folly/folly/synchronization/AtomicNotification-inl.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * 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/detail/Futex.h>
#include <folly/synchronization/ParkingLot.h>

namespace folly {
namespace detail {
namespace atomic_notification {
/**
 * We use Futex<std::atomic> as the alias that has the lowest performance
 * overhead with respect to atomic notifications.  Assert that
 * atomic_uint_fast_wait_t is the same as Futex<std::atomic>
 */
static_assert …;

/**
 * Implementation and specializations for the atomic_wait() family of
 * functions
 */
inline std::cv_status toCvStatus(FutexResult result) { … }
inline std::cv_status toCvStatus(ParkResult result) { … }

// ParkingLot instantiation for futex management
extern ParkingLot<std::uint32_t> parkingLot;

template <template <typename...> class Atom, typename... Args>
void atomic_wait_impl(
    const Atom<std::uint32_t, Args...>* atomic, std::uint32_t old) { … }

template <template <typename...> class Atom, typename Integer, typename... Args>
void atomic_wait_impl(const Atom<Integer, Args...>* atomic, Integer old) { … }

template <
    template <typename...>
    class Atom,
    typename... Args,
    typename Clock,
    typename Duration>
std::cv_status atomic_wait_until_impl(
    const Atom<std::uint32_t, Args...>* atomic,
    std::uint32_t expected,
    const std::chrono::time_point<Clock, Duration>& deadline) { … }

template <
    template <typename...>
    class Atom,
    typename Integer,
    typename... Args,
    typename Clock,
    typename Duration>
std::cv_status atomic_wait_until_impl(
    const Atom<Integer, Args...>* atomic,
    Integer expected,
    const std::chrono::time_point<Clock, Duration>& deadline) { … }

template <template <typename...> class Atom, typename... Args>
void atomic_notify_one_impl(const Atom<std::uint32_t, Args...>* atomic) { … }

template <template <typename...> class Atom, typename Integer, typename... Args>
void atomic_notify_one_impl(const Atom<Integer, Args...>* atomic) { … }

template <template <typename...> class Atom, typename... Args>
void atomic_notify_all_impl(const Atom<std::uint32_t, Args...>* atomic) { … }

template <template <typename...> class Atom, typename Integer, typename... Args>
void atomic_notify_all_impl(const Atom<Integer, Args...>* atomic) { … }

template <typename Integer>
void tag_invoke(
    atomic_wait_fn, const std::atomic<Integer>* atomic, Integer expected) { … }

template <typename Integer, typename Clock, typename Duration>
std::cv_status tag_invoke(
    atomic_wait_until_fn,
    const std::atomic<Integer>* atomic,
    Integer expected,
    const std::chrono::time_point<Clock, Duration>& deadline) { … }

template <typename Integer>
void tag_invoke(atomic_notify_one_fn, const std::atomic<Integer>* atomic) { … }

template <typename Integer>
void tag_invoke(atomic_notify_all_fn, const std::atomic<Integer>* atomic) { … }
} // namespace atomic_notification
} // namespace detail
} // namespace folly