hiccup in cdio_paranoia

[mistepien]

Every few seconds there is a "pause", mpd becomes unresponsive and so on.
Both 0.20.11 and current git.
libc is musl, kernel is 4.13.12, architecture x86 (32bit),
libcdio-0.94, libcdioparanoia-10.2+0.94+2

maybe paranoia is too paranoid? maybe accuracy is not priority here?
cdrom is connected via usb.

[MaxKellermann]

What does "becomes unresponsive" mean? What does "pause" mean? Check the verbose log for relevant messages.

[mistepien]

"Pause" means "lack of music" without setting player state to pause according to protocol.
During such "pause" sderr is also paused, meanwhile normally there is

client: [2] process command "status"
client: [2] command returned 0
client: [2] process command "currentsong"
client: [2] command returned 0
client: [2] process command "playlistinfo "1437""
client: [2] command returned 0
client: [22] process command "status"

The only residue of "pause" lasting few seconds is

alsa_output: Underrun on ALSA device "hw:V102,0"

hw:V102,0 is my dac, and when files are played there no underruns.
dmesg says nothing. mpd 0.20.1 is solid like a rock in case of files.

dac is connected via usb, too.

[MaxKellermann]

Even if the decoder thread stalls, the main thread which handles client commands should continue to run normally. A stall in the main thread is unusual. Please use strace -tttTp $(pidof mpd) -o /tmp/trace during such a hiccup and upload the output file. That can I hope I can see where the main thread stalls.
Of course, a stall in the decoder thread and xrun in the output thread is expected when the input is too slow.

[mistepien]

mpd can be striped or no? should it be compiled in some special way?

[MaxKellermann]

At this stage, stripped is ok. Use the same binary which you used to observe the problem.

[mistepien]

ok, this trace, I stopped strace when mpd "paused".
trace1.txt

[mistepien]

I changed bluray writer to old cd-rom. Pauses are now 1-2 seconds long every 15 seconds.

[MaxKellermann]

Thanks, that trace was very useful. I think I found the problem. Please test with branch unlock_cdio (https://github.com/MusicPlayerDaemon/MPD/tree/unlock_cdio)

[mistepien]

It works like a charm. Thanks a lot. No hiccups, even with bluray writer it works just great.

[MaxKellermann]

Yay! This was an obvious mistake with MPD's mutex locking inside various input plugins, including the plugin which reads static file (what nearly everybody uses). This change will improve MPD by a biiig margin!

[project-owner]

From which MPD version the fix is available? Thanks!

[iglosiggio]

I just want to thank you for this fix, i recently bought a laptop and the wakeups from the HDD made mpd hiccup a lot. Updating solved the problem (and i think this issue solved it all).