Audacious

Can you reinstall Audacious with debug symbols? The backtraces are not very useful otherwise.

I have already installed audacious and audacious-plugins built with debug symbols into /usr/local, but as I mentioned in the bug description, the version I built myself tends to freeze rather than crash and so doesn't produce a core dump or a backtrace. I've been able to view a frame stack in KDevelop a few times (it didn't look to me like anything easy to fix), but usually I just can't get anything at all out of a frozen Audacious process. If you can not reproduce this bug, I'll try to generate better backtraces.

I get a warning from the ALSA plugin, but no crash:

ERROR alsa.cc:255 [get_delay_locked]: snd_pcm_recover failed: File descriptor in bad state.

Fixed the ALSA warning:
https://github.com/audacious-media-player/audacious-plugins/commit/c1a594bcc335acd9eec286b3c65b8fecc91e3d20

It looks like you are using PulseAudio. Can you change the output plugin to ALSA and see if that makes the crash go away?

I also had similar warnings in terminal and non-blocking error messages in the UI. Had to experiment with the sleep delay to make Audacious crash or freeze.

I have tested flac files directly instead of cue files that reference them, but never got a freeze or a crash without a cue intermediary. The two cue files I have reproduced the crash with have 17 and 22 tracks, they reference flac files of size 375 and 245 MiB respectively. This bug is not likely to be specific to the two cue files, because I chose them at random from my collection, and both allowed me to reproduce the crash. But the underlying file format (flac), file size (more than 200 MiB) and the significant number of tracks could make a difference.

John Lindgren wrote:

Fixed the ALSA warning:
https://github.com/audacious-media-player/audacious-plugins/commit/c1a594bcc335acd9eec286b3c65b8fecc91e3d20

It looks like you are using PulseAudio. Can you change the output plugin to ALSA and see if that makes the crash go away?

In fact, Output plugin was set to "ALSA Output" in my Audacious settings. When I set it to "PulseAudio Output", I can't reproduce the crash.

Just got the following alsa warning while trying to reproduce the crash twice, then a freeze:

$ audacious
ERROR alsa.cc:255 [get_delay_locked]: snd_pcm_recover failed: Input/output error.
ERROR alsa.cc:255 [get_delay_locked]: snd_pcm_recover failed: Input/output error.
Killed

I'll test your commit now.

I pulled your commit, rebuilt and reinstalled audacious-plugins (but not audacious). Audacious still freezes with some sleep intervals and ALSA Output. Didn't get any alsa warnings after several attempts though.

It's almost certainly timing-related. You're hitting Audacious with a request to play a new track right at the end of the last one, as the audio buffer is draining. This is a transition state for the internals of the program, and some parts (e.g. decoding) are already done with the track while others are not. I made some changes in 4.0.x to make the UI more responsive in this state. A Git bisect would probably lead you to this commit¹, but the bug isn't necessarily in that commit itself; more likely, it exposed some underlying issues (like the one in the ALSA plugin that I just fixed).

Some backtraces with debug symbols would be very helpful. I would suggest simply taking the Arch Linux PKGBUILDs and rebuilding them with the "debug" option enabled (see the makepkg manpage²).

¹ https://github.com/audacious-media-player/audacious/commit/cd50db1079e0d0556c1bc5a700b91a9b27602a3c

² https://www.archlinux.org/pacman/makepkg.conf.5.html

Forgot to mention that I got the following output from crashing Audacious in terminal:

$ audacious -p
terminate called after throwing an instance of 'std::system_error'
  what():  No such process
Aborted (core dumped)

I am inclined to say that you have a libpthread, compiler, or CPU/firmware bug going on here. There are things in the backtraces that simply make no sense (std::terminate called when joining joinable() threads, deadlocks that are logically impossible, etc.)

I cannot help you further with this, sorry. It would take significant time, and access to the real hardware, to figure out what is really going on.

I have spent some time debugging the crash without success. Then switched to debugging the freeze and narrowed it down in no time. So I'm going to suspend debugging the crash until the freezing is fixed. There is hope that the fix will cover both issues. After all I can't reproduce the crash with PulseAudio output plugin. Perhaps this race condition corrupts pthread's private data, which then causes the crash. From man 3 pthread_join:

If multiple threads simultaneously try to join with the same thread, the results are undefined.

Aha, that's some very good detective work. Thank you. I'll need to put some thought into how to solve this.

See if this helps:

https://github.com/audacious-media-player/audacious-plugins/commit/0dac5d9a451700ffbbbd85427dc2d3661dc85bdb

I installed git master versions of audacious and audacious-plugins and tried to reproduce the crash or the freeze maybe 30-40 times with different sleep delays. None happened. Thanks for the complete fix.

However during my testing with sleep delay 0.1 two times the following error appeared in the UI and in audacious -p output:

ERROR alsa.cc:253 [get_delay_locked]: snd_pcm_recover failed: Input/output error.

Also, as used to happen during my earlier tests, there were the following string leak warnings in the output after I exited Audacious:

$ audacious -p
ERROR alsa.cc:253 [get_delay_locked]: snd_pcm_recover failed: Input/output error.
ERROR alsa.cc:253 [get_delay_locked]: snd_pcm_recover failed: Input/output error.
WARNING strpool.cc:181 [operator()]: String leaked: $PERFORMER - $TITLE - ${TRACK 01 TITLE}
WARNING strpool.cc:181 [operator()]: String leaked: $TITLE
WARNING strpool.cc:181 [operator()]: String leaked: ${PATH TO THE DIRECTORY CONTAINING THE CUE FILE}
WARNING strpool.cc:181 [operator()]: String leaked: Free Lossless Audio Codec (FLAC)
WARNING strpool.cc:181 [operator()]: String leaked: file://${URL-ENCODED ABSOLUTE PATH}.flac
WARNING strpool.cc:181 [operator()]: String leaked: $PERFORMER
WARNING strpool.cc:181 [operator()]: String leaked: $GENRE
WARNING strpool.cc:181 [operator()]: String leaked: ${TRACK 01 TITLE}
WARNING strpool.cc:181 [operator()]: String leaked: cue
WARNING strpool.cc:181 [operator()]: String leaked: lossless
WARNING strpool.cc:181 [operator()]: String leaked: file://${URL-ENCODED ABSOLUTE PATH}.cue?1
WARNING runtime.cc:364 [aud_leak_check]: Bytes allocated at exit: 7360

I replaced the actual strings with $VARIABLE, ${VARIABLE} as specified in the cue file that was in the tested bash -c "sleep 0.0005 && audacious -p -E '/home/path/to/some filename.cue'" command.
Note that these warnings happened often before, even in the absence of alsa errors.