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
select_task_rq_idle(struct task_struct * p,int sync)9 static int select_task_rq_idle(struct task_struct *p, int sync)
10 {
11 return task_cpu(p); /* IDLE tasks as never migrated */
12 }
13 #endif /* CONFIG_SMP */
14 /*
15 * Idle tasks are unconditionally rescheduled:
16 */
check_preempt_curr_idle(struct rq * rq,struct task_struct * p,int sync)17 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int sync)
18 {
19 resched_task(rq->idle);
20 }
21
pick_next_task_idle(struct rq * rq)22 static struct task_struct *pick_next_task_idle(struct rq *rq)
23 {
24 schedstat_inc(rq, sched_goidle);
25
26 return rq->idle;
27 }
28
29 /*
30 * It is not legal to sleep in the idle task - print a warning
31 * message if some code attempts to do it:
32 */
33 static void
dequeue_task_idle(struct rq * rq,struct task_struct * p,int sleep)34 dequeue_task_idle(struct rq *rq, struct task_struct *p, int sleep)
35 {
36 spin_unlock_irq(&rq->lock);
37 printk(KERN_ERR "bad: scheduling from the idle thread!\n");
38 dump_stack();
39 spin_lock_irq(&rq->lock);
40 }
41
put_prev_task_idle(struct rq * rq,struct task_struct * prev)42 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
43 {
44 }
45
46 #ifdef CONFIG_SMP
47 static unsigned long
load_balance_idle(struct rq * this_rq,int this_cpu,struct rq * busiest,unsigned long max_load_move,struct sched_domain * sd,enum cpu_idle_type idle,int * all_pinned,int * this_best_prio)48 load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
49 unsigned long max_load_move,
50 struct sched_domain *sd, enum cpu_idle_type idle,
51 int *all_pinned, int *this_best_prio)
52 {
53 return 0;
54 }
55
56 static int
move_one_task_idle(struct rq * this_rq,int this_cpu,struct rq * busiest,struct sched_domain * sd,enum cpu_idle_type idle)57 move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
58 struct sched_domain *sd, enum cpu_idle_type idle)
59 {
60 return 0;
61 }
62 #endif
63
task_tick_idle(struct rq * rq,struct task_struct * curr,int queued)64 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
65 {
66 }
67
set_curr_task_idle(struct rq * rq)68 static void set_curr_task_idle(struct rq *rq)
69 {
70 }
71
switched_to_idle(struct rq * rq,struct task_struct * p,int running)72 static void switched_to_idle(struct rq *rq, struct task_struct *p,
73 int running)
74 {
75 /* Can this actually happen?? */
76 if (running)
77 resched_task(rq->curr);
78 else
79 check_preempt_curr(rq, p, 0);
80 }
81
prio_changed_idle(struct rq * rq,struct task_struct * p,int oldprio,int running)82 static void prio_changed_idle(struct rq *rq, struct task_struct *p,
83 int oldprio, int running)
84 {
85 /* This can happen for hot plug CPUS */
86
87 /*
88 * Reschedule if we are currently running on this runqueue and
89 * our priority decreased, or if we are not currently running on
90 * this runqueue and our priority is higher than the current's
91 */
92 if (running) {
93 if (p->prio > oldprio)
94 resched_task(rq->curr);
95 } else
96 check_preempt_curr(rq, p, 0);
97 }
98
99 /*
100 * Simple, special scheduling class for the per-CPU idle tasks:
101 */
102 static const struct sched_class idle_sched_class = {
103 /* .next is NULL */
104 /* no enqueue/yield_task for idle tasks */
105
106 /* dequeue is not valid, we print a debug message there: */
107 .dequeue_task = dequeue_task_idle,
108
109 .check_preempt_curr = check_preempt_curr_idle,
110
111 .pick_next_task = pick_next_task_idle,
112 .put_prev_task = put_prev_task_idle,
113
114 #ifdef CONFIG_SMP
115 .select_task_rq = select_task_rq_idle,
116
117 .load_balance = load_balance_idle,
118 .move_one_task = move_one_task_idle,
119 #endif
120
121 .set_curr_task = set_curr_task_idle,
122 .task_tick = task_tick_idle,
123
124 .prio_changed = prio_changed_idle,
125 .switched_to = switched_to_idle,
126
127 /* no .task_new for idle tasks */
128 };
129