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 - 2018, 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 * Alternatively, you may choose to be licensed under the terms of the
117 * following license:
118 *
119 * Redistribution and use in source and binary forms, with or without
120 * modification, are permitted provided that the following conditions
121 * are met:
122 * 1. Redistributions of source code must retain the above copyright
123 *    notice, this list of conditions, and the following disclaimer,
124 *    without modification.
125 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
126 *    substantially similar to the "NO WARRANTY" disclaimer below
127 *    ("Disclaimer") and any redistribution must be conditioned upon
128 *    including a substantially similar Disclaimer requirement for further
129 *    binary redistribution.
130 * 3. Neither the names of the above-listed copyright holders nor the names
131 *    of any contributors may be used to endorse or promote products derived
132 *    from this software without specific prior written permission.
133 *
134 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
135 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
136 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
137 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
138 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
139 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
140 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
141 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
142 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
143 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
144 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
145 *
146 * Alternatively, you may choose to be licensed under the terms of the
147 * GNU General Public License ("GPL") version 2 as published by the Free
148 * Software Foundation.
149 *
150 *****************************************************************************/
151
152#include "acpi.h"
153#include "accommon.h"
154
155
156#define _COMPONENT          ACPI_UTILITIES
157        ACPI_MODULE_NAME    ("utlock")
158
159
160/*******************************************************************************
161 *
162 * FUNCTION:    AcpiUtCreateRwLock
163 *              AcpiUtDeleteRwLock
164 *
165 * PARAMETERS:  Lock                - Pointer to a valid RW lock
166 *
167 * RETURN:      Status
168 *
169 * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
170 *
171 ******************************************************************************/
172
173ACPI_STATUS
174AcpiUtCreateRwLock (
175    ACPI_RW_LOCK            *Lock)
176{
177    ACPI_STATUS             Status;
178
179
180    Lock->NumReaders = 0;
181    Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
182    if (ACPI_FAILURE (Status))
183    {
184        return (Status);
185    }
186
187    Status = AcpiOsCreateMutex (&Lock->WriterMutex);
188    return (Status);
189}
190
191
192void
193AcpiUtDeleteRwLock (
194    ACPI_RW_LOCK            *Lock)
195{
196
197    AcpiOsDeleteMutex (Lock->ReaderMutex);
198    AcpiOsDeleteMutex (Lock->WriterMutex);
199
200    Lock->NumReaders = 0;
201    Lock->ReaderMutex = NULL;
202    Lock->WriterMutex = NULL;
203}
204
205
206/*******************************************************************************
207 *
208 * FUNCTION:    AcpiUtAcquireReadLock
209 *              AcpiUtReleaseReadLock
210 *
211 * PARAMETERS:  Lock                - Pointer to a valid RW lock
212 *
213 * RETURN:      Status
214 *
215 * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
216 *              only the first reader acquires the write mutex. On release,
217 *              only the last reader releases the write mutex. Although this
218 *              algorithm can in theory starve writers, this should not be a
219 *              problem with ACPICA since the subsystem is infrequently used
220 *              in comparison to (for example) an I/O system.
221 *
222 ******************************************************************************/
223
224ACPI_STATUS
225AcpiUtAcquireReadLock (
226    ACPI_RW_LOCK            *Lock)
227{
228    ACPI_STATUS             Status;
229
230
231    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
232    if (ACPI_FAILURE (Status))
233    {
234        return (Status);
235    }
236
237    /* Acquire the write lock only for the first reader */
238
239    Lock->NumReaders++;
240    if (Lock->NumReaders == 1)
241    {
242        Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
243    }
244
245    AcpiOsReleaseMutex (Lock->ReaderMutex);
246    return (Status);
247}
248
249
250ACPI_STATUS
251AcpiUtReleaseReadLock (
252    ACPI_RW_LOCK            *Lock)
253{
254    ACPI_STATUS             Status;
255
256
257    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
258    if (ACPI_FAILURE (Status))
259    {
260        return (Status);
261    }
262
263    /* Release the write lock only for the very last reader */
264
265    Lock->NumReaders--;
266    if (Lock->NumReaders == 0)
267    {
268        AcpiOsReleaseMutex (Lock->WriterMutex);
269    }
270
271    AcpiOsReleaseMutex (Lock->ReaderMutex);
272    return (Status);
273}
274
275
276/*******************************************************************************
277 *
278 * FUNCTION:    AcpiUtAcquireWriteLock
279 *              AcpiUtReleaseWriteLock
280 *
281 * PARAMETERS:  Lock                - Pointer to a valid RW lock
282 *
283 * RETURN:      Status
284 *
285 * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
286 *              release the writer mutex associated with the lock. Acquisition
287 *              of the lock is fully exclusive and will block all readers and
288 *              writers until it is released.
289 *
290 ******************************************************************************/
291
292ACPI_STATUS
293AcpiUtAcquireWriteLock (
294    ACPI_RW_LOCK            *Lock)
295{
296    ACPI_STATUS             Status;
297
298
299    Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
300    return (Status);
301}
302
303
304void
305AcpiUtReleaseWriteLock (
306    ACPI_RW_LOCK            *Lock)
307{
308
309    AcpiOsReleaseMutex (Lock->WriterMutex);
310}
311