Merge "sched: drop related_thread_group_lock before calling call_rcu()"

	if (empty_group) {

		list_del(&grp->list);

		/*

		 * RCU, kswapd etc tasks can get woken up from

		 * call_rcu(). As the wakeup path also acquires

		 * the related_thread_group_lock, drop it here.

		 */

		write_unlock(&related_thread_group_lock);

		call_rcu(&grp->rcu, free_related_thread_group);

		write_lock(&related_thread_group_lock);

	}

}