python: backport 'avoid creating additional event loops per thread'

This commit is two backports squashed into one to avoid regressions.

python: *really* remove get_event_loop

A prior commit, aa1ff990, switched away from using get_event_loop *by
default*, but this is not good enough to avoid deprecation warnings as
`asyncio.get_event_loop_policy().get_event_loop()` is *also*
deprecated. Replace this mechanism with explicit calls to
asyncio.get_new_loop() and revise the cleanup mechanisms in __del__ to
match.

python: avoid creating additional event loops per thread

"Too hasty by far!", commit 21ce2ee4 attempted to avoid deprecated
behavior altogether by calling new_event_loop() directly if there was no
loop currently running, but this has the unfortunate side effect of
potentially creating multiple event loops per thread if tests
instantiate multiple QMP connections in a single thread. This behavior
is apparently not well-defined and causes problems in some, but not all,
combinations of Python interpreter version and platform environment.

Partially revert to Daniel Berrange's original patch, which calls
get_event_loop and simply suppresses the deprecation warning in
Python<=3.13. This time, however, additionally register new loops
created with new_event_loop() so that future calls to get_event_loop()
will return the loop already created.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
cherry picked from commit python-qemu-qmp@21ce2ee4f2df87efe84a27b9c5112487f4670622
cherry picked from commit python-qemu-qmp@c08fb82b38212956ccffc03fc6d015c3979f42fe
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 2 insertions, 8 deletions

diff --git a/python/qemu/qmp/qmp_tui.py b/python/qemu/qmp/qmp_tui.py
index 12bdc17c99..d946c20513 100644
--- a/python/qemu/qmp/qmp_tui.py
+++ b/python/qemu/qmp/qmp_tui.py
@@ -51,7 +51,7 @@ from .legacy import QEMUMonitorProtocol, QMPBadPortError
 from .message import DeserializationError, Message, UnexpectedTypeError
 from .protocol import ConnectError, Runstate
 from .qmp_client import ExecInterruptedError, QMPClient
-from .util import pretty_traceback
+from .util import get_or_create_event_loop, pretty_traceback
 
 
 # The name of the signal that is used to update the history list
@@ -387,13 +387,7 @@ class App(QMPClient):
         """
         screen = urwid.raw_display.Screen()
         screen.set_terminal_properties(256)
-
-        try:
-            self.aloop = asyncio.get_running_loop()
-        except RuntimeError:
-            # No running asyncio event loop. Create one if necessary.
-            self.aloop = asyncio.get_event_loop_policy().get_event_loop()
-
+        self.aloop = get_or_create_event_loop()
         self.aloop.set_debug(debug)
 
         # Gracefully handle SIGTERM and SIGINT signals