gh-150818: Speed up logging.getLogger() for existing loggers (GH-150825)

diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 6eef90ae5cd9143f423a1cf6d6c28b017e7a8b07..9febc50b1264ef42c608abbbb931fb0f9993c986 100644 (file)
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1373,9 +1373,16 @@ class Manager(object):
         logger and fix up the parent/child references which pointed to the
         placeholder to now point to the logger.
         """
-        rv = None
         if not isinstance(name, str):
             raise TypeError('A logger name must be a string')
+        # Fast path: an already-registered, non-placeholder logger can be
+        # returned without taking the lock. dict.get() is atomic under both
+        # the GIL and free threading, and a Logger is fully initialised before
+        # being inserted into loggerDict under the lock, so this never sees a
+        # partially-constructed object.
+        rv = self.loggerDict.get(name)
+        if rv is not None and not isinstance(rv, PlaceHolder):
+            return rv
         with _lock:
             if name in self.loggerDict:
                 rv = self.loggerDict[name]

diff --git a/Misc/NEWS.d/next/Library/2026-06-02-15-44-58.gh-issue-150818.Orcefu.rst b/Misc/NEWS.d/next/Library/2026-06-02-15-44-58.gh-issue-150818.Orcefu.rst
new file mode 100644 (file)
index 0000000..3bb1600
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-06-02-15-44-58.gh-issue-150818.Orcefu.rst
@@ -0,0 +1,3 @@
+Speed up :func:`logging.getLogger` with a lock-free fast path that returns an
+already-registered logger without acquiring the logging lock. Patch by Bernát
+Gábor.