1/*-
2 * Copyright (c) 2009-2011, Juniper Networks, Inc.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY JUNIPER NETWORKS AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL JUNIPER NETWORKS OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD$");
29
30static void
31filemon_filemon_lock(struct filemon *filemon)
32{
33	mtx_lock(&filemon->mtx);
34
35	while (filemon->locker != NULL && filemon->locker != curthread)
36		cv_wait(&filemon->cv, &filemon->mtx);
37
38	filemon->locker = curthread;
39
40	mtx_unlock(&filemon->mtx);
41}
42
43static void
44filemon_filemon_unlock(struct filemon *filemon)
45{
46	mtx_lock(&filemon->mtx);
47
48	if (filemon->locker == curthread)
49		filemon->locker = NULL;
50
51	/* Wake up threads waiting. */
52	cv_broadcast(&filemon->cv);
53
54	mtx_unlock(&filemon->mtx);
55}
56
57static void
58filemon_lock_read(void)
59{
60	mtx_lock(&access_mtx);
61
62	while (access_owner != NULL || access_requester != NULL)
63		cv_wait(&access_cv, &access_mtx);
64
65	n_readers++;
66
67	/* Wake up threads waiting. */
68	cv_broadcast(&access_cv);
69
70	mtx_unlock(&access_mtx);
71}
72
73static void
74filemon_unlock_read(void)
75{
76	mtx_lock(&access_mtx);
77
78	if (n_readers > 0)
79		n_readers--;
80
81	/* Wake up a thread waiting. */
82	cv_broadcast(&access_cv);
83
84	mtx_unlock(&access_mtx);
85}
86
87static void
88filemon_lock_write(void)
89{
90	mtx_lock(&access_mtx);
91
92	while (access_owner != curthread) {
93		if (access_owner == NULL &&
94		    (access_requester == NULL ||
95		    access_requester == curthread)) {
96			access_owner = curthread;
97			access_requester = NULL;
98		} else {
99			if (access_requester == NULL)
100				access_requester = curthread;
101
102			cv_wait(&access_cv, &access_mtx);
103		}
104	}
105
106	mtx_unlock(&access_mtx);
107}
108
109static void
110filemon_unlock_write(void)
111{
112	mtx_lock(&access_mtx);
113
114	/* Sanity check that the current thread actually has the write lock. */
115	if (access_owner == curthread)
116		access_owner = NULL;
117
118	/* Wake up a thread waiting. */
119	cv_broadcast(&access_cv);
120
121	mtx_unlock(&access_mtx);
122}
123