idle_task.c 2.2 KB
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#include "sched.h"

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

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

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static struct task_struct *
pick_next_task_idle(struct rq *rq, struct task_struct *prev)
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{
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	put_prev_task(rq, prev);
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	schedstat_inc(rq, sched_goidle);
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#ifdef CONFIG_SMP
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	idle_enter_fair(rq);
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#endif
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	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
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dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
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{
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	raw_spin_unlock_irq(&rq->lock);
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	printk(KERN_ERR "bad: scheduling from the idle thread!\n");
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	dump_stack();
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	raw_spin_lock_irq(&rq->lock);
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}

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static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
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{
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#ifdef CONFIG_SMP
	idle_exit_fair(rq);
	rq_last_tick_reset(rq);
#endif
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}

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

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static void set_curr_task_idle(struct rq *rq)
{
}

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static void switched_to_idle(struct rq *rq, struct task_struct *p)
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{
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	BUG();
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}

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static void
prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
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{
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	BUG();
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}

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static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
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{
	return 0;
}

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

	/* dequeue is not valid, we print a debug message there: */
	.dequeue_task		= dequeue_task_idle,

	.check_preempt_curr	= check_preempt_curr_idle,

	.pick_next_task		= pick_next_task_idle,
	.put_prev_task		= put_prev_task_idle,

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#ifdef CONFIG_SMP
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	.select_task_rq		= select_task_rq_idle,
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#endif
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	.set_curr_task          = set_curr_task_idle,
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	.task_tick		= task_tick_idle,
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	.get_rr_interval	= get_rr_interval_idle,

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	.prio_changed		= prio_changed_idle,
	.switched_to		= switched_to_idle,
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};