I'm trying to use GStreamer 0.10.28 to play audio from a USB FM radio to the desktop sound card.  The FM radio provides a USB audio class interface supported by the ALSA snd-usb-audio driver.  I can use the following command to set up a pipeline to listen to the radio:

gst-launch-0.10 alsasrc device="plughw:1" \! audioconvert \! alsasink

Unfortunately, if the sound card is unplugged while such a pipeline is running, attempts to stop the pipeline will generate the following type of console message:

** (gst-launch-0.10:15447): CRITICAL **: Resources for ring buffer 0x16ec1b0 still acquired

If this is done from an application which remains running after the pipeline is stopped, it will be left with a thread spinning at 100% CPU.

It would appear that the ring buffer is not being released because the alsasrc plugin's gst_alsasrc_unprepare() function is returning failure.  This is apparently caused by ENODEV errors from snd_pcm_drop() and snd_pcm_hw_free(), which it may benefit from ignoring.

Secondarily, the task_monitor_alsa() task function is calling poll() on a file descriptor that has become bad, and poll() isn't waiting.  The task is not being shut down because the ring buffer release failed, and the task function contains no logic to throttle itself or shut itself down in this case, so it spins at 100% CPU.