libcruft-util/job/spinlock.cpp

58 lines
1.4 KiB
C++

/*
* 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::job::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;
}