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/******************************************************************************

 *

 * 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);

}