DeadLock


1   //
2   // Copyright (C) 2005 United States Government as represented by the
3   // Administrator of the National Aeronautics and Space Administration
4   // (NASA).  All Rights Reserved.
5   // 
6   // This software is distributed under the NASA Open Source Agreement
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8   // Initiative.  See the file NOSA-1.3-JPF at the top of the distribution
9   // directory tree for the complete NOSA document.
10  // 
11  // THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
12  // KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
13  // LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
14  // SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
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16  // THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
17  // DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
18  //
19  package deadlock;
20  
21  /**
22   * This example shows a simple deadlock.
23   */
24  public class Deadlock implements Runnable   {
25    /**
26     * A name for the thread.
27     */
28    String   name;
29  
30    /**
31     * A fererence to the other Deadlock object running as a seperate thread.
32     */
33    Deadlock other;
34  
35    public Deadlock (String   name) {
36      this.name = name;
37    }
38  
39    public static void main (String  [] args) {
40      Deadlock o1 = new Deadlock("A");
41      Deadlock o2 = new Deadlock("B");
42  
43      o1.other = o2;
44      o2.other = o1;
45  
46      Thread   t1 = new Thread  (o1);
47      Thread   t2 = new Thread  (o2);
48  
49      t1.start();
50      t2.start();
51    }
52  
53    public void run () {
54      while (true) {
55        System.out.println(name + " cycle start");
56        synchronized (this) {
57          other.foo();
58        }
59  
60        System.out.println(name + " cycle end");
61      }
62    }
63  
64  
65    synchronized void foo () {
66      System.out.println(name + ".foo() was called");
67    }
68  }
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