diff options
Diffstat (limited to 'pthreads/pthread_barrier_wait.c')
| -rw-r--r-- | pthreads/pthread_barrier_wait.c | 203 |
1 files changed, 104 insertions, 99 deletions
diff --git a/pthreads/pthread_barrier_wait.c b/pthreads/pthread_barrier_wait.c index 01ae29766..a19582583 100644 --- a/pthreads/pthread_barrier_wait.c +++ b/pthreads/pthread_barrier_wait.c @@ -1,99 +1,104 @@ -/* - * 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) 1999,2005 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" - - -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 - { - /* - * Use the non-cancelable version of sem_wait(). - */ - result = ptw32_semwait (&(b->semBarrierBreeched[step])); - } - - /* - * 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); -} +/*
+ * 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) 1999,2005 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"
+
+
+int
+pthread_barrier_wait (pthread_barrier_t * barrier)
+{
+ int result;
+ pthread_barrier_t b;
+
+ ptw32_mcs_local_node_t node;
+
+ if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
+ {
+ return EINVAL;
+ }
+
+ ptw32_mcs_lock_acquire((ptw32_mcs_lock_t *)&(*barrier)->lock, &node);
+
+ b = *barrier;
+ if (--b->nCurrentBarrierHeight == 0)
+ {
+ /*
+ * We are the last thread to arrive at the barrier before it releases us.
+ * Move our MCS local node to the global scope barrier handle so that the
+ * last thread out (not necessarily us) can release the lock.
+ */
+ ptw32_mcs_node_substitute(&b->proxynode, &node);
+
+ /*
+ * Any threads that have not quite entered sem_wait below when the
+ * multiple_post has completed will nevertheless continue through
+ * the semaphore (barrier).
+ */
+ result = (b->nInitialBarrierHeight > 1
+ ? sem_post_multiple (&(b->semBarrierBreeched),
+ b->nInitialBarrierHeight - 1) : 0);
+ }
+ else
+ {
+ ptw32_mcs_lock_release(&node);
+ /*
+ * Use the non-cancelable version of sem_wait().
+ *
+ * It is possible that all nInitialBarrierHeight-1 threads are
+ * at this point when the last thread enters the barrier, resets
+ * nCurrentBarrierHeight = nInitialBarrierHeight and leaves.
+ * If pthread_barrier_destroy is called at that moment then the
+ * barrier will be destroyed along with the semas.
+ */
+ result = ptw32_semwait (&(b->semBarrierBreeched));
+ }
+
+ if ((PTW32_INTERLOCKED_LONG)InterlockedIncrement((LPLONG)&b->nCurrentBarrierHeight)
+ == (PTW32_INTERLOCKED_LONG)b->nInitialBarrierHeight)
+ {
+ /*
+ * We are the last thread to cross this barrier
+ */
+ ptw32_mcs_lock_release(&b->proxynode);
+ if (0 == result)
+ {
+ result = PTHREAD_BARRIER_SERIAL_THREAD;
+ }
+ }
+
+ return (result);
+}
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