Method add_front

Kernel/include/list.h:276–300

	}

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

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

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

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

		releaseLock(&lock);
	}

	void insert(const T& obj, size_t pos){
		if(!num){