LXR linux/kernel/sched/idle

   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
  11static int
  12select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
  13{
  14        return task_cpu(p); /* IDLE tasks as never migrated */
  15}
  16#endif /* CONFIG_SMP */
  17
  18/*
  19 * Idle tasks are unconditionally rescheduled:
  20 */
  21static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
  22{
  23        resched_curr(rq);
  24}
  25
  26static struct task_struct *
  27pick_next_task_idle(struct rq *rq, struct task_struct *prev)
  28{
  29        put_prev_task(rq, prev);
  30
  31        schedstat_inc(rq, sched_goidle);
  32        return rq->idle;
  33}
  34
  35/*
  36 * It is not legal to sleep in the idle task - print a warning
  37 * message if some code attempts to do it:
  38 */
  39static void
  40dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
  41{
  42        raw_spin_unlock_irq(&rq->lock);
  43        printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  44        dump_stack();
  45        raw_spin_lock_irq(&rq->lock);
  46}
  47
  48static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  49{
  50        idle_exit_fair(rq);
  51        rq_last_tick_reset(rq);
  52}
  53
  54static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  55{
  56}
  57
  58static void set_curr_task_idle(struct rq *rq)
  59{
  60}
  61
  62static void switched_to_idle(struct rq *rq, struct task_struct *p)
  63{
  64        BUG();
  65}
  66
  67static void
  68prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  69{
  70        BUG();
  71}
  72
  73static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  74{
  75        return 0;
  76}
  77
  78static void update_curr_idle(struct rq *rq)
  79{
  80}
  81
  82/*
  83 * Simple, special scheduling class for the per-CPU idle tasks:
  84 */
  85const struct sched_class idle_sched_class = {
  86        /* .next is NULL */
  87        /* no enqueue/yield_task for idle tasks */
  88
  89        /* dequeue is not valid, we print a debug message there: */
  90        .dequeue_task           = dequeue_task_idle,
  91
  92        .check_preempt_curr     = check_preempt_curr_idle,
  93
  94        .pick_next_task         = pick_next_task_idle,
  95        .put_prev_task          = put_prev_task_idle,
  96
  97#ifdef CONFIG_SMP
  98        .select_task_rq         = select_task_rq_idle,
  99        .set_cpus_allowed       = set_cpus_allowed_common,
 100#endif
 101
 102        .set_curr_task          = set_curr_task_idle,
 103        .task_tick              = task_tick_idle,
 104
 105        .get_rr_interval        = get_rr_interval_idle,
 106
 107        .prio_changed           = prio_changed_idle,
 108        .switched_to            = switched_to_idle,
 109        .update_curr            = update_curr_idle,
 110};
 111