X.Org: invoking xinput --disable [ || --enable] <device_xID> kills gdm user session

[Peter Hutterer]

On Sun, Apr 11, 2021 at 08:39:54PM +0200, Cedric Bhihe wrote:
> Hi folks,
> 
> [Background info: host OS is Arch linux 5.11.12 with gdm 40.0.1 on xorg]
> 
>  For the past 4 days, I have this weird mix-up between issuing either of the
> following cmds in a `tmux` terminal:
> 
>      $ /usr/bin/xinput --disable <xID>
> or
>      $ /usr/bin/xinput --enable <xID>
> 
> where <xID> is my Touchpad xorg device ID (=14) on a Dell XPS15, obtained
> with
>      $ /usr/bin/xinput --list --short

First note: you can use the device name, so `xinput disable "my device
name"` - you do not need to use the ID. This has worked for probably a
decade or more now.

> Issuing either one of the above cmds instantly kills my gdm user session,
> along with all that was going on in it. Next it lands me on the gdm user
> login frame, where I can start a new user session as if nothing had
> happened. Everything else seems completely normal.

most likely a crash in the X server, please check your journal for any
backtraces and file an issue against the X server (cc @whot, i.e. me)  and
we can have a look.

Cheers,
   Peter

> 
> The touchpad's driver is: xf86-input-synaptics 1.9.1-2 (could not find a
> reference to a recent update)
> The xorg-xinput version is 1.6.3-2, upgraded from 1.6.3-1 on 2020.05.19 (way
> before the issue appeared)
> On the other hand, gdm + the linux kernel and headers were upgraded recently
> (from /var/log/pacman.log):
>     - [2021-04-09T08:29:29+0200] [ALPM] upgraded linux (5.11.11.arch1-1 ->
> 5.11.12.arch1-1)
>     - [2021-04-09T08:29:30+0200] [ALPM] upgraded gdm (3.38.2.1-1 -> 40.0-1)
> 
> I have looked up FAQs, misc FAQs and extra FAQs and all I could on get my
> eyes on at xorg, as well as the knowledge base on StackExchange, in addition
> to having scanned the web, by I found absolutely no chatter on anything
> similar to that issue.
> 
> I'm stumped in part because I've used the above cli cmds for years to
> activate/deactivate my laptop's touchpad on the fly (on the same box) and I
> never had an issue.
> 
> I'm stumped and would be grateful for any pointer.
> 
> PS: I have not cross posted on gdm yet. Will do so in a few days only if
> needed or recommended by someone deeper than me on the issue.