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- /*
- * Copyright 2015-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- namespace folly {
- namespace detail {
- template <typename T>
- template <typename Tag, typename VaultTag>
- SingletonHolder<T>& SingletonHolder<T>::singleton() {
- /* library-local */ static auto entry =
- createGlobal<SingletonHolder<T>, std::pair<Tag, VaultTag>>([]() {
- return new SingletonHolder<T>(
- {typeid(T), typeid(Tag)}, *SingletonVault::singleton<VaultTag>());
- });
- return *entry;
- }
- [[noreturn]] void singletonWarnDoubleRegistrationAndAbort(
- const TypeDescriptor& type);
- template <typename T>
- void SingletonHolder<T>::registerSingleton(CreateFunc c, TeardownFunc t) {
- std::lock_guard<std::mutex> entry_lock(mutex_);
- if (state_ != SingletonHolderState::NotRegistered) {
- /* 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); });
- *
- */
- singletonWarnDoubleRegistrationAndAbort(type());
- }
- create_ = std::move(c);
- teardown_ = std::move(t);
- state_ = SingletonHolderState::Dead;
- }
- template <typename T>
- void SingletonHolder<T>::registerSingletonMock(CreateFunc c, TeardownFunc t) {
- if (state_ == SingletonHolderState::NotRegistered) {
- detail::singletonWarnRegisterMockEarlyAndAbort(type());
- }
- if (state_ == SingletonHolderState::Living) {
- destroyInstance();
- }
- {
- auto creationOrder = vault_.creationOrder_.wlock();
- auto it = std::find(creationOrder->begin(), creationOrder->end(), type());
- if (it != creationOrder->end()) {
- creationOrder->erase(it);
- }
- }
- std::lock_guard<std::mutex> entry_lock(mutex_);
- create_ = std::move(c);
- teardown_ = std::move(t);
- }
- template <typename T>
- T* SingletonHolder<T>::get() {
- if (LIKELY(
- state_.load(std::memory_order_acquire) ==
- SingletonHolderState::Living)) {
- return instance_ptr_;
- }
- createInstance();
- if (instance_weak_.expired()) {
- detail::singletonThrowGetInvokedAfterDestruction(type());
- }
- return instance_ptr_;
- }
- template <typename T>
- std::weak_ptr<T> SingletonHolder<T>::get_weak() {
- 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>
- void SingletonHolder<T>::vivify() {
- if (UNLIKELY(
- state_.load(std::memory_order_relaxed) !=
- SingletonHolderState::Living)) {
- createInstance();
- }
- }
- template <typename T>
- bool SingletonHolder<T>::hasLiveInstance() {
- return !instance_weak_.expired();
- }
- template <typename T>
- void SingletonHolder<T>::preDestroyInstance(
- ReadMostlyMainPtrDeleter<>& deleter) {
- instance_copy_ = instance_;
- deleter.add(std::move(instance_));
- }
- template <typename T>
- void SingletonHolder<T>::destroyInstance() {
- state_ = SingletonHolderState::Dead;
- instance_.reset();
- instance_copy_.reset();
- if (destroy_baton_) {
- constexpr std::chrono::seconds kDestroyWaitTime{5};
- auto last_reference_released =
- destroy_baton_->try_wait_for(kDestroyWaitTime);
- if (last_reference_released) {
- teardown_(instance_ptr_);
- } else {
- print_destructor_stack_trace_->store(true);
- detail::singletonWarnDestroyInstanceLeak(type(), instance_ptr_);
- }
- }
- }
- template <typename T>
- SingletonHolder<T>::SingletonHolder(
- TypeDescriptor typeDesc,
- SingletonVault& vault)
- : SingletonHolderBase(typeDesc), 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() {
- if (creating_thread_.load(std::memory_order_acquire) ==
- std::this_thread::get_id()) {
- detail::singletonWarnCreateCircularDependencyAndAbort(type());
- }
- std::lock_guard<std::mutex> entry_lock(mutex_);
- if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
- return;
- }
- if (state_.load(std::memory_order_acquire) ==
- SingletonHolderState::NotRegistered) {
- detail::singletonWarnCreateUnregisteredAndAbort(type());
- }
- if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
- return;
- }
- 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);
- auto state = vault_.state_.rlock();
- if (vault_.type_ != SingletonVault::Type::Relaxed &&
- !state->registrationComplete) {
- detail::singletonWarnCreateBeforeRegistrationCompleteAndAbort(type());
- }
- if (state->state == detail::SingletonVaultState::Type::Quiescing) {
- return;
- }
- auto destroy_baton = std::make_shared<folly::Baton<>>();
- auto print_destructor_stack_trace =
- std::make_shared<std::atomic<bool>>(false);
- // Can't use make_shared -- no support for a custom deleter, sadly.
- std::shared_ptr<T> instance(
- create_(),
- [destroy_baton, print_destructor_stack_trace, type = type()](T*) mutable {
- destroy_baton->post();
- if (print_destructor_stack_trace->load()) {
- detail::singletonPrintDestructionStackTrace(type);
- }
- });
- // We should schedule destroyInstances() only after the singleton was
- // created. This will ensure it will be destroyed before singletons,
- // not managed by folly::Singleton, which were initialized in its
- // constructor
- SingletonVault::scheduleDestroyInstances();
- 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, std::memory_order_release);
- vault_.creationOrder_.wlock()->push_back(type());
- }
- } // namespace detail
- } // namespace folly
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