线程死锁和递归锁
作者：互联网
'''
import threading
import time
class mythread(threading.Thread):
def A(self):
locka.acquire() #获取锁
print(self.name,"getlocka",time.ctime())
time.sleep(3)
lockb.acquire()
print(self.name,"getlockb",time.ctime())
lockb.release() #释放锁
locka.release()
def B(self):
lockb.acquire()
print(self.name,"getlockb",time.ctime())
time.sleep(2)
locka.acquire()
print(self.name,"getlocka",time.ctime())
locka.release()
lockb.release()
def run(self):
self.A()
self.B()
if __name__=="__main__":
locka=threading.Lock()
lockb=threading.Lock()
threads=[]
for i in range(5):
threads.append(mythread())#mythread()为实例化对象；将实例化5次并追加到列表中
print(threads)
for t in threads: #遍历列表中的实例化对象，分分别进行启动，并调用其中run方法
t.start()
for t in threads:
t.join()
'''
'''
#输出结果：
Thread-1 getlocka Wed Jan 5 15:58:16 2022
Thread-1 getlockb Wed Jan 5 15:58:19 2022
Thread-1 getlockb Wed Jan 5 15:58:19 2022
Thread-2 getlocka Wed Jan 5 15:58:19 2022
当循环将线程追加到threads列表中以后，首先将线程1取出去调用run方法，当线程1获取到锁A,去执行打印，然后去获取B锁，执行打印
随后释放B锁，A锁；同时线程1去执行B函数获取b锁，并打印；再休息了2s后想要去获取A锁，而与此同时线程2已经执行了A函数获取了A锁将要获取B锁，
因为线程1没有执行到释放B锁，线程2没法拿到B锁，线程2没有释放A锁，线程1没有办法拿到B锁；导致程序无法执行，死在当前程序中
'''
# 解决方法使用，递归锁，其就是一把锁，而此锁可以被重复使用
# 如下：
import threading
import time
class mythread(threading.Thread):
def A(self):
lock.acquire()
print(self.name,"getlocka",time.ctime())
time.sleep(3)
lock.acquire()
print(self.name,"getlockb",time.ctime())
lock.release()
lock.release()
def B(self):
lock.acquire()
print(self.name,"getlockb",time.ctime())
time.sleep(2)
lock.acquire()
print(self.name,"getlocka",time.ctime())
lock.release()
lock.release()
def run(self):
self.A()
self.B()
if __name__=="__main__":
# locka=threading.Lock()
# lockb=threading.Lock()
lock=threading.RLock() #创建递归锁
threads=[]
for i in range(5):
threads.append(mythread())#mythread()为实例化对象；将实例化5次并追加到列表中
print(threads)
for t in threads: #遍历列表中的实例化对象，分分别进行启动，并调用其中run方法
t.start()
for t in threads:
t.join()
#输出结果：
"""
Thread-1 getlocka Wed Jan 5 17:18:39 2022
Thread-1 getlockb Wed Jan 5 17:18:42 2022
Thread-2 getlocka Wed Jan 5 17:18:42 2022
Thread-2 getlockb Wed Jan 5 17:18:45 2022
Thread-2 getlockb Wed Jan 5 17:18:45 2022
Thread-2 getlocka Wed Jan 5 17:18:47 2022
Thread-4 getlocka Wed Jan 5 17:18:47 2022
Thread-4 getlockb Wed Jan 5 17:18:50 2022
Thread-4 getlockb Wed Jan 5 17:18:50 2022
Thread-4 getlocka Wed Jan 5 17:18:52 2022
Thread-1 getlockb Wed Jan 5 17:18:52 2022
Thread-1 getlocka Wed Jan 5 17:18:54 2022
Thread-3 getlocka Wed Jan 5 17:18:54 2022
Thread-3 getlockb Wed Jan 5 17:18:57 2022
Thread-3 getlockb Wed Jan 5 17:18:57 2022
Thread-3 getlocka Wed Jan 5 17:18:59 2022
Thread-5 getlocka Wed Jan 5 17:18:59 2022
Thread-5 getlockb Wed Jan 5 17:19:02 2022
Thread-5 getlockb Wed Jan 5 17:19:02 2022
Thread-5 getlocka Wed Jan 5 17:19:04 2022
"""
对于A方法，当获取到大锁的时候，再去获取小锁，然后分别释放小锁和大锁完毕以后，所有线程都会去抢获取锁的资源，谁先抢到，哪个线程则会进行执行
标签：17,递归,Wed,18,self,Jan,死锁,线程,2022Thread 来源： https://www.cnblogs.com/ainiforever20220101/p/15787781.html