(Beta) Xenomai 3.0.5 on Ubuntu 14.04/16.04

These instructions demonstrates how to build a Cobalt Core for Xenomai 3.0.5.

Official documentation is available at https://xenomai.org/installing-xenomai-3-x/

Allow non-root users

sudo addgroup xenomai --gid 1234
sudo addgroup root xenomai
sudo usermod -a -G xenomai $USER

Tip

If the addgroup command fails (ex: GID xenomai is already in use), change it to a different random value, and report it in the next section.

Configure GRUB and reboot

Edit the grub config :

sudo nano /etc/default/grub

GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 4.9.38-xenomai-3.0.5"
#GRUB_DEFAULT=saved
#GRUB_SAVEDEFAULT=true
# Comment the following lines
#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=5
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash xenomai.allowed_group=1234"
GRUB_CMDLINE_LINUX=""

Note

Please note the xenomai group (here 1234) should match what you set above (allow non-root users).

Tip

noapic option might be added if the screen goes black at startup and you can’t boot.

If you have an Intel HD Graphics integrated GPU (any type) :

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_rc6=0 i915.enable_dc=0 noapic xenomai.allowed_group=1234"
# This removes powersavings from the graphics, that creates disturbing interruptions.

If you have an Intel Skylake (2015 processors), you need to add nosmap to fix the latency hang (https://xenomai.org/pipermail/xenomai/2016-October/036787.html) :

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_rc6=0 i915.enable_dc=0 xeno_nucleus.xenomai_gid=1234 nosmap"

Update GRUB and reboot

sudo update-grub
sudo reboot

Installing Xenomai 3.0.5 User space libraries

First, make sure that you are running the cobalt kernel :

uname -a
# Should return Linux waro-rt 4.9.38-xenomai-3.0.5 #2 SMP Wed Sep 20 16:00:12 CEST 2017 x86_64 x86_64 x86_64 GNU/Linux
dmesg | grep Xenomai
# [    1.417024] [Xenomai] scheduling class idle registered.
# [    1.417025] [Xenomai] scheduling class rt registered.
# [    1.417045] [Xenomai] disabling automatic C1E state promotion on Intel processor
# [    1.417055] [Xenomai] SMI-enabled chipset found, but SMI workaround disabled
# [    1.417088] I-pipe: head domain Xenomai registered.
# [    1.417704] [Xenomai] allowing access to group 1234
# [    1.417726] [Xenomai] Cobalt v3.0.5 (Sisyphus's Boulder) [DEBUG]

cd xenomai-3.0.5
./configure --with-pic --with-core=cobalt --enable-smp --disable-tls --enable-dlopen-libs --disable-clock-monotonic-raw
make -j`nproc`
sudo make install
# --disable-clock-monotonic-raw : http://xenomai.org/pipermail/xenomai/2017-September/037695.html

Prevent Gazebo compiling issues

Proper fix : use Xenomai git repo

The issue has been fixed with commits 5ec8be8 and 1ed69a6.

git clone https://git.xenomai.org/xenomai-3.git
cd xenomai-3
./script/bootstrap
./configure --with-pic --with-core=cobalt --enable-smp --disable-tls --enable-dlopen-libs
make -j`nproc`
sudo make install

Hack with v3.0.5

Gazebo won’t compile because of some conflicting macros ( clz() ) present in libtbb and libcobalt. Remove this macro from xenomai to hack-fix it. It is only used in xenomai internals so won’t cause any issue in user-land. use this hack only if you install xenomai from the 3.0.5 package, not the git repo.

# http://xenomai.org/pipermail/xenomai/2017-September/037729.html
sudo sed -i 's/clz/__clz/g' /usr/xenomai/include/boilerplate/compiler.h

Update your bashrc

echo '
### Xenomai
export XENOMAI_ROOT_DIR=/usr/xenomai
export XENOMAI_PATH=/usr/xenomai
export PATH=$PATH:$XENOMAI_PATH/bin:$XENOMAI_PATH/sbin
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$XENOMAI_PATH/lib/pkgconfig
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$XENOMAI_PATH/lib
export OROCOS_TARGET=xenomai
' >> ~/.xenomai_rc

echo 'source ~/.xenomai_rc' >> ~/.bashrc
source ~/.bashrc

Test your installation

xeno latency

This loop will allow you to monitor a xenomai latency. Here’s the output for a i7 4Ghz :

== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT|  00:00:01  (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD|      0.174|      0.464|      1.780|       0|     0|      0.174|      1.780
RTD|      0.088|      0.464|      1.357|       0|     0|      0.088|      1.780
RTD|      0.336|      0.464|      1.822|       0|     0|      0.088|      1.822
RTD|      0.342|      0.464|      1.360|       0|     0|      0.088|      1.822
RTD|      0.327|      0.462|      2.297|       0|     0|      0.088|      2.297
RTD|      0.347|      0.463|      1.313|       0|     0|      0.088|      2.297
RTD|      0.314|      0.464|      1.465|       0|     0|      0.088|      2.297
RTD|      0.190|      0.464|      1.311|       0|     0|      0.088|      2.297

Tip

To get pertinent results, you need to stress your system while running the latency test. The latency has to be stable even if the system is under load.

sudo apt install stress
# Using stress
stress -v -c 8 -i 10 -d 8

Fix negative latency issues

You need to be in root sudo -s, then you can set values to the latency calibration variable in nanoseconds:

$ echo 0 > /proc/xenomai/latency
# Now run the latency test

# If the minimum latency value is positive,
# then get the lowest value from the latency test (ex: 0.088 us)
# and write it to the calibration file ( here you have to write 88 ns) :
$ echo my_super_value_in_ns > /proc/xenomai/latency

Source : https://xenomai.org/pipermail/xenomai/2007-May/009063.html