utlock.c

Go to the documentation of this file.

/******************************************************************************
 *
 * Module Name: utlock - Reader/Writer lock interfaces
 *
 *****************************************************************************/

/******************************************************************************
 *
 * 1. Copyright Notice
 *
 * Some or all of this work - Copyright (c) 1999 - 2011, Intel Corp.
 * All rights reserved.
 *
 * 2. License
 *
 * 2.1. This is your license from Intel Corp. under its intellectual property
 * rights.  You may have additional license terms from the party that provided
 * you this software, covering your right to use that party's intellectual
 * property rights.
 *
 * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
 * copy of the source code appearing in this file ("Covered Code") an
 * irrevocable, perpetual, worldwide license under Intel's copyrights in the
 * base code distributed originally by Intel ("Original Intel Code") to copy,
 * make derivatives, distribute, use and display any portion of the Covered
 * Code in any form, with the right to sublicense such rights; and
 *
 * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
 * license (with the right to sublicense), under only those claims of Intel
 * patents that are infringed by the Original Intel Code, to make, use, sell,
 * offer to sell, and import the Covered Code and derivative works thereof
 * solely to the minimum extent necessary to exercise the above copyright
 * license, and in no event shall the patent license extend to any additions
 * to or modifications of the Original Intel Code.  No other license or right
 * is granted directly or by implication, estoppel or otherwise;
 *
 * The above copyright and patent license is granted only if the following
 * conditions are met:
 *
 * 3. Conditions
 *
 * 3.1. Redistribution of Source with Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification with rights to further distribute source must include
 * the above Copyright Notice, the above License, this list of Conditions,
 * and the following Disclaimer and Export Compliance provision.  In addition,
 * Licensee must cause all Covered Code to which Licensee contributes to
 * contain a file documenting the changes Licensee made to create that Covered
 * Code and the date of any change.  Licensee must include in that file the
 * documentation of any changes made by any predecessor Licensee.  Licensee
 * must include a prominent statement that the modification is derived,
 * directly or indirectly, from Original Intel Code.
 *
 * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification without rights to further distribute source must
 * include the following Disclaimer and Export Compliance provision in the
 * documentation and/or other materials provided with distribution.  In
 * addition, Licensee may not authorize further sublicense of source of any
 * portion of the Covered Code, and must include terms to the effect that the
 * license from Licensee to its licensee is limited to the intellectual
 * property embodied in the software Licensee provides to its licensee, and
 * not to intellectual property embodied in modifications its licensee may
 * make.
 *
 * 3.3. Redistribution of Executable. Redistribution in executable form of any
 * substantial portion of the Covered Code or modification must reproduce the
 * above Copyright Notice, and the following Disclaimer and Export Compliance
 * provision in the documentation and/or other materials provided with the
 * distribution.
 *
 * 3.4. Intel retains all right, title, and interest in and to the Original
 * Intel Code.
 *
 * 3.5. Neither the name Intel nor any other trademark owned or controlled by
 * Intel shall be used in advertising or otherwise to promote the sale, use or
 * other dealings in products derived from or relating to the Covered Code
 * without prior written authorization from Intel.
 *
 * 4. Disclaimer and Export Compliance
 *
 * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
 * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
 * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
 * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
 * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
 * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
 * PARTICULAR PURPOSE.
 *
 * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
 * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
 * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
 * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
 * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
 * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
 * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
 * LIMITED REMEDY.
 *
 * 4.3. Licensee shall not export, either directly or indirectly, any of this
 * software or system incorporating such software without first obtaining any
 * required license or other approval from the U. S. Department of Commerce or
 * any other agency or department of the United States Government.  In the
 * event Licensee exports any such software from the United States or
 * re-exports any such software from a foreign destination, Licensee shall
 * ensure that the distribution and export/re-export of the software is in
 * compliance with all laws, regulations, orders, or other restrictions of the
 * U.S. Export Administration Regulations. Licensee agrees that neither it nor
 * any of its subsidiaries will export/re-export any technical data, process,
 * software, or service, directly or indirectly, to any country for which the
 * United States government or any agency thereof requires an export license,
 * other governmental approval, or letter of assurance, without first obtaining
 * such license, approval or letter.
 *
 *****************************************************************************/

#define __UTLOCK_C__

#include "acpi.h"
#include "accommon.h"


#define _COMPONENT          ACPI_UTILITIES
        ACPI_MODULE_NAME    ("utlock")


/*******************************************************************************
 *
 * FUNCTION:    AcpiUtCreateRwLock
 *              AcpiUtDeleteRwLock
 *
 * PARAMETERS:  Lock                - Pointer to a valid RW lock
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
 *
 ******************************************************************************/

ACPI_STATUS
AcpiUtCreateRwLock (
    ACPI_RW_LOCK            *Lock)
{
    ACPI_STATUS             Status;


    Lock->NumReaders = 0;
    Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    Status = AcpiOsCreateMutex (&Lock->WriterMutex);
    return (Status);
}


void
AcpiUtDeleteRwLock (
    ACPI_RW_LOCK            *Lock)
{

    AcpiOsDeleteMutex (Lock->ReaderMutex);
    AcpiOsDeleteMutex (Lock->WriterMutex);

    Lock->NumReaders = 0;
    Lock->ReaderMutex = NULL;
    Lock->WriterMutex = NULL;
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiUtAcquireReadLock
 *              AcpiUtReleaseReadLock
 *
 * 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
AcpiUtAcquireReadLock (
    ACPI_RW_LOCK            *Lock)
{
    ACPI_STATUS             Status;


    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    /* Acquire the write lock only for the first reader */

    Lock->NumReaders++;
    if (Lock->NumReaders == 1)
    {
        Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
    }

    AcpiOsReleaseMutex (Lock->ReaderMutex);
    return (Status);
}


ACPI_STATUS
AcpiUtReleaseReadLock (
    ACPI_RW_LOCK            *Lock)
{
    ACPI_STATUS             Status;


    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
    if (ACPI_FAILURE (Status))
    {
        return (Status);
    }

    /* Release the write lock only for the very last reader */

    Lock->NumReaders--;
    if (Lock->NumReaders == 0)
    {
        AcpiOsReleaseMutex (Lock->WriterMutex);
    }

    AcpiOsReleaseMutex (Lock->ReaderMutex);
    return (Status);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiUtAcquireWriteLock
 *              AcpiUtReleaseWriteLock
 *
 * 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
AcpiUtAcquireWriteLock (
    ACPI_RW_LOCK            *Lock)
{
    ACPI_STATUS             Status;


    Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
    return (Status);
}


void
AcpiUtReleaseWriteLock (
    ACPI_RW_LOCK            *Lock)
{

    AcpiOsReleaseMutex (Lock->WriterMutex);
}