Created attachment 274515 [details]
Screenshot showing how CPU is used and the dbus-daemon command line

This bug has been introduced in GNOME 3.12

Whenever I start rhythmbox, it takes around 1-2 minutes to start, in which both gnome-shell and rhythmbox are using 100% CPU.
(during those loading minutes rhythmbox is unresponsive and doesn't show any tracks)

dbus-daemon is using 50% CPU while rhythmbox loads and has been started automatically with the following command line:
/usr/bin/dbus-daemon --config-file0/etc/at-spi2/accessibility.conf --nofork --print-addres 3

Once rhythmbox has finished loading, it uses ~300 MB RAM instead of the usual 90 MB it used in GNOME 3.10

I noticed I had the same issue in 3.10 whenever I had an accessibility feature enabled, such as caribou.

I tried removing configuration files, dconf settings and rebuilding both gnome-shell and rhythmbox without success.

I'm using gnome packages from arch linux.

The screenshot attached displays the CPU usage while loading rhythmbox and the dbus-daemon command line.