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Diffstat (limited to 'pthreads/ptw32_mutex_check_need_init.c')
-rw-r--r-- | pthreads/ptw32_mutex_check_need_init.c | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/pthreads/ptw32_mutex_check_need_init.c b/pthreads/ptw32_mutex_check_need_init.c new file mode 100644 index 000000000..35ec366bd --- /dev/null +++ b/pthreads/ptw32_mutex_check_need_init.c @@ -0,0 +1,112 @@ +/* + * ptw32_mutex_check_need_init.c + * + * Description: + * This translation unit implements mutual exclusion (mutex) 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" + +static struct pthread_mutexattr_t_ ptw32_recursive_mutexattr_s = + {PTHREAD_PROCESS_PRIVATE, PTHREAD_MUTEX_RECURSIVE}; +static struct pthread_mutexattr_t_ ptw32_errorcheck_mutexattr_s = + {PTHREAD_PROCESS_PRIVATE, PTHREAD_MUTEX_ERRORCHECK}; +static pthread_mutexattr_t ptw32_recursive_mutexattr = &ptw32_recursive_mutexattr_s; +static pthread_mutexattr_t ptw32_errorcheck_mutexattr = &ptw32_errorcheck_mutexattr_s; + + +INLINE int +ptw32_mutex_check_need_init (pthread_mutex_t * mutex) +{ + register int result = 0; + register pthread_mutex_t mtx; + + /* + * The following guarded test is specifically for statically + * initialised mutexes (via PTHREAD_MUTEX_INITIALIZER). + * + * Note that by not providing this synchronisation we risk + * introducing race conditions into applications which are + * correctly written. + * + * Approach + * -------- + * We know that static mutexes 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_mutex_test_init_lock); + + /* + * We got here possibly under race + * conditions. Check again inside the critical section + * and only initialise if the mutex is valid (not been destroyed). + * If a static mutex has been destroyed, the application can + * re-initialise it only by calling pthread_mutex_init() + * explicitly. + */ + mtx = *mutex; + + if (mtx == PTHREAD_MUTEX_INITIALIZER) + { + result = pthread_mutex_init (mutex, NULL); + } + else if (mtx == PTHREAD_RECURSIVE_MUTEX_INITIALIZER) + { + result = pthread_mutex_init (mutex, &ptw32_recursive_mutexattr); + } + else if (mtx == PTHREAD_ERRORCHECK_MUTEX_INITIALIZER) + { + result = pthread_mutex_init (mutex, &ptw32_errorcheck_mutexattr); + } + else if (mtx == NULL) + { + /* + * The mutex has been destroyed while we were waiting to + * initialise it, so the operation that caused the + * auto-initialisation should fail. + */ + result = EINVAL; + } + + LeaveCriticalSection (&ptw32_mutex_test_init_lock); + + return (result); +} |