drivers/bus/acpi/acpica/utilities/utlock.c

   1 /******************************************************************************
   2  *
   3  * Module Name: utlock - Reader/Writer lock interfaces
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2018, 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 }