While testing a new build of glib2.0/experimental under
autopkgtest-virt-qemu, I saw this failure:

1670s TAP version 14
1670s # random seed: R02S01a856aad2bc451ecdbfd7538c168180
1670s 1..1
1670s # Start of memory-monitor-psi tests
1670s # GLib-DEBUG: g_set_user_dirs: Setting HOME to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/home
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CACHE_HOME to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/cache
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_DIRS to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/system-config1:/tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/system-config2
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_HOME to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/config
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_DIRS to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/system-data1:/tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/system-data2
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_HOME to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/data
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_STATE_HOME to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/state
1670s # GLib-DEBUG: g_set_user_dirs: Setting XDG_RUNTIME_DIR to /tmp/test_memory-monitor-psi_5P5ET3/memory-monitor-psi/receive-signal/.dirs/runtime
1670s # GLib-GIO-DEBUG: MEMORY_PRESSURE_WATCH is /sys/fs/cgroup/system.slice/system-autopkgtest.slice/autopkgtest@hvc1.service/memory.pressure
1670s # GLib-GIO-DEBUG: Error on opening /sys/fs/cgroup/system.slice/system-autopkgtest.slice/autopkgtest@hvc1.service/memory.pressure: Permission denied
1670s # GLib-GIO-DEBUG: PSI is not supported.
1670s **
1670s GLib-GIO:ERROR:../../../gio/tests/memory-monitor-psi.c:90:test_receive_signals: assertion failed (local_error == NULL): PSI is not supported. (g-io-error-quark, 15)
1670s not ok /memory-monitor-psi/receive-signal - GLib-GIO:ERROR:../../../gio/tests/memory-monitor-psi.c:90:test_receive_signals: assertion failed (local_error == NULL): PSI is not supported. (g-io-error-quark, 15)
1670s Bail out!

The same test succeeded under lxc.

Perhaps this is intermittent (a race condition?), or perhaps it doesn't
account for the possibility that we might be running in a cgroup owned
by root, as in fact we are on autopkgtest-virt-qemu.

    smcv

Control: clone -1 -2
Control: retitle -2 glib2.0: autopkgtest failure: glib/memory-monitor-psi.test on Salsa-CI
...

The same test fails on Salsa CI, but it fails differently:

1036s # Running test: glib/memory-monitor-psi-env-set.test
1036s TAP version 14
1036s # random seed: R02S89fda921ddab8ef6775ad859487d6bc5
1036s 1..5
1036s # Start of memory-monitor-psi-env-set tests
1036s # GLib-DEBUG: g_set_user_dirs: Setting HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/home
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CACHE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/cache
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/system-config1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/system-config2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/config
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/system-data1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/system-data2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/data
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_STATE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/state
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_RUNTIME_DIR to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/receive-signal/.dirs/runtime
1036s # GLib-GIO-DEBUG: MEMORY_PRESSURE_WATCH is /tmp/test_memory-monitor-psi-env-set_R4WYS3/cgroup
1036s # GLib-GIO-DEBUG: Create source for low memory level 0
1036s # GLib-GIO-DEBUG: Send low memory signal with warning level 0
1036s ok 1 /memory-monitor-psi-env-set/receive-signal
1036s # GLib-DEBUG: g_set_user_dirs: Setting HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/home
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CACHE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/cache
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/system-config1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/system-config2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/config
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/system-data1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/system-data2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/data
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_STATE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/state
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_RUNTIME_DIR to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-no-write/.dirs/runtime
1036s # GLib-DEBUG: setenv()/putenv() are not thread-safe and should not be used after threads are created
1036s # GLib-DEBUG: unsetenv() is not thread-safe and should not be used after threads are created
1036s # GLib-GIO-DEBUG: MEMORY_PRESSURE_WATCH is /tmp/test_memory-monitor-psi-env-set_R4WYS3/write-env-no-write
1036s # GLib-GIO-DEBUG: Create source for low memory level 0
1036s ok 2 /memory-monitor-psi-env-set/write-env-no-write
1036s # GLib-DEBUG: g_set_user_dirs: Setting HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/home
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CACHE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/cache
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/system-config1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/system-config2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/config
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/system-data1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/system-data2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/data
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_STATE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/state
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_RUNTIME_DIR to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env/.dirs/runtime
1036s # GLib-DEBUG: setenv()/putenv() are not thread-safe and should not be used after threads are created
1036s # GLib-DEBUG: setenv()/putenv() are not thread-safe and should not be used after threads are created
1036s # GLib-GIO-DEBUG: MEMORY_PRESSURE_WATCH is /tmp/test_memory-monitor-psi-env-set_R4WYS3/write-env
1036s # GLib-GIO-DEBUG: Create source for low memory level 0
1036s ok 3 /memory-monitor-psi-env-set/write-env
1036s # GLib-DEBUG: g_set_user_dirs: Setting HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/home
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CACHE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/cache
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/system-config1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/system-config2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_CONFIG_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/config
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_DIRS to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/system-data1:/tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/system-data2
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_DATA_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/data
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_STATE_HOME to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/state
1036s # GLib-DEBUG: g_set_user_dirs: Setting XDG_RUNTIME_DIR to /tmp/test_memory-monitor-psi-env-set_R4WYS3/memory-monitor-psi-env-set/write-env-null/.dirs/runtime
1036s # GLib-DEBUG: setenv()/putenv() are not thread-safe and should not be used after threads are created
1036s # GLib-DEBUG: setenv()/putenv() are not thread-safe and should not be used after threads are created
1036s # GLib-GIO-DEBUG: MEMORY_PRESSURE_WATCH is /dev/null
1036s # GLib-GIO-DEBUG: Create source for low memory level 0
1036s # GLib-GIO-DEBUG: Send low memory signal with warning level 0
1036s **
1036s GLib-GIO:ERROR:../../../gio/tests/memory-monitor-psi-env-set.c:300:test_write_env_null: assertion failed (warning_level == -1): (50 == -1)
1036s not ok /memory-monitor-psi-env-set/write-env-null - GLib-GIO:ERROR:../../../gio/tests/memory-monitor-psi-env-set.c:300:test_write_env_null: assertion failed (warning_level == -1): (50 == -1)
1036s Bail out!
1036s # FAIL: glib/memory-monitor-psi-env-set.test (Child process killed by signal 6)
1036s not ok - glib/memory-monitor-psi-env-set.test

We should probably mark this particular test as flaky for the moment.
It's new test coverage for new features, so not a regression vs. forky.

     smcv