orte/liborte/rtl/pthread_rwlock_trywrlock.c

   1 /*
   2  * pthread_rwlock_trywrlock.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) 1999,2002 Pthreads-win32 contributors
  12  *
  13  *      Contact Email: rpj@ise.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 <errno.h>
  38 //#include <limits.h>
  39
  40 //#include "pthread.h"
  41 //#include "implement.h"
  42
  43 #include "orte.h"
  44 int
  45 pthread_rwlock_trywrlock(pthread_rwlock_t * rwlock)
  46 {
  47     int result, result1;
  48     pthread_rwlock_t rwl;
  49
  50     if (rwlock == NULL || *rwlock == NULL)
  51       {
  52         return EINVAL;
  53       }
  54
  55     /*
  56      * We do a quick check to see if we need to do more work
  57      * to initialise a static rwlock. We check
  58      * again inside the guarded section of ptw32_rwlock_check_need_init()
  59      * to avoid race conditions.
  60      */
  61     if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
  62       {
  63         result = ptw32_rwlock_check_need_init(rwlock);
  64
  65         if (result != 0 && result != EBUSY)
  66           {
  67             return result;
  68           }
  69       }
  70
  71     rwl = *rwlock;
  72
  73     if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
  74       {
  75         return EINVAL;
  76       }
  77
  78     if ((result = pthread_mutex_trylock(&(rwl->mtxExclusiveAccess))) != 0)
  79       {
  80         return result;
  81       }
  82
  83     if ((result = pthread_mutex_trylock(&(rwl->mtxSharedAccessCompleted))) != 0)
  84       {
  85         result1 = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
  86         return ((result1 != 0) ? result1 : result);
  87       }
  88
  89     if (rwl->nExclusiveAccessCount == 0)
  90       {
  91         if (rwl->nCompletedSharedAccessCount > 0)
  92           {
  93             rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
  94             rwl->nCompletedSharedAccessCount = 0;
  95           }
  96
  97         if (rwl->nSharedAccessCount > 0)
  98           {
  99             if ((result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted))) != 0)
 100               {
 101                 (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
 102                 return result;
 103               }
 104
 105             if ((result = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess))) == 0)
 106               {
 107                 result = EBUSY;
 108               }
 109           }
 110         else
 111           {
 112             rwl->nExclusiveAccessCount = 1;
 113           }
 114       }
 115     else
 116       {
 117         result = EBUSY;
 118       }
 119
 120     return result;
 121 }