/*
 * 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.
 *
 * Copyright 2018 Danny Robson <danny@nerdcruft.net>
 */

#include "spinlock.hpp"

#include "../debug.hpp"

using util::thread::spinlock;


///////////////////////////////////////////////////////////////////////////////
spinlock::spinlock ():
    held (false)
{ ; }


//-----------------------------------------------------------------------------
spinlock::spinlock (spinlock &&rhs):
    held (rhs.held.load ())
{ ; }


///////////////////////////////////////////////////////////////////////////////
void
spinlock::lock (void)
{
    do {
        bool expected = false;
        if (held.compare_exchange_weak (expected, true))
            return;

        while (held)
            __asm__ volatile ("pause");
    } while (true);
}


//-----------------------------------------------------------------------------
void
spinlock::unlock (void)
{
    CHECK (held);
    held = false;
}