Subj : Re: Return value from worker thred when the working thread must be suspend after calculation???
To   : comp.os.ms-windows.programmer.win32,microsoft.public.vc.language,comp.programming.threads
From : David W. Poole, Jr.
Date : Tue Aug 30 2005 02:28 am

On Mon, 29 Aug 2005 22:14:25 -0700, "Alexander Grigoriev"
<alegr@earthlink.net> was understood to have stated the following:

>You should not access windows of the main thread from the secondary thread. 
>This may lead to deadlocks. Use PostMessage to communicate between threads.

Ok, I'll buy using PostMessage() over SendMessage() to have a worker
thread update the user interface as a safer alternative.

Of personal interest though is how this can lead to a deadlock
condition. In the applications where I utilize this technique, when a
worker thread is initiated, the parameters are read from the
appropriate controls, and the values are stuffed into a structure that
is passed to the worker thread. Thus, the worker thread no longer
requires any input from the user interface; it only needs to update
the UI on occasion; say for progress information while the thread is
active, and for parametric information upon the thread's completion.
How can this lead to a deadlock, even with SendMessage(), as the
worker thread never tries to obtain information from the user
interface? There's never anything the worker thread is waiting on, and
the user interface thread doesn't have any code other than the code
that very quickly handles messages?

.