Can't switch to x11 sessions when using gdm

entreated · 2025-09-29 03:38:32

Not sure if this is related to other recent posts about issues with gnome 49 and systemd 258.

My normal workflow involves 2 user sessions that I switch between using CTRL+ALT+F2 and CTRL+ALT+F3, with gdm sitting on F1 (tty1). After the upgrade to gnome 49, my keyboard and mouse stop responding after trying to switch back to a session running x11. It goes like this:

- I'm greeted by gdm and log into user A, with plasma DE and x11.
- I switch to gdm's greeter and log into user B, with gnome DE and wayland.
- I try to switch back to user A using CTRL+ALT+F2.

After the last one the keyboard and mouse stop responding, while the screen is completely frozen. The system is still running as I'm able to login via ssh from another computer and restart gdm to recover control.

Same happens if I login to user A with x11, switch to the gdm greeter using CTRL+ALT+F1, and then try to switch back using CTRL+ALT+F2.

The problem doesn't seem to happen if the session uses wayland, or if I try a different display manager, such as sddm.

I don't see any errors in the journal, none that I can tell that could cause this.

A full journal log of the session here: https://pastebin.com/K1dDf53R

EDIT:

Forgot to mention. I'm using 2 GPUs, 1 is an nvidia RTX 5080 (card0) and the 2nd is the iGPU of a 7800x3d (card1). I use prime-offloading but otherwise the iGPU is the one handling the GUI.

Last edited by entreated (2025-09-29 05:22:13)

seth · 2025-09-29 08:37:46

Sep 28 23:04:41 cachyos kernel: Command line: initrd=\initramfs-linux-cachyos.img cryptdevice=UUID=876cc16c-b6ff-43bd-aee0-b284f0593c21:system root=/dev/mapper/system rootflags=subvol=@root rw nowatchdog splash nvidia-drm.modeset=0 zswap.enabled=1

https://bbs.archlinux.org/misc.php?action=rules

"nvidia-drm.modeset=0"
wtf?

Sep 28 23:05:05 home-desktop /usr/lib/gdm-x-session[2320]: (II) LoadModule: "amdgpu"
Sep 28 23:05:05 home-desktop /usr/lib/gdm-x-session[2320]: (II) Loading /usr/lib/xorg/modules/drivers/amdgpu_drv.so
Sep 28 23:05:05 home-desktop /usr/lib/gdm-x-session[2320]: (II) Module amdgpu: vendor="X.Org Foundation"
Sep 28 23:05:05 home-desktop /usr/lib/gdm-x-session[2320]: (II) AMDGPU: Driver for AMD Radeon:
Sep 28 23:05:05 home-desktop /usr/lib/gdm-x-session[2320]:         All GPUs supported by the amdgpu kernel driver
Sep 28 23:05:05 home-desktop /usr/lib/gdm-x-session[2320]: (II) AMDGPU(0): Creating default Display subsection in Screen section

Try to run on the modesetting driver, remove xf86-video-amdgpu

I switch to gdm's greeter and log into user B, with gnome DE and wayland.

rendered irrelevant by

Same happens if I login to user A with x11, switch to the gdm greeter using CTRL+ALT+F1, and then try to switch back using CTRL+ALT+F2.

Sep 28 23:04:44 cachyos systemd-logind[1017]: New session '1' of user 'gdm-greeter' with class 'greeter' and type 'wayland'.
Sep 28 23:04:44 cachyos systemd-logind[1017]: New session '2' of user 'gdm-greeter' with class 'manager-early' and type 'unspecified'.
Sep 28 23:05:04 home-desktop systemd-logind[1017]: New session '3' of user 'entreated' with class 'user' and type 'x11'.
Sep 28 23:05:04 home-desktop systemd-logind[1017]: New session '4' of user 'entreated' with class 'manager' and type 'unspecified'.
Sep 28 23:05:37 home-desktop systemd-logind[1017]: New session '5' of user 'gdm-greeter' with class 'greeter' and type 'wayland'.
Sep 28 23:05:37 home-desktop systemd-logind[1017]: New session '6' of user 'gdm-greeter' with class 'manager-early' and type 'unspecified'.

A mitigation approach could be to jam a console TTY between those, ie. KDE => TTY4 => GDM => TTY4 => KDE?

entreated · 2025-09-29 23:24:42

seth wrote:

Sep 28 23:04:41 cachyos kernel: Command line: initrd=\initramfs-linux-cachyos.img cryptdevice=UUID=876cc16c-b6ff-43bd-aee0-b284f0593c21:system root=/dev/mapper/system rootflags=subvol=@root rw nowatchdog splash nvidia-drm.modeset=0 zswap.enabled=1
https://bbs.archlinux.org/misc.php?action=rules
"nvidia-drm.modeset=0"
wtf?

I have that so it'd prevent the nvidia card from being picked before the AMD iGPU under certain circumstances, which then allows me to bind it with the vfio module for GPU passthrough.

Also, I'm only using cachyos' kernel, not the distro. If that's an issue I can post logs under vanilla/lts kernels instead, although this situation happens regardless of which kernel I use, lts included.

Try to run on the modesetting driver, remove xf86-video-amdgpu

After removing it no x11 session is able to start from gdm.

I'm able to provide my password, then the screen blinks and it places me back on gdm. If I try to login again I can click on my user, but I'm unable to type in the password field. At this point gdm is unresponsive and I need to restart the service. Wayland sessions seem to work fine.

https://pastebin.com/MKP34XbC

seth · 2025-09-30 06:10:40

After removing it no x11 session is able to start from gdm.

You have some configlet referencing it

Sep 29 18:51:00 home-desktop /usr/lib/gdm-x-session[2355]:         Using the first device section listed.
Sep 29 18:51:00 home-desktop /usr/lib/gdm-x-session[2355]: (**) |   |-->Device "iGPU"
…
Sep 29 18:51:00 home-desktop /usr/lib/gdm-x-session[2355]: (II) LoadModule: "amdgpu"
Sep 29 18:51:00 home-desktop /usr/lib/gdm-x-session[2355]: (WW) Warning, couldn't open module amdgpu
Sep 29 18:51:00 home-desktop /usr/lib/gdm-x-session[2355]: (EE) Failed to load module "amdgpu" (module does not exist, 0)
Sep 29 18:51:00 home-desktop /usr/lib/gdm-x-session[2355]: (EE) No drivers available.

Remove that, too.

grep -ri amdgpu /{etc,usr/share}/X11/xorg.conf*

Arch Linux

#1 2025-09-29 03:38:32

Can't switch to x11 sessions when using gdm

#2 2025-09-29 08:37:46

Re: Can't switch to x11 sessions when using gdm

#3 2025-09-29 23:24:42

Re: Can't switch to x11 sessions when using gdm

#4 2025-09-30 06:10:40

Re: Can't switch to x11 sessions when using gdm

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