text: /*
   * 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();
  }
  