| 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 "acpi.h" |
| 45 | #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 | |
| 65 | ACPI_STATUS |
| 66 | AcpiUtCreateRwLock ( |
| 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 | |
| 84 | void |
| 85 | AcpiUtDeleteRwLock ( |
| 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 | |
| 116 | ACPI_STATUS |
| 117 | AcpiUtAcquireReadLock ( |
| 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 | |
| 142 | ACPI_STATUS |
| 143 | AcpiUtReleaseReadLock ( |
| 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 | |
| 184 | ACPI_STATUS |
| 185 | AcpiUtAcquireWriteLock ( |
| 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 | |
| 196 | void |
| 197 | AcpiUtReleaseWriteLock ( |
| 198 | ACPI_RW_LOCK *Lock) |
| 199 | { |
| 200 | |
| 201 | AcpiOsReleaseMutex (Lock->WriterMutex); |
| 202 | } |
| 203 | |