process reading battery status hangs

http://bugzilla.kernel.org/show_bug.cgi?id=8351

Signed-off-by: Vladimir Lebedev <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>

drivers/acpi/battery.c

···
 	case ACPI_BATTERY_NOTIFY_INFO:
 	case ACPI_NOTIFY_BUS_CHECK:
 	case ACPI_NOTIFY_DEVICE_CHECK:
-		acpi_battery_mutex_lock(battery);
 		device = battery->device;
 		acpi_battery_notify_update(battery);
-		acpi_battery_mutex_unlock(battery);
 		acpi_bus_generate_event(device, event,
 					acpi_battery_present(battery));
 		break;