add functional repoducer for bug 2065927

Today if the write sys call to offline a cpu when
deleting an instnace fails due to an OSERROR or ValueERROR
the instance delete fails and the instance goes to error.

as reported in bug: #2065927 this can happen as a result of
OSError: [Errno 16] Device or resource busy if the vm is
deleted shortly after its started.

Related-Bug: #2065927
Change-Id: I1352a3a1e28cfe14ec8f32042ed35cb25e70338e
(cherry picked from commit ee581a5c9d)
(cherry picked from commit f1c46802b1)
(cherry picked from commit 254ea7bbfa)

nova/tests/functional/libvirt/test_power_manage.py

@@ -10,15 +10,16 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from unittest import mock
-
 import fixtures
 
+from unittest import mock
+
 from nova import context as nova_context
 from nova import exception
 from nova import objects
 from nova.tests import fixtures as nova_fixtures
 from nova.tests.fixtures import libvirt as fakelibvirt
+from nova.tests.functional.api import client
 from nova.tests.functional.libvirt import base
 from nova.virt import hardware
 from nova.virt.libvirt.cpu import api as cpu_api
@@ -240,7 +241,6 @@ class PowerManagementTests(PowerManagementTestsBase):
                                          cpu_cores=5, cpu_threads=2)
         self.compute1 = self.start_compute(host_info=self.host_info,
                                            hostname='compute1')
-
         # All cores are shutdown at startup, let's check.
         cpu_dedicated_set = hardware.get_cpu_dedicated_set()
         self._assert_cpu_set_state(cpu_dedicated_set, expected='offline')
@@ -266,6 +266,33 @@ class PowerManagementTests(PowerManagementTestsBase):
         cpu_dedicated_set = hardware.get_cpu_dedicated_set()
         unused_cpus = cpu_dedicated_set - instance_pcpus
         self._assert_cpu_set_state(unused_cpus, expected='offline')
+        return server
+
+    def test_delete_server(self):
+        server = self.test_create_server()
+        self._delete_server(server)
+        # Let's verify that the pinned CPUs are now offline
+        cpu_dedicated_set = hardware.get_cpu_dedicated_set()
+        self._assert_cpu_set_state(cpu_dedicated_set, expected='offline')
+
+    def test_delete_server_device_busy(self):
+        server = self.test_create_server()
+
+        inst = objects.Instance.get_by_uuid(self.ctxt, server['id'])
+        instance_pcpus = inst.numa_topology.cpu_pinning
+        self._assert_cpu_set_state(instance_pcpus, expected='online')
+        with mock.patch(
+            'nova.filesystem.write_sys',
+            side_effect=exception.FileNotFound(file_path='fake')):
+            # This is bug 2065927
+            self.assertRaises(
+                client.OpenStackApiException, self._delete_server, server)
+        cpu_dedicated_set = hardware.get_cpu_dedicated_set()
+        # Verify that the unused CPUs are still offline
+        unused_cpus = cpu_dedicated_set - instance_pcpus
+        self._assert_cpu_set_state(unused_cpus, expected='offline')
+        # but the instance cpus are still online
+        self._assert_cpu_set_state(instance_pcpus, expected='online')
 
     def test_create_server_with_emulator_threads_isolate(self):
         server = self._create_server(