| // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 |
| /****************************************************************************** |
| * |
| * Module Name: utlock - Reader/Writer lock interfaces |
| * |
| * Copyright (C) 2000 - 2022, 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); |
| } |