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Commit | Line | Data |
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1 | /* | |
2 | * idle-task scheduling class. | |
3 | * | |
4 | * (NOTE: these are not related to SCHED_IDLE tasks which are | |
5 | * handled in sched_fair.c) | |
6 | */ | |
7 | ||
8 | #ifdef CONFIG_SMP | |
9 | static int | |
10 | select_task_rq_idle(struct rq *rq, struct task_struct *p, int sd_flag, int flags) | |
11 | { | |
12 | return task_cpu(p); /* IDLE tasks as never migrated */ | |
13 | } | |
14 | #endif /* CONFIG_SMP */ | |
15 | /* | |
16 | * Idle tasks are unconditionally rescheduled: | |
17 | */ | |
18 | static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags) | |
19 | { | |
20 | resched_task(rq->idle); | |
21 | } | |
22 | ||
23 | static struct task_struct *pick_next_task_idle(struct rq *rq) | |
24 | { | |
25 | schedstat_inc(rq, sched_goidle); | |
26 | calc_load_account_idle(rq); | |
27 | return rq->idle; | |
28 | } | |
29 | ||
30 | /* | |
31 | * It is not legal to sleep in the idle task - print a warning | |
32 | * message if some code attempts to do it: | |
33 | */ | |
34 | static void | |
35 | dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags) | |
36 | { | |
37 | raw_spin_unlock_irq(&rq->lock); | |
38 | printk(KERN_ERR "bad: scheduling from the idle thread!\n"); | |
39 | dump_stack(); | |
40 | raw_spin_lock_irq(&rq->lock); | |
41 | } | |
42 | ||
43 | static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) | |
44 | { | |
45 | } | |
46 | ||
47 | static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) | |
48 | { | |
49 | } | |
50 | ||
51 | static void set_curr_task_idle(struct rq *rq) | |
52 | { | |
53 | } | |
54 | ||
55 | static void switched_to_idle(struct rq *rq, struct task_struct *p, | |
56 | int running) | |
57 | { | |
58 | /* Can this actually happen?? */ | |
59 | if (running) | |
60 | resched_task(rq->curr); | |
61 | else | |
62 | check_preempt_curr(rq, p, 0); | |
63 | } | |
64 | ||
65 | static void prio_changed_idle(struct rq *rq, struct task_struct *p, | |
66 | int oldprio, int running) | |
67 | { | |
68 | /* This can happen for hot plug CPUS */ | |
69 | ||
70 | /* | |
71 | * Reschedule if we are currently running on this runqueue and | |
72 | * our priority decreased, or if we are not currently running on | |
73 | * this runqueue and our priority is higher than the current's | |
74 | */ | |
75 | if (running) { | |
76 | if (p->prio > oldprio) | |
77 | resched_task(rq->curr); | |
78 | } else | |
79 | check_preempt_curr(rq, p, 0); | |
80 | } | |
81 | ||
82 | static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task) | |
83 | { | |
84 | return 0; | |
85 | } | |
86 | ||
87 | /* | |
88 | * Simple, special scheduling class for the per-CPU idle tasks: | |
89 | */ | |
90 | static const struct sched_class idle_sched_class = { | |
91 | /* .next is NULL */ | |
92 | /* no enqueue/yield_task for idle tasks */ | |
93 | ||
94 | /* dequeue is not valid, we print a debug message there: */ | |
95 | .dequeue_task = dequeue_task_idle, | |
96 | ||
97 | .check_preempt_curr = check_preempt_curr_idle, | |
98 | ||
99 | .pick_next_task = pick_next_task_idle, | |
100 | .put_prev_task = put_prev_task_idle, | |
101 | ||
102 | #ifdef CONFIG_SMP | |
103 | .select_task_rq = select_task_rq_idle, | |
104 | #endif | |
105 | ||
106 | .set_curr_task = set_curr_task_idle, | |
107 | .task_tick = task_tick_idle, | |
108 | ||
109 | .get_rr_interval = get_rr_interval_idle, | |
110 | ||
111 | .prio_changed = prio_changed_idle, | |
112 | .switched_to = switched_to_idle, | |
113 | ||
114 | /* no .task_new for idle tasks */ | |
115 | }; |