import threading
import os
import signal
import sys
l = threading.RLock()
def lock_release(signal=None, frame=None):
    l.acquire()
    l.release()
signal.signal(signal.SIGUSR2, lock_release)
print (os.getpid())
while True:
  sys.stdout.write('.')
  sys.stdout.flush()
  for _ in range(100000):
      lock_release()