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https://issues.apache.org/jira/browse/DIRMINA-452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12532362
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Rupert Smith commented on DIRMINA-452:
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http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6612102
> IdentittyHashMap Iterator has bug in it.
> ----------------------------------------
>
> Key: DIRMINA-452
> URL: https://issues.apache.org/jira/browse/DIRMINA-452
> Project: MINA
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.1.0, 1.0.4, 1.1.1, 1.0.5,
> 1.1.2
> Environment: Java, all 1.5 and 1.6 versions at least.
> Reporter: Rupert Smith
> Fix For: 1.1.3, 2.0.0-M1
>
>
> There is a bug in IdentityHashMap Iterator which causes an infinite loop.
> This can manifest itself anywhere that the iterator.remove() method is
> called, in conjunction with the put() method. In particular this has been
> observed in the VmPipeIdleStatus checker.
> Certain sequences of puts/iterator.removes cause the map to allow put() to be
> called with a full table. The code then loops round the table forever looking
> for a free slot to add the new entry to.
> A bug report has been submitted to Sun for this problem.
> Suggested work arounds:
> Use HashMap instead of IdentityHashMap.
> Do not use the remove() method on the iterator, find all elements to remove
> in one step, then remove in another.
> Here is some sample test code that exhibits the bug in isolation. Call it
> repeatedly with n=1000, until it locks up:
> public void testRandomPutRemove(final int n)
> {
> final Map<TestElement, TestElement> idMap = new
> IdentityHashMap<TestElement, TestElement>();
> final Random r = new Random();
> final float removeProbability = r.nextFloat();
> final float addProbability = r.nextFloat();
> final Queue<String> opSequence = new LinkedList<String>();
> Runnable tester =
> new Runnable()
> {
> public void run()
> {
> for (int i = 0; i < n; i++)
> {
> if (r.nextFloat() < addProbability)
> {
> synchronized (idMap)
> {
> TestElement e = new TestElement();
> idMap.put(e, e);
> opSequence.offer("put");
> }
> }
> else
> {
> synchronized (idMap)
> {
> Iterator it = idMap.keySet().iterator();
> for (int j = 0; it.hasNext(); j++)
> {
> it.next();
> if (r.nextFloat() < removeProbability)
> {
> it.remove();
> opSequence.offer("remove " + j);
> }
> }
> }
> }
> }
> }
> };
> Thread testThread = new Thread(tester);
> testThread.start();
> try
> {
> testThread.join(5000);
> }
> catch (InterruptedException e)
> {
> fail("Test interrupted.");
> }
> if (testThread.getState() == Thread.State.RUNNABLE)
> {
> System.out.println("opSequence = " + opSequence);
> System.out.println("removeProbability = " + removeProbability);
> System.out.println("addProbability = " + addProbability);
> // Wait forever here, to give an opportunity to take thread/heap
> dumps etc.
> try
> {
> testThread.join();
> }
> catch (InterruptedException e)
> {
> // Ignore.
> }
> }
> }
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