utlock.c revision 231844 
1/******************************************************************************
2 *
3 * Module Name: utlock - Reader/Writer lock interfaces
4 *
5 *****************************************************************************/
6
7/*
8 * Copyright (C) 2000 - 2012, 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 <contrib/dev/acpica/include/acpi.h>
47#include <contrib/dev/acpica/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
67ACPI_STATUS
68AcpiUtCreateRwLock (
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
86void
87AcpiUtDeleteRwLock (
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
118ACPI_STATUS
119AcpiUtAcquireReadLock (
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
144ACPI_STATUS
145AcpiUtReleaseReadLock (
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
186ACPI_STATUS
187AcpiUtAcquireWriteLock (
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
198void
199AcpiUtReleaseWriteLock (
200    ACPI_RW_LOCK            *Lock)
201{
202
203    AcpiOsReleaseMutex (Lock->WriterMutex);
204}
205
206