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         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 flags)
  35 {
  36         raw_spin_unlock_irq(&rq->lock);
  37         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  38         dump_stack();
  39         raw_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 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  47 {
  48 }
  49
  50 static void set_curr_task_idle(struct rq *rq)
  51 {
  52 }
  53
  54 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  55 {
  56         BUG();
  57 }
  58
  59 static void
  60 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  61 {
  62         BUG();
  63 }
  64
  65 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  66 {
  67         return 0;
  68 }
  69
  70 /*
  71  * Simple, special scheduling class for the per-CPU idle tasks:
  72  */
  73 static const struct sched_class idle_sched_class = {
  74         /* .next is NULL */
  75         /* no enqueue/yield_task for idle tasks */
  76
  77         /* dequeue is not valid, we print a debug message there: */
  78         .dequeue_task           = dequeue_task_idle,
  79
  80         .check_preempt_curr     = check_preempt_curr_idle,
  81
  82         .pick_next_task         = pick_next_task_idle,
  83         .put_prev_task          = put_prev_task_idle,
  84
  85 #ifdef CONFIG_SMP
  86         .select_task_rq         = select_task_rq_idle,
  87 #endif
  88
  89         .set_curr_task          = set_curr_task_idle,
  90         .task_tick              = task_tick_idle,
  91
  92         .get_rr_interval        = get_rr_interval_idle,
  93
  94         .prio_changed           = prio_changed_idle,
  95         .switched_to            = switched_to_idle,
  96 };