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Verucchi, Micaela, (2021)  - Analisi esaustiva di DAG task: soluzioni per moderni sistemi real-time embedded  - , Tesi di dottorato - (, , Universitą degli studi di Modena e Reggio Emilia ) - pagg. -

Abstract: Modern cyber-physical embedded systems integrate several complex functionalities that are subject to tight timing constraints. Unfortunately, traditional sequential task models and uniprocessors solutions can not be applied in this context: a more expressive model becomes necessary. In this scenario, the Directed Acyclic Graph (DAG) is a suitable model to express the complexity and the parallelism of the tasks of these kinds of systems. In recent years, several methods with different settings have been proposed to solve the schedulability problem for applications featuring DAG tasks. However, there are still many open problems left. Besides schedulability, aspects like the freshness of data or reaction to an event are crucial for the performance of those kind of systems. For example, a typical application in the automotive field is composed of sensing the environment, planning, and actuate consequently to the elaborated data. Control end-to-end latency is then decisive, and it can get very complicated in real scenarios. This thesis represents an effort in both directions: (i) the schedulability of a DAG task on a multiprocessor, and (ii) the supervision of end-to-end latency for multi-rate tasks. For the former problem, a survey of the state-of-the-art of the Directed Acyclic Graph task model is presented, with a focus on scheduling tests that are more effective, easy to implement, and adopt. Regarding the latter, a method is proposed to convert a multi-rate DAG task-set with timing constraints into a single-rate DAG that optimizes schedulability, age, and reaction latency.