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// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
/******************************************************************************
*
* Module Name: utlock - Reader/Writer lock interfaces
*
* Copyright (C) 2000 - 2021, Intel Corp.
*
*****************************************************************************/
#include <acpi/acpi.h>
#include "accommon.h"
#define _COMPONENT ACPI_UTILITIES
ACPI_MODULE_NAME("utlock")
/*******************************************************************************
*
* FUNCTION: acpi_ut_create_rw_lock
* acpi_ut_delete_rw_lock
*
* PARAMETERS: lock - Pointer to a valid RW lock
*
* RETURN: Status
*
* DESCRIPTION: Reader/writer lock creation and deletion interfaces.
*
******************************************************************************/
acpi_status acpi_ut_create_rw_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
lock->num_readers = 0;
status = acpi_os_create_mutex(&lock->reader_mutex);
if (ACPI_FAILURE(status)) {
return (status);
}
status = acpi_os_create_mutex(&lock->writer_mutex);
return (status);
}
void acpi_ut_delete_rw_lock(struct acpi_rw_lock *lock)
{
acpi_os_delete_mutex(lock->reader_mutex);
acpi_os_delete_mutex(lock->writer_mutex);
lock->num_readers = 0;
lock->reader_mutex = NULL;
lock->writer_mutex = NULL;
}
/*******************************************************************************
*
* FUNCTION: acpi_ut_acquire_read_lock
* acpi_ut_release_read_lock
*
* 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 acpi_ut_acquire_read_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
if (ACPI_FAILURE(status)) {
return (status);
}
/* Acquire the write lock only for the first reader */
lock->num_readers++;
if (lock->num_readers == 1) {
status =
acpi_os_acquire_mutex(lock->writer_mutex,
ACPI_WAIT_FOREVER);
}
acpi_os_release_mutex(lock->reader_mutex);
return (status);
}
acpi_status acpi_ut_release_read_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
status = acpi_os_acquire_mutex(lock->reader_mutex, ACPI_WAIT_FOREVER);
if (ACPI_FAILURE(status)) {
return (status);
}
/* Release the write lock only for the very last reader */
lock->num_readers--;
if (lock->num_readers == 0) {
acpi_os_release_mutex(lock->writer_mutex);
}
acpi_os_release_mutex(lock->reader_mutex);
return (status);
}
/*******************************************************************************
*
* FUNCTION: acpi_ut_acquire_write_lock
* acpi_ut_release_write_lock
*
* 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 acpi_ut_acquire_write_lock(struct acpi_rw_lock *lock)
{
acpi_status status;
status = acpi_os_acquire_mutex(lock->writer_mutex, ACPI_WAIT_FOREVER);
return (status);
}
void acpi_ut_release_write_lock(struct acpi_rw_lock *lock)
{
acpi_os_release_mutex(lock->writer_mutex);
}
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