The realtime preemption end game — for real this time

Work on realtime preemption for the Linux kernel got its start almost exactly 20 years ago
(though it had its roots in earlier work, of course). It is fair to say
that finishing that job has taken a bit longer than anybody involved would
have expected. Now, though, Sebastian Andrzej Siewior has posted a brief
patch series making it possible to enable realtime preemption in the
mainline kernel on three architectures.

With the printk bits merged, PREEMPT_RT could be enabled on X86,
ARM64 and Risc-V. These three architectures merged required changes
over the years leaving me in a position where I have no essential
changes in the queue that would affect them.

Congratulations are due to the many developers who have worked on this
project for the last two decades.