1/*
2 * CDDL HEADER START
3 *
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.
7 *
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.
12 *
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]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25/*
26 * Copyright (c) 2012 by Delphix. All rights reserved.
27 */
28
29#ifndef _SYS_RR_RW_LOCK_H
30#define _SYS_RR_RW_LOCK_H
31
32#ifdef __cplusplus
33extern "C" {
34#endif
35
36#include <sys/zfs_context.h>
37#include <sys/refcount.h>
38
39/*
40 * A reader-writer lock implementation that allows re-entrant reads, but
41 * still gives writers priority on "new" reads.
42 *
43 * See rrwlock.c for more details about the implementation.
44 *
45 * Fields of the rrwlock_t structure:
46 * - rr_lock: protects modification and reading of rrwlock_t fields
47 * - rr_cv: cv for waking up readers or waiting writers
48 * - rr_writer: thread id of the current writer
49 * - rr_anon_rount: number of active anonymous readers
50 * - rr_linked_rcount: total number of non-anonymous active readers
51 * - rr_writer_wanted: a writer wants the lock
52 */
53typedef struct rrwlock {
54 kmutex_t rr_lock;
55 kcondvar_t rr_cv;
56 kthread_t *rr_writer;
57 refcount_t rr_anon_rcount;
58 refcount_t rr_linked_rcount;
59 boolean_t rr_writer_wanted;
60 boolean_t rr_track_all;
61} rrwlock_t;
62
63/*
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().
67 */
68void rrw_init(rrwlock_t *rrl, boolean_t track_all);
69void rrw_destroy(rrwlock_t *rrl);
70void rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag);
71void rrw_enter_read(rrwlock_t *rrl, void *tag);
72void rrw_enter_read_prio(rrwlock_t *rrl, void *tag);
73void rrw_enter_write(rrwlock_t *rrl);
74void rrw_exit(rrwlock_t *rrl, void *tag);
75boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
76void rrw_tsd_destroy(void *arg);
77
78#define RRW_READ_HELD(x) rrw_held(x, RW_READER)
79#define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER)
80#define RRW_LOCK_HELD(x) \
81 (rrw_held(x, RW_WRITER) || rrw_held(x, RW_READER))
82
83/*
84 * A reader-mostly lock implementation, tuning above reader-writer locks
85 * for hightly parallel read acquisitions, pessimizing write acquisitions.
86 *
87 * This should be a prime number. See comment in rrwlock.c near
88 * RRM_TD_LOCK() for details.
89 */
90#define RRM_NUM_LOCKS 17
91typedef struct rrmlock {
92 rrwlock_t locks[RRM_NUM_LOCKS];
93} rrmlock_t;
94
95void rrm_init(rrmlock_t *rrl, boolean_t track_all);
96void rrm_destroy(rrmlock_t *rrl);
97void rrm_enter(rrmlock_t *rrl, krw_t rw, void *tag);
98void rrm_enter_read(rrmlock_t *rrl, void *tag);
99void rrm_enter_write(rrmlock_t *rrl);
100void rrm_exit(rrmlock_t *rrl, void *tag);
101boolean_t rrm_held(rrmlock_t *rrl, krw_t rw);
102
103#define RRM_READ_HELD(x) rrm_held(x, RW_READER)
104#define RRM_WRITE_HELD(x) rrm_held(x, RW_WRITER)
105#define RRM_LOCK_HELD(x) \
106 (rrm_held(x, RW_WRITER) || rrm_held(x, RW_READER))
107
108#ifdef __cplusplus
109}
110#endif
111
112#endif /* _SYS_RR_RW_LOCK_H */
113