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/*
* 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.
*/
#ifndef _SYS_RR_RW_LOCK_H
#define _SYS_RR_RW_LOCK_H
#pragma ident "%Z%%M% %I% %E% SMI"
#ifdef __cplusplus
extern "C" {
#endif
#include <sys/zfs_context.h>
#include <sys/refcount.h>
/*
* A reader-writer lock implementation that allows re-entrant reads, but
* still gives writers priority on "new" reads.
*
* See rrwlock.c for more details about the implementation.
*
* Fields of the rrwlock_t structure:
* - rr_lock: protects modification and reading of rrwlock_t fields
* - rr_cv: cv for waking up readers or waiting writers
* - rr_writer: thread id of the current writer
* - rr_anon_rount: number of active anonymous readers
* - rr_linked_rcount: total number of non-anonymous active readers
* - rr_writer_wanted: a writer wants the lock
*/
typedef struct rrwlock {
kmutex_t rr_lock;
kcondvar_t rr_cv;
kthread_t *rr_writer;
refcount_t rr_anon_rcount;
refcount_t rr_linked_rcount;
boolean_t rr_writer_wanted;
} rrwlock_t;
/*
* 'tag' is used in reference counting tracking. The
* 'tag' must be the same in a rrw_enter() as in its
* corresponding rrw_exit().
*/
void rrw_init(rrwlock_t *rrl);
void rrw_destroy(rrwlock_t *rrl);
void rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag);
void rrw_exit(rrwlock_t *rrl, void *tag);
boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
#define RRW_READ_HELD(x) rrw_held(x, RW_READER)
#define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER)
#ifdef __cplusplus
}
#endif
#endif /* _SYS_RR_RW_LOCK_H */