1 /*
2    BAREOS® - Backup Archiving REcovery Open Sourced
3 
4    Copyright (C) 2001-2010 Free Software Foundation Europe e.V.
5    Copyright (C) 2016-2018 Bareos GmbH & Co. KG
6 
7    This program is Free Software; you can redistribute it and/or
8    modify it under the terms of version three of the GNU Affero General Public
9    License as published by the Free Software Foundation and included
10    in the file LICENSE.
11 
12    This program is distributed in the hope that it will be useful, but
13    WITHOUT ANY WARRANTY; without even the implied warranty of
14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15    Affero General Public License for more details.
16 
17    You should have received a copy of the GNU Affero General Public License
18    along with this program; if not, write to the Free Software
19    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
20    02110-1301, USA.
21 */
22 /*
23  * Kern Sibbald, January MMI
24  * This code adapted from "Programming with POSIX Threads", by David R. Butenhof
25  */
26 /**
27  * @file
28  * BAREOS Thread Read/Write locking code. It permits
29  * multiple readers but only one writer.
30  */
31 
32 #ifndef BAREOS_LIB_RWLOCK_H_
33 #define BAREOS_LIB_RWLOCK_H_ 1
34 
35 typedef struct s_rwlock_tag {
36   pthread_mutex_t mutex;
37   pthread_cond_t read;  /* wait for read */
38   pthread_cond_t write; /* wait for write */
39   pthread_t writer_id;  /* writer's thread id */
40   int priority;         /* used in deadlock detection */
41   int valid;            /* set when valid */
42   int r_active;         /* readers active */
43   int w_active;         /* writers active */
44   int r_wait;           /* readers waiting */
45   int w_wait;           /* writers waiting */
s_rwlock_tags_rwlock_tag46   s_rwlock_tag()
47   {
48     mutex = PTHREAD_MUTEX_INITIALIZER;
49     read = PTHREAD_COND_INITIALIZER;
50     write = PTHREAD_COND_INITIALIZER;
51     writer_id = 0;
52     priority = 0;
53     valid = 0;
54     r_active = 0;
55     w_active = 0;
56     r_wait = 0;
57     w_wait = 0;
58   };
59 } brwlock_t;
60 
61 #define RWLOCK_VALID 0xfacade
62 
63 #define RwlWritelock(x) RwlWritelock_p((x), __FILE__, __LINE__)
64 
65 /**
66  * read/write lock prototypes
67  */
68 extern int RwlInit(brwlock_t* rwl, int priority = 0);
69 extern int RwlDestroy(brwlock_t* rwl);
70 extern bool RwlIsInit(brwlock_t* rwl);
71 extern int RwlReadlock(brwlock_t* rwl);
72 extern int RwlReadtrylock(brwlock_t* rwl);
73 extern int RwlReadunlock(brwlock_t* rwl);
74 extern int RwlWritelock_p(brwlock_t* rwl,
75                           const char* file = "*unknown*",
76                           int line = 0);
77 extern int RwlWritetrylock(brwlock_t* rwl);
78 extern int RwlWriteunlock(brwlock_t* rwl);
79 
80 #endif /* BAREOS_LIB_RWLOCK_H_ */
81