Igor Stasenko wrote:
> I came to an idea , you might be interested in.
> As many of us know, some CPUs having a special mode - interrupt mode.
> What if we introduce the interrupt mode for scheduler?
[... snip ...]
> Now i trying to imagine, how a basic stuff might look like(please
> correct me if its utterly wrong way ;), if we will be able to use
> interrupt mode.

This is actually along similar lines of thought that I had when I was 
thinking of how to get rid of the builtin VM scheduling behavior. The 
main thought that I had was that the VM may have a "special" process - 
the scheduler process (duh!) which it runs when it doesn't know what 
else to do. The VM would then not directly schedule processes after 
semaphore signals but rather put them onto a "ready" queue that can be 
read by the scheduler process and switch to the scheduler process. The 
scheduler process decides what to run next and resumes the process via a 
primitive. Whenever an external signal comes in, the VM automatically 
activates the scheduler process and the scheduler process then decides 
whether to resume the previously running process or to switch to a 
different process.

In a way this folds the timer process into the scheduler (which makes 
good sense from my perspective because much of the work in the timer is 
stuff that could be more effectively take place in the scheduler). The 
implementation should be relatively straightforward - just add a 
scheduler process and a ready list to the special objects, and wherever 
the VM would normally process switch you just switch to the scheduler. 
Voila, there is your user-manipulable scheduler ;-) And obviously, 
anything that is run out of the scheduler process is by definition 
non-interruptable because there is simply nothing to switch to!

Cheers,
   - Andreas