wamblee.org Git - utils/blob - support/general/src/test/java/org/wamblee/concurrency/ReadWriteLockTest.java

   1 /*
   2  * Copyright 2005-2010 the original author or authors.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package org.wamblee.concurrency;
  17
  18 import junit.framework.TestCase;
  19
  20 /**
  21  * Testing the read-write lock class. Note: in case of problems, test cases
  22  * could hang.
  23  *
  24  * @see ReadWriteLock
  25  */
  26 public class ReadWriteLockTest extends TestCase {
  27     private static final int HALF_SECOND = 500;
  28
  29     private static final int ONE_SECOND = 1000;
  30
  31     private static final int TWO_SECONDS = 2000;
  32     private ReadWriteLock lock;
  33     private int nReaders;
  34     private int nWriters;
  35
  36     /**
  37      * Constructor for ReadWriteLockTest.
  38      *
  39      * @param aName
  40      */
  41     public ReadWriteLockTest(String aName) {
  42         super(aName);
  43     }
  44
  45     private synchronized int getReaderCount() {
  46         return nReaders;
  47     }
  48
  49     private synchronized int getWriterCount() {
  50         return nWriters;
  51     }
  52
  53     synchronized void incrementReaderCount() {
  54         nReaders++;
  55     }
  56
  57     synchronized void incrementWriterCount() {
  58         nWriters++;
  59     }
  60
  61     synchronized void decrementReaderCount() {
  62         nReaders--;
  63     }
  64
  65     synchronized void decrementWriterCount() {
  66         nWriters--;
  67     }
  68
  69     /*
  70      * @see TestCase#setUp()
  71      */
  72     protected void setUp() throws Exception {
  73         super.setUp();
  74         lock = new ReadWriteLock();
  75     }
  76
  77     /*
  78      * @see TestCase#tearDown()
  79      */
  80     protected void tearDown() throws Exception {
  81         lock = null;
  82         super.tearDown();
  83     }
  84
  85     /**
  86      * Acquire and release a read lock.
  87      */
  88     public void testRead() {
  89         lock.acquireRead();
  90         lock.releaseRead();
  91     }
  92
  93     /**
  94      * Acquire and release a write lock.
  95      */
  96     public void testWrite() {
  97         lock.acquireWrite();
  98         lock.releaseWrite();
  99     }
 100
 101     /**
 102      * Verify concurrent access by multiple readers is possible.
 103      *
 104      * @throws InterruptedException
 105      *             May not occur.
 106      */
 107     public void testMultipleReaders() throws InterruptedException {
 108         Runnable runnable = new ReadLocker(lock, this, TWO_SECONDS);
 109
 110         Thread t1 = new Thread(runnable);
 111         t1.start();
 112
 113         Thread t2 = new Thread(runnable);
 114         t2.start();
 115         Thread.sleep(ONE_SECOND);
 116         assertTrue("Not enough readers!", getReaderCount() == 2);
 117         t1.join();
 118         t2.join();
 119     }
 120
 121     /**
 122      * Verify that only one writer at a time can acquire the write lock.
 123      *
 124      * @throws InterruptedException
 125      *             May not occur.
 126      */
 127     public void testSingleWriter() throws InterruptedException {
 128         WriteLocker writer = new WriteLocker(lock, this, ONE_SECOND);
 129         Thread t1 = new Thread(writer);
 130         Thread t2 = new Thread(writer);
 131
 132         t1.start();
 133         t2.start();
 134         Thread.sleep(HALF_SECOND);
 135         assertTrue("Wrong writer count: " + getWriterCount(),
 136             getWriterCount() == 1);
 137         t1.join();
 138         t2.join();
 139     }
 140
 141     /**
 142      * Verify that multiple writers cannot acquire the write lock concurrently.
 143      *
 144      * @throws InterruptedException
 145      *             May not occur.
 146      */
 147     public void testMultipleWriters() throws InterruptedException {
 148         WriteLocker writer1 = new WriteLocker(lock, this, HALF_SECOND +
 149             ONE_SECOND);
 150         WriteLocker writer2 = new WriteLocker(lock, this, ONE_SECOND);
 151         Thread t1 = new Thread(writer1);
 152         Thread t2 = new Thread(writer2);
 153
 154         t1.start();
 155         Thread.sleep(HALF_SECOND);
 156         assertTrue(getWriterCount() == 1);
 157         t2.start();
 158         Thread.sleep(HALF_SECOND);
 159         assertTrue(getWriterCount() == 1); // first writer still
 160
 161         // has the lock.
 162         Thread.sleep(ONE_SECOND);
 163
 164         // at t = 2, the second writer still must have
 165         // a lock.
 166         assertTrue(getWriterCount() == 1);
 167         t1.join();
 168         t2.join();
 169     }
 170
 171     /**
 172      * Verify that after the first reader acquires a lock, a subsequent writer
 173      * can only acquire the lock after the reader has released it.
 174      *
 175      * @throws InterruptedException
 176      *             May not occur.
 177      */
 178     public void testReadWrite1() throws InterruptedException {
 179         ReadLocker readLocker = new ReadLocker(lock, this, TWO_SECONDS);
 180         Thread t1 = new Thread(readLocker);
 181         WriteLocker writeLocker = new WriteLocker(lock, this, TWO_SECONDS);
 182         Thread t2 = new Thread(writeLocker);
 183
 184         t1.start(); // acquire read lock
 185         Thread.sleep(HALF_SECOND);
 186         assertTrue(getReaderCount() == 1);
 187         t2.start();
 188         Thread.sleep(HALF_SECOND);
 189
 190         // 1 second underway, reader still holding the
 191         // lock so write lock cannot be acquired.
 192         assertTrue(getReaderCount() == 1);
 193         assertTrue(getWriterCount() == 0);
 194         Thread.sleep(ONE_SECOND + HALF_SECOND);
 195
 196         // 2.5 seconds underway, read lock released and
 197         // write lock must be acquired.
 198         assertTrue("Wrong no. of readers: " + getReaderCount(),
 199             getReaderCount() == 0);
 200         assertTrue(getWriterCount() == 1);
 201         t1.join();
 202         t2.join();
 203     }
 204
 205     /**
 206      * Verify that when multiple readers have acquired a read lock, the writer
 207      * can only acquire the lock after all readers have released it.
 208      *
 209      * @throws InterruptedException
 210      *             May not occur.
 211      */
 212     public void testReadWrite2() throws InterruptedException {
 213         ReadLocker readLocker1 = new ReadLocker(lock, this, TWO_SECONDS +
 214             HALF_SECOND);
 215         ReadLocker readLocker2 = new ReadLocker(lock, this, TWO_SECONDS +
 216             HALF_SECOND);
 217         Thread t1 = new Thread(readLocker1);
 218         Thread t2 = new Thread(readLocker2);
 219         WriteLocker writeLocker = new WriteLocker(lock, this, TWO_SECONDS);
 220         Thread t3 = new Thread(writeLocker);
 221
 222         t1.start(); // acquire read lock [0, 2.5]
 223         Thread.sleep(ONE_SECOND);
 224         // t = 1
 225         assertTrue(getReaderCount() == 1);
 226         t2.start(); // acquire read lock [1, 3.5]
 227         Thread.sleep(HALF_SECOND);
 228         // t = 1.5
 229         assertTrue(getReaderCount() == 2);
 230         t3.start(); // write lock
 231         Thread.sleep(HALF_SECOND);
 232
 233         // 2 seconds,
 234         assertTrue(getReaderCount() == 2);
 235         assertTrue(getWriterCount() == 0);
 236         Thread.sleep(ONE_SECOND);
 237
 238         // 3 seconds underway, first read lock must
 239         // have been released.
 240         assertTrue(getReaderCount() == 1);
 241         assertTrue(getWriterCount() == 0);
 242         Thread.sleep(ONE_SECOND);
 243
 244         // 4 seconds underway, write lock must have
 245         // been acquired.
 246         assertTrue(getReaderCount() == 0);
 247         assertTrue(getWriterCount() == 1);
 248
 249         t1.join();
 250         t2.join();
 251         t3.join();
 252     }
 253
 254     /**
 255      * Verify that after a writer acquires a lock, a subsequent reader can only
 256      * acquire the lock after the writer has released it.
 257      *
 258      * @throws InterruptedException
 259      *             May not occur.
 260      */
 261     public void testReadWrite3() throws InterruptedException {
 262         ReadLocker readLocker = new ReadLocker(lock, this, TWO_SECONDS);
 263         Thread t1 = new Thread(readLocker);
 264         WriteLocker writeLocker = new WriteLocker(lock, this, TWO_SECONDS);
 265         Thread t2 = new Thread(writeLocker);
 266
 267         t2.start(); // acquire write lock
 268         Thread.sleep(HALF_SECOND);
 269         assertTrue(getWriterCount() == 1);
 270         t1.start();
 271         Thread.sleep(HALF_SECOND);
 272
 273         // 1 second underway, writer still holding the
 274         // lock so read lock cannot be acquired.
 275         assertTrue(getWriterCount() == 1);
 276         assertTrue(getReaderCount() == 0);
 277         Thread.sleep(ONE_SECOND + HALF_SECOND);
 278
 279         // 2.5 seconds underway, write lock released and
 280         // read lock must be acquired.
 281         assertTrue("Wrong no. of writers: " + getReaderCount(),
 282             getWriterCount() == 0);
 283         assertTrue(getReaderCount() == 1);
 284         t1.join();
 285         t2.join();
 286     }
 287
 288     /*
 289      * The following test cases are for testing whether or not the read write
 290      * lock checks the locking correctly. Strictly speaking, these checks
 291      * wouldn't be necessary because it involves the contract of the
 292      * ReadWriteLock which must be obeyed by users of the ReadWriteLock.
 293      * Nevertheless, this is tested anyway to be absolutely sure.
 294      */
 295
 296     /**
 297      * Acquire a read lock from one thread, release it from another. Verify that
 298      * a RuntimeException is thrown.
 299      *
 300      * @throws InterruptedException
 301      *             May not occur.
 302      */
 303     public void testReleaseReadFromWrongThread() throws InterruptedException {
 304         Thread t1 = null;
 305
 306         try {
 307             t1 = new Thread(new Runnable() {
 308                 public void run() {
 309                     ReadWriteLockTest.this.lock.acquireRead();
 310                 }
 311             });
 312             t1.start();
 313             Thread.sleep(ONE_SECOND); // wait until thread is started
 314             lock.releaseRead(); // release lock from wrong thread.
 315         } catch (RuntimeException e) {
 316             return; // ok
 317         } finally {
 318             t1.join();
 319         }
 320
 321         fail();
 322     }
 323
 324     /**
 325      * Acquire a write lock from one thread, release it from another. Verify
 326      * that a RuntimeException is thrown.
 327      *
 328      * @throws InterruptedException
 329      *             May not occur.
 330      */
 331     public void testReleaseWriteFromWrongThread() throws InterruptedException {
 332         Thread t1 = null;
 333
 334         try {
 335             t1 = new Thread(new Runnable() {
 336                 public void run() {
 337                     ReadWriteLockTest.this.lock.acquireWrite();
 338                 }
 339             });
 340             t1.start();
 341             Thread.sleep(ONE_SECOND); // wait until thread is started
 342             lock.releaseWrite(); // release lock from wrong thread.
 343         } catch (RuntimeException e) {
 344             return; // ok
 345         } finally {
 346             t1.join();
 347         }
 348
 349         fail();
 350     }
 351
 352     /**
 353      * Try to acquire a read lock multiple times. Verify that a RuntimeException
 354      * is thrown.
 355      */
 356     public void testAcquireReadTwice() {
 357         try {
 358             lock.acquireRead();
 359             lock.acquireRead();
 360         } catch (RuntimeException e) {
 361             // ok
 362             return;
 363         }
 364
 365         fail();
 366     }
 367
 368     /**
 369      * Try to acquire a write lock multiple times. Verify that a
 370      * RuntimeException is thrown.
 371      */
 372     public void testAcquireWriteTwice() {
 373         try {
 374             lock.acquireWrite();
 375             lock.acquireWrite();
 376         } catch (RuntimeException e) {
 377             return; // ok
 378         }
 379
 380         fail();
 381     }
 382
 383     /**
 384      * Acquire the lock for reading and directly afterwards acquire it for
 385      * writing. Verify that a RuntimeException is thrown.
 386      */
 387     public void testAcquireReadFollowedByWrite() {
 388         try {
 389             lock.acquireRead();
 390             lock.acquireWrite();
 391         } catch (RuntimeException e) {
 392             return; // ok
 393         }
 394
 395         fail();
 396     }
 397
 398     /**
 399      * Acquire the lock for writing and directly afterwards acquire it for
 400      * reading. Verify that a RuntimeException is thrown.
 401      */
 402     public void testAcquireWriteFollowedByRead() {
 403         try {
 404             lock.acquireWrite();
 405             lock.acquireRead();
 406         } catch (RuntimeException e) {
 407             return; // ok
 408         }
 409
 410         fail();
 411     }
 412
 413     /**
 414      * Acquire a read lock and release it as a write lock. Verify that a
 415      * RuntimeException is thrown.
 416      */
 417     public void testAcquireReadFollowedByReleaseaWrite() {
 418         try {
 419             lock.acquireRead();
 420             lock.releaseWrite();
 421         } catch (RuntimeException e) {
 422             return; // ok
 423         }
 424
 425         fail();
 426     }
 427
 428     /**
 429      * Acquire a write lock and release it as a read lock. Verify that a
 430      * RuntimeException is thrown.
 431      */
 432     public void testAcquireWriteFollowedByReleaseRead() {
 433         try {
 434             lock.acquireWrite();
 435             lock.releaseRead();
 436         } catch (RuntimeException e) {
 437             return; // ok
 438         }
 439
 440         fail();
 441     }
 442 }
 443
 444 /**
 445  * ReadLocker acquires a read lock and performs a callback when the lock as been
 446  * acquired, sleeps for a designated amount of time, releases the read lock, and
 447  * performs a callback after the lock has been released.
 448  */
 449 class ReadLocker implements Runnable {
 450     private ReadWriteLock lock;
 451     private ReadWriteLockTest lockTest;
 452     private int sleepTime;
 453
 454     public ReadLocker(ReadWriteLock aLock, ReadWriteLockTest aLockTest,
 455         int aSleepTime) {
 456         lock = aLock;
 457         lockTest = aLockTest;
 458         sleepTime = aSleepTime;
 459     }
 460
 461     public void run() {
 462         lock.acquireRead();
 463         lockTest.incrementReaderCount();
 464
 465         try {
 466             Thread.sleep(sleepTime);
 467         } catch (InterruptedException e) {
 468             throw new RuntimeException("ReadLocker thread was interrupted." +
 469                 Thread.currentThread());
 470         }
 471
 472         lock.releaseRead();
 473         lockTest.decrementReaderCount();
 474     }
 475 }
 476
 477 /**
 478  * WriteLocker acquires a write lock and performs a callback when the lock as
 479  * been acquired, sleeps for a designated amount of time, releases the write
 480  * lock, and performs a callback after the lock has been released.
 481  */
 482 class WriteLocker implements Runnable {
 483     private ReadWriteLock lock;
 484     private ReadWriteLockTest lockTest;
 485     private int sleepTime;
 486
 487     public WriteLocker(ReadWriteLock aLock, ReadWriteLockTest aLockTest,
 488         int aSleepTime) {
 489         lock = aLock;
 490         lockTest = aLockTest;
 491         sleepTime = aSleepTime;
 492     }
 493
 494     public void run() {
 495         lock.acquireWrite();
 496         lockTest.incrementWriterCount();
 497
 498         try {
 499             Thread.sleep(sleepTime);
 500         } catch (InterruptedException e) {
 501             throw new RuntimeException("WriteLocker thread was interrupted: " +
 502                 Thread.currentThread());
 503         }
 504
 505         lock.releaseWrite();
 506         lockTest.decrementWriterCount();
 507     }
 508 }