Exit ACPI processor module gracefully if acpi is disabled

diff -puN drivers/acpi/processor_core.c~exit-acpi-processor-module-gracefully-if-acpi-is-disabled drivers/acpi/processor_core.c
@@ -1030,6 +1030,8 @@ void acpi_processor_uninstall_hotplug_no
  * ACPI, but needs symbols from this driver
  */
 
+static int processor_driver_registered;
+
 static int __init acpi_processor_init(void)
 {
 	int result = 0;

@@ -1055,6 +1057,8 @@ static int __init acpi_processor_init(vo
 		return result;
 	}
 
+	processor_driver_registered = 1;
+
 	acpi_processor_install_hotplug_notify();
 
 	acpi_thermal_cpufreq_init();

@@ -1068,15 +1072,12 @@ static void __exit acpi_processor_exit(v
 {
 
 	acpi_processor_ppc_exit();
-
-	acpi_thermal_cpufreq_exit();
-
-	acpi_processor_uninstall_hotplug_notify();
-
-	acpi_bus_unregister_driver(&acpi_processor_driver);
-
-	remove_proc_entry(ACPI_PROCESSOR_CLASS, acpi_root_dir);
-
+	if (processor_driver_registered) {
+		acpi_thermal_cpufreq_exit();
+		acpi_processor_uninstall_hotplug_notify();
+		acpi_bus_unregister_driver(&acpi_processor_driver);
+		remove_proc_entry(ACPI_PROCESSOR_CLASS, acpi_root_dir);
+	}
 	return;
 }