1 files changed, 26 insertions, 12 deletions

diff --git a/Python/import.c b/Python/import.c
index 5fc2523b268..a50ef05b07e 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -204,8 +204,11 @@ _PyImport_ReInitLock(void)
     if (import_lock_level > 1) {
         /* Forked as a side effect of import */
         long me = PyThread_get_thread_ident();
-        PyThread_acquire_lock(import_lock, 0);
-        /* XXX: can the previous line fail? */
+        /* The following could fail if the lock is already held, but forking as
+           a side-effect of an import is a) rare, b) nuts, and c) difficult to
+           do thanks to the lock only being held when doing individual module
+           locks per import. */
+        PyThread_acquire_lock(import_lock, NOWAIT_LOCK);
         import_lock_thread = me;
         import_lock_level--;
     } else {
@@ -451,12 +454,12 @@ PyImport_GetMagicTag(void)
 
 /* Magic for extension modules (built-in as well as dynamically
    loaded).  To prevent initializing an extension module more than
-   once, we keep a static dictionary 'extensions' keyed by module name
-   (for built-in modules) or by filename (for dynamically loaded
-   modules), containing these modules.  A copy of the module's
-   dictionary is stored by calling _PyImport_FixupExtensionObject()
-   immediately after the module initialization function succeeds.  A
-   copy can be retrieved from there by calling
+   once, we keep a static dictionary 'extensions' keyed by the tuple
+   (module name, module name)  (for built-in modules) or by
+   (filename, module name) (for dynamically loaded modules), containing these
+   modules.  A copy of the module's dictionary is stored by calling
+   _PyImport_FixupExtensionObject() immediately after the module initialization
+   function succeeds.  A copy can be retrieved from there by calling
    _PyImport_FindExtensionObject().
 
    Modules which do support multiple initialization set their m_size
@@ -469,8 +472,9 @@ int
 _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
                                PyObject *filename)
 {
-    PyObject *modules, *dict;
+    PyObject *modules, *dict, *key;
     struct PyModuleDef *def;
+    int res;
     if (extensions == NULL) {
         extensions = PyDict_New();
         if (extensions == NULL)
@@ -507,7 +511,13 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
         if (def->m_base.m_copy == NULL)
             return -1;
     }
-    PyDict_SetItem(extensions, filename, (PyObject*)def);
+    key = PyTuple_Pack(2, filename, name);
+    if (key == NULL)
+        return -1;
+    res = PyDict_SetItem(extensions, key, (PyObject *)def);
+    Py_DECREF(key);
+    if (res < 0)
+        return -1;
     return 0;
 }
 
@@ -527,11 +537,15 @@ _PyImport_FixupBuiltin(PyObject *mod, char *name)
 PyObject *
 _PyImport_FindExtensionObject(PyObject *name, PyObject *filename)
 {
-    PyObject *mod, *mdict;
+    PyObject *mod, *mdict, *key;
     PyModuleDef* def;
     if (extensions == NULL)
         return NULL;
-    def = (PyModuleDef*)PyDict_GetItem(extensions, filename);
+    key = PyTuple_Pack(2, filename, name);
+    if (key == NULL)
+        return NULL;
+    def = (PyModuleDef *)PyDict_GetItem(extensions, key);
+    Py_DECREF(key);
     if (def == NULL)
         return NULL;
     if (def->m_size == -1) {