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         calc_load_account_idle(rq);
  29         return rq->idle;
  30 }
  31
  32 /*
  33  * It is not legal to sleep in the idle task - print a warning
  34  * message if some code attempts to do it:
  35  */
  36 static void
  37 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
  38 {
  39         raw_spin_unlock_irq(&rq->lock);
  40         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  41         dump_stack();
  42         raw_spin_lock_irq(&rq->lock);
  43 }
  44
  45 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  46 {
  47 }
  48
  49 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  50 {
  51 }
  52
  53 static void set_curr_task_idle(struct rq *rq)
  54 {
  55 }
  56
  57 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  58 {
  59         BUG();
  60 }
  61
  62 static void
  63 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  64 {
  65         BUG();
  66 }
  67
  68 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  69 {
  70         return 0;
  71 }
  72
  73 /*
  74  * Simple, special scheduling class for the per-CPU idle tasks:
  75  */
  76 const struct sched_class idle_sched_class = {
  77         /* .next is NULL */
  78         /* no enqueue/yield_task for idle tasks */
  79
  80         /* dequeue is not valid, we print a debug message there: */
  81         .dequeue_task           = dequeue_task_idle,
  82
  83         .check_preempt_curr     = check_preempt_curr_idle,
  84
  85         .pick_next_task         = pick_next_task_idle,
  86         .put_prev_task          = put_prev_task_idle,
  87
  88 #ifdef CONFIG_SMP
  89         .select_task_rq         = select_task_rq_idle,
  90 #endif
  91
  92         .set_curr_task          = set_curr_task_idle,
  93         .task_tick              = task_tick_idle,
  94
  95         .get_rr_interval        = get_rr_interval_idle,
  96
  97         .prio_changed           = prio_changed_idle,
  98         .switched_to            = switched_to_idle,
  99 };