/*

 * Copyright (c) 2016, 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.

 *

 */

#ifndef SHARE_VM_GC_SHARED_REFERENCEPENDINGLISTLOCKER_HPP

#define SHARE_VM_GC_SHARED_REFERENCEPENDINGLISTLOCKER_HPP

#include "memory/allocation.hpp"

#include "runtime/basicLock.hpp"

#include "runtime/mutex.hpp"

#include "runtime/thread.hpp"

#include "utilities/exceptions.hpp"

//

// The ReferencePendingListLockerThread locks and unlocks the reference

// pending list lock on behalf a non-Java thread, typically a concurrent

// GC thread. This interface should not be directly accessed. All uses

// should instead go through the ReferencePendingListLocker, which calls

// this thread if needed.

//

class ReferencePendingListLockerThread : public JavaThread {

private:

  enum Message {

    NONE,

    LOCK,

    UNLOCK

  };

  Monitor _monitor;

  Message _message;

  ReferencePendingListLockerThread();

  static void start(JavaThread* thread, TRAPS);

  void send_message(Message message);

  void receive_and_handle_messages();

public:

  static ReferencePendingListLockerThread* create(TRAPS);

  virtual bool is_hidden_from_external_view() const;

  void lock();

  void unlock();

};

//

// The ReferencePendingListLocker is the main interface for locking and

// unlocking the reference pending list lock, which needs to be held by

// the GC when adding references to the pending list. Since this is a

// Java-level monitor it can only be locked/unlocked by a Java thread.

// For this reason there is an option to spawn a helper thread, the

// ReferencePendingListLockerThread, during initialization. If a helper

// thread is spawned all lock operations from non-Java threads will be

// delegated to the helper thread. The helper thread is typically needed

// by concurrent GCs.

//

class ReferencePendingListLocker VALUE_OBJ_CLASS_SPEC {

private:

  static bool                              _is_initialized;

  static ReferencePendingListLockerThread* _locker_thread;

  BasicLock                                _basic_lock;

public:

  static void initialize(bool needs_locker_thread, TRAPS);

  static bool is_initialized();

  static bool is_locked_by_self();

  void lock();

  void unlock();

};

#endif // SHARE_VM_GC_SHARED_REFERENCEPENDINGLISTLOCKER_HPP