临界区

 #include <windows.h>                                      
#include <iostream>
using namespace std;
//首先做两个线程，实现两个线程间的同步 上次是利用互斥对象实现线程间的同步CreateMutex函数和事件对象间的同步CreateEvent函数，这次用关键代码段(临界区对象)来实现
DWORD WINAPI Fun1Proc(LPVOID lpParameter);                                   
DWORD WINAPI Fun2Proc(LPVOID lpParameter);               

int tickets=100;
CRITICAL_SECTION g_cs;                                  //1.定义一个临界区对象

void main()                                              
{
HANDLE hThread1;                                      
HANDLE hThread2;                                    
hThread1=CreateThread(NULL,0,Fun1Proc,NULL,0,NULL);   
hThread2=CreateThread(NULL,0,Fun2Proc,NULL,0,NULL);   
CloseHandle(hThread1);                              
CloseHandle(hThread2);                               


InitializeCriticalSection(&g_cs);                     //2.初始化临界对象
Sleep(4000);                   
DeleteCriticalSection(&g_cs);                         //3.当函数要结束的时候释放所有没有被拥有的临界区对象相关的成员                     
}


DWORD WINAPI Fun1Proc(LPVOID lpParameter)                       
{                                                              


while(TRUE)                                         
{
EnterCriticalSection(&g_cs);                    //4.判断是否有线程在访问公共资源,如果有线程正在访问就，不能执行下面的                                                       
if(tickets>0)
{
Sleep(1);                                     
cout<<"Thread1 sell tickets:"<<tickets--<<endl;
}
else
break;
LeaveCriticalSection(&g_cs);                    //5.执行完代码段的就离开临界区，那么下个线程就可以访问资源了，这就好像我们要用公用电话(共有资源)，我们必须先看看电话厅里是否有人，有人就不能此时用，没人就可以用这个资源了
}
//7.注意一定要释放，否则线程2就没有执行的机会 “谁拥有谁释放”
return 0;                                             
}                                                         


DWORD WINAPI Fun2Proc(LPVOID lpParameter)                
{

while(TRUE)                                          
{
EnterCriticalSection(&g_cs);                            
if(tickets>0)
{
Sleep(1);                                    
cout<<"Thread2 sell tickets:"<<tickets--<<endl;
}
else
break;
LeaveCriticalSection(&g_cs);                    //8.我们可以将线程2注释起来看看，运行发现，线程1卖出第100张后不再卖了，其余的都是线程2卖的                        

}
return 0;                                          //6.程序这样执行，同步建立了。没有出现重复和0的票号                     

}