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ByteSpinLock.h
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71 lines (59 loc) · 2.07 KB
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/*
* Copyright (C) 2013 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 ByteSpinLock_h
#define ByteSpinLock_h
#include <thread>
#include <wtf/Assertions.h>
#include <wtf/Atomics.h>
#include <wtf/Locker.h>
#include <wtf/Noncopyable.h>
namespace WTF {
class ByteSpinLock {
WTF_MAKE_NONCOPYABLE(ByteSpinLock);
public:
ByteSpinLock()
: m_lock(0)
{
}
void lock()
{
while (!weakCompareAndSwap(&m_lock, 0, 1))
std::this_thread::yield();
memoryBarrierAfterLock();
}
void unlock()
{
memoryBarrierBeforeUnlock();
m_lock = 0;
}
bool isHeld() const { return !!m_lock; }
private:
uint8_t m_lock;
};
typedef Locker<ByteSpinLock> ByteSpinLocker;
} // namespace WTF
using WTF::ByteSpinLock;
using WTF::ByteSpinLocker;
#endif // ByteSpinLock_h