Root/kernel/sched_stoptask.c

1/*
2 * stop-task scheduling class.
3 *
4 * The stop task is the highest priority task in the system, it preempts
5 * everything and will be preempted by nothing.
6 *
7 * See kernel/stop_machine.c
8 */
9
10#ifdef CONFIG_SMP
11static int
12select_task_rq_stop(struct task_struct *p, int sd_flag, int flags)
13{
14    return task_cpu(p); /* stop tasks as never migrate */
15}
16#endif /* CONFIG_SMP */
17
18static void
19check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
20{
21    /* we're never preempted */
22}
23
24static struct task_struct *pick_next_task_stop(struct rq *rq)
25{
26    struct task_struct *stop = rq->stop;
27
28    if (stop && stop->on_rq)
29        return stop;
30
31    return NULL;
32}
33
34static void
35enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
36{
37}
38
39static void
40dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
41{
42}
43
44static void yield_task_stop(struct rq *rq)
45{
46    BUG(); /* the stop task should never yield, its pointless. */
47}
48
49static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
50{
51}
52
53static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
54{
55}
56
57static void set_curr_task_stop(struct rq *rq)
58{
59}
60
61static void switched_to_stop(struct rq *rq, struct task_struct *p)
62{
63    BUG(); /* its impossible to change to this class */
64}
65
66static void
67prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
68{
69    BUG(); /* how!?, what priority? */
70}
71
72static unsigned int
73get_rr_interval_stop(struct rq *rq, struct task_struct *task)
74{
75    return 0;
76}
77
78/*
79 * Simple, special scheduling class for the per-CPU stop tasks:
80 */
81static const struct sched_class stop_sched_class = {
82    .next = &rt_sched_class,
83
84    .enqueue_task = enqueue_task_stop,
85    .dequeue_task = dequeue_task_stop,
86    .yield_task = yield_task_stop,
87
88    .check_preempt_curr = check_preempt_curr_stop,
89
90    .pick_next_task = pick_next_task_stop,
91    .put_prev_task = put_prev_task_stop,
92
93#ifdef CONFIG_SMP
94    .select_task_rq = select_task_rq_stop,
95#endif
96
97    .set_curr_task = set_curr_task_stop,
98    .task_tick = task_tick_stop,
99
100    .get_rr_interval = get_rr_interval_stop,
101
102    .prio_changed = prio_changed_stop,
103    .switched_to = switched_to_stop,
104};
105

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