  There is increasing interest in using Linux in the real-time domain due to
the emergence of cloud and edge computing, the need to decrease costs, and the
growing number of complex functional and non-functional requirements of
real-time applications. Linux presents a valuable opportunity as it has rich
hardware support, an open-source development model, a well-established
programming environment, and avoids vendor lock-in. Although Linux was
initially developed as a general-purpose operating system, some real-time
capabilities have been added to the kernel over many years to increase its
predictability and reduce its scheduling latency. Unfortunately, Linux
currently has no support for time-triggered (TT) scheduling, which is widely
used in the safety-critical domain for its determinism, low run-time scheduling
latency, and strong isolation properties. We present an enhancement of the
Linux scheduler as a new low-overhead TT scheduling class to support offline
table-driven scheduling of tasks on multicore Linux nodes. Inspired by the Slot
shifting algorithm, we complement the new scheduling class with a low overhead
slot shifting manager running on a non-time-triggered core to provide
guaranteed execution time to real-time aperiodic tasks by using the slack of
the time-triggered tasks and avoiding high-overhead table regeneration for
adding new periodic tasks. Furthermore, we evaluate our implementation on
server-grade hardware with Intel Xeon Scalable Processor.
