Suspending a thread that has a synchronizing object is dangerous
The SuspendThread function suspends the specified thread.
DWORD SuspendThread( HANDLE hThread );
This function is primarily designed for use by debuggers. It is not intended to be used for thread synchronization. Calling SuspendThread on a thread that owns a synchronization object, such as a mutex or critical section, can lead to a deadlock if the calling thread tries to obtain a synchronization object owned by a suspended thread. To avoid this situation, a thread within an application that is not a debugger should signal the other thread to suspend itself. The target thread must be designed to watch for this signal and respond appropriately.
---- from MSDN
Sample of suspending a thread owns a mutex
This sample creates two threads, each drawing a circle synchronizing by a mutex.
when the thread locked the mutex, the circle is drawn in black; the circle is drawn white when mutex unlocked.
If you suspend thread 1 when it locks the mutex, the thread 2 is blocked too.