Debian hangs

Hi,

I had a machine running under Linuxcnc. Presumably this Machine ran wheezy and the RTAI kernel. I set this up a few years ago and it was running fine on a Dell Optiplex 980. I may have configured some kernel options but I forgot those

Recently I wanted to add some ngcui routines to my system and since this did not work out of the box I thought my installation is too old and I need to upgrade Linuxcnc. I thought I could just do a system update as well and move to buster. Now I wish I never touched this installation !

I have now tried:
- Standard Buster installation + Kernel replacement with PREEMT RT + Linuxcnc v2.8 (I suppose)
- Jessie installation from Linuxcnc Live image
- Wheezy Installation from Linuxcnc Live image

I'm getting roughly the same result in all cases: The machine freezes so that I can no longer use X. Sometimes the mouse does no longer move. Sometimes the PC reboots. When the system freezes REISUB does not work. The logs don't provide me any insights.

Overall I'm pretty frustrated now and which I had better documented my old system (or kept)
Maybe somebody have an idea.

I captured the logs on the Buster installation here:
Output of dmesg: pastebin.com/zgh6Cw84
Xorg.0.log:https://pastebin.com/eNJCLTWf
/var/log/messages pastebin.com/EbJh4qYY

BR,
Malte

Ok i think I got it now.

I have an Dell made NVidia Card (don't recall which chipset exactly) on my Dell Optiplex 980 system. I identified the Nouveau Xorg driver as reason for these stalls / crashes. I did replace (*) this with the vesa driver now. This behavior was verified with wheezy /RTAI kernel and strech / PREEMT RT.
Wheezy showed larger jitter on the servo thread and the machine sounded unhealthy so I ended up with Stretch. With isolcpus=3 this seems to provide a stable system (I still have to do some longer tests) and I get a jitter of about 11000ns.
I think I probably used the Nvidia driver on my old installation. I was not able to get the Nvidia driver to work with Stretch though.

(*) this requires blacklisting the kernel module and creating xorg.conf + modifying this to use vesa