c++ 条件变量使用例子

#include 
#include 
#include 
#include 
#include 

std::condition_variable m_cv;
std::mutex m_mutex;
std::atomic AtomicInt;

typedef void *(*FOSThreadRoutine)(int &);

void *AudioRecvThread(int &i)
{
    while (1)
    {
        i = AtomicInt;
        while (AtomicInt % 2 == 0)
        {
            std::unique_lock lock(m_mutex);//自解锁
            m_cv.wait(lock);//等待唤醒的信号
            std::thread::id this_id = std::this_thread::get_id();
            std::cout << "this_id= " << this_id << " wait" << std::endl;
        }

        std::thread::id this_id = std::this_thread::get_id();
        std::cout << " this_id= " << this_id << ",i=" << i << std::endl
                  << std::endl;
        std::this_thread::sleep_for(std::chrono::milliseconds(1000));
    }
}

int main(void)
{

    FOSThreadRoutine fnRoutine;
    fnRoutine = AudioRecvThread;

    int i = 0;
    std::thread hd_ = std::move(std::thread(fnRoutine, std::ref(i)));//如果要传引用进去，需要使用std::ref；

    while (1)
    {
        int i = 0;
        std::cin >> i;
        std::cout << "手动输入 i = " << i << std::endl;
        AtomicInt = i;
        m_cv.notify_one();
    }

    hd_.join();

    return 1;
}


程序运行后，手动输入整数，会有不同的输出；偶数等待，奇数持续运行；

运行结果：

[root@localhost test]# ./test
1
手动输入 i = 1
this_id= 139770932119296 wait  //输入奇数将持续运行下去，不会停止；
 this_id= 139770932119296,i=0

 this_id= 139770932119296,i=1

 this_id= 139770932119296,i=1

 this_id= 139770932119296,i=1

2
手动输入 i = 2//第一次运行到此处，m_cv.wait(lock);将等待信号
2
手动输入 i = 2
this_id= 139770932119296 wait//第一次输入2后被阻塞，在收到 m_cv.notify_one();后解除等待，接着输出此句；
2
手动输入 i = 2
this_id= 139770932119296 wait
2
手动输入 i = 2
this_id= 139770932119296 wait
3
手动输入 i = 3
this_id= 139770932119296 wait
 this_id= 139770932119296,i=2

 this_id= 139770932119296,i=3

 this_id= 139770932119296,i=3

 this_id= 139770932119296,i=3

9 this_id= 139770932119296,i=3

99
手动输入 i = 999
 this_id= 139770932119296,i=999

 this_id= 139770932119296,i=999

 this_id= 139770932119296,i=999


 this_id= 139770932119296,i=999

 this_id= 139770932119296,i=999