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v8/src/global-handles.cc
mlippautz 58a753053c [api] Remove marking persistents as partially dependent 
Also remove the flag scavenge_reclaim_unmodified_objects which has been
defaulted to true for quite some time now.

BUG=chromium:651354

Review-Url: https://codereview.chromium.org/2486173002
Cr-Commit-Position: refs/heads/master@{#40878}
2016-11-10 09:29:48 +00:00

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// Copyright 2009 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/global-handles.h"
#include "src/api.h"
#include "src/v8.h"
#include "src/vm-state-inl.h"
namespace v8 {
namespace internal {
ObjectGroup::~ObjectGroup() {
if (info != NULL) info->Dispose();
delete[] objects;
}
ImplicitRefGroup::~ImplicitRefGroup() {
delete[] children;
}
class GlobalHandles::Node {
public:
// State transition diagram:
// FREE -> NORMAL <-> WEAK -> PENDING -> NEAR_DEATH -> { NORMAL, WEAK, FREE }
enum State {
FREE = 0,
NORMAL, // Normal global handle.
WEAK, // Flagged as weak but not yet finalized.
PENDING, // Has been recognized as only reachable by weak handles.
NEAR_DEATH, // Callback has informed the handle is near death.
NUMBER_OF_NODE_STATES
};
// Maps handle location (slot) to the containing node.
static Node* FromLocation(Object** location) {
DCHECK(offsetof(Node, object_) == 0);
return reinterpret_cast<Node*>(location);
}
Node() {
DCHECK(offsetof(Node, class_id_) == Internals::kNodeClassIdOffset);
DCHECK(offsetof(Node, flags_) == Internals::kNodeFlagsOffset);
STATIC_ASSERT(static_cast<int>(NodeState::kMask) ==
Internals::kNodeStateMask);
STATIC_ASSERT(WEAK == Internals::kNodeStateIsWeakValue);
STATIC_ASSERT(PENDING == Internals::kNodeStateIsPendingValue);
STATIC_ASSERT(NEAR_DEATH == Internals::kNodeStateIsNearDeathValue);
STATIC_ASSERT(static_cast<int>(IsIndependent::kShift) ==
Internals::kNodeIsIndependentShift);
STATIC_ASSERT(static_cast<int>(IsActive::kShift) ==
Internals::kNodeIsActiveShift);
}
#ifdef ENABLE_HANDLE_ZAPPING
~Node() {
// TODO(1428): if it's a weak handle we should have invoked its callback.
// Zap the values for eager trapping.
object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
index_ = 0;
set_independent(false);
set_active(false);
set_in_new_space_list(false);
parameter_or_next_free_.next_free = NULL;
weak_callback_ = NULL;
}
#endif
void Initialize(int index, Node** first_free) {
object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
index_ = static_cast<uint8_t>(index);
DCHECK(static_cast<int>(index_) == index);
set_state(FREE);
set_in_new_space_list(false);
parameter_or_next_free_.next_free = *first_free;
*first_free = this;
}
void Acquire(Object* object) {
DCHECK(state() == FREE);
object_ = object;
class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
set_independent(false);
set_active(false);
set_state(NORMAL);
parameter_or_next_free_.parameter = NULL;
weak_callback_ = NULL;
IncreaseBlockUses();
}
void Zap() {
DCHECK(IsInUse());
// Zap the values for eager trapping.
object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
}
void Release() {
DCHECK(IsInUse());
set_state(FREE);
// Zap the values for eager trapping.
object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
set_independent(false);
set_active(false);
weak_callback_ = NULL;
DecreaseBlockUses();
}
// Object slot accessors.
Object* object() const { return object_; }
Object** location() { return &object_; }
Handle<Object> handle() { return Handle<Object>(location()); }
// Wrapper class ID accessors.
bool has_wrapper_class_id() const {
return class_id_ != v8::HeapProfiler::kPersistentHandleNoClassId;
}
uint16_t wrapper_class_id() const { return class_id_; }
// State and flag accessors.
State state() const {
return NodeState::decode(flags_);
}
void set_state(State state) {
flags_ = NodeState::update(flags_, state);
}
bool is_independent() {
return IsIndependent::decode(flags_);
}
void set_independent(bool v) {
flags_ = IsIndependent::update(flags_, v);
}
bool is_active() {
return IsActive::decode(flags_);
}
void set_active(bool v) {
flags_ = IsActive::update(flags_, v);
}
bool is_in_new_space_list() {
return IsInNewSpaceList::decode(flags_);
}
void set_in_new_space_list(bool v) {
flags_ = IsInNewSpaceList::update(flags_, v);
}
WeaknessType weakness_type() const {
return NodeWeaknessType::decode(flags_);
}
void set_weakness_type(WeaknessType weakness_type) {
flags_ = NodeWeaknessType::update(flags_, weakness_type);
}
bool IsNearDeath() const {
// Check for PENDING to ensure correct answer when processing callbacks.
return state() == PENDING || state() == NEAR_DEATH;
}
bool IsWeak() const { return state() == WEAK; }
bool IsInUse() const { return state() != FREE; }
bool IsPendingPhantomCallback() const {
return state() == PENDING &&
(weakness_type() == PHANTOM_WEAK ||
weakness_type() == PHANTOM_WEAK_2_INTERNAL_FIELDS);
}
bool IsPendingPhantomResetHandle() const {
return state() == PENDING && weakness_type() == PHANTOM_WEAK_RESET_HANDLE;
}
bool IsRetainer() const {
return state() != FREE &&
!(state() == NEAR_DEATH && weakness_type() != FINALIZER_WEAK);
}
bool IsStrongRetainer() const { return state() == NORMAL; }
bool IsWeakRetainer() const {
return state() == WEAK || state() == PENDING ||
(state() == NEAR_DEATH && weakness_type() == FINALIZER_WEAK);
}
void MarkPending() {
DCHECK(state() == WEAK);
set_state(PENDING);
}
// Independent flag accessors.
void MarkIndependent() {
DCHECK(IsInUse());
set_independent(true);
}
// Callback accessor.
// TODO(svenpanne) Re-enable or nuke later.
// WeakReferenceCallback callback() { return callback_; }
// Callback parameter accessors.
void set_parameter(void* parameter) {
DCHECK(IsInUse());
parameter_or_next_free_.parameter = parameter;
}
void* parameter() const {
DCHECK(IsInUse());
return parameter_or_next_free_.parameter;
}
// Accessors for next free node in the free list.
Node* next_free() {
DCHECK(state() == FREE);
return parameter_or_next_free_.next_free;
}
void set_next_free(Node* value) {
DCHECK(state() == FREE);
parameter_or_next_free_.next_free = value;
}
void MakeWeak(void* parameter,
WeakCallbackInfo<void>::Callback phantom_callback,
v8::WeakCallbackType type) {
DCHECK(phantom_callback != nullptr);
DCHECK(IsInUse());
CHECK_NE(object_, reinterpret_cast<Object*>(kGlobalHandleZapValue));
set_state(WEAK);
switch (type) {
case v8::WeakCallbackType::kParameter:
set_weakness_type(PHANTOM_WEAK);
break;
case v8::WeakCallbackType::kInternalFields:
set_weakness_type(PHANTOM_WEAK_2_INTERNAL_FIELDS);
break;
case v8::WeakCallbackType::kFinalizer:
set_weakness_type(FINALIZER_WEAK);
break;
}
set_parameter(parameter);
weak_callback_ = phantom_callback;
}
void MakeWeak(Object*** location_addr) {
DCHECK(IsInUse());
CHECK_NE(object_, reinterpret_cast<Object*>(kGlobalHandleZapValue));
set_state(WEAK);
set_weakness_type(PHANTOM_WEAK_RESET_HANDLE);
set_parameter(location_addr);
weak_callback_ = nullptr;
}
void* ClearWeakness() {
DCHECK(IsInUse());
void* p = parameter();
set_state(NORMAL);
set_parameter(NULL);
return p;
}
void CollectPhantomCallbackData(
Isolate* isolate,
List<PendingPhantomCallback>* pending_phantom_callbacks) {
DCHECK(weakness_type() == PHANTOM_WEAK ||
weakness_type() == PHANTOM_WEAK_2_INTERNAL_FIELDS);
DCHECK(state() == PENDING);
DCHECK(weak_callback_ != nullptr);
void* internal_fields[v8::kInternalFieldsInWeakCallback] = {nullptr,
nullptr};
if (weakness_type() != PHANTOM_WEAK && object()->IsJSObject()) {
auto jsobject = JSObject::cast(object());
int field_count = jsobject->GetInternalFieldCount();
for (int i = 0; i < v8::kInternalFieldsInWeakCallback; ++i) {
if (field_count == i) break;
auto field = jsobject->GetInternalField(i);
if (field->IsSmi()) internal_fields[i] = field;
}
}
// Zap with something dangerous.
*location() = reinterpret_cast<Object*>(0x6057ca11);
typedef v8::WeakCallbackInfo<void> Data;
auto callback = reinterpret_cast<Data::Callback>(weak_callback_);
pending_phantom_callbacks->Add(
PendingPhantomCallback(this, callback, parameter(), internal_fields));
DCHECK(IsInUse());
set_state(NEAR_DEATH);
}
void ResetPhantomHandle() {
DCHECK(weakness_type() == PHANTOM_WEAK_RESET_HANDLE);
DCHECK(state() == PENDING);
DCHECK(weak_callback_ == nullptr);
Object*** handle = reinterpret_cast<Object***>(parameter());
*handle = nullptr;
Release();
}
bool PostGarbageCollectionProcessing(Isolate* isolate) {
// Handles only weak handles (not phantom) that are dying.
if (state() != Node::PENDING) return false;
if (weak_callback_ == NULL) {
Release();
return false;
}
set_state(NEAR_DEATH);
// Check that we are not passing a finalized external string to
// the callback.
DCHECK(!object_->IsExternalOneByteString() ||
ExternalOneByteString::cast(object_)->resource() != NULL);
DCHECK(!object_->IsExternalTwoByteString() ||
ExternalTwoByteString::cast(object_)->resource() != NULL);
if (weakness_type() != FINALIZER_WEAK) {
return false;
}
// Leaving V8.
VMState<EXTERNAL> vmstate(isolate);
HandleScope handle_scope(isolate);
void* internal_fields[v8::kInternalFieldsInWeakCallback] = {nullptr,
nullptr};
v8::WeakCallbackInfo<void> data(reinterpret_cast<v8::Isolate*>(isolate),
parameter(), internal_fields, nullptr);
weak_callback_(data);
// Absence of explicit cleanup or revival of weak handle
// in most of the cases would lead to memory leak.
CHECK(state() != NEAR_DEATH);
return true;
}
inline GlobalHandles* GetGlobalHandles();
private:
inline NodeBlock* FindBlock();
inline void IncreaseBlockUses();
inline void DecreaseBlockUses();
// Storage for object pointer.
// Placed first to avoid offset computation.
Object* object_;
// Next word stores class_id, index, state, and independent.
// Note: the most aligned fields should go first.
// Wrapper class ID.
uint16_t class_id_;
// Index in the containing handle block.
uint8_t index_;
// This stores three flags (independent, partially_dependent and
// in_new_space_list) and a State.
class NodeState : public BitField<State, 0, 3> {};
class IsIndependent : public BitField<bool, 3, 1> {};
// The following two fields are mutually exclusive
class IsActive : public BitField<bool, 4, 1> {};
class IsInNewSpaceList : public BitField<bool, 5, 1> {};
class NodeWeaknessType : public BitField<WeaknessType, 6, 2> {};
uint8_t flags_;
// Handle specific callback - might be a weak reference in disguise.
WeakCallbackInfo<void>::Callback weak_callback_;
// Provided data for callback. In FREE state, this is used for
// the free list link.
union {
void* parameter;
Node* next_free;
} parameter_or_next_free_;
DISALLOW_COPY_AND_ASSIGN(Node);
};
class GlobalHandles::NodeBlock {
public:
static const int kSize = 256;
explicit NodeBlock(GlobalHandles* global_handles, NodeBlock* next)
: next_(next),
used_nodes_(0),
next_used_(NULL),
prev_used_(NULL),
global_handles_(global_handles) {}
void PutNodesOnFreeList(Node** first_free) {
for (int i = kSize - 1; i >= 0; --i) {
nodes_[i].Initialize(i, first_free);
}
}
Node* node_at(int index) {
DCHECK(0 <= index && index < kSize);
return &nodes_[index];
}
void IncreaseUses() {
DCHECK(used_nodes_ < kSize);
if (used_nodes_++ == 0) {
NodeBlock* old_first = global_handles_->first_used_block_;
global_handles_->first_used_block_ = this;
next_used_ = old_first;
prev_used_ = NULL;
if (old_first == NULL) return;
old_first->prev_used_ = this;
}
}
void DecreaseUses() {
DCHECK(used_nodes_ > 0);
if (--used_nodes_ == 0) {
if (next_used_ != NULL) next_used_->prev_used_ = prev_used_;
if (prev_used_ != NULL) prev_used_->next_used_ = next_used_;
if (this == global_handles_->first_used_block_) {
global_handles_->first_used_block_ = next_used_;
}
}
}
GlobalHandles* global_handles() { return global_handles_; }
// Next block in the list of all blocks.
NodeBlock* next() const { return next_; }
// Next/previous block in the list of blocks with used nodes.
NodeBlock* next_used() const { return next_used_; }
NodeBlock* prev_used() const { return prev_used_; }
private:
Node nodes_[kSize];
NodeBlock* const next_;
int used_nodes_;
NodeBlock* next_used_;
NodeBlock* prev_used_;
GlobalHandles* global_handles_;
};
GlobalHandles* GlobalHandles::Node::GetGlobalHandles() {
return FindBlock()->global_handles();
}
GlobalHandles::NodeBlock* GlobalHandles::Node::FindBlock() {
intptr_t ptr = reinterpret_cast<intptr_t>(this);
ptr = ptr - index_ * sizeof(Node);
NodeBlock* block = reinterpret_cast<NodeBlock*>(ptr);
DCHECK(block->node_at(index_) == this);
return block;
}
void GlobalHandles::Node::IncreaseBlockUses() {
NodeBlock* node_block = FindBlock();
node_block->IncreaseUses();
GlobalHandles* global_handles = node_block->global_handles();
global_handles->isolate()->counters()->global_handles()->Increment();
global_handles->number_of_global_handles_++;
}
void GlobalHandles::Node::DecreaseBlockUses() {
NodeBlock* node_block = FindBlock();
GlobalHandles* global_handles = node_block->global_handles();
parameter_or_next_free_.next_free = global_handles->first_free_;
global_handles->first_free_ = this;
node_block->DecreaseUses();
global_handles->isolate()->counters()->global_handles()->Decrement();
global_handles->number_of_global_handles_--;
}
class GlobalHandles::NodeIterator {
public:
explicit NodeIterator(GlobalHandles* global_handles)
: block_(global_handles->first_used_block_),
index_(0) {}
bool done() const { return block_ == NULL; }
Node* node() const {
DCHECK(!done());
return block_->node_at(index_);
}
void Advance() {
DCHECK(!done());
if (++index_ < NodeBlock::kSize) return;
index_ = 0;
block_ = block_->next_used();
}
private:
NodeBlock* block_;
int index_;
DISALLOW_COPY_AND_ASSIGN(NodeIterator);
};
class GlobalHandles::PendingPhantomCallbacksSecondPassTask
: public v8::internal::CancelableTask {
public:
// Takes ownership of the contents of pending_phantom_callbacks, leaving it in
// the same state it would be after a call to Clear().
PendingPhantomCallbacksSecondPassTask(
List<PendingPhantomCallback>* pending_phantom_callbacks, Isolate* isolate)
: CancelableTask(isolate) {
pending_phantom_callbacks_.Swap(pending_phantom_callbacks);
}
void RunInternal() override {
TRACE_EVENT0("v8", "V8.GCPhantomHandleProcessingCallback");
isolate()->heap()->CallGCPrologueCallbacks(
GCType::kGCTypeProcessWeakCallbacks, kNoGCCallbackFlags);
InvokeSecondPassPhantomCallbacks(&pending_phantom_callbacks_, isolate());
isolate()->heap()->CallGCEpilogueCallbacks(
GCType::kGCTypeProcessWeakCallbacks, kNoGCCallbackFlags);
}
private:
List<PendingPhantomCallback> pending_phantom_callbacks_;
DISALLOW_COPY_AND_ASSIGN(PendingPhantomCallbacksSecondPassTask);
};
GlobalHandles::GlobalHandles(Isolate* isolate)
: isolate_(isolate),
number_of_global_handles_(0),
first_block_(NULL),
first_used_block_(NULL),
first_free_(NULL),
post_gc_processing_count_(0),
number_of_phantom_handle_resets_(0),
object_group_connections_(kObjectGroupConnectionsCapacity) {}
GlobalHandles::~GlobalHandles() {
NodeBlock* block = first_block_;
while (block != NULL) {
NodeBlock* tmp = block->next();
delete block;
block = tmp;
}
first_block_ = NULL;
}
Handle<Object> GlobalHandles::Create(Object* value) {
if (first_free_ == NULL) {
first_block_ = new NodeBlock(this, first_block_);
first_block_->PutNodesOnFreeList(&first_free_);
}
DCHECK(first_free_ != NULL);
// Take the first node in the free list.
Node* result = first_free_;
first_free_ = result->next_free();
result->Acquire(value);
if (isolate_->heap()->InNewSpace(value) &&
!result->is_in_new_space_list()) {
new_space_nodes_.Add(result);
result->set_in_new_space_list(true);
}
return result->handle();
}
Handle<Object> GlobalHandles::CopyGlobal(Object** location) {
DCHECK(location != NULL);
return Node::FromLocation(location)->GetGlobalHandles()->Create(*location);
}
void GlobalHandles::Destroy(Object** location) {
if (location != NULL) Node::FromLocation(location)->Release();
}
typedef v8::WeakCallbackInfo<void>::Callback GenericCallback;
void GlobalHandles::MakeWeak(Object** location, void* parameter,
GenericCallback phantom_callback,
v8::WeakCallbackType type) {
Node::FromLocation(location)->MakeWeak(parameter, phantom_callback, type);
}
void GlobalHandles::MakeWeak(Object*** location_addr) {
Node::FromLocation(*location_addr)->MakeWeak(location_addr);
}
void* GlobalHandles::ClearWeakness(Object** location) {
return Node::FromLocation(location)->ClearWeakness();
}
void GlobalHandles::MarkIndependent(Object** location) {
Node::FromLocation(location)->MarkIndependent();
}
bool GlobalHandles::IsIndependent(Object** location) {
return Node::FromLocation(location)->is_independent();
}
bool GlobalHandles::IsNearDeath(Object** location) {
return Node::FromLocation(location)->IsNearDeath();
}
bool GlobalHandles::IsWeak(Object** location) {
return Node::FromLocation(location)->IsWeak();
}
DISABLE_CFI_PERF
void GlobalHandles::IterateWeakRoots(ObjectVisitor* v) {
for (NodeIterator it(this); !it.done(); it.Advance()) {
Node* node = it.node();
if (node->IsWeakRetainer()) {
// Pending weak phantom handles die immediately. Everything else survives.
if (node->IsPendingPhantomResetHandle()) {
node->ResetPhantomHandle();
++number_of_phantom_handle_resets_;
} else if (node->IsPendingPhantomCallback()) {
node->CollectPhantomCallbackData(isolate(),
&pending_phantom_callbacks_);
} else {
v->VisitPointer(node->location());
}
}
}
}
void GlobalHandles::IdentifyWeakHandles(WeakSlotCallback f) {
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (it.node()->IsWeak() && f(it.node()->location())) {
it.node()->MarkPending();
}
}
}
void GlobalHandles::IterateNewSpaceStrongAndDependentRoots(ObjectVisitor* v) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
if (node->IsStrongRetainer() ||
(node->IsWeakRetainer() && !node->is_independent() &&
node->is_active())) {
v->VisitPointer(node->location());
}
}
}
void GlobalHandles::IdentifyNewSpaceWeakIndependentHandles(
WeakSlotCallbackWithHeap f) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
DCHECK(node->is_in_new_space_list());
if (node->is_independent() && node->IsWeak() &&
f(isolate_->heap(), node->location())) {
node->MarkPending();
}
}
}
void GlobalHandles::IterateNewSpaceWeakIndependentRoots(ObjectVisitor* v) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
DCHECK(node->is_in_new_space_list());
if (node->is_independent() && node->IsWeakRetainer()) {
// Pending weak phantom handles die immediately. Everything else survives.
if (node->IsPendingPhantomResetHandle()) {
node->ResetPhantomHandle();
++number_of_phantom_handle_resets_;
} else if (node->IsPendingPhantomCallback()) {
node->CollectPhantomCallbackData(isolate(),
&pending_phantom_callbacks_);
} else {
v->VisitPointer(node->location());
}
}
}
}
void GlobalHandles::IdentifyWeakUnmodifiedObjects(
WeakSlotCallback is_unmodified) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
if (node->IsWeak() && !is_unmodified(node->location())) {
node->set_active(true);
}
}
}
void GlobalHandles::MarkNewSpaceWeakUnmodifiedObjectsPending(
WeakSlotCallbackWithHeap is_unscavenged) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
DCHECK(node->is_in_new_space_list());
if ((node->is_independent() || !node->is_active()) && node->IsWeak() &&
is_unscavenged(isolate_->heap(), node->location())) {
node->MarkPending();
}
}
}
void GlobalHandles::IterateNewSpaceWeakUnmodifiedRoots(ObjectVisitor* v) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
DCHECK(node->is_in_new_space_list());
if ((node->is_independent() || !node->is_active()) &&
node->IsWeakRetainer()) {
// Pending weak phantom handles die immediately. Everything else survives.
if (node->IsPendingPhantomResetHandle()) {
node->ResetPhantomHandle();
++number_of_phantom_handle_resets_;
} else if (node->IsPendingPhantomCallback()) {
node->CollectPhantomCallbackData(isolate(),
&pending_phantom_callbacks_);
} else {
v->VisitPointer(node->location());
}
}
}
}
DISABLE_CFI_PERF
bool GlobalHandles::IterateObjectGroups(ObjectVisitor* v,
WeakSlotCallbackWithHeap can_skip) {
ComputeObjectGroupsAndImplicitReferences();
int last = 0;
bool any_group_was_visited = false;
for (int i = 0; i < object_groups_.length(); i++) {
ObjectGroup* entry = object_groups_.at(i);
DCHECK(entry != NULL);
Object*** objects = entry->objects;
bool group_should_be_visited = false;
for (size_t j = 0; j < entry->length; j++) {
Object* object = *objects[j];
if (object->IsHeapObject()) {
if (!can_skip(isolate_->heap(), &object)) {
group_should_be_visited = true;
break;
}
}
}
if (!group_should_be_visited) {
object_groups_[last++] = entry;
continue;
}
// An object in the group requires visiting, so iterate over all
// objects in the group.
for (size_t j = 0; j < entry->length; ++j) {
Object* object = *objects[j];
if (object->IsHeapObject()) {
v->VisitPointer(&object);
any_group_was_visited = true;
}
}
// Once the entire group has been iterated over, set the object
// group to NULL so it won't be processed again.
delete entry;
object_groups_.at(i) = NULL;
}
object_groups_.Rewind(last);
return any_group_was_visited;
}
namespace {
// Traces the information about object groups and implicit ref groups given by
// the embedder to the V8 during each gc prologue.
class ObjectGroupsTracer {
public:
explicit ObjectGroupsTracer(Isolate* isolate);
void Print();
private:
void PrintObjectGroup(ObjectGroup* group);
void PrintImplicitRefGroup(ImplicitRefGroup* group);
void PrintObject(Object* object);
void PrintConstructor(JSObject* js_object);
void PrintInternalFields(JSObject* js_object);
Isolate* isolate_;
DISALLOW_COPY_AND_ASSIGN(ObjectGroupsTracer);
};
ObjectGroupsTracer::ObjectGroupsTracer(Isolate* isolate) : isolate_(isolate) {}
void ObjectGroupsTracer::Print() {
GlobalHandles* global_handles = isolate_->global_handles();
PrintIsolate(isolate_, "### Tracing object groups:\n");
for (auto group : *(global_handles->object_groups())) {
PrintObjectGroup(group);
}
for (auto group : *(global_handles->implicit_ref_groups())) {
PrintImplicitRefGroup(group);
}
PrintIsolate(isolate_, "### Tracing object groups finished.\n");
}
void ObjectGroupsTracer::PrintObject(Object* object) {
if (object->IsJSObject()) {
JSObject* js_object = JSObject::cast(object);
PrintF("{ constructor_name: ");
PrintConstructor(js_object);
PrintF(", hidden_fields: [ ");
PrintInternalFields(js_object);
PrintF(" ] }\n");
} else {
PrintF("object of unexpected type: %p\n", static_cast<void*>(object));
}
}
void ObjectGroupsTracer::PrintConstructor(JSObject* js_object) {
Object* maybe_constructor = js_object->map()->GetConstructor();
if (maybe_constructor->IsJSFunction()) {
JSFunction* constructor = JSFunction::cast(maybe_constructor);
String* name = String::cast(constructor->shared()->name());
if (name->length() == 0) name = constructor->shared()->inferred_name();
PrintF("%s", name->ToCString().get());
} else if (maybe_constructor->IsNull(isolate_)) {
if (js_object->IsOddball()) {
PrintF("<oddball>");
} else {
PrintF("<null>");
}
} else {
UNREACHABLE();
}
}
void ObjectGroupsTracer::PrintInternalFields(JSObject* js_object) {
for (int i = 0; i < js_object->GetInternalFieldCount(); ++i) {
if (i != 0) {
PrintF(", ");
}
PrintF("%p", static_cast<void*>(js_object->GetInternalField(i)));
}
}
void ObjectGroupsTracer::PrintObjectGroup(ObjectGroup* group) {
PrintIsolate(isolate_, "ObjectGroup (size: %" PRIuS ")\n", group->length);
Object*** objects = group->objects;
for (size_t i = 0; i < group->length; ++i) {
PrintIsolate(isolate_, " - Member: ");
PrintObject(*objects[i]);
}
}
void ObjectGroupsTracer::PrintImplicitRefGroup(ImplicitRefGroup* group) {
PrintIsolate(isolate_, "ImplicitRefGroup (children count: %" PRIuS ")\n",
group->length);
PrintIsolate(isolate_, " - Parent: ");
PrintObject(*(group->parent));
Object*** children = group->children;
for (size_t i = 0; i < group->length; ++i) {
PrintIsolate(isolate_, " - Child: ");
PrintObject(*children[i]);
}
}
} // namespace
void GlobalHandles::PrintObjectGroups() {
ObjectGroupsTracer(isolate_).Print();
}
void GlobalHandles::InvokeSecondPassPhantomCallbacks(
List<PendingPhantomCallback>* callbacks, Isolate* isolate) {
while (callbacks->length() != 0) {
auto callback = callbacks->RemoveLast();
DCHECK(callback.node() == nullptr);
// Fire second pass callback
callback.Invoke(isolate);
}
}
int GlobalHandles::PostScavengeProcessing(
const int initial_post_gc_processing_count) {
int freed_nodes = 0;
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
DCHECK(node->is_in_new_space_list());
if (!node->IsRetainer()) {
// Free nodes do not have weak callbacks. Do not use them to compute
// the freed_nodes.
continue;
}
// Skip dependent or unmodified handles. Their weak callbacks might expect
// to be
// called between two global garbage collection callbacks which
// are not called for minor collections.
if (!node->is_independent() && (node->is_active())) {
node->set_active(false);
continue;
}
node->set_active(false);
if (node->PostGarbageCollectionProcessing(isolate_)) {
if (initial_post_gc_processing_count != post_gc_processing_count_) {
// Weak callback triggered another GC and another round of
// PostGarbageCollection processing. The current node might
// have been deleted in that round, so we need to bail out (or
// restart the processing).
return freed_nodes;
}
}
if (!node->IsRetainer()) {
freed_nodes++;
}
}
return freed_nodes;
}
int GlobalHandles::PostMarkSweepProcessing(
const int initial_post_gc_processing_count) {
int freed_nodes = 0;
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (!it.node()->IsRetainer()) {
// Free nodes do not have weak callbacks. Do not use them to compute
// the freed_nodes.
continue;
}
it.node()->set_active(false);
if (it.node()->PostGarbageCollectionProcessing(isolate_)) {
if (initial_post_gc_processing_count != post_gc_processing_count_) {
// See the comment above.
return freed_nodes;
}
}
if (!it.node()->IsRetainer()) {
freed_nodes++;
}
}
return freed_nodes;
}
void GlobalHandles::UpdateListOfNewSpaceNodes() {
int last = 0;
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
DCHECK(node->is_in_new_space_list());
if (node->IsRetainer()) {
if (isolate_->heap()->InNewSpace(node->object())) {
new_space_nodes_[last++] = node;
isolate_->heap()->IncrementNodesCopiedInNewSpace();
} else {
node->set_in_new_space_list(false);
isolate_->heap()->IncrementNodesPromoted();
}
} else {
node->set_in_new_space_list(false);
isolate_->heap()->IncrementNodesDiedInNewSpace();
}
}
new_space_nodes_.Rewind(last);
new_space_nodes_.Trim();
}
int GlobalHandles::DispatchPendingPhantomCallbacks(
bool synchronous_second_pass) {
int freed_nodes = 0;
List<PendingPhantomCallback> second_pass_callbacks;
{
// The initial pass callbacks must simply clear the nodes.
for (auto i = pending_phantom_callbacks_.begin();
i != pending_phantom_callbacks_.end(); ++i) {
auto callback = i;
// Skip callbacks that have already been processed once.
if (callback->node() == nullptr) continue;
callback->Invoke(isolate());
if (callback->callback()) second_pass_callbacks.Add(*callback);
freed_nodes++;
}
}
pending_phantom_callbacks_.Clear();
if (second_pass_callbacks.length() > 0) {
if (FLAG_optimize_for_size || FLAG_predictable || synchronous_second_pass) {
isolate()->heap()->CallGCPrologueCallbacks(
GCType::kGCTypeProcessWeakCallbacks, kNoGCCallbackFlags);
InvokeSecondPassPhantomCallbacks(&second_pass_callbacks, isolate());
isolate()->heap()->CallGCEpilogueCallbacks(
GCType::kGCTypeProcessWeakCallbacks, kNoGCCallbackFlags);
} else {
auto task = new PendingPhantomCallbacksSecondPassTask(
&second_pass_callbacks, isolate());
V8::GetCurrentPlatform()->CallOnForegroundThread(
reinterpret_cast<v8::Isolate*>(isolate()), task);
}
}
return freed_nodes;
}
void GlobalHandles::PendingPhantomCallback::Invoke(Isolate* isolate) {
Data::Callback* callback_addr = nullptr;
if (node_ != nullptr) {
// Initialize for first pass callback.
DCHECK(node_->state() == Node::NEAR_DEATH);
callback_addr = &callback_;
}
Data data(reinterpret_cast<v8::Isolate*>(isolate), parameter_,
internal_fields_, callback_addr);
Data::Callback callback = callback_;
callback_ = nullptr;
callback(data);
if (node_ != nullptr) {
// Transition to second pass state.
DCHECK(node_->state() == Node::FREE);
node_ = nullptr;
}
}
int GlobalHandles::PostGarbageCollectionProcessing(
GarbageCollector collector, const v8::GCCallbackFlags gc_callback_flags) {
// Process weak global handle callbacks. This must be done after the
// GC is completely done, because the callbacks may invoke arbitrary
// API functions.
DCHECK(isolate_->heap()->gc_state() == Heap::NOT_IN_GC);
const int initial_post_gc_processing_count = ++post_gc_processing_count_;
int freed_nodes = 0;
bool synchronous_second_pass =
(gc_callback_flags &
(kGCCallbackFlagForced | kGCCallbackFlagCollectAllAvailableGarbage |
kGCCallbackFlagSynchronousPhantomCallbackProcessing)) != 0;
freed_nodes += DispatchPendingPhantomCallbacks(synchronous_second_pass);
if (initial_post_gc_processing_count != post_gc_processing_count_) {
// If the callbacks caused a nested GC, then return. See comment in
// PostScavengeProcessing.
return freed_nodes;
}
if (collector == SCAVENGER) {
freed_nodes += PostScavengeProcessing(initial_post_gc_processing_count);
} else {
freed_nodes += PostMarkSweepProcessing(initial_post_gc_processing_count);
}
if (initial_post_gc_processing_count != post_gc_processing_count_) {
// If the callbacks caused a nested GC, then return. See comment in
// PostScavengeProcessing.
return freed_nodes;
}
if (initial_post_gc_processing_count == post_gc_processing_count_) {
UpdateListOfNewSpaceNodes();
}
return freed_nodes;
}
void GlobalHandles::IterateStrongRoots(ObjectVisitor* v) {
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (it.node()->IsStrongRetainer()) {
v->VisitPointer(it.node()->location());
}
}
}
DISABLE_CFI_PERF
void GlobalHandles::IterateAllRoots(ObjectVisitor* v) {
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (it.node()->IsRetainer()) {
v->VisitPointer(it.node()->location());
}
}
}
DISABLE_CFI_PERF
void GlobalHandles::IterateAllRootsWithClassIds(ObjectVisitor* v) {
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (it.node()->IsRetainer() && it.node()->has_wrapper_class_id()) {
v->VisitEmbedderReference(it.node()->location(),
it.node()->wrapper_class_id());
}
}
}
DISABLE_CFI_PERF
void GlobalHandles::IterateAllRootsInNewSpaceWithClassIds(ObjectVisitor* v) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
if (node->IsRetainer() && node->has_wrapper_class_id()) {
v->VisitEmbedderReference(node->location(),
node->wrapper_class_id());
}
}
}
DISABLE_CFI_PERF
void GlobalHandles::IterateWeakRootsInNewSpaceWithClassIds(ObjectVisitor* v) {
for (int i = 0; i < new_space_nodes_.length(); ++i) {
Node* node = new_space_nodes_[i];
if (node->has_wrapper_class_id() && node->IsWeak()) {
v->VisitEmbedderReference(node->location(), node->wrapper_class_id());
}
}
}
int GlobalHandles::NumberOfWeakHandles() {
int count = 0;
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (it.node()->IsWeakRetainer()) {
count++;
}
}
return count;
}
int GlobalHandles::NumberOfGlobalObjectWeakHandles() {
int count = 0;
for (NodeIterator it(this); !it.done(); it.Advance()) {
if (it.node()->IsWeakRetainer() &&
it.node()->object()->IsJSGlobalObject()) {
count++;
}
}
return count;
}
void GlobalHandles::RecordStats(HeapStats* stats) {
*stats->global_handle_count = 0;
*stats->weak_global_handle_count = 0;
*stats->pending_global_handle_count = 0;
*stats->near_death_global_handle_count = 0;
*stats->free_global_handle_count = 0;
for (NodeIterator it(this); !it.done(); it.Advance()) {
*stats->global_handle_count += 1;
if (it.node()->state() == Node::WEAK) {
*stats->weak_global_handle_count += 1;
} else if (it.node()->state() == Node::PENDING) {
*stats->pending_global_handle_count += 1;
} else if (it.node()->state() == Node::NEAR_DEATH) {
*stats->near_death_global_handle_count += 1;
} else if (it.node()->state() == Node::FREE) {
*stats->free_global_handle_count += 1;
}
}
}
#ifdef DEBUG
void GlobalHandles::PrintStats() {
int total = 0;
int weak = 0;
int pending = 0;
int near_death = 0;
int destroyed = 0;
for (NodeIterator it(this); !it.done(); it.Advance()) {
total++;
if (it.node()->state() == Node::WEAK) weak++;
if (it.node()->state() == Node::PENDING) pending++;
if (it.node()->state() == Node::NEAR_DEATH) near_death++;
if (it.node()->state() == Node::FREE) destroyed++;
}
PrintF("Global Handle Statistics:\n");
PrintF(" allocated memory = %" PRIuS "B\n", total * sizeof(Node));
PrintF(" # weak = %d\n", weak);
PrintF(" # pending = %d\n", pending);
PrintF(" # near_death = %d\n", near_death);
PrintF(" # free = %d\n", destroyed);
PrintF(" # total = %d\n", total);
}
void GlobalHandles::Print() {
PrintF("Global handles:\n");
for (NodeIterator it(this); !it.done(); it.Advance()) {
PrintF(" handle %p to %p%s\n",
reinterpret_cast<void*>(it.node()->location()),
reinterpret_cast<void*>(it.node()->object()),
it.node()->IsWeak() ? " (weak)" : "");
}
}
#endif
void GlobalHandles::AddObjectGroup(Object*** handles,
size_t length,
v8::RetainedObjectInfo* info) {
#ifdef DEBUG
for (size_t i = 0; i < length; ++i) {
DCHECK(!Node::FromLocation(handles[i])->is_independent());
}
#endif
if (length == 0) {
if (info != NULL) info->Dispose();
return;
}
ObjectGroup* group = new ObjectGroup(length);
for (size_t i = 0; i < length; ++i)
group->objects[i] = handles[i];
group->info = info;
object_groups_.Add(group);
}
void GlobalHandles::SetObjectGroupId(Object** handle,
UniqueId id) {
object_group_connections_.Add(ObjectGroupConnection(id, handle));
}
void GlobalHandles::SetRetainedObjectInfo(UniqueId id,
RetainedObjectInfo* info) {
retainer_infos_.Add(ObjectGroupRetainerInfo(id, info));
}
void GlobalHandles::SetReferenceFromGroup(UniqueId id, Object** child) {
DCHECK(!Node::FromLocation(child)->is_independent());
implicit_ref_connections_.Add(ObjectGroupConnection(id, child));
}
void GlobalHandles::SetReference(HeapObject** parent, Object** child) {
DCHECK(!Node::FromLocation(child)->is_independent());
ImplicitRefGroup* group = new ImplicitRefGroup(parent, 1);
group->children[0] = child;
implicit_ref_groups_.Add(group);
}
void GlobalHandles::RemoveObjectGroups() {
for (int i = 0; i < object_groups_.length(); i++)
delete object_groups_.at(i);
object_groups_.Clear();
for (int i = 0; i < retainer_infos_.length(); ++i)
retainer_infos_[i].info->Dispose();
retainer_infos_.Clear();
object_group_connections_.Clear();
object_group_connections_.Initialize(kObjectGroupConnectionsCapacity);
}
void GlobalHandles::RemoveImplicitRefGroups() {
for (int i = 0; i < implicit_ref_groups_.length(); i++) {
delete implicit_ref_groups_.at(i);
}
implicit_ref_groups_.Clear();
implicit_ref_connections_.Clear();
}
void GlobalHandles::TearDown() {
// TODO(1428): invoke weak callbacks.
}
void GlobalHandles::ComputeObjectGroupsAndImplicitReferences() {
if (object_group_connections_.length() == 0) {
for (int i = 0; i < retainer_infos_.length(); ++i)
retainer_infos_[i].info->Dispose();
retainer_infos_.Clear();
implicit_ref_connections_.Clear();
return;
}
object_group_connections_.Sort();
retainer_infos_.Sort();
implicit_ref_connections_.Sort();
int info_index = 0; // For iterating retainer_infos_.
UniqueId current_group_id(0);
int current_group_start = 0;
int current_implicit_refs_start = 0;
int current_implicit_refs_end = 0;
for (int i = 0; i <= object_group_connections_.length(); ++i) {
if (i == 0)
current_group_id = object_group_connections_[i].id;
if (i == object_group_connections_.length() ||
current_group_id != object_group_connections_[i].id) {
// Group detected: objects in indices [current_group_start, i[.
// Find out which implicit references are related to this group. (We want
// to ignore object groups which only have 1 object, but that object is
// needed as a representative object for the implicit refrerence group.)
while (current_implicit_refs_start < implicit_ref_connections_.length() &&
implicit_ref_connections_[current_implicit_refs_start].id <
current_group_id)
++current_implicit_refs_start;
current_implicit_refs_end = current_implicit_refs_start;
while (current_implicit_refs_end < implicit_ref_connections_.length() &&
implicit_ref_connections_[current_implicit_refs_end].id ==
current_group_id)
++current_implicit_refs_end;
if (current_implicit_refs_end > current_implicit_refs_start) {
// Find a representative object for the implicit references.
HeapObject** representative = NULL;
for (int j = current_group_start; j < i; ++j) {
Object** object = object_group_connections_[j].object;
if ((*object)->IsHeapObject()) {
representative = reinterpret_cast<HeapObject**>(object);
break;
}
}
if (representative) {
ImplicitRefGroup* group = new ImplicitRefGroup(
representative,
current_implicit_refs_end - current_implicit_refs_start);
for (int j = current_implicit_refs_start;
j < current_implicit_refs_end;
++j) {
group->children[j - current_implicit_refs_start] =
implicit_ref_connections_[j].object;
}
implicit_ref_groups_.Add(group);
}
current_implicit_refs_start = current_implicit_refs_end;
}
// Find a RetainedObjectInfo for the group.
RetainedObjectInfo* info = NULL;
while (info_index < retainer_infos_.length() &&
retainer_infos_[info_index].id < current_group_id) {
retainer_infos_[info_index].info->Dispose();
++info_index;
}
if (info_index < retainer_infos_.length() &&
retainer_infos_[info_index].id == current_group_id) {
// This object group has an associated ObjectGroupRetainerInfo.
info = retainer_infos_[info_index].info;
++info_index;
}
// Ignore groups which only contain one object.
if (i > current_group_start + 1) {
ObjectGroup* group = new ObjectGroup(i - current_group_start);
for (int j = current_group_start; j < i; ++j) {
group->objects[j - current_group_start] =
object_group_connections_[j].object;
}
group->info = info;
object_groups_.Add(group);
} else if (info) {
info->Dispose();
}
if (i < object_group_connections_.length()) {
current_group_id = object_group_connections_[i].id;
current_group_start = i;
}
}
}
object_group_connections_.Clear();
object_group_connections_.Initialize(kObjectGroupConnectionsCapacity);
retainer_infos_.Clear();
implicit_ref_connections_.Clear();
}
EternalHandles::EternalHandles() : size_(0) {
for (unsigned i = 0; i < arraysize(singleton_handles_); i++) {
singleton_handles_[i] = kInvalidIndex;
}
}
EternalHandles::~EternalHandles() {
for (int i = 0; i < blocks_.length(); i++) delete[] blocks_[i];
}
void EternalHandles::IterateAllRoots(ObjectVisitor* visitor) {
int limit = size_;
for (int i = 0; i < blocks_.length(); i++) {
DCHECK(limit > 0);
Object** block = blocks_[i];
visitor->VisitPointers(block, block + Min(limit, kSize));
limit -= kSize;
}
}
void EternalHandles::IterateNewSpaceRoots(ObjectVisitor* visitor) {
for (int i = 0; i < new_space_indices_.length(); i++) {
visitor->VisitPointer(GetLocation(new_space_indices_[i]));
}
}
void EternalHandles::PostGarbageCollectionProcessing(Heap* heap) {
int last = 0;
for (int i = 0; i < new_space_indices_.length(); i++) {
int index = new_space_indices_[i];
if (heap->InNewSpace(*GetLocation(index))) {
new_space_indices_[last++] = index;
}
}
new_space_indices_.Rewind(last);
}
void EternalHandles::Create(Isolate* isolate, Object* object, int* index) {
DCHECK_EQ(kInvalidIndex, *index);
if (object == NULL) return;
DCHECK_NE(isolate->heap()->the_hole_value(), object);
int block = size_ >> kShift;
int offset = size_ & kMask;
// need to resize
if (offset == 0) {
Object** next_block = new Object*[kSize];
Object* the_hole = isolate->heap()->the_hole_value();
MemsetPointer(next_block, the_hole, kSize);
blocks_.Add(next_block);
}
DCHECK_EQ(isolate->heap()->the_hole_value(), blocks_[block][offset]);
blocks_[block][offset] = object;
if (isolate->heap()->InNewSpace(object)) {
new_space_indices_.Add(size_);
}
*index = size_++;
}
} // namespace internal
} // namespace v8
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