Issue #14432: Remove the thread state field from the frame structure. Fix a

crash when a generator is created in a C thread that is destroyed while the
generator is still used. The issue was that a generator contains a frame, and
the frame kept a reference to the Python state of the destroyed C thread. The
crash occurs when a trace function is setup.

Include/frameobject.h

@@ -39,7 +39,6 @@ typedef struct _frame {
     /* Borrowed reference to a generator, or NULL */
     PyObject *f_gen;
 
-    PyThreadState *f_tstate;
     int f_lasti;                /* Last instruction if called */
     /* Call PyFrame_GetLineNumber() instead of reading this field
        directly.  As of 2.3 f_lineno is only valid when tracing is

Lib/test/test_sys.py

@@ -818,7 +818,7 @@ class SizeofTest(unittest.TestCase):
         nfrees = len(x.f_code.co_freevars)
         extras = x.f_code.co_stacksize + x.f_code.co_nlocals +\
                   ncells + nfrees - 1
-        check(x, vsize('13P3ic' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
+        check(x, vsize('12P3ic' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
         # function
         def func(): pass
         check(func, size('12P'))

Lib/test/test_threading.py

@@ -662,6 +662,44 @@ class ThreadTests(BaseTestCase):
         self.assertRegex(err.rstrip(),
                          b"^sys:1: ResourceWarning: unclosed file ")
 
+    def test_frame_tstate_tracing(self):
+        # Issue #14432: Crash when a generator is created in a C thread that is
+        # destroyed while the generator is still used. The issue was that a
+        # generator contains a frame, and the frame kept a reference to the
+        # Python state of the destroyed C thread. The crash occurs when a trace
+        # function is setup.
+
+        def noop_trace(frame, event, arg):
+            # no operation
+            return noop_trace
+
+        def generator():
+            while 1:
+                yield "genereator"
+
+        def callback():
+            if callback.gen is None:
+                callback.gen = generator()
+            return next(callback.gen)
+        callback.gen = None
+
+        old_trace = sys.gettrace()
+        sys.settrace(noop_trace)
+        try:
+            # Install a trace function
+            threading.settrace(noop_trace)
+
+            # Create a generator in a C thread which exits after the call
+            _testcapi.call_in_temporary_c_thread(callback)
+
+            # Call the generator in a different Python thread, check that the
+            # generator didn't keep a reference to the destroyed thread state
+            for test in range(3):
+                # The trace function is still called here
+                callback()
+        finally:
+            sys.settrace(old_trace)
+
 
 class ThreadJoinOnShutdown(BaseTestCase):
 

Misc/NEWS

@@ -10,6 +10,12 @@ Release date: 2014-01-05
 Core and Builtins
 -----------------
 
+- Issue #14432: Remove the thread state field from the frame structure. Fix a
+  crash when a generator is created in a C thread that is destroyed while the
+  generator is still used. The issue was that a generator contains a frame, and
+  the frame kept a reference to the Python state of the destroyed C thread. The
+  crash occurs when a trace function is setup.
+
 - Issue #19576: PyGILState_Ensure() now initializes threads. At startup, Python
   has no concrete GIL. If PyGILState_Ensure() is called from a new thread for
   the first time and PyEval_InitThreads() was not called yet, a GIL needs to be

Modules/_testcapimodule.c

@@ -2869,6 +2869,93 @@ PyDoc_STRVAR(docstring_with_signature_and_extra_newlines,
 "This docstring has a valid signature and some extra newlines."
 );
 
+typedef struct {
+    PyThread_type_lock start_event;
+    PyThread_type_lock exit_event;
+    PyObject *callback;
+} test_c_thread_t;
+
+static void
+temporary_c_thread(void *data)
+{
+    test_c_thread_t *test_c_thread = data;
+    PyGILState_STATE state;
+    PyObject *res;
+
+    PyThread_release_lock(test_c_thread->start_event);
+
+    /* Allocate a Python thread state for this thread */
+    state = PyGILState_Ensure();
+
+    res = PyObject_CallFunction(test_c_thread->callback, "", NULL);
+    Py_CLEAR(test_c_thread->callback);
+
+    if (res == NULL) {
+        PyErr_Print();
+    }
+    else {
+        Py_DECREF(res);
+    }
+
+    /* Destroy the Python thread state for this thread */
+    PyGILState_Release(state);
+
+    PyThread_release_lock(test_c_thread->exit_event);
+
+    PyThread_exit_thread();
+}
+
+static PyObject *
+call_in_temporary_c_thread(PyObject *self, PyObject *callback)
+{
+    PyObject *res = NULL;
+    test_c_thread_t test_c_thread;
+    long thread;
+
+    PyEval_InitThreads();
+
+    test_c_thread.start_event = PyThread_allocate_lock();
+    test_c_thread.exit_event = PyThread_allocate_lock();
+    test_c_thread.callback = NULL;
+    if (!test_c_thread.start_event || !test_c_thread.exit_event) {
+        PyErr_SetString(PyExc_RuntimeError, "could not allocate lock");
+        goto exit;
+    }
+
+    Py_INCREF(callback);
+    test_c_thread.callback = callback;
+
+    PyThread_acquire_lock(test_c_thread.start_event, 1);
+    PyThread_acquire_lock(test_c_thread.exit_event, 1);
+
+    thread = PyThread_start_new_thread(temporary_c_thread, &test_c_thread);
+    if (thread == -1) {
+        PyErr_SetString(PyExc_RuntimeError, "unable to start the thread");
+        PyThread_release_lock(test_c_thread.start_event);
+        PyThread_release_lock(test_c_thread.exit_event);
+        goto exit;
+    }
+
+    PyThread_acquire_lock(test_c_thread.start_event, 1);
+    PyThread_release_lock(test_c_thread.start_event);
+
+    Py_BEGIN_ALLOW_THREADS
+        PyThread_acquire_lock(test_c_thread.exit_event, 1);
+        PyThread_release_lock(test_c_thread.exit_event);
+    Py_END_ALLOW_THREADS
+
+    Py_INCREF(Py_None);
+    res = Py_None;
+
+exit:
+    Py_CLEAR(test_c_thread.callback);
+    if (test_c_thread.start_event)
+        PyThread_free_lock(test_c_thread.start_event);
+    if (test_c_thread.exit_event)
+        PyThread_free_lock(test_c_thread.exit_event);
+    return res;
+}
+
 static PyMethodDef TestMethods[] = {
     {"raise_exception",         raise_exception,                 METH_VARARGS},
     {"raise_memoryerror",   (PyCFunction)raise_memoryerror,  METH_NOARGS},
@@ -2997,6 +3084,8 @@ static PyMethodDef TestMethods[] = {
     {"docstring_with_signature_and_extra_newlines",
         (PyCFunction)test_with_docstring, METH_NOARGS,
         docstring_with_signature_and_extra_newlines},
+    {"call_in_temporary_c_thread", call_in_temporary_c_thread, METH_O,
+     PyDoc_STR("set_error_class(error_class) -> None")},
     {NULL, NULL} /* sentinel */
 };
 

Objects/frameobject.c

@@ -726,7 +726,6 @@ PyFrame_New(PyThreadState *tstate, PyCodeObject *code, PyObject *globals,
         Py_INCREF(locals);
         f->f_locals = locals;
     }
-    f->f_tstate = tstate;
 
     f->f_lasti = -1;
     f->f_lineno = code->co_firstlineno;

Python/sysmodule.c

@@ -367,7 +367,7 @@ trace_init(void)
 
 
 static PyObject *
-call_trampoline(PyThreadState *tstate, PyObject* callback,
+call_trampoline(PyObject* callback,
                 PyFrameObject *frame, int what, PyObject *arg)
 {
     PyObject *args;
@@ -405,12 +405,11 @@ static int
 profile_trampoline(PyObject *self, PyFrameObject *frame,
                    int what, PyObject *arg)
 {
-    PyThreadState *tstate = frame->f_tstate;
     PyObject *result;
 
     if (arg == NULL)
         arg = Py_None;
-    result = call_trampoline(tstate, self, frame, what, arg);
+    result = call_trampoline(self, frame, what, arg);
     if (result == NULL) {
         PyEval_SetProfile(NULL, NULL);
         return -1;
@@ -423,7 +422,6 @@ static int
 trace_trampoline(PyObject *self, PyFrameObject *frame,
                  int what, PyObject *arg)
 {
-    PyThreadState *tstate = frame->f_tstate;
     PyObject *callback;
     PyObject *result;
 
@@ -433,7 +431,7 @@ trace_trampoline(PyObject *self, PyFrameObject *frame,
         callback = frame->f_trace;
     if (callback == NULL)
         return 0;
-    result = call_trampoline(tstate, callback, frame, what, arg);
+    result = call_trampoline(callback, frame, what, arg);
     if (result == NULL) {
         PyEval_SetTrace(NULL, NULL);
         Py_XDECREF(frame->f_trace);