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// Copyright 2018 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 "third_party/blink/renderer/platform/bindings/parkable_string.h"
#include "base/logging.h"
#include "base/metrics/histogram_macros.h"
#include "third_party/blink/renderer/platform/bindings/parkable_string_manager.h"
#include "third_party/blink/renderer/platform/wtf/address_sanitizer.h"
#include "third_party/blink/renderer/platform/wtf/thread_specific.h"
namespace blink {
namespace {
void RecordParkingAction(ParkableStringImpl::ParkingAction action) {
UMA_HISTOGRAM_ENUMERATION("Memory.MovableStringParkingAction", action);
}
#if defined(ADDRESS_SANITIZER)
void AsanPoisonString(const String& string) {
const void* start = string.Is8Bit()
? static_cast<const void*>(string.Characters8())
: static_cast<const void*>(string.Characters16());
ASAN_POISON_MEMORY_REGION(start, string.CharactersSizeInBytes());
}
void AsanUnpoisonString(const String& string) {
const void* start = string.Is8Bit()
? static_cast<const void*>(string.Characters8())
: static_cast<const void*>(string.Characters16());
ASAN_UNPOISON_MEMORY_REGION(start, string.CharactersSizeInBytes());
}
#endif // defined(ADDRESS_SANITIZER)
} // namespace
ParkableStringImpl::ParkableStringImpl(scoped_refptr<StringImpl>&& impl,
ParkableState parkable)
: mutex_(),
lock_depth_(0),
string_(std::move(impl)),
is_parked_(false),
is_parkable_(parkable == ParkableState::kParkable)
#if DCHECK_IS_ON()
,
owning_thread_(CurrentThread())
#endif
{
DCHECK(!string_.IsNull());
}
ParkableStringImpl::~ParkableStringImpl() {
AssertOnValidThread();
#if defined(ADDRESS_SANITIZER)
AsanUnpoisonString(string_);
#endif
if (is_parkable_)
ParkableStringManager::Instance().Remove(string_.Impl());
}
void ParkableStringImpl::Lock() {
MutexLocker locker(mutex_);
lock_depth_ += 1;
}
void ParkableStringImpl::Unlock() {
MutexLocker locker(mutex_);
DCHECK_GT(lock_depth_, 0);
lock_depth_ -= 1;
#if defined(ADDRESS_SANITIZER) && DCHECK_IS_ON()
// There are no external references to the data, nobody should touch the data.
//
// Note: Only poison the memory if this is on the owning thread, as this is
// otherwise racy. Indeed |Unlock()| may be called on any thread, and
// the owning thread may concurrently call |ToString()|. It is then allowed
// to use the string until the end of the current owning thread task.
// Requires DCHECK_IS_ON() for the |owning_thread_| check.
if (lock_depth_ == 0 && is_parkable_ && string_.Impl()->HasOneRef() &&
owning_thread_ == CurrentThread()) {
AsanPoisonString(string_);
}
#endif // defined(ADDRESS_SANITIZER) && DCHECK_IS_ON()
}
bool ParkableStringImpl::Is8Bit() const {
AssertOnValidThread();
return string_.Is8Bit();
}
bool ParkableStringImpl::IsNull() const {
AssertOnValidThread();
return string_.IsNull();
}
const String& ParkableStringImpl::ToString() {
AssertOnValidThread();
MutexLocker locker(mutex_);
#if defined(ADDRESS_SANITIZER)
AsanUnpoisonString(string_);
#endif
Unpark();
return string_;
}
unsigned ParkableStringImpl::CharactersSizeInBytes() const {
AssertOnValidThread();
return string_.CharactersSizeInBytes();
}
bool ParkableStringImpl::Park() {
AssertOnValidThread();
MutexLocker locker(mutex_);
DCHECK(is_parkable_);
if (lock_depth_ != 0)
return false;
// Cannot park strings with several references.
if (string_.Impl()->HasOneRef()) {
#if defined(ADDRESS_SANITIZER)
AsanPoisonString(string_);
#endif
RecordParkingAction(ParkingAction::kParkedInBackground);
is_parked_ = true;
}
return is_parked_;
}
void ParkableStringImpl::Unpark() {
AssertOnValidThread();
mutex_.AssertAcquired();
if (!is_parked_)
return;
bool backgrounded =
ParkableStringManager::Instance().IsRendererBackgrounded();
RecordParkingAction(backgrounded ? ParkingAction::kUnparkedInBackground
: ParkingAction::kUnparkedInForeground);
is_parked_ = false;
}
ParkableString::ParkableString(scoped_refptr<StringImpl>&& impl) {
if (!impl) {
impl_ = nullptr;
return;
}
bool is_parkable = ParkableStringManager::ShouldPark(*impl);
if (is_parkable) {
impl_ = ParkableStringManager::Instance().Add(std::move(impl));
} else {
impl_ = base::MakeRefCounted<ParkableStringImpl>(
std::move(impl), ParkableStringImpl::ParkableState::kNotParkable);
}
}
ParkableString::~ParkableString() = default;
void ParkableString::Lock() const {
if (impl_)
impl_->Lock();
}
void ParkableString::Unlock() const {
if (impl_)
impl_->Unlock();
}
bool ParkableString::Is8Bit() const {
return impl_->Is8Bit();
}
String ParkableString::ToString() const {
return impl_ ? impl_->ToString() : String();
}
unsigned ParkableString::CharactersSizeInBytes() const {
return impl_ ? impl_->CharactersSizeInBytes() : 0;
}
} // namespace blink
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