Bug#1099628: lightdm: alsa audio blocked by lightdm ipc semaphore
Package: lightdm
Version: 1.32.0-6+b1
Severity: normal
X-Debbugs-Cc: 10dmar10@gmail.com
Hello,
the issue is blocked alsa audio on login to desktop,
audio playback attempts of various programs fail with error messages:
* "unable to create IPC semaphore" and
* "ALSA: Couldn't open audio device: Permission denied"
example: aplay /usr/share/sounds/alsa/Noise.wav
ALSA lib pcm_direct.c:2178:(_snd_pcm_direct_new) unable to create IPC semaphore
aplay: main:850: audio open error: Permission denied
the problem appeared on 04.03.2024,
probably on first system boot after "aptitude safe-upgrade" from previous day.
I noticed lightdm is using alsa ipc key:
cat /usr/share/alsa/alsa.conf | grep ipc_
defaults.pcm.ipc_key 5678293
defaults.pcm.ipc_gid audio
defaults.pcm.ipc_perm 0660
note: 5678293 == 0x0056a4d5
==
== ipcs before login to desktop
==
------ Message Queues --------
key msqid owner perms used-bytes messages
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x0056a4d5 0 lightdm 660 488 1
0x0056a4d6 1 lightdm 660 131072 1
0x00000000 5 lightdm 600 524288 2 dest
------ Semaphore Arrays --------
key semid owner perms nsems
0x0056a4d5 0 lightdm 660 1
==
== ipcs when logged in to desktop, audio playback is blocked
==
------ Message Queues --------
key msqid owner perms used-bytes messages
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x0056a4d5 0 lightdm 660 488 0
0x0056a4d6 1 lightdm 660 131072 0
0x00000000 6 wwa 600 393216 2 dest
0x00000000 9 wwa 600 524288 2 dest
0x00000000 12 wwa 600 393216 2 dest
------ Semaphore Arrays --------
key semid owner perms nsems
0x0056a4d5 0 lightdm 660 1
==
== workaround:
==
executing speaker-test (on any other program playing audio) as root
solves the problem until user's logout back to lightdm.
==
== ipcs after running speaker-test once as root, alsa audio works again for normal user
==
------ Message Queues --------
key msqid owner perms used-bytes messages
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 6 wwa 600 393216 2 dest
0x00000000 9 wwa 600 524288 2 dest
0x00000000 12 wwa 600 393216 2 dest
------ Semaphore Arrays --------
key semid owner perms nsems
-- System Information:
Debian Release: trixie/sid
APT prefers testing
APT policy: (990, 'testing')
Architecture: amd64 (x86_64)
Kernel: Linux 6.12.13-wwa (SMP w/4 CPU threads; PREEMPT)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages lightdm depends on:
ii adduser 3.137
ii dbus 1.16.2-1
ii debconf [debconf-2.0] 1.5.89
ii libaudit1 1:4.0.2-2+b2
ii libc6 2.40-7
ii libgcrypt20 1.11.0-7
ii libglib2.0-0t64 2.83.4-1
ii libpam-systemd [logind] 257.3-1
ii libpam0g 1.7.0-3
ii libxcb1 1.17.0-2+b1
ii libxdmcp6 1:1.1.5-1
ii lightdm-gtk-greeter [lightdm-greeter] 2.0.9-1
Versions of packages lightdm recommends:
ii xserver-xorg 1:7.7+24
Versions of packages lightdm suggests:
ii accountsservice 23.13.9-7
ii upower 1.90.7-1
ii xserver-xephyr 2:21.1.15-3
-- debconf information:
* shared/default-x-display-manager: lightdm
lightdm/daemon_name: /usr/sbin/lightdm
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