concurrent_copying.cc revision 184c9dc3bfc500134fdb2fbea0a7fab290c0abb0 
1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "concurrent_copying.h"
18
19#include "gc/accounting/heap_bitmap-inl.h"
20#include "gc/accounting/space_bitmap-inl.h"
21#include "gc/space/image_space.h"
22#include "gc/space/space.h"
23#include "intern_table.h"
24#include "mirror/art_field-inl.h"
25#include "mirror/object-inl.h"
26#include "scoped_thread_state_change.h"
27#include "thread-inl.h"
28#include "thread_list.h"
29#include "well_known_classes.h"
30
31namespace art {
32namespace gc {
33namespace collector {
34
35ConcurrentCopying::ConcurrentCopying(Heap* heap, const std::string& name_prefix)
36    : GarbageCollector(heap,
37                       name_prefix + (name_prefix.empty() ? "" : " ") +
38                       "concurrent copying + mark sweep"),
39      region_space_(nullptr), gc_barrier_(new Barrier(0)), mark_queue_(2 * MB),
40      is_marking_(false), is_active_(false), is_asserting_to_space_invariant_(false),
41      heap_mark_bitmap_(nullptr), live_stack_freeze_size_(0),
42      skipped_blocks_lock_("concurrent copying bytes blocks lock", kMarkSweepMarkStackLock),
43      rb_table_(heap_->GetReadBarrierTable()),
44      force_evacuate_all_(false) {
45  static_assert(space::RegionSpace::kRegionSize == accounting::ReadBarrierTable::kRegionSize,
46                "The region space size and the read barrier table region size must match");
47  cc_heap_bitmap_.reset(new accounting::HeapBitmap(heap));
48  {
49    Thread* self = Thread::Current();
50    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
51    // Cache this so that we won't have to lock heap_bitmap_lock_ in
52    // Mark() which could cause a nested lock on heap_bitmap_lock_
53    // when GC causes a RB while doing GC or a lock order violation
54    // (class_linker_lock_ and heap_bitmap_lock_).
55    heap_mark_bitmap_ = heap->GetMarkBitmap();
56  }
57}
58
59ConcurrentCopying::~ConcurrentCopying() {
60}
61
62void ConcurrentCopying::RunPhases() {
63  CHECK(kUseBakerReadBarrier || kUseTableLookupReadBarrier);
64  CHECK(!is_active_);
65  is_active_ = true;
66  Thread* self = Thread::Current();
67  Locks::mutator_lock_->AssertNotHeld(self);
68  {
69    ReaderMutexLock mu(self, *Locks::mutator_lock_);
70    InitializePhase();
71  }
72  FlipThreadRoots();
73  {
74    ReaderMutexLock mu(self, *Locks::mutator_lock_);
75    MarkingPhase();
76  }
77  // Verify no from space refs. This causes a pause.
78  if (kEnableNoFromSpaceRefsVerification || kIsDebugBuild) {
79    TimingLogger::ScopedTiming split("(Paused)VerifyNoFromSpaceReferences", GetTimings());
80    ScopedPause pause(this);
81    CheckEmptyMarkQueue();
82    if (kVerboseMode) {
83      LOG(INFO) << "Verifying no from-space refs";
84    }
85    VerifyNoFromSpaceReferences();
86    CheckEmptyMarkQueue();
87  }
88  {
89    ReaderMutexLock mu(self, *Locks::mutator_lock_);
90    ReclaimPhase();
91  }
92  FinishPhase();
93  CHECK(is_active_);
94  is_active_ = false;
95}
96
97void ConcurrentCopying::BindBitmaps() {
98  Thread* self = Thread::Current();
99  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
100  // Mark all of the spaces we never collect as immune.
101  for (const auto& space : heap_->GetContinuousSpaces()) {
102    if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect
103        || space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect) {
104      CHECK(space->IsZygoteSpace() || space->IsImageSpace());
105      CHECK(immune_region_.AddContinuousSpace(space)) << "Failed to add space " << *space;
106      const char* bitmap_name = space->IsImageSpace() ? "cc image space bitmap" :
107          "cc zygote space bitmap";
108      // TODO: try avoiding using bitmaps for image/zygote to save space.
109      accounting::ContinuousSpaceBitmap* bitmap =
110          accounting::ContinuousSpaceBitmap::Create(bitmap_name, space->Begin(), space->Capacity());
111      cc_heap_bitmap_->AddContinuousSpaceBitmap(bitmap);
112      cc_bitmaps_.push_back(bitmap);
113    } else if (space == region_space_) {
114      accounting::ContinuousSpaceBitmap* bitmap =
115          accounting::ContinuousSpaceBitmap::Create("cc region space bitmap",
116                                                    space->Begin(), space->Capacity());
117      cc_heap_bitmap_->AddContinuousSpaceBitmap(bitmap);
118      cc_bitmaps_.push_back(bitmap);
119      region_space_bitmap_ = bitmap;
120    }
121  }
122}
123
124void ConcurrentCopying::InitializePhase() {
125  TimingLogger::ScopedTiming split("InitializePhase", GetTimings());
126  if (kVerboseMode) {
127    LOG(INFO) << "GC InitializePhase";
128    LOG(INFO) << "Region-space : " << reinterpret_cast<void*>(region_space_->Begin()) << "-"
129              << reinterpret_cast<void*>(region_space_->Limit());
130  }
131  CHECK(mark_queue_.IsEmpty());
132  immune_region_.Reset();
133  bytes_moved_.StoreRelaxed(0);
134  objects_moved_.StoreRelaxed(0);
135  if (GetCurrentIteration()->GetGcCause() == kGcCauseExplicit ||
136      GetCurrentIteration()->GetGcCause() == kGcCauseForNativeAlloc ||
137      GetCurrentIteration()->GetClearSoftReferences()) {
138    force_evacuate_all_ = true;
139  } else {
140    force_evacuate_all_ = false;
141  }
142  BindBitmaps();
143  if (kVerboseMode) {
144    LOG(INFO) << "force_evacuate_all=" << force_evacuate_all_;
145    LOG(INFO) << "Immune region: " << immune_region_.Begin() << "-" << immune_region_.End();
146    LOG(INFO) << "GC end of InitializePhase";
147  }
148}
149
150// Used to switch the thread roots of a thread from from-space refs to to-space refs.
151class ThreadFlipVisitor : public Closure {
152 public:
153  explicit ThreadFlipVisitor(ConcurrentCopying* concurrent_copying, bool use_tlab)
154      : concurrent_copying_(concurrent_copying), use_tlab_(use_tlab) {
155  }
156
157  virtual void Run(Thread* thread) OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
158    // Note: self is not necessarily equal to thread since thread may be suspended.
159    Thread* self = Thread::Current();
160    CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
161        << thread->GetState() << " thread " << thread << " self " << self;
162    if (use_tlab_ && thread->HasTlab()) {
163      if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) {
164        // This must come before the revoke.
165        size_t thread_local_objects = thread->GetThreadLocalObjectsAllocated();
166        concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread);
167        reinterpret_cast<Atomic<size_t>*>(&concurrent_copying_->from_space_num_objects_at_first_pause_)->
168            FetchAndAddSequentiallyConsistent(thread_local_objects);
169      } else {
170        concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread);
171      }
172    }
173    if (kUseThreadLocalAllocationStack) {
174      thread->RevokeThreadLocalAllocationStack();
175    }
176    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
177    thread->VisitRoots(ConcurrentCopying::ProcessRootCallback, concurrent_copying_);
178    concurrent_copying_->GetBarrier().Pass(self);
179  }
180
181 private:
182  ConcurrentCopying* const concurrent_copying_;
183  const bool use_tlab_;
184};
185
186// Called back from Runtime::FlipThreadRoots() during a pause.
187class FlipCallback : public Closure {
188 public:
189  explicit FlipCallback(ConcurrentCopying* concurrent_copying)
190      : concurrent_copying_(concurrent_copying) {
191  }
192
193  virtual void Run(Thread* thread) OVERRIDE EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_) {
194    ConcurrentCopying* cc = concurrent_copying_;
195    TimingLogger::ScopedTiming split("(Paused)FlipCallback", cc->GetTimings());
196    // Note: self is not necessarily equal to thread since thread may be suspended.
197    Thread* self = Thread::Current();
198    CHECK(thread == self);
199    Locks::mutator_lock_->AssertExclusiveHeld(self);
200    cc->region_space_->SetFromSpace(cc->rb_table_, cc->force_evacuate_all_);
201    cc->SwapStacks(self);
202    if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) {
203      cc->RecordLiveStackFreezeSize(self);
204      cc->from_space_num_objects_at_first_pause_ = cc->region_space_->GetObjectsAllocated();
205      cc->from_space_num_bytes_at_first_pause_ = cc->region_space_->GetBytesAllocated();
206    }
207    cc->is_marking_ = true;
208    if (UNLIKELY(Runtime::Current()->IsActiveTransaction())) {
209      CHECK(Runtime::Current()->IsAotCompiler());
210      TimingLogger::ScopedTiming split2("(Paused)VisitTransactionRoots", cc->GetTimings());
211      Runtime::Current()->VisitTransactionRoots(ConcurrentCopying::ProcessRootCallback, cc);
212    }
213  }
214
215 private:
216  ConcurrentCopying* const concurrent_copying_;
217};
218
219// Switch threads that from from-space to to-space refs. Forward/mark the thread roots.
220void ConcurrentCopying::FlipThreadRoots() {
221  TimingLogger::ScopedTiming split("FlipThreadRoots", GetTimings());
222  if (kVerboseMode) {
223    LOG(INFO) << "time=" << region_space_->Time();
224    region_space_->DumpNonFreeRegions(LOG(INFO));
225  }
226  Thread* self = Thread::Current();
227  Locks::mutator_lock_->AssertNotHeld(self);
228  gc_barrier_->Init(self, 0);
229  ThreadFlipVisitor thread_flip_visitor(this, heap_->use_tlab_);
230  FlipCallback flip_callback(this);
231  size_t barrier_count = Runtime::Current()->FlipThreadRoots(
232      &thread_flip_visitor, &flip_callback, this);
233  {
234    ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
235    gc_barrier_->Increment(self, barrier_count);
236  }
237  is_asserting_to_space_invariant_ = true;
238  QuasiAtomic::ThreadFenceForConstructor();
239  if (kVerboseMode) {
240    LOG(INFO) << "time=" << region_space_->Time();
241    region_space_->DumpNonFreeRegions(LOG(INFO));
242    LOG(INFO) << "GC end of FlipThreadRoots";
243  }
244}
245
246void ConcurrentCopying::SwapStacks(Thread* self) {
247  heap_->SwapStacks(self);
248}
249
250void ConcurrentCopying::RecordLiveStackFreezeSize(Thread* self) {
251  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
252  live_stack_freeze_size_ = heap_->GetLiveStack()->Size();
253}
254
255// Used to visit objects in the immune spaces.
256class ConcurrentCopyingImmuneSpaceObjVisitor {
257 public:
258  explicit ConcurrentCopyingImmuneSpaceObjVisitor(ConcurrentCopying* cc)
259      : collector_(cc) {}
260
261  void operator()(mirror::Object* obj) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
262      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
263    DCHECK(obj != nullptr);
264    DCHECK(collector_->immune_region_.ContainsObject(obj));
265    accounting::ContinuousSpaceBitmap* cc_bitmap =
266        collector_->cc_heap_bitmap_->GetContinuousSpaceBitmap(obj);
267    DCHECK(cc_bitmap != nullptr)
268        << "An immune space object must have a bitmap";
269    if (kIsDebugBuild) {
270      DCHECK(collector_->heap_->GetMarkBitmap()->Test(obj))
271          << "Immune space object must be already marked";
272    }
273    // This may or may not succeed, which is ok.
274    if (kUseBakerReadBarrier) {
275      obj->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
276    }
277    if (cc_bitmap->AtomicTestAndSet(obj)) {
278      // Already marked. Do nothing.
279    } else {
280      // Newly marked. Set the gray bit and push it onto the mark stack.
281      CHECK(!kUseBakerReadBarrier || obj->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
282      collector_->PushOntoMarkStack<true>(obj);
283    }
284  }
285
286 private:
287  ConcurrentCopying* collector_;
288};
289
290class EmptyCheckpoint : public Closure {
291 public:
292  explicit EmptyCheckpoint(ConcurrentCopying* concurrent_copying)
293      : concurrent_copying_(concurrent_copying) {
294  }
295
296  virtual void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS {
297    // Note: self is not necessarily equal to thread since thread may be suspended.
298    Thread* self = Thread::Current();
299    CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
300        << thread->GetState() << " thread " << thread << " self " << self;
301    // If thread is a running mutator, then act on behalf of the garbage collector.
302    // See the code in ThreadList::RunCheckpoint.
303    if (thread->GetState() == kRunnable) {
304      concurrent_copying_->GetBarrier().Pass(self);
305    }
306  }
307
308 private:
309  ConcurrentCopying* const concurrent_copying_;
310};
311
312// Concurrently mark roots that are guarded by read barriers and process the mark stack.
313void ConcurrentCopying::MarkingPhase() {
314  TimingLogger::ScopedTiming split("MarkingPhase", GetTimings());
315  if (kVerboseMode) {
316    LOG(INFO) << "GC MarkingPhase";
317  }
318  {
319    // Mark the image root. The WB-based collectors do not need to
320    // scan the image objects from roots by relying on the card table,
321    // but it's necessary for the RB to-space invariant to hold.
322    TimingLogger::ScopedTiming split1("VisitImageRoots", GetTimings());
323    gc::space::ImageSpace* image = heap_->GetImageSpace();
324    if (image != nullptr) {
325      mirror::ObjectArray<mirror::Object>* image_root = image->GetImageHeader().GetImageRoots();
326      mirror::Object* marked_image_root = Mark(image_root);
327      CHECK_EQ(image_root, marked_image_root) << "An image object does not move";
328      if (ReadBarrier::kEnableToSpaceInvariantChecks) {
329        AssertToSpaceInvariant(nullptr, MemberOffset(0), marked_image_root);
330      }
331    }
332  }
333  {
334    TimingLogger::ScopedTiming split2("VisitConstantRoots", GetTimings());
335    Runtime::Current()->VisitConstantRoots(ProcessRootCallback, this);
336  }
337  {
338    TimingLogger::ScopedTiming split3("VisitInternTableRoots", GetTimings());
339    Runtime::Current()->GetInternTable()->VisitRoots(ProcessRootCallback,
340                                                     this, kVisitRootFlagAllRoots);
341  }
342  {
343    TimingLogger::ScopedTiming split4("VisitClassLinkerRoots", GetTimings());
344    Runtime::Current()->GetClassLinker()->VisitRoots(ProcessRootCallback,
345                                                     this, kVisitRootFlagAllRoots);
346  }
347  {
348    // TODO: don't visit the transaction roots if it's not active.
349    TimingLogger::ScopedTiming split5("VisitNonThreadRoots", GetTimings());
350    Runtime::Current()->VisitNonThreadRoots(ProcessRootCallback, this);
351  }
352
353  // Immune spaces.
354  for (auto& space : heap_->GetContinuousSpaces()) {
355    if (immune_region_.ContainsSpace(space)) {
356      DCHECK(space->IsImageSpace() || space->IsZygoteSpace());
357      accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap();
358      ConcurrentCopyingImmuneSpaceObjVisitor visitor(this);
359      live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
360                                    reinterpret_cast<uintptr_t>(space->Limit()),
361                                    visitor);
362    }
363  }
364
365  Thread* self = Thread::Current();
366  {
367    TimingLogger::ScopedTiming split6("ProcessMarkStack", GetTimings());
368    // Process the mark stack and issue an empty check point. If the
369    // mark stack is still empty after the check point, we're
370    // done. Otherwise, repeat.
371    ProcessMarkStack();
372    size_t count = 0;
373    while (!ProcessMarkStack()) {
374      ++count;
375      if (kVerboseMode) {
376        LOG(INFO) << "Issue an empty check point. " << count;
377      }
378      IssueEmptyCheckpoint();
379    }
380    // Need to ensure the mark stack is empty before reference
381    // processing to get rid of non-reference gray objects.
382    CheckEmptyMarkQueue();
383    // Enable the GetReference slow path and disallow access to the system weaks.
384    GetHeap()->GetReferenceProcessor()->EnableSlowPath();
385    Runtime::Current()->DisallowNewSystemWeaks();
386    QuasiAtomic::ThreadFenceForConstructor();
387    // Lock-unlock the system weak locks so that there's no thread in
388    // the middle of accessing system weaks.
389    Runtime::Current()->EnsureNewSystemWeaksDisallowed();
390    // Note: Do not issue a checkpoint from here to the
391    // SweepSystemWeaks call or else a deadlock due to
392    // WaitHoldingLocks() would occur.
393    if (kVerboseMode) {
394      LOG(INFO) << "Enabled the ref proc slow path & disabled access to system weaks.";
395      LOG(INFO) << "ProcessReferences";
396    }
397    ProcessReferences(self, true);
398    CheckEmptyMarkQueue();
399    if (kVerboseMode) {
400      LOG(INFO) << "SweepSystemWeaks";
401    }
402    SweepSystemWeaks(self);
403    if (kVerboseMode) {
404      LOG(INFO) << "SweepSystemWeaks done";
405    }
406    // Because hash_set::Erase() can call the hash function for
407    // arbitrary elements in the weak intern table in
408    // InternTable::Table::SweepWeaks(), the above SweepSystemWeaks()
409    // call may have marked some objects (strings) alive. So process
410    // the mark stack here once again.
411    ProcessMarkStack();
412    CheckEmptyMarkQueue();
413    // Disable marking.
414    if (kUseTableLookupReadBarrier) {
415      heap_->rb_table_->ClearAll();
416      DCHECK(heap_->rb_table_->IsAllCleared());
417    }
418    is_mark_queue_push_disallowed_.StoreSequentiallyConsistent(1);
419    is_marking_ = false;
420    if (kVerboseMode) {
421      LOG(INFO) << "AllowNewSystemWeaks";
422    }
423    Runtime::Current()->AllowNewSystemWeaks();
424    CheckEmptyMarkQueue();
425  }
426
427  if (kVerboseMode) {
428    LOG(INFO) << "GC end of MarkingPhase";
429  }
430}
431
432void ConcurrentCopying::IssueEmptyCheckpoint() {
433  Thread* self = Thread::Current();
434  EmptyCheckpoint check_point(this);
435  ThreadList* thread_list = Runtime::Current()->GetThreadList();
436  gc_barrier_->Init(self, 0);
437  size_t barrier_count = thread_list->RunCheckpoint(&check_point);
438  // If there are no threads to wait which implys that all the checkpoint functions are finished,
439  // then no need to release the mutator lock.
440  if (barrier_count == 0) {
441    return;
442  }
443  // Release locks then wait for all mutator threads to pass the barrier.
444  Locks::mutator_lock_->SharedUnlock(self);
445  {
446    ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
447    gc_barrier_->Increment(self, barrier_count);
448  }
449  Locks::mutator_lock_->SharedLock(self);
450}
451
452mirror::Object* ConcurrentCopying::PopOffMarkStack() {
453  return mark_queue_.Dequeue();
454}
455
456template<bool kThreadSafe>
457void ConcurrentCopying::PushOntoMarkStack(mirror::Object* to_ref) {
458  CHECK_EQ(is_mark_queue_push_disallowed_.LoadRelaxed(), 0)
459      << " " << to_ref << " " << PrettyTypeOf(to_ref);
460  if (kThreadSafe) {
461    CHECK(mark_queue_.Enqueue(to_ref)) << "Mark queue overflow";
462  } else {
463    CHECK(mark_queue_.EnqueueThreadUnsafe(to_ref)) << "Mark queue overflow";
464  }
465}
466
467accounting::ObjectStack* ConcurrentCopying::GetAllocationStack() {
468  return heap_->allocation_stack_.get();
469}
470
471accounting::ObjectStack* ConcurrentCopying::GetLiveStack() {
472  return heap_->live_stack_.get();
473}
474
475inline mirror::Object* ConcurrentCopying::GetFwdPtr(mirror::Object* from_ref) {
476  DCHECK(region_space_->IsInFromSpace(from_ref));
477  LockWord lw = from_ref->GetLockWord(false);
478  if (lw.GetState() == LockWord::kForwardingAddress) {
479    mirror::Object* fwd_ptr = reinterpret_cast<mirror::Object*>(lw.ForwardingAddress());
480    CHECK(fwd_ptr != nullptr);
481    return fwd_ptr;
482  } else {
483    return nullptr;
484  }
485}
486
487// The following visitors are that used to verify that there's no
488// references to the from-space left after marking.
489class ConcurrentCopyingVerifyNoFromSpaceRefsVisitor {
490 public:
491  explicit ConcurrentCopyingVerifyNoFromSpaceRefsVisitor(ConcurrentCopying* collector)
492      : collector_(collector) {}
493
494  void operator()(mirror::Object* ref) const
495      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
496    if (ref == nullptr) {
497      // OK.
498      return;
499    }
500    collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
501    if (kUseBakerReadBarrier) {
502      if (collector_->RegionSpace()->IsInToSpace(ref)) {
503        CHECK(ref->GetReadBarrierPointer() == nullptr)
504            << "To-space ref " << ref << " " << PrettyTypeOf(ref)
505            << " has non-white rb_ptr " << ref->GetReadBarrierPointer();
506      } else {
507        CHECK(ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr() ||
508              (ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr() &&
509               collector_->IsOnAllocStack(ref)))
510            << "Non-moving/unevac from space ref " << ref << " " << PrettyTypeOf(ref)
511            << " has non-black rb_ptr " << ref->GetReadBarrierPointer()
512            << " but isn't on the alloc stack (and has white rb_ptr)."
513            << " Is it in the non-moving space="
514            << (collector_->GetHeap()->GetNonMovingSpace()->HasAddress(ref));
515      }
516    }
517  }
518
519  static void RootCallback(mirror::Object** root, void *arg, const RootInfo& /*root_info*/)
520      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
521    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
522    ConcurrentCopyingVerifyNoFromSpaceRefsVisitor visitor(collector);
523    DCHECK(root != nullptr);
524    visitor(*root);
525  }
526
527 private:
528  ConcurrentCopying* collector_;
529};
530
531class ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor {
532 public:
533  explicit ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor(ConcurrentCopying* collector)
534      : collector_(collector) {}
535
536  void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */) const
537      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
538    mirror::Object* ref =
539        obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset);
540    ConcurrentCopyingVerifyNoFromSpaceRefsVisitor visitor(collector_);
541    visitor(ref);
542  }
543  void operator()(mirror::Class* klass, mirror::Reference* ref) const
544      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
545    CHECK(klass->IsTypeOfReferenceClass());
546    this->operator()(ref, mirror::Reference::ReferentOffset(), false);
547  }
548
549 private:
550  ConcurrentCopying* collector_;
551};
552
553class ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor {
554 public:
555  explicit ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor(ConcurrentCopying* collector)
556      : collector_(collector) {}
557  void operator()(mirror::Object* obj) const
558      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
559    ObjectCallback(obj, collector_);
560  }
561  static void ObjectCallback(mirror::Object* obj, void *arg)
562      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
563    CHECK(obj != nullptr);
564    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
565    space::RegionSpace* region_space = collector->RegionSpace();
566    CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space";
567    ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor visitor(collector);
568    obj->VisitReferences<true>(visitor, visitor);
569    if (kUseBakerReadBarrier) {
570      if (collector->RegionSpace()->IsInToSpace(obj)) {
571        CHECK(obj->GetReadBarrierPointer() == nullptr)
572            << "obj=" << obj << " non-white rb_ptr " << obj->GetReadBarrierPointer();
573      } else {
574        CHECK(obj->GetReadBarrierPointer() == ReadBarrier::BlackPtr() ||
575              (obj->GetReadBarrierPointer() == ReadBarrier::WhitePtr() &&
576               collector->IsOnAllocStack(obj)))
577            << "Non-moving space/unevac from space ref " << obj << " " << PrettyTypeOf(obj)
578            << " has non-black rb_ptr " << obj->GetReadBarrierPointer()
579            << " but isn't on the alloc stack (and has white rb_ptr). Is it in the non-moving space="
580            << (collector->GetHeap()->GetNonMovingSpace()->HasAddress(obj));
581      }
582    }
583  }
584
585 private:
586  ConcurrentCopying* const collector_;
587};
588
589// Verify there's no from-space references left after the marking phase.
590void ConcurrentCopying::VerifyNoFromSpaceReferences() {
591  Thread* self = Thread::Current();
592  DCHECK(Locks::mutator_lock_->IsExclusiveHeld(self));
593  ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor visitor(this);
594  // Roots.
595  {
596    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
597    Runtime::Current()->VisitRoots(
598        ConcurrentCopyingVerifyNoFromSpaceRefsVisitor::RootCallback, this);
599  }
600  // The to-space.
601  region_space_->WalkToSpace(ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor::ObjectCallback,
602                             this);
603  // Non-moving spaces.
604  {
605    WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
606    heap_->GetMarkBitmap()->Visit(visitor);
607  }
608  // The alloc stack.
609  {
610    ConcurrentCopyingVerifyNoFromSpaceRefsVisitor ref_visitor(this);
611    for (auto* it = heap_->allocation_stack_->Begin(), *end = heap_->allocation_stack_->End();
612        it < end; ++it) {
613      mirror::Object* const obj = it->AsMirrorPtr();
614      if (obj != nullptr && obj->GetClass() != nullptr) {
615        // TODO: need to call this only if obj is alive?
616        ref_visitor(obj);
617        visitor(obj);
618      }
619    }
620  }
621  // TODO: LOS. But only refs in LOS are classes.
622}
623
624// The following visitors are used to assert the to-space invariant.
625class ConcurrentCopyingAssertToSpaceInvariantRefsVisitor {
626 public:
627  explicit ConcurrentCopyingAssertToSpaceInvariantRefsVisitor(ConcurrentCopying* collector)
628      : collector_(collector) {}
629
630  void operator()(mirror::Object* ref) const
631      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
632    if (ref == nullptr) {
633      // OK.
634      return;
635    }
636    collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
637  }
638  static void RootCallback(mirror::Object** root, void *arg, const RootInfo& /*root_info*/)
639      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
640    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
641    ConcurrentCopyingAssertToSpaceInvariantRefsVisitor visitor(collector);
642    DCHECK(root != nullptr);
643    visitor(*root);
644  }
645
646 private:
647  ConcurrentCopying* collector_;
648};
649
650class ConcurrentCopyingAssertToSpaceInvariantFieldVisitor {
651 public:
652  explicit ConcurrentCopyingAssertToSpaceInvariantFieldVisitor(ConcurrentCopying* collector)
653      : collector_(collector) {}
654
655  void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */) const
656      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
657    mirror::Object* ref =
658        obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset);
659    ConcurrentCopyingAssertToSpaceInvariantRefsVisitor visitor(collector_);
660    visitor(ref);
661  }
662  void operator()(mirror::Class* klass, mirror::Reference* /* ref */) const
663      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
664    CHECK(klass->IsTypeOfReferenceClass());
665  }
666
667 private:
668  ConcurrentCopying* collector_;
669};
670
671class ConcurrentCopyingAssertToSpaceInvariantObjectVisitor {
672 public:
673  explicit ConcurrentCopyingAssertToSpaceInvariantObjectVisitor(ConcurrentCopying* collector)
674      : collector_(collector) {}
675  void operator()(mirror::Object* obj) const
676      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
677    ObjectCallback(obj, collector_);
678  }
679  static void ObjectCallback(mirror::Object* obj, void *arg)
680      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
681    CHECK(obj != nullptr);
682    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
683    space::RegionSpace* region_space = collector->RegionSpace();
684    CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space";
685    collector->AssertToSpaceInvariant(nullptr, MemberOffset(0), obj);
686    ConcurrentCopyingAssertToSpaceInvariantFieldVisitor visitor(collector);
687    obj->VisitReferences<true>(visitor, visitor);
688  }
689
690 private:
691  ConcurrentCopying* collector_;
692};
693
694bool ConcurrentCopying::ProcessMarkStack() {
695  if (kVerboseMode) {
696    LOG(INFO) << "ProcessMarkStack. ";
697  }
698  size_t count = 0;
699  mirror::Object* to_ref;
700  while ((to_ref = PopOffMarkStack()) != nullptr) {
701    ++count;
702    DCHECK(!region_space_->IsInFromSpace(to_ref));
703    if (kUseBakerReadBarrier) {
704      DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr())
705          << " " << to_ref << " " << to_ref->GetReadBarrierPointer()
706          << " is_marked=" << IsMarked(to_ref);
707    }
708    // Scan ref fields.
709    Scan(to_ref);
710    // Mark the gray ref as white or black.
711    if (kUseBakerReadBarrier) {
712      DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr())
713          << " " << to_ref << " " << to_ref->GetReadBarrierPointer()
714          << " is_marked=" << IsMarked(to_ref);
715    }
716    if (to_ref->GetClass<kVerifyNone, kWithoutReadBarrier>()->IsTypeOfReferenceClass() &&
717        to_ref->AsReference()->GetReferent<kWithoutReadBarrier>() != nullptr &&
718        !IsInToSpace(to_ref->AsReference()->GetReferent<kWithoutReadBarrier>())) {
719      // Leave References gray so that GetReferent() will trigger RB.
720      CHECK(to_ref->AsReference()->IsEnqueued()) << "Left unenqueued ref gray " << to_ref;
721    } else {
722      if (kUseBakerReadBarrier) {
723        if (region_space_->IsInToSpace(to_ref)) {
724          // If to-space, change from gray to white.
725          bool success = to_ref->AtomicSetReadBarrierPointer(ReadBarrier::GrayPtr(),
726                                                             ReadBarrier::WhitePtr());
727          CHECK(success) << "Must succeed as we won the race.";
728          CHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr());
729        } else {
730          // If non-moving space/unevac from space, change from gray
731          // to black. We can't change gray to white because it's not
732          // safe to use CAS if two threads change values in opposite
733          // directions (A->B and B->A). So, we change it to black to
734          // indicate non-moving objects that have been marked
735          // through. Note we'd need to change from black to white
736          // later (concurrently).
737          bool success = to_ref->AtomicSetReadBarrierPointer(ReadBarrier::GrayPtr(),
738                                                             ReadBarrier::BlackPtr());
739          CHECK(success) << "Must succeed as we won the race.";
740          CHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
741        }
742      }
743    }
744    if (ReadBarrier::kEnableToSpaceInvariantChecks || kIsDebugBuild) {
745      ConcurrentCopyingAssertToSpaceInvariantObjectVisitor visitor(this);
746      visitor(to_ref);
747    }
748  }
749  // Return true if the stack was empty.
750  return count == 0;
751}
752
753void ConcurrentCopying::CheckEmptyMarkQueue() {
754  if (!mark_queue_.IsEmpty()) {
755    while (!mark_queue_.IsEmpty()) {
756      mirror::Object* obj = mark_queue_.Dequeue();
757      if (kUseBakerReadBarrier) {
758        mirror::Object* rb_ptr = obj->GetReadBarrierPointer();
759        LOG(INFO) << "On mark queue : " << obj << " " << PrettyTypeOf(obj) << " rb_ptr=" << rb_ptr
760                  << " is_marked=" << IsMarked(obj);
761      } else {
762        LOG(INFO) << "On mark queue : " << obj << " " << PrettyTypeOf(obj)
763                  << " is_marked=" << IsMarked(obj);
764      }
765    }
766    LOG(FATAL) << "mark queue is not empty";
767  }
768}
769
770void ConcurrentCopying::SweepSystemWeaks(Thread* self) {
771  TimingLogger::ScopedTiming split("SweepSystemWeaks", GetTimings());
772  ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
773  Runtime::Current()->SweepSystemWeaks(IsMarkedCallback, this);
774}
775
776void ConcurrentCopying::Sweep(bool swap_bitmaps) {
777  {
778    TimingLogger::ScopedTiming t("MarkStackAsLive", GetTimings());
779    accounting::ObjectStack* live_stack = heap_->GetLiveStack();
780    if (kEnableFromSpaceAccountingCheck) {
781      CHECK_GE(live_stack_freeze_size_, live_stack->Size());
782    }
783    heap_->MarkAllocStackAsLive(live_stack);
784    live_stack->Reset();
785  }
786  CHECK(mark_queue_.IsEmpty());
787  TimingLogger::ScopedTiming split("Sweep", GetTimings());
788  for (const auto& space : GetHeap()->GetContinuousSpaces()) {
789    if (space->IsContinuousMemMapAllocSpace()) {
790      space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace();
791      if (space == region_space_ || immune_region_.ContainsSpace(space)) {
792        continue;
793      }
794      TimingLogger::ScopedTiming split2(
795          alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", GetTimings());
796      RecordFree(alloc_space->Sweep(swap_bitmaps));
797    }
798  }
799  SweepLargeObjects(swap_bitmaps);
800}
801
802void ConcurrentCopying::SweepLargeObjects(bool swap_bitmaps) {
803  TimingLogger::ScopedTiming split("SweepLargeObjects", GetTimings());
804  RecordFreeLOS(heap_->GetLargeObjectsSpace()->Sweep(swap_bitmaps));
805}
806
807class ConcurrentCopyingClearBlackPtrsVisitor {
808 public:
809  explicit ConcurrentCopyingClearBlackPtrsVisitor(ConcurrentCopying* cc)
810      : collector_(cc) {}
811  void operator()(mirror::Object* obj) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
812      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
813    DCHECK(obj != nullptr);
814    DCHECK(collector_->heap_->GetMarkBitmap()->Test(obj)) << obj;
815    DCHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::BlackPtr()) << obj;
816    obj->SetReadBarrierPointer(ReadBarrier::WhitePtr());
817    DCHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << obj;
818  }
819
820 private:
821  ConcurrentCopying* const collector_;
822};
823
824// Clear the black ptrs in non-moving objects back to white.
825void ConcurrentCopying::ClearBlackPtrs() {
826  CHECK(kUseBakerReadBarrier);
827  TimingLogger::ScopedTiming split("ClearBlackPtrs", GetTimings());
828  ConcurrentCopyingClearBlackPtrsVisitor visitor(this);
829  for (auto& space : heap_->GetContinuousSpaces()) {
830    if (space == region_space_) {
831      continue;
832    }
833    accounting::ContinuousSpaceBitmap* mark_bitmap = space->GetMarkBitmap();
834    if (kVerboseMode) {
835      LOG(INFO) << "ClearBlackPtrs: " << *space << " bitmap: " << *mark_bitmap;
836    }
837    mark_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
838                                  reinterpret_cast<uintptr_t>(space->Limit()),
839                                  visitor);
840  }
841  space::LargeObjectSpace* large_object_space = heap_->GetLargeObjectsSpace();
842  large_object_space->GetMarkBitmap()->VisitMarkedRange(
843      reinterpret_cast<uintptr_t>(large_object_space->Begin()),
844      reinterpret_cast<uintptr_t>(large_object_space->End()),
845      visitor);
846  // Objects on the allocation stack?
847  if (ReadBarrier::kEnableReadBarrierInvariantChecks || kIsDebugBuild) {
848    size_t count = GetAllocationStack()->Size();
849    auto* it = GetAllocationStack()->Begin();
850    auto* end = GetAllocationStack()->End();
851    for (size_t i = 0; i < count; ++i, ++it) {
852      CHECK_LT(it, end);
853      mirror::Object* obj = it->AsMirrorPtr();
854      if (obj != nullptr) {
855        // Must have been cleared above.
856        CHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << obj;
857      }
858    }
859  }
860}
861
862void ConcurrentCopying::ReclaimPhase() {
863  TimingLogger::ScopedTiming split("ReclaimPhase", GetTimings());
864  if (kVerboseMode) {
865    LOG(INFO) << "GC ReclaimPhase";
866  }
867  Thread* self = Thread::Current();
868
869  {
870    // Double-check that the mark stack is empty.
871    // Note: need to set this after VerifyNoFromSpaceRef().
872    is_asserting_to_space_invariant_ = false;
873    QuasiAtomic::ThreadFenceForConstructor();
874    if (kVerboseMode) {
875      LOG(INFO) << "Issue an empty check point. ";
876    }
877    IssueEmptyCheckpoint();
878    // Disable the check.
879    is_mark_queue_push_disallowed_.StoreSequentiallyConsistent(0);
880    CheckEmptyMarkQueue();
881  }
882
883  {
884    // Record freed objects.
885    TimingLogger::ScopedTiming split2("RecordFree", GetTimings());
886    // Don't include thread-locals that are in the to-space.
887    uint64_t from_bytes = region_space_->GetBytesAllocatedInFromSpace();
888    uint64_t from_objects = region_space_->GetObjectsAllocatedInFromSpace();
889    uint64_t unevac_from_bytes = region_space_->GetBytesAllocatedInUnevacFromSpace();
890    uint64_t unevac_from_objects = region_space_->GetObjectsAllocatedInUnevacFromSpace();
891    uint64_t to_bytes = bytes_moved_.LoadSequentiallyConsistent();
892    uint64_t to_objects = objects_moved_.LoadSequentiallyConsistent();
893    if (kEnableFromSpaceAccountingCheck) {
894      CHECK_EQ(from_space_num_objects_at_first_pause_, from_objects + unevac_from_objects);
895      CHECK_EQ(from_space_num_bytes_at_first_pause_, from_bytes + unevac_from_bytes);
896    }
897    CHECK_LE(to_objects, from_objects);
898    CHECK_LE(to_bytes, from_bytes);
899    int64_t freed_bytes = from_bytes - to_bytes;
900    int64_t freed_objects = from_objects - to_objects;
901    if (kVerboseMode) {
902      LOG(INFO) << "RecordFree:"
903                << " from_bytes=" << from_bytes << " from_objects=" << from_objects
904                << " unevac_from_bytes=" << unevac_from_bytes << " unevac_from_objects=" << unevac_from_objects
905                << " to_bytes=" << to_bytes << " to_objects=" << to_objects
906                << " freed_bytes=" << freed_bytes << " freed_objects=" << freed_objects
907                << " from_space size=" << region_space_->FromSpaceSize()
908                << " unevac_from_space size=" << region_space_->UnevacFromSpaceSize()
909                << " to_space size=" << region_space_->ToSpaceSize();
910      LOG(INFO) << "(before) num_bytes_allocated=" << heap_->num_bytes_allocated_.LoadSequentiallyConsistent();
911    }
912    RecordFree(ObjectBytePair(freed_objects, freed_bytes));
913    if (kVerboseMode) {
914      LOG(INFO) << "(after) num_bytes_allocated=" << heap_->num_bytes_allocated_.LoadSequentiallyConsistent();
915    }
916  }
917
918  {
919    TimingLogger::ScopedTiming split3("ComputeUnevacFromSpaceLiveRatio", GetTimings());
920    ComputeUnevacFromSpaceLiveRatio();
921  }
922
923  {
924    TimingLogger::ScopedTiming split4("ClearFromSpace", GetTimings());
925    region_space_->ClearFromSpace();
926  }
927
928  {
929    WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
930    if (kUseBakerReadBarrier) {
931      ClearBlackPtrs();
932    }
933    Sweep(false);
934    SwapBitmaps();
935    heap_->UnBindBitmaps();
936
937    // Remove bitmaps for the immune spaces.
938    while (!cc_bitmaps_.empty()) {
939      accounting::ContinuousSpaceBitmap* cc_bitmap = cc_bitmaps_.back();
940      cc_heap_bitmap_->RemoveContinuousSpaceBitmap(cc_bitmap);
941      delete cc_bitmap;
942      cc_bitmaps_.pop_back();
943    }
944    region_space_bitmap_ = nullptr;
945  }
946
947  if (kVerboseMode) {
948    LOG(INFO) << "GC end of ReclaimPhase";
949  }
950}
951
952class ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor {
953 public:
954  explicit ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor(ConcurrentCopying* cc)
955      : collector_(cc) {}
956  void operator()(mirror::Object* ref) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
957      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
958    DCHECK(ref != nullptr);
959    DCHECK(collector_->region_space_bitmap_->Test(ref)) << ref;
960    DCHECK(collector_->region_space_->IsInUnevacFromSpace(ref)) << ref;
961    if (kUseBakerReadBarrier) {
962      DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::BlackPtr()) << ref;
963      // Clear the black ptr.
964      ref->SetReadBarrierPointer(ReadBarrier::WhitePtr());
965    }
966    size_t obj_size = ref->SizeOf();
967    size_t alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment);
968    collector_->region_space_->AddLiveBytes(ref, alloc_size);
969  }
970
971 private:
972  ConcurrentCopying* collector_;
973};
974
975// Compute how much live objects are left in regions.
976void ConcurrentCopying::ComputeUnevacFromSpaceLiveRatio() {
977  region_space_->AssertAllRegionLiveBytesZeroOrCleared();
978  ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor visitor(this);
979  region_space_bitmap_->VisitMarkedRange(reinterpret_cast<uintptr_t>(region_space_->Begin()),
980                                         reinterpret_cast<uintptr_t>(region_space_->Limit()),
981                                         visitor);
982}
983
984// Assert the to-space invariant.
985void ConcurrentCopying::AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
986                                               mirror::Object* ref) {
987  CHECK(heap_->collector_type_ == kCollectorTypeCC) << static_cast<size_t>(heap_->collector_type_);
988  if (is_asserting_to_space_invariant_) {
989    if (region_space_->IsInToSpace(ref)) {
990      // OK.
991      return;
992    } else if (region_space_->IsInUnevacFromSpace(ref)) {
993      CHECK(region_space_bitmap_->Test(ref)) << ref;
994    } else if (region_space_->IsInFromSpace(ref)) {
995      // Not OK. Do extra logging.
996      if (obj != nullptr) {
997        if (kUseBakerReadBarrier) {
998          LOG(INFO) << "holder=" << obj << " " << PrettyTypeOf(obj)
999                    << " holder rb_ptr=" << obj->GetReadBarrierPointer();
1000        } else {
1001          LOG(INFO) << "holder=" << obj << " " << PrettyTypeOf(obj);
1002        }
1003        if (region_space_->IsInFromSpace(obj)) {
1004          LOG(INFO) << "holder is in the from-space.";
1005        } else if (region_space_->IsInToSpace(obj)) {
1006          LOG(INFO) << "holder is in the to-space.";
1007        } else if (region_space_->IsInUnevacFromSpace(obj)) {
1008          LOG(INFO) << "holder is in the unevac from-space.";
1009          if (region_space_bitmap_->Test(obj)) {
1010            LOG(INFO) << "holder is marked in the region space bitmap.";
1011          } else {
1012            LOG(INFO) << "holder is not marked in the region space bitmap.";
1013          }
1014        } else {
1015          // In a non-moving space.
1016          if (immune_region_.ContainsObject(obj)) {
1017            LOG(INFO) << "holder is in the image or the zygote space.";
1018            accounting::ContinuousSpaceBitmap* cc_bitmap =
1019                cc_heap_bitmap_->GetContinuousSpaceBitmap(obj);
1020            CHECK(cc_bitmap != nullptr)
1021                << "An immune space object must have a bitmap.";
1022            if (cc_bitmap->Test(obj)) {
1023              LOG(INFO) << "holder is marked in the bit map.";
1024            } else {
1025              LOG(INFO) << "holder is NOT marked in the bit map.";
1026            }
1027          } else {
1028            LOG(INFO) << "holder is in a non-moving (or main) space.";
1029            accounting::ContinuousSpaceBitmap* mark_bitmap =
1030                heap_mark_bitmap_->GetContinuousSpaceBitmap(obj);
1031            accounting::LargeObjectBitmap* los_bitmap =
1032                heap_mark_bitmap_->GetLargeObjectBitmap(obj);
1033            CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1034            bool is_los = mark_bitmap == nullptr;
1035            if (!is_los && mark_bitmap->Test(obj)) {
1036              LOG(INFO) << "holder is marked in the mark bit map.";
1037            } else if (is_los && los_bitmap->Test(obj)) {
1038              LOG(INFO) << "holder is marked in the los bit map.";
1039            } else {
1040              // If ref is on the allocation stack, then it is considered
1041              // mark/alive (but not necessarily on the live stack.)
1042              if (IsOnAllocStack(obj)) {
1043                LOG(INFO) << "holder is on the alloc stack.";
1044              } else {
1045                LOG(INFO) << "holder is not marked or on the alloc stack.";
1046              }
1047            }
1048          }
1049        }
1050        LOG(INFO) << "offset=" << offset.SizeValue();
1051      }
1052      CHECK(false) << "Found from-space ref " << ref << " " << PrettyTypeOf(ref);
1053    } else {
1054      // In a non-moving spaces. Check that the ref is marked.
1055      if (immune_region_.ContainsObject(ref)) {
1056        accounting::ContinuousSpaceBitmap* cc_bitmap =
1057            cc_heap_bitmap_->GetContinuousSpaceBitmap(ref);
1058        CHECK(cc_bitmap != nullptr)
1059            << "An immune space ref must have a bitmap. " << ref;
1060        if (kUseBakerReadBarrier) {
1061          CHECK(cc_bitmap->Test(ref))
1062              << "Unmarked immune space ref. obj=" << obj << " rb_ptr="
1063              << obj->GetReadBarrierPointer() << " ref=" << ref;
1064        } else {
1065          CHECK(cc_bitmap->Test(ref))
1066              << "Unmarked immune space ref. obj=" << obj << " ref=" << ref;
1067        }
1068      } else {
1069        accounting::ContinuousSpaceBitmap* mark_bitmap =
1070            heap_mark_bitmap_->GetContinuousSpaceBitmap(ref);
1071        accounting::LargeObjectBitmap* los_bitmap =
1072            heap_mark_bitmap_->GetLargeObjectBitmap(ref);
1073        CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1074        bool is_los = mark_bitmap == nullptr;
1075        if ((!is_los && mark_bitmap->Test(ref)) ||
1076            (is_los && los_bitmap->Test(ref))) {
1077          // OK.
1078        } else {
1079          // If ref is on the allocation stack, then it may not be
1080          // marked live, but considered marked/alive (but not
1081          // necessarily on the live stack).
1082          CHECK(IsOnAllocStack(ref)) << "Unmarked ref that's not on the allocation stack. "
1083                                     << "obj=" << obj << " ref=" << ref;
1084        }
1085      }
1086    }
1087  }
1088}
1089
1090void ConcurrentCopying::ProcessRootCallback(mirror::Object** root, void* arg,
1091                                            const RootInfo& /*root_info*/) {
1092  reinterpret_cast<ConcurrentCopying*>(arg)->Process(root);
1093}
1094
1095// Used to scan ref fields of an object.
1096class ConcurrentCopyingRefFieldsVisitor {
1097 public:
1098  explicit ConcurrentCopyingRefFieldsVisitor(ConcurrentCopying* collector)
1099      : collector_(collector) {}
1100
1101  void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */)
1102      const ALWAYS_INLINE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
1103      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
1104    collector_->Process(obj, offset);
1105  }
1106
1107  void operator()(mirror::Class* klass, mirror::Reference* ref) const
1108      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
1109    CHECK(klass->IsTypeOfReferenceClass());
1110    collector_->DelayReferenceReferent(klass, ref);
1111  }
1112
1113 private:
1114  ConcurrentCopying* const collector_;
1115};
1116
1117// Scan ref fields of an object.
1118void ConcurrentCopying::Scan(mirror::Object* to_ref) {
1119  DCHECK(!region_space_->IsInFromSpace(to_ref));
1120  ConcurrentCopyingRefFieldsVisitor visitor(this);
1121  to_ref->VisitReferences<true>(visitor, visitor);
1122}
1123
1124// Process a field.
1125inline void ConcurrentCopying::Process(mirror::Object* obj, MemberOffset offset) {
1126  mirror::Object* ref = obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset);
1127  if (ref == nullptr || region_space_->IsInToSpace(ref)) {
1128    return;
1129  }
1130  mirror::Object* to_ref = Mark(ref);
1131  if (to_ref == ref) {
1132    return;
1133  }
1134  // This may fail if the mutator writes to the field at the same time. But it's ok.
1135  mirror::Object* expected_ref = ref;
1136  mirror::Object* new_ref = to_ref;
1137  do {
1138    if (expected_ref !=
1139        obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset)) {
1140      // It was updated by the mutator.
1141      break;
1142    }
1143  } while (!obj->CasFieldWeakSequentiallyConsistentObjectWithoutWriteBarrier<false, false, kVerifyNone>(
1144      offset, expected_ref, new_ref));
1145}
1146
1147// Process a root.
1148void ConcurrentCopying::Process(mirror::Object** root) {
1149  mirror::Object* ref = *root;
1150  if (ref == nullptr || region_space_->IsInToSpace(ref)) {
1151    return;
1152  }
1153  mirror::Object* to_ref = Mark(ref);
1154  if (to_ref == ref) {
1155    return;
1156  }
1157  Atomic<mirror::Object*>* addr = reinterpret_cast<Atomic<mirror::Object*>*>(root);
1158  mirror::Object* expected_ref = ref;
1159  mirror::Object* new_ref = to_ref;
1160  do {
1161    if (expected_ref != addr->LoadRelaxed()) {
1162      // It was updated by the mutator.
1163      break;
1164    }
1165  } while (!addr->CompareExchangeWeakSequentiallyConsistent(expected_ref, new_ref));
1166}
1167
1168// Fill the given memory block with a dummy object. Used to fill in a
1169// copy of objects that was lost in race.
1170void ConcurrentCopying::FillWithDummyObject(mirror::Object* dummy_obj, size_t byte_size) {
1171  CHECK(IsAligned<kObjectAlignment>(byte_size));
1172  memset(dummy_obj, 0, byte_size);
1173  mirror::Class* int_array_class = mirror::IntArray::GetArrayClass();
1174  CHECK(int_array_class != nullptr);
1175  AssertToSpaceInvariant(nullptr, MemberOffset(0), int_array_class);
1176  size_t component_size = int_array_class->GetComponentSize();
1177  CHECK_EQ(component_size, sizeof(int32_t));
1178  size_t data_offset = mirror::Array::DataOffset(component_size).SizeValue();
1179  if (data_offset > byte_size) {
1180    // An int array is too big. Use java.lang.Object.
1181    mirror::Class* java_lang_Object = WellKnownClasses::ToClass(WellKnownClasses::java_lang_Object);
1182    AssertToSpaceInvariant(nullptr, MemberOffset(0), java_lang_Object);
1183    CHECK_EQ(byte_size, java_lang_Object->GetObjectSize());
1184    dummy_obj->SetClass(java_lang_Object);
1185    CHECK_EQ(byte_size, dummy_obj->SizeOf());
1186  } else {
1187    // Use an int array.
1188    dummy_obj->SetClass(int_array_class);
1189    CHECK(dummy_obj->IsArrayInstance());
1190    int32_t length = (byte_size - data_offset) / component_size;
1191    dummy_obj->AsArray()->SetLength(length);
1192    CHECK_EQ(dummy_obj->AsArray()->GetLength(), length)
1193        << "byte_size=" << byte_size << " length=" << length
1194        << " component_size=" << component_size << " data_offset=" << data_offset;
1195    CHECK_EQ(byte_size, dummy_obj->SizeOf())
1196        << "byte_size=" << byte_size << " length=" << length
1197        << " component_size=" << component_size << " data_offset=" << data_offset;
1198  }
1199}
1200
1201// Reuse the memory blocks that were copy of objects that were lost in race.
1202mirror::Object* ConcurrentCopying::AllocateInSkippedBlock(size_t alloc_size) {
1203  // Try to reuse the blocks that were unused due to CAS failures.
1204  CHECK(IsAligned<space::RegionSpace::kAlignment>(alloc_size));
1205  Thread* self = Thread::Current();
1206  size_t min_object_size = RoundUp(sizeof(mirror::Object), space::RegionSpace::kAlignment);
1207  MutexLock mu(self, skipped_blocks_lock_);
1208  auto it = skipped_blocks_map_.lower_bound(alloc_size);
1209  if (it == skipped_blocks_map_.end()) {
1210    // Not found.
1211    return nullptr;
1212  }
1213  {
1214    size_t byte_size = it->first;
1215    CHECK_GE(byte_size, alloc_size);
1216    if (byte_size > alloc_size && byte_size - alloc_size < min_object_size) {
1217      // If remainder would be too small for a dummy object, retry with a larger request size.
1218      it = skipped_blocks_map_.lower_bound(alloc_size + min_object_size);
1219      if (it == skipped_blocks_map_.end()) {
1220        // Not found.
1221        return nullptr;
1222      }
1223      CHECK(IsAligned<space::RegionSpace::kAlignment>(it->first - alloc_size));
1224      CHECK_GE(it->first - alloc_size, min_object_size)
1225          << "byte_size=" << byte_size << " it->first=" << it->first << " alloc_size=" << alloc_size;
1226    }
1227  }
1228  // Found a block.
1229  CHECK(it != skipped_blocks_map_.end());
1230  size_t byte_size = it->first;
1231  uint8_t* addr = it->second;
1232  CHECK_GE(byte_size, alloc_size);
1233  CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr)));
1234  CHECK(IsAligned<space::RegionSpace::kAlignment>(byte_size));
1235  if (kVerboseMode) {
1236    LOG(INFO) << "Reusing skipped bytes : " << reinterpret_cast<void*>(addr) << ", " << byte_size;
1237  }
1238  skipped_blocks_map_.erase(it);
1239  memset(addr, 0, byte_size);
1240  if (byte_size > alloc_size) {
1241    // Return the remainder to the map.
1242    CHECK(IsAligned<space::RegionSpace::kAlignment>(byte_size - alloc_size));
1243    CHECK_GE(byte_size - alloc_size, min_object_size);
1244    FillWithDummyObject(reinterpret_cast<mirror::Object*>(addr + alloc_size),
1245                        byte_size - alloc_size);
1246    CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr + alloc_size)));
1247    skipped_blocks_map_.insert(std::make_pair(byte_size - alloc_size, addr + alloc_size));
1248  }
1249  return reinterpret_cast<mirror::Object*>(addr);
1250}
1251
1252mirror::Object* ConcurrentCopying::Copy(mirror::Object* from_ref) {
1253  DCHECK(region_space_->IsInFromSpace(from_ref));
1254  // No read barrier to avoid nested RB that might violate the to-space
1255  // invariant. Note that from_ref is a from space ref so the SizeOf()
1256  // call will access the from-space meta objects, but it's ok and necessary.
1257  size_t obj_size = from_ref->SizeOf<kDefaultVerifyFlags, kWithoutReadBarrier>();
1258  size_t region_space_alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment);
1259  size_t region_space_bytes_allocated = 0U;
1260  size_t non_moving_space_bytes_allocated = 0U;
1261  size_t bytes_allocated = 0U;
1262  mirror::Object* to_ref = region_space_->AllocNonvirtual<true>(
1263      region_space_alloc_size, &region_space_bytes_allocated, nullptr);
1264  bytes_allocated = region_space_bytes_allocated;
1265  if (to_ref != nullptr) {
1266    DCHECK_EQ(region_space_alloc_size, region_space_bytes_allocated);
1267  }
1268  bool fall_back_to_non_moving = false;
1269  if (UNLIKELY(to_ref == nullptr)) {
1270    // Failed to allocate in the region space. Try the skipped blocks.
1271    to_ref = AllocateInSkippedBlock(region_space_alloc_size);
1272    if (to_ref != nullptr) {
1273      // Succeeded to allocate in a skipped block.
1274      if (heap_->use_tlab_) {
1275        // This is necessary for the tlab case as it's not accounted in the space.
1276        region_space_->RecordAlloc(to_ref);
1277      }
1278      bytes_allocated = region_space_alloc_size;
1279    } else {
1280      // Fall back to the non-moving space.
1281      fall_back_to_non_moving = true;
1282      if (kVerboseMode) {
1283        LOG(INFO) << "Out of memory in the to-space. Fall back to non-moving. skipped_bytes="
1284                  << to_space_bytes_skipped_.LoadSequentiallyConsistent()
1285                  << " skipped_objects=" << to_space_objects_skipped_.LoadSequentiallyConsistent();
1286      }
1287      fall_back_to_non_moving = true;
1288      to_ref = heap_->non_moving_space_->Alloc(Thread::Current(), obj_size,
1289                                               &non_moving_space_bytes_allocated, nullptr);
1290      CHECK(to_ref != nullptr) << "Fall-back non-moving space allocation failed";
1291      bytes_allocated = non_moving_space_bytes_allocated;
1292      // Mark it in the mark bitmap.
1293      accounting::ContinuousSpaceBitmap* mark_bitmap =
1294          heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref);
1295      CHECK(mark_bitmap != nullptr);
1296      CHECK(!mark_bitmap->AtomicTestAndSet(to_ref));
1297    }
1298  }
1299  DCHECK(to_ref != nullptr);
1300
1301  // Attempt to install the forward pointer. This is in a loop as the
1302  // lock word atomic write can fail.
1303  while (true) {
1304    // Copy the object. TODO: copy only the lockword in the second iteration and on?
1305    memcpy(to_ref, from_ref, obj_size);
1306    // Set the gray ptr.
1307    if (kUseBakerReadBarrier) {
1308      to_ref->SetReadBarrierPointer(ReadBarrier::GrayPtr());
1309    }
1310
1311    LockWord old_lock_word = to_ref->GetLockWord(false);
1312
1313    if (old_lock_word.GetState() == LockWord::kForwardingAddress) {
1314      // Lost the race. Another thread (either GC or mutator) stored
1315      // the forwarding pointer first. Make the lost copy (to_ref)
1316      // look like a valid but dead (dummy) object and keep it for
1317      // future reuse.
1318      FillWithDummyObject(to_ref, bytes_allocated);
1319      if (!fall_back_to_non_moving) {
1320        DCHECK(region_space_->IsInToSpace(to_ref));
1321        if (bytes_allocated > space::RegionSpace::kRegionSize) {
1322          // Free the large alloc.
1323          region_space_->FreeLarge(to_ref, bytes_allocated);
1324        } else {
1325          // Record the lost copy for later reuse.
1326          heap_->num_bytes_allocated_.FetchAndAddSequentiallyConsistent(bytes_allocated);
1327          to_space_bytes_skipped_.FetchAndAddSequentiallyConsistent(bytes_allocated);
1328          to_space_objects_skipped_.FetchAndAddSequentiallyConsistent(1);
1329          MutexLock mu(Thread::Current(), skipped_blocks_lock_);
1330          skipped_blocks_map_.insert(std::make_pair(bytes_allocated,
1331                                                    reinterpret_cast<uint8_t*>(to_ref)));
1332        }
1333      } else {
1334        DCHECK(heap_->non_moving_space_->HasAddress(to_ref));
1335        DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated);
1336        // Free the non-moving-space chunk.
1337        accounting::ContinuousSpaceBitmap* mark_bitmap =
1338            heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref);
1339        CHECK(mark_bitmap != nullptr);
1340        CHECK(mark_bitmap->Clear(to_ref));
1341        heap_->non_moving_space_->Free(Thread::Current(), to_ref);
1342      }
1343
1344      // Get the winner's forward ptr.
1345      mirror::Object* lost_fwd_ptr = to_ref;
1346      to_ref = reinterpret_cast<mirror::Object*>(old_lock_word.ForwardingAddress());
1347      CHECK(to_ref != nullptr);
1348      CHECK_NE(to_ref, lost_fwd_ptr);
1349      CHECK(region_space_->IsInToSpace(to_ref) || heap_->non_moving_space_->HasAddress(to_ref));
1350      CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress);
1351      return to_ref;
1352    }
1353
1354    LockWord new_lock_word = LockWord::FromForwardingAddress(reinterpret_cast<size_t>(to_ref));
1355
1356    // Try to atomically write the fwd ptr.
1357    bool success = from_ref->CasLockWordWeakSequentiallyConsistent(old_lock_word, new_lock_word);
1358    if (LIKELY(success)) {
1359      // The CAS succeeded.
1360      objects_moved_.FetchAndAddSequentiallyConsistent(1);
1361      bytes_moved_.FetchAndAddSequentiallyConsistent(region_space_alloc_size);
1362      if (LIKELY(!fall_back_to_non_moving)) {
1363        DCHECK(region_space_->IsInToSpace(to_ref));
1364      } else {
1365        DCHECK(heap_->non_moving_space_->HasAddress(to_ref));
1366        DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated);
1367      }
1368      if (kUseBakerReadBarrier) {
1369        DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1370      }
1371      DCHECK(GetFwdPtr(from_ref) == to_ref);
1372      CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress);
1373      PushOntoMarkStack<true>(to_ref);
1374      return to_ref;
1375    } else {
1376      // The CAS failed. It may have lost the race or may have failed
1377      // due to monitor/hashcode ops. Either way, retry.
1378    }
1379  }
1380}
1381
1382mirror::Object* ConcurrentCopying::IsMarked(mirror::Object* from_ref) {
1383  DCHECK(from_ref != nullptr);
1384  space::RegionSpace::RegionType rtype = region_space_->GetRegionType(from_ref);
1385  if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) {
1386    // It's already marked.
1387    return from_ref;
1388  }
1389  mirror::Object* to_ref;
1390  if (rtype == space::RegionSpace::RegionType::kRegionTypeFromSpace) {
1391    to_ref = GetFwdPtr(from_ref);
1392    DCHECK(to_ref == nullptr || region_space_->IsInToSpace(to_ref) ||
1393           heap_->non_moving_space_->HasAddress(to_ref))
1394        << "from_ref=" << from_ref << " to_ref=" << to_ref;
1395  } else if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) {
1396    if (region_space_bitmap_->Test(from_ref)) {
1397      to_ref = from_ref;
1398    } else {
1399      to_ref = nullptr;
1400    }
1401  } else {
1402    // from_ref is in a non-moving space.
1403    if (immune_region_.ContainsObject(from_ref)) {
1404      accounting::ContinuousSpaceBitmap* cc_bitmap =
1405          cc_heap_bitmap_->GetContinuousSpaceBitmap(from_ref);
1406      DCHECK(cc_bitmap != nullptr)
1407          << "An immune space object must have a bitmap";
1408      if (kIsDebugBuild) {
1409        DCHECK(heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref)->Test(from_ref))
1410            << "Immune space object must be already marked";
1411      }
1412      if (cc_bitmap->Test(from_ref)) {
1413        // Already marked.
1414        to_ref = from_ref;
1415      } else {
1416        // Newly marked.
1417        to_ref = nullptr;
1418      }
1419    } else {
1420      // Non-immune non-moving space. Use the mark bitmap.
1421      accounting::ContinuousSpaceBitmap* mark_bitmap =
1422          heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref);
1423      accounting::LargeObjectBitmap* los_bitmap =
1424          heap_mark_bitmap_->GetLargeObjectBitmap(from_ref);
1425      CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1426      bool is_los = mark_bitmap == nullptr;
1427      if (!is_los && mark_bitmap->Test(from_ref)) {
1428        // Already marked.
1429        to_ref = from_ref;
1430      } else if (is_los && los_bitmap->Test(from_ref)) {
1431        // Already marked in LOS.
1432        to_ref = from_ref;
1433      } else {
1434        // Not marked.
1435        if (IsOnAllocStack(from_ref)) {
1436          // If on the allocation stack, it's considered marked.
1437          to_ref = from_ref;
1438        } else {
1439          // Not marked.
1440          to_ref = nullptr;
1441        }
1442      }
1443    }
1444  }
1445  return to_ref;
1446}
1447
1448bool ConcurrentCopying::IsOnAllocStack(mirror::Object* ref) {
1449  QuasiAtomic::ThreadFenceAcquire();
1450  accounting::ObjectStack* alloc_stack = GetAllocationStack();
1451  return alloc_stack->Contains(ref);
1452}
1453
1454mirror::Object* ConcurrentCopying::Mark(mirror::Object* from_ref) {
1455  if (from_ref == nullptr) {
1456    return nullptr;
1457  }
1458  DCHECK(from_ref != nullptr);
1459  DCHECK(heap_->collector_type_ == kCollectorTypeCC);
1460  space::RegionSpace::RegionType rtype = region_space_->GetRegionType(from_ref);
1461  if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) {
1462    // It's already marked.
1463    return from_ref;
1464  }
1465  mirror::Object* to_ref;
1466  if (rtype == space::RegionSpace::RegionType::kRegionTypeFromSpace) {
1467    to_ref = GetFwdPtr(from_ref);
1468    if (kUseBakerReadBarrier) {
1469      DCHECK(to_ref != ReadBarrier::GrayPtr()) << "from_ref=" << from_ref << " to_ref=" << to_ref;
1470    }
1471    if (to_ref == nullptr) {
1472      // It isn't marked yet. Mark it by copying it to the to-space.
1473      to_ref = Copy(from_ref);
1474    }
1475    DCHECK(region_space_->IsInToSpace(to_ref) || heap_->non_moving_space_->HasAddress(to_ref))
1476        << "from_ref=" << from_ref << " to_ref=" << to_ref;
1477  } else if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) {
1478    // This may or may not succeed, which is ok.
1479    if (kUseBakerReadBarrier) {
1480      from_ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
1481    }
1482    if (region_space_bitmap_->AtomicTestAndSet(from_ref)) {
1483      // Already marked.
1484      to_ref = from_ref;
1485    } else {
1486      // Newly marked.
1487      to_ref = from_ref;
1488      if (kUseBakerReadBarrier) {
1489        DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1490      }
1491      PushOntoMarkStack<true>(to_ref);
1492    }
1493  } else {
1494    // from_ref is in a non-moving space.
1495    DCHECK(!region_space_->HasAddress(from_ref)) << from_ref;
1496    if (immune_region_.ContainsObject(from_ref)) {
1497      accounting::ContinuousSpaceBitmap* cc_bitmap =
1498          cc_heap_bitmap_->GetContinuousSpaceBitmap(from_ref);
1499      DCHECK(cc_bitmap != nullptr)
1500          << "An immune space object must have a bitmap";
1501      if (kIsDebugBuild) {
1502        DCHECK(heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref)->Test(from_ref))
1503            << "Immune space object must be already marked";
1504      }
1505      // This may or may not succeed, which is ok.
1506      if (kUseBakerReadBarrier) {
1507        from_ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
1508      }
1509      if (cc_bitmap->AtomicTestAndSet(from_ref)) {
1510        // Already marked.
1511        to_ref = from_ref;
1512      } else {
1513        // Newly marked.
1514        to_ref = from_ref;
1515        if (kUseBakerReadBarrier) {
1516          DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1517        }
1518        PushOntoMarkStack<true>(to_ref);
1519      }
1520    } else {
1521      // Use the mark bitmap.
1522      accounting::ContinuousSpaceBitmap* mark_bitmap =
1523          heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref);
1524      accounting::LargeObjectBitmap* los_bitmap =
1525          heap_mark_bitmap_->GetLargeObjectBitmap(from_ref);
1526      CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1527      bool is_los = mark_bitmap == nullptr;
1528      if (!is_los && mark_bitmap->Test(from_ref)) {
1529        // Already marked.
1530        to_ref = from_ref;
1531        if (kUseBakerReadBarrier) {
1532          DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr() ||
1533                 to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
1534        }
1535      } else if (is_los && los_bitmap->Test(from_ref)) {
1536        // Already marked in LOS.
1537        to_ref = from_ref;
1538        if (kUseBakerReadBarrier) {
1539          DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr() ||
1540                 to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
1541        }
1542      } else {
1543        // Not marked.
1544        if (IsOnAllocStack(from_ref)) {
1545          // If it's on the allocation stack, it's considered marked. Keep it white.
1546          to_ref = from_ref;
1547          // Objects on the allocation stack need not be marked.
1548          if (!is_los) {
1549            DCHECK(!mark_bitmap->Test(to_ref));
1550          } else {
1551            DCHECK(!los_bitmap->Test(to_ref));
1552          }
1553          if (kUseBakerReadBarrier) {
1554            DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr());
1555          }
1556        } else {
1557          // Not marked or on the allocation stack. Try to mark it.
1558          // This may or may not succeed, which is ok.
1559          if (kUseBakerReadBarrier) {
1560            from_ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
1561          }
1562          if (!is_los && mark_bitmap->AtomicTestAndSet(from_ref)) {
1563            // Already marked.
1564            to_ref = from_ref;
1565          } else if (is_los && los_bitmap->AtomicTestAndSet(from_ref)) {
1566            // Already marked in LOS.
1567            to_ref = from_ref;
1568          } else {
1569            // Newly marked.
1570            to_ref = from_ref;
1571            if (kUseBakerReadBarrier) {
1572              DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1573            }
1574            PushOntoMarkStack<true>(to_ref);
1575          }
1576        }
1577      }
1578    }
1579  }
1580  return to_ref;
1581}
1582
1583void ConcurrentCopying::FinishPhase() {
1584  region_space_ = nullptr;
1585  CHECK(mark_queue_.IsEmpty());
1586  mark_queue_.Clear();
1587  {
1588    MutexLock mu(Thread::Current(), skipped_blocks_lock_);
1589    skipped_blocks_map_.clear();
1590  }
1591  WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
1592  heap_->ClearMarkedObjects();
1593}
1594
1595mirror::Object* ConcurrentCopying::IsMarkedCallback(mirror::Object* from_ref, void* arg) {
1596  return reinterpret_cast<ConcurrentCopying*>(arg)->IsMarked(from_ref);
1597}
1598
1599bool ConcurrentCopying::IsHeapReferenceMarkedCallback(
1600    mirror::HeapReference<mirror::Object>* field, void* arg) {
1601  mirror::Object* from_ref = field->AsMirrorPtr();
1602  mirror::Object* to_ref = reinterpret_cast<ConcurrentCopying*>(arg)->IsMarked(from_ref);
1603  if (to_ref == nullptr) {
1604    return false;
1605  }
1606  if (from_ref != to_ref) {
1607    QuasiAtomic::ThreadFenceRelease();
1608    field->Assign(to_ref);
1609    QuasiAtomic::ThreadFenceSequentiallyConsistent();
1610  }
1611  return true;
1612}
1613
1614mirror::Object* ConcurrentCopying::MarkCallback(mirror::Object* from_ref, void* arg) {
1615  return reinterpret_cast<ConcurrentCopying*>(arg)->Mark(from_ref);
1616}
1617
1618void ConcurrentCopying::ProcessMarkStackCallback(void* arg) {
1619  reinterpret_cast<ConcurrentCopying*>(arg)->ProcessMarkStack();
1620}
1621
1622void ConcurrentCopying::DelayReferenceReferent(mirror::Class* klass, mirror::Reference* reference) {
1623  heap_->GetReferenceProcessor()->DelayReferenceReferent(
1624      klass, reference, &IsHeapReferenceMarkedCallback, this);
1625}
1626
1627void ConcurrentCopying::ProcessReferences(Thread* self, bool concurrent) {
1628  TimingLogger::ScopedTiming split("ProcessReferences", GetTimings());
1629  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
1630  GetHeap()->GetReferenceProcessor()->ProcessReferences(
1631      concurrent, GetTimings(), GetCurrentIteration()->GetClearSoftReferences(),
1632      &IsHeapReferenceMarkedCallback, &MarkCallback, &ProcessMarkStackCallback, this);
1633}
1634
1635void ConcurrentCopying::RevokeAllThreadLocalBuffers() {
1636  TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings());
1637  region_space_->RevokeAllThreadLocalBuffers();
1638}
1639
1640}  // namespace collector
1641}  // namespace gc
1642}  // namespace art
1643