/*

 * 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);

}