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 #ifdef CONFIG_SMP
  33         idle_enter_fair(rq);
  34 #endif
  35         return rq->idle;
  36 }
  37
  38 /*
  39  * It is not legal to sleep in the idle task - print a warning
  40  * message if some code attempts to do it:
  41  */
  42 static void
  43 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
  44 {
  45         raw_spin_unlock_irq(&rq->lock);
  46         printk(KERN_ERR "bad: scheduling from the idle thread!\n");
  47         dump_stack();
  48         raw_spin_lock_irq(&rq->lock);
  49 }
  50
  51 static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
  52 {
  53 #ifdef CONFIG_SMP
  54         idle_exit_fair(rq);
  55         rq_last_tick_reset(rq);
  56 #endif
  57 }
  58
  59 static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
  60 {
  61 }
  62
  63 static void set_curr_task_idle(struct rq *rq)
  64 {
  65 }
  66
  67 static void switched_to_idle(struct rq *rq, struct task_struct *p)
  68 {
  69         BUG();
  70 }
  71
  72 static void
  73 prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
  74 {
  75         BUG();
  76 }
  77
  78 static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
  79 {
  80         return 0;
  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 #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 };