model.cc

   1 #include <stdio.h>
   2 #include <algorithm>
   3
   4 #include "model.h"
   5 #include "action.h"
   6 #include "nodestack.h"
   7 #include "schedule.h"
   8 #include "snapshot-interface.h"
   9 #include "common.h"
  10 #include "clockvector.h"
  11 #include "cyclegraph.h"
  12 #include "promise.h"
  13 #include "datarace.h"
  14
  15 #define INITIAL_THREAD_ID       0
  16
  17 ModelChecker *model;
  18
  19 /** @brief Constructor */
  20 ModelChecker::ModelChecker(struct model_params params) :
  21         /* Initialize default scheduler */
  22         scheduler(new Scheduler()),
  23         num_executions(0),
  24         num_feasible_executions(0),
  25         params(params),
  26         diverge(NULL),
  27         action_trace(new action_list_t()),
  28         thread_map(new HashTable<int, Thread *, int>()),
  29         obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
  30         obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
  31         promises(new std::vector<Promise *>()),
  32         futurevalues(new std::vector<struct PendingFutureValue>()),
  33         lazy_sync_with_release(new HashTable<void *, action_list_t, uintptr_t, 4>()),
  34         thrd_last_action(new std::vector<ModelAction *>(1)),
  35         node_stack(new NodeStack()),
  36         mo_graph(new CycleGraph()),
  37         failed_promise(false),
  38         too_many_reads(false),
  39         asserted(false)
  40 {
  41         /* Allocate this "size" on the snapshotting heap */
  42         priv = (struct model_snapshot_members *)calloc(1, sizeof(*priv));
  43         /* First thread created will have id INITIAL_THREAD_ID */
  44         priv->next_thread_id = INITIAL_THREAD_ID;
  45
  46         lazy_sync_size = &priv->lazy_sync_size;
  47 }
  48
  49 /** @brief Destructor */
  50 ModelChecker::~ModelChecker()
  51 {
  52         for (int i = 0; i < get_num_threads(); i++)
  53                 delete thread_map->get(i);
  54         delete thread_map;
  55
  56         delete obj_thrd_map;
  57         delete obj_map;
  58         delete action_trace;
  59
  60         for (unsigned int i = 0; i < promises->size(); i++)
  61                 delete (*promises)[i];
  62         delete promises;
  63
  64         delete lazy_sync_with_release;
  65
  66         delete thrd_last_action;
  67         delete node_stack;
  68         delete scheduler;
  69         delete mo_graph;
  70 }
  71
  72 /**
  73  * Restores user program to initial state and resets all model-checker data
  74  * structures.
  75  */
  76 void ModelChecker::reset_to_initial_state()
  77 {
  78         DEBUG("+++ Resetting to initial state +++\n");
  79         node_stack->reset_execution();
  80         failed_promise = false;
  81         too_many_reads = false;
  82         reset_asserted();
  83         snapshotObject->backTrackBeforeStep(0);
  84 }
  85
  86 /** @returns a thread ID for a new Thread */
  87 thread_id_t ModelChecker::get_next_id()
  88 {
  89         return priv->next_thread_id++;
  90 }
  91
  92 /** @returns the number of user threads created during this execution */
  93 int ModelChecker::get_num_threads()
  94 {
  95         return priv->next_thread_id;
  96 }
  97
  98 /** @returns a sequence number for a new ModelAction */
  99 modelclock_t ModelChecker::get_next_seq_num()
 100 {
 101         return ++priv->used_sequence_numbers;
 102 }
 103
 104 /**
 105  * @brief Choose the next thread to execute.
 106  *
 107  * This function chooses the next thread that should execute. It can force the
 108  * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
 109  * followed by a THREAD_START, or it can enforce execution replay/backtracking.
 110  * The model-checker may have no preference regarding the next thread (i.e.,
 111  * when exploring a new execution ordering), in which case this will return
 112  * NULL.
 113  * @param curr The current ModelAction. This action might guide the choice of
 114  * next thread.
 115  * @return The next thread to run. If the model-checker has no preference, NULL.
 116  */
 117 Thread * ModelChecker::get_next_thread(ModelAction *curr)
 118 {
 119         thread_id_t tid;
 120
 121         /* Do not split atomic actions. */
 122         if (curr->is_rmwr())
 123                 return thread_current();
 124         /* The THREAD_CREATE action points to the created Thread */
 125         else if (curr->get_type() == THREAD_CREATE)
 126                 return (Thread *)curr->get_location();
 127
 128         /* Have we completed exploring the preselected path? */
 129         if (diverge == NULL)
 130                 return NULL;
 131
 132         /* Else, we are trying to replay an execution */
 133         ModelAction *next = node_stack->get_next()->get_action();
 134
 135         if (next == diverge) {
 136                 Node *nextnode = next->get_node();
 137                 /* Reached divergence point */
 138                 if (nextnode->increment_promise()) {
 139                         /* The next node will try to satisfy a different set of promises. */
 140                         tid = next->get_tid();
 141                         node_stack->pop_restofstack(2);
 142                 } else if (nextnode->increment_read_from()) {
 143                         /* The next node will read from a different value. */
 144                         tid = next->get_tid();
 145                         node_stack->pop_restofstack(2);
 146                 } else if (nextnode->increment_future_value()) {
 147                         /* The next node will try to read from a different future value. */
 148                         tid = next->get_tid();
 149                         node_stack->pop_restofstack(2);
 150                 } else {
 151                         /* Make a different thread execute for next step */
 152                         Node *node = nextnode->get_parent();
 153                         tid = node->get_next_backtrack();
 154                         node_stack->pop_restofstack(1);
 155                 }
 156                 DEBUG("*** Divergence point ***\n");
 157                 diverge = NULL;
 158         } else {
 159                 tid = next->get_tid();
 160         }
 161         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 162         ASSERT(tid != THREAD_ID_T_NONE);
 163         return thread_map->get(id_to_int(tid));
 164 }
 165
 166 /**
 167  * Queries the model-checker for more executions to explore and, if one
 168  * exists, resets the model-checker state to execute a new execution.
 169  *
 170  * @return If there are more executions to explore, return true. Otherwise,
 171  * return false.
 172  */
 173 bool ModelChecker::next_execution()
 174 {
 175         DBG();
 176
 177         num_executions++;
 178         if (isfinalfeasible())
 179                 num_feasible_executions++;
 180
 181         if (isfinalfeasible() || DBG_ENABLED())
 182                 print_summary();
 183
 184         if ((diverge = get_next_backtrack()) == NULL)
 185                 return false;
 186
 187         if (DBG_ENABLED()) {
 188                 printf("Next execution will diverge at:\n");
 189                 diverge->print();
 190         }
 191
 192         reset_to_initial_state();
 193         return true;
 194 }
 195
 196 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 197 {
 198         action_type type = act->get_type();
 199
 200         switch (type) {
 201                 case ATOMIC_READ:
 202                 case ATOMIC_WRITE:
 203                 case ATOMIC_RMW:
 204                         break;
 205                 default:
 206                         return NULL;
 207         }
 208         /* linear search: from most recent to oldest */
 209         action_list_t *list = obj_map->get_safe_ptr(act->get_location());
 210         action_list_t::reverse_iterator rit;
 211         for (rit = list->rbegin(); rit != list->rend(); rit++) {
 212                 ModelAction *prev = *rit;
 213                 if (act->is_synchronizing(prev))
 214                         return prev;
 215         }
 216         return NULL;
 217 }
 218
 219 void ModelChecker::set_backtracking(ModelAction *act)
 220 {
 221         ModelAction *prev;
 222         Node *node;
 223         Thread *t = get_thread(act);
 224
 225         prev = get_last_conflict(act);
 226         if (prev == NULL)
 227                 return;
 228
 229         node = prev->get_node()->get_parent();
 230
 231         while (!node->is_enabled(t))
 232                 t = t->get_parent();
 233
 234         /* Check if this has been explored already */
 235         if (node->has_been_explored(t->get_id()))
 236                 return;
 237
 238         /* Cache the latest backtracking point */
 239         if (!priv->next_backtrack || *prev > *priv->next_backtrack)
 240                 priv->next_backtrack = prev;
 241
 242         /* If this is a new backtracking point, mark the tree */
 243         if (!node->set_backtrack(t->get_id()))
 244                 return;
 245         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 246                         prev->get_tid(), t->get_id());
 247         if (DBG_ENABLED()) {
 248                 prev->print();
 249                 act->print();
 250         }
 251 }
 252
 253 /**
 254  * Returns last backtracking point. The model checker will explore a different
 255  * path for this point in the next execution.
 256  * @return The ModelAction at which the next execution should diverge.
 257  */
 258 ModelAction * ModelChecker::get_next_backtrack()
 259 {
 260         ModelAction *next = priv->next_backtrack;
 261         priv->next_backtrack = NULL;
 262         return next;
 263 }
 264
 265 /**
 266  * Processes a read or rmw model action.
 267  * @param curr is the read model action to process.
 268  * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
 269  * @return True if processing this read updates the mo_graph.
 270  */
 271 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
 272 {
 273         uint64_t value;
 274         bool updated = false;
 275         while (true) {
 276                 const ModelAction *reads_from = curr->get_node()->get_read_from();
 277                 if (reads_from != NULL) {
 278                         mo_graph->startChanges();
 279
 280                         value = reads_from->get_value();
 281                         bool r_status = false;
 282
 283                         if (!second_part_of_rmw) {
 284                                 check_recency(curr);
 285                                 r_status = r_modification_order(curr, reads_from);
 286                         }
 287
 288
 289                         if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
 290                                 mo_graph->rollbackChanges();
 291                                 too_many_reads = false;
 292                                 continue;
 293                         }
 294
 295                         curr->read_from(reads_from);
 296                         mo_graph->commitChanges();
 297                         updated |= r_status;
 298                 } else if (!second_part_of_rmw) {
 299                         /* Read from future value */
 300                         value = curr->get_node()->get_future_value();
 301                         modelclock_t expiration = curr->get_node()->get_future_value_expiration();
 302                         curr->read_from(NULL);
 303                         Promise *valuepromise = new Promise(curr, value, expiration);
 304                         promises->push_back(valuepromise);
 305                 }
 306                 get_thread(curr)->set_return_value(value);
 307                 return updated;
 308         }
 309 }
 310
 311 /**
 312  * Process a write ModelAction
 313  * @param curr The ModelAction to process
 314  * @return True if the mo_graph was updated or promises were resolved
 315  */
 316 bool ModelChecker::process_write(ModelAction *curr)
 317 {
 318         bool updated_mod_order = w_modification_order(curr);
 319         bool updated_promises = resolve_promises(curr);
 320
 321         if (promises->size() == 0) {
 322                 for (unsigned int i = 0; i<futurevalues->size(); i++) {
 323                         struct PendingFutureValue pfv = (*futurevalues)[i];
 324                         if (pfv.act->get_node()->add_future_value(pfv.value, pfv.expiration) &&
 325                                         (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
 326                                 priv->next_backtrack = pfv.act;
 327                 }
 328                 futurevalues->resize(0);
 329         }
 330
 331         mo_graph->commitChanges();
 332         get_thread(curr)->set_return_value(VALUE_NONE);
 333         return updated_mod_order || updated_promises;
 334 }
 335
 336 /**
 337  * Initialize the current action by performing one or more of the following
 338  * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
 339  * in the NodeStack, manipulating backtracking sets, allocating and
 340  * initializing clock vectors, and computing the promises to fulfill.
 341  *
 342  * @param curr The current action, as passed from the user context; may be
 343  * freed/invalidated after the execution of this function
 344  * @return The current action, as processed by the ModelChecker. Is only the
 345  * same as the parameter @a curr if this is a newly-explored action.
 346  */
 347 ModelAction * ModelChecker::initialize_curr_action(ModelAction *curr)
 348 {
 349         ModelAction *newcurr;
 350
 351         if (curr->is_rmwc() || curr->is_rmw()) {
 352                 newcurr = process_rmw(curr);
 353                 delete curr;
 354                 compute_promises(newcurr);
 355                 return newcurr;
 356         }
 357
 358         newcurr = node_stack->explore_action(curr);
 359         if (newcurr) {
 360                 /* First restore type and order in case of RMW operation */
 361                 if (curr->is_rmwr())
 362                         newcurr->copy_typeandorder(curr);
 363
 364                 /* Discard duplicate ModelAction; use action from NodeStack */
 365                 delete curr;
 366
 367                 /* If we have diverged, we need to reset the clock vector. */
 368                 if (diverge == NULL)
 369                         newcurr->create_cv(get_parent_action(newcurr->get_tid()));
 370         } else {
 371                 newcurr = curr;
 372                 /*
 373                  * Perform one-time actions when pushing new ModelAction onto
 374                  * NodeStack
 375                  */
 376                 curr->create_cv(get_parent_action(curr->get_tid()));
 377                 if (curr->is_write())
 378                         compute_promises(curr);
 379         }
 380         return newcurr;
 381 }
 382
 383 /**
 384  * This is the heart of the model checker routine. It performs model-checking
 385  * actions corresponding to a given "current action." Among other processes, it
 386  * calculates reads-from relationships, updates synchronization clock vectors,
 387  * forms a memory_order constraints graph, and handles replay/backtrack
 388  * execution when running permutations of previously-observed executions.
 389  *
 390  * @param curr The current action to process
 391  * @return The next Thread that must be executed. May be NULL if ModelChecker
 392  * makes no choice (e.g., according to replay execution, combining RMW actions,
 393  * etc.)
 394  */
 395 Thread * ModelChecker::check_current_action(ModelAction *curr)
 396 {
 397         ASSERT(curr);
 398
 399         bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
 400
 401         ModelAction *newcurr = initialize_curr_action(curr);
 402
 403         /* Add the action to lists before any other model-checking tasks */
 404         if (!second_part_of_rmw)
 405                 add_action_to_lists(newcurr);
 406
 407         /* Build may_read_from set for newly-created actions */
 408         if (curr == newcurr && curr->is_read())
 409                 build_reads_from_past(curr);
 410         curr = newcurr;
 411
 412         /* Thread specific actions */
 413         switch (curr->get_type()) {
 414         case THREAD_CREATE: {
 415                 Thread *th = (Thread *)curr->get_location();
 416                 th->set_creation(curr);
 417                 break;
 418         }
 419         case THREAD_JOIN: {
 420                 Thread *waiting, *blocking;
 421                 waiting = get_thread(curr);
 422                 blocking = (Thread *)curr->get_location();
 423                 if (!blocking->is_complete()) {
 424                         blocking->push_wait_list(curr);
 425                         scheduler->sleep(waiting);
 426                 } else {
 427                         do_complete_join(curr);
 428                 }
 429                 break;
 430         }
 431         case THREAD_FINISH: {
 432                 Thread *th = get_thread(curr);
 433                 while (!th->wait_list_empty()) {
 434                         ModelAction *act = th->pop_wait_list();
 435                         Thread *wake = get_thread(act);
 436                         scheduler->wake(wake);
 437                         do_complete_join(act);
 438                 }
 439                 th->complete();
 440                 break;
 441         }
 442         case THREAD_START: {
 443                 check_promises(NULL, curr->get_cv());
 444                 break;
 445         }
 446         default:
 447                 break;
 448         }
 449
 450         work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
 451
 452         while (!work_queue.empty()) {
 453                 WorkQueueEntry work = work_queue.front();
 454                 work_queue.pop_front();
 455
 456                 switch (work.type) {
 457                 case WORK_CHECK_CURR_ACTION: {
 458                         ModelAction *act = work.action;
 459                         bool updated = false;
 460                         if (act->is_read() && process_read(act, second_part_of_rmw))
 461                                 updated = true;
 462
 463                         if (act->is_write() && process_write(act))
 464                                 updated = true;
 465
 466                         if (updated)
 467                                 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
 468                         break;
 469                 }
 470                 case WORK_CHECK_RELEASE_SEQ:
 471                         resolve_release_sequences(work.location, &work_queue);
 472                         break;
 473                 case WORK_CHECK_MO_EDGES: {
 474                         /** @todo Complete verification of work_queue */
 475                         ModelAction *act = work.action;
 476                         bool updated = false;
 477
 478                         if (act->is_read()) {
 479                                 if (r_modification_order(act, act->get_reads_from()))
 480                                         updated = true;
 481                         }
 482                         if (act->is_write()) {
 483                                 if (w_modification_order(act))
 484                                         updated = true;
 485                         }
 486
 487                         if (updated)
 488                                 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
 489                         break;
 490                 }
 491                 default:
 492                         ASSERT(false);
 493                         break;
 494                 }
 495         }
 496
 497         check_curr_backtracking(curr);
 498
 499         set_backtracking(curr);
 500
 501         return get_next_thread(curr);
 502 }
 503
 504 /**
 505  * Complete a THREAD_JOIN operation, by synchronizing with the THREAD_FINISH
 506  * operation from the Thread it is joining with. Must be called after the
 507  * completion of the Thread in question.
 508  * @param join The THREAD_JOIN action
 509  */
 510 void ModelChecker::do_complete_join(ModelAction *join)
 511 {
 512         Thread *blocking = (Thread *)join->get_location();
 513         ModelAction *act = get_last_action(blocking->get_id());
 514         join->synchronize_with(act);
 515 }
 516
 517 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
 518         Node *currnode = curr->get_node();
 519         Node *parnode = currnode->get_parent();
 520
 521         if ((!parnode->backtrack_empty() ||
 522                          !currnode->read_from_empty() ||
 523                          !currnode->future_value_empty() ||
 524                          !currnode->promise_empty())
 525                         && (!priv->next_backtrack ||
 526                                         *curr > *priv->next_backtrack)) {
 527                 priv->next_backtrack = curr;
 528         }
 529 }
 530
 531 bool ModelChecker::promises_expired() {
 532         for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
 533                 Promise *promise = (*promises)[promise_index];
 534                 if (promise->get_expiration()<priv->used_sequence_numbers) {
 535                         return true;
 536                 }
 537         }
 538         return false;
 539 }
 540
 541 /** @returns whether the current partial trace must be a prefix of a
 542  * feasible trace. */
 543 bool ModelChecker::isfeasibleprefix() {
 544         return promises->size() == 0 && *lazy_sync_size == 0;
 545 }
 546
 547 /** @returns whether the current partial trace is feasible. */
 548 bool ModelChecker::isfeasible() {
 549         return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW();
 550 }
 551
 552 /** @returns whether the current partial trace is feasible other than
 553  * multiple RMW reading from the same store. */
 554 bool ModelChecker::isfeasibleotherthanRMW() {
 555         if (DBG_ENABLED()) {
 556                 if (mo_graph->checkForCycles())
 557                         DEBUG("Infeasible: modification order cycles\n");
 558                 if (failed_promise)
 559                         DEBUG("Infeasible: failed promise\n");
 560                 if (too_many_reads)
 561                         DEBUG("Infeasible: too many reads\n");
 562                 if (promises_expired())
 563                         DEBUG("Infeasible: promises expired\n");
 564         }
 565         return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !promises_expired();
 566 }
 567
 568 /** Returns whether the current completed trace is feasible. */
 569 bool ModelChecker::isfinalfeasible() {
 570         if (DBG_ENABLED() && promises->size() != 0)
 571                 DEBUG("Infeasible: unrevolved promises\n");
 572
 573         return isfeasible() && promises->size() == 0;
 574 }
 575
 576 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
 577 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
 578         int tid = id_to_int(act->get_tid());
 579         ModelAction *lastread = get_last_action(tid);
 580         lastread->process_rmw(act);
 581         if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
 582                 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
 583                 mo_graph->commitChanges();
 584         }
 585         return lastread;
 586 }
 587
 588 /**
 589  * Checks whether a thread has read from the same write for too many times
 590  * without seeing the effects of a later write.
 591  *
 592  * Basic idea:
 593  * 1) there must a different write that we could read from that would satisfy the modification order,
 594  * 2) we must have read from the same value in excess of maxreads times, and
 595  * 3) that other write must have been in the reads_from set for maxreads times.
 596  *
 597  * If so, we decide that the execution is no longer feasible.
 598  */
 599 void ModelChecker::check_recency(ModelAction *curr) {
 600         if (params.maxreads != 0) {
 601                 if (curr->get_node()->get_read_from_size() <= 1)
 602                         return;
 603
 604                 //Must make sure that execution is currently feasible...  We could
 605                 //accidentally clear by rolling back
 606                 if (!isfeasible())
 607                         return;
 608
 609                 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
 610                 int tid = id_to_int(curr->get_tid());
 611
 612                 /* Skip checks */
 613                 if ((int)thrd_lists->size() <= tid)
 614                         return;
 615
 616                 action_list_t *list = &(*thrd_lists)[tid];
 617
 618                 action_list_t::reverse_iterator rit = list->rbegin();
 619                 /* Skip past curr */
 620                 for (; (*rit) != curr; rit++)
 621                         ;
 622                 /* go past curr now */
 623                 rit++;
 624
 625                 action_list_t::reverse_iterator ritcopy = rit;
 626                 //See if we have enough reads from the same value
 627                 int count = 0;
 628                 for (; count < params.maxreads; rit++,count++) {
 629                         if (rit==list->rend())
 630                                 return;
 631                         ModelAction *act = *rit;
 632                         if (!act->is_read())
 633                                 return;
 634                         if (act->get_reads_from() != curr->get_reads_from())
 635                                 return;
 636                         if (act->get_node()->get_read_from_size() <= 1)
 637                                 return;
 638                 }
 639
 640                 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
 641                         //Get write
 642                         const ModelAction * write = curr->get_node()->get_read_from_at(i);
 643                         //Need a different write
 644                         if (write==curr->get_reads_from())
 645                                 continue;
 646
 647                         /* Test to see whether this is a feasible write to read from*/
 648                         mo_graph->startChanges();
 649                         r_modification_order(curr, write);
 650                         bool feasiblereadfrom = isfeasible();
 651                         mo_graph->rollbackChanges();
 652
 653                         if (!feasiblereadfrom)
 654                                 continue;
 655                         rit = ritcopy;
 656
 657                         bool feasiblewrite = true;
 658                         //new we need to see if this write works for everyone
 659
 660                         for (int loop = count; loop>0; loop--,rit++) {
 661                                 ModelAction *act=*rit;
 662                                 bool foundvalue = false;
 663                                 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
 664                                         if (act->get_node()->get_read_from_at(i)==write) {
 665                                                 foundvalue = true;
 666                                                 break;
 667                                         }
 668                                 }
 669                                 if (!foundvalue) {
 670                                         feasiblewrite = false;
 671                                         break;
 672                                 }
 673                         }
 674                         if (feasiblewrite) {
 675                                 too_many_reads = true;
 676                                 return;
 677                         }
 678                 }
 679         }
 680 }
 681
 682 /**
 683  * Updates the mo_graph with the constraints imposed from the current
 684  * read.
 685  *
 686  * Basic idea is the following: Go through each other thread and find
 687  * the lastest action that happened before our read.  Two cases:
 688  *
 689  * (1) The action is a write => that write must either occur before
 690  * the write we read from or be the write we read from.
 691  *
 692  * (2) The action is a read => the write that that action read from
 693  * must occur before the write we read from or be the same write.
 694  *
 695  * @param curr The current action. Must be a read.
 696  * @param rf The action that curr reads from. Must be a write.
 697  * @return True if modification order edges were added; false otherwise
 698  */
 699 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
 700 {
 701         std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
 702         unsigned int i;
 703         bool added = false;
 704         ASSERT(curr->is_read());
 705
 706         /* Iterate over all threads */
 707         for (i = 0; i < thrd_lists->size(); i++) {
 708                 /* Iterate over actions in thread, starting from most recent */
 709                 action_list_t *list = &(*thrd_lists)[i];
 710                 action_list_t::reverse_iterator rit;
 711                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 712                         ModelAction *act = *rit;
 713
 714                         /*
 715                          * Include at most one act per-thread that "happens
 716                          * before" curr. Don't consider reflexively.
 717                          */
 718                         if (act->happens_before(curr) && act != curr) {
 719                                 if (act->is_write()) {
 720                                         if (rf != act) {
 721                                                 mo_graph->addEdge(act, rf);
 722                                                 added = true;
 723                                         }
 724                                 } else {
 725                                         const ModelAction *prevreadfrom = act->get_reads_from();
 726                                         if (prevreadfrom != NULL && rf != prevreadfrom) {
 727                                                 mo_graph->addEdge(prevreadfrom, rf);
 728                                                 added = true;
 729                                         }
 730                                 }
 731                                 break;
 732                         }
 733                 }
 734         }
 735
 736         return added;
 737 }
 738
 739 /** This method fixes up the modification order when we resolve a
 740  *  promises.  The basic problem is that actions that occur after the
 741  *  read curr could not property add items to the modification order
 742  *  for our read.
 743  *
 744  *  So for each thread, we find the earliest item that happens after
 745  *  the read curr.  This is the item we have to fix up with additional
 746  *  constraints.  If that action is write, we add a MO edge between
 747  *  the Action rf and that action.  If the action is a read, we add a
 748  *  MO edge between the Action rf, and whatever the read accessed.
 749  *
 750  * @param curr is the read ModelAction that we are fixing up MO edges for.
 751  * @param rf is the write ModelAction that curr reads from.
 752  *
 753  */
 754
 755 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
 756 {
 757         std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
 758         unsigned int i;
 759         ASSERT(curr->is_read());
 760
 761         /* Iterate over all threads */
 762         for (i = 0; i < thrd_lists->size(); i++) {
 763                 /* Iterate over actions in thread, starting from most recent */
 764                 action_list_t *list = &(*thrd_lists)[i];
 765                 action_list_t::reverse_iterator rit;
 766                 ModelAction *lastact = NULL;
 767
 768                 /* Find last action that happens after curr */
 769                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 770                         ModelAction *act = *rit;
 771                         if (curr->happens_before(act)) {
 772                                 lastact = act;
 773                         } else
 774                                 break;
 775                 }
 776
 777                         /* Include at most one act per-thread that "happens before" curr */
 778                 if (lastact != NULL) {
 779                         if (lastact->is_read()) {
 780                                 const ModelAction *postreadfrom = lastact->get_reads_from();
 781                                 if (postreadfrom != NULL&&rf != postreadfrom)
 782                                         mo_graph->addEdge(rf, postreadfrom);
 783                         } else if (rf != lastact) {
 784                                 mo_graph->addEdge(rf, lastact);
 785                         }
 786                         break;
 787                 }
 788         }
 789 }
 790
 791 /**
 792  * Updates the mo_graph with the constraints imposed from the current write.
 793  *
 794  * Basic idea is the following: Go through each other thread and find
 795  * the lastest action that happened before our write.  Two cases:
 796  *
 797  * (1) The action is a write => that write must occur before
 798  * the current write
 799  *
 800  * (2) The action is a read => the write that that action read from
 801  * must occur before the current write.
 802  *
 803  * This method also handles two other issues:
 804  *
 805  * (I) Sequential Consistency: Making sure that if the current write is
 806  * seq_cst, that it occurs after the previous seq_cst write.
 807  *
 808  * (II) Sending the write back to non-synchronizing reads.
 809  *
 810  * @param curr The current action. Must be a write.
 811  * @return True if modification order edges were added; false otherwise
 812  */
 813 bool ModelChecker::w_modification_order(ModelAction *curr)
 814 {
 815         std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
 816         unsigned int i;
 817         bool added = false;
 818         ASSERT(curr->is_write());
 819
 820         if (curr->is_seqcst()) {
 821                 /* We have to at least see the last sequentially consistent write,
 822                          so we are initialized. */
 823                 ModelAction *last_seq_cst = get_last_seq_cst(curr);
 824                 if (last_seq_cst != NULL) {
 825                         mo_graph->addEdge(last_seq_cst, curr);
 826                         added = true;
 827                 }
 828         }
 829
 830         /* Iterate over all threads */
 831         for (i = 0; i < thrd_lists->size(); i++) {
 832                 /* Iterate over actions in thread, starting from most recent */
 833                 action_list_t *list = &(*thrd_lists)[i];
 834                 action_list_t::reverse_iterator rit;
 835                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 836                         ModelAction *act = *rit;
 837                         if (act == curr) {
 838                                 /*
 839                                  * If RMW, we already have all relevant edges,
 840                                  * so just skip to next thread.
 841                                  * If normal write, we need to look at earlier
 842                                  * actions, so continue processing list.
 843                                  */
 844                                 if (curr->is_rmw())
 845                                         break;
 846                                 else
 847                                         continue;
 848                         }
 849
 850                         /*
 851                          * Include at most one act per-thread that "happens
 852                          * before" curr
 853                          */
 854                         if (act->happens_before(curr)) {
 855                                 /*
 856                                  * Note: if act is RMW, just add edge:
 857                                  *   act --mo--> curr
 858                                  * The following edge should be handled elsewhere:
 859                                  *   readfrom(act) --mo--> act
 860                                  */
 861                                 if (act->is_write())
 862                                         mo_graph->addEdge(act, curr);
 863                                 else if (act->is_read() && act->get_reads_from() != NULL)
 864                                         mo_graph->addEdge(act->get_reads_from(), curr);
 865                                 added = true;
 866                                 break;
 867                         } else if (act->is_read() && !act->is_synchronizing(curr) &&
 868                                                      !act->same_thread(curr)) {
 869                                 /* We have an action that:
 870                                    (1) did not happen before us
 871                                    (2) is a read and we are a write
 872                                    (3) cannot synchronize with us
 873                                    (4) is in a different thread
 874                                    =>
 875                                    that read could potentially read from our write.
 876                                  */
 877                                 if (thin_air_constraint_may_allow(curr, act)) {
 878                                         if (isfeasible() ||
 879                                                         (curr->is_rmw() && act->is_rmw() && curr->get_reads_from()==act->get_reads_from() && isfeasibleotherthanRMW())) {
 880                                                 struct PendingFutureValue pfv = {curr->get_value(),curr->get_seq_number()+params.maxfuturedelay,act};
 881                                                 futurevalues->push_back(pfv);
 882                                         }
 883                                 }
 884                         }
 885                 }
 886         }
 887
 888         return added;
 889 }
 890
 891 /** Arbitrary reads from the future are not allowed.  Section 29.3
 892  * part 9 places some constraints.  This method checks one result of constraint
 893  * constraint.  Others require compiler support. */
 894
 895 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
 896         if (!writer->is_rmw())
 897                 return true;
 898
 899         if (!reader->is_rmw())
 900                 return true;
 901
 902         for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
 903                 if (search==reader)
 904                         return false;
 905                 if (search->get_tid() == reader->get_tid() &&
 906                                 search->happens_before(reader))
 907                         break;
 908         }
 909
 910         return true;
 911 }
 912
 913 /**
 914  * Finds the head(s) of the release sequence(s) containing a given ModelAction.
 915  * The ModelAction under consideration is expected to be taking part in
 916  * release/acquire synchronization as an object of the "reads from" relation.
 917  * Note that this can only provide release sequence support for RMW chains
 918  * which do not read from the future, as those actions cannot be traced until
 919  * their "promise" is fulfilled. Similarly, we may not even establish the
 920  * presence of a release sequence with certainty, as some modification order
 921  * constraints may be decided further in the future. Thus, this function
 922  * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
 923  * and a boolean representing certainty.
 924  *
 925  * @todo Finish lazy updating, when promises are fulfilled in the future
 926  * @param rf The action that might be part of a release sequence. Must be a
 927  * write.
 928  * @param release_heads A pass-by-reference style return parameter.  After
 929  * execution of this function, release_heads will contain the heads of all the
 930  * relevant release sequences, if any exists
 931  * @return true, if the ModelChecker is certain that release_heads is complete;
 932  * false otherwise
 933  */
 934 bool ModelChecker::release_seq_head(const ModelAction *rf, rel_heads_list_t *release_heads) const
 935 {
 936         if (!rf) {
 937                 /* read from future: need to settle this later */
 938                 return false; /* incomplete */
 939         }
 940
 941         ASSERT(rf->is_write());
 942
 943         if (rf->is_release())
 944                 release_heads->push_back(rf);
 945         if (rf->is_rmw()) {
 946                 /* We need a RMW action that is both an acquire and release to stop */
 947                 /** @todo Need to be smarter here...  In the linux lock
 948                  * example, this will run to the beginning of the program for
 949                  * every acquire. */
 950                 if (rf->is_acquire() && rf->is_release())
 951                         return true; /* complete */
 952                 return release_seq_head(rf->get_reads_from(), release_heads);
 953         }
 954         if (rf->is_release())
 955                 return true; /* complete */
 956
 957         /* else relaxed write; check modification order for contiguous subsequence
 958          * -> rf must be same thread as release */
 959         int tid = id_to_int(rf->get_tid());
 960         std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
 961         action_list_t *list = &(*thrd_lists)[tid];
 962         action_list_t::const_reverse_iterator rit;
 963
 964         /* Find rf in the thread list */
 965         rit = std::find(list->rbegin(), list->rend(), rf);
 966         ASSERT(rit != list->rend());
 967
 968         /* Find the last write/release */
 969         for (; rit != list->rend(); rit++)
 970                 if ((*rit)->is_release())
 971                         break;
 972         if (rit == list->rend()) {
 973                 /* No write-release in this thread */
 974                 return true; /* complete */
 975         }
 976         ModelAction *release = *rit;
 977
 978         ASSERT(rf->same_thread(release));
 979
 980         bool certain = true;
 981         for (unsigned int i = 0; i < thrd_lists->size(); i++) {
 982                 if (id_to_int(rf->get_tid()) == (int)i)
 983                         continue;
 984                 list = &(*thrd_lists)[i];
 985
 986                 /* Can we ensure no future writes from this thread may break
 987                  * the release seq? */
 988                 bool future_ordered = false;
 989
 990                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 991                         const ModelAction *act = *rit;
 992                         if (!act->is_write())
 993                                 continue;
 994                         /* Reach synchronization -> this thread is complete */
 995                         if (act->happens_before(release))
 996                                 break;
 997                         if (rf->happens_before(act)) {
 998                                 future_ordered = true;
 999                                 continue;
1000                         }
1001
1002                         /* Check modification order */
1003                         if (mo_graph->checkReachable(rf, act)) {
1004                                 /* rf --mo--> act */
1005                                 future_ordered = true;
1006                                 continue;
1007                         }
1008                         if (mo_graph->checkReachable(act, release))
1009                                 /* act --mo--> release */
1010                                 break;
1011                         if (mo_graph->checkReachable(release, act) &&
1012                                       mo_graph->checkReachable(act, rf)) {
1013                                 /* release --mo-> act --mo--> rf */
1014                                 return true; /* complete */
1015                         }
1016                         certain = false;
1017                 }
1018                 if (!future_ordered)
1019                         return false; /* This thread is uncertain */
1020         }
1021
1022         if (certain)
1023                 release_heads->push_back(release);
1024         return certain;
1025 }
1026
1027 /**
1028  * A public interface for getting the release sequence head(s) with which a
1029  * given ModelAction must synchronize. This function only returns a non-empty
1030  * result when it can locate a release sequence head with certainty. Otherwise,
1031  * it may mark the internal state of the ModelChecker so that it will handle
1032  * the release sequence at a later time, causing @a act to update its
1033  * synchronization at some later point in execution.
1034  * @param act The 'acquire' action that may read from a release sequence
1035  * @param release_heads A pass-by-reference return parameter. Will be filled
1036  * with the head(s) of the release sequence(s), if they exists with certainty.
1037  * @see ModelChecker::release_seq_head
1038  */
1039 void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
1040 {
1041         const ModelAction *rf = act->get_reads_from();
1042         bool complete;
1043         complete = release_seq_head(rf, release_heads);
1044         if (!complete) {
1045                 /* add act to 'lazy checking' list */
1046                 action_list_t *list;
1047                 list = lazy_sync_with_release->get_safe_ptr(act->get_location());
1048                 list->push_back(act);
1049                 (*lazy_sync_size)++;
1050         }
1051 }
1052
1053 /**
1054  * Attempt to resolve all stashed operations that might synchronize with a
1055  * release sequence for a given location. This implements the "lazy" portion of
1056  * determining whether or not a release sequence was contiguous, since not all
1057  * modification order information is present at the time an action occurs.
1058  *
1059  * @param location The location/object that should be checked for release
1060  * sequence resolutions
1061  * @param work_queue The work queue to which to add work items as they are
1062  * generated
1063  * @return True if any updates occurred (new synchronization, new mo_graph
1064  * edges)
1065  */
1066 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
1067 {
1068         action_list_t *list;
1069         list = lazy_sync_with_release->getptr(location);
1070         if (!list)
1071                 return false;
1072
1073         bool updated = false;
1074         action_list_t::iterator it = list->begin();
1075         while (it != list->end()) {
1076                 ModelAction *act = *it;
1077                 const ModelAction *rf = act->get_reads_from();
1078                 rel_heads_list_t release_heads;
1079                 bool complete;
1080                 complete = release_seq_head(rf, &release_heads);
1081                 for (unsigned int i = 0; i < release_heads.size(); i++) {
1082                         if (!act->has_synchronized_with(release_heads[i])) {
1083                                 updated = true;
1084                                 act->synchronize_with(release_heads[i]);
1085                         }
1086                 }
1087
1088                 if (updated) {
1089                         /* Re-check act for mo_graph edges */
1090                         work_queue->push_back(MOEdgeWorkEntry(act));
1091
1092                         /* propagate synchronization to later actions */
1093                         action_list_t::reverse_iterator it = action_trace->rbegin();
1094                         while ((*it) != act) {
1095                                 ModelAction *propagate = *it;
1096                                 if (act->happens_before(propagate)) {
1097                                         propagate->synchronize_with(act);
1098                                         /* Re-check 'propagate' for mo_graph edges */
1099                                         work_queue->push_back(MOEdgeWorkEntry(propagate));
1100                                 }
1101                         }
1102                 }
1103                 if (complete) {
1104                         it = list->erase(it);
1105                         (*lazy_sync_size)--;
1106                 } else
1107                         it++;
1108         }
1109
1110         // If we resolved promises or data races, see if we have realized a data race.
1111         if (checkDataRaces()) {
1112                 set_assert();
1113         }
1114
1115         return updated;
1116 }
1117
1118 /**
1119  * Performs various bookkeeping operations for the current ModelAction. For
1120  * instance, adds action to the per-object, per-thread action vector and to the
1121  * action trace list of all thread actions.
1122  *
1123  * @param act is the ModelAction to add.
1124  */
1125 void ModelChecker::add_action_to_lists(ModelAction *act)
1126 {
1127         int tid = id_to_int(act->get_tid());
1128         action_trace->push_back(act);
1129
1130         obj_map->get_safe_ptr(act->get_location())->push_back(act);
1131
1132         std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
1133         if (tid >= (int)vec->size())
1134                 vec->resize(priv->next_thread_id);
1135         (*vec)[tid].push_back(act);
1136
1137         if ((int)thrd_last_action->size() <= tid)
1138                 thrd_last_action->resize(get_num_threads());
1139         (*thrd_last_action)[tid] = act;
1140 }
1141
1142 ModelAction * ModelChecker::get_last_action(thread_id_t tid)
1143 {
1144         int nthreads = get_num_threads();
1145         if ((int)thrd_last_action->size() < nthreads)
1146                 thrd_last_action->resize(nthreads);
1147         return (*thrd_last_action)[id_to_int(tid)];
1148 }
1149
1150 /**
1151  * Gets the last memory_order_seq_cst write (in the total global sequence)
1152  * performed on a particular object (i.e., memory location), not including the
1153  * current action.
1154  * @param curr The current ModelAction; also denotes the object location to
1155  * check
1156  * @return The last seq_cst write
1157  */
1158 ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr)
1159 {
1160         void *location = curr->get_location();
1161         action_list_t *list = obj_map->get_safe_ptr(location);
1162         /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1163         action_list_t::reverse_iterator rit;
1164         for (rit = list->rbegin(); rit != list->rend(); rit++)
1165                 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
1166                         return *rit;
1167         return NULL;
1168 }
1169
1170 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
1171 {
1172         ModelAction *parent = get_last_action(tid);
1173         if (!parent)
1174                 parent = get_thread(tid)->get_creation();
1175         return parent;
1176 }
1177
1178 /**
1179  * Returns the clock vector for a given thread.
1180  * @param tid The thread whose clock vector we want
1181  * @return Desired clock vector
1182  */
1183 ClockVector * ModelChecker::get_cv(thread_id_t tid)
1184 {
1185         return get_parent_action(tid)->get_cv();
1186 }
1187
1188 /**
1189  * Resolve a set of Promises with a current write. The set is provided in the
1190  * Node corresponding to @a write.
1191  * @param write The ModelAction that is fulfilling Promises
1192  * @return True if promises were resolved; false otherwise
1193  */
1194 bool ModelChecker::resolve_promises(ModelAction *write)
1195 {
1196         bool resolved = false;
1197
1198         for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
1199                 Promise *promise = (*promises)[promise_index];
1200                 if (write->get_node()->get_promise(i)) {
1201                         ModelAction *read = promise->get_action();
1202                         read->read_from(write);
1203                         if (read->is_rmw()) {
1204                                 mo_graph->addRMWEdge(write, read);
1205                         }
1206                         //First fix up the modification order for actions that happened
1207                         //before the read
1208                         r_modification_order(read, write);
1209                         //Next fix up the modification order for actions that happened
1210                         //after the read.
1211                         post_r_modification_order(read, write);
1212                         promises->erase(promises->begin() + promise_index);
1213                         resolved = true;
1214                 } else
1215                         promise_index++;
1216         }
1217         return resolved;
1218 }
1219
1220 /**
1221  * Compute the set of promises that could potentially be satisfied by this
1222  * action. Note that the set computation actually appears in the Node, not in
1223  * ModelChecker.
1224  * @param curr The ModelAction that may satisfy promises
1225  */
1226 void ModelChecker::compute_promises(ModelAction *curr)
1227 {
1228         for (unsigned int i = 0; i < promises->size(); i++) {
1229                 Promise *promise = (*promises)[i];
1230                 const ModelAction *act = promise->get_action();
1231                 if (!act->happens_before(curr) &&
1232                                 act->is_read() &&
1233                                 !act->is_synchronizing(curr) &&
1234                                 !act->same_thread(curr) &&
1235                                 promise->get_value() == curr->get_value()) {
1236                         curr->get_node()->set_promise(i);
1237                 }
1238         }
1239 }
1240
1241 /** Checks promises in response to change in ClockVector Threads. */
1242 void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv)
1243 {
1244         for (unsigned int i = 0; i < promises->size(); i++) {
1245                 Promise *promise = (*promises)[i];
1246                 const ModelAction *act = promise->get_action();
1247                 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
1248                                 merge_cv->synchronized_since(act)) {
1249                         //This thread is no longer able to send values back to satisfy the promise
1250                         int num_synchronized_threads = promise->increment_threads();
1251                         if (num_synchronized_threads == get_num_threads()) {
1252                                 //Promise has failed
1253                                 failed_promise = true;
1254                                 return;
1255                         }
1256                 }
1257         }
1258 }
1259
1260 /**
1261  * Build up an initial set of all past writes that this 'read' action may read
1262  * from. This set is determined by the clock vector's "happens before"
1263  * relationship.
1264  * @param curr is the current ModelAction that we are exploring; it must be a
1265  * 'read' operation.
1266  */
1267 void ModelChecker::build_reads_from_past(ModelAction *curr)
1268 {
1269         std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1270         unsigned int i;
1271         ASSERT(curr->is_read());
1272
1273         ModelAction *last_seq_cst = NULL;
1274
1275         /* Track whether this object has been initialized */
1276         bool initialized = false;
1277
1278         if (curr->is_seqcst()) {
1279                 last_seq_cst = get_last_seq_cst(curr);
1280                 /* We have to at least see the last sequentially consistent write,
1281                          so we are initialized. */
1282                 if (last_seq_cst != NULL)
1283                         initialized = true;
1284         }
1285
1286         /* Iterate over all threads */
1287         for (i = 0; i < thrd_lists->size(); i++) {
1288                 /* Iterate over actions in thread, starting from most recent */
1289                 action_list_t *list = &(*thrd_lists)[i];
1290                 action_list_t::reverse_iterator rit;
1291                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1292                         ModelAction *act = *rit;
1293
1294                         /* Only consider 'write' actions */
1295                         if (!act->is_write() || act == curr)
1296                                 continue;
1297
1298                         /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1299                         if (!curr->is_seqcst()|| (!act->is_seqcst() && (last_seq_cst==NULL||!act->happens_before(last_seq_cst))) || act == last_seq_cst) {
1300                                 DEBUG("Adding action to may_read_from:\n");
1301                                 if (DBG_ENABLED()) {
1302                                         act->print();
1303                                         curr->print();
1304                                 }
1305                                 curr->get_node()->add_read_from(act);
1306                         }
1307
1308                         /* Include at most one act per-thread that "happens before" curr */
1309                         if (act->happens_before(curr)) {
1310                                 initialized = true;
1311                                 break;
1312                         }
1313                 }
1314         }
1315
1316         if (!initialized) {
1317                 /** @todo Need a more informative way of reporting errors. */
1318                 printf("ERROR: may read from uninitialized atomic\n");
1319         }
1320
1321         if (DBG_ENABLED() || !initialized) {
1322                 printf("Reached read action:\n");
1323                 curr->print();
1324                 printf("Printing may_read_from\n");
1325                 curr->get_node()->print_may_read_from();
1326                 printf("End printing may_read_from\n");
1327         }
1328
1329         ASSERT(initialized);
1330 }
1331
1332 static void print_list(action_list_t *list)
1333 {
1334         action_list_t::iterator it;
1335
1336         printf("---------------------------------------------------------------------\n");
1337         printf("Trace:\n");
1338
1339         for (it = list->begin(); it != list->end(); it++) {
1340                 (*it)->print();
1341         }
1342         printf("---------------------------------------------------------------------\n");
1343 }
1344
1345 void ModelChecker::print_summary()
1346 {
1347         printf("\n");
1348         printf("Number of executions: %d\n", num_executions);
1349         printf("Number of feasible executions: %d\n", num_feasible_executions);
1350         printf("Total nodes created: %d\n", node_stack->get_total_nodes());
1351
1352 #if SUPPORT_MOD_ORDER_DUMP
1353         scheduler->print();
1354         char buffername[100];
1355         sprintf(buffername, "exec%u",num_executions);
1356         mo_graph->dumpGraphToFile(buffername);
1357 #endif
1358
1359         if (!isfinalfeasible())
1360                 printf("INFEASIBLE EXECUTION!\n");
1361         print_list(action_trace);
1362         printf("\n");
1363 }
1364
1365 /**
1366  * Add a Thread to the system for the first time. Should only be called once
1367  * per thread.
1368  * @param t The Thread to add
1369  */
1370 void ModelChecker::add_thread(Thread *t)
1371 {
1372         thread_map->put(id_to_int(t->get_id()), t);
1373         scheduler->add_thread(t);
1374 }
1375
1376 void ModelChecker::remove_thread(Thread *t)
1377 {
1378         scheduler->remove_thread(t);
1379 }
1380
1381 /**
1382  * Switch from a user-context to the "master thread" context (a.k.a. system
1383  * context). This switch is made with the intention of exploring a particular
1384  * model-checking action (described by a ModelAction object). Must be called
1385  * from a user-thread context.
1386  * @param act The current action that will be explored. Must not be NULL.
1387  * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
1388  */
1389 int ModelChecker::switch_to_master(ModelAction *act)
1390 {
1391         DBG();
1392         Thread *old = thread_current();
1393         set_current_action(act);
1394         old->set_state(THREAD_READY);
1395         return Thread::swap(old, &system_context);
1396 }
1397
1398 /**
1399  * Takes the next step in the execution, if possible.
1400  * @return Returns true (success) if a step was taken and false otherwise.
1401  */
1402 bool ModelChecker::take_step() {
1403         Thread *curr, *next;
1404
1405         if (has_asserted())
1406                 return false;
1407
1408         curr = thread_current();
1409         if (curr) {
1410                 if (curr->get_state() == THREAD_READY) {
1411                         ASSERT(priv->current_action);
1412
1413                         priv->nextThread = check_current_action(priv->current_action);
1414                         priv->current_action = NULL;
1415                         if (!curr->is_blocked() && !curr->is_complete())
1416                                 scheduler->add_thread(curr);
1417                 } else {
1418                         ASSERT(false);
1419                 }
1420         }
1421         next = scheduler->next_thread(priv->nextThread);
1422
1423         /* Infeasible -> don't take any more steps */
1424         if (!isfeasible())
1425                 return false;
1426
1427         if (next)
1428                 next->set_state(THREAD_RUNNING);
1429         DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
1430
1431         /* next == NULL -> don't take any more steps */
1432         if (!next)
1433                 return false;
1434         /* Return false only if swap fails with an error */
1435         return (Thread::swap(&system_context, next) == 0);
1436 }
1437
1438 /** Runs the current execution until threre are no more steps to take. */
1439 void ModelChecker::finish_execution() {
1440         DBG();
1441
1442         while (take_step());
1443 }