diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index a14650bf5fa47c..0004edf760701f 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -518,7 +518,9 @@ def flag_executor_shutting_down(self):
# to only have futures that are currently running.
new_pending_work_items = {}
for work_id, work_item in self.pending_work_items.items():
- if not work_item.future.cancel():
+ if work_item.future.cancel():
+ work_item.future.set_running_or_notify_cancel()
+ else:
new_pending_work_items[work_id] = work_item
self.pending_work_items = new_pending_work_items
# Drain work_ids_queue since we no longer need to
diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index 909359b648709f..bd8eb33d753598 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -264,6 +264,7 @@ def shutdown(self, wait=True, *, cancel_futures=False):
break
if work_item is not None:
work_item.future.cancel()
+ work_item.future.set_running_or_notify_cancel()
# Send a wake-up to prevent threads calling
# _work_queue.get(block=True) from permanently blocking.
diff --git a/Lib/test/test_concurrent_futures/executor.py b/Lib/test/test_concurrent_futures/executor.py
index 95bf8fcd25bf54..9a993fe32aa69a 100644
--- a/Lib/test/test_concurrent_futures/executor.py
+++ b/Lib/test/test_concurrent_futures/executor.py
@@ -233,3 +233,30 @@ def test_swallows_falsey_exceptions(self):
msg = 'lenlen'
with self.assertRaisesRegex(FalseyLenException, msg):
self.executor.submit(raiser, FalseyLenException, msg).result()
+
+ def test_shutdown_notifies_cancelled_futures(self):
+ # gh-136655: ensure cancelled futures are notified
+ count = self.worker_count * 2
+ barrier = self.create_barrier(self.worker_count + 1)
+ with self.executor as exec:
+ fs = [exec.submit(blocking_raiser,
+ barrier if index < self.worker_count else None)
+ for index in range(count)]
+
+ exec.shutdown(wait=False, cancel_futures=True)
+ try:
+ barrier.wait()
+ except threading.BrokenBarrierError:
+ pass
+
+ for future in fs:
+ self.assertRaises(
+ (FalseyBoolException, futures.CancelledError, threading.BrokenBarrierError),
+ future.result)
+
+ self.assertIn('CANCELLED_AND_NOTIFIED', [f._state for f in fs])
+
+def blocking_raiser(barrier=None):
+ if barrier is not None:
+ barrier.wait(1)
+ raise FalseyBoolException()
diff --git a/Lib/test/test_concurrent_futures/test_thread_pool.py b/Lib/test/test_concurrent_futures/test_thread_pool.py
index 4324241b374967..ab270a91670f10 100644
--- a/Lib/test/test_concurrent_futures/test_thread_pool.py
+++ b/Lib/test/test_concurrent_futures/test_thread_pool.py
@@ -112,6 +112,61 @@ def log_n_wait(ident):
# ident='third' is cancelled because it remained in the collection of futures
self.assertListEqual(log, ["ident='first' started", "ident='first' stopped"])
+ def test_shutdown_cancels_pending_futures(self):
+ # gh-109934: ensure shutdown cancels and notifies pending futures
+ def waiter(b1, b2):
+ b1.wait(3)
+ b2.wait(3)
+ def noop():
+ pass
+ b1 = threading.Barrier(2)
+ b2 = threading.Barrier(2)
+ called_back_1 = threading.Event()
+ called_back_2 = threading.Event()
+ with self.executor_type(max_workers=1) as pool:
+
+ # Submit two futures, the first of which will block and prevent the
+ # second from running
+ f1 = pool.submit(waiter, b1, b2)
+ f2 = pool.submit(noop)
+ f1.add_done_callback(lambda f: called_back_1.set())
+ f2.add_done_callback(lambda f: called_back_2.set())
+ fs = {f1, f2}
+
+ completed_iter = futures.as_completed(fs, timeout=0)
+ self.assertRaises(TimeoutError, next, completed_iter)
+
+ # Ensure the first task has started running then shutdown the
+ # pool, cancelling the unstarted task
+ b1.wait(3)
+ pool.shutdown(wait=False, cancel_futures=True)
+ self.assertTrue(f1.running())
+ self.assertTrue(f2.cancelled())
+ self.assertFalse(called_back_1.is_set())
+ self.assertTrue(called_back_2.is_set())
+
+ completed_iter = futures.as_completed(fs, timeout=0)
+ f = next(completed_iter)
+ self.assertIs(f, f2)
+ self.assertRaises(TimeoutError, next, completed_iter)
+
+ result = futures.wait(fs, timeout=0)
+ self.assertEqual(result.not_done, {f1})
+ self.assertEqual(result.done, {f2})
+
+ # Unblock and wait for the first future to complete
+ b2.wait(3)
+ called_back_1.wait(3)
+ self.assertTrue(f1.done())
+ self.assertTrue(called_back_1.is_set())
+
+ completed = set(futures.as_completed(fs, timeout=0))
+ self.assertEqual(set(fs), completed)
+
+ result = futures.wait(fs, timeout=0)
+ self.assertEqual(result.not_done, set())
+ self.assertEqual(result.done, set(fs))
+
def setUpModule():
setup_module()
diff --git a/Lib/test/test_concurrent_futures/util.py b/Lib/test/test_concurrent_futures/util.py
index b12940414d9142..aceb51cacfae26 100644
--- a/Lib/test/test_concurrent_futures/util.py
+++ b/Lib/test/test_concurrent_futures/util.py
@@ -79,6 +79,9 @@ def get_context(self):
class ThreadPoolMixin(ExecutorMixin):
executor_type = futures.ThreadPoolExecutor
+ def create_barrier(self, count):
+ return threading.Barrier(count)
+
def create_event(self):
return threading.Event()
@@ -87,6 +90,9 @@ def create_event(self):
class InterpreterPoolMixin(ExecutorMixin):
executor_type = futures.InterpreterPoolExecutor
+ def create_barrier(self, count):
+ self.skipTest("InterpreterPoolExecutor doesn't support barriers")
+
def create_event(self):
self.skipTest("InterpreterPoolExecutor doesn't support events")
@@ -106,6 +112,9 @@ def get_context(self):
self.skipTest("TSAN doesn't support threads after fork")
return super().get_context()
+ def create_barrier(self, count):
+ return self.manager.Barrier(count)
+
def create_event(self):
return self.manager.Event()
@@ -121,6 +130,9 @@ def get_context(self):
self.skipTest("ProcessPoolExecutor unavailable on this system")
return super().get_context()
+ def create_barrier(self, count):
+ return self.manager.Barrier(count)
+
def create_event(self):
return self.manager.Event()
@@ -140,6 +152,9 @@ def get_context(self):
self.skipTest("TSAN doesn't support threads after fork")
return super().get_context()
+ def create_barrier(self, count):
+ return self.manager.Barrier(count)
+
def create_event(self):
return self.manager.Event()
diff --git a/Misc/NEWS.d/next/Library/2025-05-24-15-15-43.gh-issue-109934.WXOdC8.rst b/Misc/NEWS.d/next/Library/2025-05-24-15-15-43.gh-issue-109934.WXOdC8.rst
new file mode 100644
index 00000000000000..21b097f9b72e13
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-24-15-15-43.gh-issue-109934.WXOdC8.rst
@@ -0,0 +1,3 @@
+Ensure :class:`concurrent.futures.ThreadPoolExecutor` and
+:class:`concurrent.futures.ProcessPoolExecutor` notifies any futures it cancels
+on shutdown.
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