[Python-checkins] cpython: Issue #18619: Fix atexit leaking callbacks registered from sub-interpreters,

Thu Aug 1 20:56:21 CEST 2013

http://hg.python.org/cpython/rev/71b63a32b1e3
changeset: 84953:71b63a32b1e3
user: Antoine Pitrou <solipsis at pitrou.net>
date: Thu Aug 01 20:56:12 2013 +0200
summary:
 Issue #18619: Fix atexit leaking callbacks registered from sub-interpreters, and make it GC-aware.
files:
 Lib/test/test_atexit.py | 42 +++++++++-
 Misc/NEWS | 3 +
 Modules/atexitmodule.c | 121 ++++++++++++++++++---------
 3 files changed, 122 insertions(+), 44 deletions(-)

diff --git a/Lib/test/test_atexit.py b/Lib/test/test_atexit.py
--- a/Lib/test/test_atexit.py
+++ b/Lib/test/test_atexit.py
@@ -2,6 +2,7 @@
 import unittest
 import io
 import atexit
+import _testcapi
 from test import support
 
 ### helpers
@@ -23,7 +24,9 @@
 def raise2():
 raise SystemError
 
-class TestCase(unittest.TestCase):
+
+class GeneralTest(unittest.TestCase):
+
 def setUp(self):
 self.save_stdout = sys.stdout
 self.save_stderr = sys.stderr
@@ -122,8 +125,43 @@
 self.assertEqual(l, [5])
 
 
+class SubinterpreterTest(unittest.TestCase):
+
+ def test_callbacks_leak(self):
+ # This test shows a leak in refleak mode if atexit doesn't
+ # take care to free callbacks in its per-subinterpreter module
+ # state.
+ n = atexit._ncallbacks()
+ code = r"""if 1:
+ import atexit
+ def f():
+ pass
+ atexit.register(f)
+ del atexit
+ """
+ ret = _testcapi.run_in_subinterp(code)
+ self.assertEqual(ret, 0)
+ self.assertEqual(atexit._ncallbacks(), n)
+
+ def test_callbacks_leak_refcycle(self):
+ # Similar to the above, but with a refcycle through the atexit
+ # module.
+ n = atexit._ncallbacks()
+ code = r"""if 1:
+ import atexit
+ def f():
+ pass
+ atexit.register(f)
+ atexit.__atexit = atexit
+ """
+ ret = _testcapi.run_in_subinterp(code)
+ self.assertEqual(ret, 0)
+ self.assertEqual(atexit._ncallbacks(), n)
+
+
 def test_main():
- support.run_unittest(TestCase)
+ support.run_unittest(__name__)
+
 
 if __name__ == "__main__":
 test_main()
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -179,6 +179,9 @@
 Library
 -------
 
+- Issue #18619: Fix atexit leaking callbacks registered from sub-interpreters,
+ and make it GC-aware.
+
 - Issue #15699: The readline module now uses PEP 3121-style module
 initialization, so as to reclaim allocated resources (Python callbacks)
 at shutdown. Original patch by Robin Schreiber.
diff --git a/Modules/atexitmodule.c b/Modules/atexitmodule.c
--- a/Modules/atexitmodule.c
+++ b/Modules/atexitmodule.c
@@ -10,8 +10,6 @@
 
 /* Forward declaration (for atexit_cleanup) */
 static PyObject *atexit_clear(PyObject*, PyObject*);
-/* Forward declaration (for atexit_callfuncs) */
-static void atexit_cleanup(PyObject*);
 /* Forward declaration of module object */
 static struct PyModuleDef atexitmodule;
 
@@ -33,6 +31,35 @@
 #define GET_ATEXIT_STATE(mod) ((atexitmodule_state*)PyModule_GetState(mod))
 
 
+static void
+atexit_delete_cb(atexitmodule_state *modstate, int i)
+{
+ atexit_callback *cb;
+
+ cb = modstate->atexit_callbacks[i];
+ modstate->atexit_callbacks[i] = NULL;
+ Py_DECREF(cb->func);
+ Py_DECREF(cb->args);
+ Py_XDECREF(cb->kwargs);
+ PyMem_Free(cb);
+}
+
+/* Clear all callbacks without calling them */
+static void
+atexit_cleanup(atexitmodule_state *modstate)
+{
+ atexit_callback *cb;
+ int i;
+ for (i = 0; i < modstate->ncallbacks; i++) {
+ cb = modstate->atexit_callbacks[i];
+ if (cb == NULL)
+ continue;
+
+ atexit_delete_cb(modstate, i);
+ }
+ modstate->ncallbacks = 0;
+}
+
 /* Installed into pythonrun.c's atexit mechanism */
 
 static void
@@ -78,34 +105,12 @@
 }
 }
 
- atexit_cleanup(module);
+ atexit_cleanup(modstate);
 
 if (exc_type)
 PyErr_Restore(exc_type, exc_value, exc_tb);
 }
 
-static void
-atexit_delete_cb(PyObject *self, int i)
-{
- atexitmodule_state *modstate;
- atexit_callback *cb;
-
- modstate = GET_ATEXIT_STATE(self);
- cb = modstate->atexit_callbacks[i];
- modstate->atexit_callbacks[i] = NULL;
- Py_DECREF(cb->func);
- Py_DECREF(cb->args);
- Py_XDECREF(cb->kwargs);
- PyMem_Free(cb);
-}
-
-static void
-atexit_cleanup(PyObject *self)
-{
- PyObject *r = atexit_clear(self, NULL);
- Py_DECREF(r);
-}
-
 /* ===================================================================== */
 /* Module methods. */
 
@@ -194,21 +199,50 @@
 static PyObject *
 atexit_clear(PyObject *self, PyObject *unused)
 {
+ atexit_cleanup(GET_ATEXIT_STATE(self));
+ Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(atexit_ncallbacks__doc__,
+"_ncallbacks() -> int\n\
+\n\
+Return the number of registered exit functions.");
+
+static PyObject *
+atexit_ncallbacks(PyObject *self, PyObject *unused)
+{
 atexitmodule_state *modstate;
- atexit_callback *cb;
- int i;
 
 modstate = GET_ATEXIT_STATE(self);
 
+ return PyLong_FromSsize_t(modstate->ncallbacks);
+}
+
+static int
+atexit_m_traverse(PyObject *self, visitproc visit, void *arg)
+{
+ int i;
+ atexitmodule_state *modstate;
+
+ modstate = GET_ATEXIT_STATE(self);
 for (i = 0; i < modstate->ncallbacks; i++) {
- cb = modstate->atexit_callbacks[i];
+ atexit_callback *cb = modstate->atexit_callbacks[i];
 if (cb == NULL)
 continue;
+ Py_VISIT(cb->func);
+ Py_VISIT(cb->args);
+ Py_VISIT(cb->kwargs);
+ }
+ return 0;
+}
 
- atexit_delete_cb(self, i);
- }
- modstate->ncallbacks = 0;
- Py_RETURN_NONE;
+static int
+atexit_m_clear(PyObject *self)
+{
+ atexitmodule_state *modstate;
+ modstate = GET_ATEXIT_STATE(self);
+ atexit_cleanup(modstate);
+ return 0;
 }
 
 static void
@@ -216,6 +250,7 @@
 {
 atexitmodule_state *modstate;
 modstate = GET_ATEXIT_STATE(m);
+ atexit_cleanup(modstate);
 PyMem_Free(modstate->atexit_callbacks);
 }
 
@@ -246,7 +281,7 @@
 if (eq < 0)
 return NULL;
 if (eq)
- atexit_delete_cb(self, i);
+ atexit_delete_cb(modstate, i);
 }
 Py_RETURN_NONE;
 }
@@ -260,6 +295,8 @@
 atexit_unregister__doc__},
 {"_run_exitfuncs", (PyCFunction) atexit_run_exitfuncs, METH_NOARGS,
 atexit_run_exitfuncs__doc__},
+ {"_ncallbacks", (PyCFunction) atexit_ncallbacks, METH_NOARGS,
+ atexit_ncallbacks__doc__},
 {NULL, NULL} /* sentinel */
 };
 
@@ -275,15 +312,15 @@
 
 
 static struct PyModuleDef atexitmodule = {
-	PyModuleDef_HEAD_INIT,
-	"atexit",
-	atexit__doc__,
-	sizeof(atexitmodule_state),
-	atexit_methods,
-	NULL,
-	NULL,
-	NULL,
-	(freefunc)atexit_free
+ PyModuleDef_HEAD_INIT,
+ "atexit",
+ atexit__doc__,
+ sizeof(atexitmodule_state),
+ atexit_methods,
+ NULL,
+ atexit_m_traverse,
+ atexit_m_clear,
+ (freefunc)atexit_free
 };
 
 PyMODINIT_FUNC
-- 
Repository URL: http://hg.python.org/cpython
