- An Experiment in Wait-Free Synchronisation of Priority-Controlled Simultaneous Processes: Guarded Sections (2015)
- Wait-free synchronisation gives any process in the system strong progress guarantees, irrespective of number and behaviour of other processes simultaneously competing for shared resources (i.e., data structures and code sections). It ensures completion of any operation in a finite number of steps and, thus, provides the basis to derive bounded above or even constant executions times for non-sequential programs. This characteristic is of special meaning for time-dependent processes typical for real-time (embedded) systems. But wait-free synchronisation against the background of especially arbitrary data and code structures is no bed of roses. This paper is about organising non-sequential programs to the benefit of wait-free synchronisation. Conventional critical sections are designed as so called guarded sections. Unlike critical sections, preferential processes never block at entrance to a guarded section though only one process at a time is allowed to pass through. Competing processes are forced into bypass but, if necessary and by using futures, they can synchronise on concurrent state changes inside the respective section. In consequence of this measure, the execution model of guarded sections constrains the overlapping pattern of interacting (simultaneous) processes. Thereby, efficient wait-free synchronisation of the "guarding operations" is a gratifying by-product. First experiments on a 80-way multi-core system show that non-blocking wait-free synchronised guarded sections outperform lock-based protection schemes such as MCS-locks.
- A Flexible, Adaptive System for Data-Stream Processing in Energy-Constrained Ad-hoc Networks (2015)
- Today's generation of sensor networks reflect several changes in system characteristics over traditional sensor networks. These changes affect three key aspects: energy as a fundamental resource, stream data processing, and the inherently dynamic structure of the overall system. In this paper we extract and present eight distinct challenges aligned to the key aspects which need to be addressed in the future. We use data of ongoing science and research projects to extract the most important challenges. These challenges need to be tackled in order to provide the basis for a flexible and adaptive system design which supports data-stream processing in energy-constrained ad-hoc networks.