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C++多线程同步总结

news 来源：原创 2024/9/29 7:32:33

C++多线程同步总结

关于C++多线程同步

一、C++11规范下的线程库

1、C++11 线程库的基本用法：创建线程、分离线程

#include<iostream>
#include<thread>
#include<windows.h>
using namespace std;
void threadProc()
{cout<<"this is in threadProc\n";cout<<"thread1's id is "<<this_thread::get_id()<<endl; //获取所属线程的id
}
void threadProc2(int num)
{cout<<"thread num = "<<num<<endl;
}
void threadProc3()
{cout<<"this thread is detached\n";
}
void threadProc4()
{cout<<"this thread is detached and won't print in the same console.'\n";
}
int main()
{thread a;//创建线程1，定义线程，后面再分配任务a = thread(threadProc);thread b(threadProc2,5);//创建线程2 ，定义线程的时候分配任务，参数类似于printf一样，可以为多个a.join();b.join();//采用join，主线程会阻塞等待子线程执行完毕thread c(threadProc3);c.detach();//采用detach，主线程不会等，这个线程开启早，还能输出到主线程的控制台cout<<"main thread exit"<<endl;thread d(threadProc4);d.detach();//
}

运行结果：

2、基本的互斥锁

上述运行，输出语句显然没有顺序执行，为了达到一行一行输出的效果，可以使用最基本的互斥锁。

#include<iostream>
#include<thread>
#include<mutex>
using namespace std;
mutex mu;//互斥锁 
void test1()
{for(int i=0;i<5;i++){
//        mu.lock();//锁住 cout<<"test1 i = "<<i<<endl;
//        mu.unlock();//释放 }
}
void test2()
{for(int j=0;j<5;j++){
//        mu.lock();cout<<"test2 j = "<<j<<endl;
//        mu.unlock();}
}
int main()
{thread a(test1);thread b(test2);a.join();b.join();cout<<"main thread finish."<<endl;
}

运行结果：

不加锁的话，输出就会混乱。

这里打开4行注释，重新运行。

运行结果：

可以简单理解为：test1获得锁以后，test2调用lock()，就会阻塞执行，直到test1()调用unlock()释放锁。

3、lock_guard

#include <iostream>
#include <thread>
#include <mutex>mutex mu;//互斥锁 
/*
lock_guard<mutex> locka(mu);
作用范围为从这一行开始，到那一次循环结束，还不用自己手动解锁。 
*/
void test3()
{for(int i=0;i<5;i++){std::lock_guard<std::mutex> locka(mu); std::cout << "test3 i = "<< i << std::endl;}
}
void test4()
{for(int j=0;j<5;j++){std::lock_guard<std::mutex> lock(mu);std::cout << "test4 j = " << j << std::endl;}
}
int main()
{std::thread a(test3);std::thread b(test4);a.join();b.join();std::cout<<"main thread finish."<<std::endl;
}

运行结果：

4、unique_lock

#include<iostream>
#include<thread>
#include<mutex>
using namespace std;
mutex mu;//互斥锁 
void test5()
{for(int i=0;i<5;i++){unique_lock<mutex> locka(mu,defer_lock); cout<<"test5 i = "<<i<<endl;locka.lock();cout<<"this is lock1"<<endl;}
}
void test6()
{for(int j=0;j<5;j++){unique_lock<mutex> locka(mu); cout<<"test6 j = "<<j<<endl;locka.unlock();locka.lock();cout<<"this is lock2"<<endl;}
}
int main()
{thread a(test5);thread b(test6);a.join();b.join();cout<<"main thread finish."<<endl;
}

运行结果：

 5、condition_variable

#include<iostream>
#include<thread>
#include<mutex>
#include<condition_variable>using namespace std;mutex mu;
condition_variable cv;
bool print = false;
void test7()
{for(int i=0;i<5;i++){unique_lock<mutex> l(mu);cout<<"test7 i = "<<i<<endl;cv.notify_one();print = true;}
}
void test8()
{for(int j=0;j<5;j++){unique_lock<mutex> l(mu);if(!print){cv.wait(l);}cout<<"test8 j = "<<j<<endl;print = false;}
}
int main()
{thread a(test7);thread b(test8);a.join();b.join();
}

运行结果：

二、Win32 API 实现线程同步

1、临界区

#include <iostream>
#include <thread>
#include <windows.h>using namespace std;CRITICAL_SECTION section;//临界区变量void test01()
{for(int i=0;i<5;i++){EnterCriticalSection(&section);//类似于 mutex.lock() cout<<"this is test01 i = "<<i<<endl;Sleep(1);LeaveCriticalSection(&section);//类似于 mutex.unlock() }
} 
void test02()
{for(int j=0;j<5;j++){EnterCriticalSection(&section);cout<<"this is test02 j = "<<j<<endl;Sleep(1);LeaveCriticalSection(&section);}
}
int main()
{InitializeCriticalSection(&section);//初始化临界区对象thread a(test01);thread b(test02);a.join();b.join();DeleteCriticalSection(&section);//用完了，就删除临界区 
}

运行结果：

效果类似于mutex，只是都要在执行完循环进行解锁的操作。

2、互斥锁

#include<iostream>
#include<thread>
#include<windows.h>
using namespace std;
HANDLE hmutex;
void test03()
{for(int i=0;i<5;i++){WaitForSingleObject(hmutex,INFINITE);//类似于mutex.lock() 阻塞等待多少时间 cout<<"test03 i = "<<i<<endl;ReleaseMutex(hmutex);//类似于mutex.unlock() 释放互斥锁 }
}
void test04()
{for(int j=0;j<5;j++){WaitForSingleObject(hmutex,INFINITE);cout<<"test04 j = "<<j<<endl;ReleaseMutex(hmutex);}
}
int main()
{hmutex = CreateMutex(NULL,FALSE,"mutex");//创建一个互斥锁 thread a(test03);thread b(test04);a.join();b.join();CloseHandle(hmutex);//释放句柄 
}

运行结果：

3、事件

#include<iostream>
#include<thread>
#include<windows.h>using namespace std;HANDLE hevent;
void test05()
{for(int i=0;i<5;i++){WaitForSingleObject(hevent,INFINITE);//类似于mutex.lock() 阻塞等待多少时间 cout<<"test05 i = "<<i<<endl;SetEvent(hevent);//类似于mutex.unlock() 释放互斥锁 }
}
void test06()
{for(int j=0;j<5;j++){WaitForSingleObject(hevent,INFINITE);cout<<"test06 j = "<<j<<endl;SetEvent(hevent);}
}
int main()
{hevent = CreateEvent(NULL,FALSE,TRUE,"event");//创建一个事件 thread a(test05);thread b(test06);a.join();b.join();CloseHandle(hevent);//释放句柄 
}

运行结果：

4、信号量

#include <iostream>
#include <thread>
#include <windows.h>using namespace std;HANDLE sem;
void test07()
{for(int i=0;i<5;i++){WaitForSingleObject(sem,INFINITE);//类似于mutex.lock() 阻塞等待多少时间 cout<<"test07 i = "<<i<<endl;ReleaseSemaphore(sem,1,NULL);//类似于mutex.unlock() 释放互斥锁 }
}
void test08()
{for(int j=0;j<5;j++){WaitForSingleObject(sem,INFINITE);cout<<"test08 j = "<<j<<endl;ReleaseSemaphore(sem,1,NULL);}
}
int main()
{sem = CreateSemaphore(NULL,1,2,"semaphore");thread a(test07);thread b(test08);a.join();b.join();CloseHandle(sem);//释放句柄 
}

运行结果：

#include <iostream>
#include <fstream>
#include <random>
#include <ctime>#include <windows.h>
//#include <time.h>
#include <stdio.h>
#include <math.h>
#include <bitset>#include <thread>
#include <mutex>
#include <condition_variable>#define NAME_LINE   40
void* g_hMutex2 = NULL; //使用适当的初始化方式
//定义线程函数传入参数的结构体
typedef struct __TICKET
{int nCount;char strTicketName[NAME_LINE];__TICKET() : nCount(0){memset(strTicketName, 0, NAME_LINE * sizeof(char));}
}TICKET;typedef struct __THD_DATA
{TICKET* pTicket;char strThreadName[NAME_LINE];__THD_DATA() : pTicket(NULL){memset(strThreadName, 0, NAME_LINE * sizeof(char));}
}THD_DATA;//基本类型数据转换成字符串
template<class T>
std::string convertToString(const T val)
{std::string s;std::strstream ss;ss << val;ss >> s;return s;
}
//售票程序
DWORD WINAPI SaleTicket(LPVOID lpParameter);//售票系统
void Test2();// 一个mutex变量控制同一个资源，因此会先打印完*再打印$
// 两个mutex变量则可能出现交替打印，因为不是修改统一资源
std::mutex mtx;  // mutex for critical section
void print_block(int n, char c)
{mtx.lock();for (int i = 0; i<n; i++){std::cout << c;}std::cout << '\n';mtx.unlock();
}
void thread_1()
{std::cout << "子线程1" << std::endl;
}
void thread_2(int x)
{std::cout << "x:" << x << std::endl;std::cout << "子线程2" << std::endl;
}
int f_multi_thread()
{std::thread first(thread_1); // 开启线程，调用：thread_1()std::thread second(thread_2, 100); // 开启线程，调用：thread_2(100)//std::thread third(thread_2,3);//开启第3个线程，共享thread_2函数。std::cout << "主线程\n";first.join(); //join()等待线程结束并清理资源(会阻塞)        second.join();std::cout << "子线程结束.\n";//必须join完成//std::thread th1(print_block, 50, '*');//线程1：打印*//std::thread th2(print_block, 50, '$');//线程2：打印$//th1.join();//th2.join();return 0;
}void threadProc()
{std::cout << "this is in threadProc\n";std::cout << "thread1's id is " << std::this_thread::get_id() << std::endl; //获取所属线程的id
}
void threadProc2(int num)
{std::cout << "thread num = " << num << std::endl;
}
void threadProc3()
{std::cout << "this thread is detached\n";
}
void threadProc4()
{std::cout << "this thread is detached and won't print in the same console.'\n";
}
std::mutex mu;//互斥锁 
void test1()
{for (int i = 0; i < 5; i++){mu.lock();//锁住 std::cout << "test1 i = " << i << std::endl;mu.unlock();//释放 }
}
void test2()
{for (int j = 0; j < 5; j++){mu.lock();std::cout << "test2 j = " << j << std::endl;mu.unlock();}
}
/*
lock_guard<mutex> locka(mu);
作用范围为从这一行开始，到那一次循环结束，还不用自己手动解锁。
*/
void test3()
{for (int i = 0; i < 5; i++){std::lock_guard<std::mutex> locka(mu);std::cout << "test3 i = " << i << std::endl;}
}
void test4()
{for (int j = 0; j < 5; j++){std::lock_guard<std::mutex> lock(mu);std::cout << "test4 j = " << j << std::endl;}
}
void test5()
{for (int i = 0; i < 5; i++){std::unique_lock<std::mutex> locka(mu, std::defer_lock);std::cout << "test5 i = " << i << std::endl;locka.lock();std::cout << "this is lock1" << std::endl;}
}
void test6()
{for (int j = 0; j < 5; j++){std::unique_lock<std::mutex> locka(mu);std::cout << "test6 j = " << j << std::endl;locka.unlock();locka.lock();std::cout << "this is lock2" << std::endl;}
}
std::condition_variable cv;
bool print = false;
void test7()
{for (int i = 0; i < 5; i++){std::unique_lock<std::mutex> l(mu);std::cout << "test7 i = " << i << std::endl;cv.notify_one();print = true;}
}
void test8()
{for (int j = 0; j < 5; j++){std::unique_lock<std::mutex> l(mu);if (!print){cv.wait(l);}std::cout << "test8 j = " << j << std::endl;print = false;}
}CRITICAL_SECTION section;//临界区变量
void test01()
{for (int i = 0; i < 5; i++){EnterCriticalSection(&section);//类似于 mutex.lock() std::cout << "this is test01 i = " << i << std::endl;Sleep(1);LeaveCriticalSection(&section);//类似于 mutex.unlock() }
}
void test02()
{for (int j = 0; j < 5; j++){EnterCriticalSection(&section);std::cout << "this is test02 j = " << j << std::endl;Sleep(1);LeaveCriticalSection(&section);}
}
HANDLE hmutex;
void test03()
{for (int i = 0; i < 5; i++){WaitForSingleObject(hmutex, INFINITE);//类似于mutex.lock() 阻塞等待多少时间 std::cout << "test03 i = " << i << std::endl;ReleaseMutex(hmutex);//类似于mutex.unlock() 释放互斥锁 }
}
void test04()
{for (int j = 0; j < 5; j++){WaitForSingleObject(hmutex, INFINITE);std::cout << "test04 j = " << j << std::endl;ReleaseMutex(hmutex);}
}
HANDLE hevent;
void test05()
{for (int i = 0; i < 5; i++){WaitForSingleObject(hevent, INFINITE);//类似于mutex.lock() 阻塞等待多少时间 std::cout << "test05 i = " << i << std::endl;SetEvent(hevent);//类似于mutex.unlock() 释放互斥锁 }
}
void test06()
{for (int j = 0; j < 5; j++){WaitForSingleObject(hevent, INFINITE);std::cout << "test06 j = " << j << std::endl;SetEvent(hevent);}
}
HANDLE sem;
void test07()
{for (int i = 0; i < 5; i++){WaitForSingleObject(sem, INFINITE);//类似于mutex.lock() 阻塞等待多少时间 std::cout << "test07 i = " << i << std::endl;ReleaseSemaphore(sem, 1, NULL);//类似于mutex.unlock() 释放互斥锁 }
}
void test08()
{for (int j = 0; j < 5; j++){WaitForSingleObject(sem, INFINITE);std::cout << "test08 j = " << j << std::endl;ReleaseSemaphore(sem, 1, NULL);}
}int main(int argc, char const* argv[])
{int i = 0; int rtn = 0;int ret = 0;char buff[100];char *tmp = int2hex(82);//read_csv2();//ok//float num = 0.3;//int result = ceil(num);//printf("向上取整后的结果是：%d\n", result);--------------多线程-----START------------------------//f_multi_thread();//f_multiThread();//【Demo1】：创建一个最简单的线程//f_multiThread2();//【Demo2】：在线程函数中传入参数//f_multiThread3();//【Demo3】：线程同步//售票系统 ////Test2();//【Demo4】：模拟火车售票系统====== C++11 线程库 ==== START ==========//std::thread a;//创建线程1，定义线程，后面再分配任务//a = std::thread(threadProc);//std::thread b(threadProc2, 5);//创建线程2 ，定义线程的时候分配任务，参数类似于printf一样，可以为多个//a.join();//b.join();//采用join，主线程会阻塞等待子线程执行完毕//std::thread c(threadProc3);//c.detach();//采用detach，主线程不会等，这个线程开启早，还能输出到主线程的控制台//std::cout << "main thread exit" << std::endl;//std::thread d(threadProc4);//d.detach();////std::thread a(test1);//std::thread b(test2);//a.join();//b.join();//std::cout << "main thread finish." << std::endl;//std::thread a(test3);//std::thread b(test4);//a.join();//b.join();//std::cout << "main thread finish." << std::endl;//std::thread a(test5);//std::thread b(test6);//a.join();//b.join();//std::thread a(test7);//std::thread b(test8);//a.join();//b.join();====== C++11 线程库 ==== END ================== W32API实现线程同步 ==== START ==========//InitializeCriticalSection(&section);//初始化临界区对象//std::thread a(test01);//std::thread b(test02);//a.join();//b.join();//DeleteCriticalSection(&section);//用完了，就删除临界区 //hmutex = CreateMutex(NULL, FALSE, "mutex");//创建一个互斥锁 //std::thread a(test03);//std::thread b(test04);//a.join();//b.join();//CloseHandle(hmutex);//释放句柄 //hevent = CreateEvent(NULL, FALSE, TRUE, "event");//创建一个事件 //std::thread a(test05);//std::thread b(test06);//a.join();//b.join();//CloseHandle(hevent);//释放句柄 sem = CreateSemaphore(NULL, 1, 2, "semaphore");std::thread a(test07);std::thread b(test08);a.join();b.join();CloseHandle(sem);//释放句柄 ====== W32API实现线程同步 ==== END ============--------------多线程-----END--------------------------VS 与 Matlab 混合编程//rtn = f_VS_Matlab();system("pause");return 0;
}//售票程序
DWORD WINAPI SaleTicket(LPVOID lpParameter)
{THD_DATA* pThreadData = (THD_DATA*)lpParameter;TICKET* pSaleData = pThreadData->pTicket;while (pSaleData->nCount > 0){//请求获得一个互斥量锁WaitForSingleObject(g_hMutex2, INFINITE);if (pSaleData->nCount > 0){std::cout << pThreadData->strThreadName << "出售第" << pSaleData->nCount-- << "的票,";if (pSaleData->nCount >= 0) {std::cout << "出票成功!剩余" << pSaleData->nCount << "张票." << std::endl;}else {std::cout << "出票失败！该票已售完。" << std::endl;}}Sleep(10);//释放互斥量锁ReleaseMutex(g_hMutex2);}return 0L;
}
//售票系统
void Test2()
{//创建一个互斥量g_hMutex2 = CreateMutex(NULL, FALSE, NULL);//初始化火车票TICKET ticket;ticket.nCount = 100;strcpy(ticket.strTicketName, "北京-->赣州");const int THREAD_NUMM = 2;//8;//THD_DATA threadSale[THREAD_NUMM];HANDLE hThread[THREAD_NUMM];for (int i = 0; i < THREAD_NUMM; ++i){threadSale[i].pTicket = &ticket;std::string strThreadName = convertToString(i);strThreadName = "窗口" + strThreadName;strcpy(threadSale[i].strThreadName, strThreadName.c_str());//创建线程hThread[i] = CreateThread(NULL, NULL, SaleTicket, &threadSale[i], 0, NULL);//请求获得一个互斥量锁WaitForSingleObject(g_hMutex2, INFINITE);std::cout << threadSale[i].strThreadName << "开始出售 " << threadSale[i].pTicket->strTicketName << " 的票..." << std::endl;//释放互斥量锁ReleaseMutex(g_hMutex2);//关闭线程CloseHandle(hThread[i]);}system("pause");
}

参考：

【Linux】多线程同步的四种方式 - 西*风 - 博客园 (cnblogs.com)

一文搞定c++多线程同步机制_c++多线程同步等待-CSDN博客

C++多线程同步总结 - 念秋 - 博客园 (cnblogs.com)

Linux 下多线程（C语言） | 大眼睛男孩儿 (zhangxiaoya.github.io)

读写锁 - 张飘扬 - 博客园 (cnblogs.com)

Linux C++多线程同步的四种方式（非常详细）-CSDN博客

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