4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
22 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
26 #ifndef _SYS_RR_RW_LOCK_H
27 #define _SYS_RR_RW_LOCK_H
29 #pragma ident "%Z%%M% %I% %E% SMI"
35 #include <sys/zfs_context.h>
36 #include <sys/refcount.h>
39 * A reader-writer lock implementation that allows re-entrant reads, but
40 * still gives writers priority on "new" reads.
42 * See rrwlock.c for more details about the implementation.
44 * Fields of the rrwlock_t structure:
45 * - rr_lock: protects modification and reading of rrwlock_t fields
46 * - rr_cv: cv for waking up readers or waiting writers
47 * - rr_writer: thread id of the current writer
48 * - rr_anon_rount: number of active anonymous readers
49 * - rr_linked_rcount: total number of non-anonymous active readers
50 * - rr_writer_wanted: a writer wants the lock
52 typedef struct rrwlock {
56 refcount_t rr_anon_rcount;
57 refcount_t rr_linked_rcount;
58 boolean_t rr_writer_wanted;
62 * 'tag' is used in reference counting tracking. The
63 * 'tag' must be the same in a rrw_enter() as in its
64 * corresponding rrw_exit().
66 void rrw_init(rrwlock_t *rrl);
67 void rrw_destroy(rrwlock_t *rrl);
68 void rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag);
69 void rrw_exit(rrwlock_t *rrl, void *tag);
70 boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
72 #define RRW_READ_HELD(x) rrw_held(x, RW_READER)
73 #define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER)
79 #endif /* _SYS_RR_RW_LOCK_H */