Source: mutter
Version: 48.4-2
Severity: important
Tags: ftbfs unreproducible
User: [email protected]
Usertags: flaky

In one autopkgtest on ppc64el, https://ci.debian.net/packages/m/mutter/testing/ppc64el/62167381/ we can
see this failure:

634s # Running test: mutter-16/service-channel.test
636s # Executing: mutter-16/service-channel.test
638s # FAIL: mutter-16/service-channel.test (Child process exited with code 250)
638s not ok - mutter-16/service-channel.test

[... lots more results ...]

652s # SUMMARY: total=34; passed=31; skipped=0; failed=3; user=54.7s; system=14.5s; maxrss=1146276

[... 2 unrelated failures, out-of-scope here ...]

652s # FAIL: mutter-16/service-channel.test (Child process exited with code 250)

For further details of that failure we have to look in the $AUTOPKGTEST_ARTIFACTS (artifacts.tar.gz on ci.debian.net) and read artifacts/mutter-16_service-channel.test.txt, quoted in full here:

Setup HOME as /tmp/mutter-testroot-yaqls9wt/home
Setup TMPDIR as /tmp/mutter-testroot-yaqls9wt/tmpdir
Setup XDG_CACHE_HOME as /tmp/mutter-testroot-yaqls9wt/xdg_cache_home
Setup XDG_CONFIG_HOME as /tmp/mutter-testroot-yaqls9wt/xdg_config_home
Setup XDG_DATA_HOME as /tmp/mutter-testroot-yaqls9wt/xdg_data_home
Setup XDG_RUNTIME_DIR as /tmp/mutter-testroot-yaqls9wt/xdg_runtime_dir >Starting D-Bus daemons (session & system)...
Binding /tmp/mutter-testroot-yaqls9wt/xdg_runtime_dir/pipewire-0 for socket activation
Binding /tmp/mutter-testroot-yaqls9wt/xdg_runtime_dir/pipewire-0-manager for socket activation
Launching required services...
Starting mocked services...
ERROR:dbus.proxies:Introspect error on :1.1:/org/freedesktop/login1/session/dummy: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownObject: Unknown object '/org/freedesktop/login1/session/dummy'.
Running test case...
Process ['/usr/libexec/installed-tests/mutter-16/mutter-service-channel'] started with pid 8117
TAP version 14
# random seed: R02S38e0192555d7fd6babbdacaae03fd09f
# GLib-GIO-DEBUG: _g_io_module_get_default: Found default implementation memory (GMemorySettingsBackend) for ‘gsettings-backend’
# GLib-DEBUG: setenv()/putenv() are not thread-safe and should not be used after threads are created
# libmutter-MESSAGE: Running Mutter Test (using mutter 48.4) as a Wayland display server
# libmutter-MESSAGE: Created surfaceless renderer without GPU
# GLib-GIO-DEBUG: _g_io_module_get_default: Found default implementation local (GLocalVfs) for ‘gio-vfs’
# libmutter-DEBUG: WL: Unable to initialize wl_eglstream_controller.
# libmutter-MESSAGE: Using Wayland display name 'mutter-test-display'
# libmutter-MESSAGE: Added virtual monitor Meta-0
1..1
# Start of service-channel tests

** (process:8160): ERROR **: 09:17:15.887: Failed to open Wayland service connection: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Mutter.ServiceChannel was not provided by any .service files
# libmutter-INFO: Acquired name org.gnome.Mutter.InputMapping
# libmutter-DEBUG: Acquired name org.freedesktop.a11y.Manager
** >mutter-service-channel-test:ERROR:../src/tests/meta-wayland-test-utils.c:59:wayland_test_client_finished: 'g_subprocess_get_successful (wayland_test_client->subprocess)' should be TRUE
not ok /service-channel/wayland - mutter-service-channel-test:ERROR:../src/tests/meta-wayland-test-utils.c:59:wayland_test_client_finished: 'g_subprocess_get_successful (wayland_test_client->subprocess)' should be TRUE
Bail out!
Closing PipeWire socket...
Terminating services...

I suspect that this test may have started some background process that
ought to become the owner of org.gnome.Mutter.ServiceChannel, but then immediately proceeded with testing without waiting for the name to be
owned, leading to a race condition: if the owner of org.gnome.Mutter.ServiceChannel wins the race then the test passes, but
if the client wins the race then the test fails.

I only observed this in autopkgtest results, but it could in principle
affect build-time tests too, so I've added the ftbfs tag.

smcv

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