bpo-42350: Fix Thread._reset_internal_locks() (GH-23268)
Fix the threading.Thread class at fork: do nothing if the thread is
already stopped (ex: fork called at Python exit). Previously, an
error was logged in the child process.
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index db440d4..864cea3 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -469,6 +469,35 @@
t = threading.Thread(daemon=True)
self.assertTrue(t.daemon)
+ @unittest.skipUnless(hasattr(os, 'fork'), 'needs os.fork()')
+ def test_fork_at_exit(self):
+ # bpo-42350: Calling os.fork() after threading._shutdown() must
+ # not log an error.
+ code = textwrap.dedent("""
+ import atexit
+ import os
+ import sys
+ from test.support import wait_process
+
+ # Import the threading module to register its "at fork" callback
+ import threading
+
+ def exit_handler():
+ pid = os.fork()
+ if not pid:
+ print("child process ok", file=sys.stderr, flush=True)
+ # child process
+ sys.exit()
+ else:
+ wait_process(pid, exitcode=0)
+
+ # exit_handler() will be called after threading._shutdown()
+ atexit.register(exit_handler)
+ """)
+ _, out, err = assert_python_ok("-c", code)
+ self.assertEqual(out, b'')
+ self.assertEqual(err.rstrip(), b'child process ok')
+
@unittest.skipUnless(hasattr(os, 'fork'), 'test needs fork()')
def test_dummy_thread_after_fork(self):
# Issue #14308: a dummy thread in the active list doesn't mess up
diff --git a/Lib/threading.py b/Lib/threading.py
index 7dae77d..7b3d63d 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -844,8 +844,12 @@
# they may be in an invalid state leading to a deadlock or crash.
self._started._at_fork_reinit()
if is_alive:
- self._tstate_lock._at_fork_reinit()
- self._tstate_lock.acquire()
+ # bpo-42350: If the fork happens when the thread is already stopped
+ # (ex: after threading._shutdown() has been called), _tstate_lock
+ # is None. Do nothing in this case.
+ if self._tstate_lock is not None:
+ self._tstate_lock._at_fork_reinit()
+ self._tstate_lock.acquire()
else:
# The thread isn't alive after fork: it doesn't have a tstate
# anymore.
diff --git a/Misc/NEWS.d/next/Library/2020-11-13-18-53-50.bpo-42350.rsql7V.rst b/Misc/NEWS.d/next/Library/2020-11-13-18-53-50.bpo-42350.rsql7V.rst
new file mode 100644
index 0000000..090ea22
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-11-13-18-53-50.bpo-42350.rsql7V.rst
@@ -0,0 +1,3 @@
+Fix the :class:`threading.Thread` class at fork: do nothing if the thread is
+already stopped (ex: fork called at Python exit). Previously, an error was
+logged in the child process.