pthread_rwlock_destroy.c

/*
 * pthread_rwlock_destroy.c
 *
 * Description:
 * This translation unit implements read/write 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 <stdlib.h>
#include <errno.h>
#include <limits.h>

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

int
pthread_rwlock_destroy (pthread_rwlock_t * rwlock)
{
  pthread_rwlock_t rwl;
  int result = 0, result1 = 0, result2 = 0;

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

  if (*rwlock != PTHREAD_RWLOCK_INITIALIZER)
    {
      rwl = *rwlock;

      if (rwl->nMagic != PTE_RWLOCK_MAGIC)
        {
          return EINVAL;
        }

      if ((result = pthread_mutex_lock (&(rwl->mtxExclusiveAccess))) != 0)
        {
          return result;
        }

      if ((result =
             pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
        {
          (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
          return result;
        }

      /*
       * Check whether any threads own/wait for the lock (wait for ex.access);
       * report "BUSY" if so.
       */
      if (rwl->nExclusiveAccessCount > 0
          || rwl->nSharedAccessCount > rwl->nCompletedSharedAccessCount)
        {
          result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
          result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
          result2 = EBUSY;
        }
      else
        {
          rwl->nMagic = 0;

          if ((result =
                 pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
            {
              pthread_mutex_unlock (&rwl->mtxExclusiveAccess);
              return result;
            }

          if ((result =
                 pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) != 0)
            {
              return result;
            }

          *rwlock = NULL;	/* Invalidate rwlock before anything else */
          result = pthread_cond_destroy (&(rwl->cndSharedAccessCompleted));
          result1 = pthread_mutex_destroy (&(rwl->mtxSharedAccessCompleted));
          result2 = pthread_mutex_destroy (&(rwl->mtxExclusiveAccess));
          (void) free (rwl);
        }
    }
  else
    {
      /*
       * See notes in pte_rwlock_check_need_init() above also.
       */

      pte_osMutexLock (pte_rwlock_test_init_lock);

      /*
       * Check again.
       */
      if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
        {
          /*
           * This is all we need to do to destroy a statically
           * initialised rwlock that has not yet been used (initialised).
           * If we get to here, another thread
           * waiting to initialise this rwlock will get an EINVAL.
           */
          *rwlock = NULL;
        }
      else
        {
          /*
           * The rwlock has been initialised while we were waiting
           * so assume it's in use.
           */
          result = EBUSY;
        }

      pte_osMutexUnlock(pte_rwlock_test_init_lock);

    }

  return ((result != 0) ? result : ((result1 != 0) ? result1 : result2));
}