from weakref import WeakValueDictionary
import weakref

import gc
gc.set_threshold(1, 1, 1)

class C(object):
    def __init__(self, i):
        self.i = i
        self.loop = self

    def fiddle(self):
        if not hasattr(self, 'i'):
            raise SystemError('ack! %s %s' % (id(self), weakref.getweakrefcount(self)))

class Registry(object):
    def __init__(self):
        self.all = WeakValueDictionary()

    def register(self, conns):
        for x in conns:
            self.all[id(x)] = x

    def fiddle(self):
        for c in self.all.values():
            c.fiddle()

registry = Registry()

import random

import threading
mutex = threading.Lock()

class Worker(threading.Thread):
    def __init__(self, tid):
        threading.Thread.__init__(self)
        self.tid = tid

    def run(self):
        i = 0
        tid = self.tid
        while True:
            i += 1
            #mutex.acquire()
            conns = [C(j) for j in range(50)]
            #mutex.release()

            mutex.acquire()
            registry.register(conns)
            mutex.release()

            print "%d+%d" % (tid, i),
            if random.random() < 0.2:
                mutex.acquire()
                registry.fiddle()
                mutex.release()

ts = [Worker(tid) for tid in range(3)]
for t in ts:
    t.start()