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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 | |
ac66f547 | 14 | select_task_rq_stop(struct task_struct *p, int cpu, 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 | ||
606dba2e PZ |
26 | static struct task_struct * |
27 | pick_next_task_stop(struct rq *rq, struct task_struct *prev) | |
34f971f6 PZ |
28 | { |
29 | struct task_struct *stop = rq->stop; | |
30 | ||
606dba2e PZ |
31 | if (!stop || !stop->on_rq) |
32 | return NULL; | |
34f971f6 | 33 | |
606dba2e PZ |
34 | if (prev) |
35 | prev->sched_class->put_prev_task(rq, prev); | |
36 | ||
37 | stop->se.exec_start = rq_clock_task(rq); | |
38 | ||
39 | return stop; | |
34f971f6 PZ |
40 | } |
41 | ||
42 | static void | |
43 | enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
44 | { | |
953bfcd1 | 45 | inc_nr_running(rq); |
34f971f6 PZ |
46 | } |
47 | ||
48 | static void | |
49 | dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
50 | { | |
953bfcd1 | 51 | dec_nr_running(rq); |
34f971f6 PZ |
52 | } |
53 | ||
54 | static void yield_task_stop(struct rq *rq) | |
55 | { | |
56 | BUG(); /* the stop task should never yield, its pointless. */ | |
57 | } | |
58 | ||
59 | static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) | |
60 | { | |
8f618968 MG |
61 | struct task_struct *curr = rq->curr; |
62 | u64 delta_exec; | |
63 | ||
78becc27 | 64 | delta_exec = rq_clock_task(rq) - curr->se.exec_start; |
8f618968 MG |
65 | if (unlikely((s64)delta_exec < 0)) |
66 | delta_exec = 0; | |
67 | ||
68 | schedstat_set(curr->se.statistics.exec_max, | |
69 | max(curr->se.statistics.exec_max, delta_exec)); | |
70 | ||
71 | curr->se.sum_exec_runtime += delta_exec; | |
72 | account_group_exec_runtime(curr, delta_exec); | |
73 | ||
78becc27 | 74 | curr->se.exec_start = rq_clock_task(rq); |
8f618968 | 75 | cpuacct_charge(curr, delta_exec); |
34f971f6 PZ |
76 | } |
77 | ||
78 | static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) | |
79 | { | |
80 | } | |
81 | ||
82 | static void set_curr_task_stop(struct rq *rq) | |
83 | { | |
8f618968 MG |
84 | struct task_struct *stop = rq->stop; |
85 | ||
78becc27 | 86 | stop->se.exec_start = rq_clock_task(rq); |
34f971f6 PZ |
87 | } |
88 | ||
da7a735e | 89 | static void switched_to_stop(struct rq *rq, struct task_struct *p) |
34f971f6 PZ |
90 | { |
91 | BUG(); /* its impossible to change to this class */ | |
92 | } | |
93 | ||
da7a735e PZ |
94 | static void |
95 | prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) | |
34f971f6 PZ |
96 | { |
97 | BUG(); /* how!?, what priority? */ | |
98 | } | |
99 | ||
100 | static unsigned int | |
101 | get_rr_interval_stop(struct rq *rq, struct task_struct *task) | |
102 | { | |
103 | return 0; | |
104 | } | |
105 | ||
106 | /* | |
107 | * Simple, special scheduling class for the per-CPU stop tasks: | |
108 | */ | |
029632fb | 109 | const struct sched_class stop_sched_class = { |
aab03e05 | 110 | .next = &dl_sched_class, |
34f971f6 PZ |
111 | |
112 | .enqueue_task = enqueue_task_stop, | |
113 | .dequeue_task = dequeue_task_stop, | |
114 | .yield_task = yield_task_stop, | |
115 | ||
116 | .check_preempt_curr = check_preempt_curr_stop, | |
117 | ||
118 | .pick_next_task = pick_next_task_stop, | |
119 | .put_prev_task = put_prev_task_stop, | |
120 | ||
121 | #ifdef CONFIG_SMP | |
122 | .select_task_rq = select_task_rq_stop, | |
123 | #endif | |
124 | ||
125 | .set_curr_task = set_curr_task_stop, | |
126 | .task_tick = task_tick_stop, | |
127 | ||
128 | .get_rr_interval = get_rr_interval_stop, | |
129 | ||
130 | .prio_changed = prio_changed_stop, | |
131 | .switched_to = switched_to_stop, | |
34f971f6 | 132 | }; |