死锁与递归锁

最新推荐文章于 2025-07-06 16:03:34 发布

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最新推荐文章于 2025-07-06 16:03:34 发布

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原文链接：http://www.cnblogs.com/zhengyiqun1992/p/10409059.html

本文通过Python threading模块的RLock和Lock实例，详细解释了递归锁和死锁的概念。递归锁允许同一线程多次获取锁，而死锁则发生在两个或多个线程在执行过程中因争夺资源而造成的一种僵局。

递归锁

一个线程拿到锁，counter加1,该线程内又碰到加锁的情况，则counter继续加1，这期间所有其他线程都只能等待，等待该线程释放所有锁，即counter递减到0为止

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


class Mythread(Thread):

    def run(self):
        self.f1()
        self.f2()


    def f1(self):
        mutexA.acquire()
        print('%s 拿到A锁' % self.name)
        mutexB.acquire()
        print('%s 拿到B锁' % self.name)
        mutexB.release()
        mutexA.release()

    def f2(self):
        mutexB.acquire()
        print('%s 拿到B锁' % self.name)
        time.sleep(1)
        mutexA.acquire()
        print('%s 拿到A锁' % self.name)
        mutexA.release()
        mutexB.release()


if __name__ == '__main__':
    for i in range(3):
        t = Mythread()
        t.start()

死锁

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


class Mythread(Thread):

    def run(self):
        self.f1()
        self.f2()


    def f1(self):
        mutexA.acquire()
        print('%s 拿到A锁' % self.name)
        mutexB.acquire()
        print('%s 拿到B锁' % self.name)
        mutexB.release()
        mutexA.release()

    def f2(self):
        mutexB.acquire()
        print('%s 拿到B锁' % self.name)
        time.sleep(1)
        mutexA.acquire()
        print('%s 拿到A锁' % self.name)
        mutexA.release()
        mutexB.release()


if __name__ == '__main__':
    for i in range(3):
        t = Mythread()
        t.start()