python避免死結方法執行個體分析

python避免死結方法執行個體分析

 　　本文執行個體講述了python避免死結方法。分享給大家供大家參考。具體分析如下：

　　當兩個或者更多的線程在等待資源的時候就會產生死結，兩個線程相互等待。

　　在本文執行個體中 thread1 等待thread2釋放block , thread2等待thtead1釋放ablock，

　　避免死結的原則：

　　1. 一定要以一個固定的順序來取得鎖，這個列子中，意味著首先要取得alock, 然後再去block

　　2. 一定要按照與取得鎖相反的順序釋放鎖，這裡，應該先釋放block,然後是alock

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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)

　　輸出：

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

　　希望本文所述對大家的Python程式設計有所協助。