C++ 中的线程序列化是什么意思

C++ 中的线程序列化是什么意思？

cpp
#include 
#include 
#include 
#include 
std::mutex mtx;
std::condition_variable cv;
bool ready = false;
void threadFunc(int id) {
    std::unique_lock lock(mtx);
    cv.wait(lock, []{ return ready; }); // 等待条件变量的信号
    std::cout << "Thread " << id << " is executing." << std::endl;
}
int main() {
    std::thread threads[5];
    // 创建并启动线程
    for (int i = 0; i < 5; ++i) {
        threads[i] = std::thread(threadFunc, i);
    }
    std::this_thread::sleep_for(std::chrono::seconds(2));
    std::cout << "Main thread is ready." << std::endl;
    {
        // 发送条件变量的信号，唤醒等待的线程
        std::lock_guard lock(mtx);
        ready = true;
        cv.notify_all();
    }
    // 等待所有线程执行完毕
    for (auto& thread : threads) {
        thread.join();
    }
    return 0;
}