VM hangs for several minutes because of cpu stall

[Guilherme Fernando Werlang Pagel]

I noticed today at around 18:00 PM GMT-3 that my server was not responding to requests, after some minutes, the system started responding again and I started doing some investigation to figure out what happened. For my telemetry data, what was happening is that some processes were stuck doing IO for several minutes.

Since this is very odd, I decided to take a look at the kernel information to see if I could find some tips, and indeed I found, basically, the kernel logs showed me that the kernel was stalling tasks per core, resulting in the whole system stalling.

I added the kernel log with the important bits to help debug.

So, as far as I know, this is a bug from the server side and is not something that I can do a whole lot about, but if I'm wrong please give me some guidance on how to fix it.

The machine is using Ubuntu LTS version 20.04, kernel 5.4.0-09-generic. in a B2-7 VM.

PS. I also saw something very similar in another VM I have early in the day, the VM was unresponsive too but I didn't check the logs for that machine yet to see if it is the same issue but seems like it.

[Chris Guiver (guiverc)]

Thank you for taking the time to report this bug and helping to make Ubuntu better.

Bug reporting is mostly about finding & fixing problems thus preventing future users from hitting the same bug.

I suspect a Support site would be more appropriate, eg. https://answers.launchpad.net/ubuntu. You can also find help with your problem in the support forum of your local Ubuntu community http://loco.ubuntu.com/ or asking at https://askubuntu.com or https://ubuntuforums.org, or for more support options please look at https://discourse.ubuntu.com/t/community-support/709

You've reported this error is with the Ubuntu Manual, but haven't provided any page or other references that allow us to understand what section of the manual you suggest has errors (ie. the bug) and needs correction or attention.

Please provide the URL or detail of where you believe the documentation is incorrect, or was your filing a bug in the documentation done in error? I'd suggest support would be more useful to you.

I'll mark this bug as incomplete; if you believe I'm in error, you can return the status to "New", but please provide information via comment, as to where the Ubuntu Manual/documentation is in error, so we can work on the 'bug' in the documentation.