execution.cc

   1 #include <stdio.h>
   2 #include <algorithm>
   3 #include <new>
   4 #include <stdarg.h>
   5
   6 #include "model.h"
   7 #include "execution.h"
   8 #include "action.h"
   9 #include "schedule.h"
  10 #include "common.h"
  11 #include "clockvector.h"
  12 #include "cyclegraph.h"
  13 #include "datarace.h"
  14 #include "threads-model.h"
  15 #include "bugmessage.h"
  16 #include "history.h"
  17 #include "fuzzer.h"
  18
  19 #define INITIAL_THREAD_ID       0
  20
  21 /**
  22  * Structure for holding small ModelChecker members that should be snapshotted
  23  */
  24 struct model_snapshot_members {
  25         model_snapshot_members() :
  26                 /* First thread created will have id INITIAL_THREAD_ID */
  27                 next_thread_id(INITIAL_THREAD_ID),
  28                 used_sequence_numbers(0),
  29                 bugs(),
  30                 bad_synchronization(false),
  31                 asserted(false)
  32         { }
  33
  34         ~model_snapshot_members() {
  35                 for (unsigned int i = 0;i < bugs.size();i++)
  36                         delete bugs[i];
  37                 bugs.clear();
  38         }
  39
  40         unsigned int next_thread_id;
  41         modelclock_t used_sequence_numbers;
  42         SnapVector<bug_message *> bugs;
  43         /** @brief Incorrectly-ordered synchronization was made */
  44         bool bad_synchronization;
  45         bool asserted;
  46
  47         SNAPSHOTALLOC
  48 };
  49
  50 /** @brief Constructor */
  51 ModelExecution::ModelExecution(ModelChecker *m, Scheduler *scheduler) :
  52         model(m),
  53         params(NULL),
  54         scheduler(scheduler),
  55         action_trace(),
  56         thread_map(2),  /* We'll always need at least 2 threads */
  57         pthread_map(0),
  58         pthread_counter(1),
  59         obj_map(),
  60         condvar_waiters_map(),
  61         obj_thrd_map(),
  62         mutex_map(),
  63         thrd_last_action(1),
  64         thrd_last_fence_release(),
  65         priv(new struct model_snapshot_members ()),
  66         mo_graph(new CycleGraph()),
  67         fuzzer(new Fuzzer()),
  68         thrd_func_list(),
  69         thrd_func_inst_lists()
  70 {
  71         /* Initialize a model-checker thread, for special ModelActions */
  72         model_thread = new Thread(get_next_id());
  73         add_thread(model_thread);
  74         scheduler->register_engine(this);
  75 }
  76
  77 /** @brief Destructor */
  78 ModelExecution::~ModelExecution()
  79 {
  80         for (unsigned int i = 0;i < get_num_threads();i++)
  81                 delete get_thread(int_to_id(i));
  82
  83         delete mo_graph;
  84         delete priv;
  85 }
  86
  87 int ModelExecution::get_execution_number() const
  88 {
  89         return model->get_execution_number();
  90 }
  91
  92 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
  93 {
  94         action_list_t *tmp = hash->get(ptr);
  95         if (tmp == NULL) {
  96                 tmp = new action_list_t();
  97                 hash->put(ptr, tmp);
  98         }
  99         return tmp;
 100 }
 101
 102 static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
 103 {
 104         SnapVector<action_list_t> *tmp = hash->get(ptr);
 105         if (tmp == NULL) {
 106                 tmp = new SnapVector<action_list_t>();
 107                 hash->put(ptr, tmp);
 108         }
 109         return tmp;
 110 }
 111
 112 /** @return a thread ID for a new Thread */
 113 thread_id_t ModelExecution::get_next_id()
 114 {
 115         return priv->next_thread_id++;
 116 }
 117
 118 /** @return the number of user threads created during this execution */
 119 unsigned int ModelExecution::get_num_threads() const
 120 {
 121         return priv->next_thread_id;
 122 }
 123
 124 /** @return a sequence number for a new ModelAction */
 125 modelclock_t ModelExecution::get_next_seq_num()
 126 {
 127         return ++priv->used_sequence_numbers;
 128 }
 129
 130 /**
 131  * @brief Should the current action wake up a given thread?
 132  *
 133  * @param curr The current action
 134  * @param thread The thread that we might wake up
 135  * @return True, if we should wake up the sleeping thread; false otherwise
 136  */
 137 bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
 138 {
 139         const ModelAction *asleep = thread->get_pending();
 140         /* Don't allow partial RMW to wake anyone up */
 141         if (curr->is_rmwr())
 142                 return false;
 143         /* Synchronizing actions may have been backtracked */
 144         if (asleep->could_synchronize_with(curr))
 145                 return true;
 146         /* All acquire/release fences and fence-acquire/store-release */
 147         if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
 148                 return true;
 149         /* Fence-release + store can awake load-acquire on the same location */
 150         if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
 151                 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
 152                 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
 153                         return true;
 154         }
 155         return false;
 156 }
 157
 158 void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
 159 {
 160         for (unsigned int i = 0;i < get_num_threads();i++) {
 161                 Thread *thr = get_thread(int_to_id(i));
 162                 if (scheduler->is_sleep_set(thr)) {
 163                         if (should_wake_up(curr, thr))
 164                                 /* Remove this thread from sleep set */
 165                                 scheduler->remove_sleep(thr);
 166                 }
 167         }
 168 }
 169
 170 /** @brief Alert the model-checker that an incorrectly-ordered
 171  * synchronization was made */
 172 void ModelExecution::set_bad_synchronization()
 173 {
 174         priv->bad_synchronization = true;
 175 }
 176
 177 bool ModelExecution::assert_bug(const char *msg)
 178 {
 179         priv->bugs.push_back(new bug_message(msg));
 180
 181         if (isfeasibleprefix()) {
 182                 set_assert();
 183                 return true;
 184         }
 185         return false;
 186 }
 187
 188 /** @return True, if any bugs have been reported for this execution */
 189 bool ModelExecution::have_bug_reports() const
 190 {
 191         return priv->bugs.size() != 0;
 192 }
 193
 194 /** @return True, if any fatal bugs have been reported for this execution.
 195  *  Any bug other than a data race is considered a fatal bug. Data races
 196  *  are not considered fatal unless the number of races is exceeds
 197  *  a threshold (temporarily set as 15).
 198  */
 199 bool ModelExecution::have_fatal_bug_reports() const
 200 {
 201         return priv->bugs.size() != 0;
 202 }
 203
 204 SnapVector<bug_message *> * ModelExecution::get_bugs() const
 205 {
 206         return &priv->bugs;
 207 }
 208
 209 /**
 210  * Check whether the current trace has triggered an assertion which should halt
 211  * its execution.
 212  *
 213  * @return True, if the execution should be aborted; false otherwise
 214  */
 215 bool ModelExecution::has_asserted() const
 216 {
 217         return priv->asserted;
 218 }
 219
 220 /**
 221  * Trigger a trace assertion which should cause this execution to be halted.
 222  * This can be due to a detected bug or due to an infeasibility that should
 223  * halt ASAP.
 224  */
 225 void ModelExecution::set_assert()
 226 {
 227         priv->asserted = true;
 228 }
 229
 230 /**
 231  * Check if we are in a deadlock. Should only be called at the end of an
 232  * execution, although it should not give false positives in the middle of an
 233  * execution (there should be some ENABLED thread).
 234  *
 235  * @return True if program is in a deadlock; false otherwise
 236  */
 237 bool ModelExecution::is_deadlocked() const
 238 {
 239         bool blocking_threads = false;
 240         for (unsigned int i = 0;i < get_num_threads();i++) {
 241                 thread_id_t tid = int_to_id(i);
 242                 if (is_enabled(tid))
 243                         return false;
 244                 Thread *t = get_thread(tid);
 245                 if (!t->is_model_thread() && t->get_pending())
 246                         blocking_threads = true;
 247         }
 248         return blocking_threads;
 249 }
 250
 251 /**
 252  * Check if this is a complete execution. That is, have all thread completed
 253  * execution (rather than exiting because sleep sets have forced a redundant
 254  * execution).
 255  *
 256  * @return True if the execution is complete.
 257  */
 258 bool ModelExecution::is_complete_execution() const
 259 {
 260         for (unsigned int i = 0;i < get_num_threads();i++)
 261                 if (is_enabled(int_to_id(i)))
 262                         return false;
 263         return true;
 264 }
 265
 266 ModelAction * ModelExecution::convertNonAtomicStore(void * location) {
 267         uint64_t value = *((const uint64_t *) location);
 268         modelclock_t storeclock;
 269         thread_id_t storethread;
 270         getStoreThreadAndClock(location, &storethread, &storeclock);
 271         setAtomicStoreFlag(location);
 272         ModelAction * act = new ModelAction(NONATOMIC_WRITE, memory_order_relaxed, location, value, get_thread(storethread));
 273         act->set_seq_number(storeclock);
 274         add_normal_write_to_lists(act);
 275         add_write_to_lists(act);
 276         w_modification_order(act);
 277         return act;
 278 }
 279
 280
 281 /**
 282  * Processes a read model action.
 283  * @param curr is the read model action to process.
 284  * @param rf_set is the set of model actions we can possibly read from
 285  * @return True if processing this read updates the mo_graph.
 286  */
 287 void ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> * rf_set)
 288 {
 289         SnapVector<const ModelAction *> * priorset = new SnapVector<const ModelAction *>();
 290         bool hasnonatomicstore = hasNonAtomicStore(curr->get_location());
 291         if (hasnonatomicstore) {
 292                 ModelAction * nonatomicstore = convertNonAtomicStore(curr->get_location());
 293                 rf_set->push_back(nonatomicstore);
 294         }
 295
 296         while(true) {
 297                 int index = fuzzer->selectWrite(curr, rf_set);
 298                 ModelAction *rf = (*rf_set)[index];
 299
 300
 301                 ASSERT(rf);
 302                 bool canprune = false;
 303                 if (r_modification_order(curr, rf, priorset, &canprune)) {
 304                         for(unsigned int i=0;i<priorset->size();i++) {
 305                                 mo_graph->addEdge((*priorset)[i], rf);
 306                         }
 307                         read_from(curr, rf);
 308                         get_thread(curr)->set_return_value(curr->get_return_value());
 309                         delete priorset;
 310                         if (canprune && curr->get_type() == ATOMIC_READ) {
 311                                 int tid = id_to_int(curr->get_tid());
 312                                 (*obj_thrd_map.get(curr->get_location()))[tid].pop_back();
 313                         }
 314                         return;
 315                 }
 316                 priorset->clear();
 317                 (*rf_set)[index] = rf_set->back();
 318                 rf_set->pop_back();
 319         }
 320 }
 321
 322 /**
 323  * Processes a lock, trylock, or unlock model action.  @param curr is
 324  * the read model action to process.
 325  *
 326  * The try lock operation checks whether the lock is taken.  If not,
 327  * it falls to the normal lock operation case.  If so, it returns
 328  * fail.
 329  *
 330  * The lock operation has already been checked that it is enabled, so
 331  * it just grabs the lock and synchronizes with the previous unlock.
 332  *
 333  * The unlock operation has to re-enable all of the threads that are
 334  * waiting on the lock.
 335  *
 336  * @return True if synchronization was updated; false otherwise
 337  */
 338 bool ModelExecution::process_mutex(ModelAction *curr)
 339 {
 340         cdsc::mutex *mutex = curr->get_mutex();
 341         struct cdsc::mutex_state *state = NULL;
 342
 343         if (mutex)
 344                 state = mutex->get_state();
 345
 346         switch (curr->get_type()) {
 347         case ATOMIC_TRYLOCK: {
 348                 bool success = !state->locked;
 349                 curr->set_try_lock(success);
 350                 if (!success) {
 351                         get_thread(curr)->set_return_value(0);
 352                         break;
 353                 }
 354                 get_thread(curr)->set_return_value(1);
 355         }
 356         //otherwise fall into the lock case
 357         case ATOMIC_LOCK: {
 358                 //TODO: FIND SOME BETTER WAY TO CHECK LOCK INITIALIZED OR NOT
 359                 //if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
 360                 //      assert_bug("Lock access before initialization");
 361                 state->locked = get_thread(curr);
 362                 ModelAction *unlock = get_last_unlock(curr);
 363                 //synchronize with the previous unlock statement
 364                 if (unlock != NULL) {
 365                         synchronize(unlock, curr);
 366                         return true;
 367                 }
 368                 break;
 369         }
 370         case ATOMIC_WAIT:
 371         case ATOMIC_UNLOCK: {
 372                 //TODO: FIX WAIT SITUATION...WAITS CAN SPURIOUSLY FAIL...TIMED WAITS SHOULD PROBABLY JUST BE THE SAME AS NORMAL WAITS...THINK ABOUT PROBABILITIES THOUGH....AS IN TIMED WAIT MUST FAIL TO GUARANTEE PROGRESS...NORMAL WAIT MAY FAIL...SO NEED NORMAL WAIT TO WORK CORRECTLY IN THE CASE IT SPURIOUSLY FAILS AND IN THE CASE IT DOESN'T...  TIMED WAITS MUST EVENMTUALLY RELEASE...
 373
 374                 /* wake up the other threads */
 375                 for (unsigned int i = 0;i < get_num_threads();i++) {
 376                         Thread *t = get_thread(int_to_id(i));
 377                         Thread *curr_thrd = get_thread(curr);
 378                         if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
 379                                 scheduler->wake(t);
 380                 }
 381
 382                 /* unlock the lock - after checking who was waiting on it */
 383                 state->locked = NULL;
 384
 385                 if (!curr->is_wait())
 386                         break;/* The rest is only for ATOMIC_WAIT */
 387
 388                 break;
 389         }
 390         case ATOMIC_NOTIFY_ALL: {
 391                 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
 392                 //activate all the waiting threads
 393                 for (action_list_t::iterator rit = waiters->begin();rit != waiters->end();rit++) {
 394                         scheduler->wake(get_thread(*rit));
 395                 }
 396                 waiters->clear();
 397                 break;
 398         }
 399         case ATOMIC_NOTIFY_ONE: {
 400                 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
 401                 if (waiters->size() != 0) {
 402                         Thread * thread = fuzzer->selectNotify(waiters);
 403                         scheduler->wake(thread);
 404                 }
 405                 break;
 406         }
 407
 408         default:
 409                 ASSERT(0);
 410         }
 411         return false;
 412 }
 413
 414 /**
 415  * Process a write ModelAction
 416  * @param curr The ModelAction to process
 417  * @return True if the mo_graph was updated or promises were resolved
 418  */
 419 void ModelExecution::process_write(ModelAction *curr)
 420 {
 421         w_modification_order(curr);
 422         get_thread(curr)->set_return_value(VALUE_NONE);
 423 }
 424
 425 /**
 426  * Process a fence ModelAction
 427  * @param curr The ModelAction to process
 428  * @return True if synchronization was updated
 429  */
 430 bool ModelExecution::process_fence(ModelAction *curr)
 431 {
 432         /*
 433          * fence-relaxed: no-op
 434          * fence-release: only log the occurence (not in this function), for
 435          *   use in later synchronization
 436          * fence-acquire (this function): search for hypothetical release
 437          *   sequences
 438          * fence-seq-cst: MO constraints formed in {r,w}_modification_order
 439          */
 440         bool updated = false;
 441         if (curr->is_acquire()) {
 442                 action_list_t *list = &action_trace;
 443                 action_list_t::reverse_iterator rit;
 444                 /* Find X : is_read(X) && X --sb-> curr */
 445                 for (rit = list->rbegin();rit != list->rend();rit++) {
 446                         ModelAction *act = *rit;
 447                         if (act == curr)
 448                                 continue;
 449                         if (act->get_tid() != curr->get_tid())
 450                                 continue;
 451                         /* Stop at the beginning of the thread */
 452                         if (act->is_thread_start())
 453                                 break;
 454                         /* Stop once we reach a prior fence-acquire */
 455                         if (act->is_fence() && act->is_acquire())
 456                                 break;
 457                         if (!act->is_read())
 458                                 continue;
 459                         /* read-acquire will find its own release sequences */
 460                         if (act->is_acquire())
 461                                 continue;
 462
 463                         /* Establish hypothetical release sequences */
 464                         ClockVector *cv = get_hb_from_write(act);
 465                         if (curr->get_cv()->merge(cv))
 466                                 updated = true;
 467                 }
 468         }
 469         return updated;
 470 }
 471
 472 /**
 473  * @brief Process the current action for thread-related activity
 474  *
 475  * Performs current-action processing for a THREAD_* ModelAction. Proccesses
 476  * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
 477  * synchronization, etc.  This function is a no-op for non-THREAD actions
 478  * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
 479  *
 480  * @param curr The current action
 481  * @return True if synchronization was updated or a thread completed
 482  */
 483 bool ModelExecution::process_thread_action(ModelAction *curr)
 484 {
 485         bool updated = false;
 486
 487         switch (curr->get_type()) {
 488         case THREAD_CREATE: {
 489                 thrd_t *thrd = (thrd_t *)curr->get_location();
 490                 struct thread_params *params = (struct thread_params *)curr->get_value();
 491                 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
 492                 curr->set_thread_operand(th);
 493                 add_thread(th);
 494                 th->set_creation(curr);
 495                 break;
 496         }
 497         case PTHREAD_CREATE: {
 498                 (*(uint32_t *)curr->get_location()) = pthread_counter++;
 499
 500                 struct pthread_params *params = (struct pthread_params *)curr->get_value();
 501                 Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
 502                 curr->set_thread_operand(th);
 503                 add_thread(th);
 504                 th->set_creation(curr);
 505
 506                 if ( pthread_map.size() < pthread_counter )
 507                         pthread_map.resize( pthread_counter );
 508                 pthread_map[ pthread_counter-1 ] = th;
 509
 510                 break;
 511         }
 512         case THREAD_JOIN: {
 513                 Thread *blocking = curr->get_thread_operand();
 514                 ModelAction *act = get_last_action(blocking->get_id());
 515                 synchronize(act, curr);
 516                 updated = true; /* trigger rel-seq checks */
 517                 break;
 518         }
 519         case PTHREAD_JOIN: {
 520                 Thread *blocking = curr->get_thread_operand();
 521                 ModelAction *act = get_last_action(blocking->get_id());
 522                 synchronize(act, curr);
 523                 updated = true; /* trigger rel-seq checks */
 524                 break;  // WL: to be add (modified)
 525         }
 526
 527         case THREAD_FINISH: {
 528                 Thread *th = get_thread(curr);
 529                 /* Wake up any joining threads */
 530                 for (unsigned int i = 0;i < get_num_threads();i++) {
 531                         Thread *waiting = get_thread(int_to_id(i));
 532                         if (waiting->waiting_on() == th &&
 533                                         waiting->get_pending()->is_thread_join())
 534                                 scheduler->wake(waiting);
 535                 }
 536                 th->complete();
 537                 updated = true; /* trigger rel-seq checks */
 538                 break;
 539         }
 540         case THREAD_START: {
 541                 break;
 542         }
 543         default:
 544                 break;
 545         }
 546
 547         return updated;
 548 }
 549
 550 /**
 551  * Initialize the current action by performing one or more of the following
 552  * actions, as appropriate: merging RMWR and RMWC/RMW actions,
 553  * manipulating backtracking sets, allocating and
 554  * initializing clock vectors, and computing the promises to fulfill.
 555  *
 556  * @param curr The current action, as passed from the user context; may be
 557  * freed/invalidated after the execution of this function, with a different
 558  * action "returned" its place (pass-by-reference)
 559  * @return True if curr is a newly-explored action; false otherwise
 560  */
 561 bool ModelExecution::initialize_curr_action(ModelAction **curr)
 562 {
 563         if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
 564                 ModelAction *newcurr = process_rmw(*curr);
 565                 delete *curr;
 566
 567                 *curr = newcurr;
 568                 return false;
 569         } else {
 570                 ModelAction *newcurr = *curr;
 571
 572                 newcurr->set_seq_number(get_next_seq_num());
 573                 /* Always compute new clock vector */
 574                 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
 575
 576                 /* Assign most recent release fence */
 577                 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
 578
 579                 return true;    /* This was a new ModelAction */
 580         }
 581 }
 582
 583 /**
 584  * @brief Establish reads-from relation between two actions
 585  *
 586  * Perform basic operations involved with establishing a concrete rf relation,
 587  * including setting the ModelAction data and checking for release sequences.
 588  *
 589  * @param act The action that is reading (must be a read)
 590  * @param rf The action from which we are reading (must be a write)
 591  *
 592  * @return True if this read established synchronization
 593  */
 594
 595 void ModelExecution::read_from(ModelAction *act, ModelAction *rf)
 596 {
 597         ASSERT(rf);
 598         ASSERT(rf->is_write());
 599
 600         act->set_read_from(rf);
 601         if (act->is_acquire()) {
 602                 ClockVector *cv = get_hb_from_write(rf);
 603                 if (cv == NULL)
 604                         return;
 605                 act->get_cv()->merge(cv);
 606         }
 607 }
 608
 609 /**
 610  * @brief Synchronizes two actions
 611  *
 612  * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
 613  * This function performs the synchronization as well as providing other hooks
 614  * for other checks along with synchronization.
 615  *
 616  * @param first The left-hand side of the synchronizes-with relation
 617  * @param second The right-hand side of the synchronizes-with relation
 618  * @return True if the synchronization was successful (i.e., was consistent
 619  * with the execution order); false otherwise
 620  */
 621 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
 622 {
 623         if (*second < *first) {
 624                 set_bad_synchronization();
 625                 return false;
 626         }
 627         return second->synchronize_with(first);
 628 }
 629
 630 /**
 631  * @brief Check whether a model action is enabled.
 632  *
 633  * Checks whether an operation would be successful (i.e., is a lock already
 634  * locked, or is the joined thread already complete).
 635  *
 636  * For yield-blocking, yields are never enabled.
 637  *
 638  * @param curr is the ModelAction to check whether it is enabled.
 639  * @return a bool that indicates whether the action is enabled.
 640  */
 641 bool ModelExecution::check_action_enabled(ModelAction *curr) {
 642         if (curr->is_lock()) {
 643                 cdsc::mutex *lock = curr->get_mutex();
 644                 struct cdsc::mutex_state *state = lock->get_state();
 645                 if (state->locked)
 646                         return false;
 647         } else if (curr->is_thread_join()) {
 648                 Thread *blocking = curr->get_thread_operand();
 649                 if (!blocking->is_complete()) {
 650                         return false;
 651                 }
 652         }
 653
 654         return true;
 655 }
 656
 657 /**
 658  * This is the heart of the model checker routine. It performs model-checking
 659  * actions corresponding to a given "current action." Among other processes, it
 660  * calculates reads-from relationships, updates synchronization clock vectors,
 661  * forms a memory_order constraints graph, and handles replay/backtrack
 662  * execution when running permutations of previously-observed executions.
 663  *
 664  * @param curr The current action to process
 665  * @return The ModelAction that is actually executed; may be different than
 666  * curr
 667  */
 668 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
 669 {
 670         ASSERT(curr);
 671         bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
 672         bool newly_explored = initialize_curr_action(&curr);
 673
 674         DBG();
 675
 676         wake_up_sleeping_actions(curr);
 677
 678         /* Add the action to lists before any other model-checking tasks */
 679         if (!second_part_of_rmw && curr->get_type() != NOOP)
 680                 add_action_to_lists(curr);
 681
 682         if (curr->is_write())
 683                 add_write_to_lists(curr);
 684
 685         SnapVector<ModelAction *> * rf_set = NULL;
 686         /* Build may_read_from set for newly-created actions */
 687         if (newly_explored && curr->is_read())
 688                 rf_set = build_may_read_from(curr);
 689
 690         process_thread_action(curr);
 691
 692         if (curr->is_read() && !second_part_of_rmw) {
 693                 process_read(curr, rf_set);
 694                 delete rf_set;
 695         } else {
 696                 ASSERT(rf_set == NULL);
 697         }
 698
 699         if (curr->is_write())
 700                 process_write(curr);
 701
 702         if (curr->is_fence())
 703                 process_fence(curr);
 704
 705         if (curr->is_mutex_op())
 706                 process_mutex(curr);
 707
 708         return curr;
 709 }
 710
 711 /**
 712  * This is the strongest feasibility check available.
 713  * @return whether the current trace (partial or complete) must be a prefix of
 714  * a feasible trace.
 715  */
 716 bool ModelExecution::isfeasibleprefix() const
 717 {
 718         return !is_infeasible();
 719 }
 720
 721 /**
 722  * Print disagnostic information about an infeasible execution
 723  * @param prefix A string to prefix the output with; if NULL, then a default
 724  * message prefix will be provided
 725  */
 726 void ModelExecution::print_infeasibility(const char *prefix) const
 727 {
 728         char buf[100];
 729         char *ptr = buf;
 730         if (priv->bad_synchronization)
 731                 ptr += sprintf(ptr, "[bad sw ordering]");
 732         if (ptr != buf)
 733                 model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
 734 }
 735
 736 /**
 737  * Check if the current partial trace is infeasible. Does not check any
 738  * end-of-execution flags, which might rule out the execution. Thus, this is
 739  * useful only for ruling an execution as infeasible.
 740  * @return whether the current partial trace is infeasible.
 741  */
 742 bool ModelExecution::is_infeasible() const
 743 {
 744         return priv->bad_synchronization;
 745 }
 746
 747 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
 748 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
 749         ModelAction *lastread = get_last_action(act->get_tid());
 750         lastread->process_rmw(act);
 751         if (act->is_rmw()) {
 752                 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
 753         }
 754         return lastread;
 755 }
 756
 757 /**
 758  * @brief Updates the mo_graph with the constraints imposed from the current
 759  * read.
 760  *
 761  * Basic idea is the following: Go through each other thread and find
 762  * the last action that happened before our read.  Two cases:
 763  *
 764  * -# The action is a write: that write must either occur before
 765  * the write we read from or be the write we read from.
 766  * -# The action is a read: the write that that action read from
 767  * must occur before the write we read from or be the same write.
 768  *
 769  * @param curr The current action. Must be a read.
 770  * @param rf The ModelAction or Promise that curr reads from. Must be a write.
 771  * @return True if modification order edges were added; false otherwise
 772  */
 773
 774 bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf, SnapVector<const ModelAction *> * priorset, bool * canprune)
 775 {
 776         SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
 777         unsigned int i;
 778         ASSERT(curr->is_read());
 779
 780         /* Last SC fence in the current thread */
 781         ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
 782
 783         int tid = curr->get_tid();
 784         ModelAction *prev_same_thread = NULL;
 785         /* Iterate over all threads */
 786         for (i = 0;i < thrd_lists->size();i++, tid = (((unsigned int)(tid+1)) == thrd_lists->size()) ? 0 : tid + 1) {
 787                 /* Last SC fence in thread tid */
 788                 ModelAction *last_sc_fence_thread_local = NULL;
 789                 if (i != 0)
 790                         last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(tid), NULL);
 791
 792                 /* Last SC fence in thread tid, before last SC fence in current thread */
 793                 ModelAction *last_sc_fence_thread_before = NULL;
 794                 if (last_sc_fence_local)
 795                         last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(tid), last_sc_fence_local);
 796
 797                 //Only need to iterate if either hb has changed for thread in question or SC fence after last operation...
 798                 if (prev_same_thread != NULL &&
 799                                 (prev_same_thread->get_cv()->getClock(tid) == curr->get_cv()->getClock(tid)) &&
 800                                 (last_sc_fence_thread_local == NULL || *last_sc_fence_thread_local < *prev_same_thread)) {
 801                         continue;
 802                 }
 803
 804                 /* Iterate over actions in thread, starting from most recent */
 805                 action_list_t *list = &(*thrd_lists)[tid];
 806                 action_list_t::reverse_iterator rit;
 807                 for (rit = list->rbegin();rit != list->rend();rit++) {
 808                         ModelAction *act = *rit;
 809
 810                         /* Skip curr */
 811                         if (act == curr)
 812                                 continue;
 813                         /* Don't want to add reflexive edges on 'rf' */
 814                         if (act->equals(rf)) {
 815                                 if (act->happens_before(curr))
 816                                         break;
 817                                 else
 818                                         continue;
 819                         }
 820
 821                         if (act->is_write()) {
 822                                 /* C++, Section 29.3 statement 5 */
 823                                 if (curr->is_seqcst() && last_sc_fence_thread_local &&
 824                                                 *act < *last_sc_fence_thread_local) {
 825                                         if (mo_graph->checkReachable(rf, act))
 826                                                 return false;
 827                                         priorset->push_back(act);
 828                                         break;
 829                                 }
 830                                 /* C++, Section 29.3 statement 4 */
 831                                 else if (act->is_seqcst() && last_sc_fence_local &&
 832                                                                  *act < *last_sc_fence_local) {
 833                                         if (mo_graph->checkReachable(rf, act))
 834                                                 return false;
 835                                         priorset->push_back(act);
 836                                         break;
 837                                 }
 838                                 /* C++, Section 29.3 statement 6 */
 839                                 else if (last_sc_fence_thread_before &&
 840                                                                  *act < *last_sc_fence_thread_before) {
 841                                         if (mo_graph->checkReachable(rf, act))
 842                                                 return false;
 843                                         priorset->push_back(act);
 844                                         break;
 845                                 }
 846                         }
 847
 848                         /*
 849                          * Include at most one act per-thread that "happens
 850                          * before" curr
 851                          */
 852                         if (act->happens_before(curr)) {
 853                                 if (i==0) {
 854                                         if (last_sc_fence_local == NULL ||
 855                                                         (*last_sc_fence_local < *prev_same_thread)) {
 856                                                 prev_same_thread = act;
 857                                         }
 858                                 }
 859                                 if (act->is_write()) {
 860                                         if (mo_graph->checkReachable(rf, act))
 861                                                 return false;
 862                                         priorset->push_back(act);
 863                                 } else {
 864                                         const ModelAction *prevrf = act->get_reads_from();
 865                                         if (!prevrf->equals(rf)) {
 866                                                 if (mo_graph->checkReachable(rf, prevrf))
 867                                                         return false;
 868                                                 priorset->push_back(prevrf);
 869                                         } else {
 870                                                 if (act->get_tid() == curr->get_tid()) {
 871                                                         //Can prune curr from obj list
 872                                                         *canprune = true;
 873                                                 }
 874                                         }
 875                                 }
 876                                 break;
 877                         }
 878                 }
 879         }
 880         return true;
 881 }
 882
 883 /**
 884  * Updates the mo_graph with the constraints imposed from the current write.
 885  *
 886  * Basic idea is the following: Go through each other thread and find
 887  * the lastest action that happened before our write.  Two cases:
 888  *
 889  * (1) The action is a write => that write must occur before
 890  * the current write
 891  *
 892  * (2) The action is a read => the write that that action read from
 893  * must occur before the current write.
 894  *
 895  * This method also handles two other issues:
 896  *
 897  * (I) Sequential Consistency: Making sure that if the current write is
 898  * seq_cst, that it occurs after the previous seq_cst write.
 899  *
 900  * (II) Sending the write back to non-synchronizing reads.
 901  *
 902  * @param curr The current action. Must be a write.
 903  * @param send_fv A vector for stashing reads to which we may pass our future
 904  * value. If NULL, then don't record any future values.
 905  * @return True if modification order edges were added; false otherwise
 906  */
 907 void ModelExecution::w_modification_order(ModelAction *curr)
 908 {
 909         SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
 910         unsigned int i;
 911         ASSERT(curr->is_write());
 912
 913         if (curr->is_seqcst()) {
 914                 /* We have to at least see the last sequentially consistent write,
 915                          so we are initialized. */
 916                 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
 917                 if (last_seq_cst != NULL) {
 918                         mo_graph->addEdge(last_seq_cst, curr);
 919                 }
 920         }
 921
 922         /* Last SC fence in the current thread */
 923         ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
 924
 925         /* Iterate over all threads */
 926         for (i = 0;i < thrd_lists->size();i++) {
 927                 /* Last SC fence in thread i, before last SC fence in current thread */
 928                 ModelAction *last_sc_fence_thread_before = NULL;
 929                 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
 930                         last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
 931
 932                 /* Iterate over actions in thread, starting from most recent */
 933                 action_list_t *list = &(*thrd_lists)[i];
 934                 action_list_t::reverse_iterator rit;
 935                 bool force_edge = false;
 936                 for (rit = list->rbegin();rit != list->rend();rit++) {
 937                         ModelAction *act = *rit;
 938                         if (act == curr) {
 939                                 /*
 940                                  * 1) If RMW and it actually read from something, then we
 941                                  * already have all relevant edges, so just skip to next
 942                                  * thread.
 943                                  *
 944                                  * 2) If RMW and it didn't read from anything, we should
 945                                  * whatever edge we can get to speed up convergence.
 946                                  *
 947                                  * 3) If normal write, we need to look at earlier actions, so
 948                                  * continue processing list.
 949                                  */
 950                                 force_edge = true;
 951                                 if (curr->is_rmw()) {
 952                                         if (curr->get_reads_from() != NULL)
 953                                                 break;
 954                                         else
 955                                                 continue;
 956                                 } else
 957                                         continue;
 958                         }
 959
 960                         /* C++, Section 29.3 statement 7 */
 961                         if (last_sc_fence_thread_before && act->is_write() &&
 962                                         *act < *last_sc_fence_thread_before) {
 963                                 mo_graph->addEdge(act, curr, force_edge);
 964                                 break;
 965                         }
 966
 967                         /*
 968                          * Include at most one act per-thread that "happens
 969                          * before" curr
 970                          */
 971                         if (act->happens_before(curr)) {
 972                                 /*
 973                                  * Note: if act is RMW, just add edge:
 974                                  *   act --mo--> curr
 975                                  * The following edge should be handled elsewhere:
 976                                  *   readfrom(act) --mo--> act
 977                                  */
 978                                 if (act->is_write())
 979                                         mo_graph->addEdge(act, curr, force_edge);
 980                                 else if (act->is_read()) {
 981                                         //if previous read accessed a null, just keep going
 982                                         mo_graph->addEdge(act->get_reads_from(), curr, force_edge);
 983                                 }
 984                                 break;
 985                         }
 986                 }
 987         }
 988 }
 989
 990 /**
 991  * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
 992  * some constraints. This method checks one the following constraint (others
 993  * require compiler support):
 994  *
 995  *   If X --hb-> Y --mo-> Z, then X should not read from Z.
 996  *   If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
 997  */
 998 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
 999 {
1000         SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1001         unsigned int i;
1002         /* Iterate over all threads */
1003         for (i = 0;i < thrd_lists->size();i++) {
1004                 const ModelAction *write_after_read = NULL;
1005
1006                 /* Iterate over actions in thread, starting from most recent */
1007                 action_list_t *list = &(*thrd_lists)[i];
1008                 action_list_t::reverse_iterator rit;
1009                 for (rit = list->rbegin();rit != list->rend();rit++) {
1010                         ModelAction *act = *rit;
1011
1012                         /* Don't disallow due to act == reader */
1013                         if (!reader->happens_before(act) || reader == act)
1014                                 break;
1015                         else if (act->is_write())
1016                                 write_after_read = act;
1017                         else if (act->is_read() && act->get_reads_from() != NULL)
1018                                 write_after_read = act->get_reads_from();
1019                 }
1020
1021                 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1022                         return false;
1023         }
1024         return true;
1025 }
1026
1027 /**
1028  * Computes the clock vector that happens before propagates from this write.
1029  *
1030  * @param rf The action that might be part of a release sequence. Must be a
1031  * write.
1032  * @return ClockVector of happens before relation.
1033  */
1034
1035 ClockVector * ModelExecution::get_hb_from_write(ModelAction *rf) const {
1036         SnapVector<ModelAction *> * processset = NULL;
1037         for ( ;rf != NULL;rf = rf->get_reads_from()) {
1038                 ASSERT(rf->is_write());
1039                 if (!rf->is_rmw() || (rf->is_acquire() && rf->is_release()) || rf->get_rfcv() != NULL)
1040                         break;
1041                 if (processset == NULL)
1042                         processset = new SnapVector<ModelAction *>();
1043                 processset->push_back(rf);
1044         }
1045
1046         int i = (processset == NULL) ? 0 : processset->size();
1047
1048         ClockVector * vec = NULL;
1049         while(true) {
1050                 if (rf->get_rfcv() != NULL) {
1051                         vec = rf->get_rfcv();
1052                 } else if (rf->is_acquire() && rf->is_release()) {
1053                         vec = rf->get_cv();
1054                 } else if (rf->is_release() && !rf->is_rmw()) {
1055                         vec = rf->get_cv();
1056                 } else if (rf->is_release()) {
1057                         //have rmw that is release and doesn't have a rfcv
1058                         (vec = new ClockVector(vec, NULL))->merge(rf->get_cv());
1059                         rf->set_rfcv(vec);
1060                 } else {
1061                         //operation that isn't release
1062                         if (rf->get_last_fence_release()) {
1063                                 if (vec == NULL)
1064                                         vec = rf->get_last_fence_release()->get_cv();
1065                                 else
1066                                         (vec=new ClockVector(vec, NULL))->merge(rf->get_last_fence_release()->get_cv());
1067                         }
1068                         rf->set_rfcv(vec);
1069                 }
1070                 i--;
1071                 if (i >= 0) {
1072                         rf = (*processset)[i];
1073                 } else
1074                         break;
1075         }
1076         if (processset != NULL)
1077                 delete processset;
1078         return vec;
1079 }
1080
1081 /**
1082  * Performs various bookkeeping operations for the current ModelAction. For
1083  * instance, adds action to the per-object, per-thread action vector and to the
1084  * action trace list of all thread actions.
1085  *
1086  * @param act is the ModelAction to add.
1087  */
1088 void ModelExecution::add_action_to_lists(ModelAction *act)
1089 {
1090         int tid = id_to_int(act->get_tid());
1091         ModelAction *uninit = NULL;
1092         int uninit_id = -1;
1093         action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1094         if (list->empty() && act->is_atomic_var()) {
1095                 uninit = get_uninitialized_action(act);
1096                 uninit_id = id_to_int(uninit->get_tid());
1097                 list->push_front(uninit);
1098                 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, act->get_location());
1099                 if (uninit_id >= (int)vec->size())
1100                         vec->resize(uninit_id + 1);
1101                 (*vec)[uninit_id].push_front(uninit);
1102         }
1103         list->push_back(act);
1104
1105         // Update action trace, a total order of all actions
1106         action_trace.push_back(act);
1107         if (uninit)
1108                 action_trace.push_front(uninit);
1109
1110         // Update obj_thrd_map, a per location, per thread, order of actions
1111         SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1112         if (tid >= (int)vec->size())
1113                 vec->resize(priv->next_thread_id);
1114         (*vec)[tid].push_back(act);
1115         if (uninit)
1116                 (*vec)[uninit_id].push_front(uninit);
1117
1118         // Update thrd_last_action, the last action taken by each thrad
1119         if ((int)thrd_last_action.size() <= tid)
1120                 thrd_last_action.resize(get_num_threads());
1121         thrd_last_action[tid] = act;
1122         if (uninit)
1123                 thrd_last_action[uninit_id] = uninit;
1124
1125         // Update thrd_last_fence_release, the last release fence taken by each thread
1126         if (act->is_fence() && act->is_release()) {
1127                 if ((int)thrd_last_fence_release.size() <= tid)
1128                         thrd_last_fence_release.resize(get_num_threads());
1129                 thrd_last_fence_release[tid] = act;
1130         }
1131
1132         if (act->is_wait()) {
1133                 void *mutex_loc = (void *) act->get_value();
1134                 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
1135
1136                 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
1137                 if (tid >= (int)vec->size())
1138                         vec->resize(priv->next_thread_id);
1139                 (*vec)[tid].push_back(act);
1140         }
1141 }
1142
1143 void insertIntoActionList(action_list_t *list, ModelAction *act) {
1144         action_list_t::reverse_iterator rit = list->rbegin();
1145         modelclock_t next_seq = act->get_seq_number();
1146         if (rit == list->rend() || (*rit)->get_seq_number() == next_seq)
1147                 list->push_back(act);
1148         else {
1149                 for(;rit != list->rend();rit++) {
1150                         if ((*rit)->get_seq_number() == next_seq) {
1151                                 action_list_t::iterator it = rit.base();
1152                                 list->insert(it, act);
1153                                 break;
1154                         }
1155                 }
1156         }
1157 }
1158
1159 void insertIntoActionListAndSetCV(action_list_t *list, ModelAction *act) {
1160         action_list_t::reverse_iterator rit = list->rbegin();
1161         modelclock_t next_seq = act->get_seq_number();
1162         if (rit == list->rend()) {
1163                 act->create_cv(NULL);
1164         } else if ((*rit)->get_seq_number() == next_seq) {
1165                 act->create_cv((*rit));
1166                 list->push_back(act);
1167         } else {
1168                 for(;rit != list->rend();rit++) {
1169                         if ((*rit)->get_seq_number() == next_seq) {
1170                                 act->create_cv((*rit));
1171                                 action_list_t::iterator it = rit.base();
1172                                 list->insert(it, act);
1173                                 break;
1174                         }
1175                 }
1176         }
1177 }
1178
1179 /**
1180  * Performs various bookkeeping operations for a normal write.  The
1181  * complication is that we are typically inserting a normal write
1182  * lazily, so we need to insert it into the middle of lists.
1183  *
1184  * @param act is the ModelAction to add.
1185  */
1186
1187 void ModelExecution::add_normal_write_to_lists(ModelAction *act)
1188 {
1189         int tid = id_to_int(act->get_tid());
1190         insertIntoActionListAndSetCV(&action_trace, act);
1191
1192         action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1193         insertIntoActionList(list, act);
1194
1195         // Update obj_thrd_map, a per location, per thread, order of actions
1196         SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1197         if (tid >= (int)vec->size())
1198                 vec->resize(priv->next_thread_id);
1199         insertIntoActionList(&(*vec)[tid],act);
1200
1201         // Update thrd_last_action, the last action taken by each thrad
1202         if (thrd_last_action[tid]->get_seq_number() == act->get_seq_number())
1203                 thrd_last_action[tid] = act;
1204 }
1205
1206
1207 void ModelExecution::add_write_to_lists(ModelAction *write) {
1208         // Update seq_cst map
1209         if (write->is_seqcst())
1210                 obj_last_sc_map.put(write->get_location(), write);
1211
1212         SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, write->get_location());
1213         int tid = id_to_int(write->get_tid());
1214         if (tid >= (int)vec->size())
1215                 vec->resize(priv->next_thread_id);
1216         (*vec)[tid].push_back(write);
1217 }
1218
1219 /**
1220  * @brief Get the last action performed by a particular Thread
1221  * @param tid The thread ID of the Thread in question
1222  * @return The last action in the thread
1223  */
1224 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
1225 {
1226         int threadid = id_to_int(tid);
1227         if (threadid < (int)thrd_last_action.size())
1228                 return thrd_last_action[id_to_int(tid)];
1229         else
1230                 return NULL;
1231 }
1232
1233 /**
1234  * @brief Get the last fence release performed by a particular Thread
1235  * @param tid The thread ID of the Thread in question
1236  * @return The last fence release in the thread, if one exists; NULL otherwise
1237  */
1238 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
1239 {
1240         int threadid = id_to_int(tid);
1241         if (threadid < (int)thrd_last_fence_release.size())
1242                 return thrd_last_fence_release[id_to_int(tid)];
1243         else
1244                 return NULL;
1245 }
1246
1247 /**
1248  * Gets the last memory_order_seq_cst write (in the total global sequence)
1249  * performed on a particular object (i.e., memory location), not including the
1250  * current action.
1251  * @param curr The current ModelAction; also denotes the object location to
1252  * check
1253  * @return The last seq_cst write
1254  */
1255 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
1256 {
1257         void *location = curr->get_location();
1258         return obj_last_sc_map.get(location);
1259 }
1260
1261 /**
1262  * Gets the last memory_order_seq_cst fence (in the total global sequence)
1263  * performed in a particular thread, prior to a particular fence.
1264  * @param tid The ID of the thread to check
1265  * @param before_fence The fence from which to begin the search; if NULL, then
1266  * search for the most recent fence in the thread.
1267  * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
1268  */
1269 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
1270 {
1271         /* All fences should have location FENCE_LOCATION */
1272         action_list_t *list = obj_map.get(FENCE_LOCATION);
1273
1274         if (!list)
1275                 return NULL;
1276
1277         action_list_t::reverse_iterator rit = list->rbegin();
1278
1279         if (before_fence) {
1280                 for (;rit != list->rend();rit++)
1281                         if (*rit == before_fence)
1282                                 break;
1283
1284                 ASSERT(*rit == before_fence);
1285                 rit++;
1286         }
1287
1288         for (;rit != list->rend();rit++)
1289                 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
1290                         return *rit;
1291         return NULL;
1292 }
1293
1294 /**
1295  * Gets the last unlock operation performed on a particular mutex (i.e., memory
1296  * location). This function identifies the mutex according to the current
1297  * action, which is presumed to perform on the same mutex.
1298  * @param curr The current ModelAction; also denotes the object location to
1299  * check
1300  * @return The last unlock operation
1301  */
1302 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
1303 {
1304         void *location = curr->get_location();
1305
1306         action_list_t *list = obj_map.get(location);
1307         /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1308         action_list_t::reverse_iterator rit;
1309         for (rit = list->rbegin();rit != list->rend();rit++)
1310                 if ((*rit)->is_unlock() || (*rit)->is_wait())
1311                         return *rit;
1312         return NULL;
1313 }
1314
1315 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
1316 {
1317         ModelAction *parent = get_last_action(tid);
1318         if (!parent)
1319                 parent = get_thread(tid)->get_creation();
1320         return parent;
1321 }
1322
1323 /**
1324  * Returns the clock vector for a given thread.
1325  * @param tid The thread whose clock vector we want
1326  * @return Desired clock vector
1327  */
1328 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
1329 {
1330         ModelAction *firstaction=get_parent_action(tid);
1331         return firstaction != NULL ? firstaction->get_cv() : NULL;
1332 }
1333
1334 bool valequals(uint64_t val1, uint64_t val2, int size) {
1335         switch(size) {
1336         case 1:
1337                 return ((uint8_t)val1) == ((uint8_t)val2);
1338         case 2:
1339                 return ((uint16_t)val1) == ((uint16_t)val2);
1340         case 4:
1341                 return ((uint32_t)val1) == ((uint32_t)val2);
1342         case 8:
1343                 return val1==val2;
1344         default:
1345                 ASSERT(0);
1346                 return false;
1347         }
1348 }
1349
1350 /**
1351  * Build up an initial set of all past writes that this 'read' action may read
1352  * from, as well as any previously-observed future values that must still be valid.
1353  *
1354  * @param curr is the current ModelAction that we are exploring; it must be a
1355  * 'read' operation.
1356  */
1357 SnapVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *curr)
1358 {
1359         SnapVector<action_list_t> *thrd_lists = obj_wr_thrd_map.get(curr->get_location());
1360         unsigned int i;
1361         ASSERT(curr->is_read());
1362
1363         ModelAction *last_sc_write = NULL;
1364
1365         if (curr->is_seqcst())
1366                 last_sc_write = get_last_seq_cst_write(curr);
1367
1368         SnapVector<ModelAction *> * rf_set = new SnapVector<ModelAction *>();
1369
1370         /* Iterate over all threads */
1371         for (i = 0;i < thrd_lists->size();i++) {
1372                 /* Iterate over actions in thread, starting from most recent */
1373                 action_list_t *list = &(*thrd_lists)[i];
1374                 action_list_t::reverse_iterator rit;
1375                 for (rit = list->rbegin();rit != list->rend();rit++) {
1376                         ModelAction *act = *rit;
1377
1378                         if (act == curr)
1379                                 continue;
1380
1381                         /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1382                         bool allow_read = true;
1383
1384                         if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
1385                                 allow_read = false;
1386
1387                         /* Need to check whether we will have two RMW reading from the same value */
1388                         if (curr->is_rmwr()) {
1389                                 /* It is okay if we have a failing CAS */
1390                                 if (!curr->is_rmwrcas() ||
1391                                                 valequals(curr->get_value(), act->get_value(), curr->getSize())) {
1392                                         //Need to make sure we aren't the second RMW
1393                                         CycleNode * node = mo_graph->getNode_noCreate(act);
1394                                         if (node != NULL && node->getRMW() != NULL) {
1395                                                 //we are the second RMW
1396                                                 allow_read = false;
1397                                         }
1398                                 }
1399                         }
1400
1401                         if (allow_read) {
1402                                 /* Only add feasible reads */
1403                                 rf_set->push_back(act);
1404                         }
1405
1406                         /* Include at most one act per-thread that "happens before" curr */
1407                         if (act->happens_before(curr))
1408                                 break;
1409                 }
1410         }
1411
1412         if (DBG_ENABLED()) {
1413                 model_print("Reached read action:\n");
1414                 curr->print();
1415                 model_print("End printing read_from_past\n");
1416         }
1417         return rf_set;
1418 }
1419
1420 /**
1421  * @brief Get an action representing an uninitialized atomic
1422  *
1423  * This function may create a new one.
1424  *
1425  * @param curr The current action, which prompts the creation of an UNINIT action
1426  * @return A pointer to the UNINIT ModelAction
1427  */
1428 ModelAction * ModelExecution::get_uninitialized_action(ModelAction *curr) const
1429 {
1430         ModelAction *act = curr->get_uninit_action();
1431         if (!act) {
1432                 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
1433                 curr->set_uninit_action(act);
1434         }
1435         act->create_cv(NULL);
1436         return act;
1437 }
1438
1439 static void print_list(const action_list_t *list)
1440 {
1441         action_list_t::const_iterator it;
1442
1443         model_print("------------------------------------------------------------------------------------\n");
1444         model_print("#    t    Action type     MO       Location         Value               Rf  CV\n");
1445         model_print("------------------------------------------------------------------------------------\n");
1446
1447         unsigned int hash = 0;
1448
1449         for (it = list->begin();it != list->end();it++) {
1450                 const ModelAction *act = *it;
1451                 if (act->get_seq_number() > 0)
1452                         act->print();
1453                 hash = hash^(hash<<3)^((*it)->hash());
1454         }
1455         model_print("HASH %u\n", hash);
1456         model_print("------------------------------------------------------------------------------------\n");
1457 }
1458
1459 #if SUPPORT_MOD_ORDER_DUMP
1460 void ModelExecution::dumpGraph(char *filename) const
1461 {
1462         char buffer[200];
1463         sprintf(buffer, "%s.dot", filename);
1464         FILE *file = fopen(buffer, "w");
1465         fprintf(file, "digraph %s {\n", filename);
1466         mo_graph->dumpNodes(file);
1467         ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
1468
1469         for (action_list_t::const_iterator it = action_trace.begin();it != action_trace.end();it++) {
1470                 ModelAction *act = *it;
1471                 if (act->is_read()) {
1472                         mo_graph->dot_print_node(file, act);
1473                         mo_graph->dot_print_edge(file,
1474                                                                                                                          act->get_reads_from(),
1475                                                                                                                          act,
1476                                                                                                                          "label=\"rf\", color=red, weight=2");
1477                 }
1478                 if (thread_array[act->get_tid()]) {
1479                         mo_graph->dot_print_edge(file,
1480                                                                                                                          thread_array[id_to_int(act->get_tid())],
1481                                                                                                                          act,
1482                                                                                                                          "label=\"sb\", color=blue, weight=400");
1483                 }
1484
1485                 thread_array[act->get_tid()] = act;
1486         }
1487         fprintf(file, "}\n");
1488         model_free(thread_array);
1489         fclose(file);
1490 }
1491 #endif
1492
1493 /** @brief Prints an execution trace summary. */
1494 void ModelExecution::print_summary() const
1495 {
1496 #if SUPPORT_MOD_ORDER_DUMP
1497         char buffername[100];
1498         sprintf(buffername, "exec%04u", get_execution_number());
1499         mo_graph->dumpGraphToFile(buffername);
1500         sprintf(buffername, "graph%04u", get_execution_number());
1501         dumpGraph(buffername);
1502 #endif
1503
1504         model_print("Execution trace %d:", get_execution_number());
1505         if (isfeasibleprefix()) {
1506                 if (scheduler->all_threads_sleeping())
1507                         model_print(" SLEEP-SET REDUNDANT");
1508                 if (have_bug_reports())
1509                         model_print(" DETECTED BUG(S)");
1510         } else
1511                 print_infeasibility(" INFEASIBLE");
1512         model_print("\n");
1513
1514         print_list(&action_trace);
1515         model_print("\n");
1516
1517 }
1518
1519 /**
1520  * Add a Thread to the system for the first time. Should only be called once
1521  * per thread.
1522  * @param t The Thread to add
1523  */
1524 void ModelExecution::add_thread(Thread *t)
1525 {
1526         unsigned int i = id_to_int(t->get_id());
1527         if (i >= thread_map.size())
1528                 thread_map.resize(i + 1);
1529         thread_map[i] = t;
1530         if (!t->is_model_thread())
1531                 scheduler->add_thread(t);
1532 }
1533
1534 /**
1535  * @brief Get a Thread reference by its ID
1536  * @param tid The Thread's ID
1537  * @return A Thread reference
1538  */
1539 Thread * ModelExecution::get_thread(thread_id_t tid) const
1540 {
1541         unsigned int i = id_to_int(tid);
1542         if (i < thread_map.size())
1543                 return thread_map[i];
1544         return NULL;
1545 }
1546
1547 /**
1548  * @brief Get a reference to the Thread in which a ModelAction was executed
1549  * @param act The ModelAction
1550  * @return A Thread reference
1551  */
1552 Thread * ModelExecution::get_thread(const ModelAction *act) const
1553 {
1554         return get_thread(act->get_tid());
1555 }
1556
1557 /**
1558  * @brief Get a Thread reference by its pthread ID
1559  * @param index The pthread's ID
1560  * @return A Thread reference
1561  */
1562 Thread * ModelExecution::get_pthread(pthread_t pid) {
1563         union {
1564                 pthread_t p;
1565                 uint32_t v;
1566         } x;
1567         x.p = pid;
1568         uint32_t thread_id = x.v;
1569         if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
1570         else return NULL;
1571 }
1572
1573 /**
1574  * @brief Check if a Thread is currently enabled
1575  * @param t The Thread to check
1576  * @return True if the Thread is currently enabled
1577  */
1578 bool ModelExecution::is_enabled(Thread *t) const
1579 {
1580         return scheduler->is_enabled(t);
1581 }
1582
1583 /**
1584  * @brief Check if a Thread is currently enabled
1585  * @param tid The ID of the Thread to check
1586  * @return True if the Thread is currently enabled
1587  */
1588 bool ModelExecution::is_enabled(thread_id_t tid) const
1589 {
1590         return scheduler->is_enabled(tid);
1591 }
1592
1593 /**
1594  * @brief Select the next thread to execute based on the curren action
1595  *
1596  * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
1597  * actions should be followed by the execution of their child thread. In either
1598  * case, the current action should determine the next thread schedule.
1599  *
1600  * @param curr The current action
1601  * @return The next thread to run, if the current action will determine this
1602  * selection; otherwise NULL
1603  */
1604 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
1605 {
1606         /* Do not split atomic RMW */
1607         if (curr->is_rmwr())
1608                 return get_thread(curr);
1609         /* Follow CREATE with the created thread */
1610         /* which is not needed, because model.cc takes care of this */
1611         if (curr->get_type() == THREAD_CREATE)
1612                 return curr->get_thread_operand();
1613         if (curr->get_type() == PTHREAD_CREATE) {
1614                 return curr->get_thread_operand();
1615         }
1616         return NULL;
1617 }
1618
1619 /**
1620  * Takes the next step in the execution, if possible.
1621  * @param curr The current step to take
1622  * @return Returns the next Thread to run, if any; NULL if this execution
1623  * should terminate
1624  */
1625 Thread * ModelExecution::take_step(ModelAction *curr)
1626 {
1627         Thread *curr_thrd = get_thread(curr);
1628         ASSERT(curr_thrd->get_state() == THREAD_READY);
1629
1630         ASSERT(check_action_enabled(curr));     /* May have side effects? */
1631         curr = check_current_action(curr);
1632         ASSERT(curr);
1633
1634         /* Process this action in ModelHistory for records*/
1635         model->get_history()->process_action( curr, curr_thrd->get_id() );
1636
1637         if (curr_thrd->is_blocked() || curr_thrd->is_complete())
1638                 scheduler->remove_thread(curr_thrd);
1639
1640         return action_select_next_thread(curr);
1641 }
1642
1643 Fuzzer * ModelExecution::getFuzzer() {
1644         return fuzzer;
1645 }