Fixed-priority scheduling with deferred preemption (FPDS) and fixed-priority scheduling with preemption thresholds (FPTS) have been proposed in the literature as viable alternatives to fixed-priority preemptive scheduling (FPPS), that reduce memory requirements, reduce the cost of arbitrary preemptions, and may improve the feasibility of a task set even when preemption overheads are neglected.This paper aims at advancing the relative strength of limitedpreemptive schedulers by combining FPDS and FPTS. In particular, we present a refinement of FPDS with preemption thresholds for both jobs and sub-jobs, termed FPGS. We provide an exact schedulability analysis for FPGS, and show how to maximize the feasibility of a set of sporadic tasks under FPGS for given priorities, computation times, periods, and deadlines of tasks. We evaluate the effectiveness of FPGS by comparing the feasibility of task sets under FPGS with other fixed-priority scheduling algorithms by means of a simulation. Our experiments show that FPGS allows an increase of the number of task sets that are schedulable under fixed-priority scheduling.

Understanding the wiring diagram of the human cerebral cortex is a fundamental challenge in neuroscience. Elemental aspects of its organization remain elusive. Here we examine which structural traits of cortical regions, particularly their cytoarchitecture and thickness, relate to the existence and strength of inter-regional connections. We use the architecture data from the classic work of von Economo and Koskinas and state-of-the-art diffusion-based connectivity data from the Human Connectome Project. Our results reveal a prominent role of the cytoarchitectonic similarity of supragranular layers for predicting the existence and strength of connections. In contrast, cortical thickness similarity was not related to the existence or strength of connections. These results are in line with findings for non-human mammalian cerebral cortices, suggesting overarching wiring principles of the mammalian cerebral cortex. The results invite hypotheses about evolutionary conserved neurobiological mechanisms that give rise to the relation of cytoarchitecture and connectivity in the human cerebral cortex.

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Citation for published version (APA):Heuvel, van den, M. M. H. P., Bril, R. J., & Lukkien, J. J. (2011). Dependable resource sharing for compositional real-time systems. In Proceedings of the 17th IEEE International Conference on Embedded and Real-time Computing Systems and Applications (RTCSA 2011, Toyama, Japan, August 28-31, 2011 Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publicationGeneral rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policyIf you believe that this document breaches copyright please contact us at: openaccess@tue.nl providing details and we will investigate your claim. AbstractHierarchical scheduling frameworks (HSFs) have been extensively investigated as a paradigm for facilitating temporal isolation between components that need to be integrated on a single shared processor. In the presence of shared resources, however, temporal isolation may break when one of the accessing components executes longer than specified during global resource access. The ability to confine such temporal faults makes the HSF more dependable. As a solution we propose a stack-resource-policy (SRP)-based synchronization protocol for HSFs, named Hierarchical Synchronization protocol with Temporal Protection (HSTP).When a component exceeds its specified critical-section length, HSTP enforces a component to self-donate its own budget to accelerate the resource release. In addition, a component that blocks on a locked resource may donate budget. The schedulability of those components that are independent of the locked resource is unaffected. HSTP efficiently limits the propagation of temporal faults to resource-sharing components by disabling local preemptions in a component durin...

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Abstract-Cache-related pre-emption delays (CRPD) have been integrated into the schedulability analysis of sporadic tasks with constrained deadlines for fixed-priority pre-emptive scheduling (FPPS). This paper generalizes that work by integrating CRPD into the schedulability analysis of tasks with arbitrary deadlines for fixed-priority pre-emption threshold scheduling (FPTS). The analysis is complemented by an optimal threshold assignment algorithm that minimizes CRPD. The paper includes a comparative evaluation of the schedulability ratios of FPPS and FPTS, for constrained-deadline tasks, taking CRPD into account. I. IntroductionFor cost-effectiveness reasons, it is preferred to use commercial off-the-shelf (COTS) programmable platforms for real-time embedded systems, rather than dedicated, application-domain specific platforms. These COTS platforms typically contain a cache to bridge the gap between the processor speed and main memory speed and to reduce the number of conflicts with other devices on the system bus. Unfortunately, caches give rise to additional delays upon pre-emptions due to cache flushes and reloads of blocks that are replaced during pre-emption. This cache-related pre-emption delay (CRPD) can have a significant impact on the computation times of tasks. For fixed-priority pre-emptive scheduling (FPPS), which is the defacto standard used in industry, CRPD has therefore been integrated into the schedulability analysis [17,26,32,28,3].Recently, limited pre-emptive scheduling schemes received a lot of attention from academia. In particular, fixed-priority scheduling with limited pre-emptions, such as fixed-priority scheduling with deferred pre-emption (FPDS) or co-operative scheduling [16,14,20] and fixed-priority scheduling with preemption thresholds (FPTS) [33,31,30,25], are considered viable alternatives between the extremes of FPPS and fixedpriority non-pre-emptive scheduling (FPNS). Compared to FPPS, limited pre-emptive schemes can (i) reduce memory requirements [31,23,21] and (ii) reduce the cost of arbitrary pre-emptions [16,14,10]. Compared to both FPPS and FPNS, these schemes may significantly improve the feasibility of a task set [14,31,8,20].Although FPDS clearly outperforms FPTS from a theoretical perspective [18], applying FPDS in practice is still a challenge because pre-emption points have to be explicitly added in the code. Assuming strictly periodic tasks with known phasing, a single non-pre-emptive region (NPR) can significantly reduce the preemptions that can feasibly occur [29]. Alternatively, sporadic tasks with floating NPRs [34,6] can be used; however, these require specific operating-system support and can lead

Hierarchical scheduling frameworks (HSFs) provide means for composing complex real-time systems from welldefined, independently analyzed subsystems. To support resource sharing within two-level HSFs, three synchronization protocols based on the stack resource policy (SRP) have recently been presented, i.e. HSRP [1], SIRAP [2] and BROE [3]. This paper describes the first implementation presenting these three SRPbased synchronization protocols side-by-side in a HSF-enabled real-time operating system. We base our implementations on the commercially available real-time operating system µC/OS-II, extended with proprietary support for periodic tasks, idling periodic servers and two-level preemptive scheduling. Moreover, we investigate the system overhead of the synchronization primitives of each protocol. Transparent interfaces allow a protocol to be selected during integration time based on its relative strengths 1 .