进程间同步，可以使用lock进行控制。
官方文档的例子如下：
from multiprocessing import Process, Lock
def f(l, i):
l.acquire()
print 'hello world', i
l.release()
if __name__ == '__main__':
lock = Lock()
for num in range(10):
Process(target=f, args=(lock, num)).start()
运行结果：
hello world 0 hello world 1 hello world 2 hello world 3 hello world 4 hello world 5 hello world 6 hello world 7 hello world 8 hello world 9
or
from multiprocessing import Process, Lock
from time import sleep
def f(l, i):
l.acquire()
print 'hello world', i
l.release()
def n(l,i):
l.acquire()
print 'hello world', i
sleep(5)
l.release()
if __name__ == '__main__':
lock = Lock()
result = []
result.append(Process(target = n,args = (lock,'first')))
result.append(Process(target = f,args = (lock,'sec')))
for x in result:
x.start()
for x in result:
x.join()
print('main process run OK')
运行结果：
hello world first 中间等待5秒钟 hello world sec main process run OK