Lock attach_volume

There are some issues with instance and volume cleanup when the volume
is not in a fully attached state so it will be safer to not attempt a
terminate_instance while there are attachments in progress.

Change-Id: I4347794e51004a881bf4ef5ee30f65ac28773e51
Closes-Bug: #1355348

nova/compute/manager.py

@@ -4290,11 +4290,16 @@ class ComputeManager(manager.Manager):
             bdm = objects.BlockDeviceMapping.get_by_volume_id(
                     context, volume_id)
         driver_bdm = driver_block_device.DriverVolumeBlockDevice(bdm)
-        try:
-            return self._attach_volume(context, instance, driver_bdm)
-        except Exception:
-            with excutils.save_and_reraise_exception():
-                bdm.destroy(context)
+
+        @utils.synchronized(instance.uuid)
+        def do_attach_volume(context, instance, driver_bdm):
+            try:
+                return self._attach_volume(context, instance, driver_bdm)
+            except Exception:
+                with excutils.save_and_reraise_exception():
+                    bdm.destroy(context)
+
+        do_attach_volume(context, instance, driver_bdm)
 
     def _attach_volume(self, context, instance, bdm):
         context = context.elevated()

nova/tests/compute/test_compute.py

@@ -4336,9 +4336,8 @@ class ComputeTestCase(BaseTestCase):
                        fake_attach_volume)
 
         # attach volume to instance
-        instance_p = obj_base.obj_to_primitive(instance)
         self.compute.attach_volume(self.context, volume['id'],
-                                   '/dev/vdc', instance_p, bdm=bdm)
+                                   '/dev/vdc', instance, bdm=bdm)
 
         # assert volume attached correctly
         self.assertEqual(volume['device_name'], '/dev/vdc')