互相等待另外一个线程的释放
1 import threading 2 import time 3 4 5 class MyThread(threading.Thread): 6 def action(self): 7 lock1.acquire() 8 time.sleep(1) 9 print(self.name,'got A',time.time()) 10 lock2.acquire() 11 print(self.name,'got B',time.time()) 12 lock2.release() 13 lock1.release() 14 def actonB(self): 15 lock2.acquire() 16 time.sleep(1) 17 print(self.name,'got B',time.time()) 18 lock1.acquire() 19 print(self.name,'got A',time.time()) 20 lock1.release() 21 lock2.release() 22 def run(self): 23 self.action() 24 self.actonB() 25 26 l = list() 27 lock1 = threading.Lock() 28 lock2 = threading.Lock() 29 for i in range(5): 30 t=MyThread() 31 l.append(t) 32 t.start() 33 for i in l: 34 i.join() 35 print('ending.....') 36 输出： 37 Thread-1 got A 1586753664.8394556 38 Thread-1 got B 1586753664.8394556 39 Thread-2 got A 1586753665.8402793 40 Thread-1 got B 1586753665.8402793
结论：一把锁只能是有一次。 有的锁还没有解开，其它的线程就开始执行了。导致死锁的产生。
解决办法：使用一把锁。Rlock
1 import threading 2 import time 3 4 5 class MyThread(threading.Thread): 6 def action(self): 7 r_lock.acquire() 8 time.sleep(1) 9 print(self.name,'got A',time.time()) 10 r_lock.acquire() 11 print(self.name,'got B',time.time()) 12 r_lock.release() 13 r_lock.release() 14 def actonB(self): 15 r_lock.acquire() 16 time.sleep(1) 17 print(self.name,'got B',time.time()) 18 r_lock.acquire() 19 print(self.name,'got A',time.time()) 20 r_lock.release() 21 r_lock.release() 22 def run(self): 23 self.action() 24 self.actonB() 25 26 l = list() 27 # lock1 = threading.Lock() 28 # lock2 = threading.Lock() 29 r_lock = threading.RLock() 30 for i in range(5): 31 t=MyThread() 32 l.append(t) 33 t.start() 34 for i in l: 35 i.join() 36 print('ending.....') 37 输出： 38 Thread-1 got A 1586754305.5835774 39 Thread-1 got B 1586754305.5835774 40 Thread-1 got B 1586754306.5840476 41 Thread-1 got A 1586754306.5840476 42 Thread-3 got A 1586754307.5844278 43 Thread-3 got B 1586754307.5844278 44 Thread-3 got B 1586754308.5852091 45 Thread-3 got A 1586754308.5852091 46 Thread-5 got A 1586754309.5857675 47 Thread-5 got B 1586754309.5857675 48 Thread-5 got B 1586754310.585957 49 Thread-5 got A 1586754310.585957 50 Thread-4 got A 1586754311.586401 51 Thread-4 got B 1586754311.586401 52 Thread-4 got B 1586754312.5868573 53 Thread-4 got A 1586754312.5868573 54 Thread-2 got A 1586754313.587585 55 Thread-2 got B 1586754313.587585 56 Thread-2 got B 1586754314.5880973 57 Thread-2 got A 1586754314.5880973 58 ending.....
原理：内部有一个计数器，只要有所存在就不会被其他的线程使用cpu。
勇士一把锁可以无限次的使用。 开了多少把锁就必须等到所有的锁都接触以后才能运行其它的线程。