Kernel 6.12 with PREEMPT_RT patches enabled - yet POSIX non-realtime (LM22.1)

I've tried both RIP and building into a .deb and installing, but both ways it appears that it doesn't recognize the kernel has PREEMPT_RT enabled.

I have kernel 6.12.9 (although latency-test displays 6.12.0 for some reason?) and went through the menu config to set it for fully pre-emptable kernel and build it.

I'm on Linux Mint 22.1 and I can run simulations just fine in both RIP and the installed versions, but I run a mesa card and require HOSTMOT2 functioning properly which is where the issue arises.

Running latency-test results in some crazy huge numbers   and it specifies POSIX non-realtime in the terminal.

I'm not sure if there's an additional step that I've missed to ensure LCNC "sees" the kernel has the patch enabled - perhaps the string has changed? I tried searching the forum and only came across RPI results but not x86.

 

Editing the above message appears to break it so replying instead - running uname -r it appears I have a skill issue and it returns 6.12.0, which is what I clearly accidentally had built. There may be issues in 6.12.0 that were resolved by 6.12.9 that resolve this, so a quick rebuild (well, not quick it takes forever) and I'll report back.

That's a known issue.
I've been building 6.12.11 kernels, for arm, but it needs a patch.

In case you aren't aware.
You'll also have to select Fully Preempt kernel, not low latency desktop, this option will only show up if you select enable expert under general.


[*] Configure standard kernel features (expert users)

(X) Fully Preemptible Kernel (Real-Time)

I'm giving it a go now, just to make sure I'm giving you the right info, if it works out I'll post a link to the debs. I'm building on Mint 21.3 Virginia.

I selected full pre-emptible

I documented all my steps here to get it to work, as i needed a couple workarounds on LM
iamtherealbeef.com/content/linuxcnc-on-linuxmint-22/

 

Bog standard kernel on Mint 21.3 Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz with 2 threads per core enabled, testing whilst building a RT kernel.

Same again but just with servo thread.
 

Kernel packages
drive.google.com/drive/folders/1MimfKsSD...FtRRV?usp=drive_link

Thanks, that patch file was exactly what I needed for it to work properly - I had rebuilt it at the same time and it worked without issues.

Good to hear.
Actually it’s made me realise I have to update my Mint boxes. So thanks to you.

The patch brings back the indicator (/sys/kernel/realtime) that LinuxCNC uses to check if the OS is realtime. This is a part of the realtime patches that didn't become mainline.

forum.linuxcnc.org/38-general-linuxcnc-q...6-12?start=10#315437