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