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1 | /****************************************************************************** |
2 | * | |
3 | * Module Name: utlock - Reader/Writer lock interfaces | |
4 | * | |
5 | *****************************************************************************/ | |
6 | ||
7 | /* | |
25f044e6 | 8 | * Copyright (C) 2000 - 2013, Intel Corp. |
8a335a23 BM |
9 | * All rights reserved. |
10 | * | |
11 | * Redistribution and use in source and binary forms, with or without | |
12 | * modification, are permitted provided that the following conditions | |
13 | * are met: | |
14 | * 1. Redistributions of source code must retain the above copyright | |
15 | * notice, this list of conditions, and the following disclaimer, | |
16 | * without modification. | |
17 | * 2. Redistributions in binary form must reproduce at minimum a disclaimer | |
18 | * substantially similar to the "NO WARRANTY" disclaimer below | |
19 | * ("Disclaimer") and any redistribution must be conditioned upon | |
20 | * including a substantially similar Disclaimer requirement for further | |
21 | * binary redistribution. | |
22 | * 3. Neither the names of the above-listed copyright holders nor the names | |
23 | * of any contributors may be used to endorse or promote products derived | |
24 | * from this software without specific prior written permission. | |
25 | * | |
26 | * Alternatively, this software may be distributed under the terms of the | |
27 | * GNU General Public License ("GPL") version 2 as published by the Free | |
28 | * Software Foundation. | |
29 | * | |
30 | * NO WARRANTY | |
31 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
32 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
33 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR | |
34 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
35 | * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
36 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
37 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
38 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |
39 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING | |
40 | * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
41 | * POSSIBILITY OF SUCH DAMAGES. | |
42 | */ | |
43 | ||
44 | #include <acpi/acpi.h> | |
45 | #include "accommon.h" | |
46 | ||
47 | #define _COMPONENT ACPI_UTILITIES | |
48 | ACPI_MODULE_NAME("utlock") | |
49 | ||
50 | /******************************************************************************* | |
51 | * | |
52 | * FUNCTION: acpi_ut_create_rw_lock | |
53 | * acpi_ut_delete_rw_lock | |
54 | * | |
ba494bee | 55 | * PARAMETERS: lock - Pointer to a valid RW lock |
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56 | * |
57 | * RETURN: Status | |
58 | * | |
59 | * DESCRIPTION: Reader/writer lock creation and deletion interfaces. | |
60 | * | |
61 | ******************************************************************************/ | |
62 | acpi_status acpi_ut_create_rw_lock(struct acpi_rw_lock *lock) | |
63 | { | |
64 | acpi_status status; | |
65 | ||
66 | lock->num_readers = 0; | |
67 | status = acpi_os_create_mutex(&lock->reader_mutex); | |
68 | if (ACPI_FAILURE(status)) { | |
9c0d7939 | 69 | return (status); |
8a335a23 BM |
70 | } |
71 | ||
72 | status = acpi_os_create_mutex(&lock->writer_mutex); | |
9c0d7939 | 73 | return (status); |
8a335a23 BM |
74 | } |
75 | ||
76 | void acpi_ut_delete_rw_lock(struct acpi_rw_lock *lock) | |
77 | { | |
78 | ||
79 | acpi_os_delete_mutex(lock->reader_mutex); | |
80 | acpi_os_delete_mutex(lock->writer_mutex); | |
81 | ||
82 | lock->num_readers = 0; | |
83 | lock->reader_mutex = NULL; | |
84 | lock->writer_mutex = NULL; | |
85 | } | |
86 | ||
87 | /******************************************************************************* | |
88 | * | |
89 | * FUNCTION: acpi_ut_acquire_read_lock | |
90 | * acpi_ut_release_read_lock | |
91 | * | |
ba494bee | 92 | * PARAMETERS: lock - Pointer to a valid RW lock |
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93 | * |
94 | * RETURN: Status | |
95 | * | |
96 | * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition, | |
97 | * only the first reader acquires the write mutex. On release, | |
98 | * only the last reader releases the write mutex. Although this | |
99 | * algorithm can in theory starve writers, this should not be a | |
100 | * problem with ACPICA since the subsystem is infrequently used | |
101 | * in comparison to (for example) an I/O system. | |
102 | * | |
103 | ******************************************************************************/ | |
104 | ||
105 | acpi_status acpi_ut_acquire_read_lock(struct acpi_rw_lock *lock) | |
106 | { | |
107 | acpi_status status; | |
108 | ||
109 | status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER); | |
110 | if (ACPI_FAILURE(status)) { | |
9c0d7939 | 111 | return (status); |
8a335a23 BM |
112 | } |
113 | ||
114 | /* Acquire the write lock only for the first reader */ | |
115 | ||
116 | lock->num_readers++; | |
117 | if (lock->num_readers == 1) { | |
118 | status = | |
119 | acpi_os_acquire_mutex(lock->writer_mutex, | |
120 | ACPI_WAIT_FOREVER); | |
121 | } | |
122 | ||
123 | acpi_os_release_mutex(lock->reader_mutex); | |
9c0d7939 | 124 | return (status); |
8a335a23 BM |
125 | } |
126 | ||
127 | acpi_status acpi_ut_release_read_lock(struct acpi_rw_lock *lock) | |
128 | { | |
129 | acpi_status status; | |
130 | ||
131 | status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER); | |
132 | if (ACPI_FAILURE(status)) { | |
9c0d7939 | 133 | return (status); |
8a335a23 BM |
134 | } |
135 | ||
136 | /* Release the write lock only for the very last reader */ | |
137 | ||
138 | lock->num_readers--; | |
139 | if (lock->num_readers == 0) { | |
140 | acpi_os_release_mutex(lock->writer_mutex); | |
141 | } | |
142 | ||
143 | acpi_os_release_mutex(lock->reader_mutex); | |
9c0d7939 | 144 | return (status); |
8a335a23 BM |
145 | } |
146 | ||
147 | /******************************************************************************* | |
148 | * | |
149 | * FUNCTION: acpi_ut_acquire_write_lock | |
150 | * acpi_ut_release_write_lock | |
151 | * | |
ba494bee | 152 | * PARAMETERS: lock - Pointer to a valid RW lock |
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153 | * |
154 | * RETURN: Status | |
155 | * | |
156 | * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or | |
157 | * release the writer mutex associated with the lock. Acquisition | |
158 | * of the lock is fully exclusive and will block all readers and | |
159 | * writers until it is released. | |
160 | * | |
161 | ******************************************************************************/ | |
162 | ||
163 | acpi_status acpi_ut_acquire_write_lock(struct acpi_rw_lock *lock) | |
164 | { | |
165 | acpi_status status; | |
166 | ||
167 | status = acpi_os_acquire_mutex(lock->writer_mutex, ACPI_WAIT_FOREVER); | |
9c0d7939 | 168 | return (status); |
8a335a23 BM |
169 | } |
170 | ||
171 | void acpi_ut_release_write_lock(struct acpi_rw_lock *lock) | |
172 | { | |
173 | ||
174 | acpi_os_release_mutex(lock->writer_mutex); | |
175 | } |