一个线程写完数据后，另外三个线程按顺序读取_一个线程写完后,另一个线程读取相同地址数据,会有问题呢-优快云博客

本文链接：https://blog.youkuaiyun.com/tkp2014/article/details/46594763

本文通过一个具体的C++实现案例，介绍了如何利用信号量、互斥锁等手段，在多线程环境中实现数据的安全访问和线程间的同步。具体地，一个写线程负责向缓冲区写入数据，而三个读线程则在数据写入后依次进行读取操作。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

#include <Windows.h>
#include <process.h>
#include <iostream>

using namespace std;

// write线程写了之后，read1、read2、read3才能读，且只有3个线程都读完之后，write函数才能向buffer中写
CRITICAL_SECTION cs;
typedef struct 
{
	HANDLE h1;
	HANDLE h2;
	HANDLE h3;
	HANDLE h4;
	int a;
} PARAMS, *PPARAMS;

void read1(PVOID pvoid)
{
	while (TRUE)
	{
		volatile PPARAMS pparams = (PPARAMS)pvoid;
		WaitForSingleObject(pparams->h2, INFINITE); //一直等待，直到h2指代的对象被触发
		EnterCriticalSection(&cs);
		cout << "线程1开始读取...\n";
		cout << (pparams->a) <<endl;
		LeaveCriticalSection(&cs);
		Sleep(1000);
		ReleaseSemaphore(pparams->h3, 1, NULL);
		ReleaseSemaphore(pparams->h1, 1, NULL); //释放一个信号量
	}
}

void read2(PVOID pvoid)
{
	while (TRUE)
	{
		volatile PPARAMS pparams = (PPARAMS)pvoid;
		WaitForSingleObject(pparams->h3, INFINITE);
		EnterCriticalSection(&cs);
		cout << "线程2开始读取...\n";
		cout << (pparams->a) << endl;
		LeaveCriticalSection(&cs);
		Sleep(1000);
		ReleaseSemaphore(pparams->h4, 1, NULL);
		ReleaseSemaphore(pparams->h1, 1, NULL); //释放一个信号量
	}
}

void read3(PVOID pvoid)
{
	while (TRUE)
	{
		volatile PPARAMS pparams = (PPARAMS)pvoid;
		WaitForSingleObject(pparams->h4, INFINITE);
		EnterCriticalSection(&cs);
		cout << "线程3开始读取...\n";
		cout << (pparams->a) << endl;
		LeaveCriticalSection(&cs);
		Sleep(1000);
		ReleaseSemaphore(pparams->h1,1, NULL); //释放一个信号量，h1， 加1
	}
}

void write(PVOID pvoid)
{
	while (TRUE)
	{
		volatile PPARAMS pparams = (PPARAMS)pvoid;
		WaitForSingleObject(pparams->h1, INFINITE); // 等到后，就减去一个信号
		WaitForSingleObject(pparams->h1, INFINITE);
		WaitForSingleObject(pparams->h1, INFINITE);
		cout << "======================\n";
		cout << "写线程开始写入...\n";
		pparams->a = rand()%256;
		cout << "写入" << (pparams->a) << endl;
		ReleaseSemaphore(pparams->h2, 1, NULL);
//		ReleaseSemaphore(pparams->h3, 1, NULL);
//		ReleaseSemaphore(pparams->h4, 1, NULL);
	}
}


int main()
{
	PARAMS params;
	params.h1 = CreateSemaphore(NULL, 3, 3, NULL); //最开始有3，最大有3
	params.h2 = CreateSemaphore(NULL, 0, 1, NULL); //最开始有0，最大有1
	params.h3 = CreateSemaphore(NULL, 0, 1, NULL); //最开始有0，最大有1
	params.h4 = CreateSemaphore(NULL, 0, 1, NULL); //最开始有0，最大有1

	InitializeCriticalSection(&cs);
	_beginthread(read1, 0, &params);
	_beginthread(read2, 0, &params);
	_beginthread(read3, 0, &params);
	_beginthread(write, 0, &params);

	// HANDLE hEvent;
	// hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
	// WaitForSingleObject(hEvent, INFINITE);
	int a;
	cin>>a;
	DeleteCriticalSection(&cs);
//	system("pause");

	return 0;
}