[v4.2+ regression] fd7a4bed sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks

[Mike Galbraith <umgwanakikbuti@gmail.com>]

Hi Peter,

I bumped into an odd futextest regression, and finally bisected it to
$subject.  I haven't poked at it yet, chasing down and confirming the
little bugger munched the day.

#!/bin/sh

cd /home/git/futextest/functional
trap "killall -KILL -q cpuhog;exit;" INT

for i in `seq 0 7`; do taskset -c $i cpuhog& done
sleep 1
for i in `seq 1000`
do
	echo iteration $i
	./futex_requeue_pi -c -b -o -t 500000
done
killall cpuhog


Without the cpuhogs, it won't hang.

	-Mike