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
33 extern "C" {
34 #endif
35
36 #include <sys/inttypes.h>
37 #include <sys/zfs_context.h>
38 #include <sys/refcount.h>
39
40 /*
41 * A reader-writer lock implementation that allows re-entrant reads, but
42 * still gives writers priority on "new" reads.
43 *
44 * See rrwlock.c for more details about the implementation.
45 *
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
53 */
54 typedef struct rrwlock {
55 kmutex_t rr_lock;
56 kcondvar_t rr_cv;
57 kthread_t *rr_writer;
58 refcount_t rr_anon_rcount;
59 refcount_t rr_linked_rcount;
60 boolean_t rr_writer_wanted;
61 boolean_t rr_track_all;
62 } rrwlock_t;
63
64 /*
65 * 'tag' is used in reference counting tracking. The
66 * 'tag' must be the same in a rrw_enter() as in its
67 * corresponding rrw_exit().
68 */
69 void rrw_init(rrwlock_t *rrl, boolean_t track_all);
70 void rrw_destroy(rrwlock_t *rrl);
71 void rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag);
72 void rrw_enter_read(rrwlock_t *rrl, void *tag);
73 void rrw_enter_read_prio(rrwlock_t *rrl, void *tag);
74 void rrw_enter_write(rrwlock_t *rrl);
75 void rrw_exit(rrwlock_t *rrl, void *tag);
76 boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
77 void rrw_tsd_destroy(void *arg);
78
79 #define RRW_READ_HELD(x) rrw_held(x, RW_READER)
80 #define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER)
81 #define RRW_LOCK_HELD(x) \
82 (rrw_held(x, RW_WRITER) || rrw_held(x, RW_READER))
83
84 /*
85 * A reader-mostly lock implementation, tuning above reader-writer locks
86 * for hightly parallel read acquisitions, pessimizing write acquisitions.
87 *
88 * This should be a prime number. See comment in rrwlock.c near
89 * RRM_TD_LOCK() for details.
90 */
91 #define RRM_NUM_LOCKS 17
92 typedef struct rrmlock {
93 rrwlock_t locks[RRM_NUM_LOCKS];
94 } rrmlock_t;
95
96 void rrm_init(rrmlock_t *rrl, boolean_t track_all);
97 void rrm_destroy(rrmlock_t *rrl);
98 void rrm_enter(rrmlock_t *rrl, krw_t rw, void *tag);
99 void rrm_enter_read(rrmlock_t *rrl, void *tag);
100 void rrm_enter_write(rrmlock_t *rrl);
101 void rrm_exit(rrmlock_t *rrl, void *tag);
102 boolean_t rrm_held(rrmlock_t *rrl, krw_t rw);
103
104 #define RRM_READ_HELD(x) rrm_held(x, RW_READER)
105 #define RRM_WRITE_HELD(x) rrm_held(x, RW_WRITER)
106 #define RRM_LOCK_HELD(x) \
107 (rrm_held(x, RW_WRITER) || rrm_held(x, RW_READER))
108
109 #ifdef __cplusplus
110 }
111 #endif
112
113 #endif /* _SYS_RR_RW_LOCK_H */