cRIO-9047 running Linux Locking Up

[t.erickson]

I am running LabVIEW 2024 Q3 on a cRIO-9047 with the embedded UI enabled. NI Linux Real-Time x64 6.1.92-rt32.

Two days ago I left the cRIO running overnight. The next morning the display port was not working. I found an NI support page that suggested sending a command to keep the monitor alive so I put that in.

I left the cRIO app running overnight again last night. In the morning the FPGA code was still running, evident by the user LED blinking which I put in the FPGA code. However, the screen is frozen. I am not sure if it is just the screen or the application but neither the mouse nor keyboard respond. Neither can I connect from windows so it appears the cRIO is locked up. However, I can ping it but WinSCP cannot find it.

I power cycled the cRIO and it started back up fine.

I was really counting on using the embedded UI feature.

I am not the only one: https://lavag.org/topic/23769-compactrio-locking-up/?_fromLogin=1

[gratian.crisan]

Hi @t.erickson,

Can you check the /etc/rtgroups file on cRIO and modify it to look like this: https://raw.githubusercontent.com/ni/meta-nilrt/refs/heads/nilrt/master/scarthgap/recipes-rt/rtctl/f... (or copy the github file directly on the target)

You can ignore all lines that start with '#' (those are just comments).

I particular make sure it has these lines at the bottom:

rcu:f:2:*:\[rcu(b|c|og)\/[0-9]+\]$
rcu_preempt:f:2:\[rcu_preempt\]$
ksoftirqd:f:1:*:\[ksoftirqd\/.+\]$

We've seen a priority inversion with one of the kernel threads (ksoftirqd) which in certain situations could lead to symptoms like the ones you're seeing.

The issue was fixed in this commit. However I think that was after the 2024Q3 release.

Reboot the cRIO after making the changes. Report back if it fixes the problem.

Otherwise we may need to dig deeper into the reproducing case which probably means creating an official support request.

[t.erickson]

Found out this is a known bug, fixed in NI Linux RT 2024 Q4.