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,struct pin_cookie cookie)27 pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
28 {
29 put_prev_task(rq, prev);
30 update_idle_core(rq);
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 rq_last_tick_reset(rq);
51 }
52
task_tick_idle(struct rq * rq,struct task_struct * curr,int queued)53 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
54 {
55 }
56
set_curr_task_idle(struct rq * rq)57 static void set_curr_task_idle(struct rq *rq)
58 {
59 }
60
switched_to_idle(struct rq * rq,struct task_struct * p)61 static void switched_to_idle(struct rq *rq, struct task_struct *p)
62 {
63 BUG();
64 }
65
66 static void
prio_changed_idle(struct rq * rq,struct task_struct * p,int oldprio)67 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
68 {
69 BUG();
70 }
71
get_rr_interval_idle(struct rq * rq,struct task_struct * task)72 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
73 {
74 return 0;
75 }
76
update_curr_idle(struct rq * rq)77 static void update_curr_idle(struct rq *rq)
78 {
79 }
80
81 /*
82 * Simple, special scheduling class for the per-CPU idle tasks:
83 */
84 const struct sched_class idle_sched_class = {
85 /* .next is NULL */
86 /* no enqueue/yield_task for idle tasks */
87
88 /* dequeue is not valid, we print a debug message there: */
89 .dequeue_task = dequeue_task_idle,
90
91 .check_preempt_curr = check_preempt_curr_idle,
92
93 .pick_next_task = pick_next_task_idle,
94 .put_prev_task = put_prev_task_idle,
95
96 #ifdef CONFIG_SMP
97 .select_task_rq = select_task_rq_idle,
98 .set_cpus_allowed = set_cpus_allowed_common,
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