Ravenscar Support for Time-Triggered Scheduling

[EN] This position paper follows from a previous proposal to integrate a time-triggered scheduler in a prioritybased, preemptive scheduler such as that supported by Ada¿s task dispatching policy FIFO Within Priorities . The resulting combined scheduling carries the advantages of both time-triggered and priority-based scheduling, and helps mitigating their drawbacks. The paper presents a system model for the time-triggered subsystem that extends the original proposal, and describes a Ravenscar implementation of the scheduler at the run-time system level, in the form of a new package Ada.Dispatching.TTS. Multiple programming patterns can be implemented on top of this scheduler. With respect to the previously proposed full-Ada implementation, only patterns that implied the use of asynchronous transfer of control have been excluded. On the other hand, the extension of the original model enables new patterns, not supported in our previous proposal, using the new types of continuation and optional slots. We hold that bringing the time-triggered paradigm to Ravenscar is both feasible and convenient for the High-Integrity and Embedded application domains.This work has been partly supported by the Spanish Government’s project M2C2 (TIN2014-56158-C4-1-P-AR) and the European Commission’s projects ENABLE-S3 and AQUAS (ECSEL-JU, Contracts 692455 and 737475)Real Sáez, JV.; Sáez Barona, S.; Crespo, A. (2018). Ravenscar Support for Time-Triggered Scheduling. ACM SIGAda Ada Letters. 38(1):41-54. https://doi.org/10.1145/3241950.3241957S4154381M. Aldea and M. González-Harbour. MaRTE OS: An Ada Kernel for Real-Time Embedded Applications. Reliable Software Technologies - Ada Europe 2001, Lecture Notes in Computer Science, 2043:305-316, 2001.ISO/IEC-JTC1-SC22-WG9. Ada Reference Manual ISO/IEC 8652:2012(E). URL: http://www.ada-europe.org/manuals/LRM-2012.pdf, 2012.J. Leung and J. Whitehead. On the complexity of xed-priority scheduling of periodic, real-time tasks. Performance Evaluation (Netherlands), 2(4):237-250, 1982.C. Liu and J. Layland. Scheduling Algorithms for Multiprogramming in a Hard Real-Time Environment. Journal of the ACM, 20(1):46-61, 1973.J. Real and P. Rogers. Session Summary: Experience. Ada Letters, 36(1):101-102, June 2016.J. Real, S. Sáez, and A. Crespo. Combined scheduling of time-triggeed plans and priority scheduled task sets. Ada Letters, 36(1):68-76, June 2016.J. Real, S. Sáez, and A. Crespo. Combining time-triggered plans with priority scheduled task sets. In M. Bertogna and L. M. Pinho, editors, Reliable Software Technologies - Ada-Europe 2016, volume 9695 of Lecture Notes in Computer Science. Springer, June 2016.S. Sáez and J. Real. TTS Ravenscar runtime. https://doi.org/10.5281/zenodo.1168723, February 2018

Steps to an advanced Ada programming environment

Conceptual simplicity, tight coupling of tools, and effective support of host-target software development will characterize advanced Ada programming support environments. Several important principles have been demonstrated in the Arcturus system, including template-assisted Ada editing, command completion using Ada as a command language, and combining the advantages of interpretation and compliation. Other principles, relating to analysis, testing, and debugging of concurrent Ada programs, have appeared in other contexts. This paper discusses several of these topics, considers how they can be integrated, and argues for their inclusion in an environment appropriate for software development in the late 1980's

The TASTE Toolset: turning human designed heterogeneous systems into computer built homogeneous software.

The TASTE tool-set results from spin-off studies of the ASSERT project, which started in 2004 with the objective to propose innovative and pragmatic solutions to develop real-time software. One of the primary targets was satellite flight software, but it appeared quickly that their characteristics were shared among various embedded systems. The solutions that we developed now comprise a process and several tools ; the development process is based on the idea that real-time, embedded systems are heterogeneous by nature and that a unique UML-like language was not helping neither their construction, nor their validation. Rather than inventing yet another "ultimate" language, TASTE makes the link between existing and mature technologies such as Simulink, SDL, ASN.1, C, Ada, and generates complete, homogeneous software-based systems that one can straightforwardly download and execute on a physical target. Our current prototype is moving toward a marketed product, and sequel studies are already in place to support, among others, FPGA systems

Safety verification of ADA programs in MURPHY

MURPHY is a experimental methodology, which will include an integrated tool set, for building safety-critical, real-time software. Although it is language independent, many safety-critical software projects are currently planning to use Ada. This paper presents the semantic templates for the verification of the safety of Ada programs using Software Fault Tree Analysis. An example is shown of applying the technique to an Ada program, and the tools in the MURPHY tool set to aid in this type of analysis are described

Building on the DEPLOY Legacy: Code Generation and Simulation

The RODIN, and DEPLOY projects laid solid foundations for further theoretical, and practical (methodological and tooling) advances with Event-B. Our current interest is the co-simulation of cyber-physical systems using Event-B. Using this approach we aim to simulate various features of the environment separately, in order to exercise deployable code. This paper has two contributions, the first is the extension of the code generation work of DEPLOY, where we add the ability to generate code from Event-B state-machine diagrams. The second describes how we may use code, generated from state-machines, to simulate the environment, and simulate concurrently executing state-machines, in a single task. We show how we can instrument the code to guide the simulation, by controlling the relative rate that non-deterministic transitions are traversed in the simulation.Comment: In Proceedings of DS-Event-B 2012: Workshop on the experience of and advances in developing dependable systems in Event-B, in conjunction with ICFEM 2012 - Kyoto, Japan, November 13, 201

A Monitoring Language for Run Time and Post-Mortem Behavior Analysis and Visualization

UFO is a new implementation of FORMAN, a declarative monitoring language, in which rules are compiled into execution monitors that run on a virtual machine supported by the Alamo monitor architecture.Comment: In M. Ronsse, K. De Bosschere (eds), proceedings of the Fifth International Workshop on Automated Debugging (AADEBUG 2003), September 2003, Ghent. cs.SE/030902

Building on the DEPLOY legacy: code generation and simulation

The RODIN, and DEPLOY projects have laid solid foundations for further theoretical, and practical (methodological and tooling) advances with Event-B; we investigated code generation for embedded, multi-tasking systems. This work describes activities from a follow-on project, ADVANCE; where our interest is co-simulation of cyber-physical systems. We are working to better understand the issues arising in a development when modelling with Event-B, and animating with ProB, in tandem with a multi-simulation strategy. With multi-simulation we aim to simulate various features of the environment separately, in order to exercise the deployable code. This paper has two contributions, the first is the extension of the code generation work of DEPLOY, where we add the ability to generate code from Event-B state-machine diagrams. The second describes how we may use code, generated from state-machines, to simulate the environment, and simulate concurrently executing state-machines, in a single task. We show how we can instrument the code to guide the simulation, by controlling the relative rate that non-deterministic transitions are traversed in the simulation

Analysis of a benchmark suite to evaluate mixed numeric and symbolic processing

The suite of programs that formed the benchmark for a proposed advanced computer is described and analyzed. The features of the processor and its operating system that are tested by the benchmark are discussed. The computer codes and the supporting data for the analysis are given as appendices

Modules program structures and the structuring of operating systems

In this paper some views are presented on the way in which complex systems, such as Operating Systems and the programs to be interfaced with them can be constructed, and how such systems may become heavily library oriented. Although such systems have a dynamic nature, all interfacing within and among modules can be checked statically. It will be shown that the concepts presented are equally valid for single user systems, multi-programming systems and even distributed systems. The ideas have been spurred by the implementation of a modular version of Pascal and a supporting Operating System, currently nearing completion at Twente University of Technology, The Netherlands