bpo-40089: Add _at_fork_reinit() method to locks (GH-19195)
Add a private _at_fork_reinit() method to _thread.Lock,
_thread.RLock, threading.RLock and threading.Condition classes:
reinitialize the lock after fork in the child process; reset the lock
to the unlocked state.
Rename also the private _reset_internal_locks() method of
threading.Event to _at_fork_reinit().
* Add _PyThread_at_fork_reinit() private function. It is excluded
from the limited C API.
* threading.Thread._reset_internal_locks() now calls
_at_fork_reinit() on self._tstate_lock rather than creating a new
Python lock object.
diff --git a/Lib/test/lock_tests.py b/Lib/test/lock_tests.py
index cd1155d..b397525 100644
--- a/Lib/test/lock_tests.py
+++ b/Lib/test/lock_tests.py
@@ -2,6 +2,7 @@
Various tests for synchronization primitives.
"""
+import os
import sys
import time
from _thread import start_new_thread, TIMEOUT_MAX
@@ -12,6 +13,11 @@
from test import support
+requires_fork = unittest.skipUnless(hasattr(os, 'fork'),
+ "platform doesn't support fork "
+ "(no _at_fork_reinit method)")
+
+
def _wait():
# A crude wait/yield function not relying on synchronization primitives.
time.sleep(0.01)
@@ -265,6 +271,25 @@
self.assertFalse(lock.locked())
self.assertTrue(lock.acquire(blocking=False))
+ @requires_fork
+ def test_at_fork_reinit(self):
+ def use_lock(lock):
+ # make sure that the lock still works normally
+ # after _at_fork_reinit()
+ lock.acquire()
+ lock.release()
+
+ # unlocked
+ lock = self.locktype()
+ lock._at_fork_reinit()
+ use_lock(lock)
+
+ # locked: _at_fork_reinit() resets the lock to the unlocked state
+ lock2 = self.locktype()
+ lock2.acquire()
+ lock2._at_fork_reinit()
+ use_lock(lock2)
+
class RLockTests(BaseLockTests):
"""
@@ -417,12 +442,13 @@
b.wait_for_finished()
self.assertEqual(results, [True] * N)
- def test_reset_internal_locks(self):
+ @requires_fork
+ def test_at_fork_reinit(self):
# ensure that condition is still using a Lock after reset
evt = self.eventtype()
with evt._cond:
self.assertFalse(evt._cond.acquire(False))
- evt._reset_internal_locks()
+ evt._at_fork_reinit()
with evt._cond:
self.assertFalse(evt._cond.acquire(False))