2008-11-20 20:01:55 +00:00
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/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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#ifndef _SYS_RR_RW_LOCK_H
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#define _SYS_RR_RW_LOCK_H
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2010-08-26 16:52:40 +00:00
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2008-11-20 20:01:55 +00:00
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <sys/inttypes.h>
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#include <sys/zfs_context.h>
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#include <sys/refcount.h>
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/*
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* A reader-writer lock implementation that allows re-entrant reads, but
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* still gives writers priority on "new" reads.
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*
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* See rrwlock.c for more details about the implementation.
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*
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* Fields of the rrwlock_t structure:
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* - rr_lock: protects modification and reading of rrwlock_t fields
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* - rr_cv: cv for waking up readers or waiting writers
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* - rr_writer: thread id of the current writer
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* - rr_anon_rount: number of active anonymous readers
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* - rr_linked_rcount: total number of non-anonymous active readers
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* - rr_writer_wanted: a writer wants the lock
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*/
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typedef struct rrwlock {
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kmutex_t rr_lock;
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kcondvar_t rr_cv;
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kthread_t *rr_writer;
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refcount_t rr_anon_rcount;
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refcount_t rr_linked_rcount;
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boolean_t rr_writer_wanted;
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} rrwlock_t;
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/*
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* 'tag' is used in reference counting tracking. The
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* 'tag' must be the same in a rrw_enter() as in its
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* corresponding rrw_exit().
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*/
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void rrw_init(rrwlock_t *rrl);
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void rrw_destroy(rrwlock_t *rrl);
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void rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag);
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void rrw_exit(rrwlock_t *rrl, void *tag);
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boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
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#define RRW_READ_HELD(x) rrw_held(x, RW_READER)
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#define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER)
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#ifdef __cplusplus
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}
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#endif
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#endif /* _SYS_RR_RW_LOCK_H */
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