FreeBSD/Linux Kernel Cross Reference
sys/contrib/dev/acpica/components/utilities/utlock.c

     /******************************************************************************
      *
      * Module Name: utlock - Reader/Writer lock interfaces
      *
      *****************************************************************************/
     
     /******************************************************************************
      *
      * 1. Copyright Notice
     *
     * Some or all of this work - Copyright (c) 1999 - 2022, 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.
    *
    *****************************************************************************
    *
    * Alternatively, you may choose to be licensed under the terms of the
    * following license:
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    * 1. Redistributions of source code must retain the above copyright
    *    notice, this list of conditions, and the following disclaimer,
    *    without modification.
    * 2. Redistributions in binary form must reproduce at minimum a disclaimer
    *    substantially similar to the "NO WARRANTY" disclaimer below
    *    ("Disclaimer") and any redistribution must be conditioned upon
    *    including a substantially similar Disclaimer requirement for further
    *    binary redistribution.
    * 3. Neither the names of the above-listed copyright holders nor the names
    *    of any contributors may be used to endorse or promote products derived
    *    from this software without specific prior written permission.
    *
    * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    *
    * Alternatively, you may choose to be licensed under the terms of the
    * GNU General Public License ("GPL") version 2 as published by the Free
    * Software Foundation.
    *
    *****************************************************************************/
   
   #include <contrib/dev/acpica/include/acpi.h>
   #include <contrib/dev/acpica/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);
   }

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