Xorg sometimes segfaults on monitor setup

[joren485]

• Are you using the latest driver?

$ pacman -Q displaylink
displaylink 5.4-3

• Are you using the latest EVDI version?

$ pacman -Q evdi-git
evdi-git 1.9.1.r4.gb0b3d13-1

• If you are using a DisplayLink device, have you checked 'troubleshooting'
  on DisplayLink's website?

Yes

• Is this issue related to evdi/kernel?

Yes

• Linux distribution and its version: Arch Linux
• Linux kernel version: 5.12.15-arch1-1
• Xorg version

$ pacman -Q xorg-server
xorg-server 1.20.12-1

• Desktop environment in use

$ pacman -Q i3-wm
i3-wm 4.19.2-1

Description

When I setup two Displaylink connected monitors directly after login, Xorg sometimes segfaults.

After I login I use (a script that executes) xrandr that sets up two monitors. Sometimes (not always) Xorg crashes with a segmentation fault during this setup. On the second try (i.e. after Xorg has crashed), xrandr always succeeds.

The xrandr command is xrandr --output eDP-1 --primary --mode 1920x1080 --pos 0x0 --output DVI-I-2-2 --mode 1920x1080 --pos 1920x0 --output DVI-I-1-1 --mode 1920x1080 --pos 3840x0.

When Xorg crashes it produces this backtrace:

[    26.149] (EE) 
[    26.149] (EE) Backtrace:
[    26.150] (EE) 0: /usr/lib/Xorg (xorg_backtrace+0x53) [0x55646cb5ffd3]
[    26.150] (EE) 1: /usr/lib/Xorg (0x55646ca19000+0x151df5) [0x55646cb6adf5]
[    26.150] (EE) 2: /usr/lib/libc.so.6 (0x7f6b4b02b000+0x3cf80) [0x7f6b4b067f80]
[    26.150] (EE) 3: /usr/lib/xorg/modules/drivers/modesetting_drv.so (0x7f6b4a381000+0x13853) [0x7f6b4a394853]
[    26.150] (EE) 4: /usr/lib/Xorg (RRCrtcSet+0x7e2) [0x55646cacd5a2]
[    26.150] (EE) 5: /usr/lib/Xorg (ProcRRSetCrtcConfig+0x547) [0x55646cace507]
[    26.150] (EE) 6: /usr/lib/Xorg (0x55646ca19000+0x3a195) [0x55646ca53195]
[    26.150] (EE) 7: /usr/lib/libc.so.6 (__libc_start_main+0xd5) [0x7f6b4b052b25]
[    26.151] (EE) 8: /usr/lib/Xorg (_start+0x2e) [0x55646ca535de]
[    26.151] (EE) 
[    26.151] (EE) Segmentation fault at address 0x29
[    26.151] (EE) 
Fatal server error:
[    26.151] (EE) Caught signal 11 (Segmentation fault). Server aborting
[    26.151] (EE) 
[    26.151] (EE) 

I have also opened an issue on the Xorg Gitlab about this.

[joren485]

I decided to bite the bullet and get a new (thunderbolt 3) dock that does not use Displaylink.

I will leave this issue open for now, but you can close it if you wish.

[groovyman]

I had a similar weired behaviour with KDE-X11, that causes some crashed and an enormous lag on my laptop. When i select KDE-Wayland i was able to adress 2 of my 3 4K Monitors (with one cursor on each monitor ... sic ).
Anyway it was surprising to me, that Wayland was more stable than the good ole X11.
The lag way also relative low with wayland but anyway not acceptable, when you see how it works in Windows. But the CPU consumption was with more than 100% still a desaster.

[synaptics-lspintzyk]

Please try that module option(initial_device_count):
https://github.com/DisplayLink/evdi/blob/main/module/README.md#module-options