RT scheduler

Linux 6.18.37 LTS: kernel/sched/rt.c
Linux 6.18.37 LTS: kernel/sched/core.c
Linux 6.18.37 LTS: kernel/sched/sched.h

/*
 * Adding/removing a task to/from a priority array:
 */
static void
enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
{
	struct sched_rt_entity *rt_se = &p->rt;

	if (flags & ENQUEUE_WAKEUP)
		rt_se->timeout = 0;

	check_schedstat_required();
	update_stats_wait_start_rt(rt_rq_of_se(rt_se), rt_se);

	enqueue_rt_entity(rt_se, flags);

	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
		enqueue_pushable_task(rq, p);
}

static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
{
	struct sched_rt_entity *rt_se = &p->rt;

	update_curr_rt(rq);
	dequeue_rt_entity(rt_se, flags);

	dequeue_pushable_task(rq, p);
}

/*
 * Put task to the head or the end of the run list without the overhead of
 * dequeue followed by enqueue.
 */
static void
requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
{
	if (on_rt_rq(rt_se)) {
		struct rt_prio_array *array = &rt_rq->active;

	next = list_entry(queue->next, struct sched_rt_entity, run_list);

	return next;
}

static struct task_struct *_pick_next_task_rt(struct rq *rq)
{
	struct sched_rt_entity *rt_se;
	struct rt_rq *rt_rq  = &rq->rt;

	do {
		rt_se = pick_next_rt_entity(rt_rq);
		if (unlikely(!rt_se))
			return NULL;
		rt_rq = group_rt_rq(rt_se);
	} while (rt_rq);

	return rt_task_of(rt_se);
}

static struct task_struct *pick_task_rt(struct rq *rq)
{
	struct task_struct *p;

	if (!sched_rt_runnable(rq))
		return NULL;

	p = _pick_next_task_rt(rq);

	return p;
}

static struct task_struct *pick_next_task_rt(struct rq *rq)
{
	struct task_struct *p = pick_task_rt(rq);

	if (p)
		set_next_task_rt(rq, p, true);

	return p;