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 /*

  * 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();

 }