Include call to delete_subnet from delete_network at DB level

Removes an extra lock in bsn plugin that causes a deadlock
when delete_subnet is invoked form delete_network, agreed
with kevinbenton to remove it
Modifies a unit test to cover this change per reviewer request
Co-author amirosh

Closes-bug: #1197176

Change-Id: Ie3414848a91cc737b16b79399ae19800545e533f

neutron/db/db_base_plugin_v2.py

@@ -954,8 +954,10 @@ class NeutronDbPluginV2(neutron_plugin_base_v2.NeutronPluginBaseV2,
                 self._delete_port(context, port['id'])
 
             # clean up subnets
-            subnets_qry = context.session.query(models_v2.Subnet)
-            subnets_qry.filter_by(network_id=id).delete()
+            subnets = self._get_subnets_by_network(context, id)
+            for subnet in subnets:
+                self.delete_subnet(context, subnet['id'])
+
             context.session.delete(network)
 
     def get_network(self, context, id, fields=None):

neutron/plugins/bigswitch/plugin.py

@@ -863,8 +863,6 @@ class NeutronRestProxyV2(NeutronRestProxyV2Base,
             self._send_update_network(orig_net, context)
             return new_subnet
 
-    # NOTE(kevinbenton): workaround for eventlet/mysql deadlock
-    @utils.synchronized('bsn-port-barrier')
     @put_context_in_serverpool
     def delete_subnet(self, context, id):
         LOG.debug(_("NeutronRestProxyV2: delete_subnet() called"))

neutron/tests/unit/test_db_plugin.py

@@ -2648,10 +2648,14 @@ class TestSubnetsV2(NeutronDbPluginV2TestCase):
         res = self._create_network(fmt=self.fmt, name='net',
                                    admin_state_up=True)
         network = self.deserialize(self.fmt, res)
-        self._make_subnet(self.fmt, network, gateway_ip, cidr, ip_version=4)
+        subnet = self._make_subnet(self.fmt, network, gateway_ip, cidr,
+                                   ip_version=4)
         req = self.new_delete_request('networks', network['network']['id'])
         res = req.get_response(self.api)
         self.assertEqual(res.status_int, webob.exc.HTTPNoContent.code)
+        req = self.new_show_request('subnets', subnet['subnet']['id'])
+        res = req.get_response(self.api)
+        self.assertEqual(webob.exc.HTTPNotFound.code, res.status_int)
 
     def test_create_subnet_bad_tenant(self):
         with self.network() as network: