From 58a5bc29020b7a8b3c2b2265034b26dbda0251be Mon Sep 17 00:00:00 2001 From: Timofey Ivankov Date: Fri, 11 Sep 2026 14:23:12 +0300 Subject: [PATCH 1/2] gh-157301: Fix asyncio event loop hanging on a failed eager task start --- Lib/asyncio/tasks.py | 11 +++- Lib/test/test_asyncio/test_tasks.py | 62 +++++++++++++++++++ ...-09-11-14-14-51.gh-issue-157301.QxcE2r.rst | 2 + Modules/_asynciomodule.c | 12 ++++ 4 files changed, 86 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Library/2026-09-11-14-14-51.gh-issue-157301.QxcE2r.rst diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py index f432cf0afa895a2..0a0c3f6e8f4e0f4 100644 --- a/Lib/asyncio/tasks.py +++ b/Lib/asyncio/tasks.py @@ -103,11 +103,20 @@ def __init__(self, coro, *, loop=None, name=None, context=None, self._coro = coro if context is None: self._context = contextvars.copy_context() + elif not isinstance(context, contextvars.Context): + # gh-157301: the passed value must be a contextvars.Context + self._log_destroy_pending = False + raise TypeError('a contextvars.Context was expected, ' + f'got {type(context).__name__}') else: self._context = context if eager_start and self._loop.is_running(): - self.__eager_start() + try: + self.__eager_start() + except BaseException: + self._log_destroy_pending = False + raise else: self._loop.call_soon(self.__step, context=self._context) _py_register_task(self) diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py index 9c111da8c27f162..9b59cb75b5effa9 100644 --- a/Lib/test/test_asyncio/test_tasks.py +++ b/Lib/test/test_asyncio/test_tasks.py @@ -2592,6 +2592,68 @@ async def main(): finally: loop.close() + def test_context_not_a_context(self): + # gh-157301 + async def coro(): + pass + + loop = asyncio.new_event_loop() + c = coro() + try: + with self.assertRaises(TypeError): + self.new_task(loop, c, context='not a context') + finally: + c.close() + loop.close() + + def test_context_not_a_context_leaves_loop_usable(self): + # gh-157301 + async def coro(): + pass + + async def main(): + c = coro() + try: + with self.assertRaises(TypeError): + self.new_task(loop, c, context='not a context', + eager_start=True) + finally: + c.close() + await asyncio.sleep(0) + + loop = asyncio.new_event_loop() + loop.call_later(support.SHORT_TIMEOUT, loop.stop) + try: + loop.run_until_complete(self.new_task(loop, main())) + finally: + loop.close() + + def test_context_already_entered_leaves_loop_usable(self): + # gh-157301 + async def coro(): + pass + + async def main(): + ctx = contextvars.copy_context() + + def inside(): + c = coro() + try: + with self.assertRaises(RuntimeError): + self.new_task(loop, c, context=ctx, eager_start=True) + finally: + c.close() + + ctx.run(inside) + await asyncio.sleep(0) + + loop = asyncio.new_event_loop() + loop.call_later(support.SHORT_TIMEOUT, loop.stop) + try: + loop.run_until_complete(self.new_task(loop, main())) + finally: + loop.close() + def test_context_2(self): cvar = contextvars.ContextVar('cvar', default='nope') diff --git a/Misc/NEWS.d/next/Library/2026-09-11-14-14-51.gh-issue-157301.QxcE2r.rst b/Misc/NEWS.d/next/Library/2026-09-11-14-14-51.gh-issue-157301.QxcE2r.rst new file mode 100644 index 000000000000000..9a1d2e435be9066 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-09-11-14-14-51.gh-issue-157301.QxcE2r.rst @@ -0,0 +1,2 @@ +Fix :class:`asyncio.Task` hanging the event loop when an eager start fails +to enter the task's context. diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c index a380f8ac72b32f4..687c4cebfe0d2f5 100644 --- a/Modules/_asynciomodule.c +++ b/Modules/_asynciomodule.c @@ -2312,6 +2312,13 @@ _asyncio_Task___init___impl(TaskObj *self, PyObject *coro, PyObject *loop, if (self->task_context == NULL) { return -1; } + } else if (!PyContext_CheckExact(context)) { + // gh-157301: the passed value must be a contextvars.Context + self->task_log_destroy_pending = 0; + PyErr_Format(PyExc_TypeError, + "a contextvars.Context was expected, got %T", + context); + return -1; } else { Py_XSETREF(self->task_context, Py_NewRef(context)); } @@ -3454,6 +3461,11 @@ task_eager_start(_PyThreadStateImpl *ts, asyncio_state *state, TaskObj *task) register_task(ts, task); if (_PyContext_Enter(&ts->base, task->task_context) == -1) { + // gh-157301: a failed enter must not leave the task current and registered + task->task_log_destroy_pending = 0; + PyObject *curtask = swap_current_task(ts, task->task_loop, prevtask); + Py_XDECREF(curtask); + unregister_task(task); Py_DECREF(prevtask); return -1; } From 8a3ceb5c015b0df370f7d66b3980afedf9c040e7 Mon Sep 17 00:00:00 2001 From: Timofey Ivankov Date: Fri, 11 Sep 2026 17:27:50 +0300 Subject: [PATCH 2/2] add assertion --- Modules/_asynciomodule.c | 1 + 1 file changed, 1 insertion(+) diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c index 687c4cebfe0d2f5..a368295585f8bea 100644 --- a/Modules/_asynciomodule.c +++ b/Modules/_asynciomodule.c @@ -3460,6 +3460,7 @@ task_eager_start(_PyThreadStateImpl *ts, asyncio_state *state, TaskObj *task) // it will continue as a regular (non-eager) asyncio task register_task(ts, task); + assert(PyContext_CheckExact(task->task_context)); if (_PyContext_Enter(&ts->base, task->task_context) == -1) { // gh-157301: a failed enter must not leave the task current and registered task->task_log_destroy_pending = 0;