The nvidia propriety driver doesn't build against the linux kernel with the -rt (real-time) patch applied.
Searching the web, I've found a patch for nvidia 256.44 on linux 18.104.22.168-rt29 at
Small changes were required to get the patch working on 260.9.14.
I've attached the updated patch.
Apply the patch as follow to the nVidia driver (assuming that you're using the nVidia driver with CUDA development support)
1) ./devdriver_3.2_linux_32_260.19.14.run --extract-only
2) cd /tmp/NVIDIA_Linux-x86-260.19.14/kernel
3) Move the patch to this directory
4) Apply the patch: cat patch.txt | patch -p2
The output should state: patching file nv-linux.h
5) cd ..
6) Build the module:
./nvidia-installer -K --kernel-name=22.214.171.124-rt29
This was all that was required for me.