/**
   * @param concurrency Concurrency.
   * @param isolation Isolation.
   * @throws GridException If test failed.
   */
  private void checkTransactionTimeout(
      GridCacheTxConcurrency concurrency, GridCacheTxIsolation isolation) throws Exception {

    boolean wasEx = false;

    GridCacheTx tx = null;

    try {
      GridCache<Integer, String> cache = grid.cache(null);

      tx = cache.txStart(concurrency, isolation, 50, 0);

      cache.put(1, "1");

      Thread.sleep(100);

      cache.put(1, "2");

      tx.commit();
    } catch (GridCacheTxOptimisticException e) {
      info("Received expected optimistic exception: " + e.getMessage());

      wasEx = true;

      tx.rollback();
    } catch (GridCacheTxTimeoutException e) {
      info("Received expected timeout exception: " + e.getMessage());

      wasEx = true;

      tx.rollback();
    }

    assert wasEx;
  }
    /** {@inheritDoc} */
    @Override
    public Integer call() throws Exception {
      GridCacheTx tx = CU.txStartInternal(ctx, latchView, PESSIMISTIC, REPEATABLE_READ);

      try {
        GridCacheCountDownLatchValue latchVal = latchView.get(key);

        if (latchVal == null) {
          if (log.isDebugEnabled())
            log.debug("Failed to find count down latch with given name: " + name);

          assert cnt == 0;

          return cnt;
        }

        int retVal;

        if (val > 0) {
          retVal = latchVal.get() - val;

          if (retVal < 0) retVal = 0;
        } else retVal = 0;

        latchVal.set(retVal);

        latchView.put(key, latchVal);

        tx.commit();

        return retVal;
      } finally {
        tx.end();
      }
    }
  /** {@inheritDoc} */
  @Override
  public void commit() throws GridException {
    enter();

    try {
      tx.commit();
    } finally {
      leave();
    }
  }
  /**
   * @param ctx Transaction context.
   * @param key Key.
   * @throws GridException If failed.
   */
  private void unlock(TxContext ctx, Object key) throws GridException {
    if (ctx.unlocked(key)) { // Finish transaction if last key is unlocked.
      txCtx.remove();

      GridCacheTx tx = cache.tx();

      assert tx != null;

      try {
        tx.commit();
      } finally {
        tx.close();
      }

      assert cache.tx() == null;
    }
  }