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