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 #include <limits.h>
21 #ifdef __USE_XOPEN2K
22 # define __need_timespec
23 # include <time.h>
24 #endif
25 
26 #ifndef _PTHREAD_DESCR_DEFINED
27 /* Thread descriptors.  Needed for `sem_t' definition.  */
28 typedef struct _pthread_descr_struct *_pthread_descr;
29 # define _PTHREAD_DESCR_DEFINED
30 #endif
31 
32 /* System specific semaphore definition.  */
33 typedef struct
34 {
35   struct _pthread_fastlock __sem_lock;
36   int __sem_value;
37   _pthread_descr __sem_waiting;
38 } sem_t;
39 
40 
41 
42 /* Value returned if `sem_open' failed.  */
43 #define SEM_FAILED	((sem_t *) 0)
44 
45 /* Maximum value the semaphore can have.  */
46 #ifndef SEM_VALUE_MAX
47 #define SEM_VALUE_MAX	((int) ((~0u) >> 1))
48 #endif
49 
50 
51 __BEGIN_DECLS
52 
53 /* Initialize semaphore object SEM to VALUE.  If PSHARED then share it
54    with other processes.  */
55 extern int sem_init (sem_t *__sem, int __pshared, unsigned int __value) __THROW;
56 
57 /* Free resources associated with semaphore object SEM.  */
58 extern int sem_destroy (sem_t *__sem) __THROW;
59 
60 /* Open a named semaphore NAME with open flags OFLAG.  */
61 extern sem_t *sem_open (const char *__name, int __oflag, ...) __THROW;
62 
63 /* Close descriptor for named semaphore SEM.  */
64 extern int sem_close (sem_t *__sem) __THROW;
65 
66 /* Remove named semaphore NAME.  */
67 extern int sem_unlink (const char *__name) __THROW;
68 
69 /* Wait for SEM being posted.
70 
71    This function is a cancellation point and therefore not marked with
72    __THROW.  */
73 extern int sem_wait (sem_t *__sem);
74 
75 #ifdef __USE_XOPEN2K
76 /* Similar to `sem_wait' but wait only until ABSTIME.
77 
78    This function is a cancellation point and therefore not marked with
79    __THROW.  */
80 extern int sem_timedwait (sem_t *__restrict __sem,
81 			  const struct timespec *__restrict __abstime);
82 #endif
83 
84 /* Test whether SEM is posted.  */
85 extern int sem_trywait (sem_t *__sem) __THROWNL;
86 
87 /* Post SEM.  */
88 extern int sem_post (sem_t *__sem) __THROWNL;
89 
90 /* Get current value of SEM and store it in *SVAL.  */
91 extern int sem_getvalue (sem_t *__restrict __sem, int *__restrict __sval)
92      __THROW;
93 
94 
95 __END_DECLS
96 
97 #endif	/* semaphore.h */
98