忙等待
while True:
pass
this is busy waiting
while True:
time.sleep(10)
this is not busy waiting, bucause cpu are free to do other things, and only need trivial cpu cycles
http://stackoverflow.com/questions/529034/python-pass-or-sleep-for-long-running-processes
busy waiting is considered as anti-pattern, but using it in spinning-lock is ok
should use select if we need to wait for something
https://en.wikipedia.org/wiki/Busy_waiting