1 files changed, 118 insertions, 0 deletions
diff --git a/usr/src/uts/common/fs/zfs/rprwlock.c b/usr/src/uts/common/fs/zfs/rprwlock.c
new file mode 100644
index 0000000000..49ae505209
--- /dev/null
+++ b/usr/src/uts/common/fs/zfs/rprwlock.c
@@ -0,0 +1,118 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+
+#include <sys/zfs_context.h>
+#include <sys/refcount.h>
+#include <sys/rprwlock.h>
+
+void
+rprw_init(rprwlock_t *rwl)
+{
+	mutex_init(&rwl->rw_lock, NULL, MUTEX_DEFAULT, NULL);
+	rwl->rw_writer = NULL;
+	cv_init(&rwl->rw_cv, NULL, CV_DEFAULT, NULL);
+	refcount_create(&rwl->rw_count);
+}
+
+void
+rprw_destroy(rprwlock_t *rwl)
+{
+	mutex_destroy(&rwl->rw_lock);
+	ASSERT(rwl->rw_writer == NULL);
+	cv_destroy(&rwl->rw_cv);
+	refcount_destroy(&rwl->rw_count);
+}
+
+void
+rprw_enter_read(rprwlock_t *rwl, void *tag)
+{
+	mutex_enter(&rwl->rw_lock);
+
+	if (rwl->rw_writer != curthread) {
+		while (rwl->rw_writer != NULL)
+			cv_wait(&rwl->rw_cv, &rwl->rw_lock);
+	}
+
+	(void) refcount_add(&rwl->rw_count, tag);
+
+	mutex_exit(&rwl->rw_lock);
+}
+
+void
+rprw_enter_write(rprwlock_t *rwl, void *tag)
+{
+	mutex_enter(&rwl->rw_lock);
+
+	if (rwl->rw_writer != curthread) {
+		while (!refcount_is_zero(&rwl->rw_count))
+			cv_wait(&rwl->rw_cv, &rwl->rw_lock);
+		rwl->rw_writer = curthread;
+	}
+
+	(void) refcount_add(&rwl->rw_count, tag);
+
+	mutex_exit(&rwl->rw_lock);
+}
+
+void
+rprw_enter(rprwlock_t *rwl, krw_t rw, void *tag)
+{
+	if (rw == RW_READER)
+		rprw_enter_read(rwl, tag);
+	else
+		rprw_enter_write(rwl, tag);
+}
+
+void
+rprw_exit(rprwlock_t *rwl, void *tag)
+{
+	mutex_enter(&rwl->rw_lock);
+
+	ASSERT(!refcount_is_zero(&rwl->rw_count));
+	ASSERT(rwl->rw_writer == NULL || curthread == rwl->rw_writer);
+	if (refcount_remove(&rwl->rw_count, tag) == 0) {
+		cv_broadcast(&rwl->rw_cv);
+		rwl->rw_writer = NULL;  /* OK in either case */
+	}
+
+	mutex_exit(&rwl->rw_lock);
+}
+
+boolean_t
+rprw_held(rprwlock_t *rwl, krw_t rw)
+{
+	boolean_t held;
+
+	mutex_enter(&rwl->rw_lock);
+	if (rw == RW_WRITER)
+		held = (rwl->rw_writer == curthread);
+	else
+		held = !rwl->rw_writer && !refcount_is_zero(&rwl->rw_count);
+	mutex_exit(&rwl->rw_lock);
+
+	return (held);
+}