| /* |
| * pthread_rwlock_tryrdlock.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 |
| */ |
| |
| #ifndef WINCE |
| #include <errno.h> |
| #endif |
| #include <limits.h> |
| |
| #include "pthread.h" |
| #include "implement.h" |
| |
| int |
| pthread_rwlock_tryrdlock (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_trylock (&(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)); |
| } |