Updated Dec. 11, 2004 — Vastly improved real-time capabilities in Linux kernel 2.6 are expected to hasten Linux's adoption in real-time computing. This Special Report tracks the adoption of the 2.6-series kernel, currently in beta testing, by embedded Linux distributors.

• MontaVista easies into Linux 2.6 waters — Sep. 15, 2004 — MontaVista has released what it calls an “early access” version of its commercial embedded Linux distribution based on the 2.6-series Linux kernel. The x86-only evaluation release will let existing MontaVista customers test applications on the new kernel, MontaVista says, and is available to current subscribers of MontaVista Linux Professional Edition. details.
• Migrating to Linux kernel 2.6 — Part 5: Migrating apps to the 2.6 kernel and NPTL — Mar. 11, 2004 — For most application developers, changes between the 2.4 and 2.6 kernel families have little direct impact. However, kernel and system changes that affect how applications spawn and manage other processes and threads are a significant exception to this rule. This whitepaper discusses topics related to migrating existing applications to the 2.6 kernel and the Native POSIX Threading Library (NPTL). Story
• Migrating to Linux kernel 2.6 — Part 4: Migrating custom Linux installations to 2.6 — Mar. 5, 2004 — This whitepaper provides an overview of the types of changes that you may need to make to a customized or specialized Linux installation in order to use it with the Linux 2.6 kernel, building upon the configuration file and administrative updates that were touched upon in the third article in this series. Story
• Migrating to Linux kernel 2.6 — Part 3: Using the 2.6 kernel with your current system — Feb. 24, 2004 — An overview of converting an existing development system to use a 2.6 kernel. Story
• Improvements in kernel development from 2.4 to 2.6 — Feb. 18, 2004 — This article looks at how the process of developing and testing the Linux kernel has changed since the 2.4 release, concluding that the new development process is actually the new kernel's most important “feature.” Story
• Migrating to Linux kernel 2.6 — Part 2: Migrating device drivers to Linux kernel 2.6 — Feb. 13, 2004 — This article discusses changes to the device driver model in the new kernel, and how to port or write new drivers for the 2.6 Linux kernel. Story
• Migrating to Linux kernel 2.6 — Part 1: Customizing a 2.6-based kernel — Feb. 6, 2004 — This article discusses the process of configuring the 2.6 kernel prior to compiling it. Story
• First 2.6-based “commercial” Linux ships — Jan. 20, 2004 — LynuxWorks ships BlueCat Linux 5.0, its first production release based on Linux kernel 2.6. LynuxWorks calls the release “the industry's first commercially available embedded Linux distribution based on Linux 2.6, and credits ISO testing and an extensive beta-testing program for enabling it to deliver a 2.6-based distribution so quickly. Story
• Kernel 2.6.0 takes wing: “Linux for everyone” — Dec. 18, 2003 — The Open Source Development Labs (OSDL), a global consortium of leading technology companies dedicated to accelerating the adoption of Linux, today announced that that Linus Torvalds and production kernel maintainer Andrew Morton have released the 2.6 Linux production kernel. Story
• Porting drivers to the 2.6 Linux kernel — Dec. 10, 2003 — LWN Executive Editor Jonathan Corbet, co-author of O'Reilly's Linux Device Drivers, has put together a series of detailed technical articles about porting device drivers to the new kernel. Story
• Torvalds: Last call for input on Linux kernel 2.6 — Oct. 27, 2003 — Yesterday's release of Linux kernel 2.6.0-test9 offers the “last big chance” for input on the next stable Linux kernel, according to Linux originator Linus Torvalds as quoted in a press release from the Open Source Development Labs (OSDL). This suggests that Torvalds will produce just one more test release — 2.6.0-test10 — which, if no show-stoppers emerge, he will likely rename as 2.6.0 and turn over to stable kernel maintainer Andrew Morton. Story
• MontaVista saves 2.6 for '04 — Oct. 3, 2003 — MontaVista Director of Strategic Marketing Bill Weinberg says his company will wait for a stable 2.6 kernel from Linus Torvalds before releasing its first 2.6-based distribution, but that MontaVista's current offerings include “the same thing” as parts of 2.6, according to an article in the SD Times. Story
• SnapGear embedded Linux distro boasts 2.6 kernel, merged uClinux — Sep. 29, 2003 — Version 3.0 of SnapGear Embedded Linux, based on Linux kernel 2.6, is now available for free download. The latest SnapGear security-oriented embedded Linux distribution is claimed to be the “world's first production Linux system powered by the 2.6 kernel” — but is also a watershed release in that for the first time, commercial developers can use a stable Linux kernel distribution, without patching, to build deeply embedded systems on devices without a memory management unit (MMU). uClinux patches were merged into the 2.5.46 release in November, 2002. Story
• LynuxWorks claims first public release of a 2.6-kernel based embedded Linux distribution — Sep. 8, 2003 — LynuxWorks announces a public beta for BlueCat 5.0, claiming to be the first embedded Linux distributor to release an OS based on the Linux 2.6-series kernel. Story
• Linux 2.6: A Breakthrough for Embedded Systems — Linux 2.6 introduces many new features that make it an excellent operating system for embedded computing. Among these new features are enhanced real-time performance, easier porting to new computers, support for large memory models, support for microcontrollers, and an improved I/O system. This whitepaper by LynuxWorks Director of Customer Education Brandon White describes the new functions and features of the latest Linux kernel of special interest to embedded system developers. Story
• 2.6 Linux kernel poised to “infiltrate” realtime computing — An article at EE Times notes that even prior to the appearance of 2.6-based embedded Linux distributions, Linux support began appearing for devices that have traditionally run proprietary commercial RTOSs — and for protocols important in the real-time computing space:
  • TimeSys offering a BSP for high-end Motorola VMEbus board
  • TimeSys offering a BSP for Kontron CompactPCI boards
  • FSMLabs' RTLinux supporting new high-speed network protocols

  As Linux gains real-time computing power, systems that traditionally ran a commercial RTOS for mission-critical tasks, and a Linux kernel for non-mission-critical tasks, have the potential for simplification to Linux-only systems, the article says. Story

• Linux 2.6 (or 3.0?) — a big step for enterprise and embedded — A technical article on IBM's DeveloperWorks site characterizes the pending new stable Linux kernel as “a big step for Linux on enterprise servers as well as for embedded systems,” and reviews some of the reasons. And yes, discussion suggests the new kernel could arrive with a major release number. Story
• Linux incremental patch mini-HOWTO — Those following the beta test releases of the 2.6-series Linux kernel can save lots of time and bandwidth by patching rather than replacing their kernel sources, and by re-using their kernel configuration with make oldconfig. Have a look at the recent post at kerneltrap.org on this topic, if you wish to try this simple procedure. Story
• Configuring and compiling the Linux kernel — Gentoo President/CEO Daniel Robbins offers this course with free registration through IBM's DeveloperWorks Web site. Robbins calls the course “ideal for those who want to learn about or improve their Linux kernel compilation and configuration skills,” and promises to cover important configuration options with in-depth focus on PCI and USB systems. A javascript-enabled browser is required. Story

The latest release in the 2.6 series is 2.6.0-test5, with an expected release date sometime this fall. The new kernel is pre-emptible, and features an improved scheduler for much better real-time responsiveness. As this article outlines, kernel pre-emption was originally introduced by MontaVista Software, then championed by Robert Love before being merged by Linus Torvalds.

Additional perspective on kernel pre-emption

• An interview with preemptible kernel patch maintainer, Robert Love
• Preemptible Linux — a reality check
• Design of a Fully Preemptible Linux Kernel
  
• MontaVista unveils fully preemptible Linux kernel prototype
  
• MontaVista unveils transparent real-time scheduler for Linux
  
• The Linux Real-Time Characterization Project
  
• Real-time Linux — what is it, why do you want it, how do you do it?
  
• Comparing real-time Linux alternatives
  
• Fundamentals of Real-time Linux Software Design
  
• ELJonline: Real Time and Linux, Part 1
  
• Improving Linux Response Time with a Resource Kernel
  
• TimeSys announces preemptive Linux kernel support
  
• The Real-time Linux Software Quick Reference Guide
  
• Which is it: -ible, or -able?

Additional perspective on the scheduler in Linux 2.5/2.6:

• Anticipatory scheduler ready for Linux kernel 2.5
• An interview with Linux kernel hacker, Ingo Molnar [kerneltrap.org]

 
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