Demonstrate the interaction between GC and threading in Python. Followup to http://emptysqua.re/blog/pypy-garbage-collection-and-a-deadlock/

deadlock2.py

import threading
import gc
from time import sleep

lock = threading.RLock()

def target():
    print 'target'
    with lock:
        sleep(2)

t = threading.Thread(target=target)
t.daemon = True
t.start()
sleep(1)  # Wait for 'target' to get lock.


class C(object):
    def __del__(self):
        print('getting lock')
        with lock:
            print('releasing lock')
            pass

c = C()
del c
with lock:
    print('collecting')
    gc.collect()