source: trunk/kernel/libk/readlock.h @ 540

Last change on this file since 540 was 457, checked in by alain, 3 years ago

This version modifies the exec syscall and fixes a large number of small bugs.
The version number has been updated (0.1)

File size: 4.3 KB
Line 
1/*
2 * readlock.h - kernel readlock definition
3 *
4 * Author   Alain Greiner    (2016)
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-kernel; if not, write to the Free Software Foundation,
21 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24#ifndef _READLOCK_H_
25#define _READLOCK_H_
26
27#include <kernel_config.h>
28#include <hal_kernel_types.h>
29
30/*******************************************************************************************
31 * This structure defines a local readlock, that supports several simultaneous read
32 * accesses, but only one write access.
33 * - A reader does not take the exclusive ownership of the lock, but it must atomically
34 * increment the registered readers count in the readlock_t structure before starting
35 * access and decrement it when access is completed.
36 * - A writer must take exclusive ownership before access, and must wait completion
37 * of all current read access before starting its own access.
38 * TODO : add a "list" field to register a taken lock in the owner thread list.
39 ******************************************************************************************/
40
41/****     Forward declarations    ****/
42
43struct thread_s;
44
45/*******************************************************************************************
46 * This structure defines a local readlock.
47 ******************************************************************************************/
48
49typedef struct readlock_s
50{
51        volatile uint32_t   taken;             /*! state : free if zero / taken if non zero  */
52        volatile uint32_t   count;             /*! current number of readers                 */
53        struct thread_s   * owner;             /*! pointer on curent owner thread            */
54}
55readlock_t;
56
57/*******************************************************************************************
58 * This function initializes a local readlock.
59 *******************************************************************************************
60 * @ lock       : pointer on readlock
61 ******************************************************************************************/
62void readlock_init( readlock_t * lock );
63
64/*******************************************************************************************
65 * This function get access to a local readlock for a reader.
66 *******************************************************************************************
67 * @ lock       : pointer on readlock
68 ******************************************************************************************/
69void readlock_rd_lock( readlock_t * lock );
70
71/*******************************************************************************************
72 * This function get access to a local readlock for a writer.
73 *******************************************************************************************
74 * @ lock       : pointer on readlock
75 ******************************************************************************************/
76void readlock_wr_lock( readlock_t * lock );
77
78/*******************************************************************************************
79 * This function unlocks a local readlock for a reader.
80 *******************************************************************************************
81 * @ lock       : pointer on readlock
82 ******************************************************************************************/
83void readlock_rd_unlock( readlock_t * lock );
84
85/*******************************************************************************************
86 * This function unlocks a local readlock for a writer.
87 *******************************************************************************************
88 * @ lock       : pointer on readlock
89 ******************************************************************************************/
90void readlock_wr_unlock( readlock_t * lock );
91
92
93#endif  /* _READLOCK_H_ */
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