Issue #28613: Fix get_event_loop() to return the current loop
when called from coroutines or callbacks.
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index 5597bcb..6488f23 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -393,7 +393,10 @@
"""Run until stop() is called."""
self._check_closed()
if self.is_running():
- raise RuntimeError('Event loop is running.')
+ raise RuntimeError('This event loop is already running')
+ if events._get_running_loop() is not None:
+ raise RuntimeError(
+ 'Cannot run the event loop while another loop is running')
self._set_coroutine_wrapper(self._debug)
self._thread_id = threading.get_ident()
if self._asyncgens is not None:
@@ -401,6 +404,7 @@
sys.set_asyncgen_hooks(firstiter=self._asyncgen_firstiter_hook,
finalizer=self._asyncgen_finalizer_hook)
try:
+ events._set_running_loop(self)
while True:
self._run_once()
if self._stopping:
@@ -408,6 +412,7 @@
finally:
self._stopping = False
self._thread_id = None
+ events._set_running_loop(None)
self._set_coroutine_wrapper(False)
if self._asyncgens is not None:
sys.set_asyncgen_hooks(*old_agen_hooks)
diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index b89b4b2..8575e2c 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -607,6 +607,30 @@
_lock = threading.Lock()
+# A TLS for the running event loop, used by _get_running_loop.
+class _RunningLoop(threading.local):
+ _loop = None
+_running_loop = _RunningLoop()
+
+
+def _get_running_loop():
+ """Return the running event loop or None.
+
+ This is a low-level function intended to be used by event loops.
+ This function is thread-specific.
+ """
+ return _running_loop._loop
+
+
+def _set_running_loop(loop):
+ """Set the running event loop.
+
+ This is a low-level function intended to be used by event loops.
+ This function is thread-specific.
+ """
+ _running_loop._loop = loop
+
+
def _init_event_loop_policy():
global _event_loop_policy
with _lock:
@@ -632,7 +656,17 @@
def get_event_loop():
- """Equivalent to calling get_event_loop_policy().get_event_loop()."""
+ """Return an asyncio event loop.
+
+ When called from a coroutine or a callback (e.g. scheduled with call_soon
+ or similar API), this function will always return the running event loop.
+
+ If there is no running event loop set, the function will return
+ the result of `get_event_loop_policy().get_event_loop()` call.
+ """
+ current_loop = _get_running_loop()
+ if current_loop is not None:
+ return current_loop
return get_event_loop_policy().get_event_loop()
diff --git a/Lib/asyncio/test_utils.py b/Lib/asyncio/test_utils.py
index 307fffc..9d32822 100644
--- a/Lib/asyncio/test_utils.py
+++ b/Lib/asyncio/test_utils.py
@@ -449,7 +449,13 @@
self.set_event_loop(loop)
return loop
+ def setUp(self):
+ self._get_running_loop = events._get_running_loop
+ events._get_running_loop = lambda: None
+
def tearDown(self):
+ events._get_running_loop = self._get_running_loop
+
events.set_event_loop(None)
# Detect CPython bug #23353: ensure that yield/yield-from is not used