Loading...
1#include "sched.h"
2
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
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 pin_cookie cookie)
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 cpuacct_charge(curr, delta_exec);
75}
76
77static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
78{
79}
80
81static void set_curr_task_stop(struct rq *rq)
82{
83 struct task_struct *stop = rq->stop;
84
85 stop->se.exec_start = rq_clock_task(rq);
86}
87
88static void switched_to_stop(struct rq *rq, struct task_struct *p)
89{
90 BUG(); /* its impossible to change to this class */
91}
92
93static void
94prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
95{
96 BUG(); /* how!?, what priority? */
97}
98
99static unsigned int
100get_rr_interval_stop(struct rq *rq, struct task_struct *task)
101{
102 return 0;
103}
104
105static void update_curr_stop(struct rq *rq)
106{
107}
108
109/*
110 * Simple, special scheduling class for the per-CPU stop tasks:
111 */
112const struct sched_class stop_sched_class = {
113 .next = &dl_sched_class,
114
115 .enqueue_task = enqueue_task_stop,
116 .dequeue_task = dequeue_task_stop,
117 .yield_task = yield_task_stop,
118
119 .check_preempt_curr = check_preempt_curr_stop,
120
121 .pick_next_task = pick_next_task_stop,
122 .put_prev_task = put_prev_task_stop,
123
124#ifdef CONFIG_SMP
125 .select_task_rq = select_task_rq_stop,
126 .set_cpus_allowed = set_cpus_allowed_common,
127#endif
128
129 .set_curr_task = set_curr_task_stop,
130 .task_tick = task_tick_stop,
131
132 .get_rr_interval = get_rr_interval_stop,
133
134 .prio_changed = prio_changed_stop,
135 .switched_to = switched_to_stop,
136 .update_curr = update_curr_stop,
137};
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 struct task_struct *pick_next_task_stop(struct rq *rq)
45{
46 struct task_struct *p = pick_task_stop(rq);
47
48 if (p)
49 set_next_task_stop(rq, p, true);
50
51 return p;
52}
53
54static void
55enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
56{
57 add_nr_running(rq, 1);
58}
59
60static void
61dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
62{
63 sub_nr_running(rq, 1);
64}
65
66static void yield_task_stop(struct rq *rq)
67{
68 BUG(); /* the stop task should never yield, its pointless. */
69}
70
71static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
72{
73 update_curr_common(rq);
74}
75
76/*
77 * scheduler tick hitting a task of our scheduling class.
78 *
79 * NOTE: This function can be called remotely by the tick offload that
80 * goes along full dynticks. Therefore no local assumption can be made
81 * and everything must be accessed through the @rq and @curr passed in
82 * parameters.
83 */
84static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
85{
86}
87
88static void switched_to_stop(struct rq *rq, struct task_struct *p)
89{
90 BUG(); /* its impossible to change to this class */
91}
92
93static void
94prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
95{
96 BUG(); /* how!?, what priority? */
97}
98
99static void update_curr_stop(struct rq *rq)
100{
101}
102
103/*
104 * Simple, special scheduling class for the per-CPU stop tasks:
105 */
106DEFINE_SCHED_CLASS(stop) = {
107
108 .enqueue_task = enqueue_task_stop,
109 .dequeue_task = dequeue_task_stop,
110 .yield_task = yield_task_stop,
111
112 .wakeup_preempt = wakeup_preempt_stop,
113
114 .pick_next_task = pick_next_task_stop,
115 .put_prev_task = put_prev_task_stop,
116 .set_next_task = set_next_task_stop,
117
118#ifdef CONFIG_SMP
119 .balance = balance_stop,
120 .pick_task = pick_task_stop,
121 .select_task_rq = select_task_rq_stop,
122 .set_cpus_allowed = set_cpus_allowed_common,
123#endif
124
125 .task_tick = task_tick_stop,
126
127 .prio_changed = prio_changed_stop,
128 .switched_to = switched_to_stop,
129 .update_curr = update_curr_stop,
130};