Question

If I have the following C++ code (for Windows Os):

HANDLE hEvent = ::CreateEvent(NULL, TRUE, FALSE, NULL);
HANDLE hMutex = ::CreateMutex(NULL, FALSE, NULL);

HANDLE hHandles[] = {
    hEvent,
    hMutex
};

DWORD dwR = ::WaitForMultipleObjects(2, hHandles, FALSE, INFINITE) - WAIT_OBJECT_0;

//if dwR == 0, what state is hMutex in?
//Or, do I need to call ReleaseMutex(hMutex) in that case?

I’m not sure how to handle this situation regarding the mutex.

Answer 1

dwR is not quite zero, it is WAIT_OBJECT_0 + 0, that is your wait was satisfied on the first provided handle. This is event’s handle, so you don’t need to touch your mutex.

If result is WAIT_OBJECT_0 + 1 then it was mutex handle used to succeed in waiting. And once you are done with things you need to do, you release the ownership by calling ReleaseMutex.