A while back I was celebrating that arrival of secure realtime scheduling for the desktop. As it appears this was a bit premature then, since (mis-)using cgroups for this turned out to be more problematic and messy than I anticipated.
As a followup I'd now like to point you to this announcement I posted to LAD yesterday, introducing RealtimeKit which should fix the problem for good. It has now entered Rawhide becoming part of the default install (by means of being a dependency of PulseAudio), and I assume the other distros are going to adopt it pretty soon, too.