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 #endif /* CONFIG_SMP */
  17
  18 /*
  19  * Idle tasks are unconditionally rescheduled:
  20  */
  21 static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
  22 {
  23         resched_task(rq->idle);
  24 }
  25
  26 static struct task_struct *
  27 pick_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  */
  39 static void
  40 dequeue_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
  48 static 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
  54 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  55 {
  56 }
  57
  58 static void set_curr_task_idle(struct rq *rq)
  59 {
  60 }
  61
  62 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  63 {
  64         BUG();
  65 }
  66
  67 static void
  68 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  69 {
  70         BUG();
  71 }
  72
  73 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  74 {
  75         return 0;
  76 }
  77
  78 /*
  79  * Simple, special scheduling class for the per-CPU idle tasks:
  80  */
  81 const struct sched_class idle_sched_class = {
  82         /* .next is NULL */
  83         /* no enqueue/yield_task for idle tasks */
  84
  85         /* dequeue is not valid, we print a debug message there: */
  86         .dequeue_task           = dequeue_task_idle,
  87
  88         .check_preempt_curr     = check_preempt_curr_idle,
  89
  90         .pick_next_task         = pick_next_task_idle,
  91         .put_prev_task          = put_prev_task_idle,
  92
  93 #ifdef CONFIG_SMP
  94         .select_task_rq         = select_task_rq_idle,
  95 #endif
  96
  97         .set_curr_task          = set_curr_task_idle,
  98         .task_tick              = task_tick_idle,
  99
 100         .get_rr_interval        = get_rr_interval_idle,
 101
 102         .prio_changed           = prio_changed_idle,
 103         .switched_to            = switched_to_idle,
 104 };