58 {
59 BUG();
60 }
61
62 static void
prio_changed_idle(struct rq * rq,struct task_struct * p,int oldprio)63 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
64 {
65 BUG();
66 }
67
get_rr_interval_idle(struct rq * rq,struct task_struct * task)68 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
69 {
70 return 0;
71 }
72
73 /*
74 * Simple, special scheduling class for the per-CPU idle tasks:
75 */
76 const struct sched_class idle_sched_class = {
77 /* .next is NULL */
78 /* no enqueue/yield_task for idle tasks */
79
80 /* dequeue is not valid, we print a debug message there: */
81 .dequeue_task = dequeue_task_idle,
82
83 .check_preempt_curr = check_preempt_curr_idle,
84
85 .pick_next_task = pick_next_task_idle,
86 .put_prev_task = put_prev_task_idle,
87
88 #ifdef CONFIG_SMP
89 .select_task_rq = select_task_rq_idle,
90 #endif
91
92 .set_curr_task = set_curr_task_idle,
93 .task_tick = task_tick_idle,
94
95 .get_rr_interval = get_rr_interval_idle,
96
97 .prio_changed = prio_changed_idle,
98 .switched_to = switched_to_idle,
99 };
100