reason for dead lock, dead looping?

It seems not everything can be solved by normal windows api.

Like WaitForInputIdle(), even it works well.  Like while()-slee() insead. There is still a problem there.

After I got the handle to window class of the new child process's thread's window.

When I move the child process 's window, it can cause dead-lock with some unclear reason.

Because I don't know the routine of the child process window's initiation.

The parent process operating on SetWindowLong(m_hWndChild, ... ) caused the child gui program into dead-lock state

in some sistuations, not always.

I should really hijack api.