xref: /freebsd/sys/contrib/openzfs/include/sys/rrwlock.h (revision a0b956f5ac5e0941f9e74e24c1c53e05ad061a38)
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 
33 
34 #ifdef	__cplusplus
35 extern "C" {
36 #endif
37 
38 #include <sys/inttypes.h>
39 #include <sys/zfs_context.h>
40 #include <sys/zfs_refcount.h>
41 
42 extern uint_t rrw_tsd_key;
43 
44 /*
45  * A reader-writer lock implementation that allows re-entrant reads, but
46  * still gives writers priority on "new" reads.
47  *
48  * See rrwlock.c for more details about the implementation.
49  *
50  * Fields of the rrwlock_t structure:
51  * - rr_lock: protects modification and reading of rrwlock_t fields
52  * - rr_cv: cv for waking up readers or waiting writers
53  * - rr_writer: thread id of the current writer
54  * - rr_anon_rount: number of active anonymous readers
55  * - rr_linked_rcount: total number of non-anonymous active readers
56  * - rr_writer_wanted: a writer wants the lock
57  */
58 typedef struct rrwlock {
59 	kmutex_t	rr_lock;
60 	kcondvar_t	rr_cv;
61 	kthread_t	*rr_writer;
62 	zfs_refcount_t	rr_anon_rcount;
63 	zfs_refcount_t	rr_linked_rcount;
64 	boolean_t	rr_writer_wanted;
65 	boolean_t	rr_track_all;
66 } rrwlock_t;
67 
68 /*
69  * 'tag' is used in reference counting tracking.  The
70  * 'tag' must be the same in a rrw_enter() as in its
71  * corresponding rrw_exit().
72  */
73 void rrw_init(rrwlock_t *rrl, boolean_t track_all);
74 void rrw_destroy(rrwlock_t *rrl);
75 void rrw_enter(rrwlock_t *rrl, krw_t rw, const void *tag);
76 void rrw_enter_read(rrwlock_t *rrl, const void *tag);
77 void rrw_enter_read_prio(rrwlock_t *rrl, const void *tag);
78 void rrw_enter_write(rrwlock_t *rrl);
79 void rrw_exit(rrwlock_t *rrl, const void *tag);
80 boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
81 void rrw_tsd_destroy(void *arg);
82 
83 #define	RRW_READ_HELD(x)	rrw_held(x, RW_READER)
84 #define	RRW_WRITE_HELD(x)	rrw_held(x, RW_WRITER)
85 #define	RRW_LOCK_HELD(x) \
86 	(rrw_held(x, RW_WRITER) || rrw_held(x, RW_READER))
87 
88 /*
89  * A reader-mostly lock implementation, tuning above reader-writer locks
90  * for hightly parallel read acquisitions, pessimizing write acquisitions.
91  *
92  * This should be a prime number.  See comment in rrwlock.c near
93  * RRM_TD_LOCK() for details.
94  */
95 #define	RRM_NUM_LOCKS		17
96 typedef struct rrmlock {
97 	rrwlock_t	locks[RRM_NUM_LOCKS];
98 } rrmlock_t;
99 
100 void rrm_init(rrmlock_t *rrl, boolean_t track_all);
101 void rrm_destroy(rrmlock_t *rrl);
102 void rrm_enter(rrmlock_t *rrl, krw_t rw, const void *tag);
103 void rrm_enter_read(rrmlock_t *rrl, const void *tag);
104 void rrm_enter_write(rrmlock_t *rrl);
105 void rrm_exit(rrmlock_t *rrl, const void *tag);
106 boolean_t rrm_held(rrmlock_t *rrl, krw_t rw);
107 
108 #define	RRM_READ_HELD(x)	rrm_held(x, RW_READER)
109 #define	RRM_WRITE_HELD(x)	rrm_held(x, RW_WRITER)
110 #define	RRM_LOCK_HELD(x) \
111 	(rrm_held(x, RW_WRITER) || rrm_held(x, RW_READER))
112 
113 #ifdef	__cplusplus
114 }
115 #endif
116 
117 #endif	/* _SYS_RR_RW_LOCK_H */
118