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() :
  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         current_action(NULL),
  26         diverge(NULL),
  27         nextThread(THREAD_ID_T_NONE),
  28         action_trace(new action_list_t()),
  29         thread_map(new HashTable<int, Thread *, int>()),
  30         obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
  31         obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
  32         promises(new std::vector<Promise *>()),
  33         thrd_last_action(new std::vector<ModelAction *>(1)),
  34         node_stack(new NodeStack()),
  35         next_backtrack(NULL),
  36         cyclegraph(new CycleGraph()),
  37         failed_promise(false)
  38 {
  39 }
  40
  41 /** @brief Destructor */
  42 ModelChecker::~ModelChecker()
  43 {
  44         for (int i = 0; i < get_num_threads(); i++)
  45                 delete thread_map->get(i);
  46         delete thread_map;
  47
  48         delete obj_thrd_map;
  49         delete obj_map;
  50         delete action_trace;
  51         delete thrd_last_action;
  52         delete node_stack;
  53         delete scheduler;
  54         delete cyclegraph;
  55 }
  56
  57 /**
  58  * Restores user program to initial state and resets all model-checker data
  59  * structures.
  60  */
  61 void ModelChecker::reset_to_initial_state()
  62 {
  63         DEBUG("+++ Resetting to initial state +++\n");
  64         node_stack->reset_execution();
  65         current_action = NULL;
  66         next_thread_id = INITIAL_THREAD_ID;
  67         used_sequence_numbers = 0;
  68         nextThread = 0;
  69         next_backtrack = NULL;
  70         failed_promise = false;
  71         snapshotObject->backTrackBeforeStep(0);
  72 }
  73
  74 /** @returns a thread ID for a new Thread */
  75 thread_id_t ModelChecker::get_next_id()
  76 {
  77         return next_thread_id++;
  78 }
  79
  80 /** @returns the number of user threads created during this execution */
  81 int ModelChecker::get_num_threads()
  82 {
  83         return next_thread_id;
  84 }
  85
  86 /** @returns a sequence number for a new ModelAction */
  87 modelclock_t ModelChecker::get_next_seq_num()
  88 {
  89         return ++used_sequence_numbers;
  90 }
  91
  92 /**
  93  * Performs the "scheduling" for the model-checker. That is, it checks if the
  94  * model-checker has selected a "next thread to run" and returns it, if
  95  * available. This function should be called from the Scheduler routine, where
  96  * the Scheduler falls back to a default scheduling routine if needed.
  97  *
  98  * @return The next thread chosen by the model-checker. If the model-checker
  99  * makes no selection, retuns NULL.
 100  */
 101 Thread * ModelChecker::schedule_next_thread()
 102 {
 103         Thread *t;
 104         if (nextThread == THREAD_ID_T_NONE)
 105                 return NULL;
 106         t = thread_map->get(id_to_int(nextThread));
 107
 108         ASSERT(t != NULL);
 109
 110         return t;
 111 }
 112
 113 /**
 114  * Choose the next thread in the replay sequence.
 115  *
 116  * If the replay sequence has reached the 'diverge' point, returns a thread
 117  * from the backtracking set. Otherwise, simply returns the next thread in the
 118  * sequence that is being replayed.
 119  */
 120 thread_id_t ModelChecker::get_next_replay_thread()
 121 {
 122         thread_id_t tid;
 123
 124         /* Have we completed exploring the preselected path? */
 125         if (diverge == NULL)
 126                 return THREAD_ID_T_NONE;
 127
 128         /* Else, we are trying to replay an execution */
 129         ModelAction * next = node_stack->get_next()->get_action();
 130
 131         if (next == diverge) {
 132                 Node *nextnode = next->get_node();
 133                 /* Reached divergence point */
 134                 if (nextnode->increment_promise()) {
 135                         /* The next node will try to satisfy a different set of promises. */
 136                         tid = next->get_tid();
 137                         node_stack->pop_restofstack(2);
 138                 } else if (nextnode->increment_read_from()) {
 139                         /* The next node will read from a different value. */
 140                         tid = next->get_tid();
 141                         node_stack->pop_restofstack(2);
 142                 } else if (nextnode->increment_future_value()) {
 143                         /* The next node will try to read from a different future value. */
 144                         tid = next->get_tid();
 145                         node_stack->pop_restofstack(2);
 146                 } else {
 147                         /* Make a different thread execute for next step */
 148                         Node *node = nextnode->get_parent();
 149                         tid = node->get_next_backtrack();
 150                         node_stack->pop_restofstack(1);
 151                 }
 152                 DEBUG("*** Divergence point ***\n");
 153                 diverge = NULL;
 154         } else {
 155                 tid = next->get_tid();
 156         }
 157         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 158         return tid;
 159 }
 160
 161 /**
 162  * Queries the model-checker for more executions to explore and, if one
 163  * exists, resets the model-checker state to execute a new execution.
 164  *
 165  * @return If there are more executions to explore, return true. Otherwise,
 166  * return false.
 167  */
 168 bool ModelChecker::next_execution()
 169 {
 170         DBG();
 171
 172         num_executions++;
 173
 174         if (isfinalfeasible() || DBG_ENABLED())
 175                 print_summary();
 176
 177         if ((diverge = model->get_next_backtrack()) == NULL)
 178                 return false;
 179
 180         if (DBG_ENABLED()) {
 181                 printf("Next execution will diverge at:\n");
 182                 diverge->print();
 183         }
 184
 185         model->reset_to_initial_state();
 186         return true;
 187 }
 188
 189 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 190 {
 191         action_type type = act->get_type();
 192
 193         switch (type) {
 194                 case ATOMIC_READ:
 195                 case ATOMIC_WRITE:
 196                 case ATOMIC_RMW:
 197                         break;
 198                 default:
 199                         return NULL;
 200         }
 201         /* linear search: from most recent to oldest */
 202         action_list_t *list = obj_map->ensureptr(act->get_location());
 203         action_list_t::reverse_iterator rit;
 204         for (rit = list->rbegin(); rit != list->rend(); rit++) {
 205                 ModelAction *prev = *rit;
 206                 if (act->is_synchronizing(prev))
 207                         return prev;
 208         }
 209         return NULL;
 210 }
 211
 212 void ModelChecker::set_backtracking(ModelAction *act)
 213 {
 214         ModelAction *prev;
 215         Node *node;
 216         Thread *t = get_thread(act->get_tid());
 217
 218         prev = get_last_conflict(act);
 219         if (prev == NULL)
 220                 return;
 221
 222         node = prev->get_node()->get_parent();
 223
 224         while (!node->is_enabled(t))
 225                 t = t->get_parent();
 226
 227         /* Check if this has been explored already */
 228         if (node->has_been_explored(t->get_id()))
 229                 return;
 230
 231         /* Cache the latest backtracking point */
 232         if (!next_backtrack || *prev > *next_backtrack)
 233                 next_backtrack = prev;
 234
 235         /* If this is a new backtracking point, mark the tree */
 236         if (!node->set_backtrack(t->get_id()))
 237                 return;
 238         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 239                         prev->get_tid(), t->get_id());
 240         if (DBG_ENABLED()) {
 241                 prev->print();
 242                 act->print();
 243         }
 244 }
 245
 246 /**
 247  * Returns last backtracking point. The model checker will explore a different
 248  * path for this point in the next execution.
 249  * @return The ModelAction at which the next execution should diverge.
 250  */
 251 ModelAction * ModelChecker::get_next_backtrack()
 252 {
 253         ModelAction *next = next_backtrack;
 254         next_backtrack = NULL;
 255         return next;
 256 }
 257
 258 void ModelChecker::check_current_action(void)
 259 {
 260         ModelAction *curr = this->current_action;
 261         bool already_added = false;
 262         this->current_action = NULL;
 263         if (!curr) {
 264                 DEBUG("trying to push NULL action...\n");
 265                 return;
 266         }
 267
 268         if (curr->is_rmwc()||curr->is_rmw()) {
 269                 ModelAction *tmp=process_rmw(curr);
 270                 already_added = true;
 271                 delete curr;
 272                 curr=tmp;
 273         } else {
 274                 ModelAction * tmp = node_stack->explore_action(curr);
 275                 if (tmp) {
 276                         /* Discard duplicate ModelAction; use action from NodeStack */
 277                         /* First restore type and order in case of RMW operation */
 278                         if (curr->is_rmwr())
 279                                 tmp->copy_typeandorder(curr);
 280
 281                         /* If we have diverged, we need to reset the clock vector. */
 282                         if (diverge==NULL) {
 283                                 tmp->create_cv(get_parent_action(tmp->get_tid()));
 284                         }
 285
 286                         delete curr;
 287                         curr = tmp;
 288                 } else {
 289                         /*
 290                          * Perform one-time actions when pushing new ModelAction onto
 291                          * NodeStack
 292                          */
 293                         curr->create_cv(get_parent_action(curr->get_tid()));
 294                         /* Build may_read_from set */
 295                         if (curr->is_read())
 296                                 build_reads_from_past(curr);
 297                         if (curr->is_write())
 298                                 compute_promises(curr);
 299                 }
 300         }
 301
 302         /* Assign 'creation' parent */
 303         if (curr->get_type() == THREAD_CREATE) {
 304                 Thread *th = (Thread *)curr->get_location();
 305                 th->set_creation(curr);
 306         }
 307
 308         /* Deal with new thread */
 309         if (curr->get_type() == THREAD_START) {
 310                 check_promises(NULL, curr->get_cv());
 311         }
 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         /* 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
 352         Node *currnode = curr->get_node();
 353         Node *parnode = currnode->get_parent();
 354
 355         if (!parnode->backtrack_empty()||!currnode->read_from_empty()||!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(void)
 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 (!isfinalfeasible())
 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 }