/* * pthread_rwlock_rdlock.c * * Description: * This translation unit implements read/write lock primitives. * * -------------------------------------------------------------------------- * *      Pthreads-win32 - POSIX Threads Library for Win32 *      Copyright(C) 1998 John E. Bossom *      Copyright(C) 1999,2005 Pthreads-win32 contributors *  *      Contact Email: rpj@callisto.canberra.edu.au *  *      The current list of contributors is contained *      in the file CONTRIBUTORS included with the source *      code distribution. The list can also be seen at the *      following World Wide Web location: *      http://sources.redhat.com/pthreads-win32/contributors.html *  *      This library is free software; you can redistribute it and/or *      modify it under the terms of the GNU Lesser General Public *      License as published by the Free Software Foundation; either *      version 2 of the License, or (at your option) any later version. *  *      This library is distributed in the hope that it will be useful, *      but WITHOUT ANY WARRANTY; without even the implied warranty of *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU *      Lesser General Public License for more details. *  *      You should have received a copy of the GNU Lesser General Public *      License along with this library in the file COPYING.LIB; *      if not, write to the Free Software Foundation, Inc., *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */#include <errno.h>#include <limits.h>#include "pthread.h"#include "implement.h"intpthread_rwlock_rdlock (pthread_rwlock_t * rwlock){  int result;  pthread_rwlock_t rwl;  if (rwlock == NULL || *rwlock == NULL)    {      return EINVAL;    }  /*   * We do a quick check to see if we need to do more work   * to initialise a static rwlock. We check   * again inside the guarded section of ptw32_rwlock_check_need_init()   * to avoid race conditions.   */  if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)    {      result = ptw32_rwlock_check_need_init (rwlock);      if (result != 0 && result != EBUSY)	{	  return result;	}    }  rwl = *rwlock;  if (rwl->nMagic != PTW32_RWLOCK_MAGIC)    {      return EINVAL;    }  if ((result = pthread_mutex_lock (&(rwl->mtxExclusiveAccess))) != 0)    {      return result;    }  if (++rwl->nSharedAccessCount == INT_MAX)    {      if ((result =	   pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)	{	  (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));	  return result;	}      rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;      rwl->nCompletedSharedAccessCount = 0;      if ((result =	   pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)	{	  (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));	  return result;	}    }  return (pthread_mutex_unlock (&(rwl->mtxExclusiveAccess)));}