用关键段实现线程同步
下面是一段用关键段实现线程同步的例子：
//关键段测试代码
#include <iostream>
#include <windows.h>
using namespace std;
CRITICAL_SECTION g_cs;//创建CRITICAL_SECTION结构全局变量
int g_x = 50;
//线程函数1
DWORD WINAPI ThreadFunc1(LPVOID lpParam)
{
while(TRUE)
{
EnterCriticalSection(&g_cs);
cout << "Thread1 get the access to resource" << endl;
if(g_x > 25)
{
Sleep(1);
cout<<"thread1 sell ticket : "<<g_x--<<endl;
}
else
break;
LeaveCriticalSection(&g_cs);
}
return 0;
}
//线程函数2
DWORD WINAPI ThreadFunc2(LPVOID lpParameter)
{
while(TRUE)
{
EnterCriticalSection(&g_cs);
cout << "Thread2 get the access to resource" << endl;
if(g_x > 0)
{
Sleep(1);
cout<<"thread2 sell ticket : "<<g_x--<<endl;
}
else
break;
LeaveCriticalSection(&g_cs);
}
return 0;
}
int main()
{
HANDLE hThread1;
HANDLE hThread2;
InitializeCriticalSection(&g_cs);
hThread1=CreateThread(NULL,0,ThreadFunc1,NULL,0,NULL);
hThread2=CreateThread(NULL,0,ThreadFunc2,NULL,0,NULL);
CloseHandle(hThread1);
CloseHandle(hThread2);
Sleep(4000);
DeleteCriticalSection(&g_cs);
return 0;
}
我在CodeBlocks上面运行这段代码，发现总是只有一个线程函数得以执行，一个线程执行完毕之后就返回了，为什么另外一个线程得不到执行呢？这是为什么呢？运行结果：
loli控.
13 years, 5 months ago
Answers
线程1 break后没有LeaveCriticalSection，导致了问题。
两个线程中都添加类似下面的处理
//线程函数1
DWORD WINAPI ThreadFunc1(LPVOID lpParam)
{
while(TRUE)
{
EnterCriticalSection(&g_cs);
cout << "Thread1 get the access to resource" << endl;
if(g_x > 25)
{
Sleep(10);
cout<<"thread1 sell ticket : "<<g_x--<<endl;
}
else
{
LeaveCriticalSection(&g_cs);//add
break;
}
LeaveCriticalSection(&g_cs);
}
cout << "Thread1 exit" << endl;
return 0;
}
畸智的傻逼
answered 13 years, 5 months ago