python避免死锁方法实例分析

本文实例讲述了python避免死锁方法。分享给大家供大家参考。具体分析如下:

当两个或者更多的线程在等待资源的时候就会产生死锁,两个线程相互等待。
在本文实例中 thread1 等待thread2释放block , thread2等待thtead1释放ablock,

避免死锁的原则:

1. 一定要以一个固定的顺序来取得锁,这个列子中,意味着首先要取得alock, 然后再去block

2. 一定要按照与取得锁相反的顺序释放锁,这里,应该先释放block,然后是alock

import threading ,time
a = 5
alock = threading.lock()
b = 5
block = threading.lock()
def thread1calc():
print “thread1 acquiring lock a”
alock.acquire()
time.sleep(5)
print “thread1 acquiring lock b”
block.acquire()
a+=5
b+=5
print “thread1 releasing both locks”
block.release()
alock.release()
def thread2calc():
print “thread2 acquiring lock b”
block.acquire()
time.sleep(5)
print “thread2 acquiring lock a”
alock.acquire()
time.sleep(5)
a+=10
b+=10
print “thread2 releasing both locks”
block.release()
alock.release()
t = threading.thread(target = thread1calc)
t.setdaemon(1)
t.start()
t = threading.thread(target = thread2calc)
t.setdaemon(2)
t.start()
while 1:
time.sleep(300)

输出:

thread1 acquiring lock a
thread2 acquiring lock b
thread1 acquiring lock b
thread2 acquiring lock a

希望本文所述对大家的python程序设计有所帮助。