summaryrefslogtreecommitdiff
path: root/kernel/sched/stop_task.c
blob: 7b386e86fd2352c1a0fef2be23672a9c8ef194db (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
#include "sched.h"

/*
 * stop-task scheduling class.
 *
 * The stop task is the highest priority task in the system, it preempts
 * everything and will be preempted by nothing.
 *
 * See kernel/stop_machine.c
 */

#ifdef CONFIG_SMP
static int
select_task_rq_stop(struct task_struct *p, int sd_flag, int flags)
{
	return task_cpu(p); /* stop tasks as never migrate */
}
#endif /* CONFIG_SMP */

static void
check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
{
	/* we're never preempted */
}

static struct task_struct *pick_next_task_stop(struct rq *rq)
{
	struct task_struct *stop = rq->stop;

	if (stop && stop->on_rq)
		return stop;

	return NULL;
}

static void
enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
	inc_nr_running(rq);
}

static void
dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
	dec_nr_running(rq);
}

static void yield_task_stop(struct rq *rq)
{
	BUG(); /* the stop task should never yield, its pointless. */
}

static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
{
}

static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
{
}

static void set_curr_task_stop(struct rq *rq)
{
}

static void switched_to_stop(struct rq *rq, struct task_struct *p)
{
	BUG(); /* its impossible to change to this class */
}

static void
prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
{
	BUG(); /* how!?, what priority? */
}

static unsigned int
get_rr_interval_stop(struct rq *rq, struct task_struct *task)
{
	return 0;
}

/*
 * Simple, special scheduling class for the per-CPU stop tasks:
 */
const struct sched_class stop_sched_class = {
	.next			= &rt_sched_class,

	.enqueue_task		= enqueue_task_stop,
	.dequeue_task		= dequeue_task_stop,
	.yield_task		= yield_task_stop,

	.check_preempt_curr	= check_preempt_curr_stop,

	.pick_next_task		= pick_next_task_stop,
	.put_prev_task		= put_prev_task_stop,

#ifdef CONFIG_SMP
	.select_task_rq		= select_task_rq_stop,
#endif

	.set_curr_task          = set_curr_task_stop,
	.task_tick		= task_tick_stop,

	.get_rr_interval	= get_rr_interval_stop,

	.prio_changed		= prio_changed_stop,
	.switched_to		= switched_to_stop,
};