Mutter autopkgtests are failing if a GPU exists but is not accessible

[Daniel van Vugt]

Mutter autopkgtests are failing if a GPU exists but is not accessible. Surprisingly this only just started becoming a problem recently:

2730s # libmutter-MESSAGE: Running Mutter Test (using mutter 42.9) as a Wayland display server
2730s libmutter-Message: 13:24:23.050: Running Mutter Test (using mutter 42.9) as a Wayland display server
2730s Bail out! libmutter-FATAL-WARNING: Failed to open gpu '/dev/dri/card0': Failed to open device '/dev/dri/renderD128': Permission denied
2730s
2730s (/usr/libexec/installed-tests/mutter-10/mutter-test-runner:6015): libmutter-WARNING **: 13:24:23.139: Failed to open gpu '/dev/dri/card0': Failed to open device '/dev/dri/renderD128': Permission denied

https://autopkgtest.ubuntu.com/results/autopkgtest-jammy/jammy/arm64/m/mutter/20240604_132730_8ae4b@/log.gz
https://autopkgtest.ubuntu.com/results/autopkgtest-jammy/jammy/arm64/m/mutter/20240604_160842_abf03@/log.gz

I can also reproduce it on amd64 using a second user account that doesn't have access to /dev/dri/*

Previous successful builds look like they worked only because there was no GPU to fail to open(?)

[Brian Murray (brian-murray)]

I also had a look at these regressions and noticed that they seem to be happening on instances in bos03 which is PS6 and has newer hardware than PS4.5. (We recently completed the transition to PS6.)

I opened a bug 2068053 about for this for my team to investigate it some more.

[Daniel van Vugt (vanvugt)]

I think Mutter needs fixing here more than changing the hardware config again to work around it. We can also expect more reliable test results by using a virtual GPU in future.

[Daniel van Vugt (vanvugt)]

Fix committed in readiness for 42.9-0ubuntu9, but there's no need to actually release that right now.

https://salsa.debian.org/gnome-team/mutter/-/commit/9dc8a804dd75f72cecaf938551d8d16044c2b49b