1. Aravind Venkataraman

2. Topics of Discussion Real-time Computing Synchronous Programming Languages Real-time Operating Systems Real-time System Types Real-time System Key factors, terminology Real-time System Methodologies Real-time Scheduling Algorithms Real-time Scheduling Implementation Issues Real-time Computing Research Key People

3. Real –time Computing [1] Software & hardware for systems which have real-time constraints and are interrupted often. Comprises of: Synchronous Programming Language. Real-time Operating System. Real-time Design Methodologies.

4. Synchronous Programming Language Provides abstract modules for scheduling algorithms, parallelism, pre-emption. Finite state (execution time predictable), deterministic, synchronous dataflow. Declarative and Imperative Languages. Examples: Lustre, Quartz, SOL, Esterel.

5. Examples: Embedded Systems (Appliance Controller, Spacecraft, Robots, Industrial Control. “Control Program” – American Airlines, IBM – Later called “Sabre Airline Reservation System”. Real-Time Operating System (RTOS) Early Real-time Systems Recent Important Real-time Systems DSOS (Deep Six OS) – Geophysical Services Division, Texas Instruments. Ptolemy Project, University of California, Berkeley [8]. MARS (MAintainable Real-time System). ARTS Kernel. Spring Kernel. CHAOS Kernel. Alpha Kernel. Dragon Kernel.

6. Real-time System Types ‘Hard’ Real-time System - Guaranteed, deterministic behaviour. - Critical Jobs. - Eg. Nuclear Power Plant controller. ‘Soft’ Real-time System - High Throughput. - Concurrent access, Large demand. - Eg. Airline Reservation System.

7. Hard deadline

8. Soft deadline

9. Minimal Interrupt Latency Minimal Thread switching Latency Real-Time System Key Factors [Burns, ‘91] Other Terminology Task Deadline Maximum Response Time Worst case Execution Time Timing Analysis Priority Inversion Priority Inheritance Priority Ceiling Protocol. Important Real-time System Property [Stankovic, ‘84] System Deadline => Process Deadline Periodic, Aperiodic Process.

10. MASCOT ( M odular Approach to Software Construction Operation and Test) - Architecture Oriented (RT Control & interface definition between concurrent processes) - British ground-air missile system. HOOD (Hierarchic Object-Oriented Design) - Hierarchical decomposition. - European Space Agency – Aerospace project. AADL (Architecture Analysis and Design Language) [6] - Automotive, aerospace industry. RTSJ (Real-Time Specification for Java) [7] Real-time System Design Methodologies

11. Real-time Scheduling Algorithms [Stankovic,’88] Classification Static vs Dynamic Preemptive vs Non-preemptive Global vs Local Examples Static: - Fixed-priority Rate-monotonic algorithm - Fixed-priority Deadline-monotonic algorithm - Graph based Approach Dynamic: - Earliest Deadline First - Least Laxity

12. Communication Delay - worst case execution time, non-deterministic RPC - Remote blocking Real-time Implementation issues in Distributed Systems [Kasavant, ‘88]

13. Key People in Real-time Computing Edward Lee - UC Berkeley, Ptolemy Project - http://ptolemy.eecs.berkeley.edu/~eal/ Alan Burns, Andy Wellings - Univ of York, RT Systems Research group - http://www.cs.york.ac.uk/rts/ David Dill - Stanford University - Formal verification in RT Systems design - http://verify.stanford.edu/dill/ Rajeev Alur - Univ of Pennsylvania - Hybrid systems, formal modeling, verification of reactive systems; Automata Theory - http://www.cis.upenn.edu/~alur/ Nicolas Halbwachs - Grenoble University, Critical embedded systems, data flow synchronous programming languages - http://www-verimag.imag.fr/~halbwach/

14. RT Research Groups RT computing lab: http://www.eecs.umich.edu/RTCL/ RT computation and communication group: http://www.cs.bu.edu/groups/realtime/ RT and embedded systems laboratory: http://www.cs.virginia.edu/~control/ Supercomputing and Parallel computing research group: http://www.cs.cmu.edu/~scandal/research-groups.html Systems Research group: http://www.cc.gatech.edu/systems/ Distributed systems research group: http://www-dsg.stanford.edu/ Institute for systems engineering, RT Systems group: http://www.rts.uni-hannover.de/index.php/Main_Page/index.htm Institute for computer engineering, RT Systems group: http://www.vmars.tuwien.ac.at/ IEEE Technical Committee on Real-Time Systems: http://cs-www.bu.edu/pub/ieee-rts/ Euromicro Technical Committee on Real-time Systems: http://www.ecrts.org RT Technical Commitees

15. RT Scientific conferences EventWebsite IEEE Real-time Technology and Applications Symposium, St. Louis, Missouri, USA - April 22-24, 2008 http://www.rtas.org/ ECRTS – Euromicro Conference on Real-time Systems http://www.ecrts.org/ IEEE Real-time Systems Symposium, Tuscon, Arizona, USA – Dec 3-6, 2007 http://www.rtss.org/ International Symposium on Object oriented Real-time Distributed systems http://ise.gmu.edu/is orco7 IEEE International Conference on Embedded and Real-time Computing systems and Applications http://ssl.snu.ac.kr/~ rtcsa2007/

16. References 1.http://en.wikipedia.org/wiki/Real-time_operating_system 2.S. Cheng, J.A. Stankovic and K. Ramamritham, ‘‘Scheduling Algorithms for Hard Real-Time Systems: A Brief Survey’’, pp. 150-173 in Hard Real-Time Systems: Tutorial, IEEE (1988). 3.T. L. Casavant and J. G. Kuhl, ‘‘A Taxonomy of Scheduling in General Purpose Distributed Computing Systems’’, IEEE Transactions on Software Engineering 14(2), pp. 141-154 (February 1988). 4.A. Burns, ‘‘Scheduling Hard Real-Time Systems: A Review’’, Software Engineering Journal 6(3), pp. 116-128 (1991). 5.K. Ramamritham and J.A. Stankovic, ‘‘Dynamic Task Scheduling in Hard Real- Time Distributed Systems’’, IEEE Software 1(3), pp. 65-75 (July 1984). 6.http://www.aadl.info/ 7.http://www.rtsj.org/ 8.http://ptolemy.eecs.berkeley.edu/