/* * Copyright (C) 2015 Apple Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #ifndef SpinLock_h #define SpinLock_h #include <thread> #include <wtf/Atomics.h> #include <wtf/Locker.h> namespace WTF { // SpinLockBase is a struct without an explicitly defined constructors so that // it can be initialized at compile time. See StaticSpinLock below. struct SpinLockBase { void lock() { while (!m_lock.compareExchangeWeak(0, 1, std::memory_order_acquire)) std::this_thread::yield(); } void unlock() { m_lock.store(0, std::memory_order_release); } bool isLocked() const { return m_lock.load(std::memory_order_acquire); } Atomic<unsigned> m_lock; }; // SpinLock is for use as instance variables in structs and classes, not as // statics and globals. struct SpinLock : public SpinLockBase { SpinLock() { m_lock.store(0, std::memory_order_relaxed); } }; // StaticSpinLock is for use as statics and globals, not as instance variables. typedef SpinLockBase StaticSpinLock; typedef Locker<SpinLockBase> SpinLockHolder; } // namespace WTF using WTF::StaticSpinLock; using WTF::SpinLock; using WTF::SpinLockHolder; #endif // SpinLock_h