pthread_mutex_destroy.c

/*
 * pthread_mutex_destroy.c
 *
 * Description:
 * This translation unit implements mutual exclusion (mutex) 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 <stdio.h>
#include <stdlib.h>
#include <string.h>

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


int
pthread_mutex_destroy (pthread_mutex_t * mutex)
{
  int result = 0;
  pthread_mutex_t mx;

  /*
   * Let the system deal with invalid pointers.
   */

  /*
   * Check to see if we have something to delete.
   */
  if (*mutex < PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
    {
      mx = *mutex;

      result = pthread_mutex_trylock (&mx);

      /*
       * If trylock succeeded and the mutex is not recursively locked it
       * can be destroyed.
       */
      if (result == 0)
        {
          if (mx->kind != PTHREAD_MUTEX_RECURSIVE || 1 == mx->recursive_count)
            {
              /*
               * FIXME!!!
               * The mutex isn't held by another thread but we could still
               * be too late invalidating the mutex below since another thread
               * may already have entered mutex_lock and the check for a valid
               * *mutex != NULL.
               *
               * Note that this would be an unusual situation because it is not
               * common that mutexes are destroyed while they are still in
               * use by other threads.
               */
              *mutex = NULL;

              result = pthread_mutex_unlock (&mx);

              if (result == 0)
                {
                  pte_osSemaphoreDelete(mx->handle);

                  free(mx);

                }
              else
                {
                  /*
                   * Restore the mutex before we return the error.
                   */
                  *mutex = mx;
                }
            }
          else			/* mx->recursive_count > 1 */
            {
              /*
               * The mutex must be recursive and already locked by us (this thread).
               */
              mx->recursive_count--;	/* Undo effect of pthread_mutex_trylock() above */
              result = EBUSY;
            }
        }
    }
  else
    {
      /*
       * See notes in pte_mutex_check_need_init() above also.
       */

      pte_osMutexLock (pte_mutex_test_init_lock);


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

      pte_osMutexUnlock(pte_mutex_test_init_lock);

    }

  return (result);
}