C++多线程编程第五讲--互斥量概念、用法、死锁演示及解决详解

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//(1)互斥量的(mutex)的基本概念 // 就是一个类的对象。多个线程可以尝试对一个mutex的对象进行lock，但是只有一个线程成功，其他线程需要等待。 //(2)互斥量的用法     //(2.1)lock(), unlock():要成对使用    #include<iostream>     #include<thread>     #include<vector>     #include<list>     #include<mutex>           using namespace std;           class A     {     public:         //把收到的消息，入到一个队列中         void inMsgRecvQueue()         {             int i;             for (i = 0; i < 100000; ++i)             {                       cout << "push_back num = " << i << endl;                 //lock之后只能有一个线程可以对msgQueue队列做操作                 my_mutex.lock();                 msgQueue.push_back(i);                   //数字i就是玩家的命令。                 my_mutex.unlock();             }         }               bool outMsgProc(int& command)         {             my_mutex.lock();             if (!msgQueue.empty())             {                 //消息不为空                 command = msgQueue.front();                 msgQueue.pop_front();          //移除首元素                       my_mutex.unlock();                 return true;             }             else             {                 my_mutex.unlock();                 return false;             }         }               //把数据从消息队列中取出         void outMsgRecvQueue()         {             int i;             int command = 0;             for (i = 0; i < 100000; ++i)             {                 int result = outMsgProc(command);                 if (result == true)                 {                     cout << "command = " << command << endl;                 }                 else                 {                     cout << "msgQueue is empty" << endl;                 }             }         }           private:         list<int> msgQueue;         mutex my_mutex;       //创建一个互斥量     };           int main()     {         A myobj;               thread myOutMsg(&A::outMsgRecvQueue, std::ref(myobj));   //保证线程中用的同一个对象         thread myInMsg(&A::inMsgRecvQueue, std::ref(myobj));               myOutMsg.join();         myInMsg.join();               cout << "main thread end..." << endl;         return 0;     } //(2.2)std::lock_guard类模板，与智能指针的作用是一致的，就是为了更加智能的释放资源。     #include<iostream>     #include<thread>     #include<vector>     #include<list>     #include<mutex>           using namespace std;           class A     {     public:         //把收到的消息，入到一个队列中         void inMsgRecvQueue()         {             int i;             for (i = 0; i < 100000; ++i)             {                       cout << "push_back num = " << i << endl;                 //lock之后只能有一个线程可以对msgQueue队列做操作                 lock_guard<mutex> sbguard(my_mutex);                 msgQueue.push_back(i);                   //数字i就是玩家的命令。             }         }               bool outMsgProc(int& command)         {             lock_guard<mutex> sbguard(my_mutex);             if (!msgQueue.empty())             {                 //消息不为空                 command = msgQueue.front();                 msgQueue.pop_front();          //移除首元素                       return true;             }             else             {                 return false;             }         }               //把数据从消息队列中取出         void outMsgRecvQueue()         {             int i;             int command = 0;             for (i = 0; i < 100000; ++i)             {                 int result = outMsgProc(command);                 if (result == true)                 {                     cout << "command = " << command << endl;                 }                 else                 {                     cout << "msgQueue is empty" << endl;                 }             }         }           private:         list<int> msgQueue;         mutex my_mutex;       //创建一个互斥量     };           int main()     {         A myobj;               thread myOutMsg(&A::outMsgRecvQueue, std::ref(myobj));   //保证线程中用的同一个对象         thread myInMsg(&A::inMsgRecvQueue, std::ref(myobj));               myOutMsg.join();         myInMsg.join();               cout << "main thread end..." << endl;         return 0;     } //(3)死锁：必须要有两把锁，才能出现死锁。     //(3.1)死锁演示     #include<iostream>     #include<thread>     #include<vector>     #include<list>     #include<mutex>           using namespace std;           class A     {     public:         //把收到的消息，入到一个队列中         void inMsgRecvQueue()         {             int i;             for (i = 0; i < 100000; ++i)             {                       cout << "push_back num = " << i << endl;                 //lock之后只能有一个线程可以对msgQueue队列做操作                 my_mutex1.lock();                 //...                 my_mutex2.lock();                 //...                 msgQueue.push_back(i);                   //数字i就是玩家的命令。                 //...                 my_mutex2.unlock();                 //...                 my_mutex1.unlock();                   }         }               bool outMsgProc(int& command)         {             my_mutex2.lock();             //...             my_mutex1.lock();             if (!msgQueue.empty())             {                 //消息不为空                 command = msgQueue.front();                 msgQueue.pop_front();          //移除首元素                       my_mutex1.unlock();                 my_mutex2.unlock();                 return true;             }             else             {                 my_mutex1.unlock();                 my_mutex2.unlock();                 return false;             }         }               //把数据从消息队列中取出         void outMsgRecvQueue()         {             int i;             int command = 0;             for (i = 0; i < 100000; ++i)             {                 int result = outMsgProc(command);                 if (result == true)                 {                     cout << "command = " << command << endl;                 }                 else                 {                     cout << "msgQueue is empty" << endl;                 }             }         }           private:         list<int> msgQueue;         mutex my_mutex1;         mutex my_mutex2;     };           int main()     {         A myobj;               thread myOutMsg(&A::outMsgRecvQueue, std::ref(myobj));   //保证线程中用的同一个对象         thread myInMsg(&A::inMsgRecvQueue, std::ref(myobj));               myOutMsg.join();         myInMsg.join();               cout << "main thread end..." << endl;         return 0;     }       //(3.2)死锁的一般解决方案:只要保证锁的lock顺序一致就不会出现死锁。       #include<iostream>     #include<thread>     #include<vector>     #include<list>     #include<mutex>           using namespace std;           class A     {     public:         //把收到的消息，入到一个队列中         void inMsgRecvQueue()         {             int i;             for (i = 0; i < 100000; ++i)             {                       cout << "push_back num = " << i << endl;                 //lock之后只能有一个线程可以对msgQueue队列做操作                 my_mutex1.lock();                 //...                 my_mutex2.lock();                 //...                 msgQueue.push_back(i);                   //数字i就是玩家的命令。                 //...                 my_mutex2.unlock();                 //...                 my_mutex1.unlock();                   }         }               bool outMsgProc(int& command)         {             my_mutex1.lock();             //...             my_mutex2.lock();             if (!msgQueue.empty())             {                 //消息不为空                 command = msgQueue.front();                 msgQueue.pop_front();          //移除首元素                       my_mutex2.unlock();                 my_mutex1.unlock();                 return true;             }             else             {                 my_mutex2.unlock();                 my_mutex1.unlock();                 return false;             }         }               //把数据从消息队列中取出         void outMsgRecvQueue()         {             int i;             int command = 0;             for (i = 0; i < 100000; ++i)             {                 int result = outMsgProc(command);                 if (result == true)                 {                     cout << "command = " << command << endl;                 }                 else                 {                     cout << "msgQueue is empty" << endl;                 }             }         }           private:         list<int> msgQueue;         mutex my_mutex1;         mutex my_mutex2;     };           int main()     {         A myobj;               thread myOutMsg(&A::outMsgRecvQueue, std::ref(myobj));   //保证线程中用的同一个对象         thread myInMsg(&A::inMsgRecvQueue, std::ref(myobj));               myOutMsg.join();         myInMsg.join();               cout << "main thread end..." << endl;         return 0;     }   //(3.3)std::lock()函数模板     // 一次锁住两个或两个以上的互斥量。如果这些锁中其中有一个没有lock成功，则释放已经lock的mutex对象，     // 并在这句代码中不断的循环执行为所有的mutex对象上锁的行为，直到所有的互斥量都锁成功为止。     #include<iostream>     #include<thread>     #include<vector>     #include<list>     #include<mutex>           using namespace std;           class A     {     public:         //把收到的消息，入到一个队列中         void inMsgRecvQueue()         {             int i;             for (i = 0; i < 100000; ++i)             {                       cout << "push_back num = " << i << endl;                 //lock之后只能有一个线程可以对msgQueue队列做操作                 std::lock(my_mutex1, my_mutex2);                 //...                 msgQueue.push_back(i);                   //数字i就是玩家的命令。                 //...                 my_mutex2.unlock();                 //...                 my_mutex1.unlock();                   }         }               bool outMsgProc(int& command)         {             std::lock(my_mutex1, my_mutex2);             if (!msgQueue.empty())             {                 //消息不为空                 command = msgQueue.front();                 msgQueue.pop_front();          //移除首元素                       my_mutex2.unlock();                 my_mutex1.unlock();                 return true;             }             else             {                 my_mutex2.unlock();                 my_mutex1.unlock();                 return false;             }         }               //把数据从消息队列中取出         void outMsgRecvQueue()         {             int i;             int command = 0;             for (i = 0; i < 100000; ++i)             {                 int result = outMsgProc(command);                 if (result == true)                 {                     cout << "command = " << command << endl;                 }                 else                 {                     cout << "msgQueue is empty" << endl;                 }             }         }           private:         list<int> msgQueue;         mutex my_mutex1;         mutex my_mutex2;     };           int main()     {         A myobj;               thread myOutMsg(&A::outMsgRecvQueue, std::ref(myobj));   //保证线程中用的同一个对象         thread myInMsg(&A::inMsgRecvQueue, std::ref(myobj));               myOutMsg.join();         myInMsg.join();               cout << "main thread end..." << endl;         return 0;     }   //(3.4)std::lock_guard的adopt_lock参数     //不必自己unlock #include<iostream> #include<thread> #include<vector> #include<list> #include<mutex>   using namespace std;   class A { public:     //把收到的消息，入到一个队列中     void inMsgRecvQueue()     {         int i;         for (i = 0; i < 100000; ++i)         {                           cout << "push_back num = " << i << endl;             //lock之后只能有一个线程可以对msgQueue队列做操作             std::lock(my_mutex1, my_mutex2);             lock_guard<mutex> lock_guard1(my_mutex1, std::adopt_lock);             lock_guard<mutex> lock_guard2(my_mutex2, std::adopt_lock);             //...             msgQueue.push_back(i);                   //数字i就是玩家的命令。             //...         }     }       bool outMsgProc(int &command)     {         std::lock(my_mutex1, my_mutex2);         lock_guard<mutex> lock_guard1(my_mutex1, std::adopt_lock);         lock_guard<mutex> lock_guard2(my_mutex2, std::adopt_lock);         if (!msgQueue.empty())         {             //消息不为空             command = msgQueue.front();             msgQueue.pop_front();          //移除首元素             return true;         }         else         {             return false;         }     }       //把数据从消息队列中取出     void outMsgRecvQueue()     {         int i;         int command = 0;         for (i = 0; i < 100000; ++i)         {             int result = outMsgProc(command);             if (result == true)             {                 cout << "command = " << command << endl;             }             else             {                 cout << "msgQueue is empty" << endl;             }         }     }   private:     list<int> msgQueue;     mutex my_mutex1;     mutex my_mutex2; };   int main() {     A myobj;       thread myOutMsg(&A::outMsgRecvQueue, std::ref(myobj));   //保证线程中用的同一个对象     thread myInMsg(&A::inMsgRecvQueue, std::ref(myobj));       myOutMsg.join();     myInMsg.join();       cout << "main thread end..." << endl;     return 0; }