Serhiy Storchaka added the comment:
_thread.RLock objects were wrongly pickleable before 3.6.
>>> import pickle, pickletools, _thread
>>> lock = _thread.RLock()
>>> lock.acquire()
True
>>> lock
<locked _thread.RLock object owner=-1219508480 count=1 at 0xb713acb0>
>>> pickle.loads(pickle.dumps(lock))
<unlocked _thread.RLock object owner=0 count=0 at 0xb6facb90>
>>> pickletools.dis(pickletools.optimize(pickle.dumps(lock)))
0: \x80 PROTO 3
2: c GLOBAL '_thread RLock'
17: ) EMPTY_TUPLE
18: \x81 NEWOBJ
19: . STOP
highest protocol among opcodes = 2
Actually only an information about the type was saved. The state of the lock
was lost. Unpickled lock was not a copy of the original lock, but a newly
created object with default initial state.
There were errors in programs that pickled _thread.RLock objects. Just these
errors were unnoticed. But programs likely didn't work as expected. Now an
exception raised on early stage allows you to rewrite not working code. I don't
know whether QueueHandler was designed to be pickleable. As a workaround try to
set the lock attribute to None before pickling and set it to threading.RLock()
(or call the createLock() method) after unpickling.
This change was made in issue22995.
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nosy: +serhiy.storchaka
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue29168>
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