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Multi thread anti conflict

2022-07-21 16:00:00 【51CTO】

He zhidan, software architect

The cause of the conflict

Write CString When , Maybe not enough memory , So release 、 Reallocate memory . Maybe just released , Didn't have time to allocate , It was suspended , Then another thread accesses this variable , It broke down .　

Test instructions

Button18 Tested , No conflict prevention , Program crash .Button19, Tested anti-collision processing , The program didn't crash .Button20, One write lock and several read locks , Faster than writing all locks .SNMFC::CriticalReadWriteLock, Sort out the classes of the class library by yourself .

Test code

       
       class 
       
       CTesNoLock
       
 {
       
       public:
       
       static 
       
       UINT 
       
       Write(
       
       LPVOID)
       
 {
       
       Sleep(
       
       1);
       
       s_str 
       
       += 
       
       _T(
       
       "AB33333333333333333333");
       
       return 
       
       0;
       
 }
       
       static 
       
       UINT 
       
       Read(
       
       LPVOID)
       
 {
       
       Sleep(
       
       1);
       
       bool 
       
       b 
       
       = 
       
       s_str[
       
       0] 
       
       == 
       
       _T(
       
       'A');
       
       ASSERT(
       
       b);
       
       return 
       
       0;
       
 }
       
       protected:
       
       static 
       
       CString 
       
       s_str;
       
 };
       
       CString 
       
       CTesNoLock::
       
       s_str 
       
       = 
       
       "A";
       
       class 
       
       CTesReadWriteLock : 
       
       public 
       
       CTesNoLock
       
 {
       
       public:
       
       static 
       
       UINT 
       
       LockWrite(
       
       LPVOID)
       
 {
       
       s_lock.
       
       Lock();
       
       Write(
       
       NULL);
       
       s_lock.
       
       UnLock();
       
       return 
       
       0;
       
 }
       
       static 
       
       UINT 
       
       LockRead(
       
       LPVOID)
       
 {
       
       s_lock.
       
       LockRead();
       
       Read(
       
       NULL);
       
       s_lock.
       
       UnLockRead();
       
       return 
       
       0;
       
 }
       
       static 
       
       UINT 
       
       LockWrite100ms(
       
       LPVOID)
       
 {
       
       s_lock.
       
       Lock();
       
       Sleep(
       
       100);
       
       s_lock.
       
       UnLock();
       
       return 
       
       0;
       
 }
       
       static 
       
       UINT 
       
       LockRead100ms(
       
       LPVOID)
       
 {
       
       s_lock.
       
       LockRead();
       
       Sleep(
       
       100);
       
       s_lock.
       
       UnLockRead();
       
       return 
       
       0;
       
 }
       
       protected:
       
       static 
       
       SNMFC::
       
       CriticalReadWriteLock 
       
       s_lock;
       
 };
       
       SNMFC::
       
       CriticalReadWriteLock 
       
       CTesReadWriteLock::
       
       s_lock;
       
       void 
       
       CSNMFCDlg::
       
       OnBnClickedButton18()
       
 {
       
       CTesNoLock::
       
       Write(
       
       NULL);
       
       for (
       
       int 
       
       i 
       
       = 
       
       0; 
       
       i 
       
       < 
       
       1000; 
       
       i
       
       ++)
       
 {
       
       AfxBeginThread(
       
       CTesNoLock::
       
       Write, 
       
       NULL);
       
       AfxBeginThread(
       
       CTesNoLock::
       
       Read, 
       
       NULL);
       
 }
       
 }
       
       void 
       
       CSNMFCDlg::
       
       OnBnClickedButton19()
       
 {
       
       for (
       
       int 
       
       i 
       
       = 
       
       0; 
       
       i 
       
       < 
       
       10; 
       
       i
       
       ++)
       
 {
       
       AfxBeginThread(
       
       CTesReadWriteLock::
       
       LockWrite, 
       
       NULL);
       
       for (
       
       int 
       
       j 
       
       = 
       
       0; 
       
       j 
       
       < 
       
       1000; 
       
       j
       
       ++)
       
 {
       
       AfxBeginThread(
       
       CTesReadWriteLock::
       
       LockRead, 
       
       NULL);
       
 }
       
 }
       
 }
       
       void 
       
       CSNMFCDlg::
       
       OnBnClickedButton20()
       
 {
       
       DWORD 
       
       d1 
       
       = 
       
       GetTickCount();
       
 {
       
       // Due to being locked , Can only be accessed sequentially , Time usage 10 second 
       
       for (
       
       int 
       
       i 
       
       = 
       
       0; 
       
       i 
       
       < 
       
       99; 
       
       i
       
       ++)
       
 {
       
       AfxBeginThread(
       
       CTesReadWriteLock::
       
       LockWrite100ms, 
       
       NULL);
       
 }
       
 }
       
       CTesReadWriteLock::
       
       LockWrite100ms(
       
       NULL);
       
       DWORD 
       
       d2 
       
       = 
       
       GetTickCount();
       
 {
       
       // You can read it at the same time , So it takes much less time 
       
       for (
       
       int 
       
       i 
       
       = 
       
       0; 
       
       i 
       
       < 
       
       99; 
       
       i
       
       ++)
       
 {
       
       AfxBeginThread(
       
       CTesReadWriteLock::
       
       LockRead100ms, 
       
       NULL);
       
 }
       
 }
       
       CTesReadWriteLock::
       
       LockWrite100ms(
       
       NULL);
       
       DWORD 
       
       d3 
       
       = 
       
       GetTickCount();
       
       ASSERT((
       
       d2 
       
       - 
       
       d1) 
       
       >(
       
       d3 
       
       - 
       
       d2) 
       
       * 
       
       2);
       
 }
      
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版权声明
本文为[51CTO]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/202/202207202117234258.html

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