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shared_spinlock.cpp
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shared_spinlock.cpp
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/******************************************************************************\
* ___ __ *
* /\_ \ __/\ \ *
* \//\ \ /\_\ \ \____ ___ _____ _____ __ *
* \ \ \ \/\ \ \ '__`\ /'___\/\ '__`\/\ '__`\ /'__`\ *
* \_\ \_\ \ \ \ \L\ \/\ \__/\ \ \L\ \ \ \L\ \/\ \L\.\_ *
* /\____\\ \_\ \_,__/\ \____\\ \ ,__/\ \ ,__/\ \__/.\_\ *
* \/____/ \/_/\/___/ \/____/ \ \ \/ \ \ \/ \/__/\/_/ *
* \ \_\ \ \_\ *
* \/_/ \/_/ *
* *
* Copyright (C) 2011, 2012 *
* Dominik Charousset <dominik.charousset@haw-hamburg.de> *
* *
* This file is part of libcppa. *
* libcppa is free software: you can redistribute it and/or modify it under *
* the terms of the GNU Lesser General Public License as published by the *
* Free Software Foundation, either version 3 of the License *
* or (at your option) any later version. *
* *
* libcppa is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. *
* See the GNU Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public License *
* along with libcppa. If not, see <http://www.gnu.org/licenses/>. *
\******************************************************************************/
#include "cppa/config.hpp"
#include <limits>
#include <thread>
#include "cppa/util/shared_spinlock.hpp"
namespace {
inline long min_long() { return std::numeric_limits<long>::min(); }
} // namespace <anonymous>
namespace cppa { namespace util {
shared_spinlock::shared_spinlock() : m_flag(0) {
}
void shared_spinlock::lock() {
long v = m_flag.load();
for (;;) {
if (v != 0) {
//std::this_thread::yield();
v = m_flag.load();
}
else if (m_flag.compare_exchange_weak(v, min_long())) {
return;
}
// else: next iteration
}
}
void shared_spinlock::lock_upgrade() {
unlock_shared();
lock();
}
void shared_spinlock::unlock() {
m_flag.store(0);
}
bool shared_spinlock::try_lock() {
long v = m_flag.load();
return (v == 0) ? m_flag.compare_exchange_weak(v, min_long()) : false;
}
void shared_spinlock::lock_shared() {
long v = m_flag.load();
for (;;) {
if (v < 0) {
//std::this_thread::yield();
v = m_flag.load();
}
else if (m_flag.compare_exchange_weak(v, v + 1)) {
return;
}
// else: next iteration
}
}
void shared_spinlock::unlock_shared() {
m_flag.fetch_sub(1);
}
bool shared_spinlock::try_lock_shared() {
long v = m_flag.load();
return (v >= 0) ? m_flag.compare_exchange_weak(v, v + 1) : false;
}
} } // namespace cppa::util