[gentoo-portage-dev] [PATCH] global_event_loop: return running loop for current thread

[Zac Medico]

Like asyncio.get_event_loop(), return the running loop for the
current thread if there is one, and otherwise construct a new
one if needed. This allows the _safe_loop function to become
synonymous with the global_event_loop function.

Bug: https://bugs.gentoo.org/763339
Signed-off-by: Zac Medico <zmedico@g.o>
---
 .../util/_eventloop/global_event_loop.py      | 28 ++-----------------
 lib/portage/util/futures/_asyncio/__init__.py | 22 ++++++++++-----
 2 files changed, 17 insertions(+), 33 deletions(-)

diff --git a/lib/portage/util/_eventloop/global_event_loop.py b/lib/portage/util/_eventloop/global_event_loop.py
index 413011178..bf314dc34 100644
--- a/lib/portage/util/_eventloop/global_event_loop.py
+++ b/lib/portage/util/_eventloop/global_event_loop.py
@@ -1,28 +1,4 @@
-# Copyright 2012-2020 Gentoo Authors
+# Copyright 2012-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
-import portage
-from portage.util._eventloop.asyncio_event_loop import AsyncioEventLoop
-
-_instances = {}
-
-
-def global_event_loop():
-	"""
-	Get a global EventLoop (or compatible object) instance which
-	belongs exclusively to the current process.
-	"""
-
-	pid = portage.getpid()
-	instance = _instances.get(pid)
-	if instance is not None:
-		return instance
-
-	constructor = AsyncioEventLoop
-
-	# Use the _asyncio_wrapper attribute, so that unit tests can compare
-	# the reference to one retured from _wrap_loop(), since they should
-	# not close the loop if it refers to a global event loop.
-	instance = constructor()._asyncio_wrapper
-	_instances[pid] = instance
-	return instance
+from portage.util.futures._asyncio import _safe_loop as global_event_loop
diff --git a/lib/portage/util/futures/_asyncio/__init__.py b/lib/portage/util/futures/_asyncio/__init__.py
index d39f31786..ab1468d43 100644
--- a/lib/portage/util/futures/_asyncio/__init__.py
+++ b/lib/portage/util/futures/_asyncio/__init__.py
@@ -1,4 +1,4 @@
-# Copyright 2018-2020 Gentoo Authors
+# Copyright 2018-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 __all__ = (
@@ -37,9 +37,6 @@ portage.proxy.lazyimport.lazyimport(globals(),
 	'portage.util.futures:compat_coroutine@_compat_coroutine',
 )
 from portage.util._eventloop.asyncio_event_loop import AsyncioEventLoop as _AsyncioEventLoop
-from portage.util._eventloop.global_event_loop import (
-	global_event_loop as _global_event_loop,
-)
 # pylint: disable=redefined-builtin
 from portage.util.futures.futures import (
 	CancelledError,
@@ -238,7 +235,7 @@ def _wrap_loop(loop=None):
 	# The default loop returned by _wrap_loop should be consistent
 	# with global_event_loop, in order to avoid accidental registration
 	# of callbacks with a loop that is not intended to run.
-	loop = loop or _global_event_loop()
+	loop = loop or _safe_loop()
 	return (loop if hasattr(loop, '_asyncio_wrapper')
 		else _AsyncioEventLoop(loop=loop))
 
@@ -267,8 +264,9 @@ def _safe_loop():
 	@rtype: asyncio.AbstractEventLoop (or compatible)
 	@return: event loop instance
 	"""
-	if portage._internal_caller or threading.current_thread() is threading.main_thread():
-		return _global_event_loop()
+	loop = _get_running_loop()
+	if loop is not None:
+		return loop
 
 	thread_key = threading.get_ident()
 	with _thread_weakrefs.lock:
@@ -286,6 +284,16 @@ def _safe_loop():
 	return loop
 
 
+def _get_running_loop():
+	with _thread_weakrefs.lock:
+		if _thread_weakrefs.pid == portage.getpid():
+			try:
+				loop = _thread_weakrefs.loops[threading.get_ident()]
+			except KeyError:
+				return None
+			return loop if loop.is_running() else None
+
+
 def _thread_weakrefs_atexit():
 	with _thread_weakrefs.lock:
 		if _thread_weakrefs.pid == portage.getpid():
-- 
2.26.2