Xenomai brings POSIX and traditional RTOS APIs for porting
time-critical applications to Linux-based platforms. When the native
Linux kernel cannot meet the response time requirements of the
application, Xenomai supplements it with Cobalt, a small real-time
infrastructure which schedules time-critical activities independently
from the main kernel logic.
The Cobalt real-time core depends on a patch to the mainline Linux
kernel, which introduces a separate, high-priority execution stage for
running out-of-band interrupt handlers immediately upon IRQ receipt,
which cannot be delayed by the regular kernel work.