C++如何进行多线程同步_C++互斥锁(mutex)与条件变量(condition_variable)

#include 
#include 
#include 

std::mutex mtx;
int counter = 0;

void increment() {
    for (int i = 0; i < 1000; ++i) {
        std::lock_guard lock(mtx);
        ++counter;
    }
}

int main() {
    std::thread t1(increment);
    std::thread t2(increment);

    t1.join();
    t2.join();

    std::cout << "Final counter value: " << counter << std::endl; // 输出 2000
    return 0;
}

#include 
#include 
#include 
#include 
#include 

std::queue data_queue;
std::mutex mtx;
std::condition_variable cv;
bool finished = false;

void producer() {
    for (int i = 0; i < 5; ++i) {
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
        std::unique_lock lock(mtx);
        data_queue.push(i);
        std::cout << "Produced: " << i << std::endl;
        lock.unlock();
        cv.notify_one(); // 唤醒消费者
    }
    {
        std::unique_lock lock(mtx);
        finished = true;
    }
    cv.notify_all(); // 通知所有消费者结束
}

void consumer() {
    while (true) {
        std::unique_lock lock(mtx);
        cv.wait(lock, [] { 
            return !data_queue.empty() || finished; 
        });

        if (finished && data_queue.empty()) {
            break;
        }

        int value = data_queue.front();
        data_queue.pop();
        lock.unlock();

        std::cout << "Consumed: " << value << std::endl;
    }
}

int main() {
    std::thread p(producer);
    std::thread c1(consumer);
    std::thread c2(consumer);

    p.join();
    c1.join();
    c2.join();

    return 0;
}