An
introduction to RTLinux
© (1999)VJY Associates L.L.C. . All rights reserved.
Linux is a trademark of Linus Torvalds.
|
RTlinux is a version of the Linux Operating System, enhanced
to support hard realtime control programs.
RTLinux supports
realtime interrupt handlers and realtime periodic tasks with interrupt
latencies and scheduling jitter close to the hardware limits.
Unlike
general purpose operating systems, and unlike some operating systems
advertised as "real-time", execution of RTLinux realtime components
cannot be delayed by non-realtime components of the operating
system or by non-realtime processes.
Worst case interrupt latency
on a modest, reasonably configured x87 PC is under 15 microseconds from
the moment the hardware interrupt is asserted. Better hardware configurations
produce better timings. (This is worst case time, not typical
time, and the time is from the moment the hardware asserts, not from the
moment the operating system scheduler runs).
|
|
Realtime
tasks in RTLinux can communicate with Linux processes via shared memory
or a file-like interface so that a realtime application can make use of
all the powerful, non-realtime services of Linux, such as networking, graphics,
windowing systems, data analysis packages, Linux device drivers, and standard
POSIX API. For example, it is easy to write a Perl script that displays
data in Xwindows, responds to commands delivered over a network, and collects
data from a real-time task.
|
|
RTLinux
V1, is an exceptionally stable system in use in delivered products and
in laboratory environments. V1 RTLinux provides a simple API
for starting, stopping, and scheduling realtime tasks.
RTLinux V2, offers a simplified version of the POSIX pthreads API,
and RTLinux will be compliant with the POSIX "Minimal Realtime"
standard in which the realtime component is considered a single, multithreaded
POSIX process. The aim of the V2 kernel is to offer near POSIX with no
sacrifice of speed and simplicity, while proving hooks for add-ons for POSIX
full compatibility. V2 is released with a SMP capable x86 system
available by ftp. A
PowerPC port is in alpha test. Contact cort@fsmlabs.com if you are interested
in helping test this code.
|
|
RTLinux
was originally developed at the New Mexico Institute
of Technology and is now developed both on a commercial and on a research
basis. RTLinux is an open-source product with RTLinux specific components
released under the GPL and Linux components released under the standard
Linux license. The source is freely distributed. Both GPL and Non-GPL versions
of the RTL components are available from FSMLabs.
|
FSMLabs is the prime commercial developer of the RTLinux kernel, but
there are a growing number of vendors contributing to the kernel,
developing applications, and providing services.
(Except where noted
specifically there is no business relationship between the RTLinux developers
or FSMLabs and the listed companies.)
- FSMLabs LLC is
the commercial development company set up by the developers of
RTLinux. For information visit the
web site or mail
- SynergyMicro is
collaborating with FSMLabs to produce uniprocessor and SMP embedded
boards that run RTLinux on the PowerPC processor.
- LinuxCare is offering
enterprise support for corporate end-users and vendors of RTLinux and
embedded Linux in collaboration with FSMLabs Inc.
-
Zentropix
makes development tools, provides a RTLinux CD, and ports SGI and Solaris
applications to RTLinux.
-
FCsoftware
Inc. (Ontario, Canada) provides software services (QNX,RTLinux).
Email
webmaster@rtlinux.com if you want to be listed here. Listing does not imply
any endorsement or connection.
|
|
RTLinux is copyright
by the authors and VJY Associates LLC. It is released under the terms of
the GNU General Public Licence as published by the Free
Software Foundation except where specifically noted otherwise in the
code. There are no fees or royalties for use of the code for either commercial
or noncommercial use as long as license terms are followed. The code is
provided on an "as is" basis with no warranty of any kind. RTLinux depends
on the Linux code base developed by Linus Torvalds and others. Linux is
a trademark of Linus Torvalds. For information on Linux and its use as
a commercial product see Linux International
.
|