Python连载35-死锁问题以及解决方式

import threading

import time

?

lock_1 = threading.Lock()

lock_2 = threading.Lock()

?

def func_1():

    print("func_1 starting......")

    lock_1.acquire()#我先占上lock_1

    print("func_1 申请了 lock_1.....")

    time.sleep(2)#必须得等一下啊，让这这两个函数形成死锁

    print("func_1 等待lock_2......")

    lock_2.acquire()

    print("func_1 申请了lock_2")

    lock_2.release()

    print("func_1 释放了 lock_2")

    lock_1.release()

    print("func_1 释放了 lock_1")

?

    print("func_1 done")

?

def func_2():

    print("func_2 staring......")

    lock_2.acquire()#我先占上lock_2

    print("func_2申请了lock_2.....")

    time.sleep(4)

    print("func_2等待lock_1.......")

    lock_1.acquire()

    print("func_2申请了lock_1.....")

    lock_1.release()

    print("func_2 释放了 lock_1")

    lock_2.release()

    print("func_2 释放了 lock_2")

?

    print("func_2 done")

?

if __name__ == "__main__":

    t1 = threading.Thread(target=func_1,args=())

    t2 = threading.Thread(target=func_2,args=())

?

    t1.start()

    t2.start()

?

    t1.join()

    t2.join()

lock_3 = threading.Lock()

lock_4 = threading.Lock()

?

def func_3():

    print("func_3 starting.....")

    lock_3.acquire(timeout=-1)

    print("func_3 申请了lock_3.....")

    time.sleep(2)

    print("func_3 等待lock_4.......")

?

    rst = lock_4.acquire(timeout=-1)#可见这是一个返回值是布尔类型的变量，timeout代表超时跳出

    if rst:

        print("func_3的带了锁lock_4")

        lock_4.release()

        print("func_3释放了lock_4")

    else:

        print("func_3没申请到lock_4")

?

    lock_3.release()

    print("func_3释放了lock_3")

?

    print("func_3 done......")

?

?

def func_4():

    print("func_4 starting.....")

    lock_4.acquire(timeout=4)

    print("func_4 申请了lock_4.....")

    time.sleep(2)

    print("func_4 等待lock_3.......")

?

    rst = lock_3.acquire(timeout=2)

    if rst:

        print("func_3得到了了锁lock_3")

        lock_3.release()

        print("func_4释放了lock_3")

    else:

        print("func_4没申请到lock_3")

?

    lock_4.release()

    print("func_4释放了lock_4")

?

    print("func_4 done......")

?

if __name__ == "__main__":

?

    t3 = threading.Thread(target=func_3,args=())

    t4 = threading.Thread(target=func_4,args=())

?

    t3.start()

    t4.start()

?

    t3.join()

    t4.join()