x86/oprofile/nmi: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Robert Richter <rric@kernel.org>
Cc: oprofile-list@lists.sf.net
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-20-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/oprofile/nmi_int.c

@@ -339,10 +339,11 @@ fail:
 	return 0;
 }
 
-static void nmi_cpu_setup(void *dummy)
+static void nmi_cpu_setup(void)
 {
 	int cpu = smp_processor_id();
 	struct op_msrs *msrs = &per_cpu(cpu_msrs, cpu);
+
 	nmi_cpu_save_registers(msrs);
 	raw_spin_lock(&oprofilefs_lock);
 	model->setup_ctrs(model, msrs);
@@ -369,7 +370,7 @@ static void nmi_cpu_restore_registers(struct op_msrs *msrs)
 	}
 }
 
-static void nmi_cpu_shutdown(void *dummy)
+static void nmi_cpu_shutdown(void)
 {
 	unsigned int v;
 	int cpu = smp_processor_id();
@@ -387,24 +388,26 @@ static void nmi_cpu_shutdown(void *dummy)
 	nmi_cpu_restore_registers(msrs);
 }
 
-static void nmi_cpu_up(void)
+static int nmi_cpu_online(unsigned int cpu)
 {
 	local_irq_disable();
 	if (nmi_enabled)
-		nmi_cpu_setup(NULL);
+		nmi_cpu_setup();
 	if (ctr_running)
 		nmi_cpu_start(NULL);
 	local_irq_enable();
+	return 0;
 }
 
-static void nmi_cpu_down(void)
+static int nmi_cpu_down_prep(unsigned int cpu)
 {
 	local_irq_disable();
 	if (ctr_running)
 		nmi_cpu_stop(NULL);
 	if (nmi_enabled)
-		nmi_cpu_shutdown(NULL);
+		nmi_cpu_shutdown();
 	local_irq_enable();
+	return 0;
 }
 
 static int nmi_create_files(struct dentry *root)
@@ -437,24 +440,7 @@ static int nmi_create_files(struct dentry *root)
 	return 0;
 }
 
-static int oprofile_cpu_notifier(struct notifier_block *b, unsigned long action,
-				 void *data)
-{
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_DOWN_FAILED:
-	case CPU_ONLINE:
-		nmi_cpu_up();
-		break;
-	case CPU_DOWN_PREPARE:
-		nmi_cpu_down();
-		break;
-	}
-	return NOTIFY_DONE;
-}
-
-static struct notifier_block oprofile_cpu_nb = {
-	.notifier_call = oprofile_cpu_notifier
-};
+static enum cpuhp_state cpuhp_nmi_online;
 
 static int nmi_setup(void)
 {
@@ -497,20 +483,17 @@ static int nmi_setup(void)
 	if (err)
 		goto fail;
 
-	cpu_notifier_register_begin();
-
-	/* Use get/put_online_cpus() to protect 'nmi_enabled' */
-	get_online_cpus();
 	nmi_enabled = 1;
 	/* make nmi_enabled visible to the nmi handler: */
 	smp_mb();
-	on_each_cpu(nmi_cpu_setup, NULL, 1);
-	__register_cpu_notifier(&oprofile_cpu_nb);
-	put_online_cpus();
-
-	cpu_notifier_register_done();
-
+	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/oprofile:online",
+				nmi_cpu_online, nmi_cpu_down_prep);
+	if (err < 0)
+		goto fail_nmi;
+	cpuhp_nmi_online = err;
 	return 0;
+fail_nmi:
+	unregister_nmi_handler(NMI_LOCAL, "oprofile");
 fail:
 	free_msrs();
 	return err;
@@ -520,17 +503,9 @@ static void nmi_shutdown(void)
 {
 	struct op_msrs *msrs;
 
-	cpu_notifier_register_begin();
-
-	/* Use get/put_online_cpus() to protect 'nmi_enabled' & 'ctr_running' */
-	get_online_cpus();
-	on_each_cpu(nmi_cpu_shutdown, NULL, 1);
+	cpuhp_remove_state(cpuhp_nmi_online);
 	nmi_enabled = 0;
 	ctr_running = 0;
-	__unregister_cpu_notifier(&oprofile_cpu_nb);
-	put_online_cpus();
-
-	cpu_notifier_register_done();
 
 	/* make variables visible to the nmi handler: */
 	smp_mb();