summaryrefslogtreecommitdiff
path: root/src/lib/rw_lock.c
blob: cf471e608f1accbdd0fea0f8c8e7030b675b3f2a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
/*
 * Ouroboros - Copyright (C) 2016
 *
 * Read/Write locks
 *
 *    Dimitri Staessens <dimitri.staessens@intec.ugent.be>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <ouroboros/rw_lock.h>

int rw_lock_init(rw_lock_t * lock)
{
        if (lock == NULL)
                return -1;

        pthread_mutex_init(&lock->lock, NULL);
        pthread_mutex_init(&lock->i_lock, NULL);
        lock->i = 0;

        return 0;
}

void rw_lock_destroy(rw_lock_t * lock)
{
        if (lock == NULL)
                return;

        pthread_mutex_destroy(&lock->lock);
        pthread_mutex_destroy(&lock->i_lock);
        lock->i = -1;
}

int rw_lock_rdlock(rw_lock_t * lock)
{
        int ret = 0;

        if (lock == NULL)
                return -1;

        pthread_mutex_lock(&lock->i_lock);

        if (lock->i < 0) {
                pthread_mutex_unlock(&lock->i_lock);
                return -1;
        }

        if (lock->i == 0)
                ret = pthread_mutex_lock(&lock->lock);

        ++(lock->i);

        pthread_mutex_unlock(&lock->i_lock);

        return ret;
}

int rw_lock_wrlock(rw_lock_t * lock)
{
        if (lock == NULL)
                return -1;

        pthread_mutex_lock(&lock->i_lock);

        if (lock->i < 0) {
                pthread_mutex_unlock(&lock->i_lock);
                return -1;
        }

        pthread_mutex_unlock(&lock->i_lock);

        while (1) {
                pthread_mutex_lock(&lock->i_lock);

                if (lock->i == 0) {
                        pthread_mutex_unlock(&lock->i_lock);
                        break;
                }

                pthread_mutex_unlock(&lock->i_lock);

                sched_yield();
        }

        ++(lock->i);

        return pthread_mutex_lock(&lock->lock);
}

int rw_lock_unlock(rw_lock_t * lock)
{
        int ret = 0;

        if (lock == NULL)
                return -1;

        pthread_mutex_lock(&lock->i_lock);

        if (lock->i < 0) {
                pthread_mutex_unlock(&lock->i_lock);
                return -1;
        }

        --(lock->i);

        if (lock->i == 0)
                ret = pthread_mutex_unlock(&lock->lock);

        pthread_mutex_unlock(&lock->i_lock);

        return ret;
}