/*

 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

# include "incls/_precompiled.incl"

# include "incls/_ptrQueue.cpp.incl"

PtrQueue::PtrQueue(PtrQueueSet* qset_, bool perm) :

  _qset(qset_), _buf(NULL), _index(0), _active(false),

  _perm(perm), _lock(NULL)

{}

void PtrQueue::flush() {

  if (!_perm && _buf != NULL) {

    if (_index == _sz) {

      // No work to do.

      qset()->deallocate_buffer(_buf);

    } else {

      // We must NULL out the unused entries, then enqueue.

      for (size_t i = 0; i < _index; i += oopSize) {

        _buf[byte_index_to_index((int)i)] = NULL;

      }

      qset()->enqueue_complete_buffer(_buf);

    }

    _buf = NULL;

    _index = 0;

  }

}

static int byte_index_to_index(int ind) {

  assert((ind % oopSize) == 0, "Invariant.");

  return ind / oopSize;

}

static int index_to_byte_index(int byte_ind) {

  return byte_ind * oopSize;

}

void PtrQueue::enqueue_known_active(void* ptr) {

  assert(0 <= _index && _index <= _sz, "Invariant.");

  assert(_index == 0 || _buf != NULL, "invariant");

  while (_index == 0) {

    handle_zero_index();

  }

  assert(_index > 0, "postcondition");

  _index -= oopSize;

  _buf[byte_index_to_index((int)_index)] = ptr;

  assert(0 <= _index && _index <= _sz, "Invariant.");

}

void PtrQueue::locking_enqueue_completed_buffer(void** buf) {

  assert(_lock->owned_by_self(), "Required.");

  _lock->unlock();

  qset()->enqueue_complete_buffer(buf);

  // We must relock only because the caller will unlock, for the normal

  // case.

  _lock->lock_without_safepoint_check();

}

PtrQueueSet::PtrQueueSet(bool notify_when_complete) :

  _max_completed_queue(0),

  _cbl_mon(NULL), _fl_lock(NULL),

  _notify_when_complete(notify_when_complete),

  _sz(0),

  _completed_buffers_head(NULL),

  _completed_buffers_tail(NULL),

  _n_completed_buffers(0),

  _process_completed_threshold(0), _process_completed(false),

  _buf_free_list(NULL), _buf_free_list_sz(0)

{

  _fl_owner = this;

}

void** PtrQueueSet::allocate_buffer() {

  assert(_sz > 0, "Didn't set a buffer size.");

  MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);

  if (_fl_owner->_buf_free_list != NULL) {

    void** res = _fl_owner->_buf_free_list;

    _fl_owner->_buf_free_list = (void**)_fl_owner->_buf_free_list[0];

    _fl_owner->_buf_free_list_sz--;

    // Just override the next pointer with NULL, just in case we scan this part

    // of the buffer.

    res[0] = NULL;

    return res;

  } else {

    return NEW_C_HEAP_ARRAY(void*, _sz);

  }

}

void PtrQueueSet::deallocate_buffer(void** buf) {

  assert(_sz > 0, "Didn't set a buffer size.");

  MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);

  buf[0] = (void*)_fl_owner->_buf_free_list;

  _fl_owner->_buf_free_list = buf;

  _fl_owner->_buf_free_list_sz++;

}

void PtrQueueSet::reduce_free_list() {

  // For now we'll adopt the strategy of deleting half.

  MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);

  size_t n = _buf_free_list_sz / 2;

  while (n > 0) {

    assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");

    void** head = _buf_free_list;

    _buf_free_list = (void**)_buf_free_list[0];

    FREE_C_HEAP_ARRAY(void*,head);

    n--;

  }

}

void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index, bool ignore_max_completed) {

  // I use explicit locking here because there's a bailout in the middle.

  _cbl_mon->lock_without_safepoint_check();

  Thread* thread = Thread::current();

  assert( ignore_max_completed ||

          thread->is_Java_thread() ||

          SafepointSynchronize::is_at_safepoint(),

          "invariant" );

  ignore_max_completed = ignore_max_completed || !thread->is_Java_thread();

  if (!ignore_max_completed && _max_completed_queue > 0 &&

      _n_completed_buffers >= (size_t) _max_completed_queue) {

    _cbl_mon->unlock();

    bool b = mut_process_buffer(buf);

    if (b) {

      deallocate_buffer(buf);

      return;

    }

    // Otherwise, go ahead and enqueue the buffer.  Must reaquire the lock.

    _cbl_mon->lock_without_safepoint_check();

  }

  // Here we still hold the _cbl_mon.

  CompletedBufferNode* cbn = new CompletedBufferNode;

  cbn->buf = buf;

  cbn->next = NULL;

  cbn->index = index;

  if (_completed_buffers_tail == NULL) {

    assert(_completed_buffers_head == NULL, "Well-formedness");

    _completed_buffers_head = cbn;

    _completed_buffers_tail = cbn;

  } else {

    _completed_buffers_tail->next = cbn;

    _completed_buffers_tail = cbn;

  }

  _n_completed_buffers++;

  if (!_process_completed &&

      _n_completed_buffers >= _process_completed_threshold) {

    _process_completed = true;

    if (_notify_when_complete)

      _cbl_mon->notify_all();

  }

  debug_only(assert_completed_buffer_list_len_correct_locked());

  _cbl_mon->unlock();

}

int PtrQueueSet::completed_buffers_list_length() {

  int n = 0;

  CompletedBufferNode* cbn = _completed_buffers_head;

  while (cbn != NULL) {

    n++;

    cbn = cbn->next;

  }

  return n;

}

void PtrQueueSet::assert_completed_buffer_list_len_correct() {

  MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

  assert_completed_buffer_list_len_correct_locked();

}

void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {

  guarantee((size_t)completed_buffers_list_length() ==  _n_completed_buffers,

            "Completed buffer length is wrong.");

}

void PtrQueueSet::set_buffer_size(size_t sz) {

  assert(_sz == 0 && sz > 0, "Should be called only once.");

  _sz = sz * oopSize;

}

void PtrQueueSet::set_process_completed_threshold(size_t sz) {

  _process_completed_threshold = sz;

}

// Merge lists of buffers. Notify waiting threads if the length of the list

// exceeds threshold. The source queue is emptied as a result. The queues

// must share the monitor.

void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {

  assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");

  MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

  if (_completed_buffers_tail == NULL) {

    assert(_completed_buffers_head == NULL, "Well-formedness");

    _completed_buffers_head = src->_completed_buffers_head;

    _completed_buffers_tail = src->_completed_buffers_tail;

  } else {

    assert(_completed_buffers_head != NULL, "Well formedness");

    if (src->_completed_buffers_head != NULL) {

      _completed_buffers_tail->next = src->_completed_buffers_head;

      _completed_buffers_tail = src->_completed_buffers_tail;

    }

  }

  _n_completed_buffers += src->_n_completed_buffers;

  src->_n_completed_buffers = 0;

  src->_completed_buffers_head = NULL;

  src->_completed_buffers_tail = NULL;

  assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||

         _completed_buffers_head != NULL && _completed_buffers_tail != NULL,

         "Sanity");

  if (!_process_completed &&

      _n_completed_buffers >= _process_completed_threshold) {

    _process_completed = true;

    if (_notify_when_complete)

      _cbl_mon->notify_all();

  }

}

// Merge free lists of the two queues. The free list of the source

// queue is emptied as a result. The queues must share the same

// mutex that guards free lists.

void PtrQueueSet::merge_freelists(PtrQueueSet* src) {

  assert(_fl_lock == src->_fl_lock, "Should share the same lock");

  MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);

  if (_buf_free_list != NULL) {

    void **p = _buf_free_list;

    while (*p != NULL) {

      p = (void**)*p;

    }

    *p = src->_buf_free_list;

  } else {

    _buf_free_list = src->_buf_free_list;

  }

  _buf_free_list_sz += src->_buf_free_list_sz;

  src->_buf_free_list = NULL;

  src->_buf_free_list_sz = 0;

}