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      1 /*
      2  * pthread_rwlock_timedrdlock.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_timedrdlock (pthread_rwlock_t * rwlock,
     44 			    const struct timespec *abstime)
     45 {
     46   int result;
     47   pthread_rwlock_t rwl;
     48 
     49   if (rwlock == NULL || *rwlock == NULL)
     50     {
     51       return EINVAL;
     52     }
     53 
     54   /*
     55    * We do a quick check to see if we need to do more work
     56    * to initialise a static rwlock. We check
     57    * again inside the guarded section of ptw32_rwlock_check_need_init()
     58    * to avoid race conditions.
     59    */
     60   if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
     61     {
     62       result = ptw32_rwlock_check_need_init (rwlock);
     63 
     64       if (result != 0 && result != EBUSY)
     65 	{
     66 	  return result;
     67 	}
     68     }
     69 
     70   rwl = *rwlock;
     71 
     72   if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
     73     {
     74       return EINVAL;
     75     }
     76 
     77   if ((result =
     78        pthread_mutex_timedlock (&(rwl->mtxExclusiveAccess), abstime)) != 0)
     79     {
     80       return result;
     81     }
     82 
     83   if (++rwl->nSharedAccessCount == INT_MAX)
     84     {
     85       if ((result =
     86 	   pthread_mutex_timedlock (&(rwl->mtxSharedAccessCompleted),
     87 				    abstime)) != 0)
     88 	{
     89 	  if (result == ETIMEDOUT)
     90 	    {
     91 	      ++rwl->nCompletedSharedAccessCount;
     92 	    }
     93 	  (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
     94 	  return result;
     95 	}
     96 
     97       rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
     98       rwl->nCompletedSharedAccessCount = 0;
     99 
    100       if ((result =
    101 	   pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
    102 	{
    103 	  (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
    104 	  return result;
    105 	}
    106     }
    107 
    108   return (pthread_mutex_unlock (&(rwl->mtxExclusiveAccess)));
    109 }
    110