/*

 * Copyright (c) 2018, 2019, 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.

 *

 */

#include "precompiled.hpp"

#include "gc/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/g1SATBMarkQueueSet.hpp"

#include "gc/g1/g1ThreadLocalData.hpp"

#include "gc/g1/heapRegion.hpp"

#include "gc/shared/satbMarkQueue.hpp"

#include "oops/oop.hpp"

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

G1SATBMarkQueueSet::G1SATBMarkQueueSet(BufferNode::Allocator* allocator) :

  SATBMarkQueueSet(allocator)

{}

void G1SATBMarkQueueSet::handle_zero_index_for_thread(Thread* t) {

  G1ThreadLocalData::satb_mark_queue(t).handle_zero_index();

}

SATBMarkQueue& G1SATBMarkQueueSet::satb_queue_for_thread(Thread* const t) const{

  return G1ThreadLocalData::satb_mark_queue(t);

}

// Return true if a SATB buffer entry refers to an object that

// requires marking.

//

// The entry must point into the G1 heap.  In particular, it must not

// be a NULL pointer.  NULL pointers are pre-filtered and never

// inserted into a SATB buffer.

//

// An entry that is below the NTAMS pointer for the containing heap

// region requires marking. Such an entry must point to a valid object.

//

// An entry that is at least the NTAMS pointer for the containing heap

// region might be any of the following, none of which should be marked.

//

// * A reference to an object allocated since marking started.

//   According to SATB, such objects are implicitly kept live and do

//   not need to be dealt with via SATB buffer processing.

//

// * A reference to a young generation object. Young objects are

//   handled separately and are not marked by concurrent marking.

//

// * A stale reference to a young generation object. If a young

//   generation object reference is recorded and not filtered out

//   before being moved by a young collection, the reference becomes

//   stale.

//

// * A stale reference to an eagerly reclaimed humongous object.  If a

//   humongous object is recorded and then reclaimed, the reference

//   becomes stale.

//

// The stale reference cases are implicitly handled by the NTAMS

// comparison. Because of the possibility of stale references, buffer

// processing must be somewhat circumspect and not assume entries

// in an unfiltered buffer refer to valid objects.

static inline bool requires_marking(const void* entry, G1CollectedHeap* g1h) {

  // Includes rejection of NULL pointers.

  assert(g1h->is_in_reserved(entry),

         "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry));

  HeapRegion* region = g1h->heap_region_containing(entry);

  assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry));

  if (entry >= region->next_top_at_mark_start()) {

    return false;

  }

  assert(oopDesc::is_oop(oop(entry), true /* ignore mark word */),

         "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry));

  return true;

}

static inline bool discard_entry(const void* entry, G1CollectedHeap* g1h) {

  return !requires_marking(entry, g1h) || g1h->is_marked_next((oop)entry);

}

// Workaround for not yet having std::bind.

class G1SATBMarkQueueFilterFn {

  G1CollectedHeap* _g1h;

public:

  G1SATBMarkQueueFilterFn() : _g1h(G1CollectedHeap::heap()) {}

  // Return true if entry should be filtered out (removed), false if

  // it should be retained.

  bool operator()(const void* entry) const {

    return discard_entry(entry, _g1h);

  }

};

void G1SATBMarkQueueSet::filter(SATBMarkQueue* queue) {

  apply_filter(G1SATBMarkQueueFilterFn(), queue);

}