[pulseaudio-discuss] multiple users (gnome's switch user) on Ubuntu

Colin Guthrie gmane at colin.guthr.ie
Wed Apr 14 04:33:21 PDT 2010

'Twas brillig, and Brian J. Murrell at 14/04/10 12:11 did gyre and gimble:
> Colin Guthrie <gmane <at> colin.guthr.ie> writes:
>> I suspect you could be getting tripped up by a bug.
>> http://pulseaudio.org/ticket/773
> Oh, yes, that might be it.
>> On the first seat, do you have networking enabled?
> Yes.
>> If so, when the
>> second user's PA tries to start, one of the "default" things is tries
>> before launching a daemon of it's own is to try and connect via the
>> network. This connection is allowed but the authentication part fails
>> (because User 2 is not allowed to access User 1's PA daemon - which is
>> correct).
> Even if the first user has "Don't require authentication"?

Well in that case a rather confusing situation occurs:

 1. A login dialog pops up to allow the new user to login.
 2. The user currently logged in becomes "inactive" (see
ck-list-sessions output) and thus has their right to use the audio
devices (and various other things revoked - this is all outwith PA, but
PA will notice the change and automatically "suspend" access to the
devices in question effectively "corking" (a kind of forced pause) any
application which is currently or subsequently tries to write sound to
 3. The second user logs in and *does* connect to the first user's PA,
but sadly cannot actually use the h/w there in as that users right to
use the devices is still suspended!

Ironically, if you login as the second user and try to play something,
the app should just kinda lock up due to this forced suspend. When you
hot switch back to the first user, the now suspended user's audio
application finds that the devices have come back and now *can* play at
precicely the time they shouldn't! It's a bit messy in practice, but it
actually highlights all the various low level compoenents (dbus, udev,
consolekit) behaving as they should and it's really just due to the
borked connection logic in PA that this happens.

But as Lennart said on the bug above, this is fixed in master now :)

>> HTHs
> I am sure it does.  Thanx!

No problem.




Colin Guthrie

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