C++多线程chap2多线程通信和同步6

这里，只是记录自己的学习笔记。

顺便和大家分享多线程的基础知识。然后从入门到实战。有代码。

知识点来源：

https://edu.51cto.com/course/26869.html

---

scoped_lock C++17 用于多个互斥体的免死锁 RAII 封装器 类似lock
explicit scoped_lock(_Mutexes&... _Mtxes) : _MyMutexes(_Mtxes...) { // construct and lock
_STD lock(_Mtxes...);
} 
lock(mux1, mux2);
mutex mux1, mux2;
std::scoped_lock lock(mux1, mux2);

scoped_lock ，出了栈区会自动释放锁。因此，不必手动再调用 unlock() 解锁。

#include <iostream>
#include <thread>
#include <string> 
#include <mutex>

using namespace std;

static mutex mux1;
static mutex mux2;

void TestScope1() {
    //模拟死锁，停100ms 等另一个线程锁 mux2
    this_thread::sleep_for(100ms);
    cout << "begin mux1 lock " << this_thread::get_id() << endl;
//    mux1.lock();
    cout << "begin mux2 lock " << this_thread::get_id() << endl;
//    mux2.lock();//死锁

    //C++11 
    // lock(mux1, mux2);

    //C++17
    // 出了栈区， 会将这里等待锁释放掉..所以不必再手动掉unlock()解锁
    scoped_lock lock(mux1, mux2);//解决死锁


    cout << "TestScope1 " << this_thread::get_id() << endl;
    this_thread::sleep_for(1000ms);
    //mux1.unlock();
    //mux2.unlock();
}

void TestScope2() {
    cout << "Begin mux2 lock " << this_thread::get_id() << endl;
    mux2.lock();
    this_thread::sleep_for(500ms);
    cout << "Begin mux1 lock " << this_thread::get_id() << endl;
    mux1.lock();//死锁

    cout << "TestScope2 " << this_thread::get_id() << endl;
    this_thread::sleep_for(1500ms);
    mux1.unlock();
    mux2.unlock();
}

int main() {
    {
        //演示死锁情况
        {
            thread th(TestScope1);
            th.detach();
        }
        {
            thread th(TestScope2);
            th.detach();
        }
    }


    getchar();
    return 0;
}