Issue #13502: threading: Fix a race condition in Event.wait() that made it
return False when the event was set and cleared right after.
diff --git a/Lib/test/lock_tests.py b/Lib/test/lock_tests.py
index 30148e6..094cc7a 100644
--- a/Lib/test/lock_tests.py
+++ b/Lib/test/lock_tests.py
@@ -351,6 +351,22 @@
for r, dt in results2:
self.assertTrue(r)
+ def test_set_and_clear(self):
+ # Issue #13502: check that wait() returns true even when the event is
+ # cleared before the waiting thread is woken up.
+ evt = self.eventtype()
+ results = []
+ N = 5
+ def f():
+ results.append(evt.wait(1))
+ b = Bunch(f, N)
+ b.wait_for_started()
+ time.sleep(0.5)
+ evt.set()
+ evt.clear()
+ b.wait_for_finished()
+ self.assertEqual(results, [True] * N)
+
class ConditionTests(BaseTestCase):
"""
diff --git a/Lib/threading.py b/Lib/threading.py
index 043e6c8..fe92f10 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -418,9 +418,10 @@
def wait(self, timeout=None):
self._cond.acquire()
try:
- if not self._flag:
- self._cond.wait(timeout)
- return self._flag
+ signaled = self._flag
+ if not signaled:
+ signaled = self._cond.wait(timeout)
+ return signaled
finally:
self._cond.release()