--- /dev/null
+/******************************************************************************
+ *
+ * Module Name: utlock - Reader/Writer lock interfaces
+ *
+ *****************************************************************************/
+
+/*
+ * Copyright (C) 2000 - 2015, 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);
+}
Code Review / kvmfornfv.git / blobdiff