/*

 * Copyright (c) 2011, 2018, 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/heapRegionRemSet.hpp"

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

uint FreeRegionList::_unrealistically_long_length = 0;

#ifndef PRODUCT

void HeapRegionSetBase::verify_region(HeapRegion* hr) {

  assert(hr->containing_set() == this, "Inconsistent containing set for %u", hr->hrm_index());

  assert(!hr->is_young(), "Adding young region %u", hr->hrm_index()); // currently we don't use these sets for young regions

  assert(hr->is_humongous() == regions_humongous(), "Wrong humongous state for region %u and set %s", hr->hrm_index(), name());

  assert(hr->is_free() == regions_free(), "Wrong free state for region %u and set %s", hr->hrm_index(), name());

  assert(!hr->is_free() || hr->is_empty(), "Free region %u is not empty for set %s", hr->hrm_index(), name());

  assert(!hr->is_empty() || hr->is_free() || hr->is_archive(),

         "Empty region %u is not free or archive for set %s", hr->hrm_index(), name());

}

#endif

void HeapRegionSetBase::verify() {

  // It's important that we also observe the MT safety protocol even

  // for the verification calls. If we do verification without the

  // appropriate locks and the set changes underneath our feet

  // verification might fail and send us on a wild goose chase.

  check_mt_safety();

  guarantee_heap_region_set(( is_empty() && length() == 0) ||

                            (!is_empty() && length() > 0),

                            "invariant");

}

void HeapRegionSetBase::verify_start() {

  // See comment in verify() about MT safety and verification.

  check_mt_safety();

  assert_heap_region_set(!_verify_in_progress, "verification should not be in progress");

  // Do the basic verification first before we do the checks over the regions.

  HeapRegionSetBase::verify();

  _verify_in_progress = true;

}

void HeapRegionSetBase::verify_end() {

  // See comment in verify() about MT safety and verification.

  check_mt_safety();

  assert_heap_region_set(_verify_in_progress, "verification should be in progress");

  _verify_in_progress = false;

}

void HeapRegionSetBase::print_on(outputStream* out, bool print_contents) {

  out->cr();

  out->print_cr("Set: %s (" PTR_FORMAT ")", name(), p2i(this));

  out->print_cr("  Region Assumptions");

  out->print_cr("    humongous         : %s", BOOL_TO_STR(regions_humongous()));

  out->print_cr("    free              : %s", BOOL_TO_STR(regions_free()));

  out->print_cr("  Attributes");

  out->print_cr("    length            : %14u", length());

}

HeapRegionSetBase::HeapRegionSetBase(const char* name, bool humongous, bool free, HRSMtSafeChecker* mt_safety_checker)

  : _name(name), _verify_in_progress(false),

    _is_humongous(humongous), _is_free(free), _mt_safety_checker(mt_safety_checker),

    _length(0)

{ }

void FreeRegionList::set_unrealistically_long_length(uint len) {

  guarantee(_unrealistically_long_length == 0, "should only be set once");

  _unrealistically_long_length = len;

}

void FreeRegionList::remove_all() {

  check_mt_safety();

  verify_optional();

  HeapRegion* curr = _head;

  while (curr != NULL) {

    verify_region(curr);

    HeapRegion* next = curr->next();

    curr->set_next(NULL);

    curr->set_prev(NULL);

    curr->set_containing_set(NULL);

    curr = next;

  }

  clear();

  verify_optional();

}

void FreeRegionList::add_ordered(FreeRegionList* from_list) {

  check_mt_safety();

  from_list->check_mt_safety();

  verify_optional();

  from_list->verify_optional();

  if (from_list->is_empty()) {

    return;

  }

  #ifdef ASSERT

  FreeRegionListIterator iter(from_list);

  while (iter.more_available()) {

    HeapRegion* hr = iter.get_next();

    // In set_containing_set() we check that we either set the value

    // from NULL to non-NULL or vice versa to catch bugs. So, we have

    // to NULL it first before setting it to the value.

    hr->set_containing_set(NULL);

    hr->set_containing_set(this);

  }

  #endif // ASSERT

  if (is_empty()) {

    assert_free_region_list(length() == 0 && _tail == NULL, "invariant");

    _head = from_list->_head;

    _tail = from_list->_tail;

  } else {

    HeapRegion* curr_to = _head;

    HeapRegion* curr_from = from_list->_head;

    while (curr_from != NULL) {

      while (curr_to != NULL && curr_to->hrm_index() < curr_from->hrm_index()) {

        curr_to = curr_to->next();

      }

      if (curr_to == NULL) {

        // The rest of the from list should be added as tail

        _tail->set_next(curr_from);

        curr_from->set_prev(_tail);

        curr_from = NULL;

      } else {

        HeapRegion* next_from = curr_from->next();

        curr_from->set_next(curr_to);

        curr_from->set_prev(curr_to->prev());

        if (curr_to->prev() == NULL) {

          _head = curr_from;

        } else {

          curr_to->prev()->set_next(curr_from);

        }

        curr_to->set_prev(curr_from);

        curr_from = next_from;

      }

    }

    if (_tail->hrm_index() < from_list->_tail->hrm_index()) {

      _tail = from_list->_tail;

    }

  }

  _length += from_list->length();

  from_list->clear();

  verify_optional();

  from_list->verify_optional();

}

void FreeRegionList::remove_starting_at(HeapRegion* first, uint num_regions) {

  check_mt_safety();

  assert_free_region_list(num_regions >= 1, "pre-condition");

  assert_free_region_list(!is_empty(), "pre-condition");

  verify_optional();

  DEBUG_ONLY(uint old_length = length();)

  HeapRegion* curr = first;

  uint count = 0;

  while (count < num_regions) {

    verify_region(curr);

    HeapRegion* next = curr->next();

    HeapRegion* prev = curr->prev();

    assert(count < num_regions,

           "[%s] should not come across more regions "

           "pending for removal than num_regions: %u",

           name(), num_regions);

    if (prev == NULL) {

      assert_free_region_list(_head == curr, "invariant");

      _head = next;

    } else {

      assert_free_region_list(_head != curr, "invariant");

      prev->set_next(next);

    }

    if (next == NULL) {

      assert_free_region_list(_tail == curr, "invariant");

      _tail = prev;

    } else {

      assert_free_region_list(_tail != curr, "invariant");

      next->set_prev(prev);

    }

    if (_last == curr) {

      _last = NULL;

    }

    curr->set_next(NULL);

    curr->set_prev(NULL);

    remove(curr);

    count++;

    curr = next;

  }

  assert(count == num_regions,

         "[%s] count: %u should be == num_regions: %u",

         name(), count, num_regions);

  assert(length() + num_regions == old_length,

         "[%s] new length should be consistent "

         "new length: %u old length: %u num_regions: %u",

         name(), length(), old_length, num_regions);

  verify_optional();

}

void FreeRegionList::verify() {

  // See comment in HeapRegionSetBase::verify() about MT safety and

  // verification.

  check_mt_safety();

  // This will also do the basic verification too.

  verify_start();

  verify_list();

  verify_end();

}

void FreeRegionList::clear() {

  _length = 0;

  _head = NULL;

  _tail = NULL;

  _last = NULL;

}

void FreeRegionList::verify_list() {

  HeapRegion* curr = _head;

  HeapRegion* prev1 = NULL;

  HeapRegion* prev0 = NULL;

  uint count = 0;

  size_t capacity = 0;

  uint last_index = 0;

  guarantee(_head == NULL || _head->prev() == NULL, "_head should not have a prev");

  while (curr != NULL) {

    verify_region(curr);

    count++;

    guarantee(count < _unrealistically_long_length,

              "[%s] the calculated length: %u seems very long, is there maybe a cycle? curr: " PTR_FORMAT " prev0: " PTR_FORMAT " " "prev1: " PTR_FORMAT " length: %u",

              name(), count, p2i(curr), p2i(prev0), p2i(prev1), length());

    if (curr->next() != NULL) {

      guarantee(curr->next()->prev() == curr, "Next or prev pointers messed up");

    }

    guarantee(curr->hrm_index() == 0 || curr->hrm_index() > last_index, "List should be sorted");

    last_index = curr->hrm_index();

    capacity += curr->capacity();

    prev1 = prev0;

    prev0 = curr;

    curr = curr->next();

  }

  guarantee(_tail == prev0, "Expected %s to end with %u but it ended with %u.", name(), _tail->hrm_index(), prev0->hrm_index());

  guarantee(_tail == NULL || _tail->next() == NULL, "_tail should not have a next");

  guarantee(length() == count, "%s count mismatch. Expected %u, actual %u.", name(), length(), count);

}

// Note on the check_mt_safety() methods below:

//

// Verification of the "master" heap region sets / lists that are

// maintained by G1CollectedHeap is always done during a STW pause and

// by the VM thread at the start / end of the pause. The standard

// verification methods all assert check_mt_safety(). This is

// important as it ensures that verification is done without

// concurrent updates taking place at the same time. It follows, that,

// for the "master" heap region sets / lists, the check_mt_safety()

// method should include the VM thread / STW case.

void MasterFreeRegionListMtSafeChecker::check() {

  // Master Free List MT safety protocol:

  // (a) If we're at a safepoint, operations on the master free list

  // should be invoked by either the VM thread (which will serialize

  // them) or by the GC workers while holding the

  // FreeList_lock.

  // (b) If we're not at a safepoint, operations on the master free

  // list should be invoked while holding the Heap_lock.

  if (SafepointSynchronize::is_at_safepoint()) {

    guarantee(Thread::current()->is_VM_thread() ||

              FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");

  } else {

    guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");

  }

}

void OldRegionSetMtSafeChecker::check() {

  // Master Old Set MT safety protocol:

  // (a) If we're at a safepoint, operations on the master old set

  // should be invoked:

  // - by the VM thread (which will serialize them), or

  // - by the GC workers while holding the FreeList_lock, if we're

  //   at a safepoint for an evacuation pause (this lock is taken

  //   anyway when an GC alloc region is retired so that a new one

  //   is allocated from the free list), or

  // - by the GC workers while holding the OldSets_lock, if we're at a

  //   safepoint for a cleanup pause.

  // (b) If we're not at a safepoint, operations on the master old set

  // should be invoked while holding the Heap_lock.

  if (SafepointSynchronize::is_at_safepoint()) {

    guarantee(Thread::current()->is_VM_thread()

        || FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),

        "master old set MT safety protocol at a safepoint");

  } else {

    guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");

  }

}

void HumongousRegionSetMtSafeChecker::check() {

  // Humongous Set MT safety protocol:

  // (a) If we're at a safepoint, operations on the master humongous

  // set should be invoked by either the VM thread (which will

  // serialize them) or by the GC workers while holding the

  // OldSets_lock.

  // (b) If we're not at a safepoint, operations on the master

  // humongous set should be invoked while holding the Heap_lock.

  if (SafepointSynchronize::is_at_safepoint()) {

    guarantee(Thread::current()->is_VM_thread() ||

              OldSets_lock->owned_by_self(),

              "master humongous set MT safety protocol at a safepoint");

  } else {

    guarantee(Heap_lock->owned_by_self(),

              "master humongous set MT safety protocol outside a safepoint");

  }

}