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<title>LITMUS RT 2007</title>
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<div class="logobox">
<img src="inc/litmusrt.png" alt="LITMUS^RT: Linux Testbed for Multiprocessor Scheduling in Real-Time Systems" />
<h1>LITMUS<sup>RT</sup> 2007 Series</h1>
</div>
<div class="alertbox">
<p class="nomargin">
<em><b>NOTE:</b> This web page discusses an older version of
LITMUS<sup>RT</sup>. Please use the
<a href="index.html">current version</a> unless you
have specific interest in the 2007 series.
</em>
</p>
</div>
<div class="nav">
<p>
<a href="#about">about</a> -
<a href="#support">support</a> -
<a href="#collaborators">collaborators</a> -
<a href="#download">download</a> -
<a href="#install">installation</a> -
<a href="#links">documentation</a>
</p>
</div>
<h2 id="about">About</h2>
<div class="box">
<p class="notopmargin">
The LITMUS<sup>RT</sup> project is a soft real-time extension of the Linux
kernel with focus on multiprocessor real-time scheduling and
synchronization. The LITMUS<sup>RT</sup> 2007 series is based on Linux 2.6.20.
The Linux kernel is modified to support the sporadic task
model and modular scheduler plugins. Both partitioned and global scheduling
is supported.
The last release of the 2007 series, LITMUS<sup>RT</sup> 2007.3, includes plugins for the following
scheduling policies:
</p>
<ul>
<li> Partitioned EDF (P-EDF)</li>
<li> Partitioned EDF with synchronization support (PSN-EDF)</li>
<li> Global EDF (G-EDF)</li>
<li> Global EDF with synchronization support (GSN-EDF)</li>
<li> Global non-preemptive EDF (G-NP-EDF)</li>
<li> Global Feedback-Controlled EDF (FC-EDF)</li>
<li> EDF for heterogeneous task systems (EDF-HSB)</li>
<li> PFAIR (both staggered and aligned quanta are supported)</li>
</ul>
<p>
The last 2007.X release of LITMUS<sup>RT</sup> occurred on 01/28/2008.
</p>
</div>
<h2 id="support">Support</h2>
<div class="box">
<p class="nomargin">
The LITMUS<sup>RT</sup> 2007 development effort was supported by grants from
Intel Corp., IBM Corp., The National Science Foundation (grant CCR 0615197), and The U.S.
Army Research Office (grant W911NF-06-1-0425).
</p>
</div>
<h2 id="collaborators">Collaborators</h2>
<div class="box">
<p class="nomargin"> The LITMUS<sup>RT</sup> project is led by <a
href="http://www.cs.unc.edu/~anderson/">Dr. James H. Anderson</a>. <br/><br/>
LITMUS<sup>RT</sup> 2007 was implemented by students of the
<a href="http://www.cs.unc.edu/rt">Real-Time Systems
Group</a> at the <a href="http://www.unc.edu">University of North Carolina
at Chapel Hill</a>:
</p>
<ul>
<li> <a href="http://www.cs.unc.edu/~block/">Aaron D. Block</a> <em>(graduated
August 2008)</em>
</li>
<li> <a href="http://www.cs.unc.edu/~bbb/">Björn B. Brandenburg</a>
</li>
<li> <a href="http://www.cs.unc.edu/~jmc/">John M. Calandrino</a> <em>(graduated
July 2009)</em>
</li>
<li> <a href="http://www.cs.unc.edu/~uma/">UmaMaheswari Devi</a> <em>(graduated
December 2006)</em>
</li>
<li> <a href="http://www.cs.unc.edu/~leontyev/">Hennadiy Leontyev</a>
</li>
</ul>
</div>
<h2 id="download">Download</h2>
<div class="box">
<p class="notopmargin">
The source code of LITMUS<sup>RT</sup> is made available as open source
under the terms of the <a href="http://www.gnu.org/licenses/gpl.txt">GNU
General Public License (GPL)</a>.
</p>
<p>
The third and last version of the LITMUS<sup>RT</sup> 2007 series was released on 01/28/2008.
It consists of our Linux kernel modifications in the form of a patch against Linux 2.6.20,
<span class="src">liblitmus</span>, the user-space API for real-time tasks,
and <span class="src">libso</span>, a library for shared objects that
provides synchronization primitives suitable for real-time tasks.
</p>
<ul>
<li>
2007.3 (January 2008)<br/>
Based on Linux 2.6.20. (see <a href="#install">Section Install</a>
below) <br/>
Files:
<ul>
<li><a href="download/2007.3/litmus-rt-2007.3.patch">litmus-rt-2007.3.patch</a> (344 KB)</li>
<li><a href="download/2007.3/liblitmus-2007.3.tgz">liblitmus-2007.3.tgz</a>
(14 KB)</li>
<li><a href="download/2007.3/libso-2007.3.tgz">libso-2007.3.tgz</a>
(15 KB)</li>
<li><a href="download/2007.3/SHA256SUMS">SHA256 check sums.</a>
</li>
</ul>
</li>
<li>
Major changes:
<ul>
<li>
Support for multi-threaded real-time applications added. The
use of <span class="src">libso</span> is no longer required.
</li>
<li>
All allocations (semaphores, etc.) are now dynamic. No more
running out of resources.
</li>
<li>
Real-Time tasks do not have be launched with
<span class="src">rt_launch</span> anymore. Instead, a new
<span class="src">task_mode()</span> API was introduced that
allows (Linux) tasks to transition in and out of
background task mode (std. Linux task) and LITMUS<sup>RT</sup>
real-time task.
</li>
<li>
Many bug fixes.
</li>
</ul>
</li>
</ul>
<p class="nobottommargin">
Please note that theses implementations are <em>prototypes</em> with
certain limitations. Most notably, it is not secure in a multiuser context,
<em>i.e.</em>, real-time system calls do not require superuser
privileges. Further, some resources (<em>e.g.</em> semaphores) that
should be dynamically allocated are allocated statically.
</p>
<p class="nobottommargin">
Older releases:
</p>
<ul>
<li> 2007.2 (November 2007)<br/>
Based on Linux 2.6.20. <br/>
<a href="download/litmus-rt-2007.2.patch">litmus-rt-2007.2.patch</a>
(328 KB)<br/>
<a href="download/liblitmus-2007.2.tgz">liblitmus-2007.2.tgz</a>
(11 KB) <br/>
<a href="download/libso-2007.2.tgz">libso-2007.2.tgz</a>
(16 KB) <br/><br/>
</li>
<li> 2007.1 (May 2007)<br/>
Based on Linux 2.6.20. <br/>
<a href="download/litmus-rt-2007.1.patch">litmus-rt-2007.1.patch</a>
(266 KB) <br/>
<a href="download/liblitmus-2007.1.tgz">liblitmus-2007.1.tgz</a>
(6.8 KB) <br/>
<a href="download/libso-2007.1.tgz">libso-2007.1.tgz</a>
(16 KB) <br/>
</li>
</ul>
</div>
<h2 id="install">Installation</h2>
<div class="box">
<p class="notopmargin">
LITMUS<sup>RT</sup> 2007.3 consists of an
extension of the Linux kernel that adds support for the sporadic task
model, a scheduler plugin infrastructure, and some scheduler plugins, as
well as two user-space libraries that provide the LITMUS<sup>RT</sup>
real-time API. Note, that the current implementation only works on the
Intel x86 architecture.
</p>
<h3>Patching the Kernel</h3>
<p class="notopmargin">
The extension to the Linux kernel is released as a patch against Linux
2.6.20. To install the LITMUS<sup>RT</sup> kernel, first <a
href="http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.20.tar.bz2">download the Linux
kernel 2.6.20</a> and untar it in a directory of your choice (hereafter
referred to as <span class="src">$DIR</span>). Second, apply the
LITMUS<sup>RT</sup> patch (see <a href="#download">Section Download</a>)
and configure, compile, and install the kernel as usual. The patch is <span
class="src">-p1</span> applicable.
To summarize, the LITMUS<sup>RT</sup> kernel can be obtained, patched, and
compiled with the following commands:
</p>
<pre class="shell">
cd $DIR
# get Linux 2.6.20
wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.20.tar.bz2
tar xjf linux-2.6.20.tar.bz2
wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2007.3/litmus-rt-2007.3.patch
mv linux-2.6.20 litmus-rt
# apply the LITMUS RT patch
cd litmus-rt
patch -p1 < ../litmus-rt-2007.3.patch
# create a working kernel configuration with HZ=1000
make gconfig
# compile the kernel
make bzImage
make modules
# proceed to install kernel, build initrd, etc.
...
</pre>
<p>
After the kernel has been compiled and installed, the boot-loader must be
configured to load the desired real-time scheduler plugin at boot time (run
time selection of the real-time scheduler is currently not supported). The
real-time scheduler plugin is selected with the <span
class="src">rtsched</span> kernel parameter.
</p>
<pre class="shell">
rtsched= {linux, pfair, part_edf, global_edf,
global_edf_np, edf_hsb, gsn_edf, psn_edf, adaptive}
</pre>
<p>
For example, on our test machine, we use the
following GRUB entry:
</p>
<pre class="shell">
title Kernel 2.6.20-LITMUSRT
root (hd0,5)
kernel /boot/vmlinuz-2.6.20-LITMUSRT root=/dev/sda6 ro vga=791 rtsched=gsn_edf
initrd /boot/kernel-2.6.20-LITMUSRT.img
</pre>
<h3>Libraries</h3>
<p class="notopmargin">
The two user-space libraries, <span class="src">liblitmus</span> and <span
class="src">libso</span>, provide their own makefiles and thus are easy to
compile. The kernel interface for real-time tasks is provided by <span
class="src">liblitmus</span>, which can be compiled as follows:
</p>
<pre class="shell">
cd $DIR
wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2007.3/liblitmus-2007.3.tgz
tar xzf liblitmus-2007.3.tgz
cd liblitmus
make
</pre>
<p>
The second library, <span class="src">libso</span>, provides shared object
and synchronization support for real-time tasks. It depends on <span
class="src">liblitmus</span> and must be installed in "parallel"
(they must have the same parent directory). The following commands will
obtain and compile <span class="src">libso</span>, including the test programs:
</p>
<pre class="shell">
cd $DIR
wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2007.3/libso-2007.3.tgz
tar xzf libso-2007.3.tgz
cd libso
make
make tests
</pre>
<p class="nobottommargin">
Please refer to the <a href="#doc">documentation</a> on how to use the LITMUS<sup>RT</sup>
real-time API as provided by <span class="src">libso</span> and
<span class="src">liblitmus</span>.
</p>
</div>
<h2 id="doc">Documentation</h2>
<div class="box">
<p class="notopmargin">
Most of the documentation has yet to be written. To get an overview of
the architecture of the kernel extension, we recommend to read the paper
<a href="http://www.cs.unc.edu/~anderson/papers/rtlws07.pdf">“LITMUS<sup>RT</sup>:
A Status Report”</a>.
</p>
<p>
The user space library that provides the LITMUS<sup>RT</sup> API,
<span class="src">liblitmus</span>, contains two example real-time tasks
(<span class="src">base_task.c</span> and
<span class="src">base_mt_task.c</span>)
that both illustrate how to use the API and provide a skeleton for real-time
task development. To get started with development, take a look these example
programs.
</p>
<p class="nobottommargin">
Please contact <span class="src">bbb[AT]cs.unc.edu</span> if you have any
questions.
</p>
</div>
<h2 id="credits">Credits</h2>
<div class="box">
<div style="float: right;">
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<p class="nomargin">
Linux is a registered trademark of Linus Torvalds. <br /> The
LITMUS<sup>RT</sup> logo was designed by <a
href="http://designs.primevalpress.com">Jasper McChesney</a> of <a
href="http://designs.primevalpress.com">Primeval Designs</a>. <br />
Web design by Björn Brandenburg.
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