142 lines
3.9 KiB
C
142 lines
3.9 KiB
C
// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
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/******************************************************************************
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*
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* Module Name: utlock - Reader/Writer lock interfaces
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*
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* Copyright (C) 2000 - 2019, Intel Corp.
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*
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*****************************************************************************/
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#include <acpi/acpi.h>
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#include "accommon.h"
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#define _COMPONENT ACPI_UTILITIES
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ACPI_MODULE_NAME("utlock")
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/*******************************************************************************
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*
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* FUNCTION: acpi_ut_create_rw_lock
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* acpi_ut_delete_rw_lock
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*
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* PARAMETERS: lock - Pointer to a valid RW lock
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*
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* RETURN: Status
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*
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* DESCRIPTION: Reader/writer lock creation and deletion interfaces.
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*
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******************************************************************************/
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acpi_status acpi_ut_create_rw_lock(struct acpi_rw_lock *lock)
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{
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acpi_status status;
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lock->num_readers = 0;
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status = acpi_os_create_mutex(&lock->reader_mutex);
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if (ACPI_FAILURE(status)) {
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return (status);
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}
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status = acpi_os_create_mutex(&lock->writer_mutex);
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return (status);
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}
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void acpi_ut_delete_rw_lock(struct acpi_rw_lock *lock)
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{
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acpi_os_delete_mutex(lock->reader_mutex);
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acpi_os_delete_mutex(lock->writer_mutex);
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lock->num_readers = 0;
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lock->reader_mutex = NULL;
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lock->writer_mutex = NULL;
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}
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/*******************************************************************************
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*
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* FUNCTION: acpi_ut_acquire_read_lock
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* acpi_ut_release_read_lock
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*
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* PARAMETERS: lock - Pointer to a valid RW lock
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*
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* RETURN: Status
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*
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* DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
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* only the first reader acquires the write mutex. On release,
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* only the last reader releases the write mutex. Although this
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* algorithm can in theory starve writers, this should not be a
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* problem with ACPICA since the subsystem is infrequently used
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* in comparison to (for example) an I/O system.
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*
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******************************************************************************/
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acpi_status acpi_ut_acquire_read_lock(struct acpi_rw_lock *lock)
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{
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acpi_status status;
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status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
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if (ACPI_FAILURE(status)) {
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return (status);
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}
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/* Acquire the write lock only for the first reader */
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lock->num_readers++;
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if (lock->num_readers == 1) {
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status =
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acpi_os_acquire_mutex(lock->writer_mutex,
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ACPI_WAIT_FOREVER);
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}
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acpi_os_release_mutex(lock->reader_mutex);
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return (status);
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}
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acpi_status acpi_ut_release_read_lock(struct acpi_rw_lock *lock)
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{
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acpi_status status;
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status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
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if (ACPI_FAILURE(status)) {
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return (status);
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}
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/* Release the write lock only for the very last reader */
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lock->num_readers--;
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if (lock->num_readers == 0) {
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acpi_os_release_mutex(lock->writer_mutex);
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}
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acpi_os_release_mutex(lock->reader_mutex);
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return (status);
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}
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/*******************************************************************************
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*
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* FUNCTION: acpi_ut_acquire_write_lock
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* acpi_ut_release_write_lock
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*
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* PARAMETERS: lock - Pointer to a valid RW lock
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*
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* RETURN: Status
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*
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* DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
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* release the writer mutex associated with the lock. Acquisition
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* of the lock is fully exclusive and will block all readers and
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* writers until it is released.
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*
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******************************************************************************/
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acpi_status acpi_ut_acquire_write_lock(struct acpi_rw_lock *lock)
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{
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acpi_status status;
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status = acpi_os_acquire_mutex(lock->writer_mutex, ACPI_WAIT_FOREVER);
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return (status);
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}
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void acpi_ut_release_write_lock(struct acpi_rw_lock *lock)
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{
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acpi_os_release_mutex(lock->writer_mutex);
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}
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