1/* 2 * Copyright (C) 2013 Apple Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR 17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26#ifndef ByteSpinLock_h 27#define ByteSpinLock_h 28 29#include <thread> 30#include <wtf/Assertions.h> 31#include <wtf/Atomics.h> 32#include <wtf/Locker.h> 33#include <wtf/Noncopyable.h> 34 35namespace WTF { 36 37class ByteSpinLock { 38 WTF_MAKE_NONCOPYABLE(ByteSpinLock); 39public: 40 ByteSpinLock() 41 : m_lock(0) 42 { 43 } 44 45 void lock() 46 { 47 while (!weakCompareAndSwap(&m_lock, 0, 1)) 48 std::this_thread::yield(); 49 memoryBarrierAfterLock(); 50 } 51 52 void unlock() 53 { 54 memoryBarrierBeforeUnlock(); 55 m_lock = 0; 56 } 57 58 bool isHeld() const { return !!m_lock; } 59 60private: 61 uint8_t m_lock; 62}; 63 64typedef Locker<ByteSpinLock> ByteSpinLocker; 65 66} // namespace WTF 67 68using WTF::ByteSpinLock; 69using WTF::ByteSpinLocker; 70 71#endif // ByteSpinLock_h 72