Bug 55701

PulseAudio 1.1 (tested with Fedora package pulseaudio-1.1-9.fc17.x86_64) crashes on every daemon shutdown in my configuration consisting of an module-alsa-sink (denoted as A) and two chained module-ladspa-sinks (L1, L2):

L2 -> L1 -> A

default sink = A

If module-rescue-streams is enabled, the following happens on daemon shutdown (even with PA completely idle and no clients connected):

1) A is being unloaded
2) module-rescue-streams kicks in and tries to find a new home for the output stream of L1
3) find_evacuation_sink() iterates over all sinks and finds L2 as a suitable candidate
4) module-rescue-streams thus moves L1's output (L1out) to L2, creating a cycle
5) pa_sink_process_msg() processes the PA_SINK_MESSAGE_FINISH_MOVE message and calls attach() on the pa_sink_input being moved (L1out). This points to sink_input_attach_cb() of module-ladspa-sink.c
6) sink_input_attach_cb(L1out) calls pa_sink_attach_within_thread(L1out->sink), where L1out->sink == L1
7) pa_sink_attach_within_thread(L2) iterates over L2's inputs and calls attach() on each of them, including L2out. Again, this means sink_input_attach_cb(L2out) is called.
8) sink_input_attach_cb(L2out) calls pa_sink_attach_within_thread(L2)
9) pa_sink_attach_within_thread(L2) calls attach() on L2's inputs: sink_input_attach_cb(L1out)
10) Go to 6) and repeat until the stack overflows and PA is killed by SEGV.

I'm not sure how to fix this properly since I have only limited understanding on the internals of PA. It would probably be an overkill for module-rescue-streams to do full cycle detection somehow. Possibly it would be best to just fix find_evacuation_sink() to ignore "filter-like" sinks if there's a way how to recognise them easily (ignoring just module-ladspa-sinks seems too hackish to me).