orte/liborte/rtl/pthread_rwlock_tryrdlock.c

   1 /*
   2  * pthread_rwlock_tryrdlock.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
  45 int
  46 pthread_rwlock_tryrdlock(pthread_rwlock_t * rwlock)
  47 {
  48     int result;
  49     pthread_rwlock_t rwl;
  50
  51     if (rwlock == NULL || *rwlock == NULL)
  52       {
  53         return EINVAL;
  54       }
  55
  56     /*
  57      * We do a quick check to see if we need to do more work
  58      * to initialise a static rwlock. We check
  59      * again inside the guarded section of ptw32_rwlock_check_need_init()
  60      * to avoid race conditions.
  61      */
  62     if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
  63       {
  64         result = ptw32_rwlock_check_need_init(rwlock);
  65
  66         if (result != 0 && result != EBUSY)
  67           {
  68             return result;
  69           }
  70       }
  71
  72     rwl = *rwlock;
  73
  74     if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
  75       {
  76         return EINVAL;
  77       }
  78
  79     if ((result = pthread_mutex_trylock(&(rwl->mtxExclusiveAccess))) != 0)
  80       {
  81         return result;
  82       }
  83
  84     if (++rwl->nSharedAccessCount == INT_MAX)
  85       {
  86         if ((result = pthread_mutex_lock(&(rwl->mtxSharedAccessCompleted))) != 0)
  87           {
  88             (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
  89             return result;
  90           }
  91
  92         rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
  93         rwl->nCompletedSharedAccessCount = 0;
  94
  95         if ((result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted))) != 0)
  96           {
  97             (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
  98             return result;
  99           }
 100       }
 101
 102     return (pthread_mutex_unlock(&rwl->mtxExclusiveAccess));
 103 }