Comment 0 for bug 1799497

My main server has been running into hard lockups about once a week ever since I switched to the 4.15 Ubuntu 18.04 kernel.

When this happens, nothing is printed to the console, it's effectively stuck showing a login prompt. The system is running with panic=1 on the cmdline but isn't rebooting so the kernel isn't even processing this as a kernel panic.

As this felt like a potential hardware issue, I had my hosting provider give me a completely different system, different motherboard, different CPU, different RAM and different storage, I installed that system on 18.04 and moved my data over, a week later, I hit the issue again.

We've since also had a LXD user reporting similar symptoms here also on varying hardware:
  https://github.com/lxc/lxd/issues/5197

My system doesn't have a lot of memory pressure with about 50% of free memory:

root@vorash:~# free -m
              total used free shared buff/cache available
Mem: 31819 17574 402 513 13842 13292
Swap: 15909 2687 13222

I will now try to increase console logging as much as possible on the system in the hopes that next time it hangs we can get a better idea of what happened but I'm not too hopeful given the complete silence on the console when this occurs.

System is currently on:
  Linux vorash 4.15.0-36-generic #39-Ubuntu SMP Mon Sep 24 16:19:09 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

But I've seen this since the GA kernel on 4.15 so it's not a recent regression.