qBeta for Arm – RaspberryPi

This page is for adding documentation for the implementation of qBeta on a bare bone Arm-based Rasberry Pie.

Attaching an object to a core

A class defining objects that may be attached to a core is a subclass of SuperCore

SuperCore:
   %core 16
   main: ref SuperScheduler
   inner(SuperCore)

The class Core is defined in BasicSystemLib.qbeta:

Core: SuperCore
      %Public
      attach: 
         in M: ref Scheduler
         main := M
      %Private
      go: do
          loop: obj 
             if (main =/= none) :then 
                 main.call 
             :else 
                 sleep(100)
                 restart(loop)
      (this(Core)).suspend

In the above code, class Scheduler is a subclass of class SuperScheduler – we plan to describe these classes elsewhere.

A Scheduler may be attached to a core in the following way:

C: obj Core         -- C is an instance of class Core
fork(C)             -- C is attached to a physical core 
C.attach(Scheduler) -- a Scheduler object is generated and
                    -- attached to C

In the current library, the objects that can be attached to a core are instances of class Scheduler. This is a property of how BasicSystemLib is defined. In principle qBeta allows any object to be attached to a core.

The byte code fork implements the actual attachment of C to a physical core.

Fork calls the following run-time routine:

Bfork(interpreter,B,threadNo + 1);

where interpreter is the function implementing the VM, and B is a stuct defining various attributes.

Bfork is defined in the file slib.S.