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// Copyright 2015 The Chromium 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 "platform/heap/PersistentNode.h"
#include "base/debug/alias.h"
#include "platform/heap/Handle.h"
namespace blink {
namespace {
class DummyGCBase final : public GarbageCollected<DummyGCBase> {
public:
void Trace(blink::Visitor* visitor) {}
};
}
PersistentRegion::~PersistentRegion() {
PersistentNodeSlots* slots = slots_;
while (slots) {
PersistentNodeSlots* dead_slots = slots;
slots = slots->next_;
delete dead_slots;
}
}
int PersistentRegion::NumberOfPersistents() {
int persistent_count = 0;
for (PersistentNodeSlots* slots = slots_; slots; slots = slots->next_) {
for (int i = 0; i < PersistentNodeSlots::kSlotCount; ++i) {
if (!slots->slot_[i].IsUnused())
++persistent_count;
}
}
#if DCHECK_IS_ON()
DCHECK_EQ(persistent_count, persistent_count_);
#endif
return persistent_count;
}
void PersistentRegion::EnsurePersistentNodeSlots(void* self,
TraceCallback trace) {
DCHECK(!free_list_head_);
PersistentNodeSlots* slots = new PersistentNodeSlots;
for (int i = 0; i < PersistentNodeSlots::kSlotCount; ++i) {
PersistentNode* node = &slots->slot_[i];
node->SetFreeListNext(free_list_head_);
free_list_head_ = node;
DCHECK(node->IsUnused());
}
slots->next_ = slots_;
slots_ = slots;
}
void PersistentRegion::ReleasePersistentNode(
PersistentNode* persistent_node,
ThreadState::PersistentClearCallback callback) {
DCHECK(!persistent_node->IsUnused());
// 'self' is in use, containing the persistent wrapper object.
void* self = persistent_node->Self();
if (callback) {
(*callback)(self);
DCHECK(persistent_node->IsUnused());
return;
}
Persistent<DummyGCBase>* persistent =
reinterpret_cast<Persistent<DummyGCBase>*>(self);
persistent->Clear();
DCHECK(persistent_node->IsUnused());
}
// This function traces all PersistentNodes. If we encounter
// a PersistentNodeSlot that contains only freed PersistentNodes,
// we delete the PersistentNodeSlot. This function rebuilds the free
// list of PersistentNodes.
void PersistentRegion::TracePersistentNodes(Visitor* visitor,
ShouldTraceCallback should_trace) {
size_t debug_marked_object_size = ProcessHeap::TotalMarkedObjectSize();
base::debug::Alias(&debug_marked_object_size);
free_list_head_ = nullptr;
int persistent_count = 0;
PersistentNodeSlots** prev_next = &slots_;
PersistentNodeSlots* slots = slots_;
while (slots) {
PersistentNode* free_list_next = nullptr;
PersistentNode* free_list_last = nullptr;
int free_count = 0;
for (int i = 0; i < PersistentNodeSlots::kSlotCount; ++i) {
PersistentNode* node = &slots->slot_[i];
if (node->IsUnused()) {
if (!free_list_next)
free_list_last = node;
node->SetFreeListNext(free_list_next);
free_list_next = node;
++free_count;
} else {
++persistent_count;
if (!should_trace(visitor, node))
continue;
node->TracePersistentNode(visitor);
debug_marked_object_size = ProcessHeap::TotalMarkedObjectSize();
}
}
if (free_count == PersistentNodeSlots::kSlotCount) {
PersistentNodeSlots* dead_slots = slots;
*prev_next = slots->next_;
slots = slots->next_;
delete dead_slots;
} else {
if (free_list_last) {
DCHECK(free_list_next);
DCHECK(!free_list_last->FreeListNext());
free_list_last->SetFreeListNext(free_list_head_);
free_list_head_ = free_list_next;
}
prev_next = &slots->next_;
slots = slots->next_;
}
}
#if DCHECK_IS_ON()
DCHECK_EQ(persistent_count, persistent_count_);
#endif
}
void PersistentRegion::PrepareForThreadStateTermination() {
DCHECK(!IsMainThread());
PersistentNodeSlots* slots = slots_;
while (slots) {
for (int i = 0; i < PersistentNodeSlots::kSlotCount; ++i) {
PersistentNode* node = &slots->slot_[i];
if (node->IsUnused())
continue;
// It is safe to cast to Persistent<DummyGCBase> because persistent heap
// collections are banned in non-main threads.
Persistent<DummyGCBase>* persistent =
reinterpret_cast<Persistent<DummyGCBase>*>(node->Self());
DCHECK(persistent);
persistent->Clear();
DCHECK(node->IsUnused());
}
slots = slots->next_;
}
#if DCHECK_IS_ON()
DCHECK_EQ(persistent_count_, 0);
#endif
}
bool CrossThreadPersistentRegion::ShouldTracePersistentNode(
Visitor* visitor,
PersistentNode* node) {
CrossThreadPersistent<DummyGCBase>* persistent =
reinterpret_cast<CrossThreadPersistent<DummyGCBase>*>(node->Self());
DCHECK(persistent);
DCHECK(!persistent->IsHashTableDeletedValue());
Address raw_object = reinterpret_cast<Address>(persistent->Get());
if (!raw_object)
return false;
return &visitor->Heap() == &ThreadState::FromObject(raw_object)->Heap();
}
void CrossThreadPersistentRegion::PrepareForThreadStateTermination(
ThreadState* thread_state) {
// For heaps belonging to a thread that's detaching, any cross-thread
// persistents pointing into them needs to be disabled. Do that by clearing
// out the underlying heap reference.
MutexLocker lock(mutex_);
PersistentNodeSlots* slots = persistent_region_->slots_;
while (slots) {
for (int i = 0; i < PersistentNodeSlots::kSlotCount; ++i) {
if (slots->slot_[i].IsUnused())
continue;
// 'self' is in use, containing the cross-thread persistent wrapper
// object.
CrossThreadPersistent<DummyGCBase>* persistent =
reinterpret_cast<CrossThreadPersistent<DummyGCBase>*>(
slots->slot_[i].Self());
DCHECK(persistent);
void* raw_object = persistent->AtomicGet();
if (!raw_object)
continue;
BasePage* page = PageFromObject(raw_object);
DCHECK(page);
if (page->Arena()->GetThreadState() == thread_state) {
persistent->Clear();
DCHECK(slots->slot_[i].IsUnused());
}
}
slots = slots->next_;
}
}
#if defined(ADDRESS_SANITIZER)
void CrossThreadPersistentRegion::UnpoisonCrossThreadPersistents() {
MutexLocker lock(mutex_);
int persistent_count = 0;
for (PersistentNodeSlots* slots = persistent_region_->slots_; slots;
slots = slots->next_) {
for (int i = 0; i < PersistentNodeSlots::kSlotCount; ++i) {
const PersistentNode& node = slots->slot_[i];
if (!node.IsUnused()) {
ASAN_UNPOISON_MEMORY_REGION(node.Self(),
sizeof(CrossThreadPersistent<void*>));
++persistent_count;
}
}
}
#if DCHECK_IS_ON()
DCHECK_EQ(persistent_count, persistent_region_->persistent_count_);
#endif
}
#endif
} // namespace blink
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