ParallelTask.java

/*
 * JVSTM: a Java library for Software Transactional Memory
 * Copyright (C) 2005 INESC-ID Software Engineering Group
 * http://www.esw.inesc-id.pt
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Author's contact:
 * INESC-ID Software Engineering Group
 * Rua Alves Redol 9
 * 1000 - 029 Lisboa
 * Portugal
 */
package jvstm;


public abstract class ParallelTask<T> extends TransactionalTask<T> {

    @Override
    public T call() throws Exception {
        try {
            // parent may be null if this is a "top-level" task
            if (super.parent != null) {
                super.parent.start();
            }
            while (true) {
                Transaction tx;
                if (super.parent != null) {
                    // we force the creation of a parallel nested, otherwise it would be a linear nested
                    tx = Transaction.beginParallelNested(isReadOnly());
                } else {
                    tx = Transaction.begin(isReadOnly());
                }
                try {
                    T result = execute();
                    tx.commit();
                    tx = null;
                    return result;
                } catch(EarlyAbortException eae) {
                    tx.abort();
                    tx = null;
                    if (super.parent != null) {
                        throw eae;
                    }
                } catch (CommitException ce) {
                    final Transaction causedConflict = ce.getTransactionCausedConflict();
                    tx.abort();

                    tx = null;
                    if (causedConflict != super.parent) {
                        throw ce;
                    }
                } finally {
                    if (tx != null) {
                        tx.abort();
                    }
                }
            }
        } catch (Throwable t) {
            if (t instanceof Exception) {
                throw (Exception) t;
            } else {
                throw new RuntimeException(t);
            }
        }
    }

}