Futex-inl.h | Explore in Territory

/*
 * 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/synchronization/ParkingLot.h>

namespace folly {
namespace detail {

/** Optimal when TargetClock is the same type as Clock.
 *
 *  Otherwise, both Clock::now() and TargetClock::now() must be invoked. */
template <typename TargetClock, typename Clock, typename Duration>
typename TargetClock::time_point time_point_conv(
    std::chrono::time_point<Clock, Duration> const& time) { … }

/**
 * Available overloads, with definitions elsewhere
 *
 * These functions are treated as ADL-extension points, the templates above
 * call these functions without them having being pre-declared.  This works
 * because ADL lookup finds the definitions of these functions when you pass
 * the relevant arguments
 */
int futexWakeImpl(
    const Futex<std::atomic>* futex, int count, uint32_t wakeMask);
FutexResult futexWaitImpl(
    const Futex<std::atomic>* futex,
    uint32_t expected,
    std::chrono::system_clock::time_point const* absSystemTime,
    std::chrono::steady_clock::time_point const* absSteadyTime,
    uint32_t waitMask);

int futexWakeImpl(
    const Futex<EmulatedFutexAtomic>* futex, int count, uint32_t wakeMask);
FutexResult futexWaitImpl(
    const Futex<EmulatedFutexAtomic>* futex,
    uint32_t expected,
    std::chrono::system_clock::time_point const* absSystemTime,
    std::chrono::steady_clock::time_point const* absSteadyTime,
    uint32_t waitMask);

template <typename Futex, typename Deadline>
typename std::enable_if<Deadline::clock::is_steady, FutexResult>::type
futexWaitImpl(
    Futex* futex,
    uint32_t expected,
    Deadline const& deadline,
    uint32_t waitMask) { … }

template <typename Futex, typename Deadline>
typename std::enable_if<!Deadline::clock::is_steady, FutexResult>::type
futexWaitImpl(
    Futex* futex,
    uint32_t expected,
    Deadline const& deadline,
    uint32_t waitMask) { … }

template <typename Futex>
FutexResult futexWait(
    const Futex* futex, uint32_t expected, uint32_t waitMask) { … }

template <typename Futex>
int futexWake(const Futex* futex, int count, uint32_t wakeMask) { … }

template <typename Futex, class Clock, class Duration>
FutexResult futexWaitUntil(
    const Futex* futex,
    uint32_t expected,
    std::chrono::time_point<Clock, Duration> const& deadline,
    uint32_t waitMask) { … }

} // namespace detail
} // namespace folly
folly/folly/detail/Futex-inl.h
