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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
34f971f6 PZ |
2 | /* |
3 | * stop-task scheduling class. | |
4 | * | |
5 | * The stop task is the highest priority task in the system, it preempts | |
6 | * everything and will be preempted by nothing. | |
7 | * | |
8 | * See kernel/stop_machine.c | |
9 | */ | |
97fb7a0a | 10 | #include "sched.h" |
34f971f6 PZ |
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 | 26 | static struct task_struct * |
d8ac8971 | 27 | pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
34f971f6 PZ |
28 | { |
29 | struct task_struct *stop = rq->stop; | |
30 | ||
da0c1e65 | 31 | if (!stop || !task_on_rq_queued(stop)) |
606dba2e | 32 | return NULL; |
34f971f6 | 33 | |
3f1d2a31 | 34 | put_prev_task(rq, prev); |
606dba2e PZ |
35 | |
36 | stop->se.exec_start = rq_clock_task(rq); | |
37 | ||
38 | return stop; | |
34f971f6 PZ |
39 | } |
40 | ||
41 | static void | |
42 | enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
43 | { | |
72465447 | 44 | add_nr_running(rq, 1); |
34f971f6 PZ |
45 | } |
46 | ||
47 | static void | |
48 | dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
49 | { | |
72465447 | 50 | sub_nr_running(rq, 1); |
34f971f6 PZ |
51 | } |
52 | ||
53 | static void yield_task_stop(struct rq *rq) | |
54 | { | |
55 | BUG(); /* the stop task should never yield, its pointless. */ | |
56 | } | |
57 | ||
58 | static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) | |
59 | { | |
8f618968 MG |
60 | struct task_struct *curr = rq->curr; |
61 | u64 delta_exec; | |
62 | ||
78becc27 | 63 | delta_exec = rq_clock_task(rq) - curr->se.exec_start; |
8f618968 MG |
64 | if (unlikely((s64)delta_exec < 0)) |
65 | delta_exec = 0; | |
66 | ||
67 | schedstat_set(curr->se.statistics.exec_max, | |
68 | max(curr->se.statistics.exec_max, delta_exec)); | |
69 | ||
70 | curr->se.sum_exec_runtime += delta_exec; | |
71 | account_group_exec_runtime(curr, delta_exec); | |
72 | ||
78becc27 | 73 | curr->se.exec_start = rq_clock_task(rq); |
d2cc5ed6 | 74 | cgroup_account_cputime(curr, delta_exec); |
34f971f6 PZ |
75 | } |
76 | ||
d84b3131 FW |
77 | /* |
78 | * scheduler tick hitting a task of our scheduling class. | |
79 | * | |
80 | * NOTE: This function can be called remotely by the tick offload that | |
81 | * goes along full dynticks. Therefore no local assumption can be made | |
82 | * and everything must be accessed through the @rq and @curr passed in | |
83 | * parameters. | |
84 | */ | |
34f971f6 PZ |
85 | static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) |
86 | { | |
87 | } | |
88 | ||
89 | static void set_curr_task_stop(struct rq *rq) | |
90 | { | |
8f618968 MG |
91 | struct task_struct *stop = rq->stop; |
92 | ||
78becc27 | 93 | stop->se.exec_start = rq_clock_task(rq); |
34f971f6 PZ |
94 | } |
95 | ||
da7a735e | 96 | static void switched_to_stop(struct rq *rq, struct task_struct *p) |
34f971f6 PZ |
97 | { |
98 | BUG(); /* its impossible to change to this class */ | |
99 | } | |
100 | ||
da7a735e PZ |
101 | static void |
102 | prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) | |
34f971f6 PZ |
103 | { |
104 | BUG(); /* how!?, what priority? */ | |
105 | } | |
106 | ||
107 | static unsigned int | |
108 | get_rr_interval_stop(struct rq *rq, struct task_struct *task) | |
109 | { | |
110 | return 0; | |
111 | } | |
112 | ||
90e362f4 TG |
113 | static void update_curr_stop(struct rq *rq) |
114 | { | |
115 | } | |
116 | ||
34f971f6 PZ |
117 | /* |
118 | * Simple, special scheduling class for the per-CPU stop tasks: | |
119 | */ | |
029632fb | 120 | const struct sched_class stop_sched_class = { |
aab03e05 | 121 | .next = &dl_sched_class, |
34f971f6 PZ |
122 | |
123 | .enqueue_task = enqueue_task_stop, | |
124 | .dequeue_task = dequeue_task_stop, | |
125 | .yield_task = yield_task_stop, | |
126 | ||
127 | .check_preempt_curr = check_preempt_curr_stop, | |
128 | ||
129 | .pick_next_task = pick_next_task_stop, | |
130 | .put_prev_task = put_prev_task_stop, | |
131 | ||
132 | #ifdef CONFIG_SMP | |
133 | .select_task_rq = select_task_rq_stop, | |
c5b28038 | 134 | .set_cpus_allowed = set_cpus_allowed_common, |
34f971f6 PZ |
135 | #endif |
136 | ||
137 | .set_curr_task = set_curr_task_stop, | |
138 | .task_tick = task_tick_stop, | |
139 | ||
140 | .get_rr_interval = get_rr_interval_stop, | |
141 | ||
142 | .prio_changed = prio_changed_stop, | |
143 | .switched_to = switched_to_stop, | |
90e362f4 | 144 | .update_curr = update_curr_stop, |
34f971f6 | 145 | }; |