Mixed-criticality Systems Research Articles

Towards spatial isolation design in a multi-core real-time kernel targeting safety-critical applications

In mixed-criticality systems, applications naturally have different safety criticality levels. Partitioning technology is usually used to enable the integration of such mixed criticality applications upon one platform, aiming at reducing hardware, power consumption and especially certification cost. Partitioning can prevent fault propagation among mixed-criticality applications, if spatial and temporal isolation are adequately ensured. This paper focuses on the solution of spatial isolation in the HARTEX kernel on a multi-core platform in terms of memory, communication between applications and I/O sharing. According to formulated isolation requirements, a simple partitioning multi-core hardware architecture is proposed using SoC and memory protection units, and the kernel is extended to support spatial isolation between the kernel and applications as well as between applications. Combined design of hardware and software can easily achieve this isolation. At last, the spatial isolation is evaluated using a statistical sampling method and its performance is tested in terms of task switch, system call and footprint.

Schedule Design to Guarantee Freedom of Interference in Mixed Criticality Systems

Schedule Design to Guarantee Freedom of Interference in Mixed Criticality Systems

Crossover in growth laws for phase-separating binary fluids: Molecular dynamics simulations

Pattern and dynamics during phase separation in a symmetrical binary (A+B) Lennard-Jones fluid are studied via molecular dynamics simulations after quenching homogeneously mixed critical (50:50) systems to temperatures below the critical one. The morphology of the domains, rich in A or B particles, is observed to be bicontinuous. The early-time growth of the average domain size is found to be consistent with the Lifshitz-Slyozov law for diffusive domain coarsening. After a characteristic time, dependent on the temperature, we find a clear crossover to an extended viscous hydrodynamic regime where the domains grow linearly with time. Pattern formation in the present system is compared with that in solid binary mixtures, as a function of temperature. Important results for the finite-size and temperature effects on the small-wave-vector behavior of the scattering function are also presented.

Scheduling Real-Time Mixed-Criticality Jobs

Many safety-critical embedded systems are subject to certification requirements; some systems may be required to meet multiple sets of certification requirements, from different certification authorities. Certification requirements in such "mixed-criticality” systems give rise to interesting scheduling problems, that cannot be satisfactorily addressed using techniques from conventional scheduling theory. In this paper, we study a formal model for representing such mixed-criticality workloads. We demonstrate first the intractability of determining whether a system specified in this model can be scheduled to meet all its certification requirements, even for systems subject to merely two sets of certification requirements. Then we quantify, via the metric of processor speedup factor, the effectiveness of two techniques, reservation-based scheduling and priority-based scheduling, that are widely used in scheduling such mixed-criticality systems, showing that the latter of the two is superior to the former. We also show that the speedup factors we obtain are tight for these two techniques.

Mastering MPSoCs for Mixed-critical Applications

Multi-Processor Systems-on-Chips (MPSoCs) emerge as the predominant platform in embedded real-time applications. A large variety of ubiquitous services should be implemented by embedded systems in a cost- and power-efficient way, yet providing a maximum degree of performance, usability and dependability. By using a scalable Network-on-Chip (NoC) architecture which replaces the traditional point-to-point and bus connections in conjunction with performant IP cores it is possible to use the available performance to consolidate functionality on a single MPSoC platform. But especially when uncritical best-effort applications (e.g., entertainment) and critical applications (e.g., pedestrian detection, electronic stability control) are combined on the same architecture (mixed-criticality), validation faces new challenges. Due to complex resource sharing in MPSoCs the timing behavior becomes more complex and requires new analysis methods. Additionally, applications that may exhibit multiple behaviors corresponding to different operating modes (e.g., initialization mode, fault-recovery mode) need to be also considered in the design of mixed-critical MPSoCs. In this paper, challenges in the design of mixed-critical systems are discussed and formal analysis solutions which consider shared resources, NoC communication, multi-mode applications and their reliabilities are proposed.

Fault and Error Containment of Gateways in Distributed Real-Time Systems

The composition of large embedded computer systems out of heterogenous clusters requires gateways that resolve property mismatches between networks with different communication protocols and diverse computational models. At the same time, fault and error containment mechanisms are needed in order to prevent common mode failures that could be induced by the propagation of faults between clusters. This paper presents gateways to systematically tackle these challenges. The introduced gateways contain structured collections of time-sensitive variables associated with timing information (called a realtime database). The real-time database facilitates fault and error containment by temporally decoupling clusters. For accessing the real-time database from attached networks, we introduce network adaptors that ensure compliance with temporal specifications expressed using state machines with timing constraints. The containment of faults within clusters is of particular importance for mixed-criticality systems and increases the robustness of the overall systems. The proposed solution is experimentally evaluated in an example system with a time-triggered Ethernet network and a Controller Area Network (CAN).