Re: returning from worker thread

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sat, 12 Aug 2006 17:41:42 -0400

Message-ID:

<#vaXOglvGHA.5056@TK2MSFTNGP06.phx.gbl>

Steve Russell wrote:

I realize my posts in this thread are possibly becoming an annoyance as I
juggle and struggle among varying issues and code attempts. But this
particular question is not related to shutdown, which actually was provided
for before experimenting with the advice I have received. May I ask this --
Assuming that my audio class waveOut calls m_pAudioThread->ResumeThread(),
is there anything in my worker thread function below that would appear
problematic specifically in relation to being able to post a message to my
view and retain valid pointers?

UINT AudioThreadFunc(LPVOID pParam)
{
while(TRUE)
{
CAudioFile* audiofile = (CAudioFile*)pParam;
if(WaitForSingleObject(audiofile->m_hndDone,INFINITE) != WAIT_OBJECT_0)
  // error handling goes here
  return 0;
}
CloseHandle(audiofile->m_hndDone);
if(audiofile->m_pView->m_hWnd)
    audiofile->m_pView->PostMessage(WM_AUDIO_CLEANUP, 1); // handler
calls m_pAudioFile->AudioCleanUp()
else
  audiofile->AudioCleanUp(false);

::SuspendThread(audiofile->m_pAudioThread->m_hThread);
}
return 0;
}

It is very hard to say without understanding all your variables. It
looks strange that the thread is a member of a file. It looks strange
that you assign audiofile = pParam inside the loop when pParam will
never change. It looks strange that you close a handle inside a
while(TRUE) loop that reuses it. It looks strange that you use
SuspendThread, in light of previous comments about race conditions. It
looks strange that you have two ways to do AudioCleanUp. Obviously,
that should become unnecessary when the design is right. Pretty hard to
intuit what's actually going wrong here with limited information.

The view pointer comes from audiofile->m_pView. Does audiofile get
reallocated for each audio file? Perhaps the old thread func received
the new pointer each time, but you haven't realized the new thread func
receives it only once?

P.S. No annoyance :) You're obviously working hard with difficult concepts.

--
Scott McPhillips [VC++ MVP]