/* * 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) 1999,2003 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" int pthread_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))); }