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Date: Tue, 5 Jun 2007 03:21:26 -0700 (PDT)
From: "Bertrand Delacretaz (JIRA)" <jira@apache.org>
To: dev@jackrabbit.apache.org
Subject: [jira] Created: (JCR-962) Deadlocks in
 ConcurrentVersioningWithTransactionsTest
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Deadlocks in ConcurrentVersioningWithTransactionsTest
-----------------------------------------------------

                 Key: JCR-962
                 URL: https://issues.apache.org/jira/browse/JCR-962
             Project: Jackrabbit
          Issue Type: Bug
          Components: core
            Reporter: Bertrand Delacretaz


Patch follows for a ConcurrentVersioningWithTransactionsTest, based on the existing ConcurrentVersioningTest but using transactions around the versioning operations.

On my macbook, running the test with CONCURRENCY = 100 and NUM_OPERATIONS = 100 causes a deadlock after a few seconds, thread dumps follow.

Note that I had to ignore StaleItemStateException (which is probably justified, due to not locking stuff IIUC) to let the threads run long enough to show the problem.

Running the test a few times showed the same locking pattern several times: some threads are locked at line 87 (session.save(), no transaction) while others are at line 93 (transaction.commit()), in testConcurrentCheckinInTransaction():

    80    public void testConcurrentCheckinInTransaction() throws RepositoryException {
    81      runTask(new Task() {
    82        public void execute(Session session, Node test) throws RepositoryException {
    83          int i = 0;
    84          try {
    85            Node n = test.addNode("test");
    86            n.addMixin(mixVersionable);
    87            session.save();
    88            for (i = 0; i < NUM_OPERATIONS / CONCURRENCY; i++) {
    89              final UserTransaction utx = new UserTransactionImpl(test.getSession());
    90              utx.begin();
    91              n.checkout();
    92              n.checkin();
    93              utx.commit();
    94            }
    95            n.checkout();
    96          } catch (Exception e) {
    97            final String threadName = Thread.currentThread().getName();
    98            final Throwable deepCause = getLevel2Cause(e);
    99            if(deepCause!=null && deepCause instanceof StaleItemStateException) {
   100              // ignore 
   101            } else {
   102              throw new RepositoryException(threadName + ", i=" + i + ":" + e.getClass().getName(), e);
   103            }
   104          }
   105        }
   106      }, CONCURRENCY);
   107    }

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