sched/core: Fix update_rq_clock() splat on hotplug (and suspend/resume)

{

	struct rq *rq = dead_rq;

	struct task_struct *next, *stop = rq->stop;

	struct rq_flags rf, old_rf;

	struct rq_flags rf;

	int dest_cpu;

	/*

	 * class method both need to have an up-to-date

	 * value of rq->clock[_task]

	 */

	rq_pin_lock(rq, &rf);

	update_rq_clock(rq);

	rq_unpin_lock(rq, &rf);

	for (;;) {

		/*

		/*

		 * pick_next_task() assumes pinned rq->lock:

		 */

		rq_pin_lock(rq, &rf);

		rq_repin_lock(rq, &rf);

		next = pick_next_task(rq, &fake_task, &rf);

		BUG_ON(!next);

		next->sched_class->put_prev_task(rq, next);

			continue;

		}

		/*

		 * __migrate_task() may return with a different

		 * rq->lock held and a new cookie in 'rf', but we need

		 * to preserve rf::clock_update_flags for 'dead_rq'.

		 */

		old_rf = rf;

		/* Find suitable destination for @next, with force if needed. */

		dest_cpu = select_fallback_rq(dead_rq->cpu, next);

			raw_spin_unlock(&rq->lock);

			rq = dead_rq;

			raw_spin_lock(&rq->lock);

			rf = old_rf;

		}

		raw_spin_unlock(&next->pi_lock);

	}