diff --git a/Lib/asyncio/staggered.py b/Lib/asyncio/staggered.py index 845aed4c6a3b35..a1ba9d6e75fff5 100644 --- a/Lib/asyncio/staggered.py +++ b/Lib/asyncio/staggered.py @@ -90,11 +90,7 @@ def task_done(task): return unhandled_exceptions.append(exc) - async def run_one_coro(ok_to_start, previous_failed) -> None: - # in eager tasks this waits for the calling task to append this task - # to running_tasks, in regular tasks this wait is a no-op that does - # not yield a future. See gh-124309. - await ok_to_start.wait() + async def run_one_coro(previous_failed) -> None: # Wait for the previous task to finish, or for delay seconds if previous_failed is not None: with contextlib.suppress(exceptions_mod.TimeoutError): @@ -110,14 +106,13 @@ async def run_one_coro(ok_to_start, previous_failed) -> None: return # Start task that will run the next coroutine this_failed = locks.Event() - next_ok_to_start = locks.Event() - next_task = loop.create_task(run_one_coro(next_ok_to_start, this_failed)) + next_task = loop.create_task( + run_one_coro(this_failed), + eager_start=False, + ) futures.future_add_to_awaited_by(next_task, parent_task) running_tasks.add(next_task) next_task.add_done_callback(task_done) - # next_task has been appended to running_tasks so next_task is ok to - # start. - next_ok_to_start.set() # Prepare place to put this coroutine's exceptions if not won exceptions.append(None) assert len(exceptions) == this_index + 1 @@ -149,13 +144,11 @@ async def run_one_coro(ok_to_start, previous_failed) -> None: propagate_cancellation_error = None try: - ok_to_start = locks.Event() - first_task = loop.create_task(run_one_coro(ok_to_start, None)) + first_task = loop.create_task(run_one_coro(None), eager_start=False) futures.future_add_to_awaited_by(first_task, parent_task) running_tasks.add(first_task) first_task.add_done_callback(task_done) # first_task has been appended to running_tasks so first_task is ok to start. - ok_to_start.set() propagate_cancellation_error = None # Make sure no tasks are left running if we leave this function while running_tasks: diff --git a/Misc/NEWS.d/next/Library/2026-02-22-11-27-57.gh-issue-145107.ZlQXEZ.rst b/Misc/NEWS.d/next/Library/2026-02-22-11-27-57.gh-issue-145107.ZlQXEZ.rst new file mode 100644 index 00000000000000..affd886ef6a062 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-02-22-11-27-57.gh-issue-145107.ZlQXEZ.rst @@ -0,0 +1 @@ +simplify asyncio's ``staggered_race`` using ``eager_start=False``