drivers/acpica/utlock.c

0001 /******************************************************************************
0002  *
0003  * Module Name: utlock - Reader/Writer lock interfaces
0004  *
0005  *****************************************************************************/
0006
0007 /******************************************************************************
0008  *
0009  * 1. Copyright Notice
0010  *
0011  * Some or all of this work - Copyright (c) 1999 - 2009, Intel Corp.
0012  * All rights reserved.
0013  *
0014  * 2. License
0015  *
0016  * 2.1. This is your license from Intel Corp. under its intellectual property
0017  * rights.  You may have additional license terms from the party that provided
0018  * you this software, covering your right to use that party's intellectual
0019  * property rights.
0020  *
0021  * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
0022  * copy of the source code appearing in this file ("Covered Code") an
0023  * irrevocable, perpetual, worldwide license under Intel's copyrights in the
0024  * base code distributed originally by Intel ("Original Intel Code") to copy,
0025  * make derivatives, distribute, use and display any portion of the Covered
0026  * Code in any form, with the right to sublicense such rights; and
0027  *
0028  * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
0029  * license (with the right to sublicense), under only those claims of Intel
0030  * patents that are infringed by the Original Intel Code, to make, use, sell,
0031  * offer to sell, and import the Covered Code and derivative works thereof
0032  * solely to the minimum extent necessary to exercise the above copyright
0033  * license, and in no event shall the patent license extend to any additions
0034  * to or modifications of the Original Intel Code.  No other license or right
0035  * is granted directly or by implication, estoppel or otherwise;
0036  *
0037  * The above copyright and patent license is granted only if the following
0038  * conditions are met:
0039  *
0040  * 3. Conditions
0041  *
0042  * 3.1. Redistribution of Source with Rights to Further Distribute Source.
0043  * Redistribution of source code of any substantial portion of the Covered
0044  * Code or modification with rights to further distribute source must include
0045  * the above Copyright Notice, the above License, this list of Conditions,
0046  * and the following Disclaimer and Export Compliance provision.  In addition,
0047  * Licensee must cause all Covered Code to which Licensee contributes to
0048  * contain a file documenting the changes Licensee made to create that Covered
0049  * Code and the date of any change.  Licensee must include in that file the
0050  * documentation of any changes made by any predecessor Licensee.  Licensee
0051  * must include a prominent statement that the modification is derived,
0052  * directly or indirectly, from Original Intel Code.
0053  *
0054  * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
0055  * Redistribution of source code of any substantial portion of the Covered
0056  * Code or modification without rights to further distribute source must
0057  * include the following Disclaimer and Export Compliance provision in the
0058  * documentation and/or other materials provided with distribution.  In
0059  * addition, Licensee may not authorize further sublicense of source of any
0060  * portion of the Covered Code, and must include terms to the effect that the
0061  * license from Licensee to its licensee is limited to the intellectual
0062  * property embodied in the software Licensee provides to its licensee, and
0063  * not to intellectual property embodied in modifications its licensee may
0064  * make.
0065  *
0066  * 3.3. Redistribution of Executable. Redistribution in executable form of any
0067  * substantial portion of the Covered Code or modification must reproduce the
0068  * above Copyright Notice, and the following Disclaimer and Export Compliance
0069  * provision in the documentation and/or other materials provided with the
0070  * distribution.
0071  *
0072  * 3.4. Intel retains all right, title, and interest in and to the Original
0073  * Intel Code.
0074  *
0075  * 3.5. Neither the name Intel nor any other trademark owned or controlled by
0076  * Intel shall be used in advertising or otherwise to promote the sale, use or
0077  * other dealings in products derived from or relating to the Covered Code
0078  * without prior written authorization from Intel.
0079  *
0080  * 4. Disclaimer and Export Compliance
0081  *
0082  * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
0083  * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
0084  * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
0085  * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
0086  * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
0087  * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
0088  * PARTICULAR PURPOSE.
0089  *
0090  * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
0091  * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
0092  * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
0093  * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
0094  * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
0095  * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
0096  * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
0097  * LIMITED REMEDY.
0098  *
0099  * 4.3. Licensee shall not export, either directly or indirectly, any of this
0100  * software or system incorporating such software without first obtaining any
0101  * required license or other approval from the U. S. Department of Commerce or
0102  * any other agency or department of the United States Government.  In the
0103  * event Licensee exports any such software from the United States or
0104  * re-exports any such software from a foreign destination, Licensee shall
0105  * ensure that the distribution and export/re-export of the software is in
0106  * compliance with all laws, regulations, orders, or other restrictions of the
0107  * U.S. Export Administration Regulations. Licensee agrees that neither it nor
0108  * any of its subsidiaries will export/re-export any technical data, process,
0109  * software, or service, directly or indirectly, to any country for which the
0110  * United States government or any agency thereof requires an export license,
0111  * other governmental approval, or letter of assurance, without first obtaining
0112  * such license, approval or letter.
0113  *
0114  *****************************************************************************/
0115
0116 #define __UTLOCK_C__
0117
0118 #include "acpi.h"
0119 #include "accommon.h"
0120
0121
0122 #define _COMPONENT          ACPI_UTILITIES
0123         ACPI_MODULE_NAME    ("utlock")
0124
0125
0126 /*******************************************************************************
0127  *
0128  * FUNCTION:    AcpiUtCreateRwLock
0129  *              AcpiUtDeleteRwLock
0130  *
0131  * PARAMETERS:  Lock                - Pointer to a valid RW lock
0132  *
0133  * RETURN:      Status
0134  *
0135  * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
0136  *
0137  ******************************************************************************/
0138
0139 ACPI_STATUS
0140 AcpiUtCreateRwLock (
0141     ACPI_RW_LOCK            *Lock)
0142 {
0143     ACPI_STATUS             Status;
0144
0145
0146     Lock->NumReaders = 0;
0147     Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
0148     if (ACPI_FAILURE (Status))
0149     {
0150         return (Status);
0151     }
0152
0153     Status = AcpiOsCreateMutex (&Lock->WriterMutex);
0154     return (Status);
0155 }
0156
0157
0158 void
0159 AcpiUtDeleteRwLock (
0160     ACPI_RW_LOCK            *Lock)
0161 {
0162
0163     AcpiOsDeleteMutex (Lock->ReaderMutex);
0164     AcpiOsDeleteMutex (Lock->WriterMutex);
0165
0166     Lock->NumReaders = 0;
0167     Lock->ReaderMutex = NULL;
0168     Lock->WriterMutex = NULL;
0169 }
0170
0171
0172 /*******************************************************************************
0173  *
0174  * FUNCTION:    AcpiUtAcquireReadLock
0175  *              AcpiUtReleaseReadLock
0176  *
0177  * PARAMETERS:  Lock                - Pointer to a valid RW lock
0178  *
0179  * RETURN:      Status
0180  *
0181  * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
0182  *              only the first reader acquires the write mutex. On release,
0183  *              only the last reader releases the write mutex. Although this
0184  *              algorithm can in theory starve writers, this should not be a
0185  *              problem with ACPICA since the subsystem is infrequently used
0186  *              in comparison to (for example) an I/O system.
0187  *
0188  ******************************************************************************/
0189
0190 ACPI_STATUS
0191 AcpiUtAcquireReadLock (
0192     ACPI_RW_LOCK            *Lock)
0193 {
0194     ACPI_STATUS             Status;
0195
0196
0197     Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
0198     if (ACPI_FAILURE (Status))
0199     {
0200         return (Status);
0201     }
0202
0203     /* Acquire the write lock only for the first reader */
0204
0205     Lock->NumReaders++;
0206     if (Lock->NumReaders == 1)
0207     {
0208         Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
0209     }
0210
0211     AcpiOsReleaseMutex (Lock->ReaderMutex);
0212     return (Status);
0213 }
0214
0215
0216 ACPI_STATUS
0217 AcpiUtReleaseReadLock (
0218     ACPI_RW_LOCK            *Lock)
0219 {
0220     ACPI_STATUS             Status;
0221
0222
0223     Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
0224     if (ACPI_FAILURE (Status))
0225     {
0226         return (Status);
0227     }
0228
0229     /* Release the write lock only for the very last reader */
0230
0231     Lock->NumReaders--;
0232     if (Lock->NumReaders == 0)
0233     {
0234         AcpiOsReleaseMutex (Lock->WriterMutex);
0235     }
0236
0237     AcpiOsReleaseMutex (Lock->ReaderMutex);
0238     return (Status);
0239 }
0240
0241
0242 /*******************************************************************************
0243  *
0244  * FUNCTION:    AcpiUtAcquireWriteLock
0245  *              AcpiUtReleaseWriteLock
0246  *
0247  * PARAMETERS:  Lock                - Pointer to a valid RW lock
0248  *
0249  * RETURN:      Status
0250  *
0251  * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
0252  *              release the writer mutex associated with the lock. Acquisition
0253  *              of the lock is fully exclusive and will block all readers and
0254  *              writers until it is released.
0255  *
0256  ******************************************************************************/
0257
0258 ACPI_STATUS
0259 AcpiUtAcquireWriteLock (
0260     ACPI_RW_LOCK            *Lock)
0261 {
0262     ACPI_STATUS             Status;
0263
0264
0265     Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
0266     return (Status);
0267 }
0268
0269
0270 void
0271 AcpiUtReleaseWriteLock (
0272     ACPI_RW_LOCK            *Lock)
0273 {
0274
0275     AcpiOsReleaseMutex (Lock->WriterMutex);
0276 }
0277