[pulseaudio-discuss] stream wedged in non-playing state

Pierre Ossman ossman at cendio.se
Mon May 16 15:37:40 UTC 2016

So I'm having some weird dynamic between two PulseAudio servers (using
module-tunnel-sink-new). The symptoms are that the downstream server
stops playing audio, but other clients for the upstream server work

(upstream here being the server closest to the actual audio hardware)

The bug is however very fickle and I only see it about once every two
weeks. However right now I'm able to semi-reliably produce it when
running Super Tux Kart inside ThinLinc, so I'm trying to use this
opportunity to debug it. Help is appreciated. :)

Let's call the upstream server A, and the downstream server B.

What I've discovered so far:

 a) The problem sometimes resolves itself after a few minutes. Perhaps
 it always resolves itself but the time varies, I haven't checked.

 b) Server B stops receiving requests for more data and believes the
 buffers are full.

 c) Server B still does periodic latency checks, and this is how the
 latency information looks from its point of view:

> Breakpoint 2, stream_get_timing_info_callback (pd=pd at entry=0x7f5ce40010a0, command=command at entry=2, tag=tag at entry=107, t=t at entry=0x7f5ce4010ba0, userdata=userdata at entry=0x7f5ce400e020) at pulse/stream.c:1952
> 1952	    o->stream->auto_timing_update_requested = false;
> (gdb) print *i
> $5 = {timestamp = {tv_sec = 1463411510, tv_usec = 297935}, synchronized_clocks = 1, sink_usec = 3026, source_usec = 0, transport_usec = 271, playing = 0, write_index_corrupt = 0, write_index = 1782548, 
>   read_index_corrupt = 0, read_index = 1782548, configured_sink_usec = 1451, configured_source_usec = 0, since_underrun = 12642188}

 Note that "playing" is false!

 d) I tried to gdb server A and see why it is stating that it is not
 playing. However gdb perturbed the system enough that the bug went
 away. :/

I've attached the debug output from server B around the time I started
the game and everything was supposed to un-suspend.


Pierre Ossman           Software Development
Cendio AB		https://cendio.com
Teknikringen 8		https://twitter.com/ThinLinc
583 30 Linköping	https://facebook.com/ThinLinc
Phone: +46-13-214600	https://plus.google.com/+CendioThinLinc

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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