storage: Don't leave thread stranded on error

Move thread callback outside the StorageVolume class, so we are
forced to explicitly pass in every bit it may act on. Ensure we
always cancel and clean up the thread

virtinst/storage.py

@@ -419,6 +419,31 @@ class StoragePool(_StorageObject):
         return pool
 
 
+def _progress_thread(volname, pool, meter, event):
+    vol = None
+    if not meter:
+        return
+
+    while True:
+        try:
+            if not vol:
+                vol = pool.storageVolLookupByName(volname)
+            vol.info()  # pragma: no cover
+            break  # pragma: no cover
+        except Exception:
+            if event.wait(.2):
+                break
+
+    if vol is None:
+        log.debug("Couldn't lookup storage volume in prog thread.")
+        return
+
+    while True:  # pragma: no cover
+        ignore, ignore, alloc = vol.info()
+        meter.update(alloc)
+        if event.wait(1):
+            break
+
 
 class StorageVolume(_StorageObject):
     """
@@ -479,8 +504,6 @@ class StorageVolume(_StorageObject):
         self._pool_xml = None
         self._reflink = False
 
-        self._install_finished = threading.Event()
-
 
     ######################
     # Non XML properties #
@@ -642,13 +665,6 @@ class StorageVolume(_StorageObject):
         log.debug("Creating storage volume '%s' with xml:\n%s",
                       self.name, xml)
 
-        t = threading.Thread(target=self._progress_thread,
-                             name="Checking storage allocation",
-                             args=(meter,))
-        t.setDaemon(True)
-
-        meter = progress.ensure_meter(meter)
-
         cloneflags = 0
         createflags = 0
         if (self.format == "qcow2" and
@@ -664,8 +680,14 @@ class StorageVolume(_StorageObject):
             cloneflags |= getattr(libvirt,
                 "VIR_STORAGE_VOL_CREATE_REFLINK", 1)
 
+        event = threading.Event()
+        meter = progress.ensure_meter(meter)
+        t = threading.Thread(target=_progress_thread,
+                             name="Checking storage allocation",
+                             args=(self.name, self.pool, meter, event))
+        t.setDaemon(True)
+
         try:
-            self._install_finished.clear()
             t.start()
             meter.start(size=self.capacity,
                         text=_("Allocating '%s'") % self.name)
@@ -681,8 +703,6 @@ class StorageVolume(_StorageObject):
                 log.debug("Using vol create flags=%s", createflags)
                 vol = self.pool.createXML(xml, createflags)
 
-            self._install_finished.set()
-            t.join()
             meter.end(self.capacity)
             log.debug("Storage volume '%s' install complete.", self.name)
             return vol
@@ -690,32 +710,9 @@ class StorageVolume(_StorageObject):
             log.debug("Error creating storage volume", exc_info=True)
             raise RuntimeError("Couldn't create storage volume "
                                "'%s': '%s'" % (self.name, str(e)))
-
-    def _progress_thread(self, meter):
-        vol = None
-        if not meter:
-            return
-
-        while True:
-            try:
-                if not vol:
-                    vol = self.pool.storageVolLookupByName(self.name)
-                vol.info()  # pragma: no cover
-                break  # pragma: no cover
-            except Exception:
-                if self._install_finished.wait(.2):
-                    break
-
-        if vol is None:
-            log.debug("Couldn't lookup storage volume in prog thread.")
-            return
-
-        while True:  # pragma: no cover
-            ignore, ignore, alloc = vol.info()
-            meter.update(alloc)
-            if self._install_finished.wait(1):
-                break
-
+        finally:
+            event.set()
+            t.join()
 
     def is_size_conflict(self):
         """