Xenomai
Background
Xenomai is a real-time operating system (RTOS) API designed to work alongside Linux. It provides a means of migrating from a proprietary RTOS to a Linux based system. This also allows for native Linux applications to be run side-by-side with real-time applications on the same target.
Xenomai provides a generic real-time core scheduler called the nucleus. Different RTOS APIs are provided via skins abstracting the nucleus.
Xenomai is designed to run on many different target architectures including x86, ARM, Blackfin and NIOS2.
General Information
As of Xenomai 3, there are two possible kernel configurations available: Cobalt and Mercury.
The Cobalt core configuration is the traditional co-kernel configuration and is the evolution of the Xenomai 2 architecture. The Linux kernel is patched to allow the Cobalt core to deal with real-time activities including interrupts and scheduling. The RTOS APIs provide an interface to the Cobalt core from user-space. The co-kernel configuration relies on the Adeos I-pipe patch for the sharing hardware resources between the kernels.
The Mercury core is a single kernel configuration that relies on the Linux kernel for the real-time capabilities. Typically this requires PREEMPT-RT support to be enabled in the kernel to meet timing requirements. The non-POSIX real-times APIs are emulated over a native threading library preferably NPTL. The Mercury configuration currently requires no Xenomai-specific kernel features but the kernel should provide CONFIG_HIGH_RES_TIMERS and PREEMPT-RT for bounded latencies.
