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      1 /*
      2  * pthread_rwlock_destroy.c
      3  *
      4  * Description:
      5  * This translation unit implements read/write lock primitives.
      6  *
      7  * --------------------------------------------------------------------------
      8  *
      9  *      Pthreads-win32 - POSIX Threads Library for Win32
     10  *      Copyright(C) 1998 John E. Bossom
     11  *      Copyright(C) 1999,2005 Pthreads-win32 contributors
     12  *
     13  *      Contact Email: rpj (at) callisto.canberra.edu.au
     14  *
     15  *      The current list of contributors is contained
     16  *      in the file CONTRIBUTORS included with the source
     17  *      code distribution. The list can also be seen at the
     18  *      following World Wide Web location:
     19  *      http://sources.redhat.com/pthreads-win32/contributors.html
     20  *
     21  *      This library is free software; you can redistribute it and/or
     22  *      modify it under the terms of the GNU Lesser General Public
     23  *      License as published by the Free Software Foundation; either
     24  *      version 2 of the License, or (at your option) any later version.
     25  *
     26  *      This library is distributed in the hope that it will be useful,
     27  *      but WITHOUT ANY WARRANTY; without even the implied warranty of
     28  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     29  *      Lesser General Public License for more details.
     30  *
     31  *      You should have received a copy of the GNU Lesser General Public
     32  *      License along with this library in the file COPYING.LIB;
     33  *      if not, write to the Free Software Foundation, Inc.,
     34  *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
     35  */
     36 
     37 #include <limits.h>
     38 
     39 #include "pthread.h"
     40 #include "implement.h"
     41 
     42 int
     43 pthread_rwlock_destroy (pthread_rwlock_t * rwlock)
     44 {
     45   pthread_rwlock_t rwl;
     46   int result = 0, result1 = 0, result2 = 0;
     47 
     48   if (rwlock == NULL || *rwlock == NULL)
     49     {
     50       return EINVAL;
     51     }
     52 
     53   if (*rwlock != PTHREAD_RWLOCK_INITIALIZER)
     54     {
     55       rwl = *rwlock;
     56 
     57       if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
     58 	{
     59 	  return EINVAL;
     60 	}
     61 
     62       if ((result = pthread_mutex_lock (&(rwl->mtxExclusiveAccess))) != 0)
     63 	{
     64 	  return result;
     65 	}
     66 
     67       if ((result =
     68 	   pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
     69 	{
     70 	  (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
     71 	  return result;
     72 	}
     73 
     74       /*
     75        * Check whether any threads own/wait for the lock (wait for ex.access);
     76        * report "BUSY" if so.
     77        */
     78       if (rwl->nExclusiveAccessCount > 0
     79 	  || rwl->nSharedAccessCount > rwl->nCompletedSharedAccessCount)
     80 	{
     81 	  result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
     82 	  result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
     83 	  result2 = EBUSY;
     84 	}
     85       else
     86 	{
     87 	  rwl->nMagic = 0;
     88 
     89 	  if ((result =
     90 	       pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
     91 	    {
     92 	      pthread_mutex_unlock (&rwl->mtxExclusiveAccess);
     93 	      return result;
     94 	    }
     95 
     96 	  if ((result =
     97 	       pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) != 0)
     98 	    {
     99 	      return result;
    100 	    }
    101 
    102 	  *rwlock = NULL;	/* Invalidate rwlock before anything else */
    103 	  result = pthread_cond_destroy (&(rwl->cndSharedAccessCompleted));
    104 	  result1 = pthread_mutex_destroy (&(rwl->mtxSharedAccessCompleted));
    105 	  result2 = pthread_mutex_destroy (&(rwl->mtxExclusiveAccess));
    106 	  (void) free (rwl);
    107 	}
    108     }
    109   else
    110     {
    111       ptw32_mcs_local_node_t node;
    112       /*
    113        * See notes in ptw32_rwlock_check_need_init() above also.
    114        */
    115       ptw32_mcs_lock_acquire(&ptw32_rwlock_test_init_lock, &node);
    116 
    117       /*
    118        * Check again.
    119        */
    120       if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
    121 	{
    122 	  /*
    123 	   * This is all we need to do to destroy a statically
    124 	   * initialised rwlock that has not yet been used (initialised).
    125 	   * If we get to here, another thread
    126 	   * waiting to initialise this rwlock will get an EINVAL.
    127 	   */
    128 	  *rwlock = NULL;
    129 	}
    130       else
    131 	{
    132 	  /*
    133 	   * The rwlock has been initialised while we were waiting
    134 	   * so assume it's in use.
    135 	   */
    136 	  result = EBUSY;
    137 	}
    138 
    139       ptw32_mcs_lock_release(&node);
    140     }
    141 
    142   return ((result != 0) ? result : ((result1 != 0) ? result1 : result2));
    143 }
    144