| /* |
| * pthread_rwlock_check_need_init.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 "pthread.h" |
| #include "implement.h" |
| |
| INLINE int |
| ptw32_rwlock_check_need_init (pthread_rwlock_t * rwlock) |
| { |
| int result = 0; |
| |
| /* |
| * The following guarded test is specifically for statically |
| * initialised rwlocks (via PTHREAD_RWLOCK_INITIALIZER). |
| * |
| * Note that by not providing this synchronisation we risk |
| * introducing race conditions into applications which are |
| * correctly written. |
| * |
| * Approach |
| * -------- |
| * We know that static rwlocks will not be PROCESS_SHARED |
| * so we can serialise access to internal state using |
| * Win32 Critical Sections rather than Win32 Mutexes. |
| * |
| * If using a single global lock slows applications down too much, |
| * multiple global locks could be created and hashed on some random |
| * value associated with each mutex, the pointer perhaps. At a guess, |
| * a good value for the optimal number of global locks might be |
| * the number of processors + 1. |
| * |
| */ |
| EnterCriticalSection (&ptw32_rwlock_test_init_lock); |
| |
| /* |
| * We got here possibly under race |
| * conditions. Check again inside the critical section |
| * and only initialise if the rwlock is valid (not been destroyed). |
| * If a static rwlock has been destroyed, the application can |
| * re-initialise it only by calling pthread_rwlock_init() |
| * explicitly. |
| */ |
| if (*rwlock == PTHREAD_RWLOCK_INITIALIZER) |
| { |
| result = pthread_rwlock_init (rwlock, NULL); |
| } |
| else if (*rwlock == NULL) |
| { |
| /* |
| * The rwlock has been destroyed while we were waiting to |
| * initialise it, so the operation that caused the |
| * auto-initialisation should fail. |
| */ |
| result = EINVAL; |
| } |
| |
| LeaveCriticalSection (&ptw32_rwlock_test_init_lock); |
| |
| return result; |
| } |