A common problem in event-triggered real-time systems is caused by low-priority tasks that are implemented as interrupt handlers interrupting and disturbing high-priority tasks that are implemented as threads. This problem is termed rate-monotonic priority inversion, and current software-based solutions are restricted in terms of more sophisticated scheduler features as demanded for instance by the AUTOSAR embedded-operating-system specification.We propose a hardware-based approach that makes use of a coprocessor to eliminate the potential priority inversion. By evaluating a prototypical implementation, we show that our approach both overcomes the restrictions of software approaches and introduces only a slight processing overhead in exchange for increased predictability.

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In the X10 language, computations are modeled as lightweight threads called activities. Since most operating systems only offer relatively heavyweight kernel-level threads, the X10 runtime system implements a user-space scheduler to map activities to operating-system threads in a many-to-one fashion. This approach can lead to suboptimal scheduling decisions or synchronization overhead. In this paper, we present an alternative X10 runtime system that targets OctoPOS, an operating system designed from the ground up for highly parallel workloads on PGAS architectures. OctoPOS offers an unconventional execution model based on i-lets, lightweight self-contained units of computation with (mostly) runto-completion semantics that can be dispatched very efficiently. We are able to do a 1-to-1 mapping of X10 activities to i-lets, which results in a slim runtime system, avoiding the need for user-level scheduling and its costs. We perform microbenchmarks on a prototype many-core hardware architecture and show that our system needs fewer than 2000 clock cycles to spawn local and remote activities.