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 /*
   9  * Idle tasks are unconditionally rescheduled:
  10  */
  11 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p)
  12 {
  13         resched_task(rq->idle);
  14 }
  15
  16 static struct task_struct *pick_next_task_idle(struct rq *rq)
  17 {
  18         schedstat_inc(rq, sched_goidle);
  19
  20         return rq->idle;
  21 }
  22
  23 /*
  24  * It is not legal to sleep in the idle task - print a warning
  25  * message if some code attempts to do it:
  26  */
  27 static void
  28 dequeue_task_idle(struct rq *rq, struct task_struct *p, int sleep)
  29 {
  30         spin_unlock_irq(&rq->lock);
  31         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  32         dump_stack();
  33         spin_lock_irq(&rq->lock);
  34 }
  35
  36 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  37 {
  38 }
  39
  40 #ifdef CONFIG_SMP
  41 static unsigned long
  42 load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
  43                   unsigned long max_load_move,
  44                   struct sched_domain *sd, enum cpu_idle_type idle,
  45                   int *all_pinned, int *this_best_prio)
  46 {
  47         return 0;
  48 }
  49
  50 static int
  51 move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
  52                    struct sched_domain *sd, enum cpu_idle_type idle)
  53 {
  54         return 0;
  55 }
  56 #endif
  57
  58 static void task_tick_idle(struct rq *rq, struct task_struct *curr)
  59 {
  60 }
  61
  62 static void set_curr_task_idle(struct rq *rq)
  63 {
  64 }
  65
  66 /*
  67  * Simple, special scheduling class for the per-CPU idle tasks:
  68  */
  69 const struct sched_class idle_sched_class = {
  70         /* .next is NULL */
  71         /* no enqueue/yield_task for idle tasks */
  72
  73         /* dequeue is not valid, we print a debug message there: */
  74         .dequeue_task           = dequeue_task_idle,
  75
  76         .check_preempt_curr     = check_preempt_curr_idle,
  77
  78         .pick_next_task         = pick_next_task_idle,
  79         .put_prev_task          = put_prev_task_idle,
  80
  81 #ifdef CONFIG_SMP
  82         .load_balance           = load_balance_idle,
  83         .move_one_task          = move_one_task_idle,
  84 #endif
  85
  86         .set_curr_task          = set_curr_task_idle,
  87         .task_tick              = task_tick_idle,
  88         /* no .task_new for idle tasks */
  89 };