C++多线程同步总结

2024-06-07 17:53
objective-c, ios, cocoa, macos
34人已看

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)

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