Method add_back

Kernel/include/list.h:248–274

	}

	void add_back(const T& obj) {
		acquireLock(&lock);

		ListNode<T>* node;
		if(cache.get_length() <= 0){
			node = (ListNode<T>*)kmalloc(sizeof(ListNode<T>));
		} else {
			node = cache.remove_at(0);
		}
		
		assert(node);

		node->obj = obj;
		node->next = node->prev = nullptr;

		if (!front) {
			front = node;
		}
		else if (back){
			back->next = node;
			node->prev = back;
		}
		back = node;
		num++;
		
		releaseLock(&lock);
	}

	void add_front(const T& obj) {
		acquireLock(&lock);