一把大锁在加一把小锁。
import threading
import time
def run1():
print("grab the first part data")
lock.acquire()
global num
num += 1
lock.release()
return num
def run2():
print("grab the second part data")
lock.acquire()
global num2
num2 += 1
lock.release()
return num2
def run3():
lock.acquire()
res = run1()
print(‘--------between run1 and run2-----‘)
res2 = run2()
lock.release()
print(res, res2)
if __name__ == ‘__main__‘:
num, num2 = 0, 0
lock = threading.Lock()
for i in range(10):
t = threading.Thread(target=run3)
t.start()
while threading.active_count() != 1:
print(threading.active_count())
else:
print(‘----all threads done---‘)
print(num, num2)
过程分享:
1、启动10个线程，每个线程都执行run3。
2、run3中先加了一个锁，然后执行run1。
3、run1中也加了一个锁，计算完成后解锁返回数据。执行run2。
4、run2中同样加了一个锁，计算完成后解锁打印run1,run2返回值。
5、最后打印num1、num2。
需要注意的是在执行过程中是有两把锁的，一个run3，一个run1或者run2。
运行结果：
11 11 11 11 11 11 11 11 # 程序进入死循环
死循环的原因是解锁的时候 钥匙拿错了导致进程退不出来，解决死锁就是要使用递归锁。
threading.Lock() 改为 threading.RLock()
import threading
import time
def run1():
print("grab the first part data")
lock.acquire()
global num
num += 1
lock.release()
return num
def run2():
print("grab the second part data")
lock.acquire()
global num2
num2 += 1
lock.release()
return num2
def run3():
lock.acquire()
res = run1()
print(‘--------between run1 and run2-----‘)
res2 = run2()
lock.release()
print(res, res2)
if __name__ == ‘__main__‘:
num, num2 = 0, 0
lock = threading.RLock()
for i in range(1):
t = threading.Thread(target=run3)
t.start()
while threading.active_count() != 1:
print(threading.active_count())
else:
print(‘----all threads done---‘)
print(num, num2)
运行结果
grab the first part data --------between run1 and run2----- grab the second part data 1 1 ----all threads done--- 1 1
实现原理：
解锁的时候找对应的钥匙。
原文：http://www.cnblogs.com/qing-chen/p/7680101.html