Restarting desktop session services on RPM upgrade?

[John Dennis]

We've long had a way to restart system services on an RPM upgrade via
condrestart in the initscript. However, there is another kind of service
which runs, services bound to desktop sessions. Rather that global,
these are per user session.

Is there a mechanism by which an RPM which installs a desktop service
can perform the equivalent of a condrestart on the session service?

I imagine such a mechanism would work by iterating over every DBus
session bus, query for the existence of the service, if it exists send
it a stop signal and then after the service leaves the bus perform a
StartServiceByName within the session.

Do we have anything like that? I suspect not. If not then how can a root
process iterate over existing sessions? 
-- 
John Dennis <jdennis at redhat.com>