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// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/gc_marker.h"
#include "vm/allocation.h"
#include "vm/dart_api_state.h"
#include "vm/isolate.h"
#include "vm/log.h"
#include "vm/object_id_ring.h"
#include "vm/pages.h"
#include "vm/raw_object.h"
#include "vm/stack_frame.h"
#include "vm/store_buffer.h"
#include "vm/thread_barrier.h"
#include "vm/thread_pool.h"
#include "vm/thread_registry.h"
#include "vm/timeline.h"
#include "vm/visitor.h"
namespace dart {
class SkippedCodeFunctions : public ZoneAllocated {
public:
SkippedCodeFunctions() {}
void Add(RawFunction* func) { skipped_code_functions_.Add(func); }
void DetachCode() {
#if defined(DART_PRECOMPILED_RUNTIME)
UNREACHABLE();
#else
intptr_t unoptimized_code_count = 0;
intptr_t current_code_count = 0;
for (int i = 0; i < skipped_code_functions_.length(); i++) {
RawFunction* func = skipped_code_functions_[i];
RawCode* code = func->ptr()->code_;
if (!code->IsMarked()) {
// If the code wasn't strongly visited through other references
// after skipping the function's code pointer, then we disconnect the
// code from the function.
func->StorePointer(&(func->ptr()->code_),
StubCode::LazyCompile_entry()->code());
uword entry_point = StubCode::LazyCompile_entry()->EntryPoint();
func->ptr()->entry_point_ = entry_point;
if (FLAG_log_code_drop) {
// NOTE: This code runs while GC is in progress and runs within
// a NoHandleScope block. Hence it is not okay to use a regular Zone
// or Scope handle. We use a direct stack handle so the raw pointer in
// this handle is not traversed. The use of a handle is mainly to
// be able to reuse the handle based code and avoid having to add
// helper functions to the raw object interface.
String name;
name = func->ptr()->name_;
THR_Print("Detaching code: %s\n", name.ToCString());
current_code_count++;
}
}
code = func->ptr()->unoptimized_code_;
if (!code->IsMarked()) {
// If the code wasn't strongly visited through other references
// after skipping the function's code pointer, then we disconnect the
// code from the function.
func->StorePointer(&(func->ptr()->unoptimized_code_), Code::null());
if (FLAG_log_code_drop) {
unoptimized_code_count++;
}
}
}
if (FLAG_log_code_drop) {
THR_Print(" total detached current: %" Pd "\n", current_code_count);
THR_Print(" total detached unoptimized: %" Pd "\n",
unoptimized_code_count);
}
// Clean up.
skipped_code_functions_.Clear();
#endif // !DART_PRECOMPILED_RUNTIME
}
private:
GrowableArray<RawFunction*> skipped_code_functions_;
DISALLOW_COPY_AND_ASSIGN(SkippedCodeFunctions);
};
class MarkerWorkList : public ValueObject {
public:
explicit MarkerWorkList(MarkingStack* marking_stack)
: marking_stack_(marking_stack) {
work_ = marking_stack_->PopEmptyBlock();
}
~MarkerWorkList() {
ASSERT(work_ == NULL);
ASSERT(marking_stack_ == NULL);
}
// Returns NULL if no more work was found.
RawObject* Pop() {
ASSERT(work_ != NULL);
if (work_->IsEmpty()) {
// TODO(koda): Track over/underflow events and use in heuristics to
// distribute work and prevent degenerate flip-flopping.
MarkingStack::Block* new_work = marking_stack_->PopNonEmptyBlock();
if (new_work == NULL) {
return NULL;
}
marking_stack_->PushBlock(work_);
work_ = new_work;
}
return work_->Pop();
}
void Push(RawObject* raw_obj) {
if (work_->IsFull()) {
// TODO(koda): Track over/underflow events and use in heuristics to
// distribute work and prevent degenerate flip-flopping.
marking_stack_->PushBlock(work_);
work_ = marking_stack_->PopEmptyBlock();
}
work_->Push(raw_obj);
}
void Finalize() {
ASSERT(work_->IsEmpty());
marking_stack_->PushBlock(work_);
work_ = NULL;
// Fail fast on attempts to mark after finalizing.
marking_stack_ = NULL;
}
private:
MarkingStack::Block* work_;
MarkingStack* marking_stack_;
};
template <bool sync>
class MarkingVisitorBase : public ObjectPointerVisitor {
public:
MarkingVisitorBase(Isolate* isolate,
PageSpace* page_space,
MarkingStack* marking_stack,
SkippedCodeFunctions* skipped_code_functions)
: ObjectPointerVisitor(isolate),
thread_(Thread::Current()),
#ifndef PRODUCT
class_stats_count_(isolate->class_table()->NumCids()),
class_stats_size_(isolate->class_table()->NumCids()),
#endif // !PRODUCT
page_space_(page_space),
work_list_(marking_stack),
delayed_weak_properties_(NULL),
visiting_old_object_(NULL),
skipped_code_functions_(skipped_code_functions),
marked_bytes_(0) {
ASSERT(thread_->isolate() == isolate);
#ifndef PRODUCT
class_stats_count_.SetLength(isolate->class_table()->NumCids());
class_stats_size_.SetLength(isolate->class_table()->NumCids());
for (intptr_t i = 0; i < class_stats_count_.length(); ++i) {
class_stats_count_[i] = 0;
class_stats_size_[i] = 0;
}
#endif // !PRODUCT
}
uintptr_t marked_bytes() const { return marked_bytes_; }
#ifndef PRODUCT
intptr_t live_count(intptr_t class_id) {
return class_stats_count_[class_id];
}
intptr_t live_size(intptr_t class_id) { return class_stats_size_[class_id]; }
#endif // !PRODUCT
bool ProcessPendingWeakProperties() {
bool marked = false;
RawWeakProperty* cur_weak = delayed_weak_properties_;
delayed_weak_properties_ = NULL;
while (cur_weak != NULL) {
uword next_weak = cur_weak->ptr()->next_;
RawObject* raw_key = cur_weak->ptr()->key_;
// Reset the next pointer in the weak property.
cur_weak->ptr()->next_ = 0;
if (raw_key->IsMarked()) {
RawObject* raw_val = cur_weak->ptr()->value_;
marked = marked || (raw_val->IsHeapObject() && !raw_val->IsMarked());
// The key is marked so we make sure to properly visit all pointers
// originating from this weak property.
VisitingOldObject(cur_weak);
cur_weak->VisitPointersNonvirtual(this);
} else {
// Requeue this weak property to be handled later.
EnqueueWeakProperty(cur_weak);
}
// Advance to next weak property in the queue.
cur_weak = reinterpret_cast<RawWeakProperty*>(next_weak);
}
VisitingOldObject(NULL);
return marked;
}
void DrainMarkingStack() {
RawObject* raw_obj = work_list_.Pop();
if ((raw_obj == NULL) && ProcessPendingWeakProperties()) {
raw_obj = work_list_.Pop();
}
if (raw_obj == NULL) {
ASSERT(visiting_old_object_ == NULL);
return;
}
do {
do {
// First drain the marking stacks.
VisitingOldObject(raw_obj);
const intptr_t class_id = raw_obj->GetClassId();
if (class_id != kWeakPropertyCid) {
marked_bytes_ += raw_obj->VisitPointersNonvirtual(this);
} else {
RawWeakProperty* raw_weak =
reinterpret_cast<RawWeakProperty*>(raw_obj);
marked_bytes_ += ProcessWeakProperty(raw_weak);
}
raw_obj = work_list_.Pop();
} while (raw_obj != NULL);
// Marking stack is empty.
ProcessPendingWeakProperties();
// Check whether any further work was pushed either by other markers or
// by the handling of weak properties.
raw_obj = work_list_.Pop();
} while (raw_obj != NULL);
VisitingOldObject(NULL);
}
void VisitPointers(RawObject** first, RawObject** last) {
for (RawObject** current = first; current <= last; current++) {
MarkObject(*current, current);
}
}
bool visit_function_code() const { return skipped_code_functions_ == NULL; }
virtual void add_skipped_code_function(RawFunction* func) {
ASSERT(!visit_function_code());
skipped_code_functions_->Add(func);
}
void EnqueueWeakProperty(RawWeakProperty* raw_weak) {
ASSERT(raw_weak->IsHeapObject());
ASSERT(raw_weak->IsOldObject());
ASSERT(raw_weak->IsWeakProperty());
ASSERT(raw_weak->IsMarked());
ASSERT(raw_weak->ptr()->next_ == 0);
raw_weak->ptr()->next_ = reinterpret_cast<uword>(delayed_weak_properties_);
delayed_weak_properties_ = raw_weak;
}
intptr_t ProcessWeakProperty(RawWeakProperty* raw_weak) {
// The fate of the weak property is determined by its key.
RawObject* raw_key = raw_weak->ptr()->key_;
if (raw_key->IsHeapObject() && raw_key->IsOldObject() &&
!raw_key->IsMarked()) {
// Key was white. Enqueue the weak property.
EnqueueWeakProperty(raw_weak);
return raw_weak->Size();
}
// Key is gray or black. Make the weak property black.
return raw_weak->VisitPointersNonvirtual(this);
}
// Called when all marking is complete.
void Finalize() {
work_list_.Finalize();
// Detach code from functions.
if (skipped_code_functions_ != NULL) {
skipped_code_functions_->DetachCode();
}
// Clear pending weak properties.
RawWeakProperty* cur_weak = delayed_weak_properties_;
delayed_weak_properties_ = NULL;
intptr_t weak_properties_cleared = 0;
while (cur_weak != NULL) {
uword next_weak = cur_weak->ptr()->next_;
cur_weak->ptr()->next_ = 0;
RELEASE_ASSERT(!cur_weak->ptr()->key_->IsMarked());
WeakProperty::Clear(cur_weak);
weak_properties_cleared++;
// Advance to next weak property in the queue.
cur_weak = reinterpret_cast<RawWeakProperty*>(next_weak);
}
}
void VisitingOldObject(RawObject* obj) {
ASSERT((obj == NULL) || obj->IsOldObject());
visiting_old_object_ = obj;
}
private:
void PushMarked(RawObject* raw_obj) {
ASSERT(raw_obj->IsHeapObject());
ASSERT((FLAG_verify_gc_contains)
? page_space_->Contains(RawObject::ToAddr(raw_obj))
: true);
// Push the marked object on the marking stack.
ASSERT(raw_obj->IsMarked());
// We acquired the mark bit => no other task is modifying the header.
// TODO(koda): For concurrent mutator, this needs synchronization. Consider
// clearing these bits already in the CAS for the mark bit.
raw_obj->ClearRememberedBitUnsynchronized();
work_list_.Push(raw_obj);
}
static bool TryAcquireMarkBit(RawObject* raw_obj) {
if (!sync) {
if (raw_obj->IsMarked()) return false;
raw_obj->SetMarkBitUnsynchronized();
return true;
}
return raw_obj->TryAcquireMarkBit();
}
void MarkObject(RawObject* raw_obj, RawObject** p) {
// Fast exit if the raw object is a Smi.
if (!raw_obj->IsHeapObject()) {
return;
}
// Fast exit if the raw object is marked.
if (raw_obj->IsMarked()) {
return;
}
// TODO(koda): Investigate performance impact of alternative branching:
// if (smi or new) <-- can be done as single compare + conditional jump
// if (smi) return;
// else ...
// if (marked) return;
// ...
if (raw_obj->IsNewObject()) {
ProcessNewSpaceObject(raw_obj, p);
return;
}
if (!TryAcquireMarkBit(raw_obj)) {
// Already marked.
return;
}
#ifndef PRODUCT
if (RawObject::IsVariableSizeClassId(raw_obj->GetClassId())) {
UpdateLiveOld(raw_obj->GetClassId(), raw_obj->Size());
} else {
UpdateLiveOld(raw_obj->GetClassId(), 0);
}
#endif // !PRODUCT
PushMarked(raw_obj);
}
static bool TryAcquireRememberedBit(RawObject* raw_obj) {
if (!sync) {
if (raw_obj->IsRemembered()) return false;
raw_obj->SetRememberedBitUnsynchronized();
return true;
}
return raw_obj->TryAcquireRememberedBit();
}
void ProcessNewSpaceObject(RawObject* raw_obj, RawObject** p) {
// TODO(iposva): Add consistency check.
if ((visiting_old_object_ != NULL) &&
TryAcquireRememberedBit(visiting_old_object_)) {
// NOTE: We pass in the pointer to the address we are visiting
// allows us to get a distance from the object start. At some
// point we might want to store exact addresses in store buffers
// for locations far enough from the header, so that we do not
// need to walk big objects only to find the single new
// reference in the last word during scavenge. This doesn't seem
// to be a problem though currently.
ASSERT(p != NULL);
thread_->StoreBufferAddObjectGC(visiting_old_object_);
}
}
#ifndef PRODUCT
void UpdateLiveOld(intptr_t class_id, intptr_t size) {
// TODO(koda): Support growing the array once mutator runs concurrently.
ASSERT(class_id < class_stats_count_.length());
class_stats_count_[class_id] += 1;
class_stats_size_[class_id] += size;
}
#endif // !PRODUCT
Thread* thread_;
#ifndef PRODUCT
GrowableArray<intptr_t> class_stats_count_;
GrowableArray<intptr_t> class_stats_size_;
#endif // !PRODUCT
PageSpace* page_space_;
MarkerWorkList work_list_;
RawWeakProperty* delayed_weak_properties_;
RawObject* visiting_old_object_;
SkippedCodeFunctions* skipped_code_functions_;
uintptr_t marked_bytes_;
DISALLOW_IMPLICIT_CONSTRUCTORS(MarkingVisitorBase);
};
typedef MarkingVisitorBase<false> UnsyncMarkingVisitor;
typedef MarkingVisitorBase<true> SyncMarkingVisitor;
static bool IsUnreachable(const RawObject* raw_obj) {
if (!raw_obj->IsHeapObject()) {
return false;
}
if (raw_obj == Object::null()) {
return true;
}
if (!raw_obj->IsOldObject()) {
return false;
}
return !raw_obj->IsMarked();
}
class MarkingWeakVisitor : public HandleVisitor {
public:
explicit MarkingWeakVisitor(Thread* thread)
: HandleVisitor(thread), class_table_(thread->isolate()->class_table()) {}
void VisitHandle(uword addr) {
FinalizablePersistentHandle* handle =
reinterpret_cast<FinalizablePersistentHandle*>(addr);
RawObject* raw_obj = handle->raw();
if (IsUnreachable(raw_obj)) {
handle->UpdateUnreachable(thread()->isolate());
} else {
#ifndef PRODUCT
intptr_t cid = raw_obj->GetClassIdMayBeSmi();
intptr_t size = handle->external_size();
if (raw_obj->IsSmiOrOldObject()) {
class_table_->UpdateLiveOldExternal(cid, size);
} else {
class_table_->UpdateLiveNewExternal(cid, size);
}
#endif // !PRODUCT
}
}
private:
ClassTable* class_table_;
DISALLOW_COPY_AND_ASSIGN(MarkingWeakVisitor);
};
void GCMarker::Prologue(Isolate* isolate) {
isolate->PrepareForGC();
// The store buffers will be rebuilt as part of marking, reset them now.
isolate->store_buffer()->Reset();
}
void GCMarker::Epilogue(Isolate* isolate) {}
void GCMarker::IterateRoots(Isolate* isolate,
ObjectPointerVisitor* visitor,
intptr_t slice_index,
intptr_t num_slices) {
ASSERT(0 <= slice_index && slice_index < num_slices);
if ((slice_index == 0) || (num_slices <= 1)) {
isolate->VisitObjectPointers(visitor,
ValidationPolicy::kDontValidateFrames);
}
if ((slice_index == 1) || (num_slices <= 1)) {
heap_->new_space()->VisitObjectPointers(visitor);
}
// For now, we just distinguish two parts of the root set, so any remaining
// slices are empty.
}
void GCMarker::IterateWeakRoots(Isolate* isolate, HandleVisitor* visitor) {
ApiState* state = isolate->api_state();
ASSERT(state != NULL);
isolate->VisitWeakPersistentHandles(visitor);
}
void GCMarker::ProcessWeakTables(PageSpace* page_space) {
for (int sel = 0; sel < Heap::kNumWeakSelectors; sel++) {
WeakTable* table =
heap_->GetWeakTable(Heap::kOld, static_cast<Heap::WeakSelector>(sel));
intptr_t size = table->size();
for (intptr_t i = 0; i < size; i++) {
if (table->IsValidEntryAt(i)) {
RawObject* raw_obj = table->ObjectAt(i);
ASSERT(raw_obj->IsHeapObject());
if (!raw_obj->IsMarked()) {
table->InvalidateAt(i);
}
}
}
}
}
class ObjectIdRingClearPointerVisitor : public ObjectPointerVisitor {
public:
explicit ObjectIdRingClearPointerVisitor(Isolate* isolate)
: ObjectPointerVisitor(isolate) {}
void VisitPointers(RawObject** first, RawObject** last) {
for (RawObject** current = first; current <= last; current++) {
RawObject* raw_obj = *current;
ASSERT(raw_obj->IsHeapObject());
if (raw_obj->IsOldObject() && !raw_obj->IsMarked()) {
// Object has become garbage. Replace it will null.
*current = Object::null();
}
}
}
};
void GCMarker::ProcessObjectIdTable(Isolate* isolate) {
#ifndef PRODUCT
if (!FLAG_support_service) {
return;
}
ObjectIdRingClearPointerVisitor visitor(isolate);
ObjectIdRing* ring = isolate->object_id_ring();
ASSERT(ring != NULL);
ring->VisitPointers(&visitor);
#endif // !PRODUCT
}
class MarkTask : public ThreadPool::Task {
public:
MarkTask(GCMarker* marker,
Isolate* isolate,
Heap* heap,
PageSpace* page_space,
MarkingStack* marking_stack,
ThreadBarrier* barrier,
bool collect_code,
intptr_t task_index,
intptr_t num_tasks,
uintptr_t* num_busy)
: marker_(marker),
isolate_(isolate),
heap_(heap),
page_space_(page_space),
marking_stack_(marking_stack),
barrier_(barrier),
collect_code_(collect_code),
task_index_(task_index),
num_tasks_(num_tasks),
num_busy_(num_busy) {}
virtual void Run() {
bool result =
Thread::EnterIsolateAsHelper(isolate_, Thread::kMarkerTask, true);
ASSERT(result);
{
Thread* thread = Thread::Current();
TIMELINE_FUNCTION_GC_DURATION(thread, "MarkTask");
StackZone stack_zone(thread);
Zone* zone = stack_zone.GetZone();
SkippedCodeFunctions* skipped_code_functions =
collect_code_ ? new (zone) SkippedCodeFunctions() : NULL;
SyncMarkingVisitor visitor(isolate_, page_space_, marking_stack_,
skipped_code_functions);
// Phase 1: Iterate over roots and drain marking stack in tasks.
marker_->IterateRoots(isolate_, &visitor, task_index_, num_tasks_);
bool more_to_mark = false;
do {
do {
visitor.DrainMarkingStack();
// I can't find more work right now. If no other task is busy,
// then there will never be more work (NB: 1 is *before* decrement).
if (AtomicOperations::FetchAndDecrement(num_busy_) == 1) break;
// Wait for some work to appear.
// TODO(iposva): Replace busy-waiting with a solution using Monitor,
// and redraw the boundaries between stack/visitor/task as needed.
while (marking_stack_->IsEmpty() &&
AtomicOperations::LoadRelaxed(num_busy_) > 0) {
}
// If no tasks are busy, there will never be more work.
if (AtomicOperations::LoadRelaxed(num_busy_) == 0) break;
// I saw some work; get busy and compete for it.
AtomicOperations::FetchAndIncrement(num_busy_);
} while (true);
// Wait for all markers to stop.
barrier_->Sync();
#if defined(DEBUG)
ASSERT(AtomicOperations::LoadRelaxed(num_busy_) == 0);
// Caveat: must not allow any marker to continue past the barrier
// before we checked num_busy, otherwise one of them might rush
// ahead and increment it.
barrier_->Sync();
#endif
// Check if we have any pending properties with marked keys.
// Those might have been marked by another marker.
more_to_mark = visitor.ProcessPendingWeakProperties();
if (more_to_mark) {
// We have more work to do. Notify others.
AtomicOperations::FetchAndIncrement(num_busy_);
}
// Wait for all other markers to finish processing their pending
// weak properties and decide if they need to continue marking.
// Caveat: we need two barriers here to make this decision in lock step
// between all markers and the main thread.
barrier_->Sync();
if (!more_to_mark && (AtomicOperations::LoadRelaxed(num_busy_) > 0)) {
// All markers continue to mark as long as any single marker has
// some work to do.
AtomicOperations::FetchAndIncrement(num_busy_);
more_to_mark = true;
}
barrier_->Sync();
} while (more_to_mark);
// Phase 2: Weak processing and follow-up marking on main thread.
barrier_->Sync();
// Phase 3: Finalize results from all markers (detach code, etc.).
if (FLAG_log_marker_tasks) {
THR_Print("Task %" Pd " marked %" Pd " bytes.\n", task_index_,
visitor.marked_bytes());
}
marker_->FinalizeResultsFrom(&visitor);
}
Thread::ExitIsolateAsHelper(true);
// This task is done. Notify the original thread.
barrier_->Exit();
}
private:
GCMarker* marker_;
Isolate* isolate_;
Heap* heap_;
PageSpace* page_space_;
MarkingStack* marking_stack_;
ThreadBarrier* barrier_;
bool collect_code_;
const intptr_t task_index_;
const intptr_t num_tasks_;
uintptr_t* num_busy_;
DISALLOW_COPY_AND_ASSIGN(MarkTask);
};
template <class MarkingVisitorType>
void GCMarker::FinalizeResultsFrom(MarkingVisitorType* visitor) {
{
MutexLocker ml(&stats_mutex_);
marked_bytes_ += visitor->marked_bytes();
#ifndef PRODUCT
// Class heap stats are not themselves thread-safe yet, so we update the
// stats while holding stats_mutex_.
ClassTable* table = heap_->isolate()->class_table();
for (intptr_t i = 0; i < table->NumCids(); ++i) {
const intptr_t count = visitor->live_count(i);
if (count > 0) {
const intptr_t size = visitor->live_size(i);
table->UpdateLiveOld(i, size, count);
}
}
#endif // !PRODUCT
}
visitor->Finalize();
}
void GCMarker::MarkObjects(Isolate* isolate,
PageSpace* page_space,
bool collect_code) {
Prologue(isolate);
// The API prologue/epilogue may create/destroy zones, so we must not
// depend on zone allocations surviving beyond the epilogue callback.
{
Thread* thread = Thread::Current();
StackZone stack_zone(thread);
Zone* zone = stack_zone.GetZone();
MarkingStack marking_stack;
marked_bytes_ = 0;
const int num_tasks = FLAG_marker_tasks;
if (num_tasks == 0) {
// Mark everything on main thread.
SkippedCodeFunctions* skipped_code_functions =
collect_code ? new (zone) SkippedCodeFunctions() : NULL;
UnsyncMarkingVisitor mark(isolate, page_space, &marking_stack,
skipped_code_functions);
IterateRoots(isolate, &mark, 0, 1);
mark.DrainMarkingStack();
{
TIMELINE_FUNCTION_GC_DURATION(thread, "WeakHandleProcessing");
MarkingWeakVisitor mark_weak(thread);
IterateWeakRoots(isolate, &mark_weak);
}
// All marking done; detach code, etc.
FinalizeResultsFrom(&mark);
} else {
ThreadBarrier barrier(num_tasks + 1, heap_->barrier(),
heap_->barrier_done());
// Used to coordinate draining among tasks; all start out as 'busy'.
uintptr_t num_busy = num_tasks;
// Phase 1: Iterate over roots and drain marking stack in tasks.
for (intptr_t i = 0; i < num_tasks; ++i) {
MarkTask* mark_task =
new MarkTask(this, isolate, heap_, page_space, &marking_stack,
&barrier, collect_code, i, num_tasks, &num_busy);
ThreadPool* pool = Dart::thread_pool();
pool->Run(mark_task);
}
bool more_to_mark = false;
do {
// Wait for all markers to stop.
barrier.Sync();
#if defined(DEBUG)
ASSERT(AtomicOperations::LoadRelaxed(&num_busy) == 0);
// Caveat: must not allow any marker to continue past the barrier
// before we checked num_busy, otherwise one of them might rush
// ahead and increment it.
barrier.Sync();
#endif
// Wait for all markers to go through weak properties and verify
// that there are no more objects to mark.
// Note: we need to have two barriers here because we want all markers
// and main thread to make decisions in lock step.
barrier.Sync();
more_to_mark = AtomicOperations::LoadRelaxed(&num_busy) > 0;
barrier.Sync();
} while (more_to_mark);
// Phase 2: Weak processing on main thread.
{
TIMELINE_FUNCTION_GC_DURATION(thread, "WeakHandleProcessing");
MarkingWeakVisitor mark_weak(thread);
IterateWeakRoots(isolate, &mark_weak);
}
barrier.Sync();
// Phase 3: Finalize results from all markers (detach code, etc.).
barrier.Exit();
}
ProcessWeakTables(page_space);
ProcessObjectIdTable(isolate);
}
Epilogue(isolate);
}
} // namespace dart