1 /*
2  * This file and its contents are supplied under the terms of the
3  * Common Development and Distribution License ("CDDL"), version 1.0.
4  * You may only use this file in accordance with the terms of version
5  * 1.0 of the CDDL.
6  *
7  * A full copy of the text of the CDDL should have accompanied this
8  * source.  A copy of the CDDL is also available via the Internet at
9  * http://www.illumos.org/license/CDDL.
10  */
11 
12 /*
13  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
14  */
15 
16 /*
17  * rwlock(9f)
18  */
19 
20 /* This is the API we're emulating */
21 #include <sys/rwlock.h>
22 
23 #include <sys/errno.h>
24 #include <sys/debug.h>
25 #include <sys/param.h>
26 #include <sys/synch32.h>
27 #include <sys/thread.h>
28 
29 /* avoiding synch.h */
30 int	rwlock_init(lwp_rwlock_t *, int, void *);
31 int	rwlock_destroy(lwp_rwlock_t *);
32 int	rw_rdlock(lwp_rwlock_t *);
33 int	rw_wrlock(lwp_rwlock_t *);
34 int	rw_unlock(lwp_rwlock_t *);
35 int	rw_tryrdlock(lwp_rwlock_t *);
36 int	rw_trywrlock(lwp_rwlock_t *);
37 int	_rw_read_held(void *);
38 int	_rw_write_held(void *);
39 
40 /*ARGSUSED*/
41 void
42 rw_init(krwlock_t *rwlp, char *name, krw_type_t type, void *arg)
43 {
44 	(void) rwlock_init(&rwlp->rw_lock, USYNC_THREAD, NULL);
45 	rwlp->rw_owner = _KTHREAD_INVALID;
46 }
47 
48 void
49 rw_destroy(krwlock_t *rwlp)
50 {
51 	(void) rwlock_destroy(&rwlp->rw_lock);
52 	rwlp->rw_owner = _KTHREAD_INVALID;
53 }
54 
55 void
56 rw_enter(krwlock_t *rwlp, krw_t rw)
57 {
58 	int rc;
59 
60 	if (rw == RW_READER) {
61 		rc = rw_rdlock(&rwlp->rw_lock);
62 	} else {
63 		rc = rw_wrlock(&rwlp->rw_lock);
64 		rwlp->rw_owner = _curthread();
65 	}
66 	VERIFY(rc == 0);
67 }
68 
69 void
70 rw_exit(krwlock_t *rwlp)
71 {
72 	if (_rw_write_held(&rwlp->rw_lock)) {
73 		ASSERT(rwlp->rw_owner == _curthread());
74 		rwlp->rw_owner = _KTHREAD_INVALID;
75 	}
76 	(void) rw_unlock(&rwlp->rw_lock);
77 }
78 
79 int
80 rw_tryenter(krwlock_t *rwlp, krw_t rw)
81 {
82 	int rv;
83 
84 	if (rw == RW_WRITER) {
85 		rv = rw_trywrlock(&rwlp->rw_lock);
86 		if (rv == 0)
87 			rwlp->rw_owner = _curthread();
88 	} else
89 		rv = rw_tryrdlock(&rwlp->rw_lock);
90 
91 	return ((rv == 0) ? 1 : 0);
92 }
93 
94 /*ARGSUSED*/
95 int
96 rw_tryupgrade(krwlock_t *rwlp)
97 {
98 
99 	return (0);
100 }
101 
102 void
103 rw_downgrade(krwlock_t *rwlp)
104 {
105 	ASSERT(rwlp->rw_owner == _curthread());
106 	rwlp->rw_owner = _KTHREAD_INVALID;
107 	VERIFY(rw_unlock(&rwlp->rw_lock) == 0);
108 	VERIFY(rw_rdlock(&rwlp->rw_lock) == 0);
109 }
110 
111 int
112 rw_read_held(krwlock_t *rwlp)
113 {
114 	return (_rw_read_held(rwlp));
115 }
116 
117 int
118 rw_write_held(krwlock_t *rwlp)
119 {
120 	return (_rw_write_held(rwlp));
121 }
122 
123 int
124 rw_lock_held(krwlock_t *rwlp)
125 {
126 	return (rw_read_held(rwlp) || rw_write_held(rwlp));
127 }
128 
129 /*
130  * Return the kthread_t * of the lock owner
131  */
132 void *
133 rw_owner(krwlock_t *rwlp)
134 {
135 	return (rwlp->rw_owner);
136 }
137