oprofile/timer: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.
Since the online target runs always on the target CPU we can drop
smp_call_function_single(). The functions is invoked with interrupts off to
keep the old calling convention. If the maintainer things that this function
can be called with interrupts enabled then it can be removed :)

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Robert Richter <rric@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: oprofile-list@lists.sf.net
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160906170457.32393-10-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/oprofile/timer_int.c

@@ -74,37 +74,39 @@ static void oprofile_hrtimer_stop(void)
 	put_online_cpus();
 }
 
-static int oprofile_cpu_notify(struct notifier_block *self,
-			       unsigned long action, void *hcpu)
+static int oprofile_timer_online(unsigned int cpu)
 {
-	long cpu = (long) hcpu;
-
-	switch (action) {
-	case CPU_ONLINE:
-	case CPU_ONLINE_FROZEN:
-		smp_call_function_single(cpu, __oprofile_hrtimer_start,
-					 NULL, 1);
-		break;
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		__oprofile_hrtimer_stop(cpu);
-		break;
-	}
-	return NOTIFY_OK;
+	local_irq_disable();
+	__oprofile_hrtimer_start(NULL);
+	local_irq_enable();
+	return 0;
 }
 
-static struct notifier_block __refdata oprofile_cpu_notifier = {
-	.notifier_call = oprofile_cpu_notify,
-};
+static int oprofile_timer_prep_down(unsigned int cpu)
+{
+	__oprofile_hrtimer_stop(cpu);
+	return 0;
+}
+
+static enum cpuhp_state hp_online;
 
 static int oprofile_hrtimer_setup(void)
 {
-	return register_hotcpu_notifier(&oprofile_cpu_notifier);
+	int ret;
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					"oprofile/timer:online",
+					oprofile_timer_online,
+					oprofile_timer_prep_down);
+	if (ret < 0)
+		return ret;
+	hp_online = ret;
+	return 0;
 }
 
 static void oprofile_hrtimer_shutdown(void)
 {
-	unregister_hotcpu_notifier(&oprofile_cpu_notifier);
+	cpuhp_remove_state_nocalls(hp_online);
 }
 
 int oprofile_timer_init(struct oprofile_operations *ops)