redis锁的问题

Question

我看网上这篇文章，http://blog.csdn.net/jj546630...
里面获取redis锁的过程

while lock != 1:
  now = int(time.time())
  lock_timeout = now + LOCK_TIMEOUT + 1
  lock = redis_client.setnx(lock_key, lock_timeout)
  if lock == 1 or (now > int(redis_client.get(lock_key))) and now > int(redis_client.getset(lock_key, lock_timeout)):  
    break
  else:
    time.sleep(0.001)
    

其中假如lock==0 且 now > int(redis_client.get(lock_key)
此时，now > int(redis_client.getset(lock_key, lock_timeout)这句有问题吧？这没有互斥啊，getset不是同步方法吧，这样怎么获取锁了？