Scheduler and Job handling
==========================

The purpose of the _Scheduler_ is to run small self contained _Jobs_
ordered by priority and observing specific timing constraints.

Scheduler implementation ideas
------------------------------

Use multiple priority queues

- background work
- foreground high-priority
- soft-realtime actions

About Jobs
----------
A job is a closure to run a small and limited action or operation, which
in itself _should not block_. Job may depend on each other and on resources
to be provided. A job may be conained in multiple queues and may be marked
as _canceled_ -- in which case the job function will never run and the job
will be discarded on occasion.

Job States
~~~~~~~~~~

[source,C]
--------------
enum job_state
{ 
  done,         // already done, nothing to do
  running,      // job is running 
  waiting,      // waits for some resource (annother job)
  rejected,     // sorry, cant do that dave, time will run out
  expired,      // time expired
  aborted       // got aborted
}
--------------