native_client_sdk/src/libraries/third_party/pthreads-win32/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) 1999,2005 Pthreads-win32 contributors
  12  *
  13  *      Contact Email: rpj@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_trywrlock (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   /*
  54    * We do a quick check to see if we need to do more work
  55    * to initialise a static rwlock. We check
  56    * again inside the guarded section of ptw32_rwlock_check_need_init()
  57    * to avoid race conditions.
  58    */
  59   if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
  60     {
  61       result = ptw32_rwlock_check_need_init (rwlock);
  62
  63       if (result != 0 && result != EBUSY)
  64         {
  65           return result;
  66         }
  67     }
  68
  69   rwl = *rwlock;
  70
  71   if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
  72     {
  73       return EINVAL;
  74     }
  75
  76   if ((result = pthread_mutex_trylock (&(rwl->mtxExclusiveAccess))) != 0)
  77     {
  78       return result;
  79     }
  80
  81   if ((result =
  82        pthread_mutex_trylock (&(rwl->mtxSharedAccessCompleted))) != 0)
  83     {
  84       result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
  85       return ((result1 != 0) ? result1 : result);
  86     }
  87
  88   if (rwl->nExclusiveAccessCount == 0)
  89     {
  90       if (rwl->nCompletedSharedAccessCount > 0)
  91         {
  92           rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
  93           rwl->nCompletedSharedAccessCount = 0;
  94         }
  95
  96       if (rwl->nSharedAccessCount > 0)
  97         {
  98           if ((result =
  99                pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
 100             {
 101               (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
 102               return result;
 103             }
 104
 105           if ((result =
 106                pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) == 0)
 107             {
 108               result = EBUSY;
 109             }
 110         }
 111       else
 112         {
 113           rwl->nExclusiveAccessCount = 1;
 114         }
 115     }
 116   else
 117     {
 118       result = EBUSY;
 119     }
 120
 121   return result;
 122 }