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utlock.c revision 1.1.1.11 
      1 /******************************************************************************
      2  *
      3  * Module Name: utlock - Reader/Writer lock interfaces
      4  *
      5  *****************************************************************************/
      6 
      7 /*
      8  * Copyright (C) 2000 - 2021, 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 MERCHANTABILITY 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