drivers/acpi/utilities/utlock.c

   1 /******************************************************************************
   2  *
   3  * Module Name: utlock - Reader/Writer lock interfaces
   4  *
   5  *****************************************************************************/
   6
   7 /******************************************************************************
   8  *
   9  * 1. Copyright Notice
  10  *
  11  * Some or all of this work - Copyright (c) 1999 - 2010, Intel Corp.
  12  * All rights reserved.
  13  *
  14  * 2. License
  15  *
  16  * 2.1. This is your license from Intel Corp. under its intellectual property
  17  * rights.  You may have additional license terms from the party that provided
  18  * you this software, covering your right to use that party's intellectual
  19  * property rights.
  20  *
  21  * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
  22  * copy of the source code appearing in this file ("Covered Code") an
  23  * irrevocable, perpetual, worldwide license under Intel's copyrights in the
  24  * base code distributed originally by Intel ("Original Intel Code") to copy,
  25  * make derivatives, distribute, use and display any portion of the Covered
  26  * Code in any form, with the right to sublicense such rights; and
  27  *
  28  * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
  29  * license (with the right to sublicense), under only those claims of Intel
  30  * patents that are infringed by the Original Intel Code, to make, use, sell,
  31  * offer to sell, and import the Covered Code and derivative works thereof
  32  * solely to the minimum extent necessary to exercise the above copyright
  33  * license, and in no event shall the patent license extend to any additions
  34  * to or modifications of the Original Intel Code.  No other license or right
  35  * is granted directly or by implication, estoppel or otherwise;
  36  *
  37  * The above copyright and patent license is granted only if the following
  38  * conditions are met:
  39  *
  40  * 3. Conditions
  41  *
  42  * 3.1. Redistribution of Source with Rights to Further Distribute Source.
  43  * Redistribution of source code of any substantial portion of the Covered
  44  * Code or modification with rights to further distribute source must include
  45  * the above Copyright Notice, the above License, this list of Conditions,
  46  * and the following Disclaimer and Export Compliance provision.  In addition,
  47  * Licensee must cause all Covered Code to which Licensee contributes to
  48  * contain a file documenting the changes Licensee made to create that Covered
  49  * Code and the date of any change.  Licensee must include in that file the
  50  * documentation of any changes made by any predecessor Licensee.  Licensee
  51  * must include a prominent statement that the modification is derived,
  52  * directly or indirectly, from Original Intel Code.
  53  *
  54  * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
  55  * Redistribution of source code of any substantial portion of the Covered
  56  * Code or modification without rights to further distribute source must
  57  * include the following Disclaimer and Export Compliance provision in the
  58  * documentation and/or other materials provided with distribution.  In
  59  * addition, Licensee may not authorize further sublicense of source of any
  60  * portion of the Covered Code, and must include terms to the effect that the
  61  * license from Licensee to its licensee is limited to the intellectual
  62  * property embodied in the software Licensee provides to its licensee, and
  63  * not to intellectual property embodied in modifications its licensee may
  64  * make.
  65  *
  66  * 3.3. Redistribution of Executable. Redistribution in executable form of any
  67  * substantial portion of the Covered Code or modification must reproduce the
  68  * above Copyright Notice, and the following Disclaimer and Export Compliance
  69  * provision in the documentation and/or other materials provided with the
  70  * distribution.
  71  *
  72  * 3.4. Intel retains all right, title, and interest in and to the Original
  73  * Intel Code.
  74  *
  75  * 3.5. Neither the name Intel nor any other trademark owned or controlled by
  76  * Intel shall be used in advertising or otherwise to promote the sale, use or
  77  * other dealings in products derived from or relating to the Covered Code
  78  * without prior written authorization from Intel.
  79  *
  80  * 4. Disclaimer and Export Compliance
  81  *
  82  * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
  83  * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
  84  * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
  85  * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
  86  * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
  87  * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
  88  * PARTICULAR PURPOSE.
  89  *
  90  * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
  91  * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
  92  * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
  93  * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
  94  * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
  95  * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
  96  * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
  97  * LIMITED REMEDY.
  98  *
  99  * 4.3. Licensee shall not export, either directly or indirectly, any of this
 100  * software or system incorporating such software without first obtaining any
 101  * required license or other approval from the U. S. Department of Commerce or
 102  * any other agency or department of the United States Government.  In the
 103  * event Licensee exports any such software from the United States or
 104  * re-exports any such software from a foreign destination, Licensee shall
 105  * ensure that the distribution and export/re-export of the software is in
 106  * compliance with all laws, regulations, orders, or other restrictions of the
 107  * U.S. Export Administration Regulations. Licensee agrees that neither it nor
 108  * any of its subsidiaries will export/re-export any technical data, process,
 109  * software, or service, directly or indirectly, to any country for which the
 110  * United States government or any agency thereof requires an export license,
 111  * other governmental approval, or letter of assurance, without first obtaining
 112  * such license, approval or letter.
 113  *
 114  *****************************************************************************/
 115
 116 #define __UTLOCK_C__
 117
 118 #include "acpi.h"
 119 #include "accommon.h"
 120
 121
 122 #define _COMPONENT          ACPI_UTILITIES
 123         ACPI_MODULE_NAME    ("utlock")
 124
 125
 126 /*******************************************************************************
 127  *
 128  * FUNCTION:    AcpiUtCreateRwLock
 129  *              AcpiUtDeleteRwLock
 130  *
 131  * PARAMETERS:  Lock                - Pointer to a valid RW lock
 132  *
 133  * RETURN:      Status
 134  *
 135  * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
 136  *
 137  ******************************************************************************/
 138
 139 ACPI_STATUS
 140 AcpiUtCreateRwLock (
 141     ACPI_RW_LOCK            *Lock)
 142 {
 143     ACPI_STATUS             Status;
 144
 145
 146     Lock->NumReaders = 0;
 147     Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
 148     if (ACPI_FAILURE (Status))
 149     {
 150         return (Status);
 151     }
 152
 153     Status = AcpiOsCreateMutex (&Lock->WriterMutex);
 154     return (Status);
 155 }
 156
 157
 158 void
 159 AcpiUtDeleteRwLock (
 160     ACPI_RW_LOCK            *Lock)
 161 {
 162
 163     AcpiOsDeleteMutex (Lock->ReaderMutex);
 164     AcpiOsDeleteMutex (Lock->WriterMutex);
 165
 166     Lock->NumReaders = 0;
 167     Lock->ReaderMutex = NULL;
 168     Lock->WriterMutex = NULL;
 169 }
 170
 171
 172 /*******************************************************************************
 173  *
 174  * FUNCTION:    AcpiUtAcquireReadLock
 175  *              AcpiUtReleaseReadLock
 176  *
 177  * PARAMETERS:  Lock                - Pointer to a valid RW lock
 178  *
 179  * RETURN:      Status
 180  *
 181  * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
 182  *              only the first reader acquires the write mutex. On release,
 183  *              only the last reader releases the write mutex. Although this
 184  *              algorithm can in theory starve writers, this should not be a
 185  *              problem with ACPICA since the subsystem is infrequently used
 186  *              in comparison to (for example) an I/O system.
 187  *
 188  ******************************************************************************/
 189
 190 ACPI_STATUS
 191 AcpiUtAcquireReadLock (
 192     ACPI_RW_LOCK            *Lock)
 193 {
 194     ACPI_STATUS             Status;
 195
 196
 197     Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
 198     if (ACPI_FAILURE (Status))
 199     {
 200         return (Status);
 201     }
 202
 203     /* Acquire the write lock only for the first reader */
 204
 205     Lock->NumReaders++;
 206     if (Lock->NumReaders == 1)
 207     {
 208         Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
 209     }
 210
 211     AcpiOsReleaseMutex (Lock->ReaderMutex);
 212     return (Status);
 213 }
 214
 215
 216 ACPI_STATUS
 217 AcpiUtReleaseReadLock (
 218     ACPI_RW_LOCK            *Lock)
 219 {
 220     ACPI_STATUS             Status;
 221
 222
 223     Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
 224     if (ACPI_FAILURE (Status))
 225     {
 226         return (Status);
 227     }
 228
 229     /* Release the write lock only for the very last reader */
 230
 231     Lock->NumReaders--;
 232     if (Lock->NumReaders == 0)
 233     {
 234         AcpiOsReleaseMutex (Lock->WriterMutex);
 235     }
 236
 237     AcpiOsReleaseMutex (Lock->ReaderMutex);
 238     return (Status);
 239 }
 240
 241
 242 /*******************************************************************************
 243  *
 244  * FUNCTION:    AcpiUtAcquireWriteLock
 245  *              AcpiUtReleaseWriteLock
 246  *
 247  * PARAMETERS:  Lock                - Pointer to a valid RW lock
 248  *
 249  * RETURN:      Status
 250  *
 251  * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
 252  *              release the writer mutex associated with the lock. Acquisition
 253  *              of the lock is fully exclusive and will block all readers and
 254  *              writers until it is released.
 255  *
 256  ******************************************************************************/
 257
 258 ACPI_STATUS
 259 AcpiUtAcquireWriteLock (
 260     ACPI_RW_LOCK            *Lock)
 261 {
 262     ACPI_STATUS             Status;
 263
 264
 265     Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
 266     return (Status);
 267 }
 268
 269
 270 void
 271 AcpiUtReleaseWriteLock (
 272     ACPI_RW_LOCK            *Lock)
 273 {
 274
 275     AcpiOsReleaseMutex (Lock->WriterMutex);
 276 }
 277