[LWN Logo]
Date: Tue, 20 Mar 2001 12:05:46 -0800
To: Recipient List Suppressed:;
From: Bill Krauss <bkrauss@mediaone.net>
Subject: Realtime Linux Kernel Patch Available

For immediate release:

(March 20, 2001; Socorro NM) FSMLabs, creator and developer of 
RTLinux, has announced a kernel patch which will make RTLinux (and 
other realtime Linux variants) work reliably on the recent Linux 2.4 
kernels. According to Michael Barabanov, FSMLabs Principal Systems 
Engineer, a little-noticed change in Linux low-level memory 
management can produce increased timing uncertainties and 
unpredictable system errors in any Linux-based software that relies 
on the kernel mode memory properties found in previous versions of 
Linux. The change was intended to optimize average case performance 
of Linux in mainstream Linux applications, but introduces the 
possibility of memory faults into the operation of even the lowest 
level software. "For realtime developers using the newest and latest 
Linux editions, this change has caused mysterious and confusing 
failures," said Barabanov.

Thanks to an active and technically savvy user communty, the bug was 
uncovered rapidly. While fixing the problem for RTLinux customers is 
the top priority, FSMLabs has decided to make a general release of 
the patch available. Barabanov noted that this problem illustrates 
the complex interaction between the need to optimize Linux for 
desktop and server tasks and the sometimes conflicting requirements 
of realtime and embedded Linux users. Because Linux is open source, 
and because the design of RTLinux separates realtime software from 
the Linux kernel itself, robust engineering solutions to these 
problems can be found, and the advantages of using the Linux kernel 
far outweigh the costs of tracking kernel development.

RTLinux is a low-overhead hard realtime operating system which 
provides a flexible standards-based threading environment. RTLinux 
runs the Linux OS as a task that is never permitted to delay or 
interfere with the actions of timing-critical software. RTLinux 
worst-case interrupt latency is hardware dependent -- no more than 20 
microseconds on standard PC hardware and no more than 5 microseconds 
on some embedded boards. RTLinux provides full access to the Linux 
development environment and applications. This encourages a robust 
style of software design with a rapid, low cost development cycle, 
one which makes use of the enormous range of existing software 
available under Linux.

The patch for Linux 2.4.2 is available for free download at 

About FSMLabs

FSMLabs was founded by the creators of RTLinux to develop industrial 
strength realtime software and provide engineering services and 
support. The name, an abbreviation of Finite State Machine Labs, 
reflects a company objective to provide solutions that are 
characterized by simplicity, reliability and precise design.

For more information, visit www.rtlinux.com.

Phone/Fax: 505-835-2215


Bill Krauss            mailto:krauss@fsmlabs.com
FSMLabs: The RTLinux Company.
www.fsmlabs.com  www.rtlinux.com