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Diffstat (limited to 'pthread_barrier_wait.c')
| -rw-r--r-- | pthread_barrier_wait.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/pthread_barrier_wait.c b/pthread_barrier_wait.c new file mode 100644 index 0000000..e06e87d --- /dev/null +++ b/pthread_barrier_wait.c @@ -0,0 +1,114 @@ +/* + * pthread_barrier_wait.c + * + * Description: + * This translation unit implements barrier primitives. + * + * -------------------------------------------------------------------------- + * + * Pthreads-win32 - POSIX Threads Library for Win32 + * Copyright(C) 1998 John E. Bossom + * Copyright(C) 1999,2002 Pthreads-win32 contributors + * + * Contact Email: rpj@ise.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" + + +int +pthread_barrier_wait(pthread_barrier_t *barrier) +{ + int result; + int step; + pthread_barrier_t b; + + if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID) + { + return EINVAL; + } + + b = *barrier; + step = b->iStep; + + if (0 == InterlockedDecrement((long *) &(b->nCurrentBarrierHeight))) + { + /* Must be done before posting the semaphore. */ + b->nCurrentBarrierHeight = b->nInitialBarrierHeight; + + /* + * There is no race condition between the semaphore wait and post + * because we are using two alternating semas and all threads have + * entered barrier_wait and checked nCurrentBarrierHeight before this + * barrier's sema can be posted. Any threads that have not quite + * entered sem_wait below when the multiple_post has completed + * will nevertheless continue through the semaphore (barrier) + * and will not be left stranded. + */ + result = (b->nInitialBarrierHeight > 1 + ? sem_post_multiple(&(b->semBarrierBreeched[step]), + b->nInitialBarrierHeight - 1) + : 0); + } + else + { + BOOL switchCancelState; + int oldCancelState; + pthread_t self = pthread_self(); + + /* + * This routine is not a cancelation point, so temporarily + * prevent sem_wait() from being one. + * PTHREAD_CANCEL_ASYNCHRONOUS threads can still be canceled. + */ + switchCancelState = (self->cancelType == PTHREAD_CANCEL_DEFERRED && + 0 == pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, + &oldCancelState)); + + result = sem_wait(&(b->semBarrierBreeched[step])); + + if (switchCancelState) + { + (void) pthread_setcancelstate(oldCancelState, NULL); + } + } + + /* + * The first thread across will be the PTHREAD_BARRIER_SERIAL_THREAD. + * This also sets up the alternate semaphore as the next barrier. + */ + if (0 == result) + { + result = ((PTW32_INTERLOCKED_LONG) step == + ptw32_interlocked_compare_exchange((PTW32_INTERLOCKED_LPLONG) &(b->iStep), + (PTW32_INTERLOCKED_LONG) (1L - step), + (PTW32_INTERLOCKED_LONG) step) + ? PTHREAD_BARRIER_SERIAL_THREAD + : 0); + } + + return(result); +} + |