/*
 * Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.sun.max.tele.debug.linux;

import java.util.concurrent.locks.*;

import com.sun.max.platform.*;
import com.sun.max.program.*;
import com.sun.max.tele.*;
import com.sun.max.util.*;
import com.sun.max.vm.hosted.*;

/**
 */
public final class LinuxTeleVM extends TeleVM {


    public LinuxTeleVM(BootImage bootImage, Classpath sourcepath, String[] commandLineArguments) throws BootImageException {
        super(bootImage, sourcepath, commandLineArguments);
    }

    @Override
    protected LinuxTeleProcess createTeleProcess(String[] commandLineArguments) throws BootImageException {
        return new LinuxTeleProcess(this, Platform.platform(), programFile(), commandLineArguments);
    }

    @Override
    protected LinuxTeleProcess attachToTeleProcess() throws BootImageException {
        return new LinuxTeleProcess(this, Platform.platform(), programFile(), targetLocation().id);
    }

    /**
     * Machinery required to implement transparent hand-over of the TeleVM's lock when running
     * the SingleThread on behalf of a thread holding the lock.
     */
    private static class LinuxReentrantVMLock implements VMLock {
        private ReentrantLock lock = new ReentrantLock();
        private Thread effectiveOwner = null;

        @Override
        public void lock() {
            if (effectiveOwner != null && effectiveOwner == Thread.currentThread()) {
                return;
            }
            lock.lock();
        }

        @Override
        public boolean tryLock() {
            if (effectiveOwner != null && effectiveOwner == Thread.currentThread()) {
                return true;
            }
            return lock.tryLock();
        }

        @Override
        public void unlock() {
            if (effectiveOwner != null && effectiveOwner == Thread.currentThread()) {
                return;
            }
            lock.unlock();
        }

        @Override
        public boolean isHeldByCurrentThread() {
            return (effectiveOwner != null && effectiveOwner == Thread.currentThread()) ? true : lock.isHeldByCurrentThread();
        }

        void handOverToSingleThread() {
            if (lock.isHeldByCurrentThread() && Thread.currentThread() != SingleThread.self()) {
                effectiveOwner = SingleThread.self();
            }
        }
        void handBack() {
            if (effectiveOwner != null && lock.isHeldByCurrentThread()) {
                effectiveOwner = null;
            }
        }
    }

    void handOverVMLock() {
        LinuxReentrantVMLock vmLock = (LinuxReentrantVMLock) getLock();
        vmLock.handOverToSingleThread();
    }
    void handBackVMLock() {
        LinuxReentrantVMLock vmLock = (LinuxReentrantVMLock) getLock();
        vmLock.handBack();
    }

    @Override
    protected VMLock makeVMLock() {
        return new LinuxReentrantVMLock();
    }
}