Just for the record, someone else was debugging this a few days later: https://bugzilla.kernel.org/show_bug.cgi?id=210241 And proposed a patch, which fixes the issue for both them and me: https://patchwork.kernel.org/project/linux-input/patch/20201119082232.8774-1... Regards, Merlin On Fri, 6 Nov 2020 06:08:09 +0100, Merlin Büge wrote:
Hi all.
I think I need some help with debugging an issue I have.
I recently bought an "Apple Magic Trackpad 2" for reducing strain on my hand (since I have some RSI[0] issues currently), which is supported in Linux since version 4.20[1].
After connecting it to my laptop it worked instantly at first, but "sometimes" un- and replugging the trackpad crashes my system. Often it works fine, but every now and then it triggers `general protection faults` (often while opening big applications like Firefox), causes my status bar to hang up, and usually ends in a freeze. Sometimes, just before the freeze I get thrown back to the console and see a kernel panic at the end of the log.
The laptop is a Thinkpad X200 running stock BIOS, Arch Linux and sway, with microcode updates enabled. I could also reproduce the issue with Gnome on Wayland. On Xfce I could not reproduce the issue, and also not on Fedora (which I installed on the same laptop to the same SSD, for testing).
I'm using the trackpad only via the USB cable, not via bluetooth.
Attached is a snippet from the dmesg output with debug logging enabled (appended `debug` on the kernel cmdline) showing some of the protection faults. I uploaded the full dmesg output here [2]. In this specific dmesg output, most of the protection faults happened concurrently while I was opening Firefox (several times to provoke the crash). A photo of the kernel panic can be found here [3].
This kernel bug report[4] and related arch report[5] seem related to the issue, maybe it's even the same issue? However, the kernel bug report mentions that the issue only affects linux >=5.8.7. In my case, I could reproduce the issue with the following linux versions (installed from the Arch Linux archive):
4.20.0 4.20.1 4.20.3 4.20.7 5.0.0 5.0.13 5.4.74 5.2.0 5.8.6 5.8.7 5.8.8 5.9.2, 5.9.4 5.10rc-2
The USB ID of the trackpad is 05ac:0265.
Because I'm very inexperienced with kernel debugging I would appreciate any help/pointers to what would be wise to test next. If this is likely to be an issue with the Linux kernel and not arch-related (unsure, since I could not reproduce it on other distros), please tell me so and I will post to the kernel bug tracker instead.
Thanks!
Merlin Büge
[0]: https://web.eecs.umich.edu/~cscott/rsi.html [1]: https://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid.git/commit/?h=for-next&id=9d7b18668956c411a422d04c712994c5fdb23a4b [2]: https://0x0.st/idkH.json [3]: https://0x0.st/idkz.jpg [4]: https://bugzilla.kernel.org/show_bug.cgi?id=209239 [5]: https://bugs.archlinux.org/task/67860
-- Merlin Büge