3.33.90: failure to resume gdm from backlight off and logout

Summary: While at gdm, screen goes black (expected) after period of time, backlight turns off. When I tap a key, e.g. spacebar, backlight comes on, I see a mouse arrow which is frozen, but no other UI. I cannot switch to a tty. I do have access via ssh.

Problem is semi reproducible. Complete journal. journal4.txt

System info:
Macbook Pro 2011, i915 graphics (radeon disabled)
Fedora 31 Workstation
kernel-5.3.0-0.rc6.git1.1.fc32.x86_64
gdm-3.33.90-3.fc31.x86_64
gnome-settings-daemon-3.33.90-1.fc31.x86_64
gnome-shell-3.33.91-1.fc31.x86_64
mutter-3.33.91-1.fc31.x86_64
clutter-1.26.2-9.fc31.x86_64
mesa-dri-drivers-19.2.0~rc1-2.fc31.x86_64

The only messages in the journal at the time I tap on the keyboard to "wake" up the display:

[ 4074.867452] fmac.local pkexec[4562]: gdm: The value for the SHELL variable was not found the /etc/shells file [USER=root] [TTY=unknown] [CWD=/var/lib/gdm] [COMMAND=/usr/libexec/gsd-backlight-helper /sys/devices/pnp0/00:03/backlight/gmux_backlight 35862]
[ 4074.871628] fmac.local org.gnome.SettingsDaemon.Power.desktop[4167]: The value for the SHELL variable was not found the /etc/shells file
[ 4074.871628] fmac.local org.gnome.SettingsDaemon.Power.desktop[4167]: This incident has been reported.
[ 4074.875096] fmac.local gsd-power[4167]: Error executing backlight helper: Child process stopped by signal 0
[ 4074.918180] fmac.local gnome-shell[4043]: (../src/backends/native/meta-renderer-native.c:2211):meta_onscreen_native_swap_buffers_with_damage: runtime check failed: (onscreen_native->gbm.next_fb == NULL)
[ 4080.487535] fmac.local pkexec[4564]: gdm: The value for the SHELL variable was not found the /etc/shells file [USER=root] [TTY=unknown] [CWD=/var/lib/gdm] [COMMAND=/usr/libexec/gsd-backlight-helper /sys/devices/pnp0/00:03/backlight/gmux_backlight 40752]
[ 4080.489605] fmac.local org.gnome.SettingsDaemon.Power.desktop[4167]: The value for the SHELL variable was not found the /etc/shells file
[ 4080.489605] fmac.local org.gnome.SettingsDaemon.Power.desktop[4167]: This incident has been reported.
[ 4080.490999] fmac.local gsd-power[4167]: Error executing backlight helper: Child process stopped by signal 0
[ 4086.102836] fmac.local pkexec[4565]: gdm: The value for the SHELL variable was not found the /etc/shells file [USER=root] [TTY=unknown] [CWD=/var/lib/gdm] [COMMAND=/usr/libexec/gsd-backlight-helper /sys/devices/pnp0/00:03/backlight/gmux_backlight 39937]
[ 4086.103772] fmac.local org.gnome.SettingsDaemon.Power.desktop[4167]: The value for the SHELL variable was not found the /etc/shells file
[ 4086.103772] fmac.local org.gnome.SettingsDaemon.Power.desktop[4167]: This incident has been reported.
[ 4086.105485] fmac.local gsd-power[4167]: Error executing backlight helper: Child process stopped by signal 0

There is a gdm login session 'c2' and it's a wayland session.

I was able to recover by:

# systemctl isolate multi-user.target
# systemctl isolate graphical.target

That happens at monotonic time [ 5170.808096] in the attached log.

I login via gdm again at [ 5431.614929], play around with the display and keyboard brightness keys [ 5445.788880], [ 5463.108728], and then soon after that I go to log out, about [ 5571.430458], and I do not get back to gdm, I get a black screen with a few rows of @@@@@@@ characters, and then a black screen of nothing but backlight stays on.

So yeah gdm problems.