root/kernel/sched_idletask.c

DEFINITIONS

1. select_task_rq_idle
2. check_preempt_curr_idle
3. pick_next_task_idle
4. dequeue_task_idle
5. put_prev_task_idle
6. load_balance_idle
7. move_one_task_idle
8. task_tick_idle
9. set_curr_task_idle
10. switched_to_idle
11. prio_changed_idle

/*
 * idle-task scheduling class.
 *
 * (NOTE: these are not related to SCHED_IDLE tasks which are
 *  handled in sched_fair.c)
 */

#ifdef CONFIG_SMP
static int select_task_rq_idle(struct task_struct *p, int sync)
{
        return task_cpu(p); /* IDLE tasks as never migrated */
}
#endif /* CONFIG_SMP */
/*
 * Idle tasks are unconditionally rescheduled:
 */
static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int sync)
{
        resched_task(rq->idle);
}

static struct task_struct *pick_next_task_idle(struct rq *rq)
{
        schedstat_inc(rq, sched_goidle);

        return rq->idle;
}

/*
 * It is not legal to sleep in the idle task - print a warning
 * message if some code attempts to do it:
 */
static void
dequeue_task_idle(struct rq *rq, struct task_struct *p, int sleep)
{
        spin_unlock_irq(&rq->lock);
        printk(KERN_ERR "bad: scheduling from the idle thread!\n");
        dump_stack();
        spin_lock_irq(&rq->lock);
}

static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
{
}

#ifdef CONFIG_SMP
static unsigned long
load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
                  unsigned long max_load_move,
                  struct sched_domain *sd, enum cpu_idle_type idle,
                  int *all_pinned, int *this_best_prio)
{
        return 0;
}

static int
move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
                   struct sched_domain *sd, enum cpu_idle_type idle)
{
        return 0;
}
#endif

static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
{
}

static void set_curr_task_idle(struct rq *rq)
{
}

static void switched_to_idle(struct rq *rq, struct task_struct *p,
                             int running)
{
        /* Can this actually happen?? */
        if (running)
                resched_task(rq->curr);
        else
                check_preempt_curr(rq, p, 0);
}

static void prio_changed_idle(struct rq *rq, struct task_struct *p,
                              int oldprio, int running)
{
        /* This can happen for hot plug CPUS */

        /*
         * Reschedule if we are currently running on this runqueue and
         * our priority decreased, or if we are not currently running on
         * this runqueue and our priority is higher than the current's
         */
        if (running) {
                if (p->prio > oldprio)
                        resched_task(rq->curr);
        } else
                check_preempt_curr(rq, p, 0);
}

/*
 * Simple, special scheduling class for the per-CPU idle tasks:
 */
static const struct sched_class idle_sched_class = {
        /* .next is NULL */
        /* no enqueue/yield_task for idle tasks */

        /* dequeue is not valid, we print a debug message there: */
        .dequeue_task           = dequeue_task_idle,
#ifdef CONFIG_SMP
        .select_task_rq         = select_task_rq_idle,
#endif /* CONFIG_SMP */

        .check_preempt_curr     = check_preempt_curr_idle,

        .pick_next_task         = pick_next_task_idle,
        .put_prev_task          = put_prev_task_idle,

#ifdef CONFIG_SMP
        .load_balance           = load_balance_idle,
        .move_one_task          = move_one_task_idle,
#endif

        .set_curr_task          = set_curr_task_idle,
        .task_tick              = task_tick_idle,

        .prio_changed           = prio_changed_idle,
        .switched_to            = switched_to_idle,

        /* no .task_new for idle tasks */
};