oprofile/x86: stop disabled counters in nmi handler

This patch adds checks to the nmi handler. Now samples are only
generated and counters reenabled, if the counters are running.
Otherwise the counters are stopped, if oprofile is using the nmi. In
other cases it will ignore the nmi notification.

Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Robert Richter <robert.richter@amd.com>

arch/x86/oprofile/nmi_int.c

@@ -62,12 +62,16 @@ static int profile_exceptions_notify(struct notifier_block *self,
 {
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
-	int cpu = smp_processor_id();
 
 	switch (val) {
 	case DIE_NMI:
 	case DIE_NMI_IPI:
-		model->check_ctrs(args->regs, &per_cpu(cpu_msrs, cpu));
+		if (ctr_running)
+			model->check_ctrs(args->regs, &__get_cpu_var(cpu_msrs));
+		else if (!nmi_enabled)
+			break;
+		else
+			model->stop(&__get_cpu_var(cpu_msrs));
 		ret = NOTIFY_STOP;
 		break;
 	default:
@@ -392,6 +396,9 @@ static int nmi_setup(void)
 		mux_clone(cpu);
 	}
 
+	nmi_enabled = 0;
+	ctr_running = 0;
+	barrier();
 	err = register_die_notifier(&profile_exceptions_nb);
 	if (err)
 		goto fail;
@@ -451,6 +458,7 @@ static void nmi_shutdown(void)
 	nmi_enabled = 0;
 	ctr_running = 0;
 	put_online_cpus();
+	barrier();
 	unregister_die_notifier(&profile_exceptions_nb);
 	msrs = &get_cpu_var(cpu_msrs);
 	model->shutdown(msrs);