| 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 |
| 10 | select_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 | */ |
| 18 | static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags) |
| 19 | { |
| 20 | resched_task(rq->idle); |
| 21 | } |
| 22 | |
| 23 | static 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 | */ |
| 34 | static void |
| 35 | dequeue_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 | |
| 43 | static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) |
| 44 | { |
| 45 | } |
| 46 | |
| 47 | static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) |
| 48 | { |
| 49 | } |
| 50 | |
| 51 | static void set_curr_task_idle(struct rq *rq) |
| 52 | { |
| 53 | } |
| 54 | |
| 55 | static void switched_to_idle(struct rq *rq, struct task_struct *p) |
| 56 | { |
| 57 | BUG(); |
| 58 | } |
| 59 | |
| 60 | static void |
| 61 | prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio) |
| 62 | { |
| 63 | BUG(); |
| 64 | } |
| 65 | |
| 66 | static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task) |
| 67 | { |
| 68 | return 0; |
| 69 | } |
| 70 | |
| 71 | /* |
| 72 | * Simple, special scheduling class for the per-CPU idle tasks: |
| 73 | */ |
| 74 | static const struct sched_class idle_sched_class = { |
| 75 | /* .next is NULL */ |
| 76 | /* no enqueue/yield_task for idle tasks */ |
| 77 | |
| 78 | /* dequeue is not valid, we print a debug message there: */ |
| 79 | .dequeue_task = dequeue_task_idle, |
| 80 | |
| 81 | .check_preempt_curr = check_preempt_curr_idle, |
| 82 | |
| 83 | .pick_next_task = pick_next_task_idle, |
| 84 | .put_prev_task = put_prev_task_idle, |
| 85 | |
| 86 | #ifdef CONFIG_SMP |
| 87 | .select_task_rq = select_task_rq_idle, |
| 88 | #endif |
| 89 | |
| 90 | .set_curr_task = set_curr_task_idle, |
| 91 | .task_tick = task_tick_idle, |
| 92 | |
| 93 | .get_rr_interval = get_rr_interval_idle, |
| 94 | |
| 95 | .prio_changed = prio_changed_idle, |
| 96 | .switched_to = switched_to_idle, |
| 97 | }; |