sched: add CONFIG_SMP consistency
[linux-2.6.git] / kernel / sched_idletask.c
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
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  */
17 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int sync)
18 {
19         resched_task(rq->idle);
20 }
21
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
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
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
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
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
64 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
65 {
66 }
67
68 static void set_curr_task_idle(struct rq *rq)
69 {
70 }
71
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
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 };