deadlock.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Alejandro Santos, @alejolp.

"""
This program deadlocks beacuse producers are also consumers and the Queue 
has a fixed limit. When the consumer reaches a specific level on the expansion
tree, deadlocks.
"""

import os
import sys
import multiprocessing
import time
import random

q = multiprocessing.Queue(32)

def f():
    while True:
        x = q.get()
        time.sleep(random.randint(1,9) / 10.0)
        print "Task:",x
        for y in range(2):
            q.put(2*x + y)

q.put(1)

procs = [multiprocessing.Process(target=f) for z in range(8)]
for p in procs:
    p.start()