Formal Modeling and Verification of Embedded Real-Time Systems: An Approach and Practical Tool Based on Constraint Time Petri Nets

Nigro, Libero; Cicirelli, Franco

doi:10.3390/math12060812

Cited by 4 publications

(2 citation statements)

References 32 publications

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“…If the receiver is ready, the command is not executed until the clock value is less than 2. If the receiver is ready and x >= 2, the command can be taken but not necessarily soon, similar to transitions in classical Petri nets [20,21]. Locations L1 and L2 in Figure 1 are normal locations.…”

Section: Modeling Languagementioning

confidence: 97%

Modeling and Analysis of Dekker-Based Mutual Exclusion Algorithms

Nigro,

Cicirelli,

Pupo

2024

Computers

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Mutual exclusion is a fundamental problem in concurrent/parallel/distributed systems. The first pure-software solution to this problem for two processes, which is not based on hardware instructions like test-and-set, was proposed in 1965 by Th.J. Dekker and communicated by E.W. Dijkstra. The correctness of this algorithm has generally been studied under the strong memory model, where the read and write operations on a memory cell are atomic or indivisible. In recent years, some variants of the algorithm have been proposed to make it RW-safe when using the weak memory model, which makes it possible, e.g., for multiple read operations to occur simultaneously to a write operation on the same variable, with the read operations returning (flickering) a non-deterministic value. This paper proposes a novel approach to formal modeling and reasoning on a mutual exclusion algorithm using Timed Automata and the Uppaal tool, and it applies this approach through exhaustive model checking to conduct a thorough analysis of the Dekker’s algorithm and some of its variants proposed in the literature. This paper aims to demonstrate that model checking, although necessarily limited in the scalability of the number N of the processes due to the state explosions problem, is effective yet powerful for reasoning on concurrency and process action interleaving, and it can provide significant results about the correctness and robustness of the basic version and variants of the Dekker’s algorithm under both the strong and weak memory models. In addition, the properties of these algorithms are also carefully studied in the context of a tournament-based binary tree for N≥2 processes.

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Section: Modeling Languagementioning

confidence: 97%

Modeling and Analysis of Dekker-Based Mutual Exclusion Algorithms

Nigro,

Cicirelli,

Pupo

2024

Computers

Self Cite

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“…Mutual exclusion (ME) [1,2] is a fundamental problem in the concurrent, distributed, real-time programming domains [3][4][5][6][7]. It can stated as follows.…”

Section: Introductionmentioning

confidence: 99%

Correctness Verification of Mutual Exclusion Algorithms by Model Checking

Nigro,

Cicirelli

2024

Preprint

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Mutual exclusion algorithms are at the heart of concurrent, distributed/parallel, real-time and operating systems. It is well-known that such algorithms are very difficult to analyze and in the literature different conjectures about starvation-freedom and the number of by-passes (also said the overtaking factor), which in turn affects the (hopefully) bounded waiting time that a process competing for entering the critical section has to suffer before accessing the shared resource, have been formulated for specific algorithms. This paper proposes a novel modelling approach based on Timed Automata and the Uppaal toolset, which proves effective for studying all the properties of a mutual exclusion algorithm for N≥2 processes, by exhaustive model checking. Although the approach, as already confirmed by similar experiments reported in the literature, is not scalable due to state explosion problems, and can be practically applied until N≤5, it is of great value for revealing true properties of analyzed algorithms. For dimensions N>5 the statistical model checker of Uppaal can be used which, although based on simulations, can confirm properties by estimations and probabilities. The paper describes the proposed modelling and verification method and applies it to several mutual exclusion algorithms, thus retrieving known properties but also showing new results about properties often studied only by peer-review and intuitive reasoning.

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Formal Modeling and Verification of Lycklama and Hadzilacos’s Mutual Exclusion Algorithm

Nigro

2024

Mathematics

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This study describes our thorough experience of formal modeling and exhaustive verification of concurrent systems, particularly mutual exclusion algorithms. The experience focuses on Lycklama and Hadzilacos’s (LH) mutual exclusion algorithm. LH rests on the reduced size of the shared state, contains a mechanism that tries to enforce an FCFS order to processes entering their critical section, and embodies Burns and Lamport’s (BL) mutual exclusion algorithm. The modeling methodology is based on timed automata and the model checker of the popular Uppaal toolbox. The effectiveness of the modeling and analysis approach is first demonstrated by studying the BL’s solution and retrieving all its properties, including, in general, its unbounded overtaking, which is the non-limited number of by-passes a process can suffer before accessing its critical section. Then, the LH algorithm is investigated in depth by showing it fulfills all the mutual exclusion properties when it operates with atomic memory. However, as this study demonstrates, LH is not free of deadlocks when used with non-atomic memory. Finally, a state-of-the-art mutual exclusion solution is proposed, which relies on a stripped-down LH version for processes, which is used as the arbitration unit in a tournament tree (TT) organization. This study documents that LH’s TT-based algorithm satisfies all the mutual exclusion properties, with a linear overtaking, both using atomic and non-atomic memory.

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Formal Modeling and Verification of Embedded Real-Time Systems: An Approach and Practical Tool Based on Constraint Time Petri Nets

Cited by 4 publications

References 32 publications

Modeling and Analysis of Dekker-Based Mutual Exclusion Algorithms

Modeling and Analysis of Dekker-Based Mutual Exclusion Algorithms

Correctness Verification of Mutual Exclusion Algorithms by Model Checking

Formal Modeling and Verification of Lycklama and Hadzilacos’s Mutual Exclusion Algorithm

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