From 36fc34993ddeb5e2d744e9ef17453a66beb4410b Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Sat, 13 Aug 2011 15:39:09 +0200
Subject: [PATCH] Lock fairness test: check that fair ReentrantReadWriteLocks
don't allow writers to starve. If this test passes on Java 5 and 6, we can
get rid of SynchronizedDatabaseComponent and merge
ReadWriteLockDatabaseComponent with DatabaseComponentImpl.
---
test/build.xml | 1 +
test/net/sf/briar/LockFairnessTest.java | 81 +++++++++++++++++++++++++
2 files changed, 82 insertions(+)
create mode 100644 test/net/sf/briar/LockFairnessTest.java
diff --git a/test/build.xml b/test/build.xml
index 1036f8f05f..67ff69ddcb 100644
--- a/test/build.xml
+++ b/test/build.xml
@@ -14,6 +14,7 @@
<path refid='util-classes'/>
</classpath>
<test name='net.sf.briar.FileReadWriteTest'/>
+ <test name='net.sf.briar.LockFairnessTest'/>
<test name='net.sf.briar.crypto.CounterModeTest'/>
<test name='net.sf.briar.db.BasicH2Test'/>
<test name='net.sf.briar.db.DatabaseCleanerImplTest'/>
diff --git a/test/net/sf/briar/LockFairnessTest.java b/test/net/sf/briar/LockFairnessTest.java
new file mode 100644
index 0000000000..57a6daed16
--- /dev/null
+++ b/test/net/sf/briar/LockFairnessTest.java
@@ -0,0 +1,81 @@
+package net.sf.briar;
+
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+import junit.framework.TestCase;
+
+import org.junit.Test;
+
+public class LockFairnessTest extends TestCase {
+
+ @Test
+ public void testWritersDoNotStarevWithFairLocks() throws Exception {
+ // Create a fair fair read-write lock
+ ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
+ // Create a ton of reader threads that repeatedly acquire the read lock,
+ // sleep for a few ms and release the lock
+ Thread[] readers = new Thread[20];
+ for(int i = 0; i < readers.length; i++) {
+ readers[i] = new ReaderThread(lock);
+ }
+ // Stagger the start times of the readers so they release the read lock
+ // at different times
+ for(int i = 0; i < readers.length; i++) {
+ readers[i].start();
+ Thread.sleep(7);
+ }
+ // Create a writer thread, which should be able to acquire the lock
+ WriterThread writer = new WriterThread(lock);
+ writer.start();
+ Thread.sleep(1000);
+ // The writer should have acquired the lock
+ assertTrue(writer.acquiredLock);
+ // Stop the readers
+ for(int i = 0; i < readers.length; i++) readers[i].interrupt();
+ }
+
+ private static class ReaderThread extends Thread {
+
+ private final ReentrantReadWriteLock lock;
+
+ private ReaderThread(ReentrantReadWriteLock lock) {
+ this.lock = lock;
+ }
+
+ @Override
+ public void run() {
+ try {
+ while(true) {
+ lock.readLock().lock();
+ try {
+ Thread.sleep(13);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+ } catch(InterruptedException quit) {
+ return;
+ }
+ }
+ }
+
+ private static class WriterThread extends Thread {
+
+ private final ReentrantReadWriteLock lock;
+ private volatile boolean acquiredLock = false;
+
+ private WriterThread(ReentrantReadWriteLock lock) {
+ this.lock = lock;
+ }
+
+ @Override
+ public void run() {
+ lock.writeLock().lock();
+ try {
+ acquiredLock = true;
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+ }
+}
--
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