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