device: default can't be opened for playback (Device or resource busy)

[Andrew Schulman <andrex@alumni.utexas.net>]

I have a longstanding multiuser problem with aRts.  It happens to me often
that when another user on my host has been using an application that makes
sound, my sound won't work.  If I try to start an application (such as a
movie player) that makes sound, sometimes it will block or hang, and
sometimes it will start but not play movies, or will play movies but
without sound.  So I go to the Control Center to restart the sound server,
and when I try, an error dialog pops up with the following message:

Error while initializing the sound driver:
device: default can't be opened for playback (Device or resource busy)
The sound server will continue, using the null output device.

In the old days I used to be able to find out which application had grabbed
control of the sound device by running 'lsof /dev/dsp'.  That doesn't work
now with aRts, but I don't know what the corresponding device file or
command is.

I know that my other users are the source of the problem, because if I slay
them all then eventually I get my sound server back.  Sometimes I can get
it back by just killing other sound-using applications, but sometimes I
can't and have to slay the users.

All users have "Auto-suspend if idle" turned on and set to 3 seconds.

I'm using ALSA with kernel 2.6.10, a Turtle Beach Santa Cruz sound card
(cs46xx driver), and a bt878 video capture card.

Any help appreciated.
Thanks,
Andrew.