1 | /****************************************************************************** |
2 | * |
3 | * Module Name: utlock - Reader/Writer lock interfaces |
4 | * |
5 | *****************************************************************************/ |
6 | |
7 | /* |
8 | * Copyright (C) 2000 - 2016, Intel Corp. |
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.h" |
45 | #include "accommon.h" |
46 | |
47 | |
48 | #define _COMPONENT ACPI_UTILITIES |
49 | ACPI_MODULE_NAME ("utlock" ) |
50 | |
51 | |
52 | /******************************************************************************* |
53 | * |
54 | * FUNCTION: AcpiUtCreateRwLock |
55 | * AcpiUtDeleteRwLock |
56 | * |
57 | * PARAMETERS: Lock - Pointer to a valid RW lock |
58 | * |
59 | * RETURN: Status |
60 | * |
61 | * DESCRIPTION: Reader/writer lock creation and deletion interfaces. |
62 | * |
63 | ******************************************************************************/ |
64 | |
65 | ACPI_STATUS |
66 | AcpiUtCreateRwLock ( |
67 | ACPI_RW_LOCK *Lock) |
68 | { |
69 | ACPI_STATUS Status; |
70 | |
71 | |
72 | Lock->NumReaders = 0; |
73 | Status = AcpiOsCreateMutex (&Lock->ReaderMutex); |
74 | if (ACPI_FAILURE (Status)) |
75 | { |
76 | return (Status); |
77 | } |
78 | |
79 | Status = AcpiOsCreateMutex (&Lock->WriterMutex); |
80 | return (Status); |
81 | } |
82 | |
83 | |
84 | void |
85 | AcpiUtDeleteRwLock ( |
86 | ACPI_RW_LOCK *Lock) |
87 | { |
88 | |
89 | AcpiOsDeleteMutex (Lock->ReaderMutex); |
90 | AcpiOsDeleteMutex (Lock->WriterMutex); |
91 | |
92 | Lock->NumReaders = 0; |
93 | Lock->ReaderMutex = NULL; |
94 | Lock->WriterMutex = NULL; |
95 | } |
96 | |
97 | |
98 | /******************************************************************************* |
99 | * |
100 | * FUNCTION: AcpiUtAcquireReadLock |
101 | * AcpiUtReleaseReadLock |
102 | * |
103 | * PARAMETERS: Lock - Pointer to a valid RW lock |
104 | * |
105 | * RETURN: Status |
106 | * |
107 | * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition, |
108 | * only the first reader acquires the write mutex. On release, |
109 | * only the last reader releases the write mutex. Although this |
110 | * algorithm can in theory starve writers, this should not be a |
111 | * problem with ACPICA since the subsystem is infrequently used |
112 | * in comparison to (for example) an I/O system. |
113 | * |
114 | ******************************************************************************/ |
115 | |
116 | ACPI_STATUS |
117 | AcpiUtAcquireReadLock ( |
118 | ACPI_RW_LOCK *Lock) |
119 | { |
120 | ACPI_STATUS Status; |
121 | |
122 | |
123 | Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER); |
124 | if (ACPI_FAILURE (Status)) |
125 | { |
126 | return (Status); |
127 | } |
128 | |
129 | /* Acquire the write lock only for the first reader */ |
130 | |
131 | Lock->NumReaders++; |
132 | if (Lock->NumReaders == 1) |
133 | { |
134 | Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER); |
135 | } |
136 | |
137 | AcpiOsReleaseMutex (Lock->ReaderMutex); |
138 | return (Status); |
139 | } |
140 | |
141 | |
142 | ACPI_STATUS |
143 | AcpiUtReleaseReadLock ( |
144 | ACPI_RW_LOCK *Lock) |
145 | { |
146 | ACPI_STATUS Status; |
147 | |
148 | |
149 | Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER); |
150 | if (ACPI_FAILURE (Status)) |
151 | { |
152 | return (Status); |
153 | } |
154 | |
155 | /* Release the write lock only for the very last reader */ |
156 | |
157 | Lock->NumReaders--; |
158 | if (Lock->NumReaders == 0) |
159 | { |
160 | AcpiOsReleaseMutex (Lock->WriterMutex); |
161 | } |
162 | |
163 | AcpiOsReleaseMutex (Lock->ReaderMutex); |
164 | return (Status); |
165 | } |
166 | |
167 | |
168 | /******************************************************************************* |
169 | * |
170 | * FUNCTION: AcpiUtAcquireWriteLock |
171 | * AcpiUtReleaseWriteLock |
172 | * |
173 | * PARAMETERS: Lock - Pointer to a valid RW lock |
174 | * |
175 | * RETURN: Status |
176 | * |
177 | * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or |
178 | * release the writer mutex associated with the lock. Acquisition |
179 | * of the lock is fully exclusive and will block all readers and |
180 | * writers until it is released. |
181 | * |
182 | ******************************************************************************/ |
183 | |
184 | ACPI_STATUS |
185 | AcpiUtAcquireWriteLock ( |
186 | ACPI_RW_LOCK *Lock) |
187 | { |
188 | ACPI_STATUS Status; |
189 | |
190 | |
191 | Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER); |
192 | return (Status); |
193 | } |
194 | |
195 | |
196 | void |
197 | AcpiUtReleaseWriteLock ( |
198 | ACPI_RW_LOCK *Lock) |
199 | { |
200 | |
201 | AcpiOsReleaseMutex (Lock->WriterMutex); |
202 | } |
203 | |