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 cpu, 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         rq_last_tick_reset(rq);
  21 }
  22
  23 static void post_schedule_idle(struct rq *rq)
  24 {
  25         idle_enter_fair(rq);
  26 }
  27 #endif /* CONFIG_SMP */
  28 /*
  29  * Idle tasks are unconditionally rescheduled:
  30  */
  31 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
  32 {
  33         resched_task(rq->idle);
  34 }
  35
  36 static struct task_struct *pick_next_task_idle(struct rq *rq)
  37 {
  38         schedstat_inc(rq, sched_goidle);
  39 #ifdef CONFIG_SMP
  40         /* Trigger the post schedule to do an idle_enter for CFS */
  41         rq->post_schedule = 1;
  42 #endif
  43         return rq->idle;
  44 }
  45
  46 /*
  47  * It is not legal to sleep in the idle task - print a warning
  48  * message if some code attempts to do it:
  49  */
  50 static void
  51 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
  52 {
  53         raw_spin_unlock_irq(&rq->lock);
  54         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  55         dump_stack();
  56         raw_spin_lock_irq(&rq->lock);
  57 }
  58
  59 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  60 {
  61 }
  62
  63 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  64 {
  65 }
  66
  67 static void set_curr_task_idle(struct rq *rq)
  68 {
  69 }
  70
  71 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  72 {
  73         BUG();
  74 }
  75
  76 static void
  77 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  78 {
  79         BUG();
  80 }
  81
  82 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  83 {
  84         return 0;
  85 }
  86
  87 /*
  88  * Simple, special scheduling class for the per-CPU idle tasks:
  89  */
  90 const struct sched_class idle_sched_class = {
  91         /* .next is NULL */
  92         /* no enqueue/yield_task for idle tasks */
  93
  94         /* dequeue is not valid, we print a debug message there: */
  95         .dequeue_task           = dequeue_task_idle,
  96
  97         .check_preempt_curr     = check_preempt_curr_idle,
  98
  99         .pick_next_task         = pick_next_task_idle,
 100         .put_prev_task          = put_prev_task_idle,
 101
 102 #ifdef CONFIG_SMP
 103         .select_task_rq         = select_task_rq_idle,
 104         .pre_schedule           = pre_schedule_idle,
 105         .post_schedule          = post_schedule_idle,
 106 #endif
 107
 108         .set_curr_task          = set_curr_task_idle,
 109         .task_tick              = task_tick_idle,
 110
 111         .get_rr_interval        = get_rr_interval_idle,
 112
 113         .prio_changed           = prio_changed_idle,
 114         .switched_to            = switched_to_idle,
 115 };