model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "action.h"
   5 #include "nodestack.h"
   6 #include "schedule.h"
   7 #include "snapshot-interface.h"
   8 #include "common.h"
   9 #include "clockvector.h"
  10 #include "cyclegraph.h"
  11 #include "promise.h"
  12
  13 #define INITIAL_THREAD_ID       0
  14
  15 ModelChecker *model;
  16
  17 /** @brief Constructor */
  18 ModelChecker::ModelChecker(struct model_params params) :
  19         /* Initialize default scheduler */
  20         scheduler(new Scheduler()),
  21         /* First thread created will have id INITIAL_THREAD_ID */
  22         next_thread_id(INITIAL_THREAD_ID),
  23         used_sequence_numbers(0),
  24         num_executions(0),
  25         params(params),
  26         current_action(NULL),
  27         diverge(NULL),
  28         nextThread(THREAD_ID_T_NONE),
  29         action_trace(new action_list_t()),
  30         thread_map(new HashTable<int, Thread *, int>()),
  31         obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
  32         obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
  33         promises(new std::vector<Promise *>()),
  34         thrd_last_action(new std::vector<ModelAction *>(1)),
  35         node_stack(new NodeStack()),
  36         next_backtrack(NULL),
  37         cyclegraph(new CycleGraph()),
  38         failed_promise(false)
  39 {
  40 }
  41
  42 /** @brief Destructor */
  43 ModelChecker::~ModelChecker()
  44 {
  45         for (int i = 0; i < get_num_threads(); i++)
  46                 delete thread_map->get(i);
  47         delete thread_map;
  48
  49         delete obj_thrd_map;
  50         delete obj_map;
  51         delete action_trace;
  52         delete thrd_last_action;
  53         delete node_stack;
  54         delete scheduler;
  55         delete cyclegraph;
  56 }
  57
  58 /**
  59  * Restores user program to initial state and resets all model-checker data
  60  * structures.
  61  */
  62 void ModelChecker::reset_to_initial_state()
  63 {
  64         DEBUG("+++ Resetting to initial state +++\n");
  65         node_stack->reset_execution();
  66         current_action = NULL;
  67         next_thread_id = INITIAL_THREAD_ID;
  68         used_sequence_numbers = 0;
  69         nextThread = 0;
  70         next_backtrack = NULL;
  71         failed_promise = false;
  72         snapshotObject->backTrackBeforeStep(0);
  73 }
  74
  75 /** @returns a thread ID for a new Thread */
  76 thread_id_t ModelChecker::get_next_id()
  77 {
  78         return next_thread_id++;
  79 }
  80
  81 /** @returns the number of user threads created during this execution */
  82 int ModelChecker::get_num_threads()
  83 {
  84         return next_thread_id;
  85 }
  86
  87 /** @returns a sequence number for a new ModelAction */
  88 modelclock_t ModelChecker::get_next_seq_num()
  89 {
  90         return ++used_sequence_numbers;
  91 }
  92
  93 /**
  94  * Performs the "scheduling" for the model-checker. That is, it checks if the
  95  * model-checker has selected a "next thread to run" and returns it, if
  96  * available. This function should be called from the Scheduler routine, where
  97  * the Scheduler falls back to a default scheduling routine if needed.
  98  *
  99  * @return The next thread chosen by the model-checker. If the model-checker
 100  * makes no selection, retuns NULL.
 101  */
 102 Thread * ModelChecker::schedule_next_thread()
 103 {
 104         Thread *t;
 105         if (nextThread == THREAD_ID_T_NONE)
 106                 return NULL;
 107         t = thread_map->get(id_to_int(nextThread));
 108
 109         ASSERT(t != NULL);
 110
 111         return t;
 112 }
 113
 114 /**
 115  * Choose the next thread in the replay sequence.
 116  *
 117  * If the replay sequence has reached the 'diverge' point, returns a thread
 118  * from the backtracking set. Otherwise, simply returns the next thread in the
 119  * sequence that is being replayed.
 120  */
 121 thread_id_t ModelChecker::get_next_replay_thread()
 122 {
 123         thread_id_t tid;
 124
 125         /* Have we completed exploring the preselected path? */
 126         if (diverge == NULL)
 127                 return THREAD_ID_T_NONE;
 128
 129         /* Else, we are trying to replay an execution */
 130         ModelAction * next = node_stack->get_next()->get_action();
 131
 132         if (next == diverge) {
 133                 Node *nextnode = next->get_node();
 134                 /* Reached divergence point */
 135                 if (nextnode->increment_promise()) {
 136                         /* The next node will try to satisfy a different set of promises. */
 137                         tid = next->get_tid();
 138                         node_stack->pop_restofstack(2);
 139                 } else if (nextnode->increment_read_from()) {
 140                         /* The next node will read from a different value. */
 141                         tid = next->get_tid();
 142                         node_stack->pop_restofstack(2);
 143                 } else if (nextnode->increment_future_value()) {
 144                         /* The next node will try to read from a different future value. */
 145                         tid = next->get_tid();
 146                         node_stack->pop_restofstack(2);
 147                 } else {
 148                         /* Make a different thread execute for next step */
 149                         Node *node = nextnode->get_parent();
 150                         tid = node->get_next_backtrack();
 151                         node_stack->pop_restofstack(1);
 152                 }
 153                 DEBUG("*** Divergence point ***\n");
 154                 diverge = NULL;
 155         } else {
 156                 tid = next->get_tid();
 157         }
 158         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 159         return tid;
 160 }
 161
 162 /**
 163  * Queries the model-checker for more executions to explore and, if one
 164  * exists, resets the model-checker state to execute a new execution.
 165  *
 166  * @return If there are more executions to explore, return true. Otherwise,
 167  * return false.
 168  */
 169 bool ModelChecker::next_execution()
 170 {
 171         DBG();
 172
 173         num_executions++;
 174
 175         bool feasible = isfinalfeasible();
 176         if (feasible || DBG_ENABLED())
 177                 print_summary(feasible);
 178
 179         if ((diverge = model->get_next_backtrack()) == NULL)
 180                 return false;
 181
 182         if (DBG_ENABLED()) {
 183                 printf("Next execution will diverge at:\n");
 184                 diverge->print();
 185         }
 186
 187         model->reset_to_initial_state();
 188         return true;
 189 }
 190
 191 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 192 {
 193         action_type type = act->get_type();
 194
 195         switch (type) {
 196                 case ATOMIC_READ:
 197                 case ATOMIC_WRITE:
 198                 case ATOMIC_RMW:
 199                         break;
 200                 default:
 201                         return NULL;
 202         }
 203         /* linear search: from most recent to oldest */
 204         action_list_t *list = obj_map->ensureptr(act->get_location());
 205         action_list_t::reverse_iterator rit;
 206         for (rit = list->rbegin(); rit != list->rend(); rit++) {
 207                 ModelAction *prev = *rit;
 208                 if (act->is_synchronizing(prev))
 209                         return prev;
 210         }
 211         return NULL;
 212 }
 213
 214 void ModelChecker::set_backtracking(ModelAction *act)
 215 {
 216         ModelAction *prev;
 217         Node *node;
 218         Thread *t = get_thread(act->get_tid());
 219
 220         prev = get_last_conflict(act);
 221         if (prev == NULL)
 222                 return;
 223
 224         node = prev->get_node()->get_parent();
 225
 226         while (!node->is_enabled(t))
 227                 t = t->get_parent();
 228
 229         /* Check if this has been explored already */
 230         if (node->has_been_explored(t->get_id()))
 231                 return;
 232
 233         /* Cache the latest backtracking point */
 234         if (!next_backtrack || *prev > *next_backtrack)
 235                 next_backtrack = prev;
 236
 237         /* If this is a new backtracking point, mark the tree */
 238         if (!node->set_backtrack(t->get_id()))
 239                 return;
 240         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 241                         prev->get_tid(), t->get_id());
 242         if (DBG_ENABLED()) {
 243                 prev->print();
 244                 act->print();
 245         }
 246 }
 247
 248 /**
 249  * Returns last backtracking point. The model checker will explore a different
 250  * path for this point in the next execution.
 251  * @return The ModelAction at which the next execution should diverge.
 252  */
 253 ModelAction * ModelChecker::get_next_backtrack()
 254 {
 255         ModelAction *next = next_backtrack;
 256         next_backtrack = NULL;
 257         return next;
 258 }
 259
 260 void ModelChecker::check_current_action(void)
 261 {
 262         ModelAction *curr = this->current_action;
 263         bool already_added = false;
 264         this->current_action = NULL;
 265         if (!curr) {
 266                 DEBUG("trying to push NULL action...\n");
 267                 return;
 268         }
 269
 270         if (curr->is_rmwc() || curr->is_rmw()) {
 271                 ModelAction *tmp = process_rmw(curr);
 272                 already_added = true;
 273                 delete curr;
 274                 curr = tmp;
 275         } else {
 276                 ModelAction * tmp = node_stack->explore_action(curr);
 277                 if (tmp) {
 278                         /* Discard duplicate ModelAction; use action from NodeStack */
 279                         /* First restore type and order in case of RMW operation */
 280                         if (curr->is_rmwr())
 281                                 tmp->copy_typeandorder(curr);
 282
 283                         /* If we have diverged, we need to reset the clock vector. */
 284                         if (diverge == NULL)
 285                                 tmp->create_cv(get_parent_action(tmp->get_tid()));
 286
 287                         delete curr;
 288                         curr = tmp;
 289                 } else {
 290                         /*
 291                          * Perform one-time actions when pushing new ModelAction onto
 292                          * NodeStack
 293                          */
 294                         curr->create_cv(get_parent_action(curr->get_tid()));
 295                         /* Build may_read_from set */
 296                         if (curr->is_read())
 297                                 build_reads_from_past(curr);
 298                         if (curr->is_write())
 299                                 compute_promises(curr);
 300                 }
 301         }
 302
 303         /* Assign 'creation' parent */
 304         if (curr->get_type() == THREAD_CREATE) {
 305                 Thread *th = (Thread *)curr->get_location();
 306                 th->set_creation(curr);
 307         }
 308
 309         /* Deal with new thread */
 310         if (curr->get_type() == THREAD_START)
 311                 check_promises(NULL, curr->get_cv());
 312
 313         /* Assign reads_from values */
 314         Thread *th = get_thread(curr->get_tid());
 315         uint64_t value = VALUE_NONE;
 316         if (curr->is_read()) {
 317                 const ModelAction *reads_from = curr->get_node()->get_read_from();
 318                 if (reads_from != NULL) {
 319                         value = reads_from->get_value();
 320                         /* Assign reads_from, perform release/acquire synchronization */
 321                         curr->read_from(reads_from);
 322                         r_modification_order(curr,reads_from);
 323                 } else {
 324                         /* Read from future value */
 325                         value = curr->get_node()->get_future_value();
 326                         curr->read_from(NULL);
 327                         Promise * valuepromise = new Promise(curr, value);
 328                         promises->push_back(valuepromise);
 329                 }
 330         } else if (curr->is_write()) {
 331                 w_modification_order(curr);
 332                 resolve_promises(curr);
 333         }
 334
 335         th->set_return_value(value);
 336
 337         /* Add action to list.  */
 338         if (!already_added)
 339                 add_action_to_lists(curr);
 340
 341         /** @todo Is there a better interface for setting the next thread rather
 342                  than this field/convoluted approach?  Perhaps like just returning
 343                  it or something? */
 344
 345         /* Do not split atomic actions. */
 346         if (curr->is_rmwr())
 347                 nextThread = thread_current()->get_id();
 348         else
 349                 nextThread = get_next_replay_thread();
 350
 351         Node *currnode = curr->get_node();
 352         Node *parnode = currnode->get_parent();
 353
 354         if (!parnode->backtrack_empty() || !currnode->read_from_empty() ||
 355                   !currnode->future_value_empty() || !currnode->promise_empty())
 356                 if (!next_backtrack || *curr > *next_backtrack)
 357                         next_backtrack = curr;
 358
 359         set_backtracking(curr);
 360 }
 361
 362 /** @returns whether the current partial trace is feasible. */
 363 bool ModelChecker::isfeasible() {
 364         return !cyclegraph->checkForCycles() && !failed_promise;
 365 }
 366
 367 /** Returns whether the current completed trace is feasible. */
 368 bool ModelChecker::isfinalfeasible() {
 369         return isfeasible() && promises->size() == 0;
 370 }
 371
 372 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
 373 ModelAction * ModelChecker::process_rmw(ModelAction * act) {
 374         int tid = id_to_int(act->get_tid());
 375         ModelAction *lastread = get_last_action(tid);
 376         lastread->process_rmw(act);
 377         if (act->is_rmw())
 378                 cyclegraph->addRMWEdge(lastread, lastread->get_reads_from());
 379         return lastread;
 380 }
 381
 382 /**
 383  * Updates the cyclegraph with the constraints imposed from the current read.
 384  * @param curr The current action. Must be a read.
 385  * @param rf The action that curr reads from. Must be a write.
 386  */
 387 void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *rf) {
 388         std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
 389         unsigned int i;
 390         ASSERT(curr->is_read());
 391
 392         /* Iterate over all threads */
 393         for (i = 0; i < thrd_lists->size(); i++) {
 394                 /* Iterate over actions in thread, starting from most recent */
 395                 action_list_t *list = &(*thrd_lists)[i];
 396                 action_list_t::reverse_iterator rit;
 397                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 398                         ModelAction *act = *rit;
 399
 400                         /* Include at most one act per-thread that "happens before" curr */
 401                         if (act->happens_before(curr)) {
 402                                 if (act->is_read()) {
 403                                         const ModelAction * prevreadfrom = act->get_reads_from();
 404                                         if (prevreadfrom != NULL && rf != prevreadfrom)
 405                                                 cyclegraph->addEdge(rf, prevreadfrom);
 406                                 } else if (rf != act) {
 407                                         cyclegraph->addEdge(rf, act);
 408                                 }
 409                                 break;
 410                         }
 411                 }
 412         }
 413 }
 414
 415 /** Updates the cyclegraph with the constraints imposed from the
 416  *  current read. */
 417 void ModelChecker::post_r_modification_order(ModelAction * curr, const ModelAction *rf) {
 418         std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
 419         unsigned int i;
 420         ASSERT(curr->is_read());
 421
 422         /* Iterate over all threads */
 423         for (i = 0; i < thrd_lists->size(); i++) {
 424                 /* Iterate over actions in thread, starting from most recent */
 425                 action_list_t *list = &(*thrd_lists)[i];
 426                 action_list_t::reverse_iterator rit;
 427                 ModelAction *lastact = NULL;
 428
 429                 /* Find last action that happens after curr */
 430                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 431                         ModelAction *act = *rit;
 432                         if (curr->happens_before(act)) {
 433                                 lastact = act;
 434                         } else
 435                                 break;
 436                 }
 437
 438                         /* Include at most one act per-thread that "happens before" curr */
 439                 if (lastact != NULL) {
 440                         if (lastact->is_read()) {
 441                                 const ModelAction * postreadfrom = lastact->get_reads_from();
 442                                 if (postreadfrom != NULL&&rf != postreadfrom)
 443                                         cyclegraph->addEdge(postreadfrom, rf);
 444                         } else if (rf != lastact) {
 445                                 cyclegraph->addEdge(lastact, rf);
 446                         }
 447                         break;
 448                 }
 449         }
 450 }
 451
 452 /**
 453  * Updates the cyclegraph with the constraints imposed from the current write.
 454  * @param curr The current action. Must be a write.
 455  */
 456 void ModelChecker::w_modification_order(ModelAction * curr) {
 457         std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
 458         unsigned int i;
 459         ASSERT(curr->is_write());
 460
 461         if (curr->is_seqcst()) {
 462                 /* We have to at least see the last sequentially consistent write,
 463                          so we are initialized. */
 464                 ModelAction * last_seq_cst = get_last_seq_cst(curr->get_location());
 465                 if (last_seq_cst != NULL)
 466                         cyclegraph->addEdge(curr, last_seq_cst);
 467         }
 468
 469         /* Iterate over all threads */
 470         for (i = 0; i < thrd_lists->size(); i++) {
 471                 /* Iterate over actions in thread, starting from most recent */
 472                 action_list_t *list = &(*thrd_lists)[i];
 473                 action_list_t::reverse_iterator rit;
 474                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 475                         ModelAction *act = *rit;
 476
 477                         /* Include at most one act per-thread that "happens before" curr */
 478                         if (act->happens_before(curr)) {
 479                                 if (act->is_read()) {
 480                                         cyclegraph->addEdge(curr, act->get_reads_from());
 481                                 } else
 482                                         cyclegraph->addEdge(curr, act);
 483                                 break;
 484                         } else {
 485                                 if (act->is_read()&&!act->is_synchronizing(curr)&&!act->same_thread(curr)) {
 486                                         /* We have an action that:
 487                                                  (1) did not happen before us
 488                                                  (2) is a read and we are a write
 489                                                  (3) cannot synchronize with us
 490                                                  (4) is in a different thread
 491                                                  =>
 492                                                  that read could potentially read from our write.
 493                                         */
 494                                         if (act->get_node()->add_future_value(curr->get_value())&&
 495                                                         (!next_backtrack || *act > * next_backtrack))
 496                                                 next_backtrack = act;
 497                                 }
 498                         }
 499                 }
 500         }
 501 }
 502
 503 /**
 504  * Performs various bookkeeping operations for the current ModelAction. For
 505  * instance, adds action to the per-object, per-thread action vector and to the
 506  * action trace list of all thread actions.
 507  *
 508  * @param act is the ModelAction to add.
 509  */
 510 void ModelChecker::add_action_to_lists(ModelAction *act)
 511 {
 512         int tid = id_to_int(act->get_tid());
 513         action_trace->push_back(act);
 514
 515         obj_map->ensureptr(act->get_location())->push_back(act);
 516
 517         std::vector<action_list_t> *vec = obj_thrd_map->ensureptr(act->get_location());
 518         if (tid >= (int)vec->size())
 519                 vec->resize(next_thread_id);
 520         (*vec)[tid].push_back(act);
 521
 522         if ((int)thrd_last_action->size() <= tid)
 523                 thrd_last_action->resize(get_num_threads());
 524         (*thrd_last_action)[tid] = act;
 525 }
 526
 527 ModelAction * ModelChecker::get_last_action(thread_id_t tid)
 528 {
 529         int nthreads = get_num_threads();
 530         if ((int)thrd_last_action->size() < nthreads)
 531                 thrd_last_action->resize(nthreads);
 532         return (*thrd_last_action)[id_to_int(tid)];
 533 }
 534
 535 /**
 536  * Gets the last memory_order_seq_cst action (in the total global sequence)
 537  * performed on a particular object (i.e., memory location).
 538  * @param location The object location to check
 539  * @return The last seq_cst action performed
 540  */
 541 ModelAction * ModelChecker::get_last_seq_cst(const void *location)
 542 {
 543         action_list_t *list = obj_map->ensureptr(location);
 544         /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
 545         action_list_t::reverse_iterator rit;
 546         for (rit = list->rbegin(); rit != list->rend(); rit++)
 547                 if ((*rit)->is_write() && (*rit)->is_seqcst())
 548                         return *rit;
 549         return NULL;
 550 }
 551
 552 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
 553 {
 554         ModelAction *parent = get_last_action(tid);
 555         if (!parent)
 556                 parent = get_thread(tid)->get_creation();
 557         return parent;
 558 }
 559
 560 /**
 561  * Returns the clock vector for a given thread.
 562  * @param tid The thread whose clock vector we want
 563  * @return Desired clock vector
 564  */
 565 ClockVector * ModelChecker::get_cv(thread_id_t tid) {
 566         return get_parent_action(tid)->get_cv();
 567 }
 568
 569
 570 /** Resolve the given promises. */
 571
 572 void ModelChecker::resolve_promises(ModelAction *write) {
 573         for (unsigned int i = 0, promise_index = 0;promise_index<promises->size(); i++) {
 574                 Promise * promise = (*promises)[promise_index];
 575                 if (write->get_node()->get_promise(i)) {
 576                         ModelAction * read = promise->get_action();
 577                         read->read_from(write);
 578                         r_modification_order(read, write);
 579                         post_r_modification_order(read, write);
 580                         promises->erase(promises->begin()+promise_index);
 581                 } else
 582                         promise_index++;
 583         }
 584 }
 585
 586 /** Compute the set of promises that could potentially be satisfied by
 587  *  this action. */
 588
 589 void ModelChecker::compute_promises(ModelAction *curr) {
 590         for (unsigned int i = 0;i<promises->size();i++) {
 591                 Promise * promise = (*promises)[i];
 592                 const ModelAction * act = promise->get_action();
 593                 if (!act->happens_before(curr)&&
 594                                 act->is_read()&&
 595                                 !act->is_synchronizing(curr)&&
 596                                 !act->same_thread(curr)&&
 597                                 promise->get_value() == curr->get_value()) {
 598                         curr->get_node()->set_promise(i);
 599                 }
 600         }
 601 }
 602
 603 /** Checks promises in response to change in ClockVector Threads. */
 604
 605 void ModelChecker::check_promises(ClockVector *old_cv, ClockVector * merge_cv) {
 606         for (unsigned int i = 0;i<promises->size();i++) {
 607                 Promise * promise = (*promises)[i];
 608                 const ModelAction * act = promise->get_action();
 609                 if ((old_cv == NULL||!old_cv->synchronized_since(act))&&
 610                                 merge_cv->synchronized_since(act)) {
 611                         //This thread is no longer able to send values back to satisfy the promise
 612                         int num_synchronized_threads = promise->increment_threads();
 613                         if (num_synchronized_threads == model->get_num_threads()) {
 614                                 //Promise has failed
 615                                 failed_promise = true;
 616                                 return;
 617                         }
 618                 }
 619         }
 620 }
 621
 622 /**
 623  * Build up an initial set of all past writes that this 'read' action may read
 624  * from. This set is determined by the clock vector's "happens before"
 625  * relationship.
 626  * @param curr is the current ModelAction that we are exploring; it must be a
 627  * 'read' operation.
 628  */
 629 void ModelChecker::build_reads_from_past(ModelAction *curr)
 630 {
 631         std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
 632         unsigned int i;
 633         ASSERT(curr->is_read());
 634
 635         ModelAction *last_seq_cst = NULL;
 636
 637         /* Track whether this object has been initialized */
 638         bool initialized = false;
 639
 640         if (curr->is_seqcst()) {
 641                 last_seq_cst = get_last_seq_cst(curr->get_location());
 642                 /* We have to at least see the last sequentially consistent write,
 643                          so we are initialized. */
 644                 if (last_seq_cst != NULL)
 645                         initialized = true;
 646         }
 647
 648         /* Iterate over all threads */
 649         for (i = 0; i < thrd_lists->size(); i++) {
 650                 /* Iterate over actions in thread, starting from most recent */
 651                 action_list_t *list = &(*thrd_lists)[i];
 652                 action_list_t::reverse_iterator rit;
 653                 for (rit = list->rbegin(); rit != list->rend(); rit++) {
 654                         ModelAction *act = *rit;
 655
 656                         /* Only consider 'write' actions */
 657                         if (!act->is_write())
 658                                 continue;
 659
 660                         /* Don't consider more than one seq_cst write if we are a seq_cst read. */
 661                         if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
 662                                 DEBUG("Adding action to may_read_from:\n");
 663                                 if (DBG_ENABLED()) {
 664                                         act->print();
 665                                         curr->print();
 666                                 }
 667                                 curr->get_node()->add_read_from(act);
 668                         }
 669
 670                         /* Include at most one act per-thread that "happens before" curr */
 671                         if (act->happens_before(curr)) {
 672                                 initialized = true;
 673                                 break;
 674                         }
 675                 }
 676         }
 677
 678         if (!initialized) {
 679                 /** @todo Need a more informative way of reporting errors. */
 680                 printf("ERROR: may read from uninitialized atomic\n");
 681         }
 682
 683         if (DBG_ENABLED() || !initialized) {
 684                 printf("Reached read action:\n");
 685                 curr->print();
 686                 printf("Printing may_read_from\n");
 687                 curr->get_node()->print_may_read_from();
 688                 printf("End printing may_read_from\n");
 689         }
 690
 691         ASSERT(initialized);
 692 }
 693
 694 static void print_list(action_list_t *list)
 695 {
 696         action_list_t::iterator it;
 697
 698         printf("---------------------------------------------------------------------\n");
 699         printf("Trace:\n");
 700
 701         for (it = list->begin(); it != list->end(); it++) {
 702                 (*it)->print();
 703         }
 704         printf("---------------------------------------------------------------------\n");
 705 }
 706
 707 void ModelChecker::print_summary(bool feasible)
 708 {
 709         printf("\n");
 710         printf("Number of executions: %d\n", num_executions);
 711         printf("Total nodes created: %d\n", node_stack->get_total_nodes());
 712
 713         scheduler->print();
 714
 715         if (!feasible)
 716                 printf("INFEASIBLE EXECUTION!\n");
 717         print_list(action_trace);
 718         printf("\n");
 719 }
 720
 721 int ModelChecker::add_thread(Thread *t)
 722 {
 723         thread_map->put(id_to_int(t->get_id()), t);
 724         scheduler->add_thread(t);
 725         return 0;
 726 }
 727
 728 void ModelChecker::remove_thread(Thread *t)
 729 {
 730         scheduler->remove_thread(t);
 731 }
 732
 733 /**
 734  * Switch from a user-context to the "master thread" context (a.k.a. system
 735  * context). This switch is made with the intention of exploring a particular
 736  * model-checking action (described by a ModelAction object). Must be called
 737  * from a user-thread context.
 738  * @param act The current action that will be explored. May be NULL, although
 739  * there is little reason to switch to the model-checker without an action to
 740  * explore (note: act == NULL is sometimes used as a hack to allow a thread to
 741  * yield control without performing any progress; see thrd_join()).
 742  * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
 743  */
 744 int ModelChecker::switch_to_master(ModelAction *act)
 745 {
 746         DBG();
 747         Thread * old = thread_current();
 748         set_current_action(act);
 749         old->set_state(THREAD_READY);
 750         return Thread::swap(old, get_system_context());
 751 }