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Address potential Persistent Settings Getters race.
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While Getters and SetterHelpers both use locks to prevent race
conditions, Setters do not. Given that Setters run SetterHelpers through
posted tasks, it is possible for Getters to run in-between Setters and
SetterHelpers causing a race condition. To resolve this, effectively add
Getters into the Post Task Queue by calling WaitForFence. Also refactor
GetValues calls so that they are run by Setters rather than Getters to
limit the number of deep copies made.

Now that Getters and Setters no longer race, massively clean up the
tests by removing the unwieldly and now unneeded closures.

b/305057554
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@briantting
briantting committed Apr 27, 2024
1 parent 00c3930 commit 9a84c56
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Showing 3 changed files with 221 additions and 506 deletions.
111 changes: 61 additions & 50 deletions cobalt/persistent_storage/persistent_settings.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,7 @@ void PersistentSettings::InitializePrefStore() {
pref_store_ = base::MakeRefCounted<JsonPrefStore>(
base::FilePath(persistent_settings_file_));
pref_store_->ReadPrefs();
persistent_settings_ = pref_store_->GetValues();
pref_store_initialized_.Signal();
}
// Remove settings file and do not allow writes to the file until the
Expand All @@ -102,42 +103,47 @@ void PersistentSettings::ValidatePersistentSettingsHelper(bool blocking) {

bool PersistentSettings::GetPersistentSettingAsBool(const std::string& key,
bool default_setting) {
// Wait for all previously posted tasks to finish.
PostBlockingTask();
base::AutoLock auto_lock(pref_store_lock_);
auto persistent_settings = pref_store_->GetValues();
absl::optional<bool> result = persistent_settings.FindBool(key);
absl::optional<bool> result = persistent_settings_.FindBool(key);
return result.value_or(default_setting);
}

int PersistentSettings::GetPersistentSettingAsInt(const std::string& key,
int default_setting) {
// Wait for all previously posted tasks to finish.
PostBlockingTask();
base::AutoLock auto_lock(pref_store_lock_);
auto persistent_settings = pref_store_->GetValues();
absl::optional<int> result = persistent_settings.FindInt(key);
absl::optional<int> result = persistent_settings_.FindInt(key);
return result.value_or(default_setting);
}

double PersistentSettings::GetPersistentSettingAsDouble(
const std::string& key, double default_setting) {
// Wait for all previously posted tasks to finish.
PostBlockingTask();
base::AutoLock auto_lock(pref_store_lock_);
auto persistent_settings = pref_store_->GetValues();
absl::optional<double> result = persistent_settings.FindDouble(key);
absl::optional<double> result = persistent_settings_.FindDouble(key);
return result.value_or(default_setting);
}

std::string PersistentSettings::GetPersistentSettingAsString(
const std::string& key, const std::string& default_setting) {
// Wait for all previously posted tasks to finish.
PostBlockingTask();
base::AutoLock auto_lock(pref_store_lock_);
auto persistent_settings = pref_store_->GetValues();
const std::string* result = persistent_settings.FindString(key);
const std::string* result = persistent_settings_.FindString(key);
if (result) return *result;
return default_setting;
}

std::vector<base::Value> PersistentSettings::GetPersistentSettingAsList(
const std::string& key) {
// Wait for all previously posted tasks to finish.
PostBlockingTask();
base::AutoLock auto_lock(pref_store_lock_);
auto persistent_settings = pref_store_->GetValues();
const base::Value::List* result = persistent_settings.FindList(key);
const base::Value::List* result = persistent_settings_.FindList(key);
std::vector<base::Value> values;
if (result) {
for (const auto& value : *result) {
Expand All @@ -149,9 +155,10 @@ std::vector<base::Value> PersistentSettings::GetPersistentSettingAsList(

base::flat_map<std::string, std::unique_ptr<base::Value>>
PersistentSettings::GetPersistentSettingAsDictionary(const std::string& key) {
// Wait for all previously posted tasks to finish.
PostBlockingTask();
base::AutoLock auto_lock(pref_store_lock_);
auto persistent_settings = pref_store_->GetValues();
base::Value::Dict* result = persistent_settings.FindDict(key);
base::Value::Dict* result = persistent_settings_.FindDict(key);
base::flat_map<std::string, std::unique_ptr<base::Value>> dict;
if (result) {
for (base::Value::Dict::iterator it = result->begin(); it != result->end();
Expand All @@ -164,70 +171,74 @@ PersistentSettings::GetPersistentSettingAsDictionary(const std::string& key) {
return dict;
}

void PersistentSettings::PostBlockingTask() {
base::WaitableEvent task_finished(
base::WaitableEvent::ResetPolicy::MANUAL,
base::WaitableEvent::InitialState::NOT_SIGNALED);
task_runner()->PostTask(
FROM_HERE, base::BindOnce(&PersistentSettings::PostBlockingTaskHelper,
base::Unretained(this), &task_finished));
task_finished.Wait();
}

void PersistentSettings::PostBlockingTaskHelper(
base::WaitableEvent* task_finished) {
DCHECK_EQ(base::SequencedTaskRunner::GetCurrentDefault(), task_runner());
task_finished->Signal();
}

void PersistentSettings::SetPersistentSetting(
const std::string& key, std::unique_ptr<base::Value> value,
base::OnceClosure closure, bool blocking) {
const std::string& key, std::unique_ptr<base::Value> value, bool blocking) {
task_runner()->PostTask(
FROM_HERE, base::BindOnce(&PersistentSettings::SetPersistentSettingHelper,
base::Unretained(this), key, std::move(value),
std::move(closure), blocking));
FROM_HERE,
base::BindOnce(&PersistentSettings::SetPersistentSettingHelper,
base::Unretained(this), key, std::move(value), blocking));
}

void PersistentSettings::SetPersistentSettingHelper(
const std::string& key, std::unique_ptr<base::Value> value,
base::OnceClosure closure, bool blocking) {
const std::string& key, std::unique_ptr<base::Value> value, bool blocking) {
DCHECK_EQ(base::SequencedTaskRunner::GetCurrentDefault(), task_runner());
{
base::AutoLock auto_lock(pref_store_lock_);
pref_store_->SetValue(key,
base::Value::FromUniquePtrValue(std::move(value)),
WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
if (validated_initial_settings_) {
CommitPendingWrite(blocking);
}
base::AutoLock auto_lock(pref_store_lock_);
pref_store_->SetValue(key, base::Value::FromUniquePtrValue(std::move(value)),
WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
persistent_settings_ = pref_store_->GetValues();
if (validated_initial_settings_) {
CommitPendingWrite(blocking);
}
std::move(closure).Run();
}

void PersistentSettings::RemovePersistentSetting(const std::string& key,
base::OnceClosure closure,
bool blocking) {
task_runner()->PostTask(
FROM_HERE,
base::BindOnce(&PersistentSettings::RemovePersistentSettingHelper,
base::Unretained(this), key, std::move(closure),
blocking));
base::Unretained(this), key, blocking));
}

void PersistentSettings::RemovePersistentSettingHelper(
const std::string& key, base::OnceClosure closure, bool blocking) {
void PersistentSettings::RemovePersistentSettingHelper(const std::string& key,
bool blocking) {
DCHECK_EQ(base::SequencedTaskRunner::GetCurrentDefault(), task_runner());
{
base::AutoLock auto_lock(pref_store_lock_);
pref_store_->RemoveValue(key, WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
if (validated_initial_settings_) {
CommitPendingWrite(blocking);
}
base::AutoLock auto_lock(pref_store_lock_);
pref_store_->RemoveValue(key, WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
persistent_settings_ = pref_store_->GetValues();
if (validated_initial_settings_) {
CommitPendingWrite(blocking);
}
std::move(closure).Run();
}

void PersistentSettings::DeletePersistentSettings(base::OnceClosure closure) {
void PersistentSettings::DeletePersistentSettings() {
task_runner()->PostTask(
FROM_HERE,
base::BindOnce(&PersistentSettings::DeletePersistentSettingsHelper,
base::Unretained(this), std::move(closure)));
base::Unretained(this)));
}

void PersistentSettings::DeletePersistentSettingsHelper(
base::OnceClosure closure) {
void PersistentSettings::DeletePersistentSettingsHelper() {
DCHECK_EQ(base::SequencedTaskRunner::GetCurrentDefault(), task_runner());
{
base::AutoLock auto_lock(pref_store_lock_);
starboard::SbFileDeleteRecursive(persistent_settings_file_.c_str(), true);
pref_store_->ReadPrefs();
}
std::move(closure).Run();
base::AutoLock auto_lock(pref_store_lock_);
starboard::SbFileDeleteRecursive(persistent_settings_file_.c_str(), true);
pref_store_->ReadPrefs();
persistent_settings_ = pref_store_->GetValues();
}

void PersistentSettings::CommitPendingWrite(bool blocking) {
Expand Down
35 changes: 18 additions & 17 deletions cobalt/persistent_storage/persistent_settings.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,18 +72,13 @@ class PersistentSettings : public base::CurrentThread::DestructionObserver {
base::flat_map<std::string, std::unique_ptr<base::Value>>
GetPersistentSettingAsDictionary(const std::string& key);

void SetPersistentSetting(
const std::string& key, std::unique_ptr<base::Value> value,
base::OnceClosure closure = std::move(base::DoNothing()),
bool blocking = false);
void SetPersistentSetting(const std::string& key,
std::unique_ptr<base::Value> value,
bool blocking = false);

void RemovePersistentSetting(
const std::string& key,
base::OnceClosure closure = std::move(base::DoNothing()),
bool blocking = false);
void RemovePersistentSetting(const std::string& key, bool blocking = false);

void DeletePersistentSettings(
base::OnceClosure closure = std::move(base::DoNothing()));
void DeletePersistentSettings();

private:
// Called by the constructor to initialize pref_store_ from
Expand All @@ -92,14 +87,17 @@ class PersistentSettings : public base::CurrentThread::DestructionObserver {

void ValidatePersistentSettingsHelper(bool blocking);

void PostBlockingTask();

void PostBlockingTaskHelper(base::WaitableEvent* task_finished);

void SetPersistentSettingHelper(const std::string& key,
std::unique_ptr<base::Value> value,
base::OnceClosure closure, bool blocking);
bool blocking);

void RemovePersistentSettingHelper(const std::string& key,
base::OnceClosure closure, bool blocking);
void RemovePersistentSettingHelper(const std::string& key, bool blocking);

void DeletePersistentSettingsHelper(base::OnceClosure closure);
void DeletePersistentSettingsHelper();

void CommitPendingWrite(bool blocking);

Expand All @@ -109,14 +107,17 @@ class PersistentSettings : public base::CurrentThread::DestructionObserver {
// PrefStore used for persistent settings.
scoped_refptr<PersistentPrefStore> pref_store_;

// Flag indicating whether or not initial persistent settings have been
// validated.
bool validated_initial_settings_;
// Persistent settings dictionary.
base::Value::Dict persistent_settings_;

// The thread created and owned by PersistentSettings. All pref_store_
// methods must be called from this thread.
base::Thread thread_;

// Flag indicating whether or not initial persistent settings have been
// validated.
bool validated_initial_settings_;

// This event is used to signal when Initialize has been called and
// pref_store_ mutations can now occur.
base::WaitableEvent pref_store_initialized_ = {
Expand Down
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