线程同步的问题急

2009-06-07 08:47:09 155 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

使用 Linux 系统提供的线程同步 API 解决线程同步问题一、用信号量完成四个线程的同步。主程序创建四个线程，其中两个线程负责从文件读取数据到公共缓冲区，另两个线程从缓冲区读取数据分别做加、乘运算。运行程序之前先编辑好数据文件 file1.dat 和 file2.dat，分别输入 1 2 3 4 5 6 7 8 9 10 和-1 -2 -3 -4 -5 -6 -7 -8 -9 -10。阅读详情

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

#include "MyThread.h"

int readercount=0;//读者个数
HANDLE hMutex_R_W=CreateMutex(NULL,false,"r_w");
HANDLE hMutex_ReaderCount=CreateMutex(NULL,false,"readercount");

void main()
{
/*MyThread my_thread_1(1,'R',3,5);
MyThread my_thread_2(2,'W',4,5);
MyThread my_thread_3(3,'R',5,2);
MyThread my_thread_4(4,'R',6,5);
MyThread my_thread_5(5,'W',5.1,3);*/

DWORD WINAPI Function_0(LPVOID);
DWORD WINAPI Function_1(LPVOID);
DWORD WINAPI Function_2(LPVOID);
DWORD WINAPI Function_3(LPVOID);
DWORD WINAPI Function_4(LPVOID);

HANDLE my_threads[5];
my_threads[0]=CreateThread(NULL,0,Function_0,NULL,0,NULL);
my_threads[1]=CreateThread(NULL,0,Function_1,NULL,0,NULL);
my_threads[2]=CreateThread(NULL,0,Function_2,NULL,0,NULL);
my_threads[3]=CreateThread(NULL,0,Function_3,NULL,0,NULL);
my_threads[4]=CreateThread(NULL,0,Function_4,NULL,0,NULL);
WaitForMultipleObjects(5,my_threads,TRUE,INFINITE);
cout<<"haha"<<endl;

}

DWORD WINAPI Function_0(LPVOID)
{
cout<<"线程1被创建"<<endl;
Sleep(300);
cout<<"线程1申请读操作"<<endl;
WaitForSingleObject(hMutex_ReaderCount,INFINITE);

readercount++;
if(readercount==1)
WaitForSingleObject(hMutex_R_W,INFINITE);

ReleaseMutex(hMutex_ReaderCount);
cout<<"线程1开始进行读操作"<<endl;
Sleep(500);
cout<<"线程1结束读操作"<<endl;
WaitForSingleObject(hMutex_ReaderCount,INFINITE);
readercount--;
//cout<<"1:"<<readercount<<endl;
if(readercount==0)
{
//cout<<"shit"<<1<<endl;
ReleaseMutex(hMutex_R_W);
}
ReleaseMutex(hMutex_ReaderCount);
return 0;
}

DWORD WINAPI Function_1(LPVOID)
{
cout<<"线程2被创建"<<endl;
Sleep(400);
cout<<"线程2申请写操作"<<endl;

WaitForSingleObject(hMutex_R_W,INFINITE);

//cout<<"&"<<readercount<<endl;
cout<<"线程2开始进行写操作"<<endl;
Sleep(500);
cout<<"线程2结束写操作"<<endl;
ReleaseMutex(hMutex_R_W);

return 0;
}

DWORD WINAPI Function_2(LPVOID)
{
cout<<"线程3被创建"<<endl;
Sleep(500);
cout<<"线程3申请读操作"<<endl;
WaitForSingleObject(hMutex_ReaderCount,INFINITE);

readercount++;
if(readercount==1)
WaitForSingleObject(hMutex_R_W,INFINITE);

ReleaseMutex(hMutex_ReaderCount);
cout<<"线程3开始进行读操作"<<endl;
Sleep(200);
cout<<"线程3结束读操作"<<endl;
WaitForSingleObject(hMutex_ReaderCount,INFINITE);

readercount--;
// cout<<"3:"<<readercount<<endl;
if(readercount==0)
{
//cout<<"shit"<<3<<endl;
ReleaseMutex(hMutex_R_W);
}
ReleaseMutex(hMutex_ReaderCount);
return 0;
}

DWORD WINAPI Function_3(LPVOID)
{
cout<<"线程4被创建"<<endl;
Sleep(600);
cout<<"线程4申请读操作"<<endl;
WaitForSingleObject(hMutex_ReaderCount,INFINITE);

readercount++;
if(readercount==1)
WaitForSingleObject(hMutex_R_W,INFINITE);

ReleaseMutex(hMutex_ReaderCount);
cout<<"线程4开始进行读操作"<<endl;
Sleep(500);
cout<<"线程4结束读操作"<<endl;
WaitForSingleObject(hMutex_ReaderCount,INFINITE);

readercount--;
//cout<<"4:"<<readercount<<endl;
if(readercount==0)
{
//cout<<"shit"<<4<<endl;
ReleaseMutex(hMutex_R_W);
}
ReleaseMutex(hMutex_ReaderCount);
return 0;
}

DWORD WINAPI Function_4(LPVOID)
{
cout<<"线程5被创建"<<endl;
Sleep(510);
cout<<"线程5申请写操作"<<endl;
WaitForSingleObject(hMutex_R_W,INFINITE);

// cout<<"#"<<readercount<<endl;
cout<<"线程5开始进行写操作"<<endl;
Sleep(300);
cout<<"线程5结束写操作"<<endl;
ReleaseMutex(hMutex_R_W);
return 0;
}
运行结果是
线程1申请读操作
线程1开始进行读操作
线程2申请写操作
线程3申请读操作
线程3开始进行读操作
线程5申请写操作
线程4申请读操作
线程4开始进行读操作
线程3结束读操作
线程1结束读操作
线程2开始进行写操作
线程4结束读操作
线程2结束写操作
线程5开始进行写操作
线程5结束写操作

结果存在的问题是在线程1结束读操作后线程2就进行了写操作
按照程序的逻辑应该是在线程4结束读操作后readercount==0后执行ReleaseMutex(hMutex_R_W);
然后线程2的WaitForSingleObject(hMutex_R_W,INFINITE);才有返回，才能执行，请高手们指教，另外我已经将编译选项里的MLd改成了MTd

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