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| Rev | Author | Line No. | Line |
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| 6595 | serge | 1 | /****************************************************************************** |
| 2 | * |
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| 3 | * Module Name: utlock - Reader/Writer lock interfaces |
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| 4 | * |
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| 5 | *****************************************************************************/ |
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| 6 | |||
| 7 | /* |
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| 8 | * Copyright (C) 2000 - 2015, Intel Corp. |
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| 9 | * All rights reserved. |
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| 10 | * |
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| 11 | * Redistribution and use in source and binary forms, with or without |
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| 12 | * modification, are permitted provided that the following conditions |
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| 13 | * are met: |
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| 14 | * 1. Redistributions of source code must retain the above copyright |
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| 15 | * notice, this list of conditions, and the following disclaimer, |
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| 16 | * without modification. |
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| 17 | * 2. Redistributions in binary form must reproduce at minimum a disclaimer |
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| 18 | * substantially similar to the "NO WARRANTY" disclaimer below |
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| 19 | * ("Disclaimer") and any redistribution must be conditioned upon |
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| 20 | * including a substantially similar Disclaimer requirement for further |
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| 21 | * binary redistribution. |
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| 22 | * 3. Neither the names of the above-listed copyright holders nor the names |
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| 23 | * of any contributors may be used to endorse or promote products derived |
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| 24 | * from this software without specific prior written permission. |
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| 25 | * |
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| 26 | * Alternatively, this software may be distributed under the terms of the |
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| 27 | * GNU General Public License ("GPL") version 2 as published by the Free |
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| 28 | * Software Foundation. |
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| 29 | * |
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| 30 | * NO WARRANTY |
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| 31 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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| 32 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| 33 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR |
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| 34 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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| 35 | * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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| 36 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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| 37 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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| 38 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
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| 39 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING |
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| 40 | * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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| 41 | * POSSIBILITY OF SUCH DAMAGES. |
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| 42 | */ |
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| 43 | |||
| 44 | #include |
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| 45 | #include "accommon.h" |
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| 46 | |||
| 47 | #define _COMPONENT ACPI_UTILITIES |
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| 48 | ACPI_MODULE_NAME("utlock") |
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| 49 | |||
| 50 | /******************************************************************************* |
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| 51 | * |
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| 52 | * FUNCTION: acpi_ut_create_rw_lock |
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| 53 | * acpi_ut_delete_rw_lock |
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| 54 | * |
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| 55 | * PARAMETERS: lock - Pointer to a valid RW lock |
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| 56 | * |
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| 57 | * RETURN: Status |
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| 58 | * |
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| 59 | * DESCRIPTION: Reader/writer lock creation and deletion interfaces. |
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| 60 | * |
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| 61 | ******************************************************************************/ |
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| 62 | acpi_status acpi_ut_create_rw_lock(struct acpi_rw_lock *lock) |
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| 63 | { |
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| 64 | acpi_status status; |
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| 65 | |||
| 66 | lock->num_readers = 0; |
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| 67 | status = acpi_os_create_mutex(&lock->reader_mutex); |
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| 68 | if (ACPI_FAILURE(status)) { |
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| 69 | return (status); |
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| 70 | } |
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| 71 | |||
| 72 | status = acpi_os_create_mutex(&lock->writer_mutex); |
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| 73 | return (status); |
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| 74 | } |
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| 75 | |||
| 76 | void acpi_ut_delete_rw_lock(struct acpi_rw_lock *lock) |
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| 77 | { |
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| 78 | |||
| 79 | acpi_os_delete_mutex(lock->reader_mutex); |
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| 80 | acpi_os_delete_mutex(lock->writer_mutex); |
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| 81 | |||
| 82 | lock->num_readers = 0; |
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| 83 | lock->reader_mutex = NULL; |
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| 84 | lock->writer_mutex = NULL; |
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| 85 | } |
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| 86 | |||
| 87 | /******************************************************************************* |
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| 88 | * |
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| 89 | * FUNCTION: acpi_ut_acquire_read_lock |
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| 90 | * acpi_ut_release_read_lock |
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| 91 | * |
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| 92 | * PARAMETERS: lock - Pointer to a valid RW lock |
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| 93 | * |
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| 94 | * RETURN: Status |
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| 95 | * |
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| 96 | * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition, |
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| 97 | * only the first reader acquires the write mutex. On release, |
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| 98 | * only the last reader releases the write mutex. Although this |
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| 99 | * algorithm can in theory starve writers, this should not be a |
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| 100 | * problem with ACPICA since the subsystem is infrequently used |
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| 101 | * in comparison to (for example) an I/O system. |
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| 102 | * |
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| 103 | ******************************************************************************/ |
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| 104 | |||
| 105 | acpi_status acpi_ut_acquire_read_lock(struct acpi_rw_lock *lock) |
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| 106 | { |
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| 107 | acpi_status status; |
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| 108 | |||
| 109 | status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER); |
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| 110 | if (ACPI_FAILURE(status)) { |
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| 111 | return (status); |
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| 112 | } |
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| 113 | |||
| 114 | /* Acquire the write lock only for the first reader */ |
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| 115 | |||
| 116 | lock->num_readers++; |
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| 117 | if (lock->num_readers == 1) { |
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| 118 | status = |
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| 119 | acpi_os_acquire_mutex(lock->writer_mutex, |
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| 120 | ACPI_WAIT_FOREVER); |
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| 121 | } |
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| 122 | |||
| 123 | acpi_os_release_mutex(lock->reader_mutex); |
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| 124 | return (status); |
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| 125 | } |
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| 126 | |||
| 127 | acpi_status acpi_ut_release_read_lock(struct acpi_rw_lock *lock) |
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| 128 | { |
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| 129 | acpi_status status; |
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| 130 | |||
| 131 | status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER); |
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| 132 | if (ACPI_FAILURE(status)) { |
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| 133 | return (status); |
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| 134 | } |
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| 135 | |||
| 136 | /* Release the write lock only for the very last reader */ |
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| 137 | |||
| 138 | lock->num_readers--; |
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| 139 | if (lock->num_readers == 0) { |
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| 140 | acpi_os_release_mutex(lock->writer_mutex); |
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| 141 | } |
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| 142 | |||
| 143 | acpi_os_release_mutex(lock->reader_mutex); |
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| 144 | return (status); |
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| 145 | } |
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| 146 | |||
| 147 | /******************************************************************************* |
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| 148 | * |
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| 149 | * FUNCTION: acpi_ut_acquire_write_lock |
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| 150 | * acpi_ut_release_write_lock |
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| 151 | * |
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| 152 | * PARAMETERS: lock - Pointer to a valid RW lock |
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| 153 | * |
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| 154 | * RETURN: Status |
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| 155 | * |
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| 156 | * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or |
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| 157 | * release the writer mutex associated with the lock. Acquisition |
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| 158 | * of the lock is fully exclusive and will block all readers and |
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| 159 | * writers until it is released. |
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| 160 | * |
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| 161 | ******************************************************************************/ |
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| 162 | |||
| 163 | acpi_status acpi_ut_acquire_write_lock(struct acpi_rw_lock *lock) |
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| 164 | { |
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| 165 | acpi_status status; |
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| 166 | |||
| 167 | status = acpi_os_acquire_mutex(lock->writer_mutex, ACPI_WAIT_FOREVER); |
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| 168 | return (status); |
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| 169 | } |
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| 170 | |||
| 171 | void acpi_ut_release_write_lock(struct acpi_rw_lock *lock) |
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| 172 | { |
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| 173 | |||
| 174 | acpi_os_release_mutex(lock->writer_mutex); |
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| 175 | } |