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 * Copyright (c) 2012 by Delphix. All rights reserved.
29 #ifndef _SYS_RR_RW_LOCK_H
30 #define _SYS_RR_RW_LOCK_H
36 #include <sys/inttypes.h>
37 #include <sys/zfs_context.h>
38 #include <sys/refcount.h>
41 * A reader-writer lock implementation that allows re-entrant reads, but
42 * still gives writers priority on "new" reads.
44 * See rrwlock.c for more details about the implementation.
46 * Fields of the rrwlock_t structure:
47 * - rr_lock: protects modification and reading of rrwlock_t fields
48 * - rr_cv: cv for waking up readers or waiting writers
49 * - rr_writer: thread id of the current writer
50 * - rr_anon_rount: number of active anonymous readers
51 * - rr_linked_rcount: total number of non-anonymous active readers
52 * - rr_writer_wanted: a writer wants the lock
54 typedef struct rrwlock
{
58 refcount_t rr_anon_rcount
;
59 refcount_t rr_linked_rcount
;
60 boolean_t rr_writer_wanted
;
64 * 'tag' is used in reference counting tracking. The
65 * 'tag' must be the same in a rrw_enter() as in its
66 * corresponding rrw_exit().
68 void rrw_init(rrwlock_t
*rrl
);
69 void rrw_destroy(rrwlock_t
*rrl
);
70 void rrw_enter(rrwlock_t
*rrl
, krw_t rw
, void *tag
);
71 void rrw_exit(rrwlock_t
*rrl
, void *tag
);
72 boolean_t
rrw_held(rrwlock_t
*rrl
, krw_t rw
);
73 void rrw_tsd_destroy(void *arg
);
75 #define RRW_READ_HELD(x) rrw_held(x, RW_READER)
76 #define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER)
82 #endif /* _SYS_RR_RW_LOCK_H */