Commit | Line | Data |
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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 | ||
03b7fad1 PZ |
26 | static void set_next_task_stop(struct rq *rq, struct task_struct *stop) |
27 | { | |
28 | stop->se.exec_start = rq_clock_task(rq); | |
29 | } | |
30 | ||
606dba2e | 31 | static struct task_struct * |
d8ac8971 | 32 | pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
34f971f6 PZ |
33 | { |
34 | struct task_struct *stop = rq->stop; | |
35 | ||
67692435 PZ |
36 | WARN_ON_ONCE(prev || rf); |
37 | ||
da0c1e65 | 38 | if (!stop || !task_on_rq_queued(stop)) |
606dba2e | 39 | return NULL; |
34f971f6 | 40 | |
03b7fad1 | 41 | set_next_task_stop(rq, stop); |
606dba2e PZ |
42 | |
43 | return stop; | |
34f971f6 PZ |
44 | } |
45 | ||
46 | static void | |
47 | enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
48 | { | |
72465447 | 49 | add_nr_running(rq, 1); |
34f971f6 PZ |
50 | } |
51 | ||
52 | static void | |
53 | dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) | |
54 | { | |
72465447 | 55 | sub_nr_running(rq, 1); |
34f971f6 PZ |
56 | } |
57 | ||
58 | static void yield_task_stop(struct rq *rq) | |
59 | { | |
60 | BUG(); /* the stop task should never yield, its pointless. */ | |
61 | } | |
62 | ||
5f2a45fc | 63 | static void put_prev_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
34f971f6 | 64 | { |
8f618968 MG |
65 | struct task_struct *curr = rq->curr; |
66 | u64 delta_exec; | |
67 | ||
78becc27 | 68 | delta_exec = rq_clock_task(rq) - curr->se.exec_start; |
8f618968 MG |
69 | if (unlikely((s64)delta_exec < 0)) |
70 | delta_exec = 0; | |
71 | ||
72 | schedstat_set(curr->se.statistics.exec_max, | |
73 | max(curr->se.statistics.exec_max, delta_exec)); | |
74 | ||
75 | curr->se.sum_exec_runtime += delta_exec; | |
76 | account_group_exec_runtime(curr, delta_exec); | |
77 | ||
78becc27 | 78 | curr->se.exec_start = rq_clock_task(rq); |
d2cc5ed6 | 79 | cgroup_account_cputime(curr, delta_exec); |
34f971f6 PZ |
80 | } |
81 | ||
d84b3131 FW |
82 | /* |
83 | * scheduler tick hitting a task of our scheduling class. | |
84 | * | |
85 | * NOTE: This function can be called remotely by the tick offload that | |
86 | * goes along full dynticks. Therefore no local assumption can be made | |
87 | * and everything must be accessed through the @rq and @curr passed in | |
88 | * parameters. | |
89 | */ | |
34f971f6 PZ |
90 | static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) |
91 | { | |
92 | } | |
93 | ||
da7a735e | 94 | static void switched_to_stop(struct rq *rq, struct task_struct *p) |
34f971f6 PZ |
95 | { |
96 | BUG(); /* its impossible to change to this class */ | |
97 | } | |
98 | ||
da7a735e PZ |
99 | static void |
100 | prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) | |
34f971f6 PZ |
101 | { |
102 | BUG(); /* how!?, what priority? */ | |
103 | } | |
104 | ||
105 | static unsigned int | |
106 | get_rr_interval_stop(struct rq *rq, struct task_struct *task) | |
107 | { | |
108 | return 0; | |
109 | } | |
110 | ||
90e362f4 TG |
111 | static void update_curr_stop(struct rq *rq) |
112 | { | |
113 | } | |
114 | ||
34f971f6 PZ |
115 | /* |
116 | * Simple, special scheduling class for the per-CPU stop tasks: | |
117 | */ | |
029632fb | 118 | const struct sched_class stop_sched_class = { |
aab03e05 | 119 | .next = &dl_sched_class, |
34f971f6 PZ |
120 | |
121 | .enqueue_task = enqueue_task_stop, | |
122 | .dequeue_task = dequeue_task_stop, | |
123 | .yield_task = yield_task_stop, | |
124 | ||
125 | .check_preempt_curr = check_preempt_curr_stop, | |
126 | ||
127 | .pick_next_task = pick_next_task_stop, | |
128 | .put_prev_task = put_prev_task_stop, | |
03b7fad1 | 129 | .set_next_task = set_next_task_stop, |
34f971f6 PZ |
130 | |
131 | #ifdef CONFIG_SMP | |
132 | .select_task_rq = select_task_rq_stop, | |
c5b28038 | 133 | .set_cpus_allowed = set_cpus_allowed_common, |
34f971f6 PZ |
134 | #endif |
135 | ||
34f971f6 PZ |
136 | .task_tick = task_tick_stop, |
137 | ||
138 | .get_rr_interval = get_rr_interval_stop, | |
139 | ||
140 | .prio_changed = prio_changed_stop, | |
141 | .switched_to = switched_to_stop, | |
90e362f4 | 142 | .update_curr = update_curr_stop, |
34f971f6 | 143 | }; |