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-rw-r--r--pthreads/pthread_barrier_wait.c203
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);
+}