https://github.com/python/cpython/commit/77c06f3da629b5088975309959ef6895bef841e3
commit: 77c06f3da629b5088975309959ef6895bef841e3
branch: main
author: Konstantin Vlasov <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2026-03-14T11:07:30+05:30
summary:
gh-145703: Fix `asyncio.BaseEventLoop` low clock resolution (#145706)
files:
A Misc/NEWS.d/next/Library/2026-03-09-19-59-05.gh-issue-145703.4EEP7J.rst
M Lib/asyncio/base_events.py
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index b565b1d8a9e226..0930ef403c6c4b 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -19,14 +19,15 @@
import errno
import heapq
import itertools
+import math
import os
import socket
import stat
import subprocess
+import sys
import threading
import time
import traceback
-import sys
import warnings
import weakref
@@ -2022,7 +2023,10 @@ def _run_once(self):
event_list = None
# Handle 'later' callbacks that are ready.
- end_time = self.time() + self._clock_resolution
+ now = self.time()
+ # Ensure that `end_time` is strictly increasing
+ # when the clock resolution is too small.
+ end_time = now + max(self._clock_resolution, math.ulp(now))
while self._scheduled:
handle = self._scheduled[0]
if handle._when >= end_time:
diff --git
a/Misc/NEWS.d/next/Library/2026-03-09-19-59-05.gh-issue-145703.4EEP7J.rst
b/Misc/NEWS.d/next/Library/2026-03-09-19-59-05.gh-issue-145703.4EEP7J.rst
new file mode 100644
index 00000000000000..bc239ce58c9eed
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-09-19-59-05.gh-issue-145703.4EEP7J.rst
@@ -0,0 +1,3 @@
+:mod:`asyncio`: Make sure that :meth:`loop.call_at <asyncio.loop.call_at>` and
+:meth:`loop.call_later <asyncio.loop.call_later>` trigger scheduled events on
+time when the clock resolution becomes too small.
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