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authorrpj <rpj>2002-02-08 01:51:17 +0000
committerrpj <rpj>2002-02-08 01:51:17 +0000
commitb29903300adc22ed277bbaa356aca8ed0c245957 (patch)
tree02921a99a145dda1e78a315cc75016443839f2e0 /barrier_wait.c
parent14118935d2d6863a4746223d8e22c2e58ffebab5 (diff)
Copyright notice updates; module splitting; POSIX version
conditional compilation; refinements; bug fixes. See the ChangeLog.
Diffstat (limited to 'barrier_wait.c')
-rw-r--r--barrier_wait.c114
1 files changed, 114 insertions, 0 deletions
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+/*
+ * 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);
+}
+