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23 
24 /* @test
25  * @bug 8024833
26  * @summary Tests interruption of threads mapping sections of a file channel in
27  *   an attempt to deadlock due to nesting of begin calls.
28  */
29 import java.io.IOException;
30 import java.nio.ByteBuffer;
31 import java.nio.channels.*;
32 import java.nio.channels.FileChannel.MapMode;
33 import java.nio.file.*;
34 import java.util.concurrent.Semaphore;
35 import static java.nio.file.StandardOpenOption.*;
36 
37 public class InterruptMapDeadlock {
38 
39     static class Mapper extends Thread {
40         final FileChannel fc;
41         final Semaphore gate;
42         volatile Exception exception;
43 
Mapper(FileChannel fc, Semaphore gate)44         Mapper(FileChannel fc, Semaphore gate) {
45             this.fc = fc;
46             this.gate = gate;
47         }
48 
49         @Override
run()50         public void run() {
51             try {
52                 gate.acquireUninterruptibly();
53                 fc.map(MapMode.READ_ONLY, 0, 1);
54                 throw new Exception("Map succeeded");
55             } catch (IOException x) {
56                 System.out.println(x.getClass() + " (expected)");
57             } catch (Exception unexpected) {
58                 this.exception = unexpected;
59             }
60         }
61 
exception()62         Exception exception() {
63             return exception;
64         }
65 
startMapper(FileChannel fc, Semaphore gate)66         static Mapper startMapper(FileChannel fc, Semaphore gate) {
67             Mapper r = new Mapper(fc, gate);
68             r.setDaemon(true);
69             r.start();
70             return r;
71         }
72     }
73 
74     static class Interruptor extends Thread {
75 
76         final Mapper[] mappers;
77         final Semaphore gate;
78 
Interruptor(Mapper[] mappers, Semaphore gate)79         Interruptor(Mapper[] mappers, Semaphore gate) {
80             this.mappers = mappers;
81             this.gate = gate;
82         }
83 
run()84         public void run() {
85             gate.release(mappers.length);
86             for (Mapper m : mappers) {
87                 m.interrupt();
88             }
89         }
90     }
91     // the number of mapper threads to start
92     private static final int MAPPER_COUNT = 4;
93 
main(String[] args)94     public static void main(String[] args) throws Exception {
95         Path file = Paths.get("data.txt");
96         FileChannel.open(file, CREATE, TRUNCATE_EXISTING, WRITE).close();
97 
98         Mapper[] mappers = new Mapper[MAPPER_COUNT];
99 
100         for (int i=1; i<=20; i++) {
101             System.out.format("Iteration: %s%n", i);
102 
103             FileChannel fc = FileChannel.open(file);
104             boolean failed = false;
105 
106             Semaphore gate = new Semaphore(0);
107             // start mapper threads
108             for (int j=0; j<MAPPER_COUNT; j++) {
109                 mappers[j] = Mapper.startMapper(fc, gate);
110             }
111 
112             // interrupt and wait for the mappers to terminate
113             Interruptor interruptor = new Interruptor(mappers, gate);
114             interruptor.start();
115             try {
116                 interruptor.join(10000);
117                 if (interruptor.isAlive()) {
118                     System.err.println("Interruptor thread did not terminate:");
119                     Throwable t = new Exception("Stack trace");
120                     t.setStackTrace(interruptor.getStackTrace());
121                     t.printStackTrace();
122                     failed = true;
123                 }
124             } catch (InterruptedException x) {
125                 System.err.println("Main thread was interrupted");
126                 failed = true;
127             }
128 
129             for (Mapper m: mappers) {
130                 try {
131                     m.join(10000);
132                     Exception e = m.exception();
133                     if (e != null) {
134                         System.err.println("Mapper thread failed with: " + e);
135                         failed = true;
136                     } else if (m.isAlive()) {
137                         System.err.println("Mapper thread did not terminate:");
138                         Throwable t = new Exception("Stack trace");
139                         t.setStackTrace(m.getStackTrace());
140                         t.printStackTrace();
141                         failed = true;
142                     }
143                 } catch (InterruptedException x) {
144                     System.err.println("Main thread was interrupted");
145                     failed = true;
146                 }
147             }
148 
149             if (failed)
150                 throw new RuntimeException("Test failed - see log for details");
151             else
152                 fc.close();
153         }
154     }
155 }
156