1 files changed, 33 insertions, 19 deletions

diff --git a/Python/import.c b/Python/import.c
index 26261e1..805cdd7 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) {
@@ -832,7 +846,7 @@ imp_fix_co_filename(PyObject *self, PyObject *args)
 
 
 /* Forward */
-static struct _frozen * find_frozen(PyObject *);
+static const struct _frozen * find_frozen(PyObject *);
 
 
 /* Helper to test for built-in module */
@@ -969,10 +983,10 @@ init_builtin(PyObject *name)
 
 /* Frozen modules */
 
-static struct _frozen *
+static const struct _frozen *
 find_frozen(PyObject *name)
 {
-    struct _frozen *p;
+    const struct _frozen *p;
 
     if (name == NULL)
         return NULL;
@@ -989,7 +1003,7 @@ find_frozen(PyObject *name)
 static PyObject *
 get_frozen_object(PyObject *name)
 {
-    struct _frozen *p = find_frozen(name);
+    const struct _frozen *p = find_frozen(name);
     int size;
 
     if (p == NULL) {
@@ -1013,7 +1027,7 @@ get_frozen_object(PyObject *name)
 static PyObject *
 is_frozen_package(PyObject *name)
 {
-    struct _frozen *p = find_frozen(name);
+    const struct _frozen *p = find_frozen(name);
     int size;
 
     if (p == NULL) {
@@ -1040,7 +1054,7 @@ is_frozen_package(PyObject *name)
 int
 PyImport_ImportFrozenModuleObject(PyObject *name)
 {
-    struct _frozen *p;
+    const struct _frozen *p;
     PyObject *co, *m, *path;
     int ispackage;
     int size;
@@ -1768,7 +1782,7 @@ static PyObject *
 imp_is_frozen(PyObject *self, PyObject *args)
 {
     PyObject *name;
-    struct _frozen *p;
+    const struct _frozen *p;
     if (!PyArg_ParseTuple(args, "U:is_frozen", &name))
         return NULL;
     p = find_frozen(name);