[$] The real realtime preemption end game

The addition of realtime support to Linux is a long story; it first shows up in LWN in 2004. For much of thattime, it has seemed like only a little more work was needed to get acrossthe finish line; thus we ran headlines like therealtime preemption endgame - in 2009. At the 2023 Linux Plumbers Conference, ThomasGleixner informed the group that, now, the end truly is near. There isreally only one big problem left to be solved before all of that work canland in the mainline.