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- /*
- * Copyright 2018-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.
- */
- #pragma once
- #include <folly/synchronization/Hazptr-fwd.h>
- #include <folly/concurrency/CacheLocality.h>
- #include <atomic>
- namespace folly {
- /**
- * hazptr_rec:
- *
- * Contains the actual hazard pointer.
- */
- template <template <typename> class Atom>
- class alignas(hardware_destructive_interference_size) hazptr_rec {
- Atom<const void*> hazptr_{nullptr}; // the hazard pointer
- hazptr_domain<Atom>* domain_;
- hazptr_rec* next_;
- Atom<bool> active_{false};
- friend class hazptr_domain<Atom>;
- friend class hazptr_holder<Atom>;
- friend class hazptr_tc_entry<Atom>;
- const void* hazptr() const noexcept {
- return hazptr_.load(std::memory_order_acquire);
- }
- FOLLY_ALWAYS_INLINE void reset_hazptr(const void* p = nullptr) noexcept {
- hazptr_.store(p, std::memory_order_release);
- }
- bool active() const noexcept {
- return active_.load(std::memory_order_acquire);
- }
- void set_active() noexcept {
- active_.store(true, std::memory_order_relaxed);
- }
- bool try_acquire() noexcept {
- bool a = active();
- return !a &&
- active_.compare_exchange_strong(
- a, true, std::memory_order_release, std::memory_order_relaxed);
- }
- void release() noexcept {
- active_.store(false, std::memory_order_release);
- }
- hazptr_rec<Atom>* next() {
- return next_;
- }
- void set_next(hazptr_rec<Atom>* rec) {
- next_ = rec;
- }
- FOLLY_ALWAYS_INLINE hazptr_domain<Atom>* domain() {
- return domain_;
- }
- void set_domain(hazptr_domain<Atom>* dom) {
- domain_ = dom;
- }
- }; // hazptr_rec
- } // namespace folly
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