xref: /freebsd/sys/contrib/openzfs/lib/libspl/rwlock.c (revision 8ac904ce090b1c2e355da8aa122ca2252183f4e1)

// SPDX-License-Identifier: CDDL-1.0
/*
 * 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 https://opensource.org/licenses/CDDL-1.0.
 * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
 * Copyright (c) 2016 Actifio, Inc. All rights reserved.
 * Copyright (c) 2025, Klara, Inc.
 */

#include <assert.h>
#include <pthread.h>
#include <errno.h>
#include <atomic.h>
#include <sys/rwlock.h>

/*
 * =========================================================================
 * rwlocks
 * =========================================================================
 */

void
rw_init(krwlock_t *rwlp, char *name, int type, void *arg)
{
	(void) name, (void) type, (void) arg;
	VERIFY0(pthread_rwlock_init(&rwlp->rw_lock, NULL));
	rwlp->rw_readers = 0;
	rwlp->rw_owner = 0;
}

void
rw_destroy(krwlock_t *rwlp)
{
	VERIFY0(pthread_rwlock_destroy(&rwlp->rw_lock));
}

void
rw_enter(krwlock_t *rwlp, krw_t rw)
{
	if (rw == RW_READER) {
		VERIFY0(pthread_rwlock_rdlock(&rwlp->rw_lock));
		atomic_inc_uint(&rwlp->rw_readers);
	} else {
		VERIFY0(pthread_rwlock_wrlock(&rwlp->rw_lock));
		rwlp->rw_owner = pthread_self();
	}
}

void
rw_exit(krwlock_t *rwlp)
{
	if (RW_READ_HELD(rwlp))
		atomic_dec_uint(&rwlp->rw_readers);
	else
		rwlp->rw_owner = 0;

	VERIFY0(pthread_rwlock_unlock(&rwlp->rw_lock));
}

int
rw_tryenter(krwlock_t *rwlp, krw_t rw)
{
	int error;

	if (rw == RW_READER)
		error = pthread_rwlock_tryrdlock(&rwlp->rw_lock);
	else
		error = pthread_rwlock_trywrlock(&rwlp->rw_lock);

	if (error == 0) {
		if (rw == RW_READER)
			atomic_inc_uint(&rwlp->rw_readers);
		else
			rwlp->rw_owner = pthread_self();

		return (1);
	}

	VERIFY3S(error, ==, EBUSY);

	return (0);
}

int
rw_tryupgrade(krwlock_t *rwlp)
{
	(void) rwlp;
	return (0);
}