死鎖導致程序卡死，
互斥鎖只能acquire一次，想acquire必須先release。

from threading import Thread,Lock
import time
mutexA=Lock()
mutexB=Lock()
class MyThread(Thread):
    def __init__(self):
        super().__init__()
    def run(self):
        self.f1()
        self.f2()
    def f1(self):
        mutexA.acquire()
        
 
print("%s mutex A" % self.name)
        time.sleep(1)
        mutexB.acquire()
        print("%s mutex B" % self.name)
        mutexA.release()
        mutexB.release()
    def f2(self):
        mutexB.acquire()
        print("%s mutex B" % self.name)
        time.sleep(1)
        mutexA.acquire()
        
 
print("%s mutex A" % self.name)
        mutexA.release()
        mutexB.release()
if __name__ == "__main__":
    for i in range(10):
        t=MyThread()
        t.start()奧

遞歸鎖，RLock，可以連續acquire()多次。RLock內部有一個計數器，每acquire()一次計數器加1,只要計數不為0就不能被其他線程搶到。

from threading import Thread,RLock
import time
mutexB
 
=mutexA=RLock()

class MyThread(Thread):
    def __init__(self):
        super().__init__()
    def run(self):
        self.f1()
        self.f2()
    def f1(self):
        mutexA.acquire()
        print("%s mutex A" % self.name)
        time.sleep(1)
        mutexB.acquire()
        print("%s mutex B" % self.name)
        mutexA.release()
        mutexB.release()
    def f2(self):
        mutexB.acquire()
        print("%s mutex B" % self.name)
        time.sleep(1)
        mutexA.acquire()
        print("%s mutex A" % self.name)
        mutexA.release()
        mutexB.release()
if __name__ == "__main__":
    for i in range(10):
        t=MyThread()
        t.start()

死鎖與遞歸鎖