You are required to read and agree to the below before accessing a full-text version of an article in the IDE article repository.

The full-text document you are about to access is subject to national and international copyright laws. In most cases (but not necessarily all) the consequence is that personal use is allowed given that the copyright owner is duly acknowledged and respected. All other use (typically) require an explicit permission (often in writing) by the copyright owner.

For the reports in this repository we specifically note that

  • the use of articles under IEEE copyright is governed by the IEEE copyright policy (available at http://www.ieee.org/web/publications/rights/copyrightpolicy.html)
  • the use of articles under ACM copyright is governed by the ACM copyright policy (available at http://www.acm.org/pubs/copyright_policy/)
    ss
  • technical reports and other articles issued by Mälardalen University is free for personal use. For other use, the explicit consent of the authors is required
  • in other cases, please contact the copyright owner for detailed information

By accepting I agree to acknowledge and respect the rights of the copyright owner of the document I am about to access.

If you are in doubt, feel free to contact webmaster@ide.mdh.se

Lic presentation: On the Development of Hierarchical Real-Time Systems

Speakers:

Mikael Åsberg , Mikael Åsberg

Type:

Seminar

Start time:

2012-06-12 10:15

End time:

2012-06-12 12:15

Location:

Kappa

Contact person:



Description

Hierarchical scheduling (also referred to as resource reservation) is a hot topic within the research of real-time systems. It has many advantages including that it can facilitate software integration, fault isolation, structured analysis, legacy system integration etc. The main idea is to partition resources (processors, memory, etc.) into well defined slots. This technique is rarely used in the most common real-time applications; however, it is used in the avionics industry to isolate error propagation between system parts, and to facilitate analysis of the system.

Much of the research within resource reservation deals with theoretical schedulability analysis of partitioned systems, including shared resources (other than the processor). We will in this thesis address more practical issues related to resource reservation. We focus on implementation and prototyping aspects, as well as verification and instrumentation. One of our assumptions is that we deal only with fixed-priority pre-emptive scheduling (FPPS).

The first part in this thesis deals with individual software systems that may have its own tasks as well as a scheduler and it is assumed to be part of another larger system, hence, we refer to this individual system as a subsystem. The subsystem is assumed to be integrated together with other subsystems, but at an early stage, we make it possible to simulate the subsystem running together with the rest of the subsystems. This "simulation`` does not require the actual resource reservation mechanism, the only requirement is an operating system that supports FPPS. This pre-study may be a natural step towards the "real`` integration, since each individual subsystem can be test-executed within its assigned partition. All subsystems are assumed to run together using a resource reservation mechanism (during the actual integration). We have developed two prototypes of this mechanism. The first prototype is hand-crafted and it is equipped with a program tracer for partitioned based schedulers. This instrumentation is useful for debugging and visualization of program traces for this type of scheduling. The second prototype is developed using timed automata with tasks (task automata). This model-based scheduler is verified for correctness and it is possible to automatically generate source code for the scheduler. We have successfully synthesized this scheduler for the real-time operating system VxWorks. However, it can easily be extended for other platforms. Both prototypes have pros and cons. The first version has good performance while the second can guarantee its correctness; hence, there is a trade-off between performance and correctness.

Mikael Åsberg,

Email: mikael.asberg@mdh.se