Re: returning from worker thread

From:
"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Newsgroups:
microsoft.public.vc.mfc
Date:
Tue, 15 Aug 2006 09:30:38 -0400
Message-ID:
<e7DX87GwGHA.1772@TK2MSFTNGP06.phx.gbl>
Steve Russell wrote:

1) I will be moving my audio thread pointer to become a member of my view.
But even then, I was thinking that it was better not to call the audio
class' CleanUp function and the view's AudioSignal function from within the
thread, but rather to leave the worker thread as soon as possible and do the
other tasks in the main thread. My thinking has been that it is better to
let the audio thread function basically act as a switch and not much more;
and also that it was somehow safer to let the other classes do their work in
the main thread. I believe there is both truth and fiction in this mindset.
Can you comment?


Sounds like superstition. What is preferred is to minimize interactions
between threads because they are always tricky and potential trouble
spots. I nice ideal would be an audio thread that contains all
interactions with the audio APIs.

2) What's wrong, at shutdown, with signaling the audio thread's WFSO (which
waits for the audio event handle) with SetEvent? With the help of just one
more flag variable, the switch statement could then determine whether audio
has been interrupted or not and then take the appropriate action before
returning zero? Although I have my code torn apart right now, I have been
using something like this inside the audio class, which currently owns the
thread pointer:

 DWORD threadstatus;
 if(m_pAudioThread)
 {
  ::GetExitCodeThread(m_pAudioThread->m_hThread, &threadstatus);
  if(threadstatus == STILL_ACTIVE)
  {
    Interrupt(2); // signal audio thread
    ::WaitForSingleObject(m_pAudioThread->m_hThread,50);
  }
 }


Trouble with interthread interactions example: After you call
GetExitCodeThread, but before you test the result, the thread state
could change. Ordinary step-by-step code is unreliable when dealing
with interthread interactions.

--
Scott McPhillips [VC++ MVP]

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