smp/cfd: Convert core to hotplug state machine

Install the callbacks via the state machine. They are installed at runtime so
smpcfd_prepare_cpu() needs to be invoked by the boot-CPU.

Signed-off-by: Richard Weinberger <richard@nod.at>
[ Added the dropped CPU dying case back in. ]
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Davidlohr Bueso <dave@stgolabs>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.818376366@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/cpu.c

@@ -1195,6 +1195,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
 		.startup = hrtimers_prepare_cpu,
 		.teardown = hrtimers_dead_cpu,
 	},
+	[CPUHP_SMPCFD_PREPARE] = {
+		.name = "SMPCFD prepare",
+		.startup = smpcfd_prepare_cpu,
+		.teardown = smpcfd_dead_cpu,
+	},
 	[CPUHP_TIMERS_DEAD] = {
 		.name = "timers dead",
 		.startup = NULL,
@@ -1218,6 +1223,10 @@ static struct cpuhp_step cpuhp_bp_states[] = {
 		.teardown		= NULL,
 		.cant_stop		= true,
 	},
+	[CPUHP_AP_SMPCFD_DYING] = {
+		.startup = NULL,
+		.teardown = smpcfd_dying_cpu,
+	},
 	/*
 	 * Handled on controll processor until the plugged processor manages
 	 * this itself.