commit 03b0e8374b2ea93adf8fb6a48db2916f3b0388cc
author Serhiy Storchaka <storchaka@gmail.com> Thu Jul 06 08:38:24 2017 +0300
committer GitHub <noreply@github.com> Thu Jul 06 08:38:24 2017 +0300
tree 12743d6b43e1dff7f8bbacab2b6a5f0bb5a72141
parent aaa4f991518611d101fba1ef3ecb18d7b385ad5b

[3.6] bpo-30814: Fixed a race condition when import a submodule from a package. (GH-2580). (#2598)

(cherry picked from commit b4baacee1adc06edbe30ac7574d17a8cd168e2e0)

Python/import.c

diff --git a/Python/import.c b/Python/import.c
index a23a102..a9aa5b3 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1533,18 +1533,7 @@
     }
 
     mod = PyDict_GetItem(interp->modules, abs_name);
-    if (mod == Py_None) {
-        PyObject *msg = PyUnicode_FromFormat("import of %R halted; "
-                                             "None in sys.modules", abs_name);
-        if (msg != NULL) {
-            PyErr_SetImportErrorSubclass(PyExc_ModuleNotFoundError, msg,
-                    abs_name, NULL);
-            Py_DECREF(msg);
-        }
-        mod = NULL;
-        goto error;
-    }
-    else if (mod != NULL) {
+    if (mod != NULL && mod != Py_None) {
         _Py_IDENTIFIER(__spec__);
         _Py_IDENTIFIER(_initializing);
         _Py_IDENTIFIER(_lock_unlock_module);
@@ -1585,10 +1574,6 @@
         }
     }
     else {
-#ifdef WITH_THREAD
-        _PyImport_AcquireLock();
-#endif
-        /* _bootstrap._find_and_load() releases the import lock */
         mod = _PyObject_CallMethodIdObjArgs(interp->importlib,
                                             &PyId__find_and_load, abs_name,
                                             interp->import_func, NULL);