tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * idle-task scheduling class.
3 *
4 * (NOTE: these are not related to SCHED_IDLE tasks which are
5 * handled in sched_fair.c)
6 */
7
8#ifdef CONFIG_SMP
9static int
10select_task_rq_idle(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
11{
12 return task_cpu(p); /* IDLE tasks as never migrated */
13}
14#endif /* CONFIG_SMP */
15/*
16 * Idle tasks are unconditionally rescheduled:
17 */
18static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
19{
20 resched_task(rq->idle);
21}
22
23static struct task_struct *pick_next_task_idle(struct rq *rq)
24{
25 schedstat_inc(rq, sched_goidle);
26 calc_load_account_idle(rq);
27 return rq->idle;
28}
29
30/*
31 * It is not legal to sleep in the idle task - print a warning
32 * message if some code attempts to do it:
33 */
34static void
35dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
36{
37 raw_spin_unlock_irq(&rq->lock);
38 printk(KERN_ERR "bad: scheduling from the idle thread!\n");
39 dump_stack();
40 raw_spin_lock_irq(&rq->lock);
41}
42
43static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
44{
45}
46
47static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
48{
49}
50
51static void set_curr_task_idle(struct rq *rq)
52{
53}
54
55static void switched_to_idle(struct rq *rq, struct task_struct *p,
56 int running)
57{
58 /* Can this actually happen?? */
59 if (running)
60 resched_task(rq->curr);
61 else
62 check_preempt_curr(rq, p, 0);
63}
64
65static void prio_changed_idle(struct rq *rq, struct task_struct *p,
66 int oldprio, int running)
67{
68 /* This can happen for hot plug CPUS */
69
70 /*
71 * Reschedule if we are currently running on this runqueue and
72 * our priority decreased, or if we are not currently running on
73 * this runqueue and our priority is higher than the current's
74 */
75 if (running) {
76 if (p->prio > oldprio)
77 resched_task(rq->curr);
78 } else
79 check_preempt_curr(rq, p, 0);
80}
81
82static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
83{
84 return 0;
85}
86
87/*
88 * Simple, special scheduling class for the per-CPU idle tasks:
89 */
90static const struct sched_class idle_sched_class = {
91 /* .next is NULL */
92 /* no enqueue/yield_task for idle tasks */
93
94 /* dequeue is not valid, we print a debug message there: */
95 .dequeue_task = dequeue_task_idle,
96
97 .check_preempt_curr = check_preempt_curr_idle,
98
99 .pick_next_task = pick_next_task_idle,
100 .put_prev_task = put_prev_task_idle,
101
102#ifdef CONFIG_SMP
103 .select_task_rq = select_task_rq_idle,
104#endif
105
106 .set_curr_task = set_curr_task_idle,
107 .task_tick = task_tick_idle,
108
109 .get_rr_interval = get_rr_interval_idle,
110
111 .prio_changed = prio_changed_idle,
112 .switched_to = switched_to_idle,
113
114 /* no .task_new for idle tasks */
115};