From a986b061a3cd4661eb9f857e2936291f1847bd15 Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Thu, 3 Sep 2020 12:38:34 -0700 Subject: bpo-39010: Fix errors logged on proactor loop restart (GH-22017) (#22035) Stopping and restarting a proactor event loop on windows can lead to spurious errors logged (ConnectionResetError while reading from the self pipe). This fixes the issue by ensuring that we don't attempt to start multiple copies of the self-pipe reading loop. (cherry picked from commit ea5a6363c3f8cc90b7c0cc573922b10f296073b6) Co-authored-by: Ben Darnell Co-authored-by: Ben Darnell --- Lib/asyncio/proactor_events.py | 8 ++++++++ Lib/asyncio/windows_events.py | 8 ++++++-- Lib/test/test_asyncio/test_proactor_events.py | 1 + Lib/test/test_asyncio/test_windows_events.py | 20 ++++++++++++++++++++ .../Library/2020-08-30-10-24-26.bpo-39010._mzXJW.rst | 2 ++ 5 files changed, 37 insertions(+), 2 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2020-08-30-10-24-26.bpo-39010._mzXJW.rst diff --git a/Lib/asyncio/proactor_events.py b/Lib/asyncio/proactor_events.py index 830d8ed..54e4deb 100644 --- a/Lib/asyncio/proactor_events.py +++ b/Lib/asyncio/proactor_events.py @@ -766,6 +766,14 @@ class BaseProactorEventLoop(base_events.BaseEventLoop): try: if f is not None: f.result() # may raise + if self._self_reading_future is not f: + # When we scheduled this Future, we assigned it to + # _self_reading_future. If it's not there now, something has + # tried to cancel the loop while this callback was still in the + # queue (see windows_events.ProactorEventLoop.run_forever). In + # that case stop here instead of continuing to schedule a new + # iteration. + return f = self._proactor.recv(self._ssock, 4096) except exceptions.CancelledError: # _close_self_pipe() has been called, stop waiting for data diff --git a/Lib/asyncio/windows_events.py b/Lib/asyncio/windows_events.py index 12e87ab..a5ad6fc 100644 --- a/Lib/asyncio/windows_events.py +++ b/Lib/asyncio/windows_events.py @@ -318,8 +318,12 @@ class ProactorEventLoop(proactor_events.BaseProactorEventLoop): if self._self_reading_future is not None: ov = self._self_reading_future._ov self._self_reading_future.cancel() - # self_reading_future was just cancelled so it will never be signalled - # Unregister it otherwise IocpProactor.close will wait for it forever + # self_reading_future was just cancelled so if it hasn't been + # finished yet, it never will be (it's possible that it has + # already finished and its callback is waiting in the queue, + # where it could still happen if the event loop is restarted). + # Unregister it otherwise IocpProactor.close will wait for it + # forever if ov is not None: self._proactor._unregister(ov) self._self_reading_future = None diff --git a/Lib/test/test_asyncio/test_proactor_events.py b/Lib/test/test_asyncio/test_proactor_events.py index 007039a..e4809c3 100644 --- a/Lib/test/test_asyncio/test_proactor_events.py +++ b/Lib/test/test_asyncio/test_proactor_events.py @@ -736,6 +736,7 @@ class BaseProactorEventLoopTests(test_utils.TestCase): def test_loop_self_reading_fut(self): fut = mock.Mock() + self.loop._self_reading_future = fut self.loop._loop_self_reading(fut) self.assertTrue(fut.result.called) self.proactor.recv.assert_called_with(self.ssock, 4096) diff --git a/Lib/test/test_asyncio/test_windows_events.py b/Lib/test/test_asyncio/test_windows_events.py index 6b00570..33388a8 100644 --- a/Lib/test/test_asyncio/test_windows_events.py +++ b/Lib/test/test_asyncio/test_windows_events.py @@ -211,6 +211,26 @@ class ProactorTests(test_utils.TestCase): fut.cancel() fut.cancel() + def test_read_self_pipe_restart(self): + # Regression test for https://bugs.python.org/issue39010 + # Previously, restarting a proactor event loop in certain states + # would lead to spurious ConnectionResetErrors being logged. + self.loop.call_exception_handler = mock.Mock() + # Start an operation in another thread so that the self-pipe is used. + # This is theoretically timing-dependent (the task in the executor + # must complete before our start/stop cycles), but in practice it + # seems to work every time. + f = self.loop.run_in_executor(None, lambda: None) + self.loop.stop() + self.loop.run_forever() + self.loop.stop() + self.loop.run_forever() + # If we don't wait for f to complete here, we may get another + # warning logged about a thread that didn't shut down cleanly. + self.loop.run_until_complete(f) + self.loop.close() + self.assertFalse(self.loop.call_exception_handler.called) + class WinPolicyTests(test_utils.TestCase): diff --git a/Misc/NEWS.d/next/Library/2020-08-30-10-24-26.bpo-39010._mzXJW.rst b/Misc/NEWS.d/next/Library/2020-08-30-10-24-26.bpo-39010._mzXJW.rst new file mode 100644 index 0000000..0d9015b --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-08-30-10-24-26.bpo-39010._mzXJW.rst @@ -0,0 +1,2 @@ +Restarting a ``ProactorEventLoop`` on Windows no longer logs spurious +``ConnectionResetErrors``. -- cgit v0.12