source: trunk/libs/libsemaphore/semaphore.h @ 621

Last change on this file since 621 was 619, checked in by alain, 6 years ago

1) Fix a bug in KSH : after the "load" command,

the [ksh] prompt is now printed after completion
of the loaded application.

2) Fix a bug in vmm_handle_cow() : the copy-on-write

use now a hal_remote_memcpy() to replicate the page content.
File size: 5.0 KB
Line 
1/*
2 * pthread.h - User level <semaphore> library definition.
3 *
4 * Author     Alain Greiner (2016,2017,2018)
5 *
6 * Copyright (c) UPMC Sorbonne Universites
7 *
8 * This file is part of ALMOS-MKH.
9 *
10 * ALMOS-MKH is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; version 2.0 of the License.
13 *
14 * ALMOS-MKH is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
21 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24#ifndef _SEMAPHORE_H_
25#define _SEMAPHORE_H_
26
27//////////////////////////////////////////////////////////////////////////////////////////////
28//             POSIX unnamed semaphores related functions
29//
30// This synchonisation object allows several thread in a given process to share one
31// (or several) shared resource(s).
32// - The sem_wait() function allows a thread to take one resource and atomically
33//   decrement the semaphore count. If the count value is zero, the calling thread
34//   blocks and deschedules. It is unblocked by another thread when it becomes possible
35//   to make the decrement.
36// - the sem_post() functions allows a thread to release a resource and atomicalli
37//   increment the semaphore count.
38//////////////////////////////////////////////////////////////////////////////////////////////
39
40#include <shared_semaphore.h>
41
42/*********************************************************************************************
43 * This function initializes an unnamed semaphore.
44 * Initializing a semaphore that has already been initialized results in undefined behavior.
45 *********************************************************************************************
46 * @ sem         : [in]  pointer on semaphore.
47 * @ pshared     : [in]  unsupported => must be zero.
48 * @ count       : [in]  initial semaphore value.
49 * @ return 0 if success / return -1 if failure.
50 ********************************************************************************************/
51int sem_init( sem_t        * sem,
52              int            pshared,
53              unsigned int   count );
54
55/*********************************************************************************************
56 * This blocking function takes a semaphore. It decrements the semaphore pointed to by <sem>.
57 * If the semaphore's value is greater than zero, then the decrement proceeds, and the
58 * function returns immediately. If the semaphore currently has the value zero, the calling
59 * thread registers in the associated waiting queue, blocks and deschedules.
60 * It will be unblocked by another thread when it becomes possible to perform the decrement.
61 *********************************************************************************************
62 * @ sem         : [in]  pointer on semaphore.
63 * @ return 0 if success / return -1 if failure.
64 ********************************************************************************************/
65int sem_wait( sem_t * sem );
66
67/*********************************************************************************************
68 * This function releases a semaphore. It increments the semaphore pointed to by <sem>.
69 * If the semaphore's value consequently becomes greater than zero, then another thread
70 * blocked in a sem_wait() call will be woken up to try to take the semaphore.
71 *********************************************************************************************
72 * @ sem         : [in]  pointer on semaphore.
73 * @ return 0 if success / return -1 if failure.
74 ********************************************************************************************/
75int sem_post( sem_t * sem );
76
77/*********************************************************************************************
78 * This function destroys the semaphore pointed to by <sem>.
79 *********************************************************************************************
80 * @ sem         : [in]  pointer on semaphore.
81 * @ return 0 if success / return -1 if failure.
82 ********************************************************************************************/
83int sem_destroy( sem_t * sem );
84
85/*********************************************************************************************
86 * This function places the current value of the semaphore pointed to by <sem>
87 * into the integer pointed to by <sval>.
88 *********************************************************************************************
89 * @ sem         : [in]  pointer on semaphore.
90 * @ value       : [out] buffer for semaphore current value.
91 * @ return 0 if success / return -1 if failure.
92 ********************************************************************************************/
93int sem_getvalue( sem_t * sem,
94                  int   * value );
95
96
97#endif  // _SEMAPHORE_H_
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