Thread communication confusion

[bgowland]

I probably should know how to do this but I've managed to wrap my brain in knots trying various things.

I have a situation where my main process thread creates a new thread that mostly sits around doing nothing until a specific time. At that point it needs to 'talk' to the main thread by passing some data so the main thread can act on it.

What's the best way to pass information back to the main thread in this way? I'm running myself round in circles. :confused:

Cheers,
Brian

[sub]

Its not an easy question to answer. There are lots of ways of doing it.

I quite often use a Queue class with synchronized access to it. ie, main thread periodically polls for new object on the queue (locking access before checking, pulling object off the queue if present, then unlocking). The processing thread would lock the queue, place the object on the queue, then unlock the queue.

[bgowland]

Its not an easy question to answer. There are lots of ways of doing it.

LOL - I just wish I could find ONE that works.

I quite often use a Queue class with synchronized access to it.

Thanks - I'll take a look to see if that works for me although I'm looking more for an event type of situation where the worker thread notifies the main thread immediately. I haven't had any luck with cross-thread eventing though - not sure if it's possible. I've also looked at async callbacks but I'm not sure if they're quite what I want either.

Cheers,
Brian

[sub]

Is the main thread blocked waiting for the event to occur, or is it busy doing other stuff? If its not blocked, then I'm not sure you're going to find what you're looking for.

[Old Dog]

You could define a custom Windows Message. Post the message from the worker and have a message handler in the main thread. But I wouldn't usually do it this way as I lack confidence in Window's main message queue.

What is the main thread doing when time lapses?

What will happen to the data?

[bgowland]

The main process thread is a system service that does nothing but create other threads and is blocked by at least one of those threads being in existence.

It's the DVB Radio plugin/add-in that I've been working on over the past. I figured the only way to do this would be to have an ancillary service and talk to that service from a GB-PVR plugin that uses a TcpChannel to provide recording requests. The server-side of the TcpChannel is hosted by a listener thread spawned from the main service thread and I need the listener to tell the main thread that it has received a recording request/cancellation etc.

I don't want the listener to process the command/request directly - just identify what type it is and pass it back to the main thread so that it can act on it appropriately.

I'm not sure I have the model quite right in my head. Perhaps I need to go back to the drawing board.

Cheers,
Brian

[bgowland]

You could define a custom Windows Message.

Yep - I thought about IPC but I'm trying to do this in what I see as a .NET / managed code sort of way. Windows messaging reminds me too much of the Win32 API and when I used to programme with C/C++ (the unmanaged variety). I figured there must be a cleaner way of doing this.

As I said in the previous post - the more I think about it the more I think I've got my model wrong.

This calls for my bean-bag, headphones, beer and heavy rock.

Cheers,
Brian

[23skidoo]

A quick-and-dirty strategy that works in many situations is to declare static variables.

(EDIT: Thinking C++ and C# here. But I'm sure there's plenty of easy IPC stuff in the .Net framework (e.g. semaphores).

[Boy I'm late to the party. Bored. :-) ]