Implement PThreads barriers and barrier attributes.

1 files changed, 129 insertions, 0 deletions

diff --git a/lib/libthr/thread/thr_barrier.c b/lib/libthr/thread/thr_barrier.c
new file mode 100644
index 0000000..c635820
--- /dev/null
+++ b/lib/libthr/thread/thr_barrier.c
@@ -0,0 +1,129 @@
+/*-
+ * Copyright (c) 2004 Michael Telahun Makonnen <mtm@FreeBSD.Org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <pthread.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "thr_private.h"
+
+__weak_reference(_pthread_barrier_destroy, pthread_barrier_destroy);
+__weak_reference(_pthread_barrier_init, pthread_barrier_init);
+__weak_reference(_pthread_barrier_wait, pthread_barrier_wait);
+
+int
+_pthread_barrier_destroy(pthread_barrier_t *barrier)
+{
+	if (*barrier == NULL)
+		return (EINVAL);
+	if ((*barrier)->b_subtotal > 0)
+		return (EBUSY);
+	PTHREAD_ASSERT((*barrier)->b_subtotal == 0,
+	    "barrier count must be zero when destroyed");
+	free(*barrier);
+	*barrier = NULL;
+	return (0);
+}
+
+int
+_pthread_barrier_init(pthread_barrier_t *barrier,
+    const pthread_barrierattr_t attr, unsigned int count)
+{
+	if (count < 1)
+		return (EINVAL);
+	*barrier =
+	    (struct pthread_barrier *)malloc(sizeof(struct pthread_barrier));
+	if (*barrier == NULL)
+		return (ENOMEM);
+	memset((void *)*barrier, 0, sizeof(struct pthread_barrier));
+	(*barrier)->b_total = count;
+	TAILQ_INIT(&(*barrier)->b_barrq);
+	return (0);
+}
+
+int
+_pthread_barrier_wait(pthread_barrier_t *barrier)
+{
+	struct pthread_barrier *b;
+	struct pthread	       *ptd;
+	int error;
+
+	if (*barrier == NULL)
+		return (EINVAL);
+
+	/*
+	 * Check if threads waiting on the barrier can be released. If
+	 * so, release them and make this last thread the special thread.
+	 */
+	error = 0;
+	b = *barrier;
+	UMTX_LOCK(&b->b_lock);
+	if (b->b_subtotal == (b->b_total - 1)) {
+		TAILQ_FOREACH(ptd, &b->b_barrq, sqe) {
+			_thread_critical_enter(ptd);
+			PTHREAD_NEW_STATE(ptd, PS_RUNNING);
+			TAILQ_REMOVE(&b->b_barrq, ptd, sqe);
+			ptd->flags |= PTHREAD_FLAGS_BARR_REL;
+			_thread_critical_exit(ptd);
+		}
+		b->b_subtotal = 0;
+		UMTX_UNLOCK(&b->b_lock);
+		return (PTHREAD_BARRIER_SERIAL_THREAD);
+	}
+
+	/*
+	 * More threads need to reach the barrier. Suspend this thread.
+	 */
+	_thread_critical_enter(curthread);
+	TAILQ_INSERT_HEAD(&b->b_barrq, curthread, sqe);
+	PTHREAD_NEW_STATE(curthread, PS_BARRIER_WAIT);
+	_thread_critical_exit(curthread);
+	b->b_subtotal++;
+	PTHREAD_ASSERT(b->b_subtotal < b->b_total,
+	    "the number of threads waiting at a barrier is too large");
+	UMTX_UNLOCK(&b->b_lock);
+	do {
+		error = _thread_suspend(curthread, NULL);
+		if (error == EINTR) {
+			/*
+			 * Make sure this thread wasn't released from
+			 * the barrier while it was handling the signal.
+			 */
+			_thread_critical_enter(curthread);
+			if ((curthread->flags & PTHREAD_FLAGS_BARR_REL) != 0) {
+				curthread->flags &= ~PTHREAD_FLAGS_BARR_REL;
+				_thread_critical_exit(curthread);
+				error = 0;
+				break;
+			}
+			PTHREAD_NEW_STATE(curthread, PS_BARRIER_WAIT);
+			_thread_critical_exit(curthread);
+		}
+	} while (error == EINTR);
+	return (error);
+}