from __future__ import print_function

import os
import sys
import threading
import thread
import time

def do_nothing():
    time.sleep(3)

def do_fork():
    time.sleep(1)
    if os.fork():
        sys.exit(0)

    do_child()

def do_verify(i):
    time.sleep(1 + i/10.)

    frame_from_sys = sys._current_frames()[thread.get_ident()]
    real_frame = sys._getframe()
    assert frame_from_sys is real_frame

    time.sleep(1)

def do_child():
    for i in range(5):
        threading.Thread(target=do_verify, args=(i,)).start()

def dotest():
    for i in range(4):
        threading.Thread(target=do_nothing).start()
    threading.Thread(target=do_fork).start()

if __name__ == "__main__":
    dotest()