From c476410dc5ae62ffb5e32f64f9a3a622485c7d93 Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Fri, 7 Mar 2025 09:58:09 -0500 Subject: gh-110206: Fix multiprocessing test_notify_all (#130933) The test could deadlock trying join on the worker processes due to a combination of behaviors: * The use of `assertReachesEventually` did not ensure that workers actually woken.release() because the SyncManager's Semaphore does not implement get_value. * This mean that the test could finish and the variable "sleeping" would got out of scope and be collected. This unregisters the proxy leading to failures in the worker or possibly the manager. * The subsequent call to `p.join()` during cleanUp therefore never finished. This takes two approaches to fix this: 1) Use woken.acquire() to ensure that the workers actually finish calling woken.release() 2) At the end of the test, wait until the workers are finished, while `cond`, `sleeping`, and `woken` are still valid. --- Lib/test/_test_multiprocessing.py | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py index 67ab8f0..10c17b2 100644 --- a/Lib/test/_test_multiprocessing.py +++ b/Lib/test/_test_multiprocessing.py @@ -1694,18 +1694,19 @@ class _TestCondition(BaseTestCase): woken = self.Semaphore(0) # start some threads/processes which will timeout + workers = [] for i in range(3): p = self.Process(target=self.f, args=(cond, sleeping, woken, TIMEOUT1)) p.daemon = True p.start() - self.addCleanup(p.join) + workers.append(p) t = threading.Thread(target=self.f, args=(cond, sleeping, woken, TIMEOUT1)) t.daemon = True t.start() - self.addCleanup(t.join) + workers.append(t) # wait for them all to sleep for i in range(6): @@ -1724,12 +1725,12 @@ class _TestCondition(BaseTestCase): p = self.Process(target=self.f, args=(cond, sleeping, woken)) p.daemon = True p.start() - self.addCleanup(p.join) + workers.append(p) t = threading.Thread(target=self.f, args=(cond, sleeping, woken)) t.daemon = True t.start() - self.addCleanup(t.join) + workers.append(t) # wait for them to all sleep for i in range(6): @@ -1745,11 +1746,17 @@ class _TestCondition(BaseTestCase): cond.release() # check they have all woken - self.assertReachesEventually(lambda: get_value(woken), 6) + for i in range(6): + woken.acquire() + self.assertReturnsIfImplemented(0, get_value, woken) # check state is not mucked up self.check_invariant(cond) + for w in workers: + # NOTE: join_process and join_thread are the same + threading_helper.join_thread(w) + def test_notify_n(self): cond = self.Condition() sleeping = self.Semaphore(0) -- cgit v0.12