Display connected using DisplayLink (USB-C Dock with DisplayPort) causes wingpanel to segfault

[lfuelling]

Hi,

I recently got a new laptop and installed elementaryOS on it. It features USB-C/Thunderbolt3, which I use to connect to a USB-C Dock where I plugged in my DisplayPort monitor. This currently requires the DisplayLink driver to support display output over Thunderbolt at all.

Description

When I connect the dock and the display is detected, the desktop freezes after displaying the background on the second monitor. I can still move the mouse, but the movement is only visible on the second monitor. The internal display is completely frozen. There is also nothing on the second display except the background and the mouse pointer (the mouse pointer can still be moved over to the internal display, it just doesn't show.

The only thing I found in dmesg that seems to be connected to the problem is a segfault in wingpanel, hence this bug report.

[    89.386327] wingpanel[2315]: segfault at 48 ip 00005627bfe28f13 sp 00007ffc0ef24780 error 4 in wingpanel[5627bfe1d00+14000]

Workarounds

• When I restart the laptop and do a sudo killall wingpanel && sudo killall gala in TTY1 then switch to TTY7 (ui) and insert the DisplayPort cable into the dock, the second display works without freezing. Obviously this is not a real workaround as there is no visible UI except for the background, mouse pointer and any autostart app.

• Fyi, I also tried the display when running GNOME. It works without freezing there but the mouse pointer has a square of glitch around it so this is also unuseable as a workaround.