!standard  D.13.1(4/2)                             09-10-22    AI05-0171-1/01
!class Amendment 09-10-22
!status work item 09-10-22
!status received 09-10-22
!priority Medium
!difficulty Easy
!subject Ravenscar Profile for Multi-Processor Systems

!summary

The Ravenscar Profile, originally designed for single processors, has
proven remarkably useful for modelling verifiable real-time
single-processor systems. It can be extended to support
multi-processor systems using a fully partitioned approach. The
implementation of this scheme is simple, and it can be used to develop
applications amenable to schedulability analysis.

!problem

The Ravenscar Profile defines a deterministic and analysable tasking
model for single processors which can be supported with a run-time
system of reduced size and complexity. For multi-processor systems,
the Ravenscar Profile could be extended using a fully partitioned
approach, with each task allocated statically to a concrete processor.
This scheme could be supported by a streamlined run-time system, and
applications built following this approach can apply timing analysis
techniques on each processor separately.

!proposal

We propose to allow the implementation of the Ravenscar Profile on
multi-processor systems following a fully partitioned approach.

!wording

Clause D.13.1 should be modified to add the following implementation
advice.

Implementation advice

On a multi-processor system, an implementation should support a fully
partitioned approach, with each task allocated statically to a
concrete processor and no task migration. Each processor should have
separate and disjoint ready queues. A task should only be on the ready
queues of one processor, and the processor to which a task belongs
should be defined statically. Whenever a task running on a processor
reaches a task dispatching point, it goes back to the ready queues of
the same processor.

Protected objects should be the only task synchronization
mechanism. For inter-processor communication, an implementation should
provide the necessary locking mechanism to achieve the required mutual
exclusion among tasks executing on different processors.

!discussion

** TBD ** (Why is this model preferred??)

!example

** TBD **

--!corrigendum D.13.1(4/2)


!ACATS test

Add an ACATS C-Test of this package.


!appendix

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