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
  17 static void pre_schedule_idle(struct rq *rq, struct task_struct *prev)
  18 {
  19         idle_exit_fair(rq);
  20 }
  21
  22 static void post_schedule_idle(struct rq *rq)
  23 {
  24         idle_enter_fair(rq);
  25 }
  26 #endif /* CONFIG_SMP */
  27 /*
  28  * Idle tasks are unconditionally rescheduled:
  29  */
  30 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
  31 {
  32         resched_task(rq->idle);
  33 }
  34
  35 static struct task_struct *pick_next_task_idle(struct rq *rq)
  36 {
  37         schedstat_inc(rq, sched_goidle);
  38 #ifdef CONFIG_SMP
  39         /* Trigger the post schedule to do an idle_enter for CFS */
  40         rq->post_schedule = 1;
  41 #endif
  42         return rq->idle;
  43 }
  44
  45 /*
  46  * It is not legal to sleep in the idle task - print a warning
  47  * message if some code attempts to do it:
  48  */
  49 static void
  50 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
  51 {
  52         raw_spin_unlock_irq(&rq->lock);
  53         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  54         dump_stack();
  55         raw_spin_lock_irq(&rq->lock);
  56 }
  57
  58 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  59 {
  60 }
  61
  62 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  63 {
  64 }
  65
  66 static void set_curr_task_idle(struct rq *rq)
  67 {
  68 }
  69
  70 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  71 {
  72         BUG();
  73 }
  74
  75 static void
  76 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  77 {
  78         BUG();
  79 }
  80
  81 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  82 {
  83         return 0;
  84 }
  85
  86 /*
  87  * Simple, special scheduling class for the per-CPU idle tasks:
  88  */
  89 const struct sched_class idle_sched_class = {
  90         /* .next is NULL */
  91         /* no enqueue/yield_task for idle tasks */
  92
  93         /* dequeue is not valid, we print a debug message there: */
  94         .dequeue_task           = dequeue_task_idle,
  95
  96         .check_preempt_curr     = check_preempt_curr_idle,
  97
  98         .pick_next_task         = pick_next_task_idle,
  99         .put_prev_task          = put_prev_task_idle,
 100
 101 #ifdef CONFIG_SMP
 102         .select_task_rq         = select_task_rq_idle,
 103         .pre_schedule           = pre_schedule_idle,
 104         .post_schedule          = post_schedule_idle,
 105 #endif
 106
 107         .set_curr_task          = set_curr_task_idle,
 108         .task_tick              = task_tick_idle,
 109
 110         .get_rr_interval        = get_rr_interval_idle,
 111
 112         .prio_changed           = prio_changed_idle,
 113         .switched_to            = switched_to_idle,
 114 };