线程锁 EnterCriticalSection LeaveCriticalSection

  

线程锁的概念函数EnterCriticalSection和LeaveCriticalSection的用法

  注：使用结构CRITICAL_SECTION 需加入头文件#include “afxmt.h”

定义一个全局的锁 CRITICAL_SECTION的实例
和一个静态全局变量

1. CRITICAL_SECTIONcs;         //可以理解为锁定一个资源
2. static intn_AddValue =0;         //定义一个静态的全部变量n_AddValue

创建两个线程函数，代码实现如下：

1. //第一个线程
2. UINT FirstThread(LPVOID lParam)
3. {
4.     EnterCriticalSection(&cs);   //加锁 接下来的代码处理过程中不允许其他线程进行操作，除非遇到LeaveCriticalSection
5.     for(int i = 0; i<10; i++){       
6.         n_AddValue ++;
7.         cout << "n_AddValue in FirstThread is "<<n_AddValue <<endl;       
8.    
9.     }
10.     LeaveCriticalSection(&cs);   //解锁到EnterCriticalSection之间代码资源已经释放了，其他线程可以进行操作   
11.     return 0;
12.  
13. }
14.  
15. //第二个线程
16. UINT SecondThread(LPVOID lParam)
17. {
18.     EnterCriticalSection(&cs);   //加锁
19.     for(int i = 0; i<10; i++){       
20.         n_AddValue ++;       
21.         cout << "n_AddValue in SecondThread is "<<n_AddValue <<endl;   
22.        
23.     }
24.     LeaveCriticalSection(&cs);   //解锁
25.  
26.     return 0;
27.  
28. }

在主函数添加以下代码

1. int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
2. {
3.     int nRetCode = 0;
4.  
5.     // 初始化 MFC 并在失败时显示错误
6.     if (!AfxWinInit(::GetModuleHandle(NULL),NULL, ::GetCommandLine(), 0))
7.     {
8.         // TODO: 更改错误代码以符合您的需要
9.         _tprintf(_T("错误: MFC 初始化失败/n"));
10.         nRetCode = 1;
11.     }
12.     else
13.     {
14.  
15.         InitializeCriticalSection(&cs);      //初始化结构CRITICAL_SECTION
16.  
17.  
18.         CWinThread *pFirstThread,*pSecondThread;//存储函数AfxBeginThread返回的CWinThread指针
19.        
20.  
21.         pFirstThread  = AfxBeginThread(FirstThread,LPVOID(NULL));//启动第一个线程
22.         pSecondThread = AfxBeginThread(SecondThread,LPVOID(NULL));//启动第二个线程
23.  
24.         HANDLE hThreadHandle[2];//
25.         hThreadHandle[0] = pFirstThread->m_hThread;
26.         hThreadHandle[1] = pSecondThread->m_hThread;
27.  
28.         //等待线程返回
29.         WaitForMultipleObjects(2,hThreadHandle,TRUE,INFINITE);       
30.     }
31.  
32.     return nRetCode;
33. }

输出：

n_AddValue in FirstThread is 1
n_AddValue in FirstThread is 2
n_AddValue in FirstThread is 3
n_AddValue in FirstThread is 4
n_AddValue in FirstThread is 5
n_AddValue in FirstThread is 6
n_AddValue in FirstThread is 7
n_AddValue in FirstThread is 8
n_AddValue in FirstThread is 9
n_AddValue in FirstThread is 10
n_AddValue in SecondThread is 11
n_AddValue in SecondThread is 12
n_AddValue in SecondThread is 13
n_AddValue in SecondThread is 14
n_AddValue in SecondThread is 15
n_AddValue in SecondThread is 16
n_AddValue in SecondThread is 17
n_AddValue in SecondThread is 18
n_AddValue in SecondThread is 19
n_AddValue in SecondThread is 20

最后释放临界区:

     DeleteCriticalSection(&cs);