1 /******************************************************************************
2 *
3 * Module Name: utlock - Reader/Writer lock interfaces
4 *
5 *****************************************************************************/
6
7 /*
8 * Copyright (C) 2000 - 2011, 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 #define __UTLOCK_C__
45
46 #include "acpi.h"
47 #include "accommon.h"
48
49
50 #define _COMPONENT ACPI_UTILITIES
51 ACPI_MODULE_NAME ("utlock")
52
53
54 /*******************************************************************************
55 *
56 * FUNCTION: AcpiUtCreateRwLock
57 * AcpiUtDeleteRwLock
58 *
59 * PARAMETERS: Lock - Pointer to a valid RW lock
60 *
61 * RETURN: Status
62 *
63 * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
64 *
65 ******************************************************************************/
66
67 ACPI_STATUS
68 AcpiUtCreateRwLock (
69 ACPI_RW_LOCK *Lock)
70 {
71 ACPI_STATUS Status;
72
73
74 Lock->NumReaders = 0;
75 Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
76 if (ACPI_FAILURE (Status))
77 {
78 return (Status);
79 }
80
81 Status = AcpiOsCreateMutex (&Lock->WriterMutex);
82 return (Status);
83 }
84
85
86 void
87 AcpiUtDeleteRwLock (
88 ACPI_RW_LOCK *Lock)
89 {
90
91 AcpiOsDeleteMutex (Lock->ReaderMutex);
92 AcpiOsDeleteMutex (Lock->WriterMutex);
93
94 Lock->NumReaders = 0;
95 Lock->ReaderMutex = NULL;
96 Lock->WriterMutex = NULL;
97 }
98
99
100 /*******************************************************************************
101 *
102 * FUNCTION: AcpiUtAcquireReadLock
103 * AcpiUtReleaseReadLock
104 *
105 * PARAMETERS: Lock - Pointer to a valid RW lock
106 *
107 * RETURN: Status
108 *
109 * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
110 * only the first reader acquires the write mutex. On release,
111 * only the last reader releases the write mutex. Although this
112 * algorithm can in theory starve writers, this should not be a
113 * problem with ACPICA since the subsystem is infrequently used
114 * in comparison to (for example) an I/O system.
115 *
116 ******************************************************************************/
117
118 ACPI_STATUS
119 AcpiUtAcquireReadLock (
120 ACPI_RW_LOCK *Lock)
121 {
122 ACPI_STATUS Status;
123
124
125 Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
126 if (ACPI_FAILURE (Status))
127 {
128 return (Status);
129 }
130
131 /* Acquire the write lock only for the first reader */
132
133 Lock->NumReaders++;
134 if (Lock->NumReaders == 1)
135 {
136 Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
137 }
138
139 AcpiOsReleaseMutex (Lock->ReaderMutex);
140 return (Status);
141 }
142
143
144 ACPI_STATUS
145 AcpiUtReleaseReadLock (
146 ACPI_RW_LOCK *Lock)
147 {
148 ACPI_STATUS Status;
149
150
151 Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
152 if (ACPI_FAILURE (Status))
153 {
154 return (Status);
155 }
156
157 /* Release the write lock only for the very last reader */
158
159 Lock->NumReaders--;
160 if (Lock->NumReaders == 0)
161 {
162 AcpiOsReleaseMutex (Lock->WriterMutex);
163 }
164
165 AcpiOsReleaseMutex (Lock->ReaderMutex);
166 return (Status);
167 }
168
169
170 /*******************************************************************************
171 *
172 * FUNCTION: AcpiUtAcquireWriteLock
173 * AcpiUtReleaseWriteLock
174 *
175 * PARAMETERS: Lock - Pointer to a valid RW lock
176 *
177 * RETURN: Status
178 *
179 * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
180 * release the writer mutex associated with the lock. Acquisition
181 * of the lock is fully exclusive and will block all readers and
182 * writers until it is released.
183 *
184 ******************************************************************************/
185
186 ACPI_STATUS
187 AcpiUtAcquireWriteLock (
188 ACPI_RW_LOCK *Lock)
189 {
190 ACPI_STATUS Status;
191
192
193 Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
194 return (Status);
195 }
196
197
198 void
199 AcpiUtReleaseWriteLock (
200 ACPI_RW_LOCK *Lock)
201 {
202
203 AcpiOsReleaseMutex (Lock->WriterMutex);
204 }
205