1 /*
2 * Copyright (c) International Business Machines Corp., 2001-2004
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
12 * the GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18 #include <pthread.h>
19 #include <stdlib.h>
20 #include <stdio.h>
21
22 /* #define RWDEBUG 1 */
23 #include "config.h"
24 #include "rwlock.h"
25
init_rwlock(struct rwlock * rw)26 void init_rwlock(struct rwlock *rw)
27 {
28 rw->n_readers = 0;
29 pthread_mutex_init(&rw->plock, NULL);
30 pthread_cond_init(&rw->pcond, NULL);
31 #ifdef RWDEBUG
32 rw->n_write_waiting = 0;
33 rw->n_read_waiting = 0;
34 rw->writer_tid = -1;
35 #endif
36 }
37
rw_lock_read(struct rwlock * rw)38 void rw_lock_read(struct rwlock *rw)
39 {
40 pthread_mutex_lock(&rw->plock);
41 #ifdef RWDEBUG
42 rw->n_read_waiting++;
43 #endif
44 while (rw->n_readers < 0)
45 pthread_cond_wait(&rw->pcond, &rw->plock);
46 rw->n_readers++;
47 #ifdef RWDEBUG
48 rw->n_read_waiting--;
49 #endif
50 pthread_mutex_unlock(&rw->plock);
51 }
52
rw_lock_write(struct rwlock * rw)53 void rw_lock_write(struct rwlock *rw)
54 {
55 pthread_mutex_lock(&rw->plock);
56 #ifdef RWDEBUG
57 rw->n_write_waiting++;
58 #endif
59 while (rw->n_readers != 0)
60 pthread_cond_wait(&rw->pcond, &rw->plock);
61 rw->n_readers = -1;
62 #ifdef RWDEBUG
63 rw->n_write_waiting--;
64 rw->writer_tid = (int)pthread_self();
65 #endif
66 pthread_mutex_unlock(&rw->plock);
67
68 }
69
rw_unlock_read(struct rwlock * rw)70 void rw_unlock_read(struct rwlock *rw)
71 {
72 pthread_mutex_lock(&rw->plock);
73 rw->n_readers -= 1;
74 pthread_cond_signal(&rw->pcond);
75 pthread_mutex_unlock(&rw->plock);
76 }
77
rw_unlock_write(struct rwlock * rw)78 void rw_unlock_write(struct rwlock *rw)
79 {
80 pthread_mutex_lock(&rw->plock);
81 rw->n_readers = 0;
82 pthread_cond_broadcast(&rw->pcond);
83 pthread_mutex_unlock(&rw->plock);
84 }
85
rw_trylock_read(struct rwlock * rw)86 int rw_trylock_read(struct rwlock *rw)
87 {
88 int ret = 1;
89 pthread_mutex_lock(&rw->plock);
90 if (rw->n_readers >= 0) {
91 rw->n_readers++;
92 ret = 0;
93 }
94 pthread_mutex_unlock(&rw->plock);
95 return ret;
96 }
97
rw_trylock_write(struct rwlock * rw)98 int rw_trylock_write(struct rwlock *rw)
99 {
100 int ret = 1;
101 pthread_mutex_lock(&rw->plock);
102 if (rw->n_readers == 0) {
103 ret = 0;
104 rw->n_readers = -1;
105 }
106 pthread_mutex_unlock(&rw->plock);
107 return ret;
108 }
109