/*

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

#include "gc_implementation/g1/heapRegionSets.hpp"

// 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.

//////////////////// FreeRegionList ////////////////////

const char* FreeRegionList::verify_region_extra(HeapRegion* hr) {

  if (hr->is_young()) {

    return "the region should not be young";

  }

  // The superclass will check that the region is empty and

  // not humongous.

  return HeapRegionLinkedList::verify_region_extra(hr);

}

//////////////////// MasterFreeRegionList ////////////////////

const char* MasterFreeRegionList::verify_region_extra(HeapRegion* hr) {

  // We should reset the RSet for parallel iteration before we add it

  // to the master free list so that it is ready when the region is

  // re-allocated.

  if (!hr->rem_set()->verify_ready_for_par_iteration()) {

    return "the region's RSet should be ready for parallel iteration";

  }

  return FreeRegionList::verify_region_extra(hr);

}

bool MasterFreeRegionList::check_mt_safety() {

  // 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(),

              hrs_ext_msg(this, "master free list MT safety protocol "

                                "at a safepoint"));

  } else {

    guarantee(Heap_lock->owned_by_self(),

              hrs_ext_msg(this, "master free list MT safety protocol "

                                "outside a safepoint"));

  }

  return FreeRegionList::check_mt_safety();

}

//////////////////// SecondaryFreeRegionList ////////////////////

bool SecondaryFreeRegionList::check_mt_safety() {

  // Secondary Free List MT safety protocol:

  // Operations on the secondary free list should always be invoked

  // while holding the SecondaryFreeList_lock.

  guarantee(SecondaryFreeList_lock->owned_by_self(),

            hrs_ext_msg(this, "secondary free list MT safety protocol"));

  return FreeRegionList::check_mt_safety();

}

//////////////////// OldRegionSet ////////////////////

const char* OldRegionSet::verify_region_extra(HeapRegion* hr) {

  if (hr->is_young()) {

    return "the region should not be young";

  }

  // The superclass will check that the region is not empty and not

  // humongous.

  return HeapRegionSet::verify_region_extra(hr);

}

//////////////////// MasterOldRegionSet ////////////////////

bool MasterOldRegionSet::check_mt_safety() {

  // 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() ||

              _phase == HRSPhaseEvacuation && FreeList_lock->owned_by_self() ||

              _phase == HRSPhaseCleanup && OldSets_lock->owned_by_self(),

              hrs_ext_msg(this, "master old set MT safety protocol "

                                "at a safepoint"));

  } else {

    guarantee(Heap_lock->owned_by_self(),

              hrs_ext_msg(this, "master old set MT safety protocol "

                                "outside a safepoint"));

  }

  return OldRegionSet::check_mt_safety();

}

//////////////////// HumongousRegionSet ////////////////////

const char* HumongousRegionSet::verify_region_extra(HeapRegion* hr) {

  if (hr->is_young()) {

    return "the region should not be young";

  }

  // The superclass will check that the region is not empty and

  // humongous.

  return HeapRegionSet::verify_region_extra(hr);

}

//////////////////// MasterHumongousRegionSet ////////////////////

bool MasterHumongousRegionSet::check_mt_safety() {

  // Master 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(),

              hrs_ext_msg(this, "master humongous set MT safety protocol "

                                "at a safepoint"));

  } else {

    guarantee(Heap_lock->owned_by_self(),

              hrs_ext_msg(this, "master humongous set MT safety protocol "

                                "outside a safepoint"));

  }

  return HumongousRegionSet::check_mt_safety();

}