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Diffstat (limited to 'drivers/acpi/acpica/utlock.c')
| -rw-r--r-- | drivers/acpi/acpica/utlock.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/drivers/acpi/acpica/utlock.c b/drivers/acpi/acpica/utlock.c new file mode 100644 index 000000000000..25e03120686d --- /dev/null +++ b/drivers/acpi/acpica/utlock.c @@ -0,0 +1,175 @@ +/****************************************************************************** + * + * Module Name: utlock - Reader/Writer lock interfaces + * + *****************************************************************************/ + +/* + * Copyright (C) 2000 - 2009, Intel Corp. + * All rights reserved. + * + * 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. + * + * Alternatively, this software may be distributed under the terms of the + * GNU General Public License ("GPL") version 2 as published by the Free + * Software Foundation. + * + * NO WARRANTY + * 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 MERCHANTIBILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * HOLDERS OR CONTRIBUTORS BE LIABLE FOR 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 DAMAGES. + */ + +#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); +} |