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      1 /*
      2  * pthread_rwlock_unlock.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_unlock (pthread_rwlock_t * rwlock)
     44 {
     45   int result, result1;
     46   pthread_rwlock_t rwl;
     47 
     48   if (rwlock == NULL || *rwlock == NULL)
     49     {
     50       return (EINVAL);
     51     }
     52 
     53   if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
     54     {
     55       /*
     56        * Assume any race condition here is harmless.
     57        */
     58       return 0;
     59     }
     60 
     61   rwl = *rwlock;
     62 
     63   if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
     64     {
     65       return EINVAL;
     66     }
     67 
     68   if (rwl->nExclusiveAccessCount == 0)
     69     {
     70       if ((result =
     71 	   pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
     72 	{
     73 	  return result;
     74 	}
     75 
     76       if (++rwl->nCompletedSharedAccessCount == 0)
     77 	{
     78 	  result = pthread_cond_signal (&(rwl->cndSharedAccessCompleted));
     79 	}
     80 
     81       result1 = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
     82     }
     83   else
     84     {
     85       rwl->nExclusiveAccessCount--;
     86 
     87       result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
     88       result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
     89 
     90     }
     91 
     92   return ((result != 0) ? result : result1);
     93 }
     94