Commit | Line | Data |
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34f971f6 PZ |
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 | |
11 | static int | |
12 | select_task_rq_stop(struct rq *rq, struct task_struct *p, | |
13 | int sd_flag, int flags) | |
14 | { | |
15 | return task_cpu(p); /* stop tasks as never migrate */ | |
16 | } | |
17 | #endif /* CONFIG_SMP */ | |
18 | ||
19 | static void | |
20 | check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags) | |
21 | { | |
1e5a7405 | 22 | /* we're never preempted */ |
34f971f6 PZ |
23 | } |
24 | ||
25 | static struct task_struct *pick_next_task_stop(struct rq *rq) | |
26 | { | |
27 | struct task_struct *stop = rq->stop; | |
28 | ||
2d467090 | 29 | if (stop && stop->se.on_rq) |
34f971f6 PZ |
30 | return stop; |
31 | ||
32 | return NULL; | |
33 | } | |
34 | ||
35 | static void | |
36 | enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
37 | { | |
38 | } | |
39 | ||
40 | static void | |
41 | dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
42 | { | |
43 | } | |
44 | ||
45 | static void yield_task_stop(struct rq *rq) | |
46 | { | |
47 | BUG(); /* the stop task should never yield, its pointless. */ | |
48 | } | |
49 | ||
50 | static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) | |
51 | { | |
52 | } | |
53 | ||
54 | static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) | |
55 | { | |
56 | } | |
57 | ||
58 | static void set_curr_task_stop(struct rq *rq) | |
59 | { | |
60 | } | |
61 | ||
da7a735e | 62 | static void switched_to_stop(struct rq *rq, struct task_struct *p) |
34f971f6 PZ |
63 | { |
64 | BUG(); /* its impossible to change to this class */ | |
65 | } | |
66 | ||
da7a735e PZ |
67 | static void |
68 | prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) | |
34f971f6 PZ |
69 | { |
70 | BUG(); /* how!?, what priority? */ | |
71 | } | |
72 | ||
73 | static unsigned int | |
74 | get_rr_interval_stop(struct rq *rq, struct task_struct *task) | |
75 | { | |
76 | return 0; | |
77 | } | |
78 | ||
79 | /* | |
80 | * Simple, special scheduling class for the per-CPU stop tasks: | |
81 | */ | |
82 | static const struct sched_class stop_sched_class = { | |
83 | .next = &rt_sched_class, | |
84 | ||
85 | .enqueue_task = enqueue_task_stop, | |
86 | .dequeue_task = dequeue_task_stop, | |
87 | .yield_task = yield_task_stop, | |
88 | ||
89 | .check_preempt_curr = check_preempt_curr_stop, | |
90 | ||
91 | .pick_next_task = pick_next_task_stop, | |
92 | .put_prev_task = put_prev_task_stop, | |
93 | ||
94 | #ifdef CONFIG_SMP | |
95 | .select_task_rq = select_task_rq_stop, | |
96 | #endif | |
97 | ||
98 | .set_curr_task = set_curr_task_stop, | |
99 | .task_tick = task_tick_stop, | |
100 | ||
101 | .get_rr_interval = get_rr_interval_stop, | |
102 | ||
103 | .prio_changed = prio_changed_stop, | |
104 | .switched_to = switched_to_stop, | |
34f971f6 | 105 | }; |