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41 import java.util.concurrent.CyclicBarrier  ;
42 import java.util.concurrent.BrokenBarrierException ;
43 import java.util.concurrent.locks.Lock ;
44 import java.util.concurrent.locks.ReentrantLock ;
45 import java.io.IOException ;
46
47
55 public class Deadlock {
56 public static void main(String [] argv) {
57 Deadlock dl = new Deadlock();
58
59 ThreadMonitor monitor = new ThreadMonitor();
61 boolean found = false;
62 while (!found) {
63 found = monitor.findDeadlock();
64 try {
65 Thread.sleep(500);
66 } catch (InterruptedException e) {
67 System.exit(1);
68 }
69 }
70
71 System.out.println("\nPress <Enter> to exit this Deadlock program.\n");
72 waitForEnterPressed();
73 }
74
75
76 private CyclicBarrier barrier = new CyclicBarrier (6);
77 public Deadlock() {
78 DeadlockThread[] dThreads = new DeadlockThread[6];
79
80 Monitor a = new Monitor("a");
81 Monitor b = new Monitor("b");
82 Monitor c = new Monitor("c");
83 dThreads[0] = new DeadlockThread("MThread-1", a, b);
84 dThreads[1] = new DeadlockThread("MThread-2", b, c);
85 dThreads[2] = new DeadlockThread("MThread-3", c, a);
86
87 Lock d = new ReentrantLock ();
88 Lock e = new ReentrantLock ();
89 Lock f = new ReentrantLock ();
90
91 dThreads[3] = new DeadlockThread("SThread-4", d, e);
92 dThreads[4] = new DeadlockThread("SThread-5", e, f);
93 dThreads[5] = new DeadlockThread("SThread-6", f, d);
94
95 for (int i = 0; i < 6; i++) {
97 dThreads[i].setDaemon(true);
98 dThreads[i].start();
99 }
100 }
101
102 class DeadlockThread extends Thread {
103 private Lock lock1 = null;
104 private Lock lock2 = null;
105 private Monitor mon1 = null;
106 private Monitor mon2 = null;
107 private boolean useSync;
108
109 DeadlockThread(String name, Lock lock1, Lock lock2) {
110 super(name);
111 this.lock1 = lock1;
112 this.lock2 = lock2;
113 this.useSync = true;
114 }
115 DeadlockThread(String name, Monitor mon1, Monitor mon2) {
116 super(name);
117 this.mon1 = mon1;
118 this.mon2 = mon2;
119 this.useSync = false;
120 }
121 public void run() {
122 if (useSync) {
123 syncLock();
124 } else {
125 monitorLock();
126 }
127 }
128 private void syncLock() {
129 lock1.lock();
130 try {
131 try {
132 barrier.await();
133 } catch (InterruptedException e) {
134 e.printStackTrace();
135 System.exit(1);
136 } catch (BrokenBarrierException e) {
137 e.printStackTrace();
138 System.exit(1);
139 }
140 goSyncDeadlock();
141 } finally {
142 lock1.unlock();
143 }
144 }
145 private void goSyncDeadlock() {
146 try {
147 barrier.await();
148 } catch (InterruptedException e) {
149 e.printStackTrace();
150 System.exit(1);
151 } catch (BrokenBarrierException e) {
152 e.printStackTrace();
153 System.exit(1);
154 }
155 lock2.lock();
156 throw new RuntimeException ("should not reach here.");
157 }
158 private void monitorLock() {
159 synchronized (mon1) {
160 try {
161 barrier.await();
162 } catch (InterruptedException e) {
163 e.printStackTrace();
164 System.exit(1);
165 } catch (BrokenBarrierException e) {
166 e.printStackTrace();
167 System.exit(1);
168 }
169 goMonitorDeadlock();
170 }
171 }
172 private void goMonitorDeadlock() {
173 try {
174 barrier.await();
175 } catch (InterruptedException e) {
176 e.printStackTrace();
177 System.exit(1);
178 } catch (BrokenBarrierException e) {
179 e.printStackTrace();
180 System.exit(1);
181 }
182 synchronized (mon2) {
183 throw new RuntimeException (getName() + " should not reach here.");
184 }
185 }
186 }
187
188 class Monitor {
189 String name;
190 Monitor(String name) {
191 this.name = name;
192 }
193 }
194
195 private static void waitForEnterPressed() {
196 try {
197 boolean done = false;
198 while (!done) {
199 char ch = (char) System.in.read();
200 if (ch<0||ch=='\n') {
201 done = true;
202 }
203 }
204 }
205 catch (IOException e) {
206 e.printStackTrace();
207 System.exit(0);
208 }
209 }
210 }
211
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