可重入鎖:支持在同一線程中多次請求同一資源

import threading

import time

class MyThread(threading.Thread):

def run(self):

global num

time.sleep(1)

if mutex.acquire(1):

num = num+1

msg = self.name+' set num to '+str(num)

print(msg)

mutex.acquire()

print('Do another thing.')

mutex.release()

mutex.release()

num = 0

mutex = threading.RLock()

def test():

for i in range(5):

t = MyThread()

t.start()

if __name__ == '__main__':

test()

那我既然一個線程要用兩次共享變量,我直接acquire后我就不release,干嘛要acquire兩次不是多此一舉?

直接只有一次acquire和一次release:

import threading

import time

class MyThread(threading.Thread):

def run(self):

global num

time.sleep(1)

if mutex.acquire(1):

num = num+1

msg = self.name+' set num to '+str(num)

print(msg)

print('Do another thing.')

mutex.release()

num = 0

mutex = threading.RLock()

def test():

for i in range(5):

t = MyThread()

t.start()

if __name__ == '__main__':

test()

還是我學藝不精,說可重入鎖是用來防止死鎖的,那么可重入鎖應該用在什么情況下?

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