projects/linux·blob uaccess-cleanups · refs

119 lines · 2.6 KiB

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