kernel/sched/idle_task.c

   1 #include "sched.h"
   2
   3 /*
   4  * idle-task scheduling class.
   5  *
   6  * (NOTE: these are not related to SCHED_IDLE tasks which are
   7  *  handled in sched/fair.c)
   8  */
   9
  10 #ifdef CONFIG_SMP
  11 static int
  12 select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)
  13 {
  14         return task_cpu(p); /* IDLE tasks as never migrated */
  15 }
  16 #endif /* CONFIG_SMP */
  17 /*
  18  * Idle tasks are unconditionally rescheduled:
  19  */
  20 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
  21 {
  22         resched_task(rq->idle);
  23 }
  24
  25 static struct task_struct *pick_next_task_idle(struct rq *rq)
  26 {
  27         schedstat_inc(rq, sched_goidle);
  28         return rq->idle;
  29 }
  30
  31 /*
  32  * It is not legal to sleep in the idle task - print a warning
  33  * message if some code attempts to do it:
  34  */
  35 static void
  36 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
  37 {
  38         raw_spin_unlock_irq(&rq->lock);
  39         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  40         dump_stack();
  41         raw_spin_lock_irq(&rq->lock);
  42 }
  43
  44 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  45 {
  46 }
  47
  48 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  49 {
  50 }
  51
  52 static void set_curr_task_idle(struct rq *rq)
  53 {
  54 }
  55
  56 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  57 {
  58         BUG();
  59 }
  60
  61 static void
  62 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  63 {
  64         BUG();
  65 }
  66
  67 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  68 {
  69         return 0;
  70 }
  71
  72 /*
  73  * Simple, special scheduling class for the per-CPU idle tasks:
  74  */
  75 const struct sched_class idle_sched_class = {
  76         /* .next is NULL */
  77         /* no enqueue/yield_task for idle tasks */
  78
  79         /* dequeue is not valid, we print a debug message there: */
  80         .dequeue_task           = dequeue_task_idle,
  81
  82         .check_preempt_curr     = check_preempt_curr_idle,
  83
  84         .pick_next_task         = pick_next_task_idle,
  85         .put_prev_task          = put_prev_task_idle,
  86
  87 #ifdef CONFIG_SMP
  88         .select_task_rq         = select_task_rq_idle,
  89 #endif
  90
  91         .set_curr_task          = set_curr_task_idle,
  92         .task_tick              = task_tick_idle,
  93
  94         .get_rr_interval        = get_rr_interval_idle,
  95
  96         .prio_changed           = prio_changed_idle,
  97         .switched_to            = switched_to_idle,
  98 };