RTXI Not Running in Real-Time Mode Despite EVL Kernel Installation

[hxywang7]

When launching RTXI, I receive the warning:

You are using the POSIX compatibility layer, RTXI is NOT running in realtime!!

I have installed RTXI using the EVL kernel, and my system reports running on 5.15.129-xenomai-4 when using uname -r
However, after verifying with the Xenomai testing suite (https://v4.xenomai.org/core/testing/), all tests pass, indicating that I should have a functioning EVL kernel core.

Despite this, RTXI does not seem to recognize the real-time environment.

System Information

• OS: Ubuntu 22.04.5 LTS
• Kernel Version: 5.15.129-xenomai-4
• RTXI Version: 3.2.0

[fusge]

It may be that the wrong version was installed, or that the installation occurred while on the non-realtime kernel. Either way you have to reinstall RTXI.

Please uninstall RTXI using the following commands. Before doing so make sure you have any data and settings backed up:

dpgk -r rtxi
dpgk -p rtxi

The above commands remove and purge all RTXI related files and plugins. Restart your computer Make sure that you are booted in the real-time kernel. Before continuing, If using National Instruments then also make sure that the support libraries and drivers are also installed or RTXI may not build with the needed drivers to interface with them.

Next Follow the instructions for installing RTXI. Select the EVL option for the Real-Time Kernel.

If the problem persists please respond here and we'll continue from there.

[hxywang7]

Thanks for your help. But the problem still persist.

I first uninstalled RTXI using:
dpkg -p rtxi
Then, I restarted the computer under kernel 5.15.129-xenomai-4.

To ensure the EVL core is running, I used:
sudo dmesg | grep -I evl
The output confirmed that the EVL core started successfully:

[    3.834809] IRQ pipeline: high-priority EVL stage added.  
[    3.835070] EVL: core started  

Next, I installed RTXI:

1. Installed dependencies: sudo ./scripts/install_dependencies.sh
2. Installed RTXI: ./scripts/install_rtxi.sh

During installation, I was prompted to select a kernel configuration:

-----> Starting RTXI installation...  
-----> Kernel configuration...  
evl -- Xenomai with EVL library (RT)  
xenomai -- Legacy Xenomai with Alchemy skin (RT)  
posix -- Linux-based core (Non-RT)  
-----> Please type your configuration and then press enter:  

I selected evl.

However, after completing the installation, RTXI still displayed the following warning:
***WARNING*** You are using the POSIX compatibility layer, RTXI is NOT running in realtime!!!

[fusge]

It may be that the build system can't find the evl library. Can you post the output of the following command?

which evl

If it does find a binary, please run the following command as well:

evl test

[hxywang7]

Thanks for your response!

Here's the output of the commands you suggested:

samsep10l@samsep10l-MS-7D78:~$ which evl
/usr/local/bin/evl

samsep10l@samsep10l-MS-7D78:~$ evl test
evl: no 'test' command. Try 'evl --help'.

Looks like the evl binary is found, but test isn't a valid command. Let me know what else I can check!

[thiagoburghi]

Running evl test with sudo worked. Here's the output:

basic-xbuf: OK
clock-timer-periodic: OK
clone-fork-exec: OK
detach-self: OK
duplicate-element: OK
element-visibility: OK
fault: OK
fpu-preload: OK
fpu-stress: OK
heap-torture: OK
mapfd: OK
monitor-deadlock: OK
monitor-deboost-stress: OK
monitor-event: OK
monitor-event-targeted: OK
monitor-event-untrack: OK
monitor-flags: OK
monitor-flags-broadcast: OK
../tests/monitor-flags-inband.c:92: FAILED: write(i_ffd, &n, sizeof(n)) (=Operation not permitted)
../tests/monitor-flags-inband.c:33: FAILED: read(i_ffd, &bits, sizeof(bits)) (=Operation not permitted)
** monitor-flags-inband: BROKEN

Not sure if the monitor thing is relevant.

Perhaps RTXI is not able to run evl propertly because of lack of sudo privileges?

[fusge]

That's odd. To double check please also run the following command:

pkg-config --list-all | grep evl

What output do you see?

[hxywang7]

✅ Issue Solved

Thanks for the support! The problem has been solved.

After investigation, the root cause turned out to be a stale librtxipal.so installed manually in /lib/ from a previous build. This file was not managed by dpkg or CMake's packaging system.

Although install_rtxi.sh correctly built and installed the EVL version of librtxipal.so into /usr/local/lib, RTXI was actually loading the outdated library from /lib due to it appearing earlier in the dynamic linker search path.

---

✔️ Solution steps:

1. Removed all stale copies:

   sudo rm -f /usr/lib/librtxipal.so
   sudo rm -f /usr/local/lib/librtxipal.so
   sudo rm -f /lib/librtxipal.so  # <-- this was the hidden culprit

2. Rebuilt RTXI cleanly and Installed the correct version:

    rm -rf build
   ./scripts/install_rtxi.sh

3. Verified that RTXI now correctly uses EVL:

   RTXI: Successfully attached thread to EVL!
   

---

💡 Recommendation:

It might be helpful to add a check in install_rtxi.sh to detect old librtxipal.so files in /lib, as they can cause confusion and are not managed by the package manager.

Thanks again for your help!