Re: EXE COM Singleton

From:

"Alexander Nickolov" <agnickolov@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Thu, 17 Aug 2006 09:32:37 -0700

Message-ID:

<ufP5ArhwGHA.560@TK2MSFTNGP05.phx.gbl>

Stop wasting time right here. The singleton on its own cannot
be responsible for a deadlock. It's something in your code.
Check what that function is waiting on (mutex or some such)
and see what other blocked thread holds the mutex (or whatever)
while waiting on something else.

BTW, if your server is free-threaded, and you never create
STAs in it, you don't need GIT. Just an observation, not
related to your deadlock...

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================

"Aaron Smith" <AaronSmith@somewhere.com> wrote in message
news:etWSU$gwGHA.1888@TK2MSFTNGP03.phx.gbl...

I've been working on an "Audio Router" for the last couple of years. Its
been in production code for the last year. Now all of a sudden we are
starting to see deadlocks. I was most definitely a beginner when I
started the project and still have a lot to learn.

The Audio Router is implemented as an out of process COM server, singleton
(using DECLARE_CLASSFACTORY_SINGLETON) using MTA thread model. I had to
make this a singleton so multiple clients can have access to the
microphone and sound buffers. The clients control the publish/subscribe
states for audio to multiple DirectPlay groups my making calls on the
Audio Router. As specific events happen (received from a DirectPlay
message handler) callbacks are made to the clients through a provided
callback interface (the callback interfaces are stored in a global
interface table). When things reach a deadlock state, I can step into the
debugger and see that several threads are stopped while invoking a
function on Audio Router (some threads start from the DirectPlay callback,
others start from clients calling into Audio Router).

With that said, I have to assume that this is an issue of making Audio
Router a singleton. I have seen allot about not using singletons, but
that it could be done using an EXE COM Server... if done properly. Can
anyone point me to a resource that would explain the "done properly" part.
I've also read that singletons are not necessary if you use static or
global member variables. Will this work if I create a "Audio Router
Factory" (not an actual COM factory) that wraps a static pointer to the
Audio Router interface. Then provide a "get interface" method to return
the interface properly marshaled for the calling thread?

Thanks in advance,
Aaron Smith