/*

 * Copyright (c) 2017, 2019, Red Hat, Inc. All rights reserved.

 *

 * 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_GC_SHENANDOAH_SHENANDOAHLOCK_HPP

#define SHARE_GC_SHENANDOAH_SHENANDOAHLOCK_HPP

#include "memory/allocation.hpp"

#include "runtime/thread.hpp"

class ShenandoahLock  {

private:

  enum LockState { unlocked = 0, locked = 1 };

  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile int));

  volatile int _state;

  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile Thread*));

  volatile Thread* _owner;

  DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, 0);

public:

  ShenandoahLock() : _state(unlocked), _owner(NULL) {};

  void lock() {

#ifdef ASSERT

    assert(_owner != Thread::current(), "reentrant locking attempt, would deadlock");

#endif

    Thread::SpinAcquire(&_state, "Shenandoah Heap Lock");

#ifdef ASSERT

    assert(_state == locked, "must be locked");

    assert(_owner == NULL, "must not be owned");

    _owner = Thread::current();

#endif

  }

  void unlock() {

#ifdef ASSERT

    assert (_owner == Thread::current(), "sanity");

    _owner = NULL;

#endif

    Thread::SpinRelease(&_state);

  }

#ifdef ASSERT

  void assert_owned_by_current_thread() {

    assert(_state == locked, "must be locked");

    assert(_owner == Thread::current(), "must be owned by current thread");

  }

  void assert_not_owned_by_current_thread() {

    assert(_owner != Thread::current(), "must be not owned by current thread");

  }

  void assert_owned_by_current_thread_or_safepoint() {

    Thread* thr = Thread::current();

    assert((_state == locked && _owner == thr) ||

           (SafepointSynchronize::is_at_safepoint() && thr->is_VM_thread()),

           "must own heap lock or by VM thread at safepoint");

  }

#endif

};

class ShenandoahLocker : public StackObj {

private:

  ShenandoahLock* const _lock;

public:

  ShenandoahLocker(ShenandoahLock* lock) : _lock(lock) {

    if (_lock != NULL) {

      _lock->lock();

    }

  }

  ~ShenandoahLocker() {

    if (_lock != NULL) {

      _lock->unlock();

    }

  }

};

#endif // SHARE_GC_SHENANDOAH_SHENANDOAHLOCK_HPP