https://github.com/python/cpython/commit/3835fca3f5ce0512ef7df10c7188daf04e07e409
commit: 3835fca3f5ce0512ef7df10c7188daf04e07e409
branch: main
author: Bernát Gábor <[email protected]>
committer: vsajip <[email protected]>
date: 2026-06-05T16:00:56+01:00
summary:
gh-150818: Wire logger parent before publishing it in getLogger() (GH-150941)
files:
M Lib/logging/__init__.py
M Lib/test/test_logging.py
diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 9febc50b1264ef..b4a5f5cc2f598f 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1377,9 +1377,10 @@ def getLogger(self, name):
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.
+ # the GIL and free threading. A Logger is inserted into loggerDict only
+ # after it is fully wired up (parent/child references fixed) under the
+ # lock, so the fast path never observes a logger whose parent is not
yet
+ # set.
rv = self.loggerDict.get(name)
if rv is not None and not isinstance(rv, PlaceHolder):
return rv
@@ -1390,14 +1391,18 @@ def getLogger(self, name):
ph = rv
rv = (self.loggerClass or _loggerClass)(name)
rv.manager = self
- self.loggerDict[name] = rv
self._fixupChildren(ph, rv)
self._fixupParents(rv)
+ # Publish only after rv is fully wired: the fast path reads
+ # loggerDict without the lock.
+ self.loggerDict[name] = rv
else:
rv = (self.loggerClass or _loggerClass)(name)
rv.manager = self
- self.loggerDict[name] = rv
self._fixupParents(rv)
+ # Publish only after rv is fully wired: the fast path reads
+ # loggerDict without the lock.
+ self.loggerDict[name] = rv
return rv
def setLoggerClass(self, klass):
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index d4fa78acfd11de..9f29fe8a5b3c9b 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -4269,6 +4269,43 @@ def test_set_log_record_factory(self):
man.setLogRecordFactory(expected)
self.assertEqual(man.logRecordFactory, expected)
+ @threading_helper.requires_working_threading()
+ def test_getLogger_fast_path_never_returns_unwired_logger(self):
+ # getLogger()'s lock-free fast path returns a logger straight out of
+ # loggerDict, so a logger must be published there only after
+ # _fixupParents() has set its parent; otherwise a concurrent caller
+ # observes it detached from the hierarchy (gh-150818 follow-up).
+ manager = logging.Manager(logging.RootLogger(logging.WARNING))
+ name = 'a.b.c'
+
+ paused = threading.Event()
+ seen = []
+ real_fixup = manager._fixupParents
+
+ # Pause the creating thread between publishing rv and wiring its
+ # parent, then read loggerDict the way the fast path does and snapshot
+ # the parent at that instant (rv is wired in place soon after).
+ def fixup(alogger):
+ paused.set()
+ reader.join()
+ real_fixup(alogger)
+
+ def read():
+ paused.wait()
+ rv = manager.loggerDict.get(name)
+ if rv is not None and not isinstance(rv, logging.PlaceHolder):
+ seen.append(rv.parent)
+
+ reader = threading.Thread(target=read)
+ manager._fixupParents = fixup
+ try:
+ reader.start()
+ manager.getLogger(name)
+ finally:
+ manager._fixupParents = real_fixup
+
+ self.assertNotIn(None, seen)
+
class ChildLoggerTest(BaseTest):
def test_child_loggers(self):
r = logging.getLogger()
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