11 #include "clockvector.h"
12 #include "cyclegraph.h"
14 #include "threads-model.h"
15 #include "bugmessage.h"
18 #include "newfuzzer.h"
20 #define INITIAL_THREAD_ID 0
23 * Structure for holding small ModelChecker members that should be snapshotted
25 struct model_snapshot_members {
26 model_snapshot_members() :
27 /* First thread created will have id INITIAL_THREAD_ID */
28 next_thread_id(INITIAL_THREAD_ID),
29 used_sequence_numbers(0),
34 ~model_snapshot_members() {
35 for (unsigned int i = 0;i < bugs.size();i++)
40 unsigned int next_thread_id;
41 modelclock_t used_sequence_numbers;
42 SnapVector<bug_message *> bugs;
43 /** @brief Incorrectly-ordered synchronization was made */
49 /** @brief Constructor */
50 ModelExecution::ModelExecution(ModelChecker *m, Scheduler *scheduler) :
54 thread_map(2), /* We'll always need at least 2 threads */
59 condvar_waiters_map(),
63 thrd_last_fence_release(),
64 priv(new struct model_snapshot_members ()),
65 mo_graph(new CycleGraph()),
66 fuzzer(new NewFuzzer()),
69 /* Initialize a model-checker thread, for special ModelActions */
70 model_thread = new Thread(get_next_id());
71 add_thread(model_thread);
72 fuzzer->register_engine(m->get_history(), this);
73 scheduler->register_engine(this);
75 pthread_key_create(&pthreadkey, tlsdestructor);
79 /** @brief Destructor */
80 ModelExecution::~ModelExecution()
82 for (unsigned int i = 0;i < get_num_threads();i++)
83 delete get_thread(int_to_id(i));
89 int ModelExecution::get_execution_number() const
91 return model->get_execution_number();
94 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 2> * hash, void * ptr)
96 action_list_t *tmp = hash->get(ptr);
98 tmp = new action_list_t();
104 static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<action_list_t> *, uintptr_t, 2> * hash, void * ptr)
106 SnapVector<action_list_t> *tmp = hash->get(ptr);
108 tmp = new SnapVector<action_list_t>();
114 /** @return a thread ID for a new Thread */
115 thread_id_t ModelExecution::get_next_id()
117 return priv->next_thread_id++;
120 /** @return the number of user threads created during this execution */
121 unsigned int ModelExecution::get_num_threads() const
123 return priv->next_thread_id;
126 /** @return a sequence number for a new ModelAction */
127 modelclock_t ModelExecution::get_next_seq_num()
129 return ++priv->used_sequence_numbers;
132 /** Restore the last used sequence number when actions of a thread are postponed by Fuzzer */
133 void ModelExecution::restore_last_seq_num()
135 priv->used_sequence_numbers--;
139 * @brief Should the current action wake up a given thread?
141 * @param curr The current action
142 * @param thread The thread that we might wake up
143 * @return True, if we should wake up the sleeping thread; false otherwise
145 bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
147 const ModelAction *asleep = thread->get_pending();
148 /* Don't allow partial RMW to wake anyone up */
151 /* Synchronizing actions may have been backtracked */
152 if (asleep->could_synchronize_with(curr))
154 /* All acquire/release fences and fence-acquire/store-release */
155 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
157 /* Fence-release + store can awake load-acquire on the same location */
158 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
159 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
160 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
163 /* The sleep is literally sleeping */
164 if (asleep->is_sleep()) {
165 if (fuzzer->shouldWake(asleep))
172 void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
174 for (unsigned int i = 0;i < get_num_threads();i++) {
175 Thread *thr = get_thread(int_to_id(i));
176 if (scheduler->is_sleep_set(thr)) {
177 if (should_wake_up(curr, thr)) {
178 /* Remove this thread from sleep set */
179 scheduler->remove_sleep(thr);
180 if (thr->get_pending()->is_sleep())
181 thr->set_wakeup_state(true);
187 void ModelExecution::assert_bug(const char *msg)
189 priv->bugs.push_back(new bug_message(msg));
193 /** @return True, if any bugs have been reported for this execution */
194 bool ModelExecution::have_bug_reports() const
196 return priv->bugs.size() != 0;
199 SnapVector<bug_message *> * ModelExecution::get_bugs() const
205 * Check whether the current trace has triggered an assertion which should halt
208 * @return True, if the execution should be aborted; false otherwise
210 bool ModelExecution::has_asserted() const
212 return priv->asserted;
216 * Trigger a trace assertion which should cause this execution to be halted.
217 * This can be due to a detected bug or due to an infeasibility that should
220 void ModelExecution::set_assert()
222 priv->asserted = true;
226 * Check if we are in a deadlock. Should only be called at the end of an
227 * execution, although it should not give false positives in the middle of an
228 * execution (there should be some ENABLED thread).
230 * @return True if program is in a deadlock; false otherwise
232 bool ModelExecution::is_deadlocked() const
234 bool blocking_threads = false;
235 for (unsigned int i = 0;i < get_num_threads();i++) {
236 thread_id_t tid = int_to_id(i);
239 Thread *t = get_thread(tid);
240 if (!t->is_model_thread() && t->get_pending())
241 blocking_threads = true;
243 return blocking_threads;
247 * Check if this is a complete execution. That is, have all thread completed
248 * execution (rather than exiting because sleep sets have forced a redundant
251 * @return True if the execution is complete.
253 bool ModelExecution::is_complete_execution() const
255 for (unsigned int i = 0;i < get_num_threads();i++)
256 if (is_enabled(int_to_id(i)))
261 ModelAction * ModelExecution::convertNonAtomicStore(void * location) {
262 uint64_t value = *((const uint64_t *) location);
263 modelclock_t storeclock;
264 thread_id_t storethread;
265 getStoreThreadAndClock(location, &storethread, &storeclock);
266 setAtomicStoreFlag(location);
267 ModelAction * act = new ModelAction(NONATOMIC_WRITE, memory_order_relaxed, location, value, get_thread(storethread));
268 act->set_seq_number(storeclock);
269 add_normal_write_to_lists(act);
270 add_write_to_lists(act);
271 w_modification_order(act);
272 model->get_history()->process_action(act, act->get_tid());
277 * Processes a read model action.
278 * @param curr is the read model action to process.
279 * @param rf_set is the set of model actions we can possibly read from
280 * @return True if processing this read updates the mo_graph.
282 bool ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> * rf_set)
284 SnapVector<const ModelAction *> * priorset = new SnapVector<const ModelAction *>();
285 bool hasnonatomicstore = hasNonAtomicStore(curr->get_location());
286 if (hasnonatomicstore) {
287 ModelAction * nonatomicstore = convertNonAtomicStore(curr->get_location());
288 rf_set->push_back(nonatomicstore);
291 // Remove writes that violate read modification order
294 while (i < rf_set->size()) {
295 ModelAction * rf = (*rf_set)[i];
296 if (!r_modification_order(curr, rf, NULL, NULL, true)) {
297 (*rf_set)[i] = rf_set->back();
304 int index = fuzzer->selectWrite(curr, rf_set);
306 ModelAction *rf = (*rf_set)[index];
309 bool canprune = false;
310 if (r_modification_order(curr, rf, priorset, &canprune)) {
311 for(unsigned int i=0;i<priorset->size();i++) {
312 mo_graph->addEdge((*priorset)[i], rf);
315 get_thread(curr)->set_return_value(curr->get_return_value());
317 if (canprune && curr->get_type() == ATOMIC_READ) {
318 int tid = id_to_int(curr->get_tid());
319 (*obj_thrd_map.get(curr->get_location()))[tid].pop_back();
324 (*rf_set)[index] = rf_set->back();
330 * Processes a lock, trylock, or unlock model action. @param curr is
331 * the read model action to process.
333 * The try lock operation checks whether the lock is taken. If not,
334 * it falls to the normal lock operation case. If so, it returns
337 * The lock operation has already been checked that it is enabled, so
338 * it just grabs the lock and synchronizes with the previous unlock.
340 * The unlock operation has to re-enable all of the threads that are
341 * waiting on the lock.
343 * @return True if synchronization was updated; false otherwise
345 bool ModelExecution::process_mutex(ModelAction *curr)
347 cdsc::mutex *mutex = curr->get_mutex();
348 struct cdsc::mutex_state *state = NULL;
351 state = mutex->get_state();
353 switch (curr->get_type()) {
354 case ATOMIC_TRYLOCK: {
355 bool success = !state->locked;
356 curr->set_try_lock(success);
358 get_thread(curr)->set_return_value(0);
361 get_thread(curr)->set_return_value(1);
363 //otherwise fall into the lock case
365 //TODO: FIND SOME BETTER WAY TO CHECK LOCK INITIALIZED OR NOT
366 //if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
367 // assert_bug("Lock access before initialization");
368 state->locked = get_thread(curr);
369 ModelAction *unlock = get_last_unlock(curr);
370 //synchronize with the previous unlock statement
371 if (unlock != NULL) {
372 synchronize(unlock, curr);
378 /* wake up the other threads */
379 for (unsigned int i = 0;i < get_num_threads();i++) {
380 Thread *t = get_thread(int_to_id(i));
381 Thread *curr_thrd = get_thread(curr);
382 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
386 /* unlock the lock - after checking who was waiting on it */
387 state->locked = NULL;
389 if (fuzzer->shouldWait(curr)) {
390 /* disable this thread */
391 get_safe_ptr_action(&condvar_waiters_map, curr->get_location())->push_back(curr);
392 scheduler->sleep(get_thread(curr));
397 case ATOMIC_TIMEDWAIT:
398 case ATOMIC_UNLOCK: {
399 //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...
401 /* wake up the other threads */
402 for (unsigned int i = 0;i < get_num_threads();i++) {
403 Thread *t = get_thread(int_to_id(i));
404 Thread *curr_thrd = get_thread(curr);
405 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
409 /* unlock the lock - after checking who was waiting on it */
410 state->locked = NULL;
413 case ATOMIC_NOTIFY_ALL: {
414 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
415 //activate all the waiting threads
416 for (sllnode<ModelAction *> * rit = waiters->begin();rit != NULL;rit=rit->getNext()) {
417 scheduler->wake(get_thread(rit->getVal()));
422 case ATOMIC_NOTIFY_ONE: {
423 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
424 if (waiters->size() != 0) {
425 Thread * thread = fuzzer->selectNotify(waiters);
426 scheduler->wake(thread);
438 * Process a write ModelAction
439 * @param curr The ModelAction to process
440 * @return True if the mo_graph was updated or promises were resolved
442 void ModelExecution::process_write(ModelAction *curr)
444 w_modification_order(curr);
445 get_thread(curr)->set_return_value(VALUE_NONE);
449 * Process a fence ModelAction
450 * @param curr The ModelAction to process
451 * @return True if synchronization was updated
453 bool ModelExecution::process_fence(ModelAction *curr)
456 * fence-relaxed: no-op
457 * fence-release: only log the occurence (not in this function), for
458 * use in later synchronization
459 * fence-acquire (this function): search for hypothetical release
461 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
463 bool updated = false;
464 if (curr->is_acquire()) {
465 action_list_t *list = &action_trace;
466 sllnode<ModelAction *> * rit;
467 /* Find X : is_read(X) && X --sb-> curr */
468 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
469 ModelAction *act = rit->getVal();
472 if (act->get_tid() != curr->get_tid())
474 /* Stop at the beginning of the thread */
475 if (act->is_thread_start())
477 /* Stop once we reach a prior fence-acquire */
478 if (act->is_fence() && act->is_acquire())
482 /* read-acquire will find its own release sequences */
483 if (act->is_acquire())
486 /* Establish hypothetical release sequences */
487 ClockVector *cv = get_hb_from_write(act->get_reads_from());
488 if (cv != NULL && curr->get_cv()->merge(cv))
496 * @brief Process the current action for thread-related activity
498 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
499 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
500 * synchronization, etc. This function is a no-op for non-THREAD actions
501 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
503 * @param curr The current action
504 * @return True if synchronization was updated or a thread completed
506 void ModelExecution::process_thread_action(ModelAction *curr)
508 switch (curr->get_type()) {
509 case THREAD_CREATE: {
510 thrd_t *thrd = (thrd_t *)curr->get_location();
511 struct thread_params *params = (struct thread_params *)curr->get_value();
512 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
513 curr->set_thread_operand(th);
515 th->set_creation(curr);
518 case PTHREAD_CREATE: {
519 (*(uint32_t *)curr->get_location()) = pthread_counter++;
521 struct pthread_params *params = (struct pthread_params *)curr->get_value();
522 Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
523 curr->set_thread_operand(th);
525 th->set_creation(curr);
527 if ( pthread_map.size() < pthread_counter )
528 pthread_map.resize( pthread_counter );
529 pthread_map[ pthread_counter-1 ] = th;
534 Thread *blocking = curr->get_thread_operand();
535 ModelAction *act = get_last_action(blocking->get_id());
536 synchronize(act, curr);
540 Thread *blocking = curr->get_thread_operand();
541 ModelAction *act = get_last_action(blocking->get_id());
542 synchronize(act, curr);
543 break; // WL: to be add (modified)
546 case THREADONLY_FINISH:
547 case THREAD_FINISH: {
548 Thread *th = get_thread(curr);
549 if (curr->get_type() == THREAD_FINISH &&
550 th == model->getInitThread()) {
556 /* Wake up any joining threads */
557 for (unsigned int i = 0;i < get_num_threads();i++) {
558 Thread *waiting = get_thread(int_to_id(i));
559 if (waiting->waiting_on() == th &&
560 waiting->get_pending()->is_thread_join())
561 scheduler->wake(waiting);
570 Thread *th = get_thread(curr);
571 th->set_pending(curr);
572 scheduler->add_sleep(th);
581 * Initialize the current action by performing one or more of the following
582 * actions, as appropriate: merging RMWR and RMWC/RMW actions,
583 * manipulating backtracking sets, allocating and
584 * initializing clock vectors, and computing the promises to fulfill.
586 * @param curr The current action, as passed from the user context; may be
587 * freed/invalidated after the execution of this function, with a different
588 * action "returned" its place (pass-by-reference)
589 * @return True if curr is a newly-explored action; false otherwise
591 bool ModelExecution::initialize_curr_action(ModelAction **curr)
593 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
594 ModelAction *newcurr = process_rmw(*curr);
600 ModelAction *newcurr = *curr;
602 newcurr->set_seq_number(get_next_seq_num());
603 /* Always compute new clock vector */
604 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
606 /* Assign most recent release fence */
607 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
609 return true; /* This was a new ModelAction */
614 * @brief Establish reads-from relation between two actions
616 * Perform basic operations involved with establishing a concrete rf relation,
617 * including setting the ModelAction data and checking for release sequences.
619 * @param act The action that is reading (must be a read)
620 * @param rf The action from which we are reading (must be a write)
622 * @return True if this read established synchronization
625 void ModelExecution::read_from(ModelAction *act, ModelAction *rf)
628 ASSERT(rf->is_write());
630 act->set_read_from(rf);
631 if (act->is_acquire()) {
632 ClockVector *cv = get_hb_from_write(rf);
635 act->get_cv()->merge(cv);
640 * @brief Synchronizes two actions
642 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
643 * This function performs the synchronization as well as providing other hooks
644 * for other checks along with synchronization.
646 * @param first The left-hand side of the synchronizes-with relation
647 * @param second The right-hand side of the synchronizes-with relation
648 * @return True if the synchronization was successful (i.e., was consistent
649 * with the execution order); false otherwise
651 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
653 if (*second < *first) {
654 ASSERT(0); //This should not happend
657 return second->synchronize_with(first);
661 * @brief Check whether a model action is enabled.
663 * Checks whether an operation would be successful (i.e., is a lock already
664 * locked, or is the joined thread already complete).
666 * For yield-blocking, yields are never enabled.
668 * @param curr is the ModelAction to check whether it is enabled.
669 * @return a bool that indicates whether the action is enabled.
671 bool ModelExecution::check_action_enabled(ModelAction *curr) {
672 if (curr->is_lock()) {
673 cdsc::mutex *lock = curr->get_mutex();
674 struct cdsc::mutex_state *state = lock->get_state();
677 } else if (curr->is_thread_join()) {
678 Thread *blocking = curr->get_thread_operand();
679 if (!blocking->is_complete()) {
682 } else if (curr->is_sleep()) {
683 if (!fuzzer->shouldSleep(curr))
691 * This is the heart of the model checker routine. It performs model-checking
692 * actions corresponding to a given "current action." Among other processes, it
693 * calculates reads-from relationships, updates synchronization clock vectors,
694 * forms a memory_order constraints graph, and handles replay/backtrack
695 * execution when running permutations of previously-observed executions.
697 * @param curr The current action to process
698 * @return The ModelAction that is actually executed; may be different than
701 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
704 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
705 bool newly_explored = initialize_curr_action(&curr);
709 wake_up_sleeping_actions(curr);
711 /* Add uninitialized actions to lists */
712 if (!second_part_of_rmw)
713 add_uninit_action_to_lists(curr);
715 SnapVector<ModelAction *> * rf_set = NULL;
716 /* Build may_read_from set for newly-created actions */
717 if (newly_explored && curr->is_read())
718 rf_set = build_may_read_from(curr);
720 if (curr->is_read() && !second_part_of_rmw) {
721 process_read(curr, rf_set);
724 ASSERT(rf_set == NULL);
726 /* Add the action to lists */
727 if (!second_part_of_rmw)
728 add_action_to_lists(curr);
730 if (curr->is_write())
731 add_write_to_lists(curr);
733 process_thread_action(curr);
735 if (curr->is_write())
738 if (curr->is_fence())
741 if (curr->is_mutex_op())
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);
752 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
758 * @brief Updates the mo_graph with the constraints imposed from the current
761 * Basic idea is the following: Go through each other thread and find
762 * the last action that happened before our read. Two cases:
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.
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 * @param check_only If true, then only check whether the current action satisfies
772 * read modification order or not, without modifiying priorset and canprune.
774 * @return True if modification order edges were added; false otherwise
777 bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf,
778 SnapVector<const ModelAction *> * priorset, bool * canprune, bool check_only)
780 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
782 ASSERT(curr->is_read());
784 /* Last SC fence in the current thread */
785 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
787 int tid = curr->get_tid();
788 ModelAction *prev_same_thread = NULL;
789 /* Iterate over all threads */
790 for (i = 0;i < thrd_lists->size();i++, tid = (((unsigned int)(tid+1)) == thrd_lists->size()) ? 0 : tid + 1) {
791 /* Last SC fence in thread tid */
792 ModelAction *last_sc_fence_thread_local = NULL;
794 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(tid), NULL);
796 /* Last SC fence in thread tid, before last SC fence in current thread */
797 ModelAction *last_sc_fence_thread_before = NULL;
798 if (last_sc_fence_local)
799 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(tid), last_sc_fence_local);
801 //Only need to iterate if either hb has changed for thread in question or SC fence after last operation...
802 if (prev_same_thread != NULL &&
803 (prev_same_thread->get_cv()->getClock(tid) == curr->get_cv()->getClock(tid)) &&
804 (last_sc_fence_thread_local == NULL || *last_sc_fence_thread_local < *prev_same_thread)) {
808 /* Iterate over actions in thread, starting from most recent */
809 action_list_t *list = &(*thrd_lists)[tid];
810 sllnode<ModelAction *> * rit;
811 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
812 ModelAction *act = rit->getVal();
817 /* Don't want to add reflexive edges on 'rf' */
818 if (act->equals(rf)) {
819 if (act->happens_before(curr))
825 if (act->is_write()) {
826 /* C++, Section 29.3 statement 5 */
827 if (curr->is_seqcst() && last_sc_fence_thread_local &&
828 *act < *last_sc_fence_thread_local) {
829 if (mo_graph->checkReachable(rf, act))
832 priorset->push_back(act);
835 /* C++, Section 29.3 statement 4 */
836 else if (act->is_seqcst() && last_sc_fence_local &&
837 *act < *last_sc_fence_local) {
838 if (mo_graph->checkReachable(rf, act))
841 priorset->push_back(act);
844 /* C++, Section 29.3 statement 6 */
845 else if (last_sc_fence_thread_before &&
846 *act < *last_sc_fence_thread_before) {
847 if (mo_graph->checkReachable(rf, act))
850 priorset->push_back(act);
856 * Include at most one act per-thread that "happens
859 if (act->happens_before(curr)) {
861 if (last_sc_fence_local == NULL ||
862 (*last_sc_fence_local < *act)) {
863 prev_same_thread = act;
866 if (act->is_write()) {
867 if (mo_graph->checkReachable(rf, act))
870 priorset->push_back(act);
872 const ModelAction *prevrf = act->get_reads_from();
873 if (!prevrf->equals(rf)) {
874 if (mo_graph->checkReachable(rf, prevrf))
877 priorset->push_back(prevrf);
879 if (act->get_tid() == curr->get_tid()) {
880 //Can prune curr from obj list
894 * Updates the mo_graph with the constraints imposed from the current write.
896 * Basic idea is the following: Go through each other thread and find
897 * the lastest action that happened before our write. Two cases:
899 * (1) The action is a write => that write must occur before
902 * (2) The action is a read => the write that that action read from
903 * must occur before the current write.
905 * This method also handles two other issues:
907 * (I) Sequential Consistency: Making sure that if the current write is
908 * seq_cst, that it occurs after the previous seq_cst write.
910 * (II) Sending the write back to non-synchronizing reads.
912 * @param curr The current action. Must be a write.
913 * @param send_fv A vector for stashing reads to which we may pass our future
914 * value. If NULL, then don't record any future values.
915 * @return True if modification order edges were added; false otherwise
917 void ModelExecution::w_modification_order(ModelAction *curr)
919 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
921 ASSERT(curr->is_write());
923 SnapList<ModelAction *> edgeset;
925 if (curr->is_seqcst()) {
926 /* We have to at least see the last sequentially consistent write,
927 so we are initialized. */
928 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
929 if (last_seq_cst != NULL) {
930 edgeset.push_back(last_seq_cst);
932 //update map for next query
933 obj_last_sc_map.put(curr->get_location(), curr);
936 /* Last SC fence in the current thread */
937 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
939 /* Iterate over all threads */
940 for (i = 0;i < thrd_lists->size();i++) {
941 /* Last SC fence in thread i, before last SC fence in current thread */
942 ModelAction *last_sc_fence_thread_before = NULL;
943 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
944 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
946 /* Iterate over actions in thread, starting from most recent */
947 action_list_t *list = &(*thrd_lists)[i];
948 sllnode<ModelAction*>* rit;
949 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
950 ModelAction *act = rit->getVal();
953 * 1) If RMW and it actually read from something, then we
954 * already have all relevant edges, so just skip to next
957 * 2) If RMW and it didn't read from anything, we should
958 * whatever edge we can get to speed up convergence.
960 * 3) If normal write, we need to look at earlier actions, so
961 * continue processing list.
963 if (curr->is_rmw()) {
964 if (curr->get_reads_from() != NULL)
972 /* C++, Section 29.3 statement 7 */
973 if (last_sc_fence_thread_before && act->is_write() &&
974 *act < *last_sc_fence_thread_before) {
975 edgeset.push_back(act);
980 * Include at most one act per-thread that "happens
983 if (act->happens_before(curr)) {
985 * Note: if act is RMW, just add edge:
987 * The following edge should be handled elsewhere:
988 * readfrom(act) --mo--> act
991 edgeset.push_back(act);
992 else if (act->is_read()) {
993 //if previous read accessed a null, just keep going
994 edgeset.push_back(act->get_reads_from());
1000 mo_graph->addEdges(&edgeset, curr);
1005 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1006 * some constraints. This method checks one the following constraint (others
1007 * require compiler support):
1009 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1010 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
1012 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1014 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1016 /* Iterate over all threads */
1017 for (i = 0;i < thrd_lists->size();i++) {
1018 const ModelAction *write_after_read = NULL;
1020 /* Iterate over actions in thread, starting from most recent */
1021 action_list_t *list = &(*thrd_lists)[i];
1022 sllnode<ModelAction *>* rit;
1023 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
1024 ModelAction *act = rit->getVal();
1026 /* Don't disallow due to act == reader */
1027 if (!reader->happens_before(act) || reader == act)
1029 else if (act->is_write())
1030 write_after_read = act;
1031 else if (act->is_read() && act->get_reads_from() != NULL)
1032 write_after_read = act->get_reads_from();
1035 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1042 * Computes the clock vector that happens before propagates from this write.
1044 * @param rf The action that might be part of a release sequence. Must be a
1046 * @return ClockVector of happens before relation.
1049 ClockVector * ModelExecution::get_hb_from_write(ModelAction *rf) const {
1050 SnapVector<ModelAction *> * processset = NULL;
1051 for ( ;rf != NULL;rf = rf->get_reads_from()) {
1052 ASSERT(rf->is_write());
1053 if (!rf->is_rmw() || (rf->is_acquire() && rf->is_release()) || rf->get_rfcv() != NULL)
1055 if (processset == NULL)
1056 processset = new SnapVector<ModelAction *>();
1057 processset->push_back(rf);
1060 int i = (processset == NULL) ? 0 : processset->size();
1062 ClockVector * vec = NULL;
1064 if (rf->get_rfcv() != NULL) {
1065 vec = rf->get_rfcv();
1066 } else if (rf->is_acquire() && rf->is_release()) {
1068 } else if (rf->is_release() && !rf->is_rmw()) {
1070 } else if (rf->is_release()) {
1071 //have rmw that is release and doesn't have a rfcv
1072 (vec = new ClockVector(vec, NULL))->merge(rf->get_cv());
1075 //operation that isn't release
1076 if (rf->get_last_fence_release()) {
1078 vec = rf->get_last_fence_release()->get_cv();
1080 (vec=new ClockVector(vec, NULL))->merge(rf->get_last_fence_release()->get_cv());
1086 rf = (*processset)[i];
1090 if (processset != NULL)
1096 * Performs various bookkeeping operations for the current ModelAction when it is
1097 * the first atomic action occurred at its memory location.
1099 * For instance, adds uninitialized action to the per-object, per-thread action vector
1100 * and to the action trace list of all thread actions.
1102 * @param act is the ModelAction to process.
1104 void ModelExecution::add_uninit_action_to_lists(ModelAction *act)
1106 int tid = id_to_int(act->get_tid());
1107 ModelAction *uninit = NULL;
1109 SnapVector<action_list_t> *objvec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1110 if (objvec->empty() && act->is_atomic_var()) {
1111 uninit = get_uninitialized_action(act);
1112 uninit_id = id_to_int(uninit->get_tid());
1113 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, act->get_location());
1114 if ((int)vec->size() <= uninit_id) {
1115 int oldsize = (int) vec->size();
1116 vec->resize(uninit_id + 1);
1117 for(int i = oldsize;i < uninit_id + 1;i++) {
1118 new (&(*vec)[i]) action_list_t();
1121 (*vec)[uninit_id].push_front(uninit);
1124 // Update action trace, a total order of all actions
1126 action_trace.push_front(uninit);
1128 // Update obj_thrd_map, a per location, per thread, order of actions
1129 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1130 if ((int)vec->size() <= tid) {
1131 uint oldsize = vec->size();
1132 vec->resize(priv->next_thread_id);
1133 for(uint i = oldsize;i < priv->next_thread_id;i++)
1134 new (&(*vec)[i]) action_list_t();
1137 (*vec)[uninit_id].push_front(uninit);
1139 // Update thrd_last_action, the last action taken by each thrad
1140 if ((int)thrd_last_action.size() <= tid)
1141 thrd_last_action.resize(get_num_threads());
1143 thrd_last_action[uninit_id] = uninit;
1148 * Performs various bookkeeping operations for the current ModelAction. For
1149 * instance, adds action to the per-object, per-thread action vector and to the
1150 * action trace list of all thread actions.
1152 * @param act is the ModelAction to add.
1154 void ModelExecution::add_action_to_lists(ModelAction *act)
1156 int tid = id_to_int(act->get_tid());
1157 if ((act->is_fence() && act->is_seqcst()) || act->is_unlock()) {
1158 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1159 list->push_back(act);
1162 // Update action trace, a total order of all actions
1163 action_trace.push_back(act);
1165 // Update obj_thrd_map, a per location, per thread, order of actions
1166 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1167 if ((int)vec->size() <= tid) {
1168 uint oldsize = vec->size();
1169 vec->resize(priv->next_thread_id);
1170 for(uint i = oldsize;i < priv->next_thread_id;i++)
1171 new (&(*vec)[i]) action_list_t();
1173 (*vec)[tid].push_back(act);
1175 // Update thrd_last_action, the last action taken by each thrad
1176 if ((int)thrd_last_action.size() <= tid)
1177 thrd_last_action.resize(get_num_threads());
1178 thrd_last_action[tid] = act;
1180 // Update thrd_last_fence_release, the last release fence taken by each thread
1181 if (act->is_fence() && act->is_release()) {
1182 if ((int)thrd_last_fence_release.size() <= tid)
1183 thrd_last_fence_release.resize(get_num_threads());
1184 thrd_last_fence_release[tid] = act;
1187 if (act->is_wait()) {
1188 void *mutex_loc = (void *) act->get_value();
1189 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
1191 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
1192 if ((int)vec->size() <= tid) {
1193 uint oldsize = vec->size();
1194 vec->resize(priv->next_thread_id);
1195 for(uint i = oldsize;i < priv->next_thread_id;i++)
1196 new (&(*vec)[i]) action_list_t();
1198 (*vec)[tid].push_back(act);
1202 void insertIntoActionList(action_list_t *list, ModelAction *act) {
1203 sllnode<ModelAction*> * rit = list->end();
1204 modelclock_t next_seq = act->get_seq_number();
1205 if (rit == NULL || (rit->getVal()->get_seq_number() == next_seq))
1206 list->push_back(act);
1208 for(;rit != NULL;rit=rit->getPrev()) {
1209 if (rit->getVal()->get_seq_number() == next_seq) {
1210 list->insertAfter(rit, act);
1217 void insertIntoActionListAndSetCV(action_list_t *list, ModelAction *act) {
1218 sllnode<ModelAction*> * rit = list->end();
1219 modelclock_t next_seq = act->get_seq_number();
1221 act->create_cv(NULL);
1222 } else if (rit->getVal()->get_seq_number() == next_seq) {
1223 act->create_cv(rit->getVal());
1224 list->push_back(act);
1226 for(;rit != NULL;rit=rit->getPrev()) {
1227 if (rit->getVal()->get_seq_number() == next_seq) {
1228 act->create_cv(rit->getVal());
1229 list->insertAfter(rit, act);
1237 * Performs various bookkeeping operations for a normal write. The
1238 * complication is that we are typically inserting a normal write
1239 * lazily, so we need to insert it into the middle of lists.
1241 * @param act is the ModelAction to add.
1244 void ModelExecution::add_normal_write_to_lists(ModelAction *act)
1246 int tid = id_to_int(act->get_tid());
1247 insertIntoActionListAndSetCV(&action_trace, act);
1249 // Update obj_thrd_map, a per location, per thread, order of actions
1250 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1251 if (tid >= (int)vec->size()) {
1252 uint oldsize =vec->size();
1253 vec->resize(priv->next_thread_id);
1254 for(uint i=oldsize;i<priv->next_thread_id;i++)
1255 new (&(*vec)[i]) action_list_t();
1257 insertIntoActionList(&(*vec)[tid],act);
1259 // Update thrd_last_action, the last action taken by each thrad
1260 if (thrd_last_action[tid]->get_seq_number() == act->get_seq_number())
1261 thrd_last_action[tid] = act;
1265 void ModelExecution::add_write_to_lists(ModelAction *write) {
1266 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, write->get_location());
1267 int tid = id_to_int(write->get_tid());
1268 if (tid >= (int)vec->size()) {
1269 uint oldsize =vec->size();
1270 vec->resize(priv->next_thread_id);
1271 for(uint i=oldsize;i<priv->next_thread_id;i++)
1272 new (&(*vec)[i]) action_list_t();
1274 (*vec)[tid].push_back(write);
1278 * @brief Get the last action performed by a particular Thread
1279 * @param tid The thread ID of the Thread in question
1280 * @return The last action in the thread
1282 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
1284 int threadid = id_to_int(tid);
1285 if (threadid < (int)thrd_last_action.size())
1286 return thrd_last_action[id_to_int(tid)];
1292 * @brief Get the last fence release performed by a particular Thread
1293 * @param tid The thread ID of the Thread in question
1294 * @return The last fence release in the thread, if one exists; NULL otherwise
1296 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
1298 int threadid = id_to_int(tid);
1299 if (threadid < (int)thrd_last_fence_release.size())
1300 return thrd_last_fence_release[id_to_int(tid)];
1306 * Gets the last memory_order_seq_cst write (in the total global sequence)
1307 * performed on a particular object (i.e., memory location), not including the
1309 * @param curr The current ModelAction; also denotes the object location to
1311 * @return The last seq_cst write
1313 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
1315 void *location = curr->get_location();
1316 return obj_last_sc_map.get(location);
1320 * Gets the last memory_order_seq_cst fence (in the total global sequence)
1321 * performed in a particular thread, prior to a particular fence.
1322 * @param tid The ID of the thread to check
1323 * @param before_fence The fence from which to begin the search; if NULL, then
1324 * search for the most recent fence in the thread.
1325 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
1327 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
1329 /* All fences should have location FENCE_LOCATION */
1330 action_list_t *list = obj_map.get(FENCE_LOCATION);
1335 sllnode<ModelAction*>* rit = list->end();
1338 for (;rit != NULL;rit=rit->getPrev())
1339 if (rit->getVal() == before_fence)
1342 ASSERT(rit->getVal() == before_fence);
1346 for (;rit != NULL;rit=rit->getPrev()) {
1347 ModelAction *act = rit->getVal();
1348 if (act->is_fence() && (tid == act->get_tid()) && act->is_seqcst())
1355 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1356 * location). This function identifies the mutex according to the current
1357 * action, which is presumed to perform on the same mutex.
1358 * @param curr The current ModelAction; also denotes the object location to
1360 * @return The last unlock operation
1362 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
1364 void *location = curr->get_location();
1366 action_list_t *list = obj_map.get(location);
1370 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1371 sllnode<ModelAction*>* rit;
1372 for (rit = list->end();rit != NULL;rit=rit->getPrev())
1373 if (rit->getVal()->is_unlock() || rit->getVal()->is_wait())
1374 return rit->getVal();
1378 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
1380 ModelAction *parent = get_last_action(tid);
1382 parent = get_thread(tid)->get_creation();
1387 * Returns the clock vector for a given thread.
1388 * @param tid The thread whose clock vector we want
1389 * @return Desired clock vector
1391 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
1393 ModelAction *firstaction=get_parent_action(tid);
1394 return firstaction != NULL ? firstaction->get_cv() : NULL;
1397 bool valequals(uint64_t val1, uint64_t val2, int size) {
1400 return ((uint8_t)val1) == ((uint8_t)val2);
1402 return ((uint16_t)val1) == ((uint16_t)val2);
1404 return ((uint32_t)val1) == ((uint32_t)val2);
1414 * Build up an initial set of all past writes that this 'read' action may read
1415 * from, as well as any previously-observed future values that must still be valid.
1417 * @param curr is the current ModelAction that we are exploring; it must be a
1420 SnapVector<ModelAction *> * ModelExecution::build_may_read_from(ModelAction *curr)
1422 SnapVector<action_list_t> *thrd_lists = obj_wr_thrd_map.get(curr->get_location());
1424 ASSERT(curr->is_read());
1426 ModelAction *last_sc_write = NULL;
1428 if (curr->is_seqcst())
1429 last_sc_write = get_last_seq_cst_write(curr);
1431 SnapVector<ModelAction *> * rf_set = new SnapVector<ModelAction *>();
1433 /* Iterate over all threads */
1434 for (i = 0;i < thrd_lists->size();i++) {
1435 /* Iterate over actions in thread, starting from most recent */
1436 action_list_t *list = &(*thrd_lists)[i];
1437 sllnode<ModelAction *> * rit;
1438 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
1439 ModelAction *act = rit->getVal();
1444 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1445 bool allow_read = true;
1447 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
1450 /* Need to check whether we will have two RMW reading from the same value */
1451 if (curr->is_rmwr()) {
1452 /* It is okay if we have a failing CAS */
1453 if (!curr->is_rmwrcas() ||
1454 valequals(curr->get_value(), act->get_value(), curr->getSize())) {
1455 //Need to make sure we aren't the second RMW
1456 CycleNode * node = mo_graph->getNode_noCreate(act);
1457 if (node != NULL && node->getRMW() != NULL) {
1458 //we are the second RMW
1465 /* Only add feasible reads */
1466 rf_set->push_back(act);
1469 /* Include at most one act per-thread that "happens before" curr */
1470 if (act->happens_before(curr))
1475 if (DBG_ENABLED()) {
1476 model_print("Reached read action:\n");
1478 model_print("End printing read_from_past\n");
1484 * @brief Get an action representing an uninitialized atomic
1486 * This function may create a new one.
1488 * @param curr The current action, which prompts the creation of an UNINIT action
1489 * @return A pointer to the UNINIT ModelAction
1491 ModelAction * ModelExecution::get_uninitialized_action(ModelAction *curr) const
1493 ModelAction *act = curr->get_uninit_action();
1495 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
1496 curr->set_uninit_action(act);
1498 act->create_cv(NULL);
1502 static void print_list(action_list_t *list)
1504 sllnode<ModelAction*> *it;
1506 model_print("------------------------------------------------------------------------------------\n");
1507 model_print("# t Action type MO Location Value Rf CV\n");
1508 model_print("------------------------------------------------------------------------------------\n");
1510 unsigned int hash = 0;
1512 for (it = list->begin();it != NULL;it=it->getNext()) {
1513 const ModelAction *act = it->getVal();
1514 if (act->get_seq_number() > 0)
1516 hash = hash^(hash<<3)^(it->getVal()->hash());
1518 model_print("HASH %u\n", hash);
1519 model_print("------------------------------------------------------------------------------------\n");
1522 #if SUPPORT_MOD_ORDER_DUMP
1523 void ModelExecution::dumpGraph(char *filename)
1526 sprintf(buffer, "%s.dot", filename);
1527 FILE *file = fopen(buffer, "w");
1528 fprintf(file, "digraph %s {\n", filename);
1529 mo_graph->dumpNodes(file);
1530 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
1532 for (sllnode<ModelAction*>* it = action_trace.begin();it != NULL;it=it->getNext()) {
1533 ModelAction *act = it->getVal();
1534 if (act->is_read()) {
1535 mo_graph->dot_print_node(file, act);
1536 mo_graph->dot_print_edge(file,
1537 act->get_reads_from(),
1539 "label=\"rf\", color=red, weight=2");
1541 if (thread_array[act->get_tid()]) {
1542 mo_graph->dot_print_edge(file,
1543 thread_array[id_to_int(act->get_tid())],
1545 "label=\"sb\", color=blue, weight=400");
1548 thread_array[act->get_tid()] = act;
1550 fprintf(file, "}\n");
1551 model_free(thread_array);
1556 /** @brief Prints an execution trace summary. */
1557 void ModelExecution::print_summary()
1559 #if SUPPORT_MOD_ORDER_DUMP
1560 char buffername[100];
1561 sprintf(buffername, "exec%04u", get_execution_number());
1562 mo_graph->dumpGraphToFile(buffername);
1563 sprintf(buffername, "graph%04u", get_execution_number());
1564 dumpGraph(buffername);
1567 model_print("Execution trace %d:", get_execution_number());
1568 if (scheduler->all_threads_sleeping())
1569 model_print(" SLEEP-SET REDUNDANT");
1570 if (have_bug_reports())
1571 model_print(" DETECTED BUG(S)");
1575 print_list(&action_trace);
1581 * Add a Thread to the system for the first time. Should only be called once
1583 * @param t The Thread to add
1585 void ModelExecution::add_thread(Thread *t)
1587 unsigned int i = id_to_int(t->get_id());
1588 if (i >= thread_map.size())
1589 thread_map.resize(i + 1);
1591 if (!t->is_model_thread())
1592 scheduler->add_thread(t);
1596 * @brief Get a Thread reference by its ID
1597 * @param tid The Thread's ID
1598 * @return A Thread reference
1600 Thread * ModelExecution::get_thread(thread_id_t tid) const
1602 unsigned int i = id_to_int(tid);
1603 if (i < thread_map.size())
1604 return thread_map[i];
1609 * @brief Get a reference to the Thread in which a ModelAction was executed
1610 * @param act The ModelAction
1611 * @return A Thread reference
1613 Thread * ModelExecution::get_thread(const ModelAction *act) const
1615 return get_thread(act->get_tid());
1619 * @brief Get a Thread reference by its pthread ID
1620 * @param index The pthread's ID
1621 * @return A Thread reference
1623 Thread * ModelExecution::get_pthread(pthread_t pid) {
1629 uint32_t thread_id = x.v;
1630 if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
1635 * @brief Check if a Thread is currently enabled
1636 * @param t The Thread to check
1637 * @return True if the Thread is currently enabled
1639 bool ModelExecution::is_enabled(Thread *t) const
1641 return scheduler->is_enabled(t);
1645 * @brief Check if a Thread is currently enabled
1646 * @param tid The ID of the Thread to check
1647 * @return True if the Thread is currently enabled
1649 bool ModelExecution::is_enabled(thread_id_t tid) const
1651 return scheduler->is_enabled(tid);
1655 * @brief Select the next thread to execute based on the curren action
1657 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
1658 * actions should be followed by the execution of their child thread. In either
1659 * case, the current action should determine the next thread schedule.
1661 * @param curr The current action
1662 * @return The next thread to run, if the current action will determine this
1663 * selection; otherwise NULL
1665 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
1667 /* Do not split atomic RMW */
1668 if (curr->is_rmwr() && !paused_by_fuzzer(curr))
1669 return get_thread(curr);
1670 /* Follow CREATE with the created thread */
1671 /* which is not needed, because model.cc takes care of this */
1672 if (curr->get_type() == THREAD_CREATE)
1673 return curr->get_thread_operand();
1674 if (curr->get_type() == PTHREAD_CREATE) {
1675 return curr->get_thread_operand();
1680 /** @param act A read atomic action */
1681 bool ModelExecution::paused_by_fuzzer(const ModelAction * act) const
1683 ASSERT(act->is_read());
1685 // Actions paused by fuzzer have their sequence number reset to 0
1686 return act->get_seq_number() == 0;
1690 * Takes the next step in the execution, if possible.
1691 * @param curr The current step to take
1692 * @return Returns the next Thread to run, if any; NULL if this execution
1695 Thread * ModelExecution::take_step(ModelAction *curr)
1697 Thread *curr_thrd = get_thread(curr);
1698 ASSERT(curr_thrd->get_state() == THREAD_READY);
1700 ASSERT(check_action_enabled(curr)); /* May have side effects? */
1701 curr = check_current_action(curr);
1704 /* Process this action in ModelHistory for records */
1705 model->get_history()->process_action( curr, curr->get_tid() );
1707 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
1708 scheduler->remove_thread(curr_thrd);
1710 return action_select_next_thread(curr);
1713 Fuzzer * ModelExecution::getFuzzer() {