drivers/acpi/acpica/dsmethod.c

   1 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
   2 /******************************************************************************
   3  *
   4  * Module Name: dsmethod - Parser/Interpreter interface - control method parsing
   5  *
   6  * Copyright (C) 2000 - 2021, Intel Corp.
   7  *
   8  *****************************************************************************/
   9
  10 #include <acpi/acpi.h>
  11 #include "accommon.h"
  12 #include "acdispat.h"
  13 #include "acinterp.h"
  14 #include "acnamesp.h"
  15 #include "acparser.h"
  16 #include "amlcode.h"
  17 #include "acdebug.h"
  18
  19 #define _COMPONENT          ACPI_DISPATCHER
  20 ACPI_MODULE_NAME("dsmethod")
  21
  22 /* Local prototypes */
  23 static acpi_status
  24 acpi_ds_detect_named_opcodes(struct acpi_walk_state *walk_state,
  25                              union acpi_parse_object **out_op);
  26
  27 static acpi_status
  28 acpi_ds_create_method_mutex(union acpi_operand_object *method_desc);
  29
  30 /*******************************************************************************
  31  *
  32  * FUNCTION:    acpi_ds_auto_serialize_method
  33  *
  34  * PARAMETERS:  node                        - Namespace Node of the method
  35  *              obj_desc                    - Method object attached to node
  36  *
  37  * RETURN:      Status
  38  *
  39  * DESCRIPTION: Parse a control method AML to scan for control methods that
  40  *              need serialization due to the creation of named objects.
  41  *
  42  * NOTE: It is a bit of overkill to mark all such methods serialized, since
  43  * there is only a problem if the method actually blocks during execution.
  44  * A blocking operation is, for example, a Sleep() operation, or any access
  45  * to an operation region. However, it is probably not possible to easily
  46  * detect whether a method will block or not, so we simply mark all suspicious
  47  * methods as serialized.
  48  *
  49  * NOTE2: This code is essentially a generic routine for parsing a single
  50  * control method.
  51  *
  52  ******************************************************************************/
  53
  54 acpi_status
  55 acpi_ds_auto_serialize_method(struct acpi_namespace_node *node,
  56                               union acpi_operand_object *obj_desc)
  57 {
  58         acpi_status status;
  59         union acpi_parse_object *op = NULL;
  60         struct acpi_walk_state *walk_state;
  61
  62         ACPI_FUNCTION_TRACE_PTR(ds_auto_serialize_method, node);
  63
  64         ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
  65                           "Method auto-serialization parse [%4.4s] %p\n",
  66                           acpi_ut_get_node_name(node), node));
  67
  68         /* Create/Init a root op for the method parse tree */
  69
  70         op = acpi_ps_alloc_op(AML_METHOD_OP, obj_desc->method.aml_start);
  71         if (!op) {
  72                 return_ACPI_STATUS(AE_NO_MEMORY);
  73         }
  74
  75         acpi_ps_set_name(op, node->name.integer);
  76         op->common.node = node;
  77
  78         /* Create and initialize a new walk state */
  79
  80         walk_state =
  81             acpi_ds_create_walk_state(node->owner_id, NULL, NULL, NULL);
  82         if (!walk_state) {
  83                 acpi_ps_free_op(op);
  84                 return_ACPI_STATUS(AE_NO_MEMORY);
  85         }
  86
  87         status = acpi_ds_init_aml_walk(walk_state, op, node,
  88                                        obj_desc->method.aml_start,
  89                                        obj_desc->method.aml_length, NULL, 0);
  90         if (ACPI_FAILURE(status)) {
  91                 acpi_ds_delete_walk_state(walk_state);
  92                 acpi_ps_free_op(op);
  93                 return_ACPI_STATUS(status);
  94         }
  95
  96         walk_state->descending_callback = acpi_ds_detect_named_opcodes;
  97
  98         /* Parse the method, scan for creation of named objects */
  99
 100         status = acpi_ps_parse_aml(walk_state);
 101
 102         acpi_ps_delete_parse_tree(op);
 103         return_ACPI_STATUS(status);
 104 }
 105
 106 /*******************************************************************************
 107  *
 108  * FUNCTION:    acpi_ds_detect_named_opcodes
 109  *
 110  * PARAMETERS:  walk_state      - Current state of the parse tree walk
 111  *              out_op          - Unused, required for parser interface
 112  *
 113  * RETURN:      Status
 114  *
 115  * DESCRIPTION: Descending callback used during the loading of ACPI tables.
 116  *              Currently used to detect methods that must be marked serialized
 117  *              in order to avoid problems with the creation of named objects.
 118  *
 119  ******************************************************************************/
 120
 121 static acpi_status
 122 acpi_ds_detect_named_opcodes(struct acpi_walk_state *walk_state,
 123                              union acpi_parse_object **out_op)
 124 {
 125
 126         ACPI_FUNCTION_NAME(acpi_ds_detect_named_opcodes);
 127
 128         /* We are only interested in opcodes that create a new name */
 129
 130         if (!
 131             (walk_state->op_info->
 132              flags & (AML_NAMED | AML_CREATE | AML_FIELD))) {
 133                 return (AE_OK);
 134         }
 135
 136         /*
 137          * At this point, we know we have a Named object opcode.
 138          * Mark the method as serialized. Later code will create a mutex for
 139          * this method to enforce serialization.
 140          *
 141          * Note, ACPI_METHOD_IGNORE_SYNC_LEVEL flag means that we will ignore the
 142          * Sync Level mechanism for this method, even though it is now serialized.
 143          * Otherwise, there can be conflicts with existing ASL code that actually
 144          * uses sync levels.
 145          */
 146         walk_state->method_desc->method.sync_level = 0;
 147         walk_state->method_desc->method.info_flags |=
 148             (ACPI_METHOD_SERIALIZED | ACPI_METHOD_IGNORE_SYNC_LEVEL);
 149
 150         ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 151                           "Method serialized [%4.4s] %p - [%s] (%4.4X)\n",
 152                           walk_state->method_node->name.ascii,
 153                           walk_state->method_node, walk_state->op_info->name,
 154                           walk_state->opcode));
 155
 156         /* Abort the parse, no need to examine this method any further */
 157
 158         return (AE_CTRL_TERMINATE);
 159 }
 160
 161 /*******************************************************************************
 162  *
 163  * FUNCTION:    acpi_ds_method_error
 164  *
 165  * PARAMETERS:  status          - Execution status
 166  *              walk_state      - Current state
 167  *
 168  * RETURN:      Status
 169  *
 170  * DESCRIPTION: Called on method error. Invoke the global exception handler if
 171  *              present, dump the method data if the debugger is configured
 172  *
 173  *              Note: Allows the exception handler to change the status code
 174  *
 175  ******************************************************************************/
 176
 177 acpi_status
 178 acpi_ds_method_error(acpi_status status, struct acpi_walk_state *walk_state)
 179 {
 180         u32 aml_offset;
 181         acpi_name name = 0;
 182
 183         ACPI_FUNCTION_ENTRY();
 184
 185         /* Ignore AE_OK and control exception codes */
 186
 187         if (ACPI_SUCCESS(status) || (status & AE_CODE_CONTROL)) {
 188                 return (status);
 189         }
 190
 191         /* Invoke the global exception handler */
 192
 193         if (acpi_gbl_exception_handler) {
 194
 195                 /* Exit the interpreter, allow handler to execute methods */
 196
 197                 acpi_ex_exit_interpreter();
 198
 199                 /*
 200                  * Handler can map the exception code to anything it wants, including
 201                  * AE_OK, in which case the executing method will not be aborted.
 202                  */
 203                 aml_offset = (u32)ACPI_PTR_DIFF(walk_state->aml,
 204                                                 walk_state->parser_state.
 205                                                 aml_start);
 206
 207                 if (walk_state->method_node) {
 208                         name = walk_state->method_node->name.integer;
 209                 } else if (walk_state->deferred_node) {
 210                         name = walk_state->deferred_node->name.integer;
 211                 }
 212
 213                 status = acpi_gbl_exception_handler(status, name,
 214                                                     walk_state->opcode,
 215                                                     aml_offset, NULL);
 216                 acpi_ex_enter_interpreter();
 217         }
 218
 219         acpi_ds_clear_implicit_return(walk_state);
 220
 221         if (ACPI_FAILURE(status)) {
 222                 acpi_ds_dump_method_stack(status, walk_state, walk_state->op);
 223
 224                 /* Display method locals/args if debugger is present */
 225
 226 #ifdef ACPI_DEBUGGER
 227                 acpi_db_dump_method_info(status, walk_state);
 228 #endif
 229         }
 230
 231         return (status);
 232 }
 233
 234 /*******************************************************************************
 235  *
 236  * FUNCTION:    acpi_ds_create_method_mutex
 237  *
 238  * PARAMETERS:  obj_desc            - The method object
 239  *
 240  * RETURN:      Status
 241  *
 242  * DESCRIPTION: Create a mutex object for a serialized control method
 243  *
 244  ******************************************************************************/
 245
 246 static acpi_status
 247 acpi_ds_create_method_mutex(union acpi_operand_object *method_desc)
 248 {
 249         union acpi_operand_object *mutex_desc;
 250         acpi_status status;
 251
 252         ACPI_FUNCTION_TRACE(ds_create_method_mutex);
 253
 254         /* Create the new mutex object */
 255
 256         mutex_desc = acpi_ut_create_internal_object(ACPI_TYPE_MUTEX);
 257         if (!mutex_desc) {
 258                 return_ACPI_STATUS(AE_NO_MEMORY);
 259         }
 260
 261         /* Create the actual OS Mutex */
 262
 263         status = acpi_os_create_mutex(&mutex_desc->mutex.os_mutex);
 264         if (ACPI_FAILURE(status)) {
 265                 acpi_ut_delete_object_desc(mutex_desc);
 266                 return_ACPI_STATUS(status);
 267         }
 268
 269         mutex_desc->mutex.sync_level = method_desc->method.sync_level;
 270         method_desc->method.mutex = mutex_desc;
 271         return_ACPI_STATUS(AE_OK);
 272 }
 273
 274 /*******************************************************************************
 275  *
 276  * FUNCTION:    acpi_ds_begin_method_execution
 277  *
 278  * PARAMETERS:  method_node         - Node of the method
 279  *              obj_desc            - The method object
 280  *              walk_state          - current state, NULL if not yet executing
 281  *                                    a method.
 282  *
 283  * RETURN:      Status
 284  *
 285  * DESCRIPTION: Prepare a method for execution. Parses the method if necessary,
 286  *              increments the thread count, and waits at the method semaphore
 287  *              for clearance to execute.
 288  *
 289  ******************************************************************************/
 290
 291 acpi_status
 292 acpi_ds_begin_method_execution(struct acpi_namespace_node *method_node,
 293                                union acpi_operand_object *obj_desc,
 294                                struct acpi_walk_state *walk_state)
 295 {
 296         acpi_status status = AE_OK;
 297
 298         ACPI_FUNCTION_TRACE_PTR(ds_begin_method_execution, method_node);
 299
 300         if (!method_node) {
 301                 return_ACPI_STATUS(AE_NULL_ENTRY);
 302         }
 303
 304         acpi_ex_start_trace_method(method_node, obj_desc, walk_state);
 305
 306         /* Prevent wraparound of thread count */
 307
 308         if (obj_desc->method.thread_count == ACPI_UINT8_MAX) {
 309                 ACPI_ERROR((AE_INFO,
 310                             "Method reached maximum reentrancy limit (255)"));
 311                 return_ACPI_STATUS(AE_AML_METHOD_LIMIT);
 312         }
 313
 314         /*
 315          * If this method is serialized, we need to acquire the method mutex.
 316          */
 317         if (obj_desc->method.info_flags & ACPI_METHOD_SERIALIZED) {
 318                 /*
 319                  * Create a mutex for the method if it is defined to be Serialized
 320                  * and a mutex has not already been created. We defer the mutex creation
 321                  * until a method is actually executed, to minimize the object count
 322                  */
 323                 if (!obj_desc->method.mutex) {
 324                         status = acpi_ds_create_method_mutex(obj_desc);
 325                         if (ACPI_FAILURE(status)) {
 326                                 return_ACPI_STATUS(status);
 327                         }
 328                 }
 329
 330                 /*
 331                  * The current_sync_level (per-thread) must be less than or equal to
 332                  * the sync level of the method. This mechanism provides some
 333                  * deadlock prevention.
 334                  *
 335                  * If the method was auto-serialized, we just ignore the sync level
 336                  * mechanism, because auto-serialization of methods can interfere
 337                  * with ASL code that actually uses sync levels.
 338                  *
 339                  * Top-level method invocation has no walk state at this point
 340                  */
 341                 if (walk_state &&
 342                     (!(obj_desc->method.
 343                        info_flags & ACPI_METHOD_IGNORE_SYNC_LEVEL))
 344                     && (walk_state->thread->current_sync_level >
 345                         obj_desc->method.mutex->mutex.sync_level)) {
 346                         ACPI_ERROR((AE_INFO,
 347                                     "Cannot acquire Mutex for method [%4.4s]"
 348                                     ", current SyncLevel is too large (%u)",
 349                                     acpi_ut_get_node_name(method_node),
 350                                     walk_state->thread->current_sync_level));
 351
 352                         return_ACPI_STATUS(AE_AML_MUTEX_ORDER);
 353                 }
 354
 355                 /*
 356                  * Obtain the method mutex if necessary. Do not acquire mutex for a
 357                  * recursive call.
 358                  */
 359                 if (!walk_state ||
 360                     !obj_desc->method.mutex->mutex.thread_id ||
 361                     (walk_state->thread->thread_id !=
 362                      obj_desc->method.mutex->mutex.thread_id)) {
 363                         /*
 364                          * Acquire the method mutex. This releases the interpreter if we
 365                          * block (and reacquires it before it returns)
 366                          */
 367                         status =
 368                             acpi_ex_system_wait_mutex(obj_desc->method.mutex->
 369                                                       mutex.os_mutex,
 370                                                       ACPI_WAIT_FOREVER);
 371                         if (ACPI_FAILURE(status)) {
 372                                 return_ACPI_STATUS(status);
 373                         }
 374
 375                         /* Update the mutex and walk info and save the original sync_level */
 376
 377                         if (walk_state) {
 378                                 obj_desc->method.mutex->mutex.
 379                                     original_sync_level =
 380                                     walk_state->thread->current_sync_level;
 381
 382                                 obj_desc->method.mutex->mutex.thread_id =
 383                                     walk_state->thread->thread_id;
 384
 385                                 /*
 386                                  * Update the current sync_level only if this is not an auto-
 387                                  * serialized method. In the auto case, we have to ignore
 388                                  * the sync level for the method mutex (created for the
 389                                  * auto-serialization) because we have no idea of what the
 390                                  * sync level should be. Therefore, just ignore it.
 391                                  */
 392                                 if (!(obj_desc->method.info_flags &
 393                                       ACPI_METHOD_IGNORE_SYNC_LEVEL)) {
 394                                         walk_state->thread->current_sync_level =
 395                                             obj_desc->method.sync_level;
 396                                 }
 397                         } else {
 398                                 obj_desc->method.mutex->mutex.
 399                                     original_sync_level =
 400                                     obj_desc->method.mutex->mutex.sync_level;
 401
 402                                 obj_desc->method.mutex->mutex.thread_id =
 403                                     acpi_os_get_thread_id();
 404                         }
 405                 }
 406
 407                 /* Always increase acquisition depth */
 408
 409                 obj_desc->method.mutex->mutex.acquisition_depth++;
 410         }
 411
 412         /*
 413          * Allocate an Owner ID for this method, only if this is the first thread
 414          * to begin concurrent execution. We only need one owner_id, even if the
 415          * method is invoked recursively.
 416          */
 417         if (!obj_desc->method.owner_id) {
 418                 status = acpi_ut_allocate_owner_id(&obj_desc->method.owner_id);
 419                 if (ACPI_FAILURE(status)) {
 420                         goto cleanup;
 421                 }
 422         }
 423
 424         /*
 425          * Increment the method parse tree thread count since it has been
 426          * reentered one more time (even if it is the same thread)
 427          */
 428         obj_desc->method.thread_count++;
 429         acpi_method_count++;
 430         return_ACPI_STATUS(status);
 431
 432 cleanup:
 433         /* On error, must release the method mutex (if present) */
 434
 435         if (obj_desc->method.mutex) {
 436                 acpi_os_release_mutex(obj_desc->method.mutex->mutex.os_mutex);
 437         }
 438         return_ACPI_STATUS(status);
 439 }
 440
 441 /*******************************************************************************
 442  *
 443  * FUNCTION:    acpi_ds_call_control_method
 444  *
 445  * PARAMETERS:  thread              - Info for this thread
 446  *              this_walk_state     - Current walk state
 447  *              op                  - Current Op to be walked
 448  *
 449  * RETURN:      Status
 450  *
 451  * DESCRIPTION: Transfer execution to a called control method
 452  *
 453  ******************************************************************************/
 454
 455 acpi_status
 456 acpi_ds_call_control_method(struct acpi_thread_state *thread,
 457                             struct acpi_walk_state *this_walk_state,
 458                             union acpi_parse_object *op)
 459 {
 460         acpi_status status;
 461         struct acpi_namespace_node *method_node;
 462         struct acpi_walk_state *next_walk_state = NULL;
 463         union acpi_operand_object *obj_desc;
 464         struct acpi_evaluate_info *info;
 465         u32 i;
 466
 467         ACPI_FUNCTION_TRACE_PTR(ds_call_control_method, this_walk_state);
 468
 469         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 470                           "Calling method %p, currentstate=%p\n",
 471                           this_walk_state->prev_op, this_walk_state));
 472
 473         /*
 474          * Get the namespace entry for the control method we are about to call
 475          */
 476         method_node = this_walk_state->method_call_node;
 477         if (!method_node) {
 478                 return_ACPI_STATUS(AE_NULL_ENTRY);
 479         }
 480
 481         obj_desc = acpi_ns_get_attached_object(method_node);
 482         if (!obj_desc) {
 483                 return_ACPI_STATUS(AE_NULL_OBJECT);
 484         }
 485
 486         /* Init for new method, possibly wait on method mutex */
 487
 488         status =
 489             acpi_ds_begin_method_execution(method_node, obj_desc,
 490                                            this_walk_state);
 491         if (ACPI_FAILURE(status)) {
 492                 return_ACPI_STATUS(status);
 493         }
 494
 495         /* Begin method parse/execution. Create a new walk state */
 496
 497         next_walk_state =
 498             acpi_ds_create_walk_state(obj_desc->method.owner_id, NULL, obj_desc,
 499                                       thread);
 500         if (!next_walk_state) {
 501                 status = AE_NO_MEMORY;
 502                 goto cleanup;
 503         }
 504
 505         /*
 506          * The resolved arguments were put on the previous walk state's operand
 507          * stack. Operands on the previous walk state stack always
 508          * start at index 0. Also, null terminate the list of arguments
 509          */
 510         this_walk_state->operands[this_walk_state->num_operands] = NULL;
 511
 512         /*
 513          * Allocate and initialize the evaluation information block
 514          * TBD: this is somewhat inefficient, should change interface to
 515          * ds_init_aml_walk. For now, keeps this struct off the CPU stack
 516          */
 517         info = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_evaluate_info));
 518         if (!info) {
 519                 status = AE_NO_MEMORY;
 520                 goto cleanup;
 521         }
 522
 523         info->parameters = &this_walk_state->operands[0];
 524
 525         status = acpi_ds_init_aml_walk(next_walk_state, NULL, method_node,
 526                                        obj_desc->method.aml_start,
 527                                        obj_desc->method.aml_length, info,
 528                                        ACPI_IMODE_EXECUTE);
 529
 530         ACPI_FREE(info);
 531         if (ACPI_FAILURE(status)) {
 532                 goto cleanup;
 533         }
 534
 535         next_walk_state->method_nesting_depth =
 536             this_walk_state->method_nesting_depth + 1;
 537
 538         /*
 539          * Delete the operands on the previous walkstate operand stack
 540          * (they were copied to new objects)
 541          */
 542         for (i = 0; i < obj_desc->method.param_count; i++) {
 543                 acpi_ut_remove_reference(this_walk_state->operands[i]);
 544                 this_walk_state->operands[i] = NULL;
 545         }
 546
 547         /* Clear the operand stack */
 548
 549         this_walk_state->num_operands = 0;
 550
 551         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 552                           "**** Begin nested execution of [%4.4s] **** WalkState=%p\n",
 553                           method_node->name.ascii, next_walk_state));
 554
 555         this_walk_state->method_pathname =
 556             acpi_ns_get_normalized_pathname(method_node, TRUE);
 557         this_walk_state->method_is_nested = TRUE;
 558
 559         /* Optional object evaluation log */
 560
 561         ACPI_DEBUG_PRINT_RAW((ACPI_DB_EVALUATION,
 562                               "%-26s:  %*s%s\n", "   Nested method call",
 563                               next_walk_state->method_nesting_depth * 3, " ",
 564                               &this_walk_state->method_pathname[1]));
 565
 566         /* Invoke an internal method if necessary */
 567
 568         if (obj_desc->method.info_flags & ACPI_METHOD_INTERNAL_ONLY) {
 569                 status =
 570                     obj_desc->method.dispatch.implementation(next_walk_state);
 571                 if (status == AE_OK) {
 572                         status = AE_CTRL_TERMINATE;
 573                 }
 574         }
 575
 576         return_ACPI_STATUS(status);
 577
 578 cleanup:
 579
 580         /* On error, we must terminate the method properly */
 581
 582         acpi_ds_terminate_control_method(obj_desc, next_walk_state);
 583         acpi_ds_delete_walk_state(next_walk_state);
 584
 585         return_ACPI_STATUS(status);
 586 }
 587
 588 /*******************************************************************************
 589  *
 590  * FUNCTION:    acpi_ds_restart_control_method
 591  *
 592  * PARAMETERS:  walk_state          - State for preempted method (caller)
 593  *              return_desc         - Return value from the called method
 594  *
 595  * RETURN:      Status
 596  *
 597  * DESCRIPTION: Restart a method that was preempted by another (nested) method
 598  *              invocation. Handle the return value (if any) from the callee.
 599  *
 600  ******************************************************************************/
 601
 602 acpi_status
 603 acpi_ds_restart_control_method(struct acpi_walk_state *walk_state,
 604                                union acpi_operand_object *return_desc)
 605 {
 606         acpi_status status;
 607         int same_as_implicit_return;
 608
 609         ACPI_FUNCTION_TRACE_PTR(ds_restart_control_method, walk_state);
 610
 611         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 612                           "****Restart [%4.4s] Op %p ReturnValueFromCallee %p\n",
 613                           acpi_ut_get_node_name(walk_state->method_node),
 614                           walk_state->method_call_op, return_desc));
 615
 616         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 617                           "    ReturnFromThisMethodUsed?=%X ResStack %p Walk %p\n",
 618                           walk_state->return_used,
 619                           walk_state->results, walk_state));
 620
 621         /* Did the called method return a value? */
 622
 623         if (return_desc) {
 624
 625                 /* Is the implicit return object the same as the return desc? */
 626
 627                 same_as_implicit_return =
 628                     (walk_state->implicit_return_obj == return_desc);
 629
 630                 /* Are we actually going to use the return value? */
 631
 632                 if (walk_state->return_used) {
 633
 634                         /* Save the return value from the previous method */
 635
 636                         status = acpi_ds_result_push(return_desc, walk_state);
 637                         if (ACPI_FAILURE(status)) {
 638                                 acpi_ut_remove_reference(return_desc);
 639                                 return_ACPI_STATUS(status);
 640                         }
 641
 642                         /*
 643                          * Save as THIS method's return value in case it is returned
 644                          * immediately to yet another method
 645                          */
 646                         walk_state->return_desc = return_desc;
 647                 }
 648
 649                 /*
 650                  * The following code is the optional support for the so-called
 651                  * "implicit return". Some AML code assumes that the last value of the
 652                  * method is "implicitly" returned to the caller, in the absence of an
 653                  * explicit return value.
 654                  *
 655                  * Just save the last result of the method as the return value.
 656                  *
 657                  * NOTE: this is optional because the ASL language does not actually
 658                  * support this behavior.
 659                  */
 660                 else if (!acpi_ds_do_implicit_return
 661                          (return_desc, walk_state, FALSE)
 662                          || same_as_implicit_return) {
 663                         /*
 664                          * Delete the return value if it will not be used by the
 665                          * calling method or remove one reference if the explicit return
 666                          * is the same as the implicit return value.
 667                          */
 668                         acpi_ut_remove_reference(return_desc);
 669                 }
 670         }
 671
 672         return_ACPI_STATUS(AE_OK);
 673 }
 674
 675 /*******************************************************************************
 676  *
 677  * FUNCTION:    acpi_ds_terminate_control_method
 678  *
 679  * PARAMETERS:  method_desc         - Method object
 680  *              walk_state          - State associated with the method
 681  *
 682  * RETURN:      None
 683  *
 684  * DESCRIPTION: Terminate a control method. Delete everything that the method
 685  *              created, delete all locals and arguments, and delete the parse
 686  *              tree if requested.
 687  *
 688  * MUTEX:       Interpreter is locked
 689  *
 690  ******************************************************************************/
 691
 692 void
 693 acpi_ds_terminate_control_method(union acpi_operand_object *method_desc,
 694                                  struct acpi_walk_state *walk_state)
 695 {
 696
 697         ACPI_FUNCTION_TRACE_PTR(ds_terminate_control_method, walk_state);
 698
 699         /* method_desc is required, walk_state is optional */
 700
 701         if (!method_desc) {
 702                 return_VOID;
 703         }
 704
 705         if (walk_state) {
 706
 707                 /* Delete all arguments and locals */
 708
 709                 acpi_ds_method_data_delete_all(walk_state);
 710
 711                 /*
 712                  * Delete any namespace objects created anywhere within the
 713                  * namespace by the execution of this method. Unless:
 714                  * 1) This method is a module-level executable code method, in which
 715                  *    case we want make the objects permanent.
 716                  * 2) There are other threads executing the method, in which case we
 717                  *    will wait until the last thread has completed.
 718                  */
 719                 if (!(method_desc->method.info_flags & ACPI_METHOD_MODULE_LEVEL)
 720                     && (method_desc->method.thread_count == 1)) {
 721
 722                         /* Delete any direct children of (created by) this method */
 723
 724                         (void)acpi_ex_exit_interpreter();
 725                         acpi_ns_delete_namespace_subtree(walk_state->
 726                                                          method_node);
 727                         (void)acpi_ex_enter_interpreter();
 728
 729                         /*
 730                          * Delete any objects that were created by this method
 731                          * elsewhere in the namespace (if any were created).
 732                          * Use of the ACPI_METHOD_MODIFIED_NAMESPACE optimizes the
 733                          * deletion such that we don't have to perform an entire
 734                          * namespace walk for every control method execution.
 735                          */
 736                         if (method_desc->method.
 737                             info_flags & ACPI_METHOD_MODIFIED_NAMESPACE) {
 738                                 (void)acpi_ex_exit_interpreter();
 739                                 acpi_ns_delete_namespace_by_owner(method_desc->
 740                                                                   method.
 741                                                                   owner_id);
 742                                 (void)acpi_ex_enter_interpreter();
 743                                 method_desc->method.info_flags &=
 744                                     ~ACPI_METHOD_MODIFIED_NAMESPACE;
 745                         }
 746                 }
 747
 748                 /*
 749                  * If method is serialized, release the mutex and restore the
 750                  * current sync level for this thread
 751                  */
 752                 if (method_desc->method.mutex) {
 753
 754                         /* Acquisition Depth handles recursive calls */
 755
 756                         method_desc->method.mutex->mutex.acquisition_depth--;
 757                         if (!method_desc->method.mutex->mutex.acquisition_depth) {
 758                                 walk_state->thread->current_sync_level =
 759                                     method_desc->method.mutex->mutex.
 760                                     original_sync_level;
 761
 762                                 acpi_os_release_mutex(method_desc->method.
 763                                                       mutex->mutex.os_mutex);
 764                                 method_desc->method.mutex->mutex.thread_id = 0;
 765                         }
 766                 }
 767         }
 768
 769         /* Decrement the thread count on the method */
 770
 771         if (method_desc->method.thread_count) {
 772                 method_desc->method.thread_count--;
 773         } else {
 774                 ACPI_ERROR((AE_INFO, "Invalid zero thread count in method"));
 775         }
 776
 777         /* Are there any other threads currently executing this method? */
 778
 779         if (method_desc->method.thread_count) {
 780                 /*
 781                  * Additional threads. Do not release the owner_id in this case,
 782                  * we immediately reuse it for the next thread executing this method
 783                  */
 784                 ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 785                                   "*** Completed execution of one thread, %u threads remaining\n",
 786                                   method_desc->method.thread_count));
 787         } else {
 788                 /* This is the only executing thread for this method */
 789
 790                 /*
 791                  * Support to dynamically change a method from not_serialized to
 792                  * Serialized if it appears that the method is incorrectly written and
 793                  * does not support multiple thread execution. The best example of this
 794                  * is if such a method creates namespace objects and blocks. A second
 795                  * thread will fail with an AE_ALREADY_EXISTS exception.
 796                  *
 797                  * This code is here because we must wait until the last thread exits
 798                  * before marking the method as serialized.
 799                  */
 800                 if (method_desc->method.
 801                     info_flags & ACPI_METHOD_SERIALIZED_PENDING) {
 802                         if (walk_state) {
 803                                 ACPI_INFO(("Marking method %4.4s as Serialized "
 804                                            "because of AE_ALREADY_EXISTS error",
 805                                            walk_state->method_node->name.
 806                                            ascii));
 807                         }
 808
 809                         /*
 810                          * Method tried to create an object twice and was marked as
 811                          * "pending serialized". The probable cause is that the method
 812                          * cannot handle reentrancy.
 813                          *
 814                          * The method was created as not_serialized, but it tried to create
 815                          * a named object and then blocked, causing the second thread
 816                          * entrance to begin and then fail. Workaround this problem by
 817                          * marking the method permanently as Serialized when the last
 818                          * thread exits here.
 819                          */
 820                         method_desc->method.info_flags &=
 821                             ~ACPI_METHOD_SERIALIZED_PENDING;
 822
 823                         method_desc->method.info_flags |=
 824                             (ACPI_METHOD_SERIALIZED |
 825                              ACPI_METHOD_IGNORE_SYNC_LEVEL);
 826                         method_desc->method.sync_level = 0;
 827                 }
 828
 829                 /* No more threads, we can free the owner_id */
 830
 831                 if (!
 832                     (method_desc->method.
 833                      info_flags & ACPI_METHOD_MODULE_LEVEL)) {
 834                         acpi_ut_release_owner_id(&method_desc->method.owner_id);
 835                 }
 836         }
 837
 838         acpi_ex_stop_trace_method((struct acpi_namespace_node *)method_desc->
 839                                   method.node, method_desc, walk_state);
 840
 841         return_VOID;
 842 }