learn-python3/do_Lock.py at master · zzccoder/learn-python3

45 lines (37 loc) · 1.16 KB

#!/bin/env python3

# -*- coding:utf-8 -*-

#多线程中，所有变量都由所有线程共享

import time,threading

# 假定这是你的银行存款:

balance = 0

def change_it(n):

# 先存后取，结果应该为0:

global balance

balance = balance + n

balance = balance - n

def run_thread(n):

for i in range(100000):

change_it(n)

t1 = threading.Thread(target=run_thread, args=(5,))

t2 = threading.Thread(target=run_thread, args=(8,))

t1.start()

t2.start()

t1.join()

t2.join()

print(balance) # 线程调度由操作系统决定，t1、t2交替进行，balance结果不一定是0

# threading.Lock()

# 不同的线程持有不同的锁，并试图获取对方持有的锁时，可能会造成死锁

# 导致多个线程全部挂起，既不能执行，也无法结束，只能靠操作系统强制终止。

# GIL锁：Global Interpreter Lock

balance = 0

lock = threading.Lock()

def run_thread(n):

for i in range(100000):

# 先要获取锁:

lock.acquire()

try:

# 放心地改吧:

change_it(n)

finally:

# 改完了一定要释放锁,否则称为死线程:

lock.release()

FilesExpand file tree