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