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029632fb PZ |
1 | #include "sched.h" |
2 | ||
34f971f6 PZ |
3 | /* |
4 | * stop-task scheduling class. | |
5 | * | |
6 | * The stop task is the highest priority task in the system, it preempts | |
7 | * everything and will be preempted by nothing. | |
8 | * | |
9 | * See kernel/stop_machine.c | |
10 | */ | |
11 | ||
12 | #ifdef CONFIG_SMP | |
13 | static int | |
7608dec2 | 14 | select_task_rq_stop(struct task_struct *p, int sd_flag, int flags) |
34f971f6 PZ |
15 | { |
16 | return task_cpu(p); /* stop tasks as never migrate */ | |
17 | } | |
18 | #endif /* CONFIG_SMP */ | |
19 | ||
20 | static void | |
21 | check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags) | |
22 | { | |
1e5a7405 | 23 | /* we're never preempted */ |
34f971f6 PZ |
24 | } |
25 | ||
26 | static struct task_struct *pick_next_task_stop(struct rq *rq) | |
27 | { | |
28 | struct task_struct *stop = rq->stop; | |
29 | ||
fd2f4419 | 30 | if (stop && stop->on_rq) |
34f971f6 PZ |
31 | return stop; |
32 | ||
33 | return NULL; | |
34 | } | |
35 | ||
36 | static void | |
37 | enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
38 | { | |
953bfcd1 | 39 | inc_nr_running(rq); |
34f971f6 PZ |
40 | } |
41 | ||
42 | static void | |
43 | dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
44 | { | |
953bfcd1 | 45 | dec_nr_running(rq); |
34f971f6 PZ |
46 | } |
47 | ||
48 | static void yield_task_stop(struct rq *rq) | |
49 | { | |
50 | BUG(); /* the stop task should never yield, its pointless. */ | |
51 | } | |
52 | ||
53 | static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) | |
54 | { | |
55 | } | |
56 | ||
57 | static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) | |
58 | { | |
59 | } | |
60 | ||
61 | static void set_curr_task_stop(struct rq *rq) | |
62 | { | |
63 | } | |
64 | ||
da7a735e | 65 | static void switched_to_stop(struct rq *rq, struct task_struct *p) |
34f971f6 PZ |
66 | { |
67 | BUG(); /* its impossible to change to this class */ | |
68 | } | |
69 | ||
da7a735e PZ |
70 | static void |
71 | prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) | |
34f971f6 PZ |
72 | { |
73 | BUG(); /* how!?, what priority? */ | |
74 | } | |
75 | ||
76 | static unsigned int | |
77 | get_rr_interval_stop(struct rq *rq, struct task_struct *task) | |
78 | { | |
79 | return 0; | |
80 | } | |
81 | ||
82 | /* | |
83 | * Simple, special scheduling class for the per-CPU stop tasks: | |
84 | */ | |
029632fb | 85 | const struct sched_class stop_sched_class = { |
34f971f6 PZ |
86 | .next = &rt_sched_class, |
87 | ||
88 | .enqueue_task = enqueue_task_stop, | |
89 | .dequeue_task = dequeue_task_stop, | |
90 | .yield_task = yield_task_stop, | |
91 | ||
92 | .check_preempt_curr = check_preempt_curr_stop, | |
93 | ||
94 | .pick_next_task = pick_next_task_stop, | |
95 | .put_prev_task = put_prev_task_stop, | |
96 | ||
97 | #ifdef CONFIG_SMP | |
98 | .select_task_rq = select_task_rq_stop, | |
99 | #endif | |
100 | ||
101 | .set_curr_task = set_curr_task_stop, | |
102 | .task_tick = task_tick_stop, | |
103 | ||
104 | .get_rr_interval = get_rr_interval_stop, | |
105 | ||
106 | .prio_changed = prio_changed_stop, | |
107 | .switched_to = switched_to_stop, | |
34f971f6 | 108 | }; |