/******************************************************************************
 *
 * Module Name: dsmethod - Parser/Interpreter interface - control method parsing
 *
 *****************************************************************************/

/*
 * 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"
#include "acdispat.h"
#include "acinterp.h"
#include "acnamesp.h"
#ifdef  ACPI_DISASSEMBLER
#include "acdisasm.h"
#endif
#include "acparser.h"
#include "amlcode.h"

#define _COMPONENT          ACPI_DISPATCHER
ACPI_MODULE_NAME("dsmethod")

/* Local prototypes */
static acpi_status
acpi_ds_detect_named_opcodes(struct acpi_walk_state *walk_state,
                             union acpi_parse_object **out_op);

static acpi_status
acpi_ds_create_method_mutex(union acpi_operand_object *method_desc);

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_auto_serialize_method
 *
 * PARAMETERS:  node                        - Namespace Node of the method
 *              obj_desc                    - Method object attached to node
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Parse a control method AML to scan for control methods that
 *              need serialization due to the creation of named objects.
 *
 * NOTE: It is a bit of overkill to mark all such methods serialized, since
 * there is only a problem if the method actually blocks during execution.
 * A blocking operation is, for example, a Sleep() operation, or any access
 * to an operation region. However, it is probably not possible to easily
 * detect whether a method will block or not, so we simply mark all suspicious
 * methods as serialized.
 *
 * NOTE2: This code is essentially a generic routine for parsing a single
 * control method.
 *
 ******************************************************************************/

acpi_status
acpi_ds_auto_serialize_method(struct acpi_namespace_node *node,
                              union acpi_operand_object *obj_desc)
{
        acpi_status status;
        union acpi_parse_object *op = NULL;
        struct acpi_walk_state *walk_state;

        ACPI_FUNCTION_TRACE_PTR(ds_auto_serialize_method, node);

        ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
                          "Method auto-serialization parse [%4.4s] %p\n",
                          acpi_ut_get_node_name(node), node));

        /* Create/Init a root op for the method parse tree */

        op = acpi_ps_alloc_op(AML_METHOD_OP);
        if (!op) {
                return_ACPI_STATUS(AE_NO_MEMORY);
        }

        acpi_ps_set_name(op, node->name.integer);
        op->common.node = node;

        /* Create and initialize a new walk state */

        walk_state =
            acpi_ds_create_walk_state(node->owner_id, NULL, NULL, NULL);
        if (!walk_state) {
                return_ACPI_STATUS(AE_NO_MEMORY);
        }

        status =
            acpi_ds_init_aml_walk(walk_state, op, node,
                                  obj_desc->method.aml_start,
                                  obj_desc->method.aml_length, NULL, 0);
        if (ACPI_FAILURE(status)) {
                acpi_ds_delete_walk_state(walk_state);
                return_ACPI_STATUS(status);
        }

        walk_state->descending_callback = acpi_ds_detect_named_opcodes;

        /* Parse the method, scan for creation of named objects */

        status = acpi_ps_parse_aml(walk_state);
        if (ACPI_FAILURE(status)) {
                return_ACPI_STATUS(status);
        }

        acpi_ps_delete_parse_tree(op);
        return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_detect_named_opcodes
 *
 * PARAMETERS:  walk_state      - Current state of the parse tree walk
 *              out_op          - Unused, required for parser interface
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Descending callback used during the loading of ACPI tables.
 *              Currently used to detect methods that must be marked serialized
 *              in order to avoid problems with the creation of named objects.
 *
 ******************************************************************************/

static acpi_status
acpi_ds_detect_named_opcodes(struct acpi_walk_state *walk_state,
                             union acpi_parse_object **out_op)
{

        ACPI_FUNCTION_NAME(acpi_ds_detect_named_opcodes);

        /* We are only interested in opcodes that create a new name */

        if (!
            (walk_state->op_info->
             flags & (AML_NAMED | AML_CREATE | AML_FIELD))) {
                return (AE_OK);
        }

        /*
         * At this point, we know we have a Named object opcode.
         * Mark the method as serialized. Later code will create a mutex for
         * this method to enforce serialization.
         *
         * Note, ACPI_METHOD_IGNORE_SYNC_LEVEL flag means that we will ignore the
         * Sync Level mechanism for this method, even though it is now serialized.
         * Otherwise, there can be conflicts with existing ASL code that actually
         * uses sync levels.
         */
        walk_state->method_desc->method.sync_level = 0;
        walk_state->method_desc->method.info_flags |=
            (ACPI_METHOD_SERIALIZED | ACPI_METHOD_IGNORE_SYNC_LEVEL);

        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                          "Method serialized [%4.4s] %p - [%s] (%4.4X)\n",
                          walk_state->method_node->name.ascii,
                          walk_state->method_node, walk_state->op_info->name,
                          walk_state->opcode));

        /* Abort the parse, no need to examine this method any further */

        return (AE_CTRL_TERMINATE);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_method_error
 *
 * PARAMETERS:  status          - Execution status
 *              walk_state      - Current state
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Called on method error. Invoke the global exception handler if
 *              present, dump the method data if the disassembler is configured
 *
 *              Note: Allows the exception handler to change the status code
 *
 ******************************************************************************/

acpi_status
acpi_ds_method_error(acpi_status status, struct acpi_walk_state * walk_state)
{
        ACPI_FUNCTION_ENTRY();

        /* Ignore AE_OK and control exception codes */

        if (ACPI_SUCCESS(status) || (status & AE_CODE_CONTROL)) {
                return (status);
        }

        /* Invoke the global exception handler */

        if (acpi_gbl_exception_handler) {

                /* Exit the interpreter, allow handler to execute methods */

                acpi_ex_exit_interpreter();

                /*
                 * Handler can map the exception code to anything it wants, including
                 * AE_OK, in which case the executing method will not be aborted.
                 */
                status = acpi_gbl_exception_handler(status,
                                                    walk_state->method_node ?
                                                    walk_state->method_node->
                                                    name.integer : 0,
                                                    walk_state->opcode,
                                                    walk_state->aml_offset,
                                                    NULL);
                acpi_ex_enter_interpreter();
        }

        acpi_ds_clear_implicit_return(walk_state);

#ifdef ACPI_DISASSEMBLER
        if (ACPI_FAILURE(status)) {

                /* Display method locals/args if disassembler is present */

                acpi_dm_dump_method_info(status, walk_state, walk_state->op);
        }
#endif

        return (status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_create_method_mutex
 *
 * PARAMETERS:  obj_desc            - The method object
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Create a mutex object for a serialized control method
 *
 ******************************************************************************/

static acpi_status
acpi_ds_create_method_mutex(union acpi_operand_object *method_desc)
{
        union acpi_operand_object *mutex_desc;
        acpi_status status;

        ACPI_FUNCTION_TRACE(ds_create_method_mutex);

        /* Create the new mutex object */

        mutex_desc = acpi_ut_create_internal_object(ACPI_TYPE_MUTEX);
        if (!mutex_desc) {
                return_ACPI_STATUS(AE_NO_MEMORY);
        }

        /* Create the actual OS Mutex */

        status = acpi_os_create_mutex(&mutex_desc->mutex.os_mutex);
        if (ACPI_FAILURE(status)) {
                acpi_ut_delete_object_desc(mutex_desc);
                return_ACPI_STATUS(status);
        }

        mutex_desc->mutex.sync_level = method_desc->method.sync_level;
        method_desc->method.mutex = mutex_desc;
        return_ACPI_STATUS(AE_OK);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_begin_method_execution
 *
 * PARAMETERS:  method_node         - Node of the method
 *              obj_desc            - The method object
 *              walk_state          - current state, NULL if not yet executing
 *                                    a method.
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Prepare a method for execution. Parses the method if necessary,
 *              increments the thread count, and waits at the method semaphore
 *              for clearance to execute.
 *
 ******************************************************************************/

acpi_status
acpi_ds_begin_method_execution(struct acpi_namespace_node *method_node,
                               union acpi_operand_object *obj_desc,
                               struct acpi_walk_state *walk_state)
{
        acpi_status status = AE_OK;

        ACPI_FUNCTION_TRACE_PTR(ds_begin_method_execution, method_node);

        if (!method_node) {
                return_ACPI_STATUS(AE_NULL_ENTRY);
        }

        /* Prevent wraparound of thread count */

        if (obj_desc->method.thread_count == ACPI_UINT8_MAX) {
                ACPI_ERROR((AE_INFO,
                            "Method reached maximum reentrancy limit (255)"));
                return_ACPI_STATUS(AE_AML_METHOD_LIMIT);
        }

        /*
         * If this method is serialized, we need to acquire the method mutex.
         */
        if (obj_desc->method.info_flags & ACPI_METHOD_SERIALIZED) {
                /*
                 * Create a mutex for the method if it is defined to be Serialized
                 * and a mutex has not already been created. We defer the mutex creation
                 * until a method is actually executed, to minimize the object count
                 */
                if (!obj_desc->method.mutex) {
                        status = acpi_ds_create_method_mutex(obj_desc);
                        if (ACPI_FAILURE(status)) {
                                return_ACPI_STATUS(status);
                        }
                }

                /*
                 * The current_sync_level (per-thread) must be less than or equal to
                 * the sync level of the method. This mechanism provides some
                 * deadlock prevention.
                 *
                 * If the method was auto-serialized, we just ignore the sync level
                 * mechanism, because auto-serialization of methods can interfere
                 * with ASL code that actually uses sync levels.
                 *
                 * Top-level method invocation has no walk state at this point
                 */
                if (walk_state &&
                    (!(obj_desc->method.
                       info_flags & ACPI_METHOD_IGNORE_SYNC_LEVEL))
                    && (walk_state->thread->current_sync_level >
                        obj_desc->method.mutex->mutex.sync_level)) {
                        ACPI_ERROR((AE_INFO,
                                    "Cannot acquire Mutex for method [%4.4s], current SyncLevel is too large (%u)",
                                    acpi_ut_get_node_name(method_node),
                                    walk_state->thread->current_sync_level));

                        return_ACPI_STATUS(AE_AML_MUTEX_ORDER);
                }

                /*
                 * Obtain the method mutex if necessary. Do not acquire mutex for a
                 * recursive call.
                 */
                if (!walk_state ||
                    !obj_desc->method.mutex->mutex.thread_id ||
                    (walk_state->thread->thread_id !=
                     obj_desc->method.mutex->mutex.thread_id)) {
                        /*
                         * Acquire the method mutex. This releases the interpreter if we
                         * block (and reacquires it before it returns)
                         */
                        status =
                            acpi_ex_system_wait_mutex(obj_desc->method.mutex->
                                                      mutex.os_mutex,
                                                      ACPI_WAIT_FOREVER);
                        if (ACPI_FAILURE(status)) {
                                return_ACPI_STATUS(status);
                        }

                        /* Update the mutex and walk info and save the original sync_level */

                        if (walk_state) {
                                obj_desc->method.mutex->mutex.
                                    original_sync_level =
                                    walk_state->thread->current_sync_level;

                                obj_desc->method.mutex->mutex.thread_id =
                                    walk_state->thread->thread_id;
                                walk_state->thread->current_sync_level =
                                    obj_desc->method.sync_level;
                        } else {
                                obj_desc->method.mutex->mutex.
                                    original_sync_level =
                                    obj_desc->method.mutex->mutex.sync_level;
                        }
                }

                /* Always increase acquisition depth */

                obj_desc->method.mutex->mutex.acquisition_depth++;
        }

        /*
         * Allocate an Owner ID for this method, only if this is the first thread
         * to begin concurrent execution. We only need one owner_id, even if the
         * method is invoked recursively.
         */
        if (!obj_desc->method.owner_id) {
                status = acpi_ut_allocate_owner_id(&obj_desc->method.owner_id);
                if (ACPI_FAILURE(status)) {
                        goto cleanup;
                }
        }

        /*
         * Increment the method parse tree thread count since it has been
         * reentered one more time (even if it is the same thread)
         */
        obj_desc->method.thread_count++;
        acpi_method_count++;
        return_ACPI_STATUS(status);

cleanup:
        /* On error, must release the method mutex (if present) */

        if (obj_desc->method.mutex) {
                acpi_os_release_mutex(obj_desc->method.mutex->mutex.os_mutex);
        }
        return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_call_control_method
 *
 * PARAMETERS:  thread              - Info for this thread
 *              this_walk_state     - Current walk state
 *              op                  - Current Op to be walked
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Transfer execution to a called control method
 *
 ******************************************************************************/

acpi_status
acpi_ds_call_control_method(struct acpi_thread_state *thread,
                            struct acpi_walk_state *this_walk_state,
                            union acpi_parse_object *op)
{
        acpi_status status;
        struct acpi_namespace_node *method_node;
        struct acpi_walk_state *next_walk_state = NULL;
        union acpi_operand_object *obj_desc;
        struct acpi_evaluate_info *info;
        u32 i;

        ACPI_FUNCTION_TRACE_PTR(ds_call_control_method, this_walk_state);

        ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
                          "Calling method %p, currentstate=%p\n",
                          this_walk_state->prev_op, this_walk_state));

        /*
         * Get the namespace entry for the control method we are about to call
         */
        method_node = this_walk_state->method_call_node;
        if (!method_node) {
                return_ACPI_STATUS(AE_NULL_ENTRY);
        }

        obj_desc = acpi_ns_get_attached_object(method_node);
        if (!obj_desc) {
                return_ACPI_STATUS(AE_NULL_OBJECT);
        }

        /* Init for new method, possibly wait on method mutex */

        status = acpi_ds_begin_method_execution(method_node, obj_desc,
                                                this_walk_state);
        if (ACPI_FAILURE(status)) {
                return_ACPI_STATUS(status);
        }

        /* Begin method parse/execution. Create a new walk state */

        next_walk_state = acpi_ds_create_walk_state(obj_desc->method.owner_id,
                                                    NULL, obj_desc, thread);
        if (!next_walk_state) {
                status = AE_NO_MEMORY;
                goto cleanup;
        }

        /*
         * The resolved arguments were put on the previous walk state's operand
         * stack. Operands on the previous walk state stack always
         * start at index 0. Also, null terminate the list of arguments
         */
        this_walk_state->operands[this_walk_state->num_operands] = NULL;

        /*
         * Allocate and initialize the evaluation information block
         * TBD: this is somewhat inefficient, should change interface to
         * ds_init_aml_walk. For now, keeps this struct off the CPU stack
         */
        info = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_evaluate_info));
        if (!info) {
                status = AE_NO_MEMORY;
                goto cleanup;
        }

        info->parameters = &this_walk_state->operands[0];

        status = acpi_ds_init_aml_walk(next_walk_state, NULL, method_node,
                                       obj_desc->method.aml_start,
                                       obj_desc->method.aml_length, info,
                                       ACPI_IMODE_EXECUTE);

        ACPI_FREE(info);
        if (ACPI_FAILURE(status)) {
                goto cleanup;
        }

        /*
         * Delete the operands on the previous walkstate operand stack
         * (they were copied to new objects)
         */
        for (i = 0; i < obj_desc->method.param_count; i++) {
                acpi_ut_remove_reference(this_walk_state->operands[i]);
                this_walk_state->operands[i] = NULL;
        }

        /* Clear the operand stack */

        this_walk_state->num_operands = 0;

        ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
                          "**** Begin nested execution of [%4.4s] **** WalkState=%p\n",
                          method_node->name.ascii, next_walk_state));

        /* Invoke an internal method if necessary */

        if (obj_desc->method.info_flags & ACPI_METHOD_INTERNAL_ONLY) {
                status =
                    obj_desc->method.dispatch.implementation(next_walk_state);
                if (status == AE_OK) {
                        status = AE_CTRL_TERMINATE;
                }
        }

        return_ACPI_STATUS(status);

cleanup:

        /* On error, we must terminate the method properly */

        acpi_ds_terminate_control_method(obj_desc, next_walk_state);
        if (next_walk_state) {
                acpi_ds_delete_walk_state(next_walk_state);
        }

        return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_restart_control_method
 *
 * PARAMETERS:  walk_state          - State for preempted method (caller)
 *              return_desc         - Return value from the called method
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Restart a method that was preempted by another (nested) method
 *              invocation. Handle the return value (if any) from the callee.
 *
 ******************************************************************************/

acpi_status
acpi_ds_restart_control_method(struct acpi_walk_state *walk_state,
                               union acpi_operand_object *return_desc)
{
        acpi_status status;
        int same_as_implicit_return;

        ACPI_FUNCTION_TRACE_PTR(ds_restart_control_method, walk_state);

        ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
                          "****Restart [%4.4s] Op %p ReturnValueFromCallee %p\n",
                          acpi_ut_get_node_name(walk_state->method_node),
                          walk_state->method_call_op, return_desc));

        ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
                          "    ReturnFromThisMethodUsed?=%X ResStack %p Walk %p\n",
                          walk_state->return_used,
                          walk_state->results, walk_state));

        /* Did the called method return a value? */

        if (return_desc) {

                /* Is the implicit return object the same as the return desc? */

                same_as_implicit_return =
                    (walk_state->implicit_return_obj == return_desc);

                /* Are we actually going to use the return value? */

                if (walk_state->return_used) {

                        /* Save the return value from the previous method */

                        status = acpi_ds_result_push(return_desc, walk_state);
                        if (ACPI_FAILURE(status)) {
                                acpi_ut_remove_reference(return_desc);
                                return_ACPI_STATUS(status);
                        }

                        /*
                         * Save as THIS method's return value in case it is returned
                         * immediately to yet another method
                         */
                        walk_state->return_desc = return_desc;
                }

                /*
                 * The following code is the optional support for the so-called
                 * "implicit return". Some AML code assumes that the last value of the
                 * method is "implicitly" returned to the caller, in the absence of an
                 * explicit return value.
                 *
                 * Just save the last result of the method as the return value.
                 *
                 * NOTE: this is optional because the ASL language does not actually
                 * support this behavior.
                 */
                else if (!acpi_ds_do_implicit_return
                         (return_desc, walk_state, FALSE)
                         || same_as_implicit_return) {
                        /*
                         * Delete the return value if it will not be used by the
                         * calling method or remove one reference if the explicit return
                         * is the same as the implicit return value.
                         */
                        acpi_ut_remove_reference(return_desc);
                }
        }

        return_ACPI_STATUS(AE_OK);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ds_terminate_control_method
 *
 * PARAMETERS:  method_desc         - Method object
 *              walk_state          - State associated with the method
 *
 * RETURN:      None
 *
 * DESCRIPTION: Terminate a control method. Delete everything that the method
 *              created, delete all locals and arguments, and delete the parse
 *              tree if requested.
 *
 * MUTEX:       Interpreter is locked
 *
 ******************************************************************************/

void
acpi_ds_terminate_control_method(union acpi_operand_object *method_desc,
                                 struct acpi_walk_state *walk_state)
{

        ACPI_FUNCTION_TRACE_PTR(ds_terminate_control_method, walk_state);

        /* method_desc is required, walk_state is optional */

        if (!method_desc) {
                return_VOID;
        }

        if (walk_state) {

                /* Delete all arguments and locals */

                acpi_ds_method_data_delete_all(walk_state);

                /*
                 * If method is serialized, release the mutex and restore the
                 * current sync level for this thread
                 */
                if (method_desc->method.mutex) {

                        /* Acquisition Depth handles recursive calls */

                        method_desc->method.mutex->mutex.acquisition_depth--;
                        if (!method_desc->method.mutex->mutex.acquisition_depth) {
                                walk_state->thread->current_sync_level =
                                    method_desc->method.mutex->mutex.
                                    original_sync_level;

                                acpi_os_release_mutex(method_desc->method.
                                                      mutex->mutex.os_mutex);
                                method_desc->method.mutex->mutex.thread_id = 0;
                        }
                }

                /*
                 * Delete any namespace objects created anywhere within the
                 * namespace by the execution of this method. Unless:
                 * 1) This method is a module-level executable code method, in which
                 *    case we want make the objects permanent.
                 * 2) There are other threads executing the method, in which case we
                 *    will wait until the last thread has completed.
                 */
                if (!(method_desc->method.info_flags & ACPI_METHOD_MODULE_LEVEL)
                    && (method_desc->method.thread_count == 1)) {

                        /* Delete any direct children of (created by) this method */

                        acpi_ns_delete_namespace_subtree(walk_state->
                                                         method_node);

                        /*
                         * Delete any objects that were created by this method
                         * elsewhere in the namespace (if any were created).
                         * Use of the ACPI_METHOD_MODIFIED_NAMESPACE optimizes the
                         * deletion such that we don't have to perform an entire
                         * namespace walk for every control method execution.
                         */
                        if (method_desc->method.
                            info_flags & ACPI_METHOD_MODIFIED_NAMESPACE) {
                                acpi_ns_delete_namespace_by_owner(method_desc->
                                                                  method.
                                                                  owner_id);
                                method_desc->method.info_flags &=
                                    ~ACPI_METHOD_MODIFIED_NAMESPACE;
                        }
                }
        }

        /* Decrement the thread count on the method */

        if (method_desc->method.thread_count) {
                method_desc->method.thread_count--;
        } else {
                ACPI_ERROR((AE_INFO, "Invalid zero thread count in method"));
        }

        /* Are there any other threads currently executing this method? */

        if (method_desc->method.thread_count) {
                /*
                 * Additional threads. Do not release the owner_id in this case,
                 * we immediately reuse it for the next thread executing this method
                 */
                ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
                                  "*** Completed execution of one thread, %u threads remaining\n",
                                  method_desc->method.thread_count));
        } else {
                /* This is the only executing thread for this method */

                /*
                 * Support to dynamically change a method from not_serialized to
                 * Serialized if it appears that the method is incorrectly written and
                 * does not support multiple thread execution. The best example of this
                 * is if such a method creates namespace objects and blocks. A second
                 * thread will fail with an AE_ALREADY_EXISTS exception.
                 *
                 * This code is here because we must wait until the last thread exits
                 * before marking the method as serialized.
                 */
                if (method_desc->method.
                    info_flags & ACPI_METHOD_SERIALIZED_PENDING) {
                        if (walk_state) {
                                ACPI_INFO((AE_INFO,
                                           "Marking method %4.4s as Serialized because of AE_ALREADY_EXISTS error",
                                           walk_state->method_node->name.
                                           ascii));
                        }

                        /*
                         * Method tried to create an object twice and was marked as
                         * "pending serialized". The probable cause is that the method
                         * cannot handle reentrancy.
                         *
                         * The method was created as not_serialized, but it tried to create
                         * a named object and then blocked, causing the second thread
                         * entrance to begin and then fail. Workaround this problem by
                         * marking the method permanently as Serialized when the last
                         * thread exits here.
                         */
                        method_desc->method.info_flags &=
                            ~ACPI_METHOD_SERIALIZED_PENDING;
                        method_desc->method.info_flags |=
                            (ACPI_METHOD_SERIALIZED |
                             ACPI_METHOD_IGNORE_SYNC_LEVEL);
                        method_desc->method.sync_level = 0;
                }

                /* No more threads, we can free the owner_id */

                if (!
                    (method_desc->method.
                     info_flags & ACPI_METHOD_MODULE_LEVEL)) {
                        acpi_ut_release_owner_id(&method_desc->method.owner_id);
                }
        }

        return_VOID;
}