REAL-TIME OPERATING SYSTEMS AND STANDARDS - Hard Real-Time Computing Systems: Predictable Scheduling Algorithms and Applications - page 431

An application can be written across several CPUs by using signal IPC and link han-
dlers. One can mix any kernel type with any other; links are monitored for hardware
failures, and alternate routes are automatically attempted to be established upon a link
failure. Processes are notified upon link failure events.

Errors in system calls are not indicated by a traditional return code, but as a call to an
error handler. The error handlers exist on several levels: process, block, and system
level. If an error handler on one level cannot handle the error, it is propagated to the
next level, until it reaches the system level.

12.2.3 QNX NEUTRINO

QNX Neutrino [Hil92] is a real-time operating system used for mission-critical appli-
cations, from medical instruments and Internet routers to telematics devices, process
control applications, and air traffic control systems.

The QNX Neutrino microkernel implements only the most fundamental services in the
kernel, such as signals, timers, and scheduling. All other components U file systems,
drivers, protocol stacks, applications U run outside the kernel, in a memory-protected
user space. As a result, a faulty component can be automatically restarted without
affecting other components or the kernel.

Some of the real-time features include distributed priority inheritance to eliminate
priority inversion and nested interrupts to allow priority driven interrupt handling. All
components communicate via message passing, which forms a virtual "software bus"
that allows the user to dynamically plug in, or plug out, any component on the fly.
It provides support for transparent distributed processing using standard messages to
access hardware and software resources on remote nodes.

QNX complies with the POSIX 1003.1-2001 standard, providing realtime extensions
and threads. It includes a power management framework to enable control over the
power consumption of system components. This allows the application developer to
determine power management policies.

Finally, QNX Neutrino also provides advanced graphics features, using layering tech-
niques, to create visual applications for markets such as automotive, medical, indus-
trial automation and interactive gaming. A support for accelerated 3D graphics ren-
dering (based on the Mesa implementation of the OpenGL standard) allows for the
creation of sophisticated displays with little impact on CPU performance.