The goal of Industry 4.0 is to be faster, more efficient and more customer-centric, by enhancing the automation and digitalisation of production systems. Frequently, the production in Industry 4.0 is categorised as safety-critical, for example, due to the interactions between autonomous machines and hazardous substances that can result in human injury or death, damage to machines, property or the environment. In order to demonstrate the acceptable safety of production operations, safety cases are constructed to provide comprehensive, logical and defensible justification of the safety of a production system for a given application in a predefined operating environment. However, the construction and maintenance of safety cases in alignment with Industry 4.0 are challenging tasks. For their construction, besides the modular, dynamic and reconfigurable nature of Industry 4.0, the architectural levels of the things, fog and cloud computing have to be considered. The safety cases constructed at system design and development phases might be invalidated during production operations, thus necessitating some means for dynamic safety assurance. Moreover, flexible manufacturing in Industry 4.0 also underlines the need for safety assurance in a dynamic manner during the operational phase. Currently published studies are not explicitly supporting the safety assurance of Industry 4.0, which is the focus of this paper with special emphasis on dynamic safety assurance. At first, the Hazard and Operability (HAZOP) and Fault Tree Analysis (FTA) techniques are used for the identification and mitigation/elimination of potential hazards. Next, based on the hazard analysis results, we derived the safety requirements and safety contracts. Subsequently, safety cases are constructed using the OpenCert platform and safety contracts are associated with them to enable necessary changes during runtime. Finally, we use a simulations based approach to identify and resolve the deviations between the system understanding reflected in the safety cases and the current system operation. The dynamic safety assurance is demonstrated using a use case scenario of materials transportation and data flow in the Industry 4.0 context.

When trying to track down bugs using cyclic debugging, the ability to correctly reproduce executions is imperative. In sequential, deterministic, non-real-time software, this reproducibility is inherent. However, when the execution is affected by preemptive interrupts, this will have severe effects on the ability to reproduce program behaviors deterministically, since a reproduction requires the interrupts to hit the program at the exact same instructions. In previous methods, this problem has been solved using different kinds of instruction counters, that induce large execution time perturbations, demand for specialized hardware, or provide inexact results. This makes them highly unfit for resource-constrained embedded real-time systems. In this paper, we propose an alternative method for pinpointing interrupts in embedded real-time systems using context checksums, which is not dependent on specific hardware features or special compilers - but which rather can be applied to any system. Although context checksums in some cases also prove inexact or ambiguous, we show that they serve as a practical method for pinpointing and reproducing interrupts in embedded real-time systems. Furthermore, our method performs perfectly well with standard development tools and operating systems, requires no additional hardware support and, according to preliminary results, consumes merely a tenth of the execution time of existing software-based methods for pinpointing interrupts.

In this paper we present a method for automatically, on demand, linking entire functions into statically linked running embedded multi-tasking real-time applications. The purpose is to facilitate dynamic instrumentation of deployed systems. The method makes it possible to dynamically instrument the target in run-time, without preparing the source code. Code segments that are modified are substituted on the function level by the introduction of a dynamic relink method. The actual modification of the execution binary is performed in a safe and controlled manner by a low interference task. An algorithm is introduced for reusing memory from obsolete functions.

In this paper, we present a method for patching embedded multitasking real-time systems applications during runtime, for instrumentation purposes. The method uses binary modification techniques and automates the entire patch process. The method makes it possible to insert and remove instrumentation code without preparing the original source code. The method makes it possible to invoke code patches during run-time, without having to rely on dynamic linking of object files, or predeployment prepared dormant code. The actual modification of the executing target binary is performed in a safe and controlled manner by a dedicated low interference mutation task

Repeatable executions are required in order to successfully debug a computer system. However, for real-time systems, interactions with the environment and race conditions in the execution of multitasking real-time systems software make reproducible behavior difficult to achieve. Earlier work on debugging of real-time software has established the use of a deterministic replay, a record/replay solution, as a viable approach to reproduce executions. When combining the deterministic replay approach with infinite loop recorders (similar to black-box recorders in airplanes) for post-mortem debugging, it is essential that the recordings are sufficiently long and detailed in order to be able to re-execute the system. Basis problems however, are how to find a well-defined starting point within the recording, and how to find a reachable state in the rebooted/restarted system to match that instance? Previous work has not presented solutions to these fundamental problems, in this paper we do. We also present some implementation details from an industrial case study.

Previous work has shown that a system-on-a-chip lock cache (SoCLC) reduces on-chip memory traffic, provides a fair and fast lock hand-off, simplifies software, increases the real-time predictability of the system and improves performance. In this research work, we extend the SoCLC mechanism with a priority inheritance support implemented in hardware. Priority inheritance provides a higher level of real-time guarantees for synchronizing application tasks. Experimental results indicate that our SoCLC hardware mechanism with priority inheritance achieves a 36% speedup in lock delay, 88% speedup in lock latency, and 15% speedup in the overall execution time when compared to its software counterpart. The cost in terms of additional hardware area for the SoCLC with priority inheritance is approximately 10000 NAND2 gates.

Cyclic debugging is one of the most important and most commonly used activities in program development. During cyclic debugging, a program is repeatedly re-executed to track down errors when a failure has been observed. This process necessitates reproducible program executions. Applying classical debugging techniques, such as using breakpoints or single stepping, in real-time systems changes the temporal behaviour and makes reproduction of the observed failure during debugging less likely, if not impossible. Consequently, these techniques are not directly applicable to the cyclic debugging of real-time systems. In this paper, we present a novel software-based approach for the cyclic debugging of distributed real-time systems. By the online recording of significant system events, and then deterministically replaying them off-line, we can inspect a real-time system in great detail, while still preserving its real-time behaviour.

Reproducible and deterministic testing of sequential programs can in most cases be achieved by controlling the sequence of inputs to the program. The behavior of a distributed real-time system, on the other hand not only depends on the inputs but also on the order and timing of the concurrent tasks that execute and communicate with each other and the environment. Hence, sequential test techniques are not directly applicable, since they disregard the significance of order and timing of the tasks. In this paper we present a method for identifying all possible orderings of task starts, preemptions and completions for tasks executing in a distributed real-time system. Together with an accompanying testing strategy, this method allows test methods for sequential programs to be applied, since each identified ordering can be regarded as a sequential program. In the presented analysis and testing strategy, we consider task sets with recurring release patterns, and take into account the effects of clock synchronization and variations in start and execution times of the involved tasks.