File indexing completed on 2024-04-28 16:59:49

 /*
    Copyright (C) 2014 Andreas Hartmetz <ahartmetz@gmail.com>
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.
 
    This library 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
    Library General Public License for more details.
 
    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LGPL.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
 
    Alternatively, this file is available under the Mozilla Public License
    Version 1.1.  You may obtain a copy of the License at
    http://www.mozilla.org/MPL/
 */
 
 #ifndef SPINLOCK_H
 #define SPINLOCK_H
 
 #include <atomic>
 #include <cassert>
 
 #ifdef HAVE_VALGRIND
 #include <valgrind/helgrind.h>
 #else
 #include "valgrind-noop.h"
 #endif
 
 class Spinlock
 {
 public:
     Spinlock()
     {
         VALGRIND_HG_MUTEX_INIT_POST(this, 0);
     }
 
     // The assertion does two things (in debug mode):
     // - Check that a locked Spinlock is not destroyed
     // - Check that a destroyed Spinlock is not locked, by forcing a deadlock in that case
     //   (if the memory has not yet been overwritten)
     ~Spinlock()
     {
         VALGRIND_HG_MUTEX_DESTROY_PRE(this);
         assert(!m_locked.test_and_set(std::memory_order_acquire));
     }
 
     void lock()
     {
         VALGRIND_HG_MUTEX_LOCK_PRE(this, 0);
         while (m_locked.test_and_set(std::memory_order_acquire)) {
             // spin until locked
         }
         VALGRIND_HG_MUTEX_LOCK_POST(this);
     }
 
     void unlock()
     {
         VALGRIND_HG_MUTEX_UNLOCK_PRE(this);
         m_locked.clear(std::memory_order_release);
         VALGRIND_HG_MUTEX_UNLOCK_POST(this);
     }
 private:
     std::atomic_flag m_locked = ATOMIC_FLAG_INIT;
 };
 
 class SpinLocker
 {
 public:
     SpinLocker(Spinlock *lock)
        : m_lock(lock)
     {
         m_lock->lock();
     }
 
     ~SpinLocker()
     {
         m_lock->unlock();
     }
 private:
     Spinlock *m_lock;
 };
 
 #endif // SPINLOCK_H