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
26void 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
38void 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
53void 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
70void 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
78void 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
86int 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
98int 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