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
  10 select_task_rq_idle(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 };