1/******************************************************************************
2 *
3 * Module Name: utlock - Reader/Writer lock interfaces
4 *
5 *****************************************************************************/
6
7/******************************************************************************
8 *
9 * 1. Copyright Notice
10 *
11 * Some or all of this work - Copyright (c) 1999 - 2009, Intel Corp.
12 * All rights reserved.
13 *
14 * 2. License
15 *
16 * 2.1. This is your license from Intel Corp. under its intellectual property
17 * rights.  You may have additional license terms from the party that provided
18 * you this software, covering your right to use that party's intellectual
19 * property rights.
20 *
21 * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
22 * copy of the source code appearing in this file ("Covered Code") an
23 * irrevocable, perpetual, worldwide license under Intel's copyrights in the
24 * base code distributed originally by Intel ("Original Intel Code") to copy,
25 * make derivatives, distribute, use and display any portion of the Covered
26 * Code in any form, with the right to sublicense such rights; and
27 *
28 * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
29 * license (with the right to sublicense), under only those claims of Intel
30 * patents that are infringed by the Original Intel Code, to make, use, sell,
31 * offer to sell, and import the Covered Code and derivative works thereof
32 * solely to the minimum extent necessary to exercise the above copyright
33 * license, and in no event shall the patent license extend to any additions
34 * to or modifications of the Original Intel Code.  No other license or right
35 * is granted directly or by implication, estoppel or otherwise;
36 *
37 * The above copyright and patent license is granted only if the following
38 * conditions are met:
39 *
40 * 3. Conditions
41 *
42 * 3.1. Redistribution of Source with Rights to Further Distribute Source.
43 * Redistribution of source code of any substantial portion of the Covered
44 * Code or modification with rights to further distribute source must include
45 * the above Copyright Notice, the above License, this list of Conditions,
46 * and the following Disclaimer and Export Compliance provision.  In addition,
47 * Licensee must cause all Covered Code to which Licensee contributes to
48 * contain a file documenting the changes Licensee made to create that Covered
49 * Code and the date of any change.  Licensee must include in that file the
50 * documentation of any changes made by any predecessor Licensee.  Licensee
51 * must include a prominent statement that the modification is derived,
52 * directly or indirectly, from Original Intel Code.
53 *
54 * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
55 * Redistribution of source code of any substantial portion of the Covered
56 * Code or modification without rights to further distribute source must
57 * include the following Disclaimer and Export Compliance provision in the
58 * documentation and/or other materials provided with distribution.  In
59 * addition, Licensee may not authorize further sublicense of source of any
60 * portion of the Covered Code, and must include terms to the effect that the
61 * license from Licensee to its licensee is limited to the intellectual
62 * property embodied in the software Licensee provides to its licensee, and
63 * not to intellectual property embodied in modifications its licensee may
64 * make.
65 *
66 * 3.3. Redistribution of Executable. Redistribution in executable form of any
67 * substantial portion of the Covered Code or modification must reproduce the
68 * above Copyright Notice, and the following Disclaimer and Export Compliance
69 * provision in the documentation and/or other materials provided with the
70 * distribution.
71 *
72 * 3.4. Intel retains all right, title, and interest in and to the Original
73 * Intel Code.
74 *
75 * 3.5. Neither the name Intel nor any other trademark owned or controlled by
76 * Intel shall be used in advertising or otherwise to promote the sale, use or
77 * other dealings in products derived from or relating to the Covered Code
78 * without prior written authorization from Intel.
79 *
80 * 4. Disclaimer and Export Compliance
81 *
82 * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
83 * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
84 * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
85 * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
86 * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
87 * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
88 * PARTICULAR PURPOSE.
89 *
90 * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
91 * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
92 * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
93 * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
94 * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
95 * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
96 * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
97 * LIMITED REMEDY.
98 *
99 * 4.3. Licensee shall not export, either directly or indirectly, any of this
100 * software or system incorporating such software without first obtaining any
101 * required license or other approval from the U. S. Department of Commerce or
102 * any other agency or department of the United States Government.  In the
103 * event Licensee exports any such software from the United States or
104 * re-exports any such software from a foreign destination, Licensee shall
105 * ensure that the distribution and export/re-export of the software is in
106 * compliance with all laws, regulations, orders, or other restrictions of the
107 * U.S. Export Administration Regulations. Licensee agrees that neither it nor
108 * any of its subsidiaries will export/re-export any technical data, process,
109 * software, or service, directly or indirectly, to any country for which the
110 * United States government or any agency thereof requires an export license,
111 * other governmental approval, or letter of assurance, without first obtaining
112 * such license, approval or letter.
113 *
114 *****************************************************************************/
115
116#define __UTLOCK_C__
117
118#include "acpi.h"
119#include "accommon.h"
120
121
122#define _COMPONENT          ACPI_UTILITIES
123        ACPI_MODULE_NAME    ("utlock")
124
125
126/*******************************************************************************
127 *
128 * FUNCTION:    AcpiUtCreateRwLock
129 *              AcpiUtDeleteRwLock
130 *
131 * PARAMETERS:  Lock                - Pointer to a valid RW lock
132 *
133 * RETURN:      Status
134 *
135 * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
136 *
137 ******************************************************************************/
138
139ACPI_STATUS
140AcpiUtCreateRwLock (
141    ACPI_RW_LOCK            *Lock)
142{
143    ACPI_STATUS             Status;
144
145
146    Lock->NumReaders = 0;
147    Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
148    if (ACPI_FAILURE (Status))
149    {
150        return (Status);
151    }
152
153    Status = AcpiOsCreateMutex (&Lock->WriterMutex);
154    return (Status);
155}
156
157
158void
159AcpiUtDeleteRwLock (
160    ACPI_RW_LOCK            *Lock)
161{
162
163    AcpiOsDeleteMutex (Lock->ReaderMutex);
164    AcpiOsDeleteMutex (Lock->WriterMutex);
165
166    Lock->NumReaders = 0;
167    Lock->ReaderMutex = NULL;
168    Lock->WriterMutex = NULL;
169}
170
171
172/*******************************************************************************
173 *
174 * FUNCTION:    AcpiUtAcquireReadLock
175 *              AcpiUtReleaseReadLock
176 *
177 * PARAMETERS:  Lock                - Pointer to a valid RW lock
178 *
179 * RETURN:      Status
180 *
181 * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
182 *              only the first reader acquires the write mutex. On release,
183 *              only the last reader releases the write mutex. Although this
184 *              algorithm can in theory starve writers, this should not be a
185 *              problem with ACPICA since the subsystem is infrequently used
186 *              in comparison to (for example) an I/O system.
187 *
188 ******************************************************************************/
189
190ACPI_STATUS
191AcpiUtAcquireReadLock (
192    ACPI_RW_LOCK            *Lock)
193{
194    ACPI_STATUS             Status;
195
196
197    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
198    if (ACPI_FAILURE (Status))
199    {
200        return (Status);
201    }
202
203    /* Acquire the write lock only for the first reader */
204
205    Lock->NumReaders++;
206    if (Lock->NumReaders == 1)
207    {
208        Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
209    }
210
211    AcpiOsReleaseMutex (Lock->ReaderMutex);
212    return (Status);
213}
214
215
216ACPI_STATUS
217AcpiUtReleaseReadLock (
218    ACPI_RW_LOCK            *Lock)
219{
220    ACPI_STATUS             Status;
221
222
223    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
224    if (ACPI_FAILURE (Status))
225    {
226        return (Status);
227    }
228
229    /* Release the write lock only for the very last reader */
230
231    Lock->NumReaders--;
232    if (Lock->NumReaders == 0)
233    {
234        AcpiOsReleaseMutex (Lock->WriterMutex);
235    }
236
237    AcpiOsReleaseMutex (Lock->ReaderMutex);
238    return (Status);
239}
240
241
242/*******************************************************************************
243 *
244 * FUNCTION:    AcpiUtAcquireWriteLock
245 *              AcpiUtReleaseWriteLock
246 *
247 * PARAMETERS:  Lock                - Pointer to a valid RW lock
248 *
249 * RETURN:      Status
250 *
251 * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
252 *              release the writer mutex associated with the lock. Acquisition
253 *              of the lock is fully exclusive and will block all readers and
254 *              writers until it is released.
255 *
256 ******************************************************************************/
257
258ACPI_STATUS
259AcpiUtAcquireWriteLock (
260    ACPI_RW_LOCK            *Lock)
261{
262    ACPI_STATUS             Status;
263
264
265    Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
266    return (Status);
267}
268
269
270void
271AcpiUtReleaseWriteLock (
272    ACPI_RW_LOCK            *Lock)
273{
274
275    AcpiOsReleaseMutex (Lock->WriterMutex);
276}
277
278