Method defer_to_new_thread

thread/thread.cpp:704–719

            th->remove_from_list();
        }
        bool defer_to_new_thread() const {
            auto idle_worker = vcpu->idle_worker;
            if (current->next() == idle_worker) {
                if (idle_worker->next() == current) {
                    // if defer_func is executed in idle_worker and it yields,
                    // photon will be broken. so we should return true and
                    // create a new thread to execute the defer func.
                    return true;
                }

                // postpone idle worker
                auto next = idle_worker->remove_from_list();
                next->insert_after(idle_worker);
            }
            return false;
        }
    };

    inline void thread::dequeue_ready_atomic(states newstat)