Audacity freezes with padsp, unless pavucontrol is running

[smmalis37]

It's a strange one alright. When I open Audacity with padsp it works fine until I try to play anything. At that point it freezes beyond recovery. Looking online I found a 'pulseaudio application debug guide'. Following its instructions I ran pavucontrol before padsp audacity, and to my surprise Audacity worked perfectly! I was shocked! So i tried without pavucontrol running: freeze. Run pavucontrol again: plays perfectly. Needless to say, I'm very confused.

[lennart]

This is a deadlock if the same client ends up starting PA from two contexts. This has been fixed in PA 0.9.12.

(If you are experiencing this on 0.9.12 or have disabled autospawning, feel free to reopen)

[smmalis37]

I'm confused, how would I run PA from two different contexts? If PA is running, wouldn't padsp just run under that instance? And how does pavucontrol fix it?

P.S. I'm running pulseaudio 9.10 on Ubuntu

[lennart]

it's library contexts, not execution contexts.

So you say you are running PA 0.9.10 without autospawning? If that's the case than it is a different bug anyway.

Please provide a backtrace of the freeze. See http://pulseaudio.org/wiki/Community#PatchesBugsTranslations for some links how to do that.

[smmalis37]

I ran gdb following Ubuntu's instuctions, but nothing really came of it. Upon hitting play in Audacity I saw a lot of:

[New Thread 0xb4effb90 (LWP 6395)]
[Thread 0xb4effb90 (LWP 6395) exited]
[New Thread 0xb4effb90 (LWP 6396)]
[Thread 0xb4effb90 (LWP 6396) exited]
[New Thread 0xb4effb90 (LWP 6397)]
[Thread 0xb4effb90 (LWP 6397) exited]

Eventually these message froze as did Audacity. Gnome told me it was frozen and gave me an opportunity to force quit. I said yes. After that, gdb wouldn't give me any information.

(gdb) backtrace full
No stack.

[lennart]

You might ned to install debugging symbols first. No idea how that works on Ubuntu.

When Audacity freezes, press C-c in gdb. Then do the backtrace.

[smmalis37]

Debugging symbols were installed for everything (audacity & all pulseaudio packages). By C-c do you mean Control-c?

[lennart]

Yes C-c is <Control>+c.

I guess you haven't been raised with teachings in Emacs keybindings, have you? ;-)

[smmalis37]

Nope, I have almost no emacs experience. But that's besides the point. Here is what I did:

Reboot (to start fresh)
run 'padsp audacity'
open some music file
hit play

This causes the freeze. I attached gdb before hitting play, which produced the first log file. Hitting play froze it, so I hit Ctrl-C to stop gdb. I then restarted gdb, reattached it, and produced the second log file.

[lennart]

uh?

hmm, that doesn't make sense.

You should run audacity inside gdb all the time. Then pres C-c to get back to the gdb prompt when audacity freezes and do the bt

[smmalis37]

When I pressed C-c it ended gdb.

[lennart]

hmm, the second bt is actually fine.

[smmalis37]

This log might come in more handy. I ran padsp audacity and attached gdb to it. I caused the freeze and then hit Ctrl-Z on audacity (not gdb). Then the backtrace and everything else.

[lennart]

I am pretty sure I fixed this race condition now in r54afcf2 which will be part of 0.9.13. If it doesn't please reopen this bug report.

[smmalis37]

Running the PPA packages of 9.13 on intrepid beta now, problem still isn't fixed. BT coming shortly.

[smmalis37]

And now I can't get it to do it again. It was doing it non-stop before. I'm really confused now. My best guess is that it has something to do with pulseaudio releasing the audio devices if nothing is using them, then padsp has some kind of startup freeze. Just a guess, but it seems to fit whats going on (from my point of view). Sorry I can't be more helpful.

[lennart]

If you manage to reproduce it please reopen, otherwise I'll consider this one solved.

Maybe you used an incompletely upgraded system?