drivers/acpi/dispatcher/dsmethod.c

   1 /******************************************************************************
   2  *
   3  * Module Name: dsmethod - Parser/Interpreter interface - control method parsing
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2006, R. Byron Moore
   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 #include <acpi/acpi.h>
  45 #include <acpi/acparser.h>
  46 #include <acpi/amlcode.h>
  47 #include <acpi/acdispat.h>
  48 #include <acpi/acinterp.h>
  49 #include <acpi/acnamesp.h>
  50 #include <acpi/acdisasm.h>
  51
  52 #define _COMPONENT          ACPI_DISPATCHER
  53 ACPI_MODULE_NAME("dsmethod")
  54
  55 /* Local prototypes */
  56 static acpi_status
  57 acpi_ds_create_method_mutex(union acpi_operand_object *method_desc);
  58
  59 /*******************************************************************************
  60  *
  61  * FUNCTION:    acpi_ds_method_error
  62  *
  63  * PARAMETERS:  Status          - Execution status
  64  *              walk_state      - Current state
  65  *
  66  * RETURN:      Status
  67  *
  68  * DESCRIPTION: Called on method error. Invoke the global exception handler if
  69  *              present, dump the method data if the disassembler is configured
  70  *
  71  *              Note: Allows the exception handler to change the status code
  72  *
  73  ******************************************************************************/
  74
  75 acpi_status
  76 acpi_ds_method_error(acpi_status status, struct acpi_walk_state *walk_state)
  77 {
  78         ACPI_FUNCTION_ENTRY();
  79
  80         /* Ignore AE_OK and control exception codes */
  81
  82         if (ACPI_SUCCESS(status) || (status & AE_CODE_CONTROL)) {
  83                 return (status);
  84         }
  85
  86         /* Invoke the global exception handler */
  87
  88         if (acpi_gbl_exception_handler) {
  89
  90                 /* Exit the interpreter, allow handler to execute methods */
  91
  92                 acpi_ex_exit_interpreter();
  93
  94                 /*
  95                  * Handler can map the exception code to anything it wants, including
  96                  * AE_OK, in which case the executing method will not be aborted.
  97                  */
  98                 status = acpi_gbl_exception_handler(status,
  99                                                     walk_state->method_node ?
 100                                                     walk_state->method_node->
 101                                                     name.integer : 0,
 102                                                     walk_state->opcode,
 103                                                     walk_state->aml_offset,
 104                                                     NULL);
 105                 (void)acpi_ex_enter_interpreter();
 106         }
 107 #ifdef ACPI_DISASSEMBLER
 108         if (ACPI_FAILURE(status)) {
 109
 110                 /* Display method locals/args if disassembler is present */
 111
 112                 acpi_dm_dump_method_info(status, walk_state, walk_state->op);
 113         }
 114 #endif
 115
 116         return (status);
 117 }
 118
 119 /*******************************************************************************
 120  *
 121  * FUNCTION:    acpi_ds_create_method_mutex
 122  *
 123  * PARAMETERS:  obj_desc            - The method object
 124  *
 125  * RETURN:      Status
 126  *
 127  * DESCRIPTION: Create a mutex object for a serialized control method
 128  *
 129  ******************************************************************************/
 130
 131 static acpi_status
 132 acpi_ds_create_method_mutex(union acpi_operand_object *method_desc)
 133 {
 134         union acpi_operand_object *mutex_desc;
 135         acpi_status status;
 136
 137         ACPI_FUNCTION_TRACE(ds_create_method_mutex);
 138
 139         /* Create the new mutex object */
 140
 141         mutex_desc = acpi_ut_create_internal_object(ACPI_TYPE_MUTEX);
 142         if (!mutex_desc) {
 143                 return_ACPI_STATUS(AE_NO_MEMORY);
 144         }
 145
 146         /* Create the actual OS Mutex */
 147
 148         status = acpi_os_create_mutex(&mutex_desc->mutex.os_mutex);
 149         if (ACPI_FAILURE(status)) {
 150                 return_ACPI_STATUS(status);
 151         }
 152
 153         mutex_desc->mutex.sync_level = method_desc->method.sync_level;
 154         method_desc->method.mutex = mutex_desc;
 155         return_ACPI_STATUS(AE_OK);
 156 }
 157
 158 /*******************************************************************************
 159  *
 160  * FUNCTION:    acpi_ds_begin_method_execution
 161  *
 162  * PARAMETERS:  method_node         - Node of the method
 163  *              obj_desc            - The method object
 164  *              walk_state          - current state, NULL if not yet executing
 165  *                                    a method.
 166  *
 167  * RETURN:      Status
 168  *
 169  * DESCRIPTION: Prepare a method for execution.  Parses the method if necessary,
 170  *              increments the thread count, and waits at the method semaphore
 171  *              for clearance to execute.
 172  *
 173  ******************************************************************************/
 174
 175 acpi_status
 176 acpi_ds_begin_method_execution(struct acpi_namespace_node *method_node,
 177                                union acpi_operand_object *obj_desc,
 178                                struct acpi_walk_state *walk_state)
 179 {
 180         acpi_status status = AE_OK;
 181
 182         ACPI_FUNCTION_TRACE_PTR(ds_begin_method_execution, method_node);
 183
 184         if (!method_node) {
 185                 return_ACPI_STATUS(AE_NULL_ENTRY);
 186         }
 187
 188         /* Prevent wraparound of thread count */
 189
 190         if (obj_desc->method.thread_count == ACPI_UINT8_MAX) {
 191                 ACPI_ERROR((AE_INFO,
 192                             "Method reached maximum reentrancy limit (255)"));
 193                 return_ACPI_STATUS(AE_AML_METHOD_LIMIT);
 194         }
 195
 196         /*
 197          * If this method is serialized, we need to acquire the method mutex.
 198          */
 199         if (obj_desc->method.method_flags & AML_METHOD_SERIALIZED) {
 200                 /*
 201                  * Create a mutex for the method if it is defined to be Serialized
 202                  * and a mutex has not already been created. We defer the mutex creation
 203                  * until a method is actually executed, to minimize the object count
 204                  */
 205                 if (!obj_desc->method.mutex) {
 206                         status = acpi_ds_create_method_mutex(obj_desc);
 207                         if (ACPI_FAILURE(status)) {
 208                                 return_ACPI_STATUS(status);
 209                         }
 210                 }
 211
 212                 /*
 213                  * The current_sync_level (per-thread) must be less than or equal to
 214                  * the sync level of the method. This mechanism provides some
 215                  * deadlock prevention
 216                  *
 217                  * Top-level method invocation has no walk state at this point
 218                  */
 219                 if (walk_state &&
 220                     (walk_state->thread->current_sync_level >
 221                      obj_desc->method.mutex->mutex.sync_level)) {
 222                         ACPI_ERROR((AE_INFO,
 223                                     "Cannot acquire Mutex for method [%4.4s], current SyncLevel is too large (%d)",
 224                                     acpi_ut_get_node_name(method_node),
 225                                     walk_state->thread->current_sync_level));
 226
 227                         return_ACPI_STATUS(AE_AML_MUTEX_ORDER);
 228                 }
 229
 230                 /*
 231                  * Obtain the method mutex if necessary. Do not acquire mutex for a
 232                  * recursive call.
 233                  */
 234                 if (!walk_state ||
 235                     !obj_desc->method.mutex->mutex.owner_thread ||
 236                     (walk_state->thread !=
 237                      obj_desc->method.mutex->mutex.owner_thread)) {
 238                         /*
 239                          * Acquire the method mutex. This releases the interpreter if we
 240                          * block (and reacquires it before it returns)
 241                          */
 242                         status =
 243                             acpi_ex_system_wait_mutex(obj_desc->method.mutex->
 244                                                       mutex.os_mutex,
 245                                                       ACPI_WAIT_FOREVER);
 246                         if (ACPI_FAILURE(status)) {
 247                                 return_ACPI_STATUS(status);
 248                         }
 249
 250                         /* Update the mutex and walk info and save the original sync_level */
 251
 252                         if (walk_state) {
 253                                 obj_desc->method.mutex->mutex.
 254                                     original_sync_level =
 255                                     walk_state->thread->current_sync_level;
 256
 257                                 obj_desc->method.mutex->mutex.owner_thread =
 258                                     walk_state->thread;
 259                                 walk_state->thread->current_sync_level =
 260                                     obj_desc->method.sync_level;
 261                         } else {
 262                                 obj_desc->method.mutex->mutex.
 263                                     original_sync_level =
 264                                     obj_desc->method.mutex->mutex.sync_level;
 265                         }
 266                 }
 267
 268                 /* Always increase acquisition depth */
 269
 270                 obj_desc->method.mutex->mutex.acquisition_depth++;
 271         }
 272
 273         /*
 274          * Allocate an Owner ID for this method, only if this is the first thread
 275          * to begin concurrent execution. We only need one owner_id, even if the
 276          * method is invoked recursively.
 277          */
 278         if (!obj_desc->method.owner_id) {
 279                 status = acpi_ut_allocate_owner_id(&obj_desc->method.owner_id);
 280                 if (ACPI_FAILURE(status)) {
 281                         goto cleanup;
 282                 }
 283         }
 284
 285         /*
 286          * Increment the method parse tree thread count since it has been
 287          * reentered one more time (even if it is the same thread)
 288          */
 289         obj_desc->method.thread_count++;
 290         return_ACPI_STATUS(status);
 291
 292       cleanup:
 293         /* On error, must release the method mutex (if present) */
 294
 295         if (obj_desc->method.mutex) {
 296                 acpi_os_release_mutex(obj_desc->method.mutex->mutex.os_mutex);
 297         }
 298         return_ACPI_STATUS(status);
 299 }
 300
 301 /*******************************************************************************
 302  *
 303  * FUNCTION:    acpi_ds_call_control_method
 304  *
 305  * PARAMETERS:  Thread              - Info for this thread
 306  *              this_walk_state     - Current walk state
 307  *              Op                  - Current Op to be walked
 308  *
 309  * RETURN:      Status
 310  *
 311  * DESCRIPTION: Transfer execution to a called control method
 312  *
 313  ******************************************************************************/
 314
 315 acpi_status
 316 acpi_ds_call_control_method(struct acpi_thread_state *thread,
 317                             struct acpi_walk_state *this_walk_state,
 318                             union acpi_parse_object *op)
 319 {
 320         acpi_status status;
 321         struct acpi_namespace_node *method_node;
 322         struct acpi_walk_state *next_walk_state = NULL;
 323         union acpi_operand_object *obj_desc;
 324         struct acpi_evaluate_info *info;
 325         u32 i;
 326
 327         ACPI_FUNCTION_TRACE_PTR(ds_call_control_method, this_walk_state);
 328
 329         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 330                           "Execute method %p, currentstate=%p\n",
 331                           this_walk_state->prev_op, this_walk_state));
 332
 333         /*
 334          * Get the namespace entry for the control method we are about to call
 335          */
 336         method_node = this_walk_state->method_call_node;
 337         if (!method_node) {
 338                 return_ACPI_STATUS(AE_NULL_ENTRY);
 339         }
 340
 341         obj_desc = acpi_ns_get_attached_object(method_node);
 342         if (!obj_desc) {
 343                 return_ACPI_STATUS(AE_NULL_OBJECT);
 344         }
 345
 346         /* Init for new method, possibly wait on method mutex */
 347
 348         status = acpi_ds_begin_method_execution(method_node, obj_desc,
 349                                                 this_walk_state);
 350         if (ACPI_FAILURE(status)) {
 351                 return_ACPI_STATUS(status);
 352         }
 353
 354         /*
 355          * 1) Parse the method. All "normal" methods are parsed for each execution.
 356          * Internal methods (_OSI, etc.) do not require parsing.
 357          */
 358         if (!(obj_desc->method.method_flags & AML_METHOD_INTERNAL_ONLY)) {
 359
 360                 /* Create a new walk state for the parse */
 361
 362                 next_walk_state =
 363                     acpi_ds_create_walk_state(obj_desc->method.owner_id, op,
 364                                               obj_desc, NULL);
 365                 if (!next_walk_state) {
 366                         status = AE_NO_MEMORY;
 367                         goto cleanup;
 368                 }
 369
 370                 /* Create and init a parse tree root */
 371
 372                 op = acpi_ps_create_scope_op();
 373                 if (!op) {
 374                         status = AE_NO_MEMORY;
 375                         goto cleanup;
 376                 }
 377
 378                 status = acpi_ds_init_aml_walk(next_walk_state, op, method_node,
 379                                                obj_desc->method.aml_start,
 380                                                obj_desc->method.aml_length,
 381                                                NULL, 1);
 382                 if (ACPI_FAILURE(status)) {
 383                         acpi_ps_delete_parse_tree(op);
 384                         goto cleanup;
 385                 }
 386
 387                 /* Begin AML parse (deletes next_walk_state) */
 388
 389                 status = acpi_ps_parse_aml(next_walk_state);
 390                 acpi_ps_delete_parse_tree(op);
 391                 if (ACPI_FAILURE(status)) {
 392                         goto cleanup;
 393                 }
 394         }
 395
 396         /* 2) Begin method execution. Create a new walk state */
 397
 398         next_walk_state = acpi_ds_create_walk_state(obj_desc->method.owner_id,
 399                                                     NULL, obj_desc, thread);
 400         if (!next_walk_state) {
 401                 status = AE_NO_MEMORY;
 402                 goto cleanup;
 403         }
 404
 405         /*
 406          * The resolved arguments were put on the previous walk state's operand
 407          * stack. Operands on the previous walk state stack always
 408          * start at index 0. Also, null terminate the list of arguments
 409          */
 410         this_walk_state->operands[this_walk_state->num_operands] = NULL;
 411
 412         /*
 413          * Allocate and initialize the evaluation information block
 414          * TBD: this is somewhat inefficient, should change interface to
 415          * ds_init_aml_walk. For now, keeps this struct off the CPU stack
 416          */
 417         info = ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_evaluate_info));
 418         if (!info) {
 419                 return_ACPI_STATUS(AE_NO_MEMORY);
 420         }
 421
 422         info->parameters = &this_walk_state->operands[0];
 423         info->parameter_type = ACPI_PARAM_ARGS;
 424
 425         status = acpi_ds_init_aml_walk(next_walk_state, NULL, method_node,
 426                                        obj_desc->method.aml_start,
 427                                        obj_desc->method.aml_length, info, 3);
 428
 429         ACPI_FREE(info);
 430         if (ACPI_FAILURE(status)) {
 431                 goto cleanup;
 432         }
 433
 434         /*
 435          * Delete the operands on the previous walkstate operand stack
 436          * (they were copied to new objects)
 437          */
 438         for (i = 0; i < obj_desc->method.param_count; i++) {
 439                 acpi_ut_remove_reference(this_walk_state->operands[i]);
 440                 this_walk_state->operands[i] = NULL;
 441         }
 442
 443         /* Clear the operand stack */
 444
 445         this_walk_state->num_operands = 0;
 446
 447         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 448                           "Starting nested execution, newstate=%p\n",
 449                           next_walk_state));
 450
 451         /* Invoke an internal method if necessary */
 452
 453         if (obj_desc->method.method_flags & AML_METHOD_INTERNAL_ONLY) {
 454                 status = obj_desc->method.implementation(next_walk_state);
 455         }
 456
 457         return_ACPI_STATUS(status);
 458
 459       cleanup:
 460
 461         /* On error, we must terminate the method properly */
 462
 463         acpi_ds_terminate_control_method(obj_desc, next_walk_state);
 464         if (next_walk_state) {
 465                 acpi_ds_delete_walk_state(next_walk_state);
 466         }
 467
 468         return_ACPI_STATUS(status);
 469 }
 470
 471 /*******************************************************************************
 472  *
 473  * FUNCTION:    acpi_ds_restart_control_method
 474  *
 475  * PARAMETERS:  walk_state          - State for preempted method (caller)
 476  *              return_desc         - Return value from the called method
 477  *
 478  * RETURN:      Status
 479  *
 480  * DESCRIPTION: Restart a method that was preempted by another (nested) method
 481  *              invocation.  Handle the return value (if any) from the callee.
 482  *
 483  ******************************************************************************/
 484
 485 acpi_status
 486 acpi_ds_restart_control_method(struct acpi_walk_state *walk_state,
 487                                union acpi_operand_object *return_desc)
 488 {
 489         acpi_status status;
 490         int same_as_implicit_return;
 491
 492         ACPI_FUNCTION_TRACE_PTR(ds_restart_control_method, walk_state);
 493
 494         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 495                           "****Restart [%4.4s] Op %p ReturnValueFromCallee %p\n",
 496                           acpi_ut_get_node_name(walk_state->method_node),
 497                           walk_state->method_call_op, return_desc));
 498
 499         ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 500                           "    ReturnFromThisMethodUsed?=%X ResStack %p Walk %p\n",
 501                           walk_state->return_used,
 502                           walk_state->results, walk_state));
 503
 504         /* Did the called method return a value? */
 505
 506         if (return_desc) {
 507
 508                 /* Is the implicit return object the same as the return desc? */
 509
 510                 same_as_implicit_return =
 511                     (walk_state->implicit_return_obj == return_desc);
 512
 513                 /* Are we actually going to use the return value? */
 514
 515                 if (walk_state->return_used) {
 516
 517                         /* Save the return value from the previous method */
 518
 519                         status = acpi_ds_result_push(return_desc, walk_state);
 520                         if (ACPI_FAILURE(status)) {
 521                                 acpi_ut_remove_reference(return_desc);
 522                                 return_ACPI_STATUS(status);
 523                         }
 524
 525                         /*
 526                          * Save as THIS method's return value in case it is returned
 527                          * immediately to yet another method
 528                          */
 529                         walk_state->return_desc = return_desc;
 530                 }
 531
 532                 /*
 533                  * The following code is the optional support for the so-called
 534                  * "implicit return". Some AML code assumes that the last value of the
 535                  * method is "implicitly" returned to the caller, in the absence of an
 536                  * explicit return value.
 537                  *
 538                  * Just save the last result of the method as the return value.
 539                  *
 540                  * NOTE: this is optional because the ASL language does not actually
 541                  * support this behavior.
 542                  */
 543                 else if (!acpi_ds_do_implicit_return
 544                          (return_desc, walk_state, FALSE)
 545                          || same_as_implicit_return) {
 546                         /*
 547                          * Delete the return value if it will not be used by the
 548                          * calling method or remove one reference if the explicit return
 549                          * is the same as the implicit return value.
 550                          */
 551                         acpi_ut_remove_reference(return_desc);
 552                 }
 553         }
 554
 555         return_ACPI_STATUS(AE_OK);
 556 }
 557
 558 /*******************************************************************************
 559  *
 560  * FUNCTION:    acpi_ds_terminate_control_method
 561  *
 562  * PARAMETERS:  method_desc         - Method object
 563  *              walk_state          - State associated with the method
 564  *
 565  * RETURN:      None
 566  *
 567  * DESCRIPTION: Terminate a control method.  Delete everything that the method
 568  *              created, delete all locals and arguments, and delete the parse
 569  *              tree if requested.
 570  *
 571  * MUTEX:       Interpreter is locked
 572  *
 573  ******************************************************************************/
 574
 575 void
 576 acpi_ds_terminate_control_method(union acpi_operand_object *method_desc,
 577                                  struct acpi_walk_state *walk_state)
 578 {
 579         struct acpi_namespace_node *method_node;
 580         acpi_status status;
 581
 582         ACPI_FUNCTION_TRACE_PTR(ds_terminate_control_method, walk_state);
 583
 584         /* method_desc is required, walk_state is optional */
 585
 586         if (!method_desc) {
 587                 return_VOID;
 588         }
 589
 590         if (walk_state) {
 591
 592                 /* Delete all arguments and locals */
 593
 594                 acpi_ds_method_data_delete_all(walk_state);
 595         }
 596
 597         /*
 598          * If method is serialized, release the mutex and restore the
 599          * current sync level for this thread
 600          */
 601         if (method_desc->method.mutex) {
 602
 603                 /* Acquisition Depth handles recursive calls */
 604
 605                 method_desc->method.mutex->mutex.acquisition_depth--;
 606                 if (!method_desc->method.mutex->mutex.acquisition_depth) {
 607                         walk_state->thread->current_sync_level =
 608                             method_desc->method.mutex->mutex.
 609                             original_sync_level;
 610
 611                         acpi_os_release_mutex(method_desc->method.mutex->mutex.
 612                                               os_mutex);
 613                         method_desc->method.mutex->mutex.owner_thread = NULL;
 614                 }
 615         }
 616
 617         if (walk_state) {
 618                 /*
 619                  * Delete any objects created by this method during execution.
 620                  * The method Node is stored in the walk state
 621                  */
 622                 method_node = walk_state->method_node;
 623
 624                 /*
 625                  * Delete any namespace objects created anywhere within
 626                  * the namespace by the execution of this method
 627                  */
 628                 acpi_ns_delete_namespace_by_owner(method_desc->method.owner_id);
 629         }
 630
 631         /* Decrement the thread count on the method */
 632
 633         if (method_desc->method.thread_count) {
 634                 method_desc->method.thread_count--;
 635         } else {
 636                 ACPI_ERROR((AE_INFO, "Invalid zero thread count in method"));
 637         }
 638
 639         /* Are there any other threads currently executing this method? */
 640
 641         if (method_desc->method.thread_count) {
 642                 /*
 643                  * Additional threads. Do not release the owner_id in this case,
 644                  * we immediately reuse it for the next thread executing this method
 645                  */
 646                 ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 647                                   "*** Completed execution of one thread, %d threads remaining\n",
 648                                   method_desc->method.thread_count));
 649         } else {
 650                 /* This is the only executing thread for this method */
 651
 652                 /*
 653                  * Support to dynamically change a method from not_serialized to
 654                  * Serialized if it appears that the method is incorrectly written and
 655                  * does not support multiple thread execution. The best example of this
 656                  * is if such a method creates namespace objects and blocks. A second
 657                  * thread will fail with an AE_ALREADY_EXISTS exception
 658                  *
 659                  * This code is here because we must wait until the last thread exits
 660                  * before creating the synchronization semaphore.
 661                  */
 662                 if ((method_desc->method.method_flags & AML_METHOD_SERIALIZED)
 663                     && (!method_desc->method.mutex)) {
 664                         status = acpi_ds_create_method_mutex(method_desc);
 665                 }
 666
 667                 /* No more threads, we can free the owner_id */
 668
 669                 acpi_ut_release_owner_id(&method_desc->method.owner_id);
 670         }
 671
 672         return_VOID;
 673 }