1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
|
/******************************************************************************
*
* Module Name: utlock - Reader/Writer lock interfaces
*
*****************************************************************************/
/*
* Copyright (C) 2000 - 2010, Intel Corp.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce at minimum a disclaimer
* substantially similar to the "NO WARRANTY" disclaimer below
* ("Disclaimer") and any redistribution must be conditioned upon
* including a substantially similar Disclaimer requirement for further
* binary redistribution.
* 3. Neither the names of the above-listed copyright holders nor the names
* of any contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* NO WARRANTY
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*/
#include <acpi/acpi.h>
#include "accommon.h"
#define _COMPONENT ACPI_UTILITIES
ACPI_MODULE_NAME("utlock")
/*******************************************************************************
*
* FUNCTION: acpi_ut_create_rw_lock
* acpi_ut_delete_rw_lock
*
* PARAMETERS: Lock - Pointer to a valid RW lock
*
* RETURN: Status
*
* DESCRIPTION: Reader/writer lock creation and deletion interfaces.
*
******************************************************************************/
acpi_status acpi_ut_create_rw_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
lock->num_readers = 0;
status = acpi_os_create_mutex(&lock->reader_mutex);
if (ACPI_FAILURE(status)) {
return status;
}
status = acpi_os_create_mutex(&lock->writer_mutex);
return status;
}
void acpi_ut_delete_rw_lock(struct acpi_rw_lock *lock)
{
acpi_os_delete_mutex(lock->reader_mutex);
acpi_os_delete_mutex(lock->writer_mutex);
lock->num_readers = 0;
lock->reader_mutex = NULL;
lock->writer_mutex = NULL;
}
/*******************************************************************************
*
* FUNCTION: acpi_ut_acquire_read_lock
* acpi_ut_release_read_lock
*
* PARAMETERS: Lock - Pointer to a valid RW lock
*
* RETURN: Status
*
* DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
* only the first reader acquires the write mutex. On release,
* only the last reader releases the write mutex. Although this
* algorithm can in theory starve writers, this should not be a
* problem with ACPICA since the subsystem is infrequently used
* in comparison to (for example) an I/O system.
*
******************************************************************************/
acpi_status acpi_ut_acquire_read_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
if (ACPI_FAILURE(status)) {
return status;
}
/* Acquire the write lock only for the first reader */
lock->num_readers++;
if (lock->num_readers == 1) {
status =
acpi_os_acquire_mutex(lock->writer_mutex,
ACPI_WAIT_FOREVER);
}
acpi_os_release_mutex(lock->reader_mutex);
return status;
}
acpi_status acpi_ut_release_read_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
if (ACPI_FAILURE(status)) {
return status;
}
/* Release the write lock only for the very last reader */
lock->num_readers--;
if (lock->num_readers == 0) {
acpi_os_release_mutex(lock->writer_mutex);
}
acpi_os_release_mutex(lock->reader_mutex);
return status;
}
/*******************************************************************************
*
* FUNCTION: acpi_ut_acquire_write_lock
* acpi_ut_release_write_lock
*
* PARAMETERS: Lock - Pointer to a valid RW lock
*
* RETURN: Status
*
* DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
* release the writer mutex associated with the lock. Acquisition
* of the lock is fully exclusive and will block all readers and
* writers until it is released.
*
******************************************************************************/
acpi_status acpi_ut_acquire_write_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
status = acpi_os_acquire_mutex(lock->writer_mutex, ACPI_WAIT_FOREVER);
return status;
}
void acpi_ut_release_write_lock(struct acpi_rw_lock *lock)
{
acpi_os_release_mutex(lock->writer_mutex);
}
|
