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// SPDX-License-Identifier: GPL-2.0
#include "sched.h"
/*
* 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 cpu, int sd_flag, int flags)
{
return task_cpu(p); /* IDLE tasks as never migrated */
}
#endif
/*
* Idle tasks are unconditionally rescheduled:
*/
static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
{
resched_curr(rq);
}
static struct task_struct *
pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
put_prev_task(rq, prev);
update_idle_core(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 flags)
{
raw_spin_unlock_irq(&rq->lock);
printk(KERN_ERR "bad: scheduling from the idle thread!\n");
dump_stack();
raw_spin_lock_irq(&rq->lock);
}
static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
{
}
/*
* scheduler tick hitting a task of our scheduling class.
*
* NOTE: This function can be called remotely by the tick offload that
* goes along full dynticks. Therefore no local assumption can be made
* and everything must be accessed through the @rq and @curr passed in
* parameters.
*/
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)
{
BUG();
}
static void
prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
{
BUG();
}
static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
{
return 0;
}
static void update_curr_idle(struct rq *rq)
{
}
/*
* Simple, special scheduling class for the per-CPU idle tasks:
*/
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,
.check_preempt_curr = check_preempt_curr_idle,
.pick_next_task = pick_next_task_idle,
.put_prev_task = put_prev_task_idle,
#ifdef CONFIG_SMP
.select_task_rq = select_task_rq_idle,
.set_cpus_allowed = set_cpus_allowed_common,
#endif
.set_curr_task = set_curr_task_idle,
.task_tick = task_tick_idle,
.get_rr_interval = get_rr_interval_idle,
.prio_changed = prio_changed_idle,
.switched_to = switched_to_idle,
.update_curr = update_curr_idle,
};
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