OnTimer and multithreading

In general, opening a UI thread in MFC can use the following code:

M_pcamerathread = AfxBeginThread (runtime_class (Ccamerathread)); if (!m_pcamerathread->postthreadmessage (um_verify_availability, NULL, NULL)) {    Sleep (  );}

However, in a case in OnTimer, it is not possible to start two of these UI threads in sequence at the same time, it is recommended that different UI threads be started in different cases in order, or the most likely exception in ***.exe will appear under Debug 0x*****: 0XC0000005: An access violation occurred while reading the location 0x******. And the release does not appear. This conflict is not caused by a conventional pointer crossing, which is very difficult to debug. The reason for the above error may be that the OnTimer function itself is not multi-threaded!

OnTimer and multithreading