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[3.10] bpo-44422: Fix threading.enumerate() reentrant call (GH-26727) #26737

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Merged
merged 1 commit into from
Jun 15, 2021
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[3.10] bpo-44422: Fix threading.enumerate() reentrant call (GH-26727) #26737

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9 changes: 6 additions & 3 deletions Lib/threading.py
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Original file line number Diff line number Diff line change
Expand Up @@ -775,8 +775,11 @@ class BrokenBarrierError(RuntimeError):
def _newname(name_template):
return name_template % _counter()

# Active thread administration
_active_limbo_lock = _allocate_lock()
# Active thread administration.
#
# bpo-44422: Use a reentrant lock to allow reentrant calls to functions like
# threading.enumerate().
_active_limbo_lock = RLock()
_active = {} # maps thread id to Thread object
_limbo = {}
_dangling = WeakSet()
Expand Down Expand Up @@ -1564,7 +1567,7 @@ def _after_fork():
# by another (non-forked) thread. http://bugs.python.org/issue874900
global _active_limbo_lock, _main_thread
global _shutdown_locks_lock, _shutdown_locks
_active_limbo_lock = _allocate_lock()
_active_limbo_lock = RLock()

# fork() only copied the current thread; clear references to others.
new_active = {}
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2021-06-14-23-28-17.bpo-44422.BlWOgv.rst
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@@ -0,0 +1,3 @@
The :func:`threading.enumerate` function now uses a reentrant lock to
prevent a hang on reentrant call.
Patch by Victor Stinner.