1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
2 /* threads for Linux.                                                   */
3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
4 /*                                                                      */
5 /* This program is free software; you can redistribute it and/or        */
6 /* modify it under the terms of the GNU Library General Public License  */
7 /* as published by the Free Software Foundation; either version 2       */
8 /* of the License, or (at your option) any later version.               */
9 /*                                                                      */
10 /* This program is distributed in the hope that it will be useful,      */
11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
13 /* GNU Library General Public License for more details.                 */
14 
15 #ifndef _SEMAPHORE_H
16 #define _SEMAPHORE_H	1
17 
18 #include <features.h>
19 #include <sys/types.h>
20 #ifdef __USE_XOPEN2K
21 # define __need_timespec
22 # include <time.h>
23 #endif
24 
25 #ifndef _PTHREAD_DESCR_DEFINED
26 /* Thread descriptors.  Needed for `sem_t' definition.  */
27 typedef struct pthread *_pthread_descr;
28 # define _PTHREAD_DESCR_DEFINED
29 #endif
30 
31 /* System specific semaphore definition.  */
32 typedef struct
33 {
34   struct _pthread_fastlock __sem_lock;
35   int __sem_value;
36   _pthread_descr __sem_waiting;
37 } sem_t;
38 
39 
40 
41 /* Value returned if `sem_open' failed.  */
42 #define SEM_FAILED	((sem_t *) 0)
43 
44 /* Maximum value the semaphore can have.  */
45 #define SEM_VALUE_MAX	(2147483647)
46 
47 
48 __BEGIN_DECLS
49 
50 /* Initialize semaphore object SEM to VALUE.  If PSHARED then share it
51    with other processes.  */
52 extern int sem_init (sem_t *__sem, int __pshared, unsigned int __value) __THROW;
53 
54 /* Free resources associated with semaphore object SEM.  */
55 extern int sem_destroy (sem_t *__sem) __THROW;
56 
57 /* Open a named semaphore NAME with open flags OFLAG.  */
58 extern sem_t *sem_open (__const char *__name, int __oflag, ...) __THROW;
59 
60 /* Close descriptor for named semaphore SEM.  */
61 extern int sem_close (sem_t *__sem) __THROW;
62 
63 /* Remove named semaphore NAME.  */
64 extern int sem_unlink (__const char *__name) __THROW;
65 
66 /* Wait for SEM being posted.
67 
68    This function is a cancellation point and therefore not marked with
69    __THROW.  */
70 extern int sem_wait (sem_t *__sem);
71 
72 #ifdef __USE_XOPEN2K
73 /* Similar to `sem_wait' but wait only until ABSTIME.
74 
75    This function is a cancellation point and therefore not marked with
76    __THROW.  */
77 extern int sem_timedwait (sem_t *__restrict __sem,
78 			  __const struct timespec *__restrict __abstime);
79 #endif
80 
81 /* Test whether SEM is posted.  */
82 extern int sem_trywait (sem_t *__sem) __THROW;
83 
84 /* Post SEM.  */
85 extern int sem_post (sem_t *__sem) __THROW;
86 
87 /* Get current value of SEM and store it in *SVAL.  */
88 extern int sem_getvalue (sem_t *__restrict __sem, int *__restrict __sval)
89      __THROW;
90 
91 
92 __END_DECLS
93 
94 #endif	/* semaphore.h */
95