Comment 55 for bug 1727662

I reported this issue in the Ubuntu bug tracker:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1727662
I was advised to cross post it here.

It can be reproduced in the latest Mainline kernel 4.14-rc8
http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.14-rc8/
but doesn't seem to appear (after 1.5 days of testing) with the current drm-tip build
http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-tip/current/

Copying original bug description here:
"What happens is after I dock my laptop into a Lenovo ThinkPad Ultra Dock Type 40A2 20V, lock it via clicking the lock icon, and wait ~30 minutes, one of the following three things happen ~50% of the time when I come back to unlock it:
* Most of the time the computer is found shut down.
* Sometimes the notebook screen flickers weirdly and one of the two external monitors show pixelation.
* The notebook screen shows the lock screen but is completely frozen. Occasionally unlocking works.

I have two external monitors attached to the docking station.

When I dock my laptop, the battery indicator does recognize its charging.

I've not seen this issue when:
1) With the laptop in the dock, while actively using the laptop.
2) With the laptop out of the dock and no external monitors present.

This bug started after upgrading from Ubtuntu 17.04 to Ubuntu 17.10.

Using or not using the following kernel parameter didn't change anything:
i915.enable_rc6=0

PC temperatures are normal as per lm-sensors."