2 * Bacula Thread Read/Write locking code. It permits
3 * multiple readers but only one writer.
5 * Kern Sibbald, January MMI
7 * This code adapted from "Programming with POSIX Threads", by
14 Bacula® - The Network Backup Solution
16 Copyright (C) 2001-2006 Free Software Foundation Europe e.V.
18 The main author of Bacula is Kern Sibbald, with contributions from
19 many others, a complete list can be found in the file AUTHORS.
20 This program is Free Software; you can redistribute it and/or
21 modify it under the terms of version two of the GNU General Public
22 License as published by the Free Software Foundation and included
25 This program is distributed in the hope that it will be useful, but
26 WITHOUT ANY WARRANTY; without even the implied warranty of
27 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
28 General Public License for more details.
30 You should have received a copy of the GNU General Public License
31 along with this program; if not, write to the Free Software
32 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
35 Bacula® is a registered trademark of Kern Sibbald.
36 The licensor of Bacula is the Free Software Foundation Europe
37 (FSFE), Fiduciary Program, Sumatrastrasse 25, 8006 Zürich,
38 Switzerland, email:ftf@fsfeurope.org.
44 typedef struct s_rwlock_tag {
45 pthread_mutex_t mutex;
46 pthread_cond_t read; /* wait for read */
47 pthread_cond_t write; /* wait for write */
48 pthread_t writer_id; /* writer's thread id */
49 int priority; /* used in deadlock detection */
50 int valid; /* set when valid */
51 int r_active; /* readers active */
52 int w_active; /* writers active */
53 int r_wait; /* readers waiting */
54 int w_wait; /* writers waiting */
57 typedef struct s_rwsteal_tag {
58 pthread_t writer_id; /* writer's thread id */
63 #define RWLOCK_VALID 0xfacade
65 #define RWL_INIIALIZER \
66 {PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, \
67 PTHREAD_COND_INITIALIZER, RWLOCK_VALID, 0, 0, 0, 0}
70 * read/write lock prototypes
72 extern int rwl_init(brwlock_t *wrlock, int priority=0);
73 extern int rwl_destroy(brwlock_t *rwlock);
74 extern int rwl_readlock(brwlock_t *rwlock);
75 extern int rwl_readtrylock(brwlock_t *rwlock);
76 extern int rwl_readunlock(brwlock_t *rwlock);
77 extern int rwl_writelock(brwlock_t *rwlock);
78 extern int rwl_writetrylock(brwlock_t *rwlock);
79 extern int rwl_writeunlock(brwlock_t *rwlock);
81 #endif /* __RWLOCK_H */