AVR-Chat

>
>If the point of your message is to take issue with my claim that it 
>is not necessary to poll, then I give up. You win. It is possible to 
>define polling such that polling is necessary. I don't care how; 
>picking at terminology is not interesting to me.

If I'm understanding it right, in your case, a timer schedules your re-evaluation of which tasks should be running/queued.  During that timer int, you do what I do, in that you examine semaphores to see what's ready, what's done, what's empty, etc..
(pre-emptive multitasking?)

In my case, I run a task to completion, with an eye to completing it as soon as possible.
When any task ends, then in the case of a round-robin, the next task tries to run.
If it can't proceed for whatever reason, then I pass to the next task, and so on. 
Interrupts, in my case, are either a system timer (clock-ish timekeeping) or physical events.
(cooperative multitasking)

I arrange the order of my tasks in the round-robin system such that the low level functions happen first, then the higher levels, because the higher levels depend on events that happen in the lower levels.

Alternately, I can re-start from the beginning in which case high priority tasks (those that sit early in the idle loop) can prevent lower priority tasks from running by chewing up all the time.