Re: How to: communication between multiple tasks using protected objects - with no polling?

[Esa Riihonen <esa.riihonen.er@gmail.com>]

torstai 22. tammikuuta 2015 1.22.45 UTC+2 Hubert kirjoitti:
> the point of a protected object here is that the code each task spends 
> in it should be small, just enough to add an entry to a list or so.
> When you send a message to a task, it can be that the task is involved 
> in a lengthy operatin and thus your task has  to wait until the received 
> task can accept it.
> 
> You could also make a more complex setup, perhaps something like
> 
> Tx1 -> Pox1 -> Tx2 -> Po-final ->Tfinal
> Ty2 -> Poy2 -> Ty2 ^
> 
> and then Have one output PO per worker task and each has it's own task 
> to forward the data to the final PO from which the final task fetches it 
> or so.
> The Ada tasking system is easy enough to use to set up stuff like this 
> pretty quickly and when tasks sleep waiting for an entry they dont eat time.

That surely looks promising - AFAICT this was the model that someone other was also proposing "forwarder tasks".

> Just you have to be careful about the maximimum NOF tasks your system 
> can support which is, I believe, depended on the underlying OS. But in 
> my experience a few dozen are not problem, pehraps even a few 100, 
> depending on how much stack each underlying thread reserves. But I 
> wasn't able to get any hard data on that.

My C-program consists of something like 10 processes currently. So, even if I end up to a full scale Ada implementation with added forwarder tasks, we are still speaking of about a couple of dozen tasks max.

Thanks alot again for the insight.