std::lock_guard<std::mutex> entry_lock(mutex_);
if (state_ != SingletonHolderState::NotRegistered) {
- throw std::logic_error("Double registration");
+ /* Possible causes:
+ *
+ * You have two instances of the same
+ * folly::Singleton<Class>. Probably because you define the
+ * singleton in a header included in multiple places? In general,
+ * folly::Singleton shouldn't be in the header, only off in some
+ * anonymous namespace in a cpp file. Code needing the singleton
+ * will find it when that code references folly::Singleton<Class>.
+ *
+ * Alternatively, you could have 2 singletons with the same type
+ * defined with a different name in a .cpp (source) file. For
+ * example:
+ *
+ * Singleton<int> a([] { return new int(3); });
+ * Singleton<int> b([] { return new int(4); });
+ *
+ */
+ LOG(FATAL) << "Double registration of singletons of the same "
+ << "underlying type; check for multiple definitions "
+ << "of type folly::Singleton<" + type_.name() + ">";
}
create_ = std::move(c);
template <typename T>
void SingletonHolder<T>::registerSingletonMock(CreateFunc c, TeardownFunc t) {
if (state_ == SingletonHolderState::NotRegistered) {
- throw std::logic_error("Registering mock before singleton was registered");
+ LOG(FATAL)
+ << "Registering mock before singleton was registered: " << type_.name();
}
destroyInstance();
template <typename T>
T* SingletonHolder<T>::get() {
- if (LIKELY(state_ == SingletonHolderState::Living)) {
+ if (LIKELY(state_.load(std::memory_order_acquire) ==
+ SingletonHolderState::Living)) {
return instance_ptr_;
}
createInstance();
if (instance_weak_.expired()) {
throw std::runtime_error(
- "Raw pointer to a singleton requested after its destruction.");
+ "Raw pointer to a singleton requested after its destruction."
+ " Singleton type is: " +
+ type_.name());
}
return instance_ptr_;
template <typename T>
std::weak_ptr<T> SingletonHolder<T>::get_weak() {
- if (UNLIKELY(state_ != SingletonHolderState::Living)) {
+ if (UNLIKELY(state_.load(std::memory_order_acquire) !=
+ SingletonHolderState::Living)) {
createInstance();
}
return instance_weak_;
}
+template <typename T>
+std::shared_ptr<T> SingletonHolder<T>::try_get() {
+ if (UNLIKELY(state_.load(std::memory_order_acquire) !=
+ SingletonHolderState::Living)) {
+ createInstance();
+ }
+
+ return instance_weak_.lock();
+}
+
+template <typename T>
+folly::ReadMostlySharedPtr<T> SingletonHolder<T>::try_get_fast() {
+ if (UNLIKELY(state_.load(std::memory_order_acquire) !=
+ SingletonHolderState::Living)) {
+ createInstance();
+ }
+
+ return instance_weak_fast_.lock();
+}
+
template <typename T>
TypeDescriptor SingletonHolder<T>::type() {
return type_;
type_(type__), vault_(vault) {
}
+template <typename T>
+bool SingletonHolder<T>::creationStarted() {
+ // If alive, then creation was of course started.
+ // This is flipped after creating_thread_ was set, and before it was reset.
+ if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
+ return true;
+ }
+
+ // Not yet built. Is it currently in progress?
+ if (creating_thread_.load(std::memory_order_acquire) != std::thread::id()) {
+ return true;
+ }
+
+ return false;
+}
+
template <typename T>
void SingletonHolder<T>::createInstance() {
- // There's no synchronization here, so we may not see the current value
- // for creating_thread if it was set by other thread, but we only care about
- // it if it was set by current thread anyways.
- if (creating_thread_ == std::this_thread::get_id()) {
- throw std::out_of_range(std::string("circular singleton dependency: ") +
- type_.name());
+ if (creating_thread_.load(std::memory_order_acquire) ==
+ std::this_thread::get_id()) {
+ LOG(FATAL) << "circular singleton dependency: " << type_.name();
}
std::lock_guard<std::mutex> entry_lock(mutex_);
- if (state_ == SingletonHolderState::Living) {
+ if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
return;
}
- if (state_ == SingletonHolderState::NotRegistered) {
- throw std::out_of_range("Creating instance for unregistered singleton");
+ if (state_.load(std::memory_order_acquire) ==
+ SingletonHolderState::NotRegistered) {
+ auto ptr = SingletonVault::stackTraceGetter().load();
+ LOG(FATAL) << "Creating instance for unregistered singleton: "
+ << type_.name() << "\n"
+ << "Stacktrace:"
+ << "\n" << (ptr ? (*ptr)() : "(not available)");
}
- if (state_ == SingletonHolderState::Living) {
+ if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
return;
}
- creating_thread_ = std::this_thread::get_id();
+ SCOPE_EXIT {
+ // Clean up creator thread when complete, and also, in case of errors here,
+ // so that subsequent attempts don't think this is still in the process of
+ // being built.
+ creating_thread_.store(std::thread::id(), std::memory_order_release);
+ };
+
+ creating_thread_.store(std::this_thread::get_id(), std::memory_order_release);
RWSpinLock::ReadHolder rh(&vault_.stateMutex_);
if (vault_.state_ == SingletonVault::SingletonVaultState::Quiescing) {
- creating_thread_ = std::thread::id();
return;
}
auto type_name = type_.name();
// Can't use make_shared -- no support for a custom deleter, sadly.
- instance_ = std::shared_ptr<T>(
+ std::shared_ptr<T> instance(
create_(),
[destroy_baton, print_destructor_stack_trace, teardown, type_name]
(T* instance_ptr) mutable {
// constructor
SingletonVault::scheduleDestroyInstances();
- instance_weak_ = instance_;
- instance_ptr_ = instance_.get();
- creating_thread_ = std::thread::id();
+ instance_weak_ = instance;
+ instance_ptr_ = instance.get();
+ instance_.reset(std::move(instance));
+ instance_weak_fast_ = instance_;
+
destroy_baton_ = std::move(destroy_baton);
print_destructor_stack_trace_ = std::move(print_destructor_stack_trace);
// This has to be the last step, because once state is Living other threads
// may access instance and instance_weak w/o synchronization.
- state_.store(SingletonHolderState::Living);
+ state_.store(SingletonHolderState::Living, std::memory_order_release);
{
RWSpinLock::WriteHolder wh(&vault_.mutex_);
projects / folly.git / blobdiff