/*

 * Copyright (c) 2001, 2012, 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_implementation/g1/g1CollectedHeap.inline.hpp"

#include "gc_implementation/g1/satbQueue.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/sharedHeap.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/thread.hpp"

#include "runtime/vmThread.hpp"

void ObjPtrQueue::flush() {

  // The buffer might contain refs into the CSet. We have to filter it

  // first before we flush it, otherwise we might end up with an

  // enqueued buffer with refs into the CSet which breaks our invariants.

  filter();

  PtrQueue::flush();

}

// This method removes entries from an SATB buffer that will not be

// useful to the concurrent marking threads. An entry is removed if it

// satisfies one of the following conditions:

//

// * it points to an object outside the G1 heap (G1's concurrent

//     marking only visits objects inside the G1 heap),

// * it points to an object that has been allocated since marking

//     started (according to SATB those objects do not need to be

//     visited during marking), or

// * it points to an object that has already been marked (no need to

//     process it again).

//

// The rest of the entries will be retained and are compacted towards

// the top of the buffer. Note that, because we do not allow old

// regions in the CSet during marking, all objects on the CSet regions

// are young (eden or survivors) and therefore implicitly live. So any

// references into the CSet will be removed during filtering.

void ObjPtrQueue::filter() {

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  void** buf = _buf;

  size_t sz = _sz;

  if (buf == NULL) {

    // nothing to do

    return;

  }

  // Used for sanity checking at the end of the loop.

  debug_only(size_t entries = 0; size_t retained = 0;)

  size_t i = sz;

  size_t new_index = sz;

  while (i > _index) {

    assert(i > 0, "we should have at least one more entry to process");

    i -= oopSize;

    debug_only(entries += 1;)

    oop* p = (oop*) &buf[byte_index_to_index((int) i)];

    oop obj = *p;

    // NULL the entry so that unused parts of the buffer contain NULLs

    // at the end. If we are going to retain it we will copy it to its

    // final place. If we have retained all entries we have visited so

    // far, we'll just end up copying it to the same place.

    *p = NULL;

    bool retain = g1h->is_obj_ill(obj);

    if (retain) {

      assert(new_index > 0, "we should not have already filled up the buffer");

      new_index -= oopSize;

      assert(new_index >= i,

             "new_index should never be below i, as we alwaysr compact 'up'");

      oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];

      assert(new_p >= p, "the destination location should never be below "

             "the source as we always compact 'up'");

      assert(*new_p == NULL,

             "we should have already cleared the destination location");

      *new_p = obj;

      debug_only(retained += 1;)

    }

  }

#ifdef ASSERT

  size_t entries_calc = (sz - _index) / oopSize;

  assert(entries == entries_calc, "the number of entries we counted "

         "should match the number of entries we calculated");

  size_t retained_calc = (sz - new_index) / oopSize;

  assert(retained == retained_calc, "the number of retained entries we counted "

         "should match the number of retained entries we calculated");

#endif // ASSERT

  _index = new_index;

}

// This method will first apply the above filtering to the buffer. If

// post-filtering a large enough chunk of the buffer has been cleared

// we can re-use the buffer (instead of enqueueing it) and we can just

// allow the mutator to carry on executing using the same buffer

// instead of replacing it.

bool ObjPtrQueue::should_enqueue_buffer() {

  assert(_lock == NULL || _lock->owned_by_self(),

         "we should have taken the lock before calling this");

  // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to

  // filter the buffer given that this will remove any references into

  // the CSet as we currently assume that no such refs will appear in

  // enqueued buffers.

  // This method should only be called if there is a non-NULL buffer

  // that is full.

  assert(_index == 0, "pre-condition");

  assert(_buf != NULL, "pre-condition");

  filter();

  size_t sz = _sz;

  size_t all_entries = sz / oopSize;

  size_t retained_entries = (sz - _index) / oopSize;

  size_t perc = retained_entries * 100 / all_entries;

  bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;

  return should_enqueue;

}

void ObjPtrQueue::apply_closure(ObjectClosure* cl) {

  if (_buf != NULL) {

    apply_closure_to_buffer(cl, _buf, _index, _sz);

  }

}

void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) {

  if (_buf != NULL) {

    apply_closure_to_buffer(cl, _buf, _index, _sz);

    _index = _sz;

  }

}

void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,

                                          void** buf, size_t index, size_t sz) {

  if (cl == NULL) return;

  for (size_t i = index; i < sz; i += oopSize) {

    oop obj = (oop)buf[byte_index_to_index((int)i)];

    // There can be NULL entries because of destructors.

    if (obj != NULL) {

      cl->do_object(obj);

    }

  }

}

#ifndef PRODUCT

// Helpful for debugging

void ObjPtrQueue::print(const char* name) {

  print(name, _buf, _index, _sz);

}

void ObjPtrQueue::print(const char* name,

                        void** buf, size_t index, size_t sz) {

  gclog_or_tty->print_cr("  SATB BUFFER [%s] buf: "PTR_FORMAT" "

                         "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,

                         name, buf, index, sz);

}

#endif // PRODUCT

#ifdef ASSERT

void ObjPtrQueue::verify_oops_in_buffer() {

  if (_buf == NULL) return;

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

    oop obj = (oop)_buf[byte_index_to_index((int)i)];

    assert(obj != NULL && obj->is_oop(true /* ignore mark word */),

           "Not an oop");

  }

}

#endif

#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

SATBMarkQueueSet::SATBMarkQueueSet() :

  PtrQueueSet(), _closure(NULL), _par_closures(NULL),

  _shared_satb_queue(this, true /*perm*/) { }

void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,

                                  int process_completed_threshold,

                                  Mutex* lock) {

  PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);

  _shared_satb_queue.set_lock(lock);

  if (ParallelGCThreads > 0) {

    _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);

  }

}

void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {

  DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)

  t->satb_mark_queue().handle_zero_index();

}

#ifdef ASSERT

void SATBMarkQueueSet::dump_active_values(JavaThread* first,

                                          bool expected_active) {

  gclog_or_tty->print_cr("SATB queue active values for Java Threads");

  gclog_or_tty->print_cr(" SATB queue set: active is %s",

                         (is_active()) ? "TRUE" : "FALSE");

  gclog_or_tty->print_cr(" expected_active is %s",

                         (expected_active) ? "TRUE" : "FALSE");

  for (JavaThread* t = first; t; t = t->next()) {

    bool active = t->satb_mark_queue().is_active();

    gclog_or_tty->print_cr("  thread %s, active is %s",

                           t->name(), (active) ? "TRUE" : "FALSE");

  }

}

#endif // ASSERT

void SATBMarkQueueSet::set_active_all_threads(bool b,

                                              bool expected_active) {

  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

  JavaThread* first = Threads::first();

#ifdef ASSERT

  if (_all_active != expected_active) {

    dump_active_values(first, expected_active);

    // I leave this here as a guarantee, instead of an assert, so

    // that it will still be compiled in if we choose to uncomment

    // the #ifdef ASSERT in a product build. The whole block is

    // within an #ifdef ASSERT so the guarantee will not be compiled

    // in a product build anyway.

    guarantee(false,

              "SATB queue set has an unexpected active value");

  }

#endif // ASSERT

  _all_active = b;

  for (JavaThread* t = first; t; t = t->next()) {

#ifdef ASSERT

    bool active = t->satb_mark_queue().is_active();

    if (active != expected_active) {

      dump_active_values(first, expected_active);

      // I leave this here as a guarantee, instead of an assert, so

      // that it will still be compiled in if we choose to uncomment

      // the #ifdef ASSERT in a product build. The whole block is

      // within an #ifdef ASSERT so the guarantee will not be compiled

      // in a product build anyway.

      guarantee(false,

                "thread has an unexpected active value in its SATB queue");

    }

#endif // ASSERT

    t->satb_mark_queue().set_active(b);

  }

}

void SATBMarkQueueSet::filter_thread_buffers() {

  for(JavaThread* t = Threads::first(); t; t = t->next()) {

    t->satb_mark_queue().filter();

  }

  shared_satb_queue()->filter();

}

void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {

  _closure = closure;

}

void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {

  assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");

  _par_closures[i] = par_closure;

}

void SATBMarkQueueSet::iterate_closure_all_threads() {

  for(JavaThread* t = Threads::first(); t; t = t->next()) {

    t->satb_mark_queue().apply_closure_and_empty(_closure);

  }

  shared_satb_queue()->apply_closure_and_empty(_closure);

}

void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {

  SharedHeap* sh = SharedHeap::heap();

  int parity = sh->strong_roots_parity();

  for(JavaThread* t = Threads::first(); t; t = t->next()) {

    if (t->claim_oops_do(true, parity)) {

      t->satb_mark_queue().apply_closure_and_empty(_par_closures[worker]);

    }

  }

  // We also need to claim the VMThread so that its parity is updated

  // otherwise the next call to Thread::possibly_parallel_oops_do inside

  // a StrongRootsScope might skip the VMThread because it has a stale

  // parity that matches the parity set by the StrongRootsScope

  //

  // Whichever worker succeeds in claiming the VMThread gets to do

  // the shared queue.

  VMThread* vmt = VMThread::vm_thread();

  if (vmt->claim_oops_do(true, parity)) {

    shared_satb_queue()->apply_closure_and_empty(_par_closures[worker]);

  }

}

bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,

                                                              int worker) {

  BufferNode* nd = NULL;

  {

    MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

    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--;

      if (_n_completed_buffers == 0) _process_completed = false;

    }

  }

  ObjectClosure* cl = (par ? _par_closures[worker] : _closure);

  if (nd != NULL) {

    void **buf = BufferNode::make_buffer_from_node(nd);

    ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);

    deallocate_buffer(buf);

    return true;

  } else {

    return false;

  }

}

void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) {

  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

  assert(cl != NULL, "pre-condition");

  BufferNode* nd = _completed_buffers_head;

  while (nd != NULL) {

    void** buf = BufferNode::make_buffer_from_node(nd);

    ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);

    nd = nd->next();

  }

}

void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) {

  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

  assert(cl != NULL, "pre-condition");

  for (JavaThread* t = Threads::first(); t; t = t->next()) {

    t->satb_mark_queue().apply_closure(cl);

  }

  shared_satb_queue()->apply_closure(cl);

}

#ifndef PRODUCT

// Helpful for debugging

#define SATB_PRINTER_BUFFER_SIZE 256

void SATBMarkQueueSet::print_all(const char* msg) {

  char buffer[SATB_PRINTER_BUFFER_SIZE];

  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

  gclog_or_tty->cr();

  gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);

  BufferNode* nd = _completed_buffers_head;

  int i = 0;

  while (nd != NULL) {

    void** buf = BufferNode::make_buffer_from_node(nd);

    jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);

    ObjPtrQueue::print(buffer, buf, 0, _sz);

    nd = nd->next();

    i += 1;

  }

  for (JavaThread* t = Threads::first(); t; t = t->next()) {

    jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());

    t->satb_mark_queue().print(buffer);

  }

  shared_satb_queue()->print("Shared");

  gclog_or_tty->cr();

}

#endif // PRODUCT

void SATBMarkQueueSet::abandon_partial_marking() {

  BufferNode* buffers_to_delete = NULL;

  {

    MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

    while (_completed_buffers_head != NULL) {

      BufferNode* nd = _completed_buffers_head;

      _completed_buffers_head = nd->next();

      nd->set_next(buffers_to_delete);

      buffers_to_delete = nd;

    }

    _completed_buffers_tail = NULL;

    _n_completed_buffers = 0;

    DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());

  }

  while (buffers_to_delete != NULL) {

    BufferNode* nd = buffers_to_delete;

    buffers_to_delete = nd->next();

    deallocate_buffer(BufferNode::make_buffer_from_node(nd));

  }

  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

  // So we can safely manipulate these queues.

  for (JavaThread* t = Threads::first(); t; t = t->next()) {

    t->satb_mark_queue().reset();

  }

 shared_satb_queue()->reset();

}