sched/rt: Prevent idle task boosting

	rq = __task_rq_lock(p);

	/*

	 * Idle task boosting is a nono in general. There is one

	 * exception, when PREEMPT_RT and NOHZ is active:

	 *

	 * The idle task calls get_next_timer_interrupt() and holds

	 * the timer wheel base->lock on the CPU and another CPU wants

	 * to access the timer (probably to cancel it). We can safely

	 * ignore the boosting request, as the idle CPU runs this code

	 * with interrupts disabled and will complete the lock

	 * protected section without being interrupted. So there is no

	 * real need to boost.

	 */

	if (unlikely(p == rq->idle)) {

		WARN_ON(p != rq->curr);

		WARN_ON(p->pi_blocked_on);

		goto out_unlock;

	}

	trace_sched_pi_setprio(p, prio);

	oldprio = p->prio;

	prev_class = p->sched_class;

		enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);

	check_class_changed(rq, p, prev_class, oldprio);

out_unlock:

	__task_rq_unlock(rq);

}

#endif

void set_user_nice(struct task_struct *p, long nice)

{

	int old_prio, delta, on_rq;