python避免死锁方法实例分析

 更新时间:2015年06月04日 12:43:13   作者:MaxOmnis   我要评论
这篇文章主要介绍了python避免死锁方法,较为详细的分析了死锁的成因与避免形成死锁的方法,需要的朋友可以参考下

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。

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