xref: /illumos-gate/usr/src/uts/common/fs/zfs/sys/rrwlock.h (revision e914ace2)
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 	zfs_refcount_t	rr_anon_rcount;
59 	zfs_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 */
114