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1// SPDX-License-Identifier: GPL-2.0
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 */
10#include "sched.h"
11
12#ifdef CONFIG_SMP
13static int
14select_task_rq_stop(struct task_struct *p, int cpu, int sd_flag, int flags)
15{
16 return task_cpu(p); /* stop tasks as never migrate */
17}
18
19static int
20balance_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
21{
22 return sched_stop_runnable(rq);
23}
24#endif /* CONFIG_SMP */
25
26static void
27check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
28{
29 /* we're never preempted */
30}
31
32static void set_next_task_stop(struct rq *rq, struct task_struct *stop)
33{
34 stop->se.exec_start = rq_clock_task(rq);
35}
36
37static struct task_struct *
38pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
39{
40 WARN_ON_ONCE(prev || rf);
41
42 if (!sched_stop_runnable(rq))
43 return NULL;
44
45 set_next_task_stop(rq, rq->stop);
46 return rq->stop;
47}
48
49static void
50enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
51{
52 add_nr_running(rq, 1);
53}
54
55static void
56dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
57{
58 sub_nr_running(rq, 1);
59}
60
61static void yield_task_stop(struct rq *rq)
62{
63 BUG(); /* the stop task should never yield, its pointless. */
64}
65
66static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
67{
68 struct task_struct *curr = rq->curr;
69 u64 delta_exec;
70
71 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
72 if (unlikely((s64)delta_exec < 0))
73 delta_exec = 0;
74
75 schedstat_set(curr->se.statistics.exec_max,
76 max(curr->se.statistics.exec_max, delta_exec));
77
78 curr->se.sum_exec_runtime += delta_exec;
79 account_group_exec_runtime(curr, delta_exec);
80
81 curr->se.exec_start = rq_clock_task(rq);
82 cgroup_account_cputime(curr, delta_exec);
83}
84
85/*
86 * scheduler tick hitting a task of our scheduling class.
87 *
88 * NOTE: This function can be called remotely by the tick offload that
89 * goes along full dynticks. Therefore no local assumption can be made
90 * and everything must be accessed through the @rq and @curr passed in
91 * parameters.
92 */
93static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
94{
95}
96
97static void switched_to_stop(struct rq *rq, struct task_struct *p)
98{
99 BUG(); /* its impossible to change to this class */
100}
101
102static void
103prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
104{
105 BUG(); /* how!?, what priority? */
106}
107
108static unsigned int
109get_rr_interval_stop(struct rq *rq, struct task_struct *task)
110{
111 return 0;
112}
113
114static void update_curr_stop(struct rq *rq)
115{
116}
117
118/*
119 * Simple, special scheduling class for the per-CPU stop tasks:
120 */
121const struct sched_class stop_sched_class = {
122 .next = &dl_sched_class,
123
124 .enqueue_task = enqueue_task_stop,
125 .dequeue_task = dequeue_task_stop,
126 .yield_task = yield_task_stop,
127
128 .check_preempt_curr = check_preempt_curr_stop,
129
130 .pick_next_task = pick_next_task_stop,
131 .put_prev_task = put_prev_task_stop,
132 .set_next_task = set_next_task_stop,
133
134#ifdef CONFIG_SMP
135 .balance = balance_stop,
136 .select_task_rq = select_task_rq_stop,
137 .set_cpus_allowed = set_cpus_allowed_common,
138#endif
139
140 .task_tick = task_tick_stop,
141
142 .get_rr_interval = get_rr_interval_stop,
143
144 .prio_changed = prio_changed_stop,
145 .switched_to = switched_to_stop,
146 .update_curr = update_curr_stop,
147};
1// SPDX-License-Identifier: GPL-2.0
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 */
10
11#ifdef CONFIG_SMP
12static int
13select_task_rq_stop(struct task_struct *p, int cpu, int flags)
14{
15 return task_cpu(p); /* stop tasks as never migrate */
16}
17
18static int
19balance_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
20{
21 return sched_stop_runnable(rq);
22}
23#endif /* CONFIG_SMP */
24
25static void
26wakeup_preempt_stop(struct rq *rq, struct task_struct *p, int flags)
27{
28 /* we're never preempted */
29}
30
31static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool first)
32{
33 stop->se.exec_start = rq_clock_task(rq);
34}
35
36static struct task_struct *pick_task_stop(struct rq *rq)
37{
38 if (!sched_stop_runnable(rq))
39 return NULL;
40
41 return rq->stop;
42}
43
44static void
45enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
46{
47 add_nr_running(rq, 1);
48}
49
50static bool
51dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
52{
53 sub_nr_running(rq, 1);
54 return true;
55}
56
57static void yield_task_stop(struct rq *rq)
58{
59 BUG(); /* the stop task should never yield, its pointless. */
60}
61
62static void put_prev_task_stop(struct rq *rq, struct task_struct *prev, struct task_struct *next)
63{
64 update_curr_common(rq);
65}
66
67/*
68 * scheduler tick hitting a task of our scheduling class.
69 *
70 * NOTE: This function can be called remotely by the tick offload that
71 * goes along full dynticks. Therefore no local assumption can be made
72 * and everything must be accessed through the @rq and @curr passed in
73 * parameters.
74 */
75static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
76{
77}
78
79static void switched_to_stop(struct rq *rq, struct task_struct *p)
80{
81 BUG(); /* its impossible to change to this class */
82}
83
84static void
85prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
86{
87 BUG(); /* how!?, what priority? */
88}
89
90static void update_curr_stop(struct rq *rq)
91{
92}
93
94/*
95 * Simple, special scheduling class for the per-CPU stop tasks:
96 */
97DEFINE_SCHED_CLASS(stop) = {
98
99 .enqueue_task = enqueue_task_stop,
100 .dequeue_task = dequeue_task_stop,
101 .yield_task = yield_task_stop,
102
103 .wakeup_preempt = wakeup_preempt_stop,
104
105 .pick_task = pick_task_stop,
106 .put_prev_task = put_prev_task_stop,
107 .set_next_task = set_next_task_stop,
108
109#ifdef CONFIG_SMP
110 .balance = balance_stop,
111 .select_task_rq = select_task_rq_stop,
112 .set_cpus_allowed = set_cpus_allowed_common,
113#endif
114
115 .task_tick = task_tick_stop,
116
117 .prio_changed = prio_changed_stop,
118 .switched_to = switched_to_stop,
119 .update_curr = update_curr_stop,
120};