utlock.c revision 306536 
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 <contrib/dev/acpica/include/acpi.h>
45#include <contrib/dev/acpica/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
65ACPI_STATUS
66AcpiUtCreateRwLock (
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
84void
85AcpiUtDeleteRwLock (
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
116ACPI_STATUS
117AcpiUtAcquireReadLock (
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
142ACPI_STATUS
143AcpiUtReleaseReadLock (
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
184ACPI_STATUS
185AcpiUtAcquireWriteLock (
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
196void
197AcpiUtReleaseWriteLock (
198    ACPI_RW_LOCK            *Lock)
199{
200
201    AcpiOsReleaseMutex (Lock->WriterMutex);
202}
203