276 lines
8.0 KiB
C++
276 lines
8.0 KiB
C++
/*
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* Copyright 2015-present Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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namespace folly {
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namespace detail {
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template <typename T>
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template <typename Tag, typename VaultTag>
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SingletonHolder<T>& SingletonHolder<T>::singleton() {
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/* library-local */ static auto entry =
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createGlobal<SingletonHolder<T>, std::pair<Tag, VaultTag>>([]() {
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return new SingletonHolder<T>(
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{typeid(T), typeid(Tag)}, *SingletonVault::singleton<VaultTag>());
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});
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return *entry;
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}
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[[noreturn]] void singletonWarnDoubleRegistrationAndAbort(
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const TypeDescriptor& type);
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template <typename T>
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void SingletonHolder<T>::registerSingleton(CreateFunc c, TeardownFunc t) {
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std::lock_guard<std::mutex> entry_lock(mutex_);
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if (state_ != SingletonHolderState::NotRegistered) {
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/* Possible causes:
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*
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* You have two instances of the same
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* folly::Singleton<Class>. Probably because you define the
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* singleton in a header included in multiple places? In general,
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* folly::Singleton shouldn't be in the header, only off in some
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* anonymous namespace in a cpp file. Code needing the singleton
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* will find it when that code references folly::Singleton<Class>.
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*
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* Alternatively, you could have 2 singletons with the same type
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* defined with a different name in a .cpp (source) file. For
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* example:
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*
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* Singleton<int> a([] { return new int(3); });
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* Singleton<int> b([] { return new int(4); });
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*
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*/
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singletonWarnDoubleRegistrationAndAbort(type());
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}
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create_ = std::move(c);
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teardown_ = std::move(t);
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state_ = SingletonHolderState::Dead;
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}
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template <typename T>
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void SingletonHolder<T>::registerSingletonMock(CreateFunc c, TeardownFunc t) {
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if (state_ == SingletonHolderState::NotRegistered) {
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detail::singletonWarnRegisterMockEarlyAndAbort(type());
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}
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if (state_ == SingletonHolderState::Living) {
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destroyInstance();
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}
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{
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auto creationOrder = vault_.creationOrder_.wlock();
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auto it = std::find(creationOrder->begin(), creationOrder->end(), type());
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if (it != creationOrder->end()) {
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creationOrder->erase(it);
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}
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}
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std::lock_guard<std::mutex> entry_lock(mutex_);
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create_ = std::move(c);
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teardown_ = std::move(t);
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}
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template <typename T>
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T* SingletonHolder<T>::get() {
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if (LIKELY(
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state_.load(std::memory_order_acquire) ==
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SingletonHolderState::Living)) {
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return instance_ptr_;
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}
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createInstance();
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if (instance_weak_.expired()) {
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detail::singletonThrowGetInvokedAfterDestruction(type());
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}
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return instance_ptr_;
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}
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template <typename T>
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std::weak_ptr<T> SingletonHolder<T>::get_weak() {
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if (UNLIKELY(
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state_.load(std::memory_order_acquire) !=
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SingletonHolderState::Living)) {
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createInstance();
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}
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return instance_weak_;
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}
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template <typename T>
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std::shared_ptr<T> SingletonHolder<T>::try_get() {
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if (UNLIKELY(
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state_.load(std::memory_order_acquire) !=
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SingletonHolderState::Living)) {
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createInstance();
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}
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return instance_weak_.lock();
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}
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template <typename T>
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folly::ReadMostlySharedPtr<T> SingletonHolder<T>::try_get_fast() {
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if (UNLIKELY(
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state_.load(std::memory_order_acquire) !=
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SingletonHolderState::Living)) {
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createInstance();
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}
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return instance_weak_fast_.lock();
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}
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template <typename T>
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void SingletonHolder<T>::vivify() {
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if (UNLIKELY(
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state_.load(std::memory_order_relaxed) !=
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SingletonHolderState::Living)) {
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createInstance();
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}
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}
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template <typename T>
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bool SingletonHolder<T>::hasLiveInstance() {
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return !instance_weak_.expired();
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}
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template <typename T>
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void SingletonHolder<T>::preDestroyInstance(
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ReadMostlyMainPtrDeleter<>& deleter) {
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instance_copy_ = instance_;
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deleter.add(std::move(instance_));
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}
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template <typename T>
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void SingletonHolder<T>::destroyInstance() {
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state_ = SingletonHolderState::Dead;
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instance_.reset();
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instance_copy_.reset();
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if (destroy_baton_) {
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constexpr std::chrono::seconds kDestroyWaitTime{5};
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auto last_reference_released =
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destroy_baton_->try_wait_for(kDestroyWaitTime);
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if (last_reference_released) {
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teardown_(instance_ptr_);
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} else {
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print_destructor_stack_trace_->store(true);
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detail::singletonWarnDestroyInstanceLeak(type(), instance_ptr_);
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}
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}
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}
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template <typename T>
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SingletonHolder<T>::SingletonHolder(
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TypeDescriptor typeDesc,
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SingletonVault& vault)
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: SingletonHolderBase(typeDesc), vault_(vault) {}
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template <typename T>
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bool SingletonHolder<T>::creationStarted() {
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// If alive, then creation was of course started.
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// This is flipped after creating_thread_ was set, and before it was reset.
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if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
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return true;
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}
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// Not yet built. Is it currently in progress?
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if (creating_thread_.load(std::memory_order_acquire) != std::thread::id()) {
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return true;
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}
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return false;
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}
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template <typename T>
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void SingletonHolder<T>::createInstance() {
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if (creating_thread_.load(std::memory_order_acquire) ==
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std::this_thread::get_id()) {
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detail::singletonWarnCreateCircularDependencyAndAbort(type());
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}
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std::lock_guard<std::mutex> entry_lock(mutex_);
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if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
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return;
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}
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if (state_.load(std::memory_order_acquire) ==
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SingletonHolderState::NotRegistered) {
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detail::singletonWarnCreateUnregisteredAndAbort(type());
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}
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if (state_.load(std::memory_order_acquire) == SingletonHolderState::Living) {
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return;
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}
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SCOPE_EXIT {
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// Clean up creator thread when complete, and also, in case of errors here,
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// so that subsequent attempts don't think this is still in the process of
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// being built.
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creating_thread_.store(std::thread::id(), std::memory_order_release);
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};
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creating_thread_.store(std::this_thread::get_id(), std::memory_order_release);
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auto state = vault_.state_.rlock();
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if (vault_.type_ != SingletonVault::Type::Relaxed &&
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!state->registrationComplete) {
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detail::singletonWarnCreateBeforeRegistrationCompleteAndAbort(type());
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}
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if (state->state == detail::SingletonVaultState::Type::Quiescing) {
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return;
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}
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auto destroy_baton = std::make_shared<folly::Baton<>>();
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auto print_destructor_stack_trace =
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std::make_shared<std::atomic<bool>>(false);
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// Can't use make_shared -- no support for a custom deleter, sadly.
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std::shared_ptr<T> instance(
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create_(),
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[destroy_baton, print_destructor_stack_trace, type = type()](T*) mutable {
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destroy_baton->post();
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if (print_destructor_stack_trace->load()) {
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detail::singletonPrintDestructionStackTrace(type);
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}
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});
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// We should schedule destroyInstances() only after the singleton was
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// created. This will ensure it will be destroyed before singletons,
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// not managed by folly::Singleton, which were initialized in its
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// constructor
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SingletonVault::scheduleDestroyInstances();
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instance_weak_ = instance;
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instance_ptr_ = instance.get();
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instance_.reset(std::move(instance));
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instance_weak_fast_ = instance_;
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destroy_baton_ = std::move(destroy_baton);
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print_destructor_stack_trace_ = std::move(print_destructor_stack_trace);
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// This has to be the last step, because once state is Living other threads
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// may access instance and instance_weak w/o synchronization.
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state_.store(SingletonHolderState::Living, std::memory_order_release);
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vault_.creationOrder_.wlock()->push_back(type());
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}
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} // namespace detail
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} // namespace folly
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