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bpo-20526: Fix PyThreadState_Clear(): don't decref frame (GH-19120) 

PyThreadState.frame is a borrowed reference, not a strong reference:
PyThreadState_Clear() must not call Py_CLEAR(tstate->frame).

Remove test_threading.test_warnings_at_exit(): we cannot warranty
that the Python thread state of daemon threads is cleared in a
reliable way during Python shutdown.
This commit is contained in:
Victor Stinner 2020-03-24 16:32:26 +01:00 committed by GitHub
parent 472fc843ca
commit 5804f878e7
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4 changed files with 14 additions and 30 deletions
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1
Include/cpython/pystate.h
View File

@ -55,6 +55,7 @@ struct _ts {
struct _ts *next;
PyInterpreterState *interp;
/* Borrowed reference to the current frame (it can be NULL) */
struct _frame *frame;
int recursion_depth;
char overflowed; /* The stack has overflowed. Allow 50 more calls

28
Lib/test/test_threading.py
View File

@ -776,34 +776,6 @@ class ThreadTests(BaseTestCase):
""")
self.assertEqual(out.rstrip(), b"thread_dict.atexit = 'value'")
def test_warnings_at_exit(self):
# bpo-19466: try to call most destructors at Python shutdown before
# destroying Python thread states
filename = __file__
rc, out, err = assert_python_ok("-Wd", "-c", """if 1:
import time
import threading
from test import support
def open_sleep():
# a warning will be emitted when the open file will be
# destroyed (without being explicitly closed) while the daemon
# thread is destroyed
fileobj = open(%a, 'rb')
start_event.set()
time.sleep(support.LONG_TIMEOUT)
start_event = threading.Event()
thread = threading.Thread(target=open_sleep, daemon=True)
thread.start()
# wait until the thread started
start_event.wait()
""" % filename)
self.assertRegex(err.rstrip(),
b"^sys:1: ResourceWarning: unclosed file ")
class ThreadJoinOnShutdown(BaseTestCase):

3
Misc/NEWS.d/next/Core and Builtins/2020-03-23-18-08-34.bpo-20526.NHNZIv.rst Normal file
View File

@ -0,0 +1,3 @@
Fix :c:func:`PyThreadState_Clear()`. ``PyThreadState.frame`` is a borrowed
reference, not a strong reference: ``PyThreadState_Clear()`` must not call
``Py_CLEAR(tstate->frame)``.

12
Python/pystate.c
View File

@ -765,11 +765,19 @@ PyThreadState_Clear(PyThreadState *tstate)
{
int verbose = tstate->interp->config.verbose;
if (verbose && tstate->frame != NULL)
if (verbose && tstate->frame != NULL) {
/* bpo-20526: After the main thread calls
_PyRuntimeState_SetFinalizing() in Py_FinalizeEx(), threads must
exit when trying to take the GIL. If a thread exit in the middle of
_PyEval_EvalFrameDefault(), tstate->frame is not reset to its
previous value. It is more likely with daemon threads, but it can
happen with regular threads if threading._shutdown() fails
(ex: interrupted by CTRL+C). */
fprintf(stderr,
"PyThreadState_Clear: warning: thread still has a frame\n");
}
Py_CLEAR(tstate->frame);
/* Don't clear tstate->frame: it is a borrowed reference */
Py_CLEAR(tstate->dict);
Py_CLEAR(tstate->async_exc);