Revert "ARM: tegra: tegratab: dummy change"
[linux-2.6.git] / drivers / acpi / acpica / utlock.c
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 #include <acpi/acpi.h>
45 #include "accommon.h"
46
47 #define _COMPONENT          ACPI_UTILITIES
48 ACPI_MODULE_NAME("utlock")
49
50 /*******************************************************************************
51  *
52  * FUNCTION:    acpi_ut_create_rw_lock
53  *              acpi_ut_delete_rw_lock
54  *
55  * PARAMETERS:  Lock                - Pointer to a valid RW lock
56  *
57  * RETURN:      Status
58  *
59  * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
60  *
61  ******************************************************************************/
62 acpi_status acpi_ut_create_rw_lock(struct acpi_rw_lock *lock)
63 {
64         acpi_status status;
65
66         lock->num_readers = 0;
67         status = acpi_os_create_mutex(&lock->reader_mutex);
68         if (ACPI_FAILURE(status)) {
69                 return status;
70         }
71
72         status = acpi_os_create_mutex(&lock->writer_mutex);
73         return status;
74 }
75
76 void acpi_ut_delete_rw_lock(struct acpi_rw_lock *lock)
77 {
78
79         acpi_os_delete_mutex(lock->reader_mutex);
80         acpi_os_delete_mutex(lock->writer_mutex);
81
82         lock->num_readers = 0;
83         lock->reader_mutex = NULL;
84         lock->writer_mutex = NULL;
85 }
86
87 /*******************************************************************************
88  *
89  * FUNCTION:    acpi_ut_acquire_read_lock
90  *              acpi_ut_release_read_lock
91  *
92  * PARAMETERS:  Lock                - Pointer to a valid RW lock
93  *
94  * RETURN:      Status
95  *
96  * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
97  *              only the first reader acquires the write mutex. On release,
98  *              only the last reader releases the write mutex. Although this
99  *              algorithm can in theory starve writers, this should not be a
100  *              problem with ACPICA since the subsystem is infrequently used
101  *              in comparison to (for example) an I/O system.
102  *
103  ******************************************************************************/
104
105 acpi_status acpi_ut_acquire_read_lock(struct acpi_rw_lock *lock)
106 {
107         acpi_status status;
108
109         status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
110         if (ACPI_FAILURE(status)) {
111                 return status;
112         }
113
114         /* Acquire the write lock only for the first reader */
115
116         lock->num_readers++;
117         if (lock->num_readers == 1) {
118                 status =
119                     acpi_os_acquire_mutex(lock->writer_mutex,
120                                           ACPI_WAIT_FOREVER);
121         }
122
123         acpi_os_release_mutex(lock->reader_mutex);
124         return status;
125 }
126
127 acpi_status acpi_ut_release_read_lock(struct acpi_rw_lock *lock)
128 {
129         acpi_status status;
130
131         status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
132         if (ACPI_FAILURE(status)) {
133                 return status;
134         }
135
136         /* Release the write lock only for the very last reader */
137
138         lock->num_readers--;
139         if (lock->num_readers == 0) {
140                 acpi_os_release_mutex(lock->writer_mutex);
141         }
142
143         acpi_os_release_mutex(lock->reader_mutex);
144         return status;
145 }
146
147 /*******************************************************************************
148  *
149  * FUNCTION:    acpi_ut_acquire_write_lock
150  *              acpi_ut_release_write_lock
151  *
152  * PARAMETERS:  Lock                - Pointer to a valid RW lock
153  *
154  * RETURN:      Status
155  *
156  * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
157  *              release the writer mutex associated with the lock. Acquisition
158  *              of the lock is fully exclusive and will block all readers and
159  *              writers until it is released.
160  *
161  ******************************************************************************/
162
163 acpi_status acpi_ut_acquire_write_lock(struct acpi_rw_lock *lock)
164 {
165         acpi_status status;
166
167         status = acpi_os_acquire_mutex(lock->writer_mutex, ACPI_WAIT_FOREVER);
168         return status;
169 }
170
171 void acpi_ut_release_write_lock(struct acpi_rw_lock *lock)
172 {
173
174         acpi_os_release_mutex(lock->writer_mutex);
175 }