Arch Linux

javex

Member

Registered: 2011-12-30

Posts: 76

Kernel NULL pointer dereference with TB16 Thunderbolt Dock

I'm not quite certain what exactly the cause of this issue is but I am seeing a kernel error message under a certain combination of conditions and I'm pretty sure it's an issue with the i915 driver. Here is what's happening: I have a Dell XPS 13 9360 with a Thunderbolt dock (Dell TB16) and whenever it is plugged in while booting, I see a call trace printed on the screen under certain conditions.

* TB16 unplugged: No issues in any combination
* TB16 + early KMS (i915): Kernel panic
* TB16 + late KMS + Wayland: Kernel panic
* TB16 + late KMS + X: No issues

I cannot figure out if there is any way to actually write a log file for this situation so unfortunately, all I have a photos of the monitor. I put them in this album.

What I can see from that is that "intel_digital_connector_atomic_check" causes the error and seems to be part of i915, plus the "drm_kms_helper" seems to indicate it has to do with KMS.

Interestingly, if I wait until KMS has finished (with early KMS when it prompts for my LUKS passphrase, with late KMS when I GDM is up), I can plug in the Thunderbolt cable and have no issues whatsoever.

uname:

5.7.9-arch1-1 #1 SMP PREEMPT Thu, 16 Jul 2020 19:34:49 +0000 x86_64 GNU/Linux

Relevant packages:

% pacman -Q linux xf86-video-intel     
linux 5.7.9.arch1-1
xf86-video-intel 1:2.99.917+908+g7181c5a4-1

I have uploaded my dmesg output from a successful early KMS boot with the dock unplugged. As mentioned, I don't know if it's possible to get a log of this at all...? If there are instructions of how to turn this into something that can be debugged that'd be great.

What are good next steps for me? Is this a kernel bug or am I doing something wrong?

Last edited by javex (2020-07-20 09:47:35)

loqs

Member

Registered: 2014-03-06

Posts: 17,314

Re: Kernel NULL pointer dereference with TB16 Thunderbolt Dock

https://gitlab.freedesktop.org/drm/intel/-/issues/2091 try linux-mainline 5.8-rc6 also available from Unofficial_user_repositories#miffe.

javex

Member

Registered: 2011-12-30

Posts: 76

Re: Kernel NULL pointer dereference with TB16 Thunderbolt Dock

Hi loqs,

Thanks for the quick reply. I don't really know why this didn't come up in my search, but yes that seems to be exactly my issue. I looked into the mainline kernel yesterday, but if the options are either to self-compile or use an unofficial repo, I think I'll wait. I'm glad to know that it's a known issue and will be fixed when I upgrade to 5.8 once it's made it into the standard arch kernel. Until then, I can easily only plug in my dock once the system is up and running which works just fine.

Do you want me to keep this topic open until I could confirm the fix worked once the new package is out or should I mark it as solved now?

Last edited by javex (2020-07-21 12:56:25)

fmc000

Member

Registered: 2020-05-12

Posts: 43

Re: Kernel NULL pointer dereference with TB16 Thunderbolt Dock

Hi loqs,

Thanks for the quick reply. I don't really know why this didn't come up in my search, but yes that seems to be exactly my issue. I looked into the mainline kernel yesterday, but if the options are either to self-compile or use an unofficial repo, I think I'll wait. I'm glad to know that it's a known issue and will be fixed when I upgrade to 5.8 once it's made it into the standard arch kernel. Until then, I can easily only plug in my dock once the system is up and running which works just fine.

Do you want me to keep this topic open until I could confirm the fix worked once the new package is out or should I mark it as solved now?

Using Miffe's repo is not a problem at all, it works just fine for me. Unless you don't trust him.