https://github.com/python/cpython/commit/f2521324e6bdf331460abec7c2a88e2d3736b91c commit: f2521324e6bdf331460abec7c2a88e2d3736b91c branch: main author: Tobias Alex-Petersen <[email protected]> committer: kumaraditya303 <[email protected]> date: 2026-07-19T21:28:58+05:30 summary:
gh-119710: fix asyncio Process.wait() to finish on process exit and not wait for closing of pipes (#151983) Co-authored-by: Kumar Aditya <[email protected]> files: A Misc/NEWS.d/next/Library/2026-06-11-10-00-00.gh-issue-119710.Qz7Kp2.rst M Lib/asyncio/base_subprocess.py M Lib/test/test_asyncio/test_subprocess.py diff --git a/Lib/asyncio/base_subprocess.py b/Lib/asyncio/base_subprocess.py index 224b1883808a412..3fa1ed1afd2a651 100644 --- a/Lib/asyncio/base_subprocess.py +++ b/Lib/asyncio/base_subprocess.py @@ -26,7 +26,6 @@ def __init__(self, loop, protocol, args, shell, self._pending_calls = collections.deque() self._pipes = {} self._finished = False - self._pipes_connected = False if stdin == subprocess.PIPE: self._pipes[0] = None @@ -214,7 +213,6 @@ async def _connect_pipes(self, waiter): else: if waiter is not None and not waiter.cancelled(): waiter.set_result(None) - self._pipes_connected = True def _call(self, cb, *data): if self._pending_calls is not None: @@ -235,6 +233,7 @@ def _process_exited(self, returncode): if self._loop.get_debug(): logger.info('%r exited with return code %r', self, returncode) self._returncode = returncode + if self._proc.returncode is None: # asyncio uses a child watcher: copy the status into the Popen # object. On Python 3.6, it is required to avoid a ResourceWarning. @@ -243,6 +242,13 @@ def _process_exited(self, returncode): self._try_finish() + # gh-119710: Wake up futures waiting for wait() as soon as the process + # exits. + for waiter in self._exit_waiters: + if not waiter.done(): + waiter.set_result(returncode) + self._exit_waiters = None + async def _wait(self): """Wait until the process exit and return the process return code. @@ -258,15 +264,7 @@ def _try_finish(self): assert not self._finished if self._returncode is None: return - if not self._pipes_connected: - # self._pipes_connected can be False if not all pipes were connected - # because either the process failed to start or the self._connect_pipes task - # got cancelled. In this broken state we consider all pipes disconnected and - # to avoid hanging forever in self._wait as otherwise _exit_waiters - # would never be woken up, we wake them up here. - for waiter in self._exit_waiters: - if not waiter.done(): - waiter.set_result(self._returncode) + if all(p is not None and p.disconnected for p in self._pipes.values()): self._finished = True @@ -276,11 +274,6 @@ def _call_connection_lost(self, exc): try: self._protocol.connection_lost(exc) finally: - # wake up futures waiting for wait() - for waiter in self._exit_waiters: - if not waiter.done(): - waiter.set_result(self._returncode) - self._exit_waiters = None self._loop = None self._proc = None self._protocol = None diff --git a/Lib/test/test_asyncio/test_subprocess.py b/Lib/test/test_asyncio/test_subprocess.py index bb1a7d6ff22be8d..2e97fa5820f8245 100644 --- a/Lib/test/test_asyncio/test_subprocess.py +++ b/Lib/test/test_asyncio/test_subprocess.py @@ -112,37 +112,6 @@ def test_subprocess_repr(self): ) transport.close() - def test_proc_exited_no_invalid_state_error_on_exit_waiters(self): - # gh-145541: when _connect_pipes hasn't completed (so - # _pipes_connected is False) and the process exits, _try_finish() - # sets the result on exit waiters. Then _call_connection_lost() must - # not call set_result() again on the same waiters. - self.loop.set_exception_handler( - lambda loop, context: self.fail( - f"unexpected exception: {context}") - ) - waiter = self.loop.create_future() - transport, protocol = self.create_transport(waiter) - - # Simulate a waiter registered via _wait() before the process exits. - exit_waiter = self.loop.create_future() - transport._exit_waiters.append(exit_waiter) - - # _connect_pipes hasn't completed, so _pipes_connected is False. - self.assertFalse(transport._pipes_connected) - - # Simulate process exit. _try_finish() will set the result on - # exit_waiter because _pipes_connected is False, and then schedule - # _call_connection_lost() because _pipes is empty (vacuously all - # disconnected). _call_connection_lost() must skip exit_waiter - # because it's already done. - transport._process_exited(6) - self.loop.run_until_complete(waiter) - - self.assertEqual(exit_waiter.result(), 6) - - transport.close() - class SubprocessMixin: @@ -436,6 +405,46 @@ async def len_message(message): self.assertEqual(output.rstrip(), b'3') self.assertEqual(exitcode, 0) + def test_wait_even_if_pipe_is_open(self): + # gh-119710: Process.wait() must return once the process exits even + # if its stdout pipe is inherited by a grandchild that keeps it open, + # so the pipe never reaches EOF. Otherwise wait() hangs forever + # despite the returncode being known. + + async def run(): + # The grandchild inherits the child's stdin and stdout pipes and + # keeps both open after the child is killed. It writes "ready" + # so we know it has started, and exits once its stdin hits EOF. + code = textwrap.dedent("""\ + import subprocess, sys + subprocess.run([sys.executable, "-c", + "import sys; sys.stdout.write('ready');" + " sys.stdout.flush(); sys.stdin.read()"]) + """) + + proc = await asyncio.create_subprocess_exec( + sys.executable, "-c", code, + stdin=subprocess.PIPE, + stdout=subprocess.PIPE, + ) + try: + wait_proc = asyncio.create_task(proc.wait()) + # Wait until the grandchild holds the inherited pipes; this + # also lets the wait() task register its waiter. + await proc.stdout.readexactly(5) + proc.kill() + returncode = await asyncio.wait_for( + wait_proc, timeout=support.SHORT_TIMEOUT) + if sys.platform == 'win32': + self.assertIsInstance(returncode, int) + else: + self.assertEqual(-signal.SIGKILL, returncode) + finally: + proc.stdin.close() # let the grandchild exit + await proc.stdout.read() + + self.loop.run_until_complete(run()) + def test_empty_input(self): async def empty_input(): diff --git a/Misc/NEWS.d/next/Library/2026-06-11-10-00-00.gh-issue-119710.Qz7Kp2.rst b/Misc/NEWS.d/next/Library/2026-06-11-10-00-00.gh-issue-119710.Qz7Kp2.rst new file mode 100644 index 000000000000000..45f99d72ea29a2f --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-06-11-10-00-00.gh-issue-119710.Qz7Kp2.rst @@ -0,0 +1,4 @@ +Fix :mod:`asyncio` subprocess :meth:`~asyncio.subprocess.Process.wait` +hanging when the process has exited but one of its pipes is kept open by an +inherited child process (so the pipe never reaches EOF). ``wait()`` now +returns as soon as the process exits, regardless of the pipes' state. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
