rprwlock.c revision 91ebeef555ce7f899b6270a3c2df47b51f7ad59a
/*
* 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);
}