threading.RLock (and threading.Condition) doesn't work on Python 3.2+ with monkey-patching

[vstinner]

The threading.RLock class was reimplemented in C in Python 3.2. threading.RLock doesn't use _thread.get_ident() or threading.get_ident(), but it calls directly the C function. Because of that, RLock doesn't work ("as expected") with eventlet monkey-patching. Example:

#!python
import eventlet
eventlet.monkey_patch()

import threading
#threading.RLock = threading._PyRLock

def func(c):
    with c:
        print("thread: owned?", c._is_owned())
        c.notify()
        print("thread: owned?", c._is_owned())

c = threading.Condition()
print("LOCK", threading.RLock)
with c:
    t = threading.Thread(target=func, args=(c,))
    t.start()
    print("main: owned?", c._is_owned())
    c.wait()
    print("main: owned?", c._is_owned())

The code hangs with eventlet 0.16 on Python 3.5 (and probably also Python 3.2, 3.3 and 3.4).

I tried to reuse the Python implementation of the RLock class (threading._PyRLock), but in this case c.notify() raises: RuntimeError("cannot notify on un-acquired lock").

I will work on a fix.

Note: I'm working on porting the Oslo Messaging project to Python 3. The initial issue came from a threading.Condition object, threading.Condition uses internally a threading.RLock.

[vstinner]

Oslo Messaging now works well on Python 3 with eventlet. I don't recall how the issue was fixed, but it now works well :-) So I close this old issue.