drivers/acpi/acpica/psparse.c

   1 /******************************************************************************
   2  *
   3  * Module Name: psparse - Parser top level AML parse routines
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2008, Intel Corp.
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions, and the following disclaimer,
  16  *    without modification.
  17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  18  *    substantially similar to the "NO WARRANTY" disclaimer below
  19  *    ("Disclaimer") and any redistribution must be conditioned upon
  20  *    including a substantially similar Disclaimer requirement for further
  21  *    binary redistribution.
  22  * 3. Neither the names of the above-listed copyright holders nor the names
  23  *    of any contributors may be used to endorse or promote products derived
  24  *    from this software without specific prior written permission.
  25  *
  26  * Alternatively, this software may be distributed under the terms of the
  27  * GNU General Public License ("GPL") version 2 as published by the Free
  28  * Software Foundation.
  29  *
  30  * NO WARRANTY
  31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
  34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  41  * POSSIBILITY OF SUCH DAMAGES.
  42  */
  43
  44 /*
  45  * Parse the AML and build an operation tree as most interpreters,
  46  * like Perl, do.  Parsing is done by hand rather than with a YACC
  47  * generated parser to tightly constrain stack and dynamic memory
  48  * usage.  At the same time, parsing is kept flexible and the code
  49  * fairly compact by parsing based on a list of AML opcode
  50  * templates in aml_op_info[]
  51  */
  52
  53 #include <acpi/acpi.h>
  54 #include "accommon.h"
  55 #include "acparser.h"
  56 #include "acdispat.h"
  57 #include "amlcode.h"
  58 #include "acnamesp.h"
  59 #include "acinterp.h"
  60
  61 #define _COMPONENT          ACPI_PARSER
  62 ACPI_MODULE_NAME("psparse")
  63
  64 /*******************************************************************************
  65  *
  66  * FUNCTION:    acpi_ps_get_opcode_size
  67  *
  68  * PARAMETERS:  Opcode          - An AML opcode
  69  *
  70  * RETURN:      Size of the opcode, in bytes (1 or 2)
  71  *
  72  * DESCRIPTION: Get the size of the current opcode.
  73  *
  74  ******************************************************************************/
  75 u32 acpi_ps_get_opcode_size(u32 opcode)
  76 {
  77
  78         /* Extended (2-byte) opcode if > 255 */
  79
  80         if (opcode > 0x00FF) {
  81                 return (2);
  82         }
  83
  84         /* Otherwise, just a single byte opcode */
  85
  86         return (1);
  87 }
  88
  89 /*******************************************************************************
  90  *
  91  * FUNCTION:    acpi_ps_peek_opcode
  92  *
  93  * PARAMETERS:  parser_state        - A parser state object
  94  *
  95  * RETURN:      Next AML opcode
  96  *
  97  * DESCRIPTION: Get next AML opcode (without incrementing AML pointer)
  98  *
  99  ******************************************************************************/
 100
 101 u16 acpi_ps_peek_opcode(struct acpi_parse_state * parser_state)
 102 {
 103         u8 *aml;
 104         u16 opcode;
 105
 106         aml = parser_state->aml;
 107         opcode = (u16) ACPI_GET8(aml);
 108
 109         if (opcode == AML_EXTENDED_OP_PREFIX) {
 110
 111                 /* Extended opcode, get the second opcode byte */
 112
 113                 aml++;
 114                 opcode = (u16) ((opcode << 8) | ACPI_GET8(aml));
 115         }
 116
 117         return (opcode);
 118 }
 119
 120 /*******************************************************************************
 121  *
 122  * FUNCTION:    acpi_ps_complete_this_op
 123  *
 124  * PARAMETERS:  walk_state      - Current State
 125  *              Op              - Op to complete
 126  *
 127  * RETURN:      Status
 128  *
 129  * DESCRIPTION: Perform any cleanup at the completion of an Op.
 130  *
 131  ******************************************************************************/
 132
 133 acpi_status
 134 acpi_ps_complete_this_op(struct acpi_walk_state * walk_state,
 135                          union acpi_parse_object * op)
 136 {
 137         union acpi_parse_object *prev;
 138         union acpi_parse_object *next;
 139         const struct acpi_opcode_info *parent_info;
 140         union acpi_parse_object *replacement_op = NULL;
 141         acpi_status status = AE_OK;
 142
 143         ACPI_FUNCTION_TRACE_PTR(ps_complete_this_op, op);
 144
 145         /* Check for null Op, can happen if AML code is corrupt */
 146
 147         if (!op) {
 148                 return_ACPI_STATUS(AE_OK);      /* OK for now */
 149         }
 150
 151         /* Delete this op and the subtree below it if asked to */
 152
 153         if (((walk_state->parse_flags & ACPI_PARSE_TREE_MASK) !=
 154              ACPI_PARSE_DELETE_TREE)
 155             || (walk_state->op_info->class == AML_CLASS_ARGUMENT)) {
 156                 return_ACPI_STATUS(AE_OK);
 157         }
 158
 159         /* Make sure that we only delete this subtree */
 160
 161         if (op->common.parent) {
 162                 prev = op->common.parent->common.value.arg;
 163                 if (!prev) {
 164
 165                         /* Nothing more to do */
 166
 167                         goto cleanup;
 168                 }
 169
 170                 /*
 171                  * Check if we need to replace the operator and its subtree
 172                  * with a return value op (placeholder op)
 173                  */
 174                 parent_info =
 175                     acpi_ps_get_opcode_info(op->common.parent->common.
 176                                             aml_opcode);
 177
 178                 switch (parent_info->class) {
 179                 case AML_CLASS_CONTROL:
 180                         break;
 181
 182                 case AML_CLASS_CREATE:
 183
 184                         /*
 185                          * These opcodes contain term_arg operands. The current
 186                          * op must be replaced by a placeholder return op
 187                          */
 188                         replacement_op =
 189                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP);
 190                         if (!replacement_op) {
 191                                 status = AE_NO_MEMORY;
 192                         }
 193                         break;
 194
 195                 case AML_CLASS_NAMED_OBJECT:
 196
 197                         /*
 198                          * These opcodes contain term_arg operands. The current
 199                          * op must be replaced by a placeholder return op
 200                          */
 201                         if ((op->common.parent->common.aml_opcode ==
 202                              AML_REGION_OP)
 203                             || (op->common.parent->common.aml_opcode ==
 204                                 AML_DATA_REGION_OP)
 205                             || (op->common.parent->common.aml_opcode ==
 206                                 AML_BUFFER_OP)
 207                             || (op->common.parent->common.aml_opcode ==
 208                                 AML_PACKAGE_OP)
 209                             || (op->common.parent->common.aml_opcode ==
 210                                 AML_BANK_FIELD_OP)
 211                             || (op->common.parent->common.aml_opcode ==
 212                                 AML_VAR_PACKAGE_OP)) {
 213                                 replacement_op =
 214                                     acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP);
 215                                 if (!replacement_op) {
 216                                         status = AE_NO_MEMORY;
 217                                 }
 218                         } else
 219                             if ((op->common.parent->common.aml_opcode ==
 220                                  AML_NAME_OP)
 221                                 && (walk_state->pass_number <=
 222                                     ACPI_IMODE_LOAD_PASS2)) {
 223                                 if ((op->common.aml_opcode == AML_BUFFER_OP)
 224                                     || (op->common.aml_opcode == AML_PACKAGE_OP)
 225                                     || (op->common.aml_opcode ==
 226                                         AML_VAR_PACKAGE_OP)) {
 227                                         replacement_op =
 228                                             acpi_ps_alloc_op(op->common.
 229                                                              aml_opcode);
 230                                         if (!replacement_op) {
 231                                                 status = AE_NO_MEMORY;
 232                                         } else {
 233                                                 replacement_op->named.data =
 234                                                     op->named.data;
 235                                                 replacement_op->named.length =
 236                                                     op->named.length;
 237                                         }
 238                                 }
 239                         }
 240                         break;
 241
 242                 default:
 243
 244                         replacement_op =
 245                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP);
 246                         if (!replacement_op) {
 247                                 status = AE_NO_MEMORY;
 248                         }
 249                 }
 250
 251                 /* We must unlink this op from the parent tree */
 252
 253                 if (prev == op) {
 254
 255                         /* This op is the first in the list */
 256
 257                         if (replacement_op) {
 258                                 replacement_op->common.parent =
 259                                     op->common.parent;
 260                                 replacement_op->common.value.arg = NULL;
 261                                 replacement_op->common.node = op->common.node;
 262                                 op->common.parent->common.value.arg =
 263                                     replacement_op;
 264                                 replacement_op->common.next = op->common.next;
 265                         } else {
 266                                 op->common.parent->common.value.arg =
 267                                     op->common.next;
 268                         }
 269                 }
 270
 271                 /* Search the parent list */
 272
 273                 else
 274                         while (prev) {
 275
 276                                 /* Traverse all siblings in the parent's argument list */
 277
 278                                 next = prev->common.next;
 279                                 if (next == op) {
 280                                         if (replacement_op) {
 281                                                 replacement_op->common.parent =
 282                                                     op->common.parent;
 283                                                 replacement_op->common.value.
 284                                                     arg = NULL;
 285                                                 replacement_op->common.node =
 286                                                     op->common.node;
 287                                                 prev->common.next =
 288                                                     replacement_op;
 289                                                 replacement_op->common.next =
 290                                                     op->common.next;
 291                                                 next = NULL;
 292                                         } else {
 293                                                 prev->common.next =
 294                                                     op->common.next;
 295                                                 next = NULL;
 296                                         }
 297                                 }
 298                                 prev = next;
 299                         }
 300         }
 301
 302       cleanup:
 303
 304         /* Now we can actually delete the subtree rooted at Op */
 305
 306         acpi_ps_delete_parse_tree(op);
 307         return_ACPI_STATUS(status);
 308 }
 309
 310 /*******************************************************************************
 311  *
 312  * FUNCTION:    acpi_ps_next_parse_state
 313  *
 314  * PARAMETERS:  walk_state          - Current state
 315  *              Op                  - Current parse op
 316  *              callback_status     - Status from previous operation
 317  *
 318  * RETURN:      Status
 319  *
 320  * DESCRIPTION: Update the parser state based upon the return exception from
 321  *              the parser callback.
 322  *
 323  ******************************************************************************/
 324
 325 acpi_status
 326 acpi_ps_next_parse_state(struct acpi_walk_state *walk_state,
 327                          union acpi_parse_object *op,
 328                          acpi_status callback_status)
 329 {
 330         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 331         acpi_status status = AE_CTRL_PENDING;
 332
 333         ACPI_FUNCTION_TRACE_PTR(ps_next_parse_state, op);
 334
 335         switch (callback_status) {
 336         case AE_CTRL_TERMINATE:
 337                 /*
 338                  * A control method was terminated via a RETURN statement.
 339                  * The walk of this method is complete.
 340                  */
 341                 parser_state->aml = parser_state->aml_end;
 342                 status = AE_CTRL_TERMINATE;
 343                 break;
 344
 345         case AE_CTRL_BREAK:
 346
 347                 parser_state->aml = walk_state->aml_last_while;
 348                 walk_state->control_state->common.value = FALSE;
 349                 status = AE_CTRL_BREAK;
 350                 break;
 351
 352         case AE_CTRL_CONTINUE:
 353
 354                 parser_state->aml = walk_state->aml_last_while;
 355                 status = AE_CTRL_CONTINUE;
 356                 break;
 357
 358         case AE_CTRL_PENDING:
 359
 360                 parser_state->aml = walk_state->aml_last_while;
 361                 break;
 362
 363 #if 0
 364         case AE_CTRL_SKIP:
 365
 366                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 367                 status = AE_OK;
 368                 break;
 369 #endif
 370
 371         case AE_CTRL_TRUE:
 372                 /*
 373                  * Predicate of an IF was true, and we are at the matching ELSE.
 374                  * Just close out this package
 375                  */
 376                 parser_state->aml = acpi_ps_get_next_package_end(parser_state);
 377                 status = AE_CTRL_PENDING;
 378                 break;
 379
 380         case AE_CTRL_FALSE:
 381                 /*
 382                  * Either an IF/WHILE Predicate was false or we encountered a BREAK
 383                  * opcode.  In both cases, we do not execute the rest of the
 384                  * package;  We simply close out the parent (finishing the walk of
 385                  * this branch of the tree) and continue execution at the parent
 386                  * level.
 387                  */
 388                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 389
 390                 /* In the case of a BREAK, just force a predicate (if any) to FALSE */
 391
 392                 walk_state->control_state->common.value = FALSE;
 393                 status = AE_CTRL_END;
 394                 break;
 395
 396         case AE_CTRL_TRANSFER:
 397
 398                 /* A method call (invocation) -- transfer control */
 399
 400                 status = AE_CTRL_TRANSFER;
 401                 walk_state->prev_op = op;
 402                 walk_state->method_call_op = op;
 403                 walk_state->method_call_node =
 404                     (op->common.value.arg)->common.node;
 405
 406                 /* Will return value (if any) be used by the caller? */
 407
 408                 walk_state->return_used =
 409                     acpi_ds_is_result_used(op, walk_state);
 410                 break;
 411
 412         default:
 413
 414                 status = callback_status;
 415                 if ((callback_status & AE_CODE_MASK) == AE_CODE_CONTROL) {
 416                         status = AE_OK;
 417                 }
 418                 break;
 419         }
 420
 421         return_ACPI_STATUS(status);
 422 }
 423
 424 /*******************************************************************************
 425  *
 426  * FUNCTION:    acpi_ps_parse_aml
 427  *
 428  * PARAMETERS:  walk_state      - Current state
 429  *
 430  *
 431  * RETURN:      Status
 432  *
 433  * DESCRIPTION: Parse raw AML and return a tree of ops
 434  *
 435  ******************************************************************************/
 436
 437 acpi_status acpi_ps_parse_aml(struct acpi_walk_state *walk_state)
 438 {
 439         acpi_status status;
 440         struct acpi_thread_state *thread;
 441         struct acpi_thread_state *prev_walk_list = acpi_gbl_current_walk_list;
 442         struct acpi_walk_state *previous_walk_state;
 443
 444         ACPI_FUNCTION_TRACE(ps_parse_aml);
 445
 446         ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 447                           "Entered with WalkState=%p Aml=%p size=%X\n",
 448                           walk_state, walk_state->parser_state.aml,
 449                           walk_state->parser_state.aml_size));
 450
 451         if (!walk_state->parser_state.aml) {
 452                 return_ACPI_STATUS(AE_NULL_OBJECT);
 453         }
 454
 455         /* Create and initialize a new thread state */
 456
 457         thread = acpi_ut_create_thread_state();
 458         if (!thread) {
 459                 if (walk_state->method_desc) {
 460
 461                         /* Executing a control method - additional cleanup */
 462
 463                         acpi_ds_terminate_control_method(
 464                                 walk_state->method_desc, walk_state);
 465                 }
 466
 467                 acpi_ds_delete_walk_state(walk_state);
 468                 return_ACPI_STATUS(AE_NO_MEMORY);
 469         }
 470
 471         walk_state->thread = thread;
 472
 473         /*
 474          * If executing a method, the starting sync_level is this method's
 475          * sync_level
 476          */
 477         if (walk_state->method_desc) {
 478                 walk_state->thread->current_sync_level =
 479                     walk_state->method_desc->method.sync_level;
 480         }
 481
 482         acpi_ds_push_walk_state(walk_state, thread);
 483
 484         /*
 485          * This global allows the AML debugger to get a handle to the currently
 486          * executing control method.
 487          */
 488         acpi_gbl_current_walk_list = thread;
 489
 490         /*
 491          * Execute the walk loop as long as there is a valid Walk State.  This
 492          * handles nested control method invocations without recursion.
 493          */
 494         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "State=%p\n", walk_state));
 495
 496         status = AE_OK;
 497         while (walk_state) {
 498                 if (ACPI_SUCCESS(status)) {
 499                         /*
 500                          * The parse_loop executes AML until the method terminates
 501                          * or calls another method.
 502                          */
 503                         status = acpi_ps_parse_loop(walk_state);
 504                 }
 505
 506                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 507                                   "Completed one call to walk loop, %s State=%p\n",
 508                                   acpi_format_exception(status), walk_state));
 509
 510                 if (status == AE_CTRL_TRANSFER) {
 511                         /*
 512                          * A method call was detected.
 513                          * Transfer control to the called control method
 514                          */
 515                         status =
 516                             acpi_ds_call_control_method(thread, walk_state,
 517                                                         NULL);
 518                         if (ACPI_FAILURE(status)) {
 519                                 status =
 520                                     acpi_ds_method_error(status, walk_state);
 521                         }
 522
 523                         /*
 524                          * If the transfer to the new method method call worked, a new walk
 525                          * state was created -- get it
 526                          */
 527                         walk_state = acpi_ds_get_current_walk_state(thread);
 528                         continue;
 529                 } else if (status == AE_CTRL_TERMINATE) {
 530                         status = AE_OK;
 531                 } else if ((status != AE_OK) && (walk_state->method_desc)) {
 532
 533                         /* Either the method parse or actual execution failed */
 534
 535                         ACPI_ERROR_METHOD("Method parse/execution failed",
 536                                           walk_state->method_node, NULL,
 537                                           status);
 538
 539                         /* Check for possible multi-thread reentrancy problem */
 540
 541                         if ((status == AE_ALREADY_EXISTS) &&
 542                             (!walk_state->method_desc->method.mutex)) {
 543                                 ACPI_INFO((AE_INFO,
 544                                            "Marking method %4.4s as Serialized because of AE_ALREADY_EXISTS error",
 545                                            walk_state->method_node->name.
 546                                            ascii));
 547
 548                                 /*
 549                                  * Method tried to create an object twice. The probable cause is
 550                                  * that the method cannot handle reentrancy.
 551                                  *
 552                                  * The method is marked not_serialized, but it tried to create
 553                                  * a named object, causing the second thread entrance to fail.
 554                                  * Workaround this problem by marking the method permanently
 555                                  * as Serialized.
 556                                  */
 557                                 walk_state->method_desc->method.method_flags |=
 558                                     AML_METHOD_SERIALIZED;
 559                                 walk_state->method_desc->method.sync_level = 0;
 560                         }
 561                 }
 562
 563                 /* We are done with this walk, move on to the parent if any */
 564
 565                 walk_state = acpi_ds_pop_walk_state(thread);
 566
 567                 /* Reset the current scope to the beginning of scope stack */
 568
 569                 acpi_ds_scope_stack_clear(walk_state);
 570
 571                 /*
 572                  * If we just returned from the execution of a control method or if we
 573                  * encountered an error during the method parse phase, there's lots of
 574                  * cleanup to do
 575                  */
 576                 if (((walk_state->parse_flags & ACPI_PARSE_MODE_MASK) ==
 577                      ACPI_PARSE_EXECUTE) || (ACPI_FAILURE(status))) {
 578                         acpi_ds_terminate_control_method(walk_state->
 579                                                          method_desc,
 580                                                          walk_state);
 581                 }
 582
 583                 /* Delete this walk state and all linked control states */
 584
 585                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 586                 previous_walk_state = walk_state;
 587
 588                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 589                                   "ReturnValue=%p, ImplicitValue=%p State=%p\n",
 590                                   walk_state->return_desc,
 591                                   walk_state->implicit_return_obj, walk_state));
 592
 593                 /* Check if we have restarted a preempted walk */
 594
 595                 walk_state = acpi_ds_get_current_walk_state(thread);
 596                 if (walk_state) {
 597                         if (ACPI_SUCCESS(status)) {
 598                                 /*
 599                                  * There is another walk state, restart it.
 600                                  * If the method return value is not used by the parent,
 601                                  * The object is deleted
 602                                  */
 603                                 if (!previous_walk_state->return_desc) {
 604                                         /*
 605                                          * In slack mode execution, if there is no return value
 606                                          * we should implicitly return zero (0) as a default value.
 607                                          */
 608                                         if (acpi_gbl_enable_interpreter_slack &&
 609                                             !previous_walk_state->
 610                                             implicit_return_obj) {
 611                                                 previous_walk_state->
 612                                                     implicit_return_obj =
 613                                                     acpi_ut_create_internal_object
 614                                                     (ACPI_TYPE_INTEGER);
 615                                                 if (!previous_walk_state->
 616                                                     implicit_return_obj) {
 617                                                         return_ACPI_STATUS
 618                                                             (AE_NO_MEMORY);
 619                                                 }
 620
 621                                                 previous_walk_state->
 622                                                     implicit_return_obj->
 623                                                     integer.value = 0;
 624                                         }
 625
 626                                         /* Restart the calling control method */
 627
 628                                         status =
 629                                             acpi_ds_restart_control_method
 630                                             (walk_state,
 631                                              previous_walk_state->
 632                                              implicit_return_obj);
 633                                 } else {
 634                                         /*
 635                                          * We have a valid return value, delete any implicit
 636                                          * return value.
 637                                          */
 638                                         acpi_ds_clear_implicit_return
 639                                             (previous_walk_state);
 640
 641                                         status =
 642                                             acpi_ds_restart_control_method
 643                                             (walk_state,
 644                                              previous_walk_state->return_desc);
 645                                 }
 646                                 if (ACPI_SUCCESS(status)) {
 647                                         walk_state->walk_type |=
 648                                             ACPI_WALK_METHOD_RESTART;
 649                                 }
 650                         } else {
 651                                 /* On error, delete any return object or implicit return */
 652
 653                                 acpi_ut_remove_reference(previous_walk_state->
 654                                                          return_desc);
 655                                 acpi_ds_clear_implicit_return
 656                                     (previous_walk_state);
 657                         }
 658                 }
 659
 660                 /*
 661                  * Just completed a 1st-level method, save the final internal return
 662                  * value (if any)
 663                  */
 664                 else if (previous_walk_state->caller_return_desc) {
 665                         if (previous_walk_state->implicit_return_obj) {
 666                                 *(previous_walk_state->caller_return_desc) =
 667                                     previous_walk_state->implicit_return_obj;
 668                         } else {
 669                                 /* NULL if no return value */
 670
 671                                 *(previous_walk_state->caller_return_desc) =
 672                                     previous_walk_state->return_desc;
 673                         }
 674                 } else {
 675                         if (previous_walk_state->return_desc) {
 676
 677                                 /* Caller doesn't want it, must delete it */
 678
 679                                 acpi_ut_remove_reference(previous_walk_state->
 680                                                          return_desc);
 681                         }
 682                         if (previous_walk_state->implicit_return_obj) {
 683
 684                                 /* Caller doesn't want it, must delete it */
 685
 686                                 acpi_ut_remove_reference(previous_walk_state->
 687                                                          implicit_return_obj);
 688                         }
 689                 }
 690
 691                 acpi_ds_delete_walk_state(previous_walk_state);
 692         }
 693
 694         /* Normal exit */
 695
 696         acpi_ex_release_all_mutexes(thread);
 697         acpi_ut_delete_generic_state(ACPI_CAST_PTR
 698                                      (union acpi_generic_state, thread));
 699         acpi_gbl_current_walk_list = prev_walk_list;
 700         return_ACPI_STATUS(status);
 701 }