view src/share/vm/gc_implementation/g1/dirtyCardQueue.cpp @ 364:919e7959392a

6742641: G1: NullPointerException during GCOld Summary: An update buffer is not processed correctly, which causes roots into the collection set not to be scanned and, hence, for the heap to be corrupted. The cause is that an object is accessed after it has been explicitly deleted, which causes a race. Reviewed-by: jcoomes, ysr
author tonyp
date Mon, 22 Sep 2008 09:56:49 -0400
parents 37f87013dfd8
children ad8c8ca4ab0f
line wrap: on
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/*
 * Copyright 2001-2007 Sun Microsystems, Inc.  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 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/_dirtyCardQueue.cpp.incl"

bool DirtyCardQueue::apply_closure(CardTableEntryClosure* cl,
                                   bool consume,
                                   size_t worker_i) {
  bool res = true;
  if (_buf != NULL) {
    res = apply_closure_to_buffer(cl, _buf, _index, _sz,
                                  consume,
                                  (int) worker_i);
    if (res && consume) _index = _sz;
  }
  return res;
}

bool DirtyCardQueue::apply_closure_to_buffer(CardTableEntryClosure* cl,
                                             void** buf,
                                             size_t index, size_t sz,
                                             bool consume,
                                             int worker_i) {
  if (cl == NULL) return true;
  for (size_t i = index; i < sz; i += oopSize) {
    int ind = byte_index_to_index((int)i);
    jbyte* card_ptr = (jbyte*)buf[ind];
    if (card_ptr != NULL) {
      // Set the entry to null, so we don't do it again (via the test
      // above) if we reconsider this buffer.
      if (consume) buf[ind] = NULL;
      if (!cl->do_card_ptr(card_ptr, worker_i)) return false;
    }
  }
  return true;
}

#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
#endif // _MSC_VER

DirtyCardQueueSet::DirtyCardQueueSet() :
  PtrQueueSet(true /*notify_when_complete*/),
  _closure(NULL),
  _shared_dirty_card_queue(this, true /*perm*/),
  _free_ids(NULL),
  _processed_buffers_mut(0), _processed_buffers_rs_thread(0)
{
  _all_active = true;
}

size_t DirtyCardQueueSet::num_par_ids() {
  return MAX2(ParallelGCThreads, (size_t)2);
}


void DirtyCardQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
                                   int max_completed_queue,
                                   Mutex* lock) {
  PtrQueueSet::initialize(cbl_mon, fl_lock, max_completed_queue);
  set_buffer_size(DCQBarrierQueueBufferSize);
  set_process_completed_threshold(DCQBarrierProcessCompletedThreshold);

  _shared_dirty_card_queue.set_lock(lock);
  _free_ids = new FreeIdSet((int) num_par_ids(), _cbl_mon);
  bool b = _free_ids->claim_perm_id(0);
  guarantee(b, "Must reserve id zero for concurrent refinement thread.");
}

void DirtyCardQueueSet::handle_zero_index_for_thread(JavaThread* t) {
  t->dirty_card_queue().handle_zero_index();
}

void DirtyCardQueueSet::set_closure(CardTableEntryClosure* closure) {
  _closure = closure;
}

void DirtyCardQueueSet::iterate_closure_all_threads(bool consume,
                                                    size_t worker_i) {
  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
  for(JavaThread* t = Threads::first(); t; t = t->next()) {
    bool b = t->dirty_card_queue().apply_closure(_closure, consume);
    guarantee(b, "Should not be interrupted.");
  }
  bool b = shared_dirty_card_queue()->apply_closure(_closure,
                                                    consume,
                                                    worker_i);
  guarantee(b, "Should not be interrupted.");
}

bool DirtyCardQueueSet::mut_process_buffer(void** buf) {

  // Used to determine if we had already claimed a par_id
  // before entering this method.
  bool already_claimed = false;

  // We grab the current JavaThread.
  JavaThread* thread = JavaThread::current();

  // We get the the number of any par_id that this thread
  // might have already claimed.
  int worker_i = thread->get_claimed_par_id();

  // If worker_i is not -1 then the thread has already claimed
  // a par_id. We make note of it using the already_claimed value
  if (worker_i != -1) {
    already_claimed = true;
  } else {

    // Otherwise we need to claim a par id
    worker_i = _free_ids->claim_par_id();

    // And store the par_id value in the thread
    thread->set_claimed_par_id(worker_i);
  }

  bool b = false;
  if (worker_i != -1) {
    b = DirtyCardQueue::apply_closure_to_buffer(_closure, buf, 0,
                                                _sz, true, worker_i);
    if (b) Atomic::inc(&_processed_buffers_mut);

    // If we had not claimed an id before entering the method
    // then we must release the id.
    if (!already_claimed) {

      // we release the id
      _free_ids->release_par_id(worker_i);

      // and set the claimed_id in the thread to -1
      thread->set_claimed_par_id(-1);
    }
  }
  return b;
}

DirtyCardQueueSet::CompletedBufferNode*
DirtyCardQueueSet::get_completed_buffer_lock(int stop_at) {
  CompletedBufferNode* nd = NULL;
  MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

  if ((int)_n_completed_buffers <= stop_at) {
    _process_completed = false;
    return NULL;
  }

  if (_completed_buffers_head != NULL) {
    nd = _completed_buffers_head;
    _completed_buffers_head = nd->next;
    if (_completed_buffers_head == NULL)
      _completed_buffers_tail = NULL;
    _n_completed_buffers--;
  }
  debug_only(assert_completed_buffer_list_len_correct_locked());
  return nd;
}

// We only do this in contexts where there is no concurrent enqueueing.
DirtyCardQueueSet::CompletedBufferNode*
DirtyCardQueueSet::get_completed_buffer_CAS() {
  CompletedBufferNode* nd = _completed_buffers_head;

  while (nd != NULL) {
    CompletedBufferNode* next = nd->next;
    CompletedBufferNode* result =
      (CompletedBufferNode*)Atomic::cmpxchg_ptr(next,
                                                &_completed_buffers_head,
                                                nd);
    if (result == nd) {
      return result;
    } else {
      nd = _completed_buffers_head;
    }
  }
  assert(_completed_buffers_head == NULL, "Loop post");
  _completed_buffers_tail = NULL;
  return NULL;
}

bool DirtyCardQueueSet::
apply_closure_to_completed_buffer_helper(int worker_i,
                                         CompletedBufferNode* nd) {
  if (nd != NULL) {
    bool b =
      DirtyCardQueue::apply_closure_to_buffer(_closure, nd->buf,
                                              nd->index, _sz,
                                              true, worker_i);
    void** buf = nd->buf;
    size_t index = nd->index;
    delete nd;
    if (b) {
      deallocate_buffer(buf);
      return true;  // In normal case, go on to next buffer.
    } else {
      enqueue_complete_buffer(buf, index, true);
      return false;
    }
  } else {
    return false;
  }
}

bool DirtyCardQueueSet::apply_closure_to_completed_buffer(int worker_i,
                                                          int stop_at,
                                                          bool with_CAS)
{
  CompletedBufferNode* nd = NULL;
  if (with_CAS) {
    guarantee(stop_at == 0, "Precondition");
    nd = get_completed_buffer_CAS();
  } else {
    nd = get_completed_buffer_lock(stop_at);
  }
  bool res = apply_closure_to_completed_buffer_helper(worker_i, nd);
  if (res) _processed_buffers_rs_thread++;
  return res;
}

void DirtyCardQueueSet::apply_closure_to_all_completed_buffers() {
  CompletedBufferNode* nd = _completed_buffers_head;
  while (nd != NULL) {
    bool b =
      DirtyCardQueue::apply_closure_to_buffer(_closure, nd->buf, 0, _sz,
                                              false);
    guarantee(b, "Should not stop early.");
    nd = nd->next;
  }
}

void DirtyCardQueueSet::abandon_logs() {
  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
  CompletedBufferNode* buffers_to_delete = NULL;
  {
    MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
    while (_completed_buffers_head != NULL) {
      CompletedBufferNode* nd = _completed_buffers_head;
      _completed_buffers_head = nd->next;
      nd->next = buffers_to_delete;
      buffers_to_delete = nd;
    }
    _n_completed_buffers = 0;
    _completed_buffers_tail = NULL;
    debug_only(assert_completed_buffer_list_len_correct_locked());
  }
  while (buffers_to_delete != NULL) {
    CompletedBufferNode* nd = buffers_to_delete;
    buffers_to_delete = nd->next;
    deallocate_buffer(nd->buf);
    delete nd;
  }
  // Since abandon is done only at safepoints, we can safely manipulate
  // these queues.
  for (JavaThread* t = Threads::first(); t; t = t->next()) {
    t->dirty_card_queue().reset();
  }
  shared_dirty_card_queue()->reset();
}


void DirtyCardQueueSet::concatenate_logs() {
  // Iterate over all the threads, if we find a partial log add it to
  // the global list of logs.  Temporarily turn off the limit on the number
  // of outstanding buffers.
  int save_max_completed_queue = _max_completed_queue;
  _max_completed_queue = max_jint;
  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
  for (JavaThread* t = Threads::first(); t; t = t->next()) {
    DirtyCardQueue& dcq = t->dirty_card_queue();
    if (dcq.size() != 0) {
      void **buf = t->dirty_card_queue().get_buf();
      // We must NULL out the unused entries, then enqueue.
      for (size_t i = 0; i < t->dirty_card_queue().get_index(); i += oopSize) {
        buf[PtrQueue::byte_index_to_index((int)i)] = NULL;
      }
      enqueue_complete_buffer(dcq.get_buf(), dcq.get_index());
      dcq.reinitialize();
    }
  }
  if (_shared_dirty_card_queue.size() != 0) {
    enqueue_complete_buffer(_shared_dirty_card_queue.get_buf(),
                            _shared_dirty_card_queue.get_index());
    _shared_dirty_card_queue.reinitialize();
  }
  // Restore the completed buffer queue limit.
  _max_completed_queue = save_max_completed_queue;
}