Multiprocessor Real-Time Locking Protocols

Brandenburg, Björn B.

doi:10.1007/978-981-4585-87-3_10-1

Cited by 9 publications

(6 citation statements)

References 136 publications

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“…Very similar to our proposed approach are the seminal multicore versions of the priority-ceiling protocol by Rajkumar et al, which exist in a shared-memory [10] and a messagepassing [11] version, also referred to as MPCP and DPCP, respectively [7]. MPCP tries to benefit from data locality by distinguishing between local resources only used on one core and global resources.…”

Section: Background and Related Workmentioning

confidence: 88%

“…Synchronizing concurring threads through means of shared memory or message passing is a long researched topic [6]. As the interaction of threads over shared resources greatly influences their timing behavior, synchronization mechanisms are also a highly researched topic in the real-time community (an overview can be found in [7]). In particular, shared resources can lead to priority inversion, meaning ready-to-run higher priority threads cannot execute because of blocked resources held by lower priority threads [8].…”

Section: Background and Related Workmentioning

confidence: 99%

“…However, if a sound worst-case blocking-bound analysis yields a finite duration, deadlocks are not possible. Solutions for lock nesting in real-time systems are either to forbid nesting entirely, to group locks that may nest to a single lock [7], or to analyze transitive blocking [18].…”

Section: G Lock Nestingmentioning

confidence: 99%

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Migration-Based Synchronization

Raffeck

Gerhorst

Schröder-Preikschat

et al. 2021

2021 XI Brazilian Symposium on Computing Systems Engineering (SBESC)

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A fundamental challenge in multi-and many-core systems is the correct execution of concurrent access to shared data. A common drawback from existing synchronization mechanisms is the loss of data locality as the shared data is transferred between the accessing cores. In real-time systems, this is especially important as knowledge about data access times is crucial to establish bounds on execution times and guarantee the meeting of deadlines.We propose in this paper a refinement of our previously sketched approach of Migration-Based Synchronization (MBS) as well as its first practical implementation. The core concept of MBS is the replacement of data migration with controlflow migration to achieve synchronized memory accesses with guaranteed data locality. This leads to both shorter and more predictable execution times for critical sections. As MBS can be used as a substitute for classical locks, it can be employed in legacy applications without code alterations.We further examine how the gained data locality improves the results of worst-case timing analyses and results in tighter bounds on execution and response time. We reason about the similarity of MBS to existing synchronization approaches and how it enables us to reuse existing analysis techniques.Finally, we evaluate our prototype implementation, showing that MBS can exploit data locality with similar overheads as traditional locking mechanisms.

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Section: Background and Related Workmentioning

confidence: 88%

Section: Background and Related Workmentioning

confidence: 99%

See 1 more Smart Citation

Migration-Based Synchronization

Raffeck

Gerhorst

Schröder-Preikschat

et al. 2021

2021 XI Brazilian Symposium on Computing Systems Engineering (SBESC)

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“…Priority-and-budget inheritance protocols have been studied for a long time, mainly in the context of accessing lockprotected shared resources [35]. The seminal work on priority inheritance is due to Sha et al [36] in 1990.…”

Section: Related Workmentioning

confidence: 99%

On the QNX IPC: Assessing Predictability for Local and Distributed Real-Time Systems

Becker

Dasari

Casini

2023

2023 IEEE 29th Real-Time and Embedded Technology and Applications Symposium (RTAS)

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With the advent of massively distributed applications such as those required by the IoT-to-Edge-to-Cloud compute continuum (i.e., automotive, smart agriculture, smart manufacturing, and more), real-time communication mechanisms allowing physically distributed nodes to seamlessly communicate as if they were running on the same host acquired noteworthy importance. To this end, the synchronous inter-process communication (IPC) mechanism provided by the QNX operating system (OS) is a promising candidate, as it allows using the application programming interface for communicating both on a single-and multi-node setting. Furthermore, it provides priority and partition inheritance mechanisms to improve predictability when working with the Adaptive Partitioning Scheduler (APS), a reservationbased scheduler provided by the QNX OS. This paper explores the behavior of the QNX synchronous message-passing (SyncMP) IPC with an extensive set of experiments, using them to formalize its behavior and model it from a real-time perspective. Then, it provides a response-time analysis for client-server applications based on the QNX SyncMP building upon self-suspending task theory. Finally, we evaluate the analysis on an application based on the WATERS 2019 Challenge by Bosch.

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“…Typically, tasks in a real-time robotic application are dependent on each other, where the dependency stems from their need to perform computations and exchange data, and thus access the MEC’s resources concurrently. The way the exclusive access to resources is handled, i.e., the real-time locking protocol ( Brandenburg, 2020 ) (the algorithm used to lock and unlock the MEC’s resources 3 when accessed concurrently by real-time tasks), has a direct effect on schedulability and therefore real-time performance (more in Section 2 through Section 10 ). Mainstream robotic frameworks lack predictable (bounded blocking) and efficient (low-overhead) locking protocols ( Section 2 , Section 10 ).…”

Section: Introductionmentioning

confidence: 99%

Formal Verification of Real-Time Autonomous Robots: An Interdisciplinary Approach

Foughali

Zuepke

2022

Front. Robot. AI

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Due to the severe consequences of their possible failure, robotic systems must be rigorously verified as to guarantee that their behavior is correct and safe. Such verification, carried out on a model, needs to cover various behavioral properties (e.g., safety and liveness), but also, given the timing constraints of robotic missions, real-time properties (e.g., schedulability and bounded response). In addition, in order to obtain valid and useful verification results, the model must faithfully represent the underlying robotic system and should therefore take into account all possible behaviors of the robotic software under the actual hardware and OS constraints (e.g., the scheduling policy and the number of cores). These requirements put the rigorous verification of robotic systems at the intersection of at least three communities: the robotic community, the formal methods community, and the real-time systems community. Verifying robotic systems is thus a complex, interdisciplinary task that involves a number of disciplines/techniques (e.g., model checking, schedulability analysis, component-based design) and faces a number of challenges (e.g., formalization, automation, scalability). For instance, the use of formal verification (formal methods community) is hindered by the state-space explosion problem, whereas schedulability analysis (real-time systems) is not suitable for behavioral properties. Moreover, current real-time implementations of robotic software are limited in terms of predictability and efficiency, leading to, e.g., unnecessary latencies. This is flagrant, in particular, at the level of locking protocols in robotic software. Such situation may benefit from major theoretical and practical findings of the real-time systems community. In this paper, we propose an interdisciplinary approach that, by joining forces of the different communities, provides a scalable and unified means to efficiently implement and rigorously verify real-time robots. First, we propose a scalable two-step verification solution that combines formal methods and schedulability analysis to verify both behavioral and real-time properties. Second, we devise a new multi-resource locking mechanism that is efficient, predictable, and suitable for real-time robots and show how it improves the latter’s real-time behavior. In both cases, we show, using a real drone example, how our approach compares favorably to that in the literature. This paper is a major extension of the RTCSA 2020 publication “A Two-Step Hybrid Approach for Verifying Real-Time Robotic Systems.”

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Multiprocessor Real-Time Locking Protocols

Cited by 9 publications

References 136 publications

Migration-Based Synchronization

Migration-Based Synchronization

On the QNX IPC: Assessing Predictability for Local and Distributed Real-Time Systems

Formal Verification of Real-Time Autonomous Robots: An Interdisciplinary Approach

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