spin_lock.h

// -*- mode: c++; tab-width: 4; indent-tabs-mode: t; eval: (progn (c-set-style "stroustrup") (c-set-offset 'innamespace 0)); -*-
// vi:set ts=4 sts=4 sw=4 noet :
//
// Copyright 2017, The TPIE development team
// 
// This file is part of TPIE.
// 
// TPIE 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.
// 
// TPIE 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 TPIE.  If not, see <http://www.gnu.org/licenses/>
 
 
#ifndef __TPIE_SPIN_LOCK_H__
#define __TPIE_SPIN_LOCK_H__
 
#include <atomic>
#include <limits>
 
namespace tpie {
 
class unique_spin_lock {
public:
    unique_spin_lock(std::atomic_size_t & spin): spin(spin) {
        while (true) {
            size_t expected = 0;
            if (spin.compare_exchange_weak(expected, 0x80000000)) return;
        }
    }
    ~unique_spin_lock() {
        spin -= 0x80000000;
    }
private:
    std::atomic_size_t & spin;
};
 
 
class shared_spin_lock {
public:
    shared_spin_lock(std::atomic_size_t & spin): spin(spin), locked(false) {
        acquire();
    }
    void release() {
        --spin;
        locked = false;
    }
 
    void acquire() {
        spin++;
        while (spin.load() >= 0x80000000) {}
        locked = true;
    }
    
    ~shared_spin_lock() {
        if (locked) release();
    }
private:
    std::atomic_size_t & spin;
    bool locked;
};
 
} //namespace tpie
#endif //__TPIE_SPIN_LOCK_H__