Elements of Robust Real-Time Systems: Regularity-Based Virtualization and Functional Reactive Programming

Mar 01, 2023

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Abstract

The use of sophisticated digital systems to control complex physical components in real-time has grown at a rapid pace. These applications range from traditional stand-alone systems to highly-networked cyber-physical systems (CPS), spanning a diverse array of software architectures and control models. Examples include city-wide traffic control, robotics, medical systems, autonomous vehicular travel, green buildings, physical manipulation of nano-structures, and space exploration. Since all these applications interact directly with the physical world and often have humans in the loop, we must ensure their robustness, security, and physical safety. Obviously, the correctness of these real-time systems and CPS depends not only on the effects or results they produce, but also on the time at which these results are produced. For instance, in a CPS consisting of a multitude of vehicles and communication components with the goal to avoid collisions and reduce traffic congestions, formal safety verification and response time analysis are essential to the certification and use of such systems. This seminar introduces two key elements for building robust real-time systems: regularity-based virtualization and functional reactive programming.

Real-time resource partitioning (RP) divides hardware resources (processors, cores, and other components) into temporal partitions and allocates these partitions as virtual resources (physical resources at a fraction of their service rates) to application tasks. RP can be a layer in the OS or firmware directly interfacing the hardware, and is a key enabling technology for virtualization and cloud computing. Open, virtualized real-time systems make it easy to securely add and remove software applications as well as to increase resource utilization and reduce implementation cost when compared to systems which physically assign distinct computing resources to run different applications. The first part of this talk will describe ways based on the Regularity-based Resource Partition Model (RRP) to maintain the schedulability of real-time tasks as if they were scheduled on dedicated physical resources and increase the utilization of the physical multi-resources.

The benefits of using the functional (reactive) programming (FRP) over the imperative programming style found in languages such as C/C++ and Java for implementing embedded and real-time software are several. The functional programming paradigm allows the programmer to intuitively describe safety-critical behaviors of the system and connect its components, thus lowering the chance of introducing bugs in the design phase, resulting in a robust and secure implementation. Its stateless nature of execution does not require the use of synchronization primitives like mutexes and semaphores, thus reducing the complexity in programming on parallel and multi-core platforms. Hence, FRP can potentially transform the way we implement next-generation real-time systems and CPS. However, accurate response time analysis of FRP-based controllers remains a largely unexplored problem. The second part of this talk will explore a framework for accurate response time analysis, scheduling, and verification of embedded controllers implemented in FRP.