relibc_pthreads-emb/pthread_spin_trylock.c

/*
 * pthread_spin_trylock.c
 *
 * Description:
 * This translation unit implements spin lock primitives.
 *
 * --------------------------------------------------------------------------
 *
 *      Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
 *      Copyright(C) 2008 Jason Schmidlapp
 *
 *      Contact Email: jschmidlapp@users.sourceforge.net
 *
 *
 *      Based upon Pthreads-win32 - POSIX Threads Library for Win32
 *      Copyright(C) 1998 John E. Bossom
 *      Copyright(C) 1999,2005 Pthreads-win32 contributors
 *
 *      Contact Email: rpj@callisto.canberra.edu.au
 *
 *      The original list of contributors to the Pthreads-win32 project
 *      is contained in the file CONTRIBUTORS.ptw32 included with the
 *      source code distribution. The list can also be seen at the
 *      following World Wide Web location:
 *      http://sources.redhat.com/pthreads-win32/contributors.html
 *
 *      This library 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 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
 *      Lesser General Public License for more details.
 *
 *      You should have received a copy of the GNU Lesser General Public
 *      License along with this library in the file COPYING.LIB;
 *      if not, write to the Free Software Foundation, Inc.,
 *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */


#include "pthread.h"
#include "implement.h"


int
pthread_spin_trylock (pthread_spinlock_t * lock)
{
  register pthread_spinlock_t s;

  if (NULL == lock || NULL == *lock)
    {
      return (EINVAL);
    }

  if (*lock == PTHREAD_SPINLOCK_INITIALIZER)
    {
      int result;

      if ((result = pte_spinlock_check_need_init (lock)) != 0)
        {
          return (result);
        }
    }

  s = *lock;

  switch ((long)
          PTE_ATOMIC_COMPARE_EXCHANGE (&(s->interlock),
                                       PTE_SPIN_LOCKED,
                                       PTE_SPIN_UNLOCKED))
    {
    case PTE_SPIN_UNLOCKED:
      return 0;
    case PTE_SPIN_LOCKED:
      return EBUSY;
    case PTE_SPIN_USE_MUTEX:
      return pthread_mutex_trylock (&(s->u.mutex));
    }

  return EINVAL;
}