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  • Committer: Bazaar Package Importer
  • Author(s): Kees Cook
  • Date: 2007-02-20 10:33:44 UTC
  • mto: This revision was merged to the branch mainline in revision 16.
  • Revision ID: james.westby@ubuntu.com-20070220103344-zgcu2psnx9d98fpa
Tags: upstream-0.90
Import upstream version 0.90

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win32/3rdparty/pthreads/pthread_rwlock_trywrlock.c
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/*
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 * pthread_rwlock_trywrlock.c
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 *
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 * Description:
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 * This translation unit implements read/write lock primitives.
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 *
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 * --------------------------------------------------------------------------
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 *
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 *      Pthreads-win32 - POSIX Threads Library for Win32
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 *      Copyright(C) 1998 John E. Bossom
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 *      Copyright(C) 1999,2005 Pthreads-win32 contributors
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 * 
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 *      Contact Email: rpj@callisto.canberra.edu.au
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 * 
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 *      The current list of contributors is contained
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 *      in the file CONTRIBUTORS included with the source
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 *      code distribution. The list can also be seen at the
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 *      following World Wide Web location:
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 *      http://sources.redhat.com/pthreads-win32/contributors.html
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 * 
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 *      This library is free software; you can redistribute it and/or
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 *      modify it under the terms of the GNU Lesser General Public
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 *      License as published by the Free Software Foundation; either
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 *      version 2 of the License, or (at your option) any later version.
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 * 
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 *      This library is distributed in the hope that it will be useful,
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 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
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 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 *      Lesser General Public License for more details.
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 * 
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 *      You should have received a copy of the GNU Lesser General Public
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 *      License along with this library in the file COPYING.LIB;
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 *      if not, write to the Free Software Foundation, Inc.,
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 *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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 */
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#include <limits.h>
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#include "pthread.h"
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#include "implement.h"
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int
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pthread_rwlock_trywrlock (pthread_rwlock_t * rwlock)
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{
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  int result, result1;
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  pthread_rwlock_t rwl;
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  if (rwlock == NULL || *rwlock == NULL)
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    {
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      return EINVAL;
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    }
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  /*
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   * We do a quick check to see if we need to do more work
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   * to initialise a static rwlock. We check
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   * again inside the guarded section of ptw32_rwlock_check_need_init()
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   * to avoid race conditions.
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   */
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  if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
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    {
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      result = ptw32_rwlock_check_need_init (rwlock);
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      if (result != 0 && result != EBUSY)
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        {
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          return result;
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        }
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    }
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  rwl = *rwlock;
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  if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
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    {
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      return EINVAL;
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    }
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  if ((result = pthread_mutex_trylock (&(rwl->mtxExclusiveAccess))) != 0)
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    {
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      return result;
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    }
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  if ((result =
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       pthread_mutex_trylock (&(rwl->mtxSharedAccessCompleted))) != 0)
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    {
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      result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
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      return ((result1 != 0) ? result1 : result);
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    }
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  if (rwl->nExclusiveAccessCount == 0)
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    {
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      if (rwl->nCompletedSharedAccessCount > 0)
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        {
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          rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
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          rwl->nCompletedSharedAccessCount = 0;
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        }
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      if (rwl->nSharedAccessCount > 0)
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        {
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          if ((result =
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               pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
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            {
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              (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
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              return result;
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            }
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          if ((result =
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               pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) == 0)
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            {
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              result = EBUSY;
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            }
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        }
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      else
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        {
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          rwl->nExclusiveAccessCount = 1;
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        }
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    }
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  else
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    {
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      result = EBUSY;
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    }
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  return result;
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}