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-rw-r--r--Lib/_threading_local.py8
-rw-r--r--Lib/threading.py4
-rw-r--r--Misc/NEWS3
3 files changed, 12 insertions, 3 deletions
diff --git a/Lib/_threading_local.py b/Lib/_threading_local.py
index 6d770350ff..6e8a8d85a7 100644
--- a/Lib/_threading_local.py
+++ b/Lib/_threading_local.py
@@ -217,10 +217,12 @@ class local(_localbase):
key = object.__getattribute__(self, '_local__key')
try:
- threads = list(threading.enumerate())
+ # We use the non-locking API since we might already hold the lock
+ # (__del__ can be called at any point by the cyclic GC).
+ threads = threading._enumerate()
except:
- # If enumerate fails, as it seems to do during
- # shutdown, we'll skip cleanup under the assumption
+ # If enumerating the current threads fails, as it seems to do
+ # during shutdown, we'll skip cleanup under the assumption
# that there is nothing to clean up.
return
diff --git a/Lib/threading.py b/Lib/threading.py
index 88101b0cb5..d5412e935c 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -798,6 +798,10 @@ def active_count():
activeCount = active_count
+def _enumerate():
+ # Same as enumerate(), but without the lock. Internal use only.
+ return list(_active.values()) + list(_limbo.values())
+
def enumerate():
with _active_limbo_lock:
return list(_active.values()) + list(_limbo.values())
diff --git a/Misc/NEWS b/Misc/NEWS
index c67407f8af..2ce607096a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -40,6 +40,9 @@ Core and Builtins
Library
-------
+- Issue #7264: Fix a possible deadlock when deallocating thread-local objects
+ which are part of a reference cycle.
+
- Issue #6896: mailbox.Maildir now invalidates its internal cache each time
a modification is done through it. This fixes inconsistencies and test
failures on systems with slightly bogus mtime behaviour.