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),
31 bad_synchronization(false),
35 ~model_snapshot_members() {
36 for (unsigned int i = 0;i < bugs.size();i++)
41 unsigned int next_thread_id;
42 modelclock_t used_sequence_numbers;
43 SnapVector<bug_message *> bugs;
44 /** @brief Incorrectly-ordered synchronization was made */
45 bool bad_synchronization;
51 /** @brief Constructor */
52 ModelExecution::ModelExecution(ModelChecker *m, Scheduler *scheduler) :
57 thread_map(2), /* We'll always need at least 2 threads */
61 condvar_waiters_map(),
65 thrd_last_fence_release(),
66 priv(new struct model_snapshot_members ()),
67 mo_graph(new CycleGraph()),
68 fuzzer(new NewFuzzer()),
70 thrd_func_act_lists(),
73 /* Initialize a model-checker thread, for special ModelActions */
74 model_thread = new Thread(get_next_id());
75 add_thread(model_thread);
76 scheduler->register_engine(this);
77 fuzzer->register_engine(m->get_history(), this);
80 /** @brief Destructor */
81 ModelExecution::~ModelExecution()
83 for (unsigned int i = 0;i < get_num_threads();i++)
84 delete get_thread(int_to_id(i));
90 int ModelExecution::get_execution_number() const
92 return model->get_execution_number();
95 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
97 action_list_t *tmp = hash->get(ptr);
99 tmp = new action_list_t();
105 static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
107 SnapVector<action_list_t> *tmp = hash->get(ptr);
109 tmp = new SnapVector<action_list_t>();
115 /** @return a thread ID for a new Thread */
116 thread_id_t ModelExecution::get_next_id()
118 return priv->next_thread_id++;
121 /** @return the number of user threads created during this execution */
122 unsigned int ModelExecution::get_num_threads() const
124 return priv->next_thread_id;
127 /** @return a sequence number for a new ModelAction */
128 modelclock_t ModelExecution::get_next_seq_num()
130 return ++priv->used_sequence_numbers;
133 /** Restore the last used sequence number when actions of a thread are postponed by Fuzzer */
134 void ModelExecution::restore_last_seq_num()
136 priv->used_sequence_numbers--;
140 * @brief Should the current action wake up a given thread?
142 * @param curr The current action
143 * @param thread The thread that we might wake up
144 * @return True, if we should wake up the sleeping thread; false otherwise
146 bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
148 const ModelAction *asleep = thread->get_pending();
149 /* Don't allow partial RMW to wake anyone up */
152 /* Synchronizing actions may have been backtracked */
153 if (asleep->could_synchronize_with(curr))
155 /* All acquire/release fences and fence-acquire/store-release */
156 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
158 /* Fence-release + store can awake load-acquire on the same location */
159 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
160 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
161 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
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);
184 /** @brief Alert the model-checker that an incorrectly-ordered
185 * synchronization was made */
186 void ModelExecution::set_bad_synchronization()
188 priv->bad_synchronization = true;
191 bool ModelExecution::assert_bug(const char *msg)
193 priv->bugs.push_back(new bug_message(msg));
195 if (isfeasibleprefix()) {
202 /** @return True, if any bugs have been reported for this execution */
203 bool ModelExecution::have_bug_reports() const
205 return priv->bugs.size() != 0;
208 SnapVector<bug_message *> * ModelExecution::get_bugs() const
214 * Check whether the current trace has triggered an assertion which should halt
217 * @return True, if the execution should be aborted; false otherwise
219 bool ModelExecution::has_asserted() const
221 return priv->asserted;
225 * Trigger a trace assertion which should cause this execution to be halted.
226 * This can be due to a detected bug or due to an infeasibility that should
229 void ModelExecution::set_assert()
231 priv->asserted = true;
235 * Check if we are in a deadlock. Should only be called at the end of an
236 * execution, although it should not give false positives in the middle of an
237 * execution (there should be some ENABLED thread).
239 * @return True if program is in a deadlock; false otherwise
241 bool ModelExecution::is_deadlocked() const
243 bool blocking_threads = false;
244 for (unsigned int i = 0;i < get_num_threads();i++) {
245 thread_id_t tid = int_to_id(i);
248 Thread *t = get_thread(tid);
249 if (!t->is_model_thread() && t->get_pending())
250 blocking_threads = true;
252 return blocking_threads;
256 * Check if this is a complete execution. That is, have all thread completed
257 * execution (rather than exiting because sleep sets have forced a redundant
260 * @return True if the execution is complete.
262 bool ModelExecution::is_complete_execution() const
264 for (unsigned int i = 0;i < get_num_threads();i++)
265 if (is_enabled(int_to_id(i)))
270 ModelAction * ModelExecution::convertNonAtomicStore(void * location) {
271 uint64_t value = *((const uint64_t *) location);
272 modelclock_t storeclock;
273 thread_id_t storethread;
274 getStoreThreadAndClock(location, &storethread, &storeclock);
275 setAtomicStoreFlag(location);
276 ModelAction * act = new ModelAction(NONATOMIC_WRITE, memory_order_relaxed, location, value, get_thread(storethread));
277 act->set_seq_number(storeclock);
278 add_normal_write_to_lists(act);
279 add_write_to_lists(act);
280 w_modification_order(act);
281 model->get_history()->process_action(act, act->get_tid());
286 * Processes a read model action.
287 * @param curr is the read model action to process.
288 * @param rf_set is the set of model actions we can possibly read from
289 * @return True if processing this read updates the mo_graph.
291 bool ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> * rf_set)
293 SnapVector<const ModelAction *> * priorset = new SnapVector<const ModelAction *>();
294 bool hasnonatomicstore = hasNonAtomicStore(curr->get_location());
295 if (hasnonatomicstore) {
296 ModelAction * nonatomicstore = convertNonAtomicStore(curr->get_location());
297 rf_set->push_back(nonatomicstore);
301 int index = fuzzer->selectWrite(curr, rf_set);
302 if (index == -1) // no feasible write exists
305 ModelAction *rf = (*rf_set)[index];
308 bool canprune = false;
309 if (r_modification_order(curr, rf, priorset, &canprune)) {
310 for(unsigned int i=0;i<priorset->size();i++) {
311 mo_graph->addEdge((*priorset)[i], rf);
314 get_thread(curr)->set_return_value(curr->get_return_value());
316 if (canprune && curr->get_type() == ATOMIC_READ) {
317 int tid = id_to_int(curr->get_tid());
318 (*obj_thrd_map.get(curr->get_location()))[tid].pop_back();
323 (*rf_set)[index] = rf_set->back();
329 * Processes a lock, trylock, or unlock model action. @param curr is
330 * the read model action to process.
332 * The try lock operation checks whether the lock is taken. If not,
333 * it falls to the normal lock operation case. If so, it returns
336 * The lock operation has already been checked that it is enabled, so
337 * it just grabs the lock and synchronizes with the previous unlock.
339 * The unlock operation has to re-enable all of the threads that are
340 * waiting on the lock.
342 * @return True if synchronization was updated; false otherwise
344 bool ModelExecution::process_mutex(ModelAction *curr)
346 cdsc::mutex *mutex = curr->get_mutex();
347 struct cdsc::mutex_state *state = NULL;
350 state = mutex->get_state();
352 switch (curr->get_type()) {
353 case ATOMIC_TRYLOCK: {
354 bool success = !state->locked;
355 curr->set_try_lock(success);
357 get_thread(curr)->set_return_value(0);
360 get_thread(curr)->set_return_value(1);
362 //otherwise fall into the lock case
364 //TODO: FIND SOME BETTER WAY TO CHECK LOCK INITIALIZED OR NOT
365 //if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
366 // assert_bug("Lock access before initialization");
367 state->locked = get_thread(curr);
368 ModelAction *unlock = get_last_unlock(curr);
369 //synchronize with the previous unlock statement
370 if (unlock != NULL) {
371 synchronize(unlock, curr);
377 case ATOMIC_UNLOCK: {
378 //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...
380 /* wake up the other threads */
381 for (unsigned int i = 0;i < get_num_threads();i++) {
382 Thread *t = get_thread(int_to_id(i));
383 Thread *curr_thrd = get_thread(curr);
384 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
388 /* unlock the lock - after checking who was waiting on it */
389 state->locked = NULL;
391 if (!curr->is_wait())
392 break;/* The rest is only for ATOMIC_WAIT */
396 case ATOMIC_NOTIFY_ALL: {
397 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
398 //activate all the waiting threads
399 for (sllnode<ModelAction *> * rit = waiters->begin();rit != NULL;rit=rit->getNext()) {
400 scheduler->wake(get_thread(rit->getVal()));
405 case ATOMIC_NOTIFY_ONE: {
406 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
407 if (waiters->size() != 0) {
408 Thread * thread = fuzzer->selectNotify(waiters);
409 scheduler->wake(thread);
421 * Process a write ModelAction
422 * @param curr The ModelAction to process
423 * @return True if the mo_graph was updated or promises were resolved
425 void ModelExecution::process_write(ModelAction *curr)
427 w_modification_order(curr);
428 get_thread(curr)->set_return_value(VALUE_NONE);
432 * Process a fence ModelAction
433 * @param curr The ModelAction to process
434 * @return True if synchronization was updated
436 bool ModelExecution::process_fence(ModelAction *curr)
439 * fence-relaxed: no-op
440 * fence-release: only log the occurence (not in this function), for
441 * use in later synchronization
442 * fence-acquire (this function): search for hypothetical release
444 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
446 bool updated = false;
447 if (curr->is_acquire()) {
448 action_list_t *list = &action_trace;
449 sllnode<ModelAction *> * rit;
450 /* Find X : is_read(X) && X --sb-> curr */
451 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
452 ModelAction *act = rit->getVal();
455 if (act->get_tid() != curr->get_tid())
457 /* Stop at the beginning of the thread */
458 if (act->is_thread_start())
460 /* Stop once we reach a prior fence-acquire */
461 if (act->is_fence() && act->is_acquire())
465 /* read-acquire will find its own release sequences */
466 if (act->is_acquire())
469 /* Establish hypothetical release sequences */
470 ClockVector *cv = get_hb_from_write(act->get_reads_from());
471 if (cv != NULL && curr->get_cv()->merge(cv))
479 * @brief Process the current action for thread-related activity
481 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
482 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
483 * synchronization, etc. This function is a no-op for non-THREAD actions
484 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
486 * @param curr The current action
487 * @return True if synchronization was updated or a thread completed
489 void ModelExecution::process_thread_action(ModelAction *curr)
491 switch (curr->get_type()) {
492 case THREAD_CREATE: {
493 thrd_t *thrd = (thrd_t *)curr->get_location();
494 struct thread_params *params = (struct thread_params *)curr->get_value();
495 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
496 curr->set_thread_operand(th);
498 th->set_creation(curr);
501 case PTHREAD_CREATE: {
502 (*(uint32_t *)curr->get_location()) = pthread_counter++;
504 struct pthread_params *params = (struct pthread_params *)curr->get_value();
505 Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
506 curr->set_thread_operand(th);
508 th->set_creation(curr);
510 if ( pthread_map.size() < pthread_counter )
511 pthread_map.resize( pthread_counter );
512 pthread_map[ pthread_counter-1 ] = th;
517 Thread *blocking = curr->get_thread_operand();
518 ModelAction *act = get_last_action(blocking->get_id());
519 synchronize(act, curr);
523 Thread *blocking = curr->get_thread_operand();
524 ModelAction *act = get_last_action(blocking->get_id());
525 synchronize(act, curr);
526 break; // WL: to be add (modified)
529 case THREADONLY_FINISH:
530 case THREAD_FINISH: {
531 Thread *th = get_thread(curr);
532 if (curr->get_type() == THREAD_FINISH &&
533 th == model->getInitThread()) {
539 /* Wake up any joining threads */
540 for (unsigned int i = 0;i < get_num_threads();i++) {
541 Thread *waiting = get_thread(int_to_id(i));
542 if (waiting->waiting_on() == th &&
543 waiting->get_pending()->is_thread_join())
544 scheduler->wake(waiting);
558 * Initialize the current action by performing one or more of the following
559 * actions, as appropriate: merging RMWR and RMWC/RMW actions,
560 * manipulating backtracking sets, allocating and
561 * initializing clock vectors, and computing the promises to fulfill.
563 * @param curr The current action, as passed from the user context; may be
564 * freed/invalidated after the execution of this function, with a different
565 * action "returned" its place (pass-by-reference)
566 * @return True if curr is a newly-explored action; false otherwise
568 bool ModelExecution::initialize_curr_action(ModelAction **curr)
570 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
571 ModelAction *newcurr = process_rmw(*curr);
577 ModelAction *newcurr = *curr;
579 newcurr->set_seq_number(get_next_seq_num());
580 /* Always compute new clock vector */
581 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
583 /* Assign most recent release fence */
584 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
586 return true; /* This was a new ModelAction */
591 * @brief Establish reads-from relation between two actions
593 * Perform basic operations involved with establishing a concrete rf relation,
594 * including setting the ModelAction data and checking for release sequences.
596 * @param act The action that is reading (must be a read)
597 * @param rf The action from which we are reading (must be a write)
599 * @return True if this read established synchronization
602 void ModelExecution::read_from(ModelAction *act, ModelAction *rf)
605 ASSERT(rf->is_write());
607 act->set_read_from(rf);
608 if (act->is_acquire()) {
609 ClockVector *cv = get_hb_from_write(rf);
612 act->get_cv()->merge(cv);
617 * @brief Synchronizes two actions
619 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
620 * This function performs the synchronization as well as providing other hooks
621 * for other checks along with synchronization.
623 * @param first The left-hand side of the synchronizes-with relation
624 * @param second The right-hand side of the synchronizes-with relation
625 * @return True if the synchronization was successful (i.e., was consistent
626 * with the execution order); false otherwise
628 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
630 if (*second < *first) {
631 set_bad_synchronization();
634 return second->synchronize_with(first);
638 * @brief Check whether a model action is enabled.
640 * Checks whether an operation would be successful (i.e., is a lock already
641 * locked, or is the joined thread already complete).
643 * For yield-blocking, yields are never enabled.
645 * @param curr is the ModelAction to check whether it is enabled.
646 * @return a bool that indicates whether the action is enabled.
648 bool ModelExecution::check_action_enabled(ModelAction *curr) {
649 if (curr->is_lock()) {
650 cdsc::mutex *lock = curr->get_mutex();
651 struct cdsc::mutex_state *state = lock->get_state();
654 } else if (curr->is_thread_join()) {
655 Thread *blocking = curr->get_thread_operand();
656 if (!blocking->is_complete()) {
659 } else if (curr->is_sleep()) {
660 if (!fuzzer->shouldSleep(curr))
668 * This is the heart of the model checker routine. It performs model-checking
669 * actions corresponding to a given "current action." Among other processes, it
670 * calculates reads-from relationships, updates synchronization clock vectors,
671 * forms a memory_order constraints graph, and handles replay/backtrack
672 * execution when running permutations of previously-observed executions.
674 * @param curr The current action to process
675 * @return The ModelAction that is actually executed; may be different than
678 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
681 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
682 bool newly_explored = initialize_curr_action(&curr);
686 wake_up_sleeping_actions(curr);
688 /* Add uninitialized actions to lists */
689 if (!second_part_of_rmw && curr->get_type() != NOOP)
690 add_uninit_action_to_lists(curr);
692 SnapVector<ModelAction *> * rf_set = NULL;
693 /* Build may_read_from set for newly-created actions */
694 if (newly_explored && curr->is_read())
695 rf_set = build_may_read_from(curr);
697 if (curr->is_read() && !second_part_of_rmw) {
698 bool success = process_read(curr, rf_set);
701 return curr; // Do not add action to lists
703 ASSERT(rf_set == NULL);
705 /* Add the action to lists */
706 if (!second_part_of_rmw && curr->get_type() != NOOP)
707 add_action_to_lists(curr);
709 if (curr->is_write())
710 add_write_to_lists(curr);
712 process_thread_action(curr);
714 if (curr->is_write())
717 if (curr->is_fence())
720 if (curr->is_mutex_op())
727 * This is the strongest feasibility check available.
728 * @return whether the current trace (partial or complete) must be a prefix of
731 bool ModelExecution::isfeasibleprefix() const
733 return !is_infeasible();
737 * Print disagnostic information about an infeasible execution
738 * @param prefix A string to prefix the output with; if NULL, then a default
739 * message prefix will be provided
741 void ModelExecution::print_infeasibility(const char *prefix) const
745 if (priv->bad_synchronization)
746 ptr += sprintf(ptr, "[bad sw ordering]");
748 model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
752 * Check if the current partial trace is infeasible. Does not check any
753 * end-of-execution flags, which might rule out the execution. Thus, this is
754 * useful only for ruling an execution as infeasible.
755 * @return whether the current partial trace is infeasible.
757 bool ModelExecution::is_infeasible() const
759 return priv->bad_synchronization;
762 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
763 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
764 ModelAction *lastread = get_last_action(act->get_tid());
765 lastread->process_rmw(act);
767 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
773 * @brief Updates the mo_graph with the constraints imposed from the current
776 * Basic idea is the following: Go through each other thread and find
777 * the last action that happened before our read. Two cases:
779 * -# The action is a write: that write must either occur before
780 * the write we read from or be the write we read from.
781 * -# The action is a read: the write that that action read from
782 * must occur before the write we read from or be the same write.
784 * @param curr The current action. Must be a read.
785 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
786 * @return True if modification order edges were added; false otherwise
789 bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf, SnapVector<const ModelAction *> * priorset, bool * canprune)
791 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
793 ASSERT(curr->is_read());
795 /* Last SC fence in the current thread */
796 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
798 int tid = curr->get_tid();
799 ModelAction *prev_same_thread = NULL;
800 /* Iterate over all threads */
801 for (i = 0;i < thrd_lists->size();i++, tid = (((unsigned int)(tid+1)) == thrd_lists->size()) ? 0 : tid + 1) {
802 /* Last SC fence in thread tid */
803 ModelAction *last_sc_fence_thread_local = NULL;
805 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(tid), NULL);
807 /* Last SC fence in thread tid, before last SC fence in current thread */
808 ModelAction *last_sc_fence_thread_before = NULL;
809 if (last_sc_fence_local)
810 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(tid), last_sc_fence_local);
812 //Only need to iterate if either hb has changed for thread in question or SC fence after last operation...
813 if (prev_same_thread != NULL &&
814 (prev_same_thread->get_cv()->getClock(tid) == curr->get_cv()->getClock(tid)) &&
815 (last_sc_fence_thread_local == NULL || *last_sc_fence_thread_local < *prev_same_thread)) {
819 /* Iterate over actions in thread, starting from most recent */
820 action_list_t *list = &(*thrd_lists)[tid];
821 sllnode<ModelAction *> * rit;
822 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
823 ModelAction *act = rit->getVal();
828 /* Don't want to add reflexive edges on 'rf' */
829 if (act->equals(rf)) {
830 if (act->happens_before(curr))
836 if (act->is_write()) {
837 /* C++, Section 29.3 statement 5 */
838 if (curr->is_seqcst() && last_sc_fence_thread_local &&
839 *act < *last_sc_fence_thread_local) {
840 if (mo_graph->checkReachable(rf, act))
842 priorset->push_back(act);
845 /* C++, Section 29.3 statement 4 */
846 else if (act->is_seqcst() && last_sc_fence_local &&
847 *act < *last_sc_fence_local) {
848 if (mo_graph->checkReachable(rf, act))
850 priorset->push_back(act);
853 /* C++, Section 29.3 statement 6 */
854 else if (last_sc_fence_thread_before &&
855 *act < *last_sc_fence_thread_before) {
856 if (mo_graph->checkReachable(rf, act))
858 priorset->push_back(act);
864 * Include at most one act per-thread that "happens
867 if (act->happens_before(curr)) {
869 if (last_sc_fence_local == NULL ||
870 (*last_sc_fence_local < *act)) {
871 prev_same_thread = act;
874 if (act->is_write()) {
875 if (mo_graph->checkReachable(rf, act))
877 priorset->push_back(act);
879 const ModelAction *prevrf = act->get_reads_from();
880 if (!prevrf->equals(rf)) {
881 if (mo_graph->checkReachable(rf, prevrf))
883 priorset->push_back(prevrf);
885 if (act->get_tid() == curr->get_tid()) {
886 //Can prune curr from obj list
899 * Updates the mo_graph with the constraints imposed from the current write.
901 * Basic idea is the following: Go through each other thread and find
902 * the lastest action that happened before our write. Two cases:
904 * (1) The action is a write => that write must occur before
907 * (2) The action is a read => the write that that action read from
908 * must occur before the current write.
910 * This method also handles two other issues:
912 * (I) Sequential Consistency: Making sure that if the current write is
913 * seq_cst, that it occurs after the previous seq_cst write.
915 * (II) Sending the write back to non-synchronizing reads.
917 * @param curr The current action. Must be a write.
918 * @param send_fv A vector for stashing reads to which we may pass our future
919 * value. If NULL, then don't record any future values.
920 * @return True if modification order edges were added; false otherwise
922 void ModelExecution::w_modification_order(ModelAction *curr)
924 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
926 ASSERT(curr->is_write());
928 SnapList<ModelAction *> edgeset;
930 if (curr->is_seqcst()) {
931 /* We have to at least see the last sequentially consistent write,
932 so we are initialized. */
933 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
934 if (last_seq_cst != NULL) {
935 edgeset.push_back(last_seq_cst);
937 //update map for next query
938 obj_last_sc_map.put(curr->get_location(), curr);
941 /* Last SC fence in the current thread */
942 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
944 /* Iterate over all threads */
945 for (i = 0;i < thrd_lists->size();i++) {
946 /* Last SC fence in thread i, before last SC fence in current thread */
947 ModelAction *last_sc_fence_thread_before = NULL;
948 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
949 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
951 /* Iterate over actions in thread, starting from most recent */
952 action_list_t *list = &(*thrd_lists)[i];
953 sllnode<ModelAction*>* rit;
954 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
955 ModelAction *act = rit->getVal();
958 * 1) If RMW and it actually read from something, then we
959 * already have all relevant edges, so just skip to next
962 * 2) If RMW and it didn't read from anything, we should
963 * whatever edge we can get to speed up convergence.
965 * 3) If normal write, we need to look at earlier actions, so
966 * continue processing list.
968 if (curr->is_rmw()) {
969 if (curr->get_reads_from() != NULL)
977 /* C++, Section 29.3 statement 7 */
978 if (last_sc_fence_thread_before && act->is_write() &&
979 *act < *last_sc_fence_thread_before) {
980 edgeset.push_back(act);
985 * Include at most one act per-thread that "happens
988 if (act->happens_before(curr)) {
990 * Note: if act is RMW, just add edge:
992 * The following edge should be handled elsewhere:
993 * readfrom(act) --mo--> act
996 edgeset.push_back(act);
997 else if (act->is_read()) {
998 //if previous read accessed a null, just keep going
999 edgeset.push_back(act->get_reads_from());
1005 mo_graph->addEdges(&edgeset, curr);
1010 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1011 * some constraints. This method checks one the following constraint (others
1012 * require compiler support):
1014 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1015 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
1017 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1019 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1021 /* Iterate over all threads */
1022 for (i = 0;i < thrd_lists->size();i++) {
1023 const ModelAction *write_after_read = NULL;
1025 /* Iterate over actions in thread, starting from most recent */
1026 action_list_t *list = &(*thrd_lists)[i];
1027 sllnode<ModelAction *>* rit;
1028 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
1029 ModelAction *act = rit->getVal();
1031 /* Don't disallow due to act == reader */
1032 if (!reader->happens_before(act) || reader == act)
1034 else if (act->is_write())
1035 write_after_read = act;
1036 else if (act->is_read() && act->get_reads_from() != NULL)
1037 write_after_read = act->get_reads_from();
1040 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1047 * Computes the clock vector that happens before propagates from this write.
1049 * @param rf The action that might be part of a release sequence. Must be a
1051 * @return ClockVector of happens before relation.
1054 ClockVector * ModelExecution::get_hb_from_write(ModelAction *rf) const {
1055 SnapVector<ModelAction *> * processset = NULL;
1056 for ( ;rf != NULL;rf = rf->get_reads_from()) {
1057 ASSERT(rf->is_write());
1058 if (!rf->is_rmw() || (rf->is_acquire() && rf->is_release()) || rf->get_rfcv() != NULL)
1060 if (processset == NULL)
1061 processset = new SnapVector<ModelAction *>();
1062 processset->push_back(rf);
1065 int i = (processset == NULL) ? 0 : processset->size();
1067 ClockVector * vec = NULL;
1069 if (rf->get_rfcv() != NULL) {
1070 vec = rf->get_rfcv();
1071 } else if (rf->is_acquire() && rf->is_release()) {
1073 } else if (rf->is_release() && !rf->is_rmw()) {
1075 } else if (rf->is_release()) {
1076 //have rmw that is release and doesn't have a rfcv
1077 (vec = new ClockVector(vec, NULL))->merge(rf->get_cv());
1080 //operation that isn't release
1081 if (rf->get_last_fence_release()) {
1083 vec = rf->get_last_fence_release()->get_cv();
1085 (vec=new ClockVector(vec, NULL))->merge(rf->get_last_fence_release()->get_cv());
1091 rf = (*processset)[i];
1095 if (processset != NULL)
1101 * Performs various bookkeeping operations for the current ModelAction when it is
1102 * the first atomic action occurred at its memory location.
1104 * For instance, adds uninitialized action to the per-object, per-thread action vector
1105 * and to the action trace list of all thread actions.
1107 * @param act is the ModelAction to process.
1109 void ModelExecution::add_uninit_action_to_lists(ModelAction *act)
1111 int tid = id_to_int(act->get_tid());
1112 ModelAction *uninit = NULL;
1114 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1115 if (list->empty() && act->is_atomic_var()) {
1116 uninit = get_uninitialized_action(act);
1117 uninit_id = id_to_int(uninit->get_tid());
1118 list->push_front(uninit);
1119 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, act->get_location());
1120 if ((int)vec->size() <= uninit_id) {
1121 int oldsize = (int) vec->size();
1122 vec->resize(uninit_id + 1);
1123 for(int i = oldsize; i < uninit_id + 1; i++) {
1124 new (&(*vec)[i]) action_list_t();
1127 (*vec)[uninit_id].push_front(uninit);
1130 // Update action trace, a total order of all actions
1132 action_trace.push_front(uninit);
1134 // Update obj_thrd_map, a per location, per thread, order of actions
1135 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1136 if ((int)vec->size() <= tid) {
1137 uint oldsize = vec->size();
1138 vec->resize(priv->next_thread_id);
1139 for(uint i = oldsize; i < priv->next_thread_id; i++)
1140 new (&(*vec)[i]) action_list_t();
1143 (*vec)[uninit_id].push_front(uninit);
1145 // Update thrd_last_action, the last action taken by each thrad
1146 if ((int)thrd_last_action.size() <= tid)
1147 thrd_last_action.resize(get_num_threads());
1149 thrd_last_action[uninit_id] = uninit;
1154 * Performs various bookkeeping operations for the current ModelAction. For
1155 * instance, adds action to the per-object, per-thread action vector and to the
1156 * action trace list of all thread actions.
1158 * @param act is the ModelAction to add.
1160 void ModelExecution::add_action_to_lists(ModelAction *act)
1162 int tid = id_to_int(act->get_tid());
1163 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1164 list->push_back(act);
1166 // Update action trace, a total order of all actions
1167 action_trace.push_back(act);
1169 // Update obj_thrd_map, a per location, per thread, order of actions
1170 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1171 if ((int)vec->size() <= tid) {
1172 uint oldsize = vec->size();
1173 vec->resize(priv->next_thread_id);
1174 for(uint i = oldsize; i < priv->next_thread_id; i++)
1175 new (&(*vec)[i]) action_list_t();
1177 (*vec)[tid].push_back(act);
1179 // Update thrd_last_action, the last action taken by each thrad
1180 if ((int)thrd_last_action.size() <= tid)
1181 thrd_last_action.resize(get_num_threads());
1182 thrd_last_action[tid] = act;
1184 // Update thrd_last_fence_release, the last release fence taken by each thread
1185 if (act->is_fence() && act->is_release()) {
1186 if ((int)thrd_last_fence_release.size() <= tid)
1187 thrd_last_fence_release.resize(get_num_threads());
1188 thrd_last_fence_release[tid] = act;
1191 if (act->is_wait()) {
1192 void *mutex_loc = (void *) act->get_value();
1193 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
1195 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
1196 if ((int)vec->size() <= tid) {
1197 uint oldsize = vec->size();
1198 vec->resize(priv->next_thread_id);
1199 for(uint i = oldsize; i < priv->next_thread_id; i++)
1200 new (&(*vec)[i]) action_list_t();
1202 (*vec)[tid].push_back(act);
1206 void insertIntoActionList(action_list_t *list, ModelAction *act) {
1207 sllnode<ModelAction*> * rit = list->end();
1208 modelclock_t next_seq = act->get_seq_number();
1209 if (rit == NULL || (rit->getVal()->get_seq_number() == next_seq))
1210 list->push_back(act);
1212 for(;rit != NULL;rit=rit->getPrev()) {
1213 if (rit->getVal()->get_seq_number() == next_seq) {
1214 list->insertAfter(rit, act);
1221 void insertIntoActionListAndSetCV(action_list_t *list, ModelAction *act) {
1222 sllnode<ModelAction*> * rit = list->end();
1223 modelclock_t next_seq = act->get_seq_number();
1225 act->create_cv(NULL);
1226 } else if (rit->getVal()->get_seq_number() == next_seq) {
1227 act->create_cv(rit->getVal());
1228 list->push_back(act);
1230 for(;rit != NULL;rit=rit->getPrev()) {
1231 if (rit->getVal()->get_seq_number() == next_seq) {
1232 act->create_cv(rit->getVal());
1233 list->insertAfter(rit, act);
1241 * Performs various bookkeeping operations for a normal write. The
1242 * complication is that we are typically inserting a normal write
1243 * lazily, so we need to insert it into the middle of lists.
1245 * @param act is the ModelAction to add.
1248 void ModelExecution::add_normal_write_to_lists(ModelAction *act)
1250 int tid = id_to_int(act->get_tid());
1251 insertIntoActionListAndSetCV(&action_trace, act);
1253 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1254 insertIntoActionList(list, act);
1256 // Update obj_thrd_map, a per location, per thread, order of actions
1257 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1258 if (tid >= (int)vec->size()) {
1259 uint oldsize =vec->size();
1260 vec->resize(priv->next_thread_id);
1261 for(uint i=oldsize;i<priv->next_thread_id;i++)
1262 new (&(*vec)[i]) action_list_t();
1264 insertIntoActionList(&(*vec)[tid],act);
1266 // Update thrd_last_action, the last action taken by each thrad
1267 if (thrd_last_action[tid]->get_seq_number() == act->get_seq_number())
1268 thrd_last_action[tid] = act;
1272 void ModelExecution::add_write_to_lists(ModelAction *write) {
1273 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, write->get_location());
1274 int tid = id_to_int(write->get_tid());
1275 if (tid >= (int)vec->size()) {
1276 uint oldsize =vec->size();
1277 vec->resize(priv->next_thread_id);
1278 for(uint i=oldsize;i<priv->next_thread_id;i++)
1279 new (&(*vec)[i]) action_list_t();
1281 (*vec)[tid].push_back(write);
1285 * @brief Get the last action performed by a particular Thread
1286 * @param tid The thread ID of the Thread in question
1287 * @return The last action in the thread
1289 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
1291 int threadid = id_to_int(tid);
1292 if (threadid < (int)thrd_last_action.size())
1293 return thrd_last_action[id_to_int(tid)];
1299 * @brief Get the last fence release performed by a particular Thread
1300 * @param tid The thread ID of the Thread in question
1301 * @return The last fence release in the thread, if one exists; NULL otherwise
1303 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
1305 int threadid = id_to_int(tid);
1306 if (threadid < (int)thrd_last_fence_release.size())
1307 return thrd_last_fence_release[id_to_int(tid)];
1313 * Gets the last memory_order_seq_cst write (in the total global sequence)
1314 * performed on a particular object (i.e., memory location), not including the
1316 * @param curr The current ModelAction; also denotes the object location to
1318 * @return The last seq_cst write
1320 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
1322 void *location = curr->get_location();
1323 return obj_last_sc_map.get(location);
1327 * Gets the last memory_order_seq_cst fence (in the total global sequence)
1328 * performed in a particular thread, prior to a particular fence.
1329 * @param tid The ID of the thread to check
1330 * @param before_fence The fence from which to begin the search; if NULL, then
1331 * search for the most recent fence in the thread.
1332 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
1334 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
1336 /* All fences should have location FENCE_LOCATION */
1337 action_list_t *list = obj_map.get(FENCE_LOCATION);
1342 sllnode<ModelAction*>* rit = list->end();
1345 for (;rit != NULL;rit=rit->getPrev())
1346 if (rit->getVal() == before_fence)
1349 ASSERT(rit->getVal() == before_fence);
1353 for (;rit != NULL;rit=rit->getPrev()) {
1354 ModelAction *act = rit->getVal();
1355 if (act->is_fence() && (tid == act->get_tid()) && act->is_seqcst())
1362 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1363 * location). This function identifies the mutex according to the current
1364 * action, which is presumed to perform on the same mutex.
1365 * @param curr The current ModelAction; also denotes the object location to
1367 * @return The last unlock operation
1369 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
1371 void *location = curr->get_location();
1373 action_list_t *list = obj_map.get(location);
1374 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1375 sllnode<ModelAction*>* rit;
1376 for (rit = list->end();rit != NULL;rit=rit->getPrev())
1377 if (rit->getVal()->is_unlock() || rit->getVal()->is_wait())
1378 return rit->getVal();
1382 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
1384 ModelAction *parent = get_last_action(tid);
1386 parent = get_thread(tid)->get_creation();
1391 * Returns the clock vector for a given thread.
1392 * @param tid The thread whose clock vector we want
1393 * @return Desired clock vector
1395 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
1397 ModelAction *firstaction=get_parent_action(tid);
1398 return firstaction != NULL ? firstaction->get_cv() : NULL;
1401 bool valequals(uint64_t val1, uint64_t val2, int size) {
1404 return ((uint8_t)val1) == ((uint8_t)val2);
1406 return ((uint16_t)val1) == ((uint16_t)val2);
1408 return ((uint32_t)val1) == ((uint32_t)val2);
1418 * Build up an initial set of all past writes that this 'read' action may read
1419 * from, as well as any previously-observed future values that must still be valid.
1421 * @param curr is the current ModelAction that we are exploring; it must be a
1424 SnapVector<ModelAction *> * ModelExecution::build_may_read_from(ModelAction *curr)
1426 SnapVector<action_list_t> *thrd_lists = obj_wr_thrd_map.get(curr->get_location());
1428 ASSERT(curr->is_read());
1430 ModelAction *last_sc_write = NULL;
1432 if (curr->is_seqcst())
1433 last_sc_write = get_last_seq_cst_write(curr);
1435 SnapVector<ModelAction *> * rf_set = new SnapVector<ModelAction *>();
1437 /* Iterate over all threads */
1438 for (i = 0;i < thrd_lists->size();i++) {
1439 /* Iterate over actions in thread, starting from most recent */
1440 action_list_t *list = &(*thrd_lists)[i];
1441 sllnode<ModelAction *> * rit;
1442 for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
1443 ModelAction *act = rit->getVal();
1448 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1449 bool allow_read = true;
1451 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
1454 /* Need to check whether we will have two RMW reading from the same value */
1455 if (curr->is_rmwr()) {
1456 /* It is okay if we have a failing CAS */
1457 if (!curr->is_rmwrcas() ||
1458 valequals(curr->get_value(), act->get_value(), curr->getSize())) {
1459 //Need to make sure we aren't the second RMW
1460 CycleNode * node = mo_graph->getNode_noCreate(act);
1461 if (node != NULL && node->getRMW() != NULL) {
1462 //we are the second RMW
1469 /* Only add feasible reads */
1470 rf_set->push_back(act);
1473 /* Include at most one act per-thread that "happens before" curr */
1474 if (act->happens_before(curr))
1479 if (DBG_ENABLED()) {
1480 model_print("Reached read action:\n");
1482 model_print("End printing read_from_past\n");
1488 * @brief Get an action representing an uninitialized atomic
1490 * This function may create a new one.
1492 * @param curr The current action, which prompts the creation of an UNINIT action
1493 * @return A pointer to the UNINIT ModelAction
1495 ModelAction * ModelExecution::get_uninitialized_action(ModelAction *curr) const
1497 ModelAction *act = curr->get_uninit_action();
1499 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
1500 curr->set_uninit_action(act);
1502 act->create_cv(NULL);
1506 static void print_list(action_list_t *list)
1508 sllnode<ModelAction*> *it;
1510 model_print("------------------------------------------------------------------------------------\n");
1511 model_print("# t Action type MO Location Value Rf CV\n");
1512 model_print("------------------------------------------------------------------------------------\n");
1514 unsigned int hash = 0;
1516 for (it = list->begin();it != NULL;it=it->getNext()) {
1517 const ModelAction *act = it->getVal();
1518 if (act->get_seq_number() > 0)
1520 hash = hash^(hash<<3)^(it->getVal()->hash());
1522 model_print("HASH %u\n", hash);
1523 model_print("------------------------------------------------------------------------------------\n");
1526 #if SUPPORT_MOD_ORDER_DUMP
1527 void ModelExecution::dumpGraph(char *filename)
1530 sprintf(buffer, "%s.dot", filename);
1531 FILE *file = fopen(buffer, "w");
1532 fprintf(file, "digraph %s {\n", filename);
1533 mo_graph->dumpNodes(file);
1534 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
1536 for (sllnode<ModelAction*>* it = action_trace.begin();it != NULL;it=it->getNext()) {
1537 ModelAction *act = it->getVal();
1538 if (act->is_read()) {
1539 mo_graph->dot_print_node(file, act);
1540 mo_graph->dot_print_edge(file,
1541 act->get_reads_from(),
1543 "label=\"rf\", color=red, weight=2");
1545 if (thread_array[act->get_tid()]) {
1546 mo_graph->dot_print_edge(file,
1547 thread_array[id_to_int(act->get_tid())],
1549 "label=\"sb\", color=blue, weight=400");
1552 thread_array[act->get_tid()] = act;
1554 fprintf(file, "}\n");
1555 model_free(thread_array);
1560 /** @brief Prints an execution trace summary. */
1561 void ModelExecution::print_summary()
1563 #if SUPPORT_MOD_ORDER_DUMP
1564 char buffername[100];
1565 sprintf(buffername, "exec%04u", get_execution_number());
1566 mo_graph->dumpGraphToFile(buffername);
1567 sprintf(buffername, "graph%04u", get_execution_number());
1568 dumpGraph(buffername);
1571 model_print("Execution trace %d:", get_execution_number());
1572 if (isfeasibleprefix()) {
1573 if (scheduler->all_threads_sleeping())
1574 model_print(" SLEEP-SET REDUNDANT");
1575 if (have_bug_reports())
1576 model_print(" DETECTED BUG(S)");
1578 print_infeasibility(" INFEASIBLE");
1581 print_list(&action_trace);
1587 * Add a Thread to the system for the first time. Should only be called once
1589 * @param t The Thread to add
1591 void ModelExecution::add_thread(Thread *t)
1593 unsigned int i = id_to_int(t->get_id());
1594 if (i >= thread_map.size())
1595 thread_map.resize(i + 1);
1597 if (!t->is_model_thread())
1598 scheduler->add_thread(t);
1602 * @brief Get a Thread reference by its ID
1603 * @param tid The Thread's ID
1604 * @return A Thread reference
1606 Thread * ModelExecution::get_thread(thread_id_t tid) const
1608 unsigned int i = id_to_int(tid);
1609 if (i < thread_map.size())
1610 return thread_map[i];
1615 * @brief Get a reference to the Thread in which a ModelAction was executed
1616 * @param act The ModelAction
1617 * @return A Thread reference
1619 Thread * ModelExecution::get_thread(const ModelAction *act) const
1621 return get_thread(act->get_tid());
1625 * @brief Get a Thread reference by its pthread ID
1626 * @param index The pthread's ID
1627 * @return A Thread reference
1629 Thread * ModelExecution::get_pthread(pthread_t pid) {
1635 uint32_t thread_id = x.v;
1636 if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
1641 * @brief Check if a Thread is currently enabled
1642 * @param t The Thread to check
1643 * @return True if the Thread is currently enabled
1645 bool ModelExecution::is_enabled(Thread *t) const
1647 return scheduler->is_enabled(t);
1651 * @brief Check if a Thread is currently enabled
1652 * @param tid The ID of the Thread to check
1653 * @return True if the Thread is currently enabled
1655 bool ModelExecution::is_enabled(thread_id_t tid) const
1657 return scheduler->is_enabled(tid);
1661 * @brief Select the next thread to execute based on the curren action
1663 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
1664 * actions should be followed by the execution of their child thread. In either
1665 * case, the current action should determine the next thread schedule.
1667 * @param curr The current action
1668 * @return The next thread to run, if the current action will determine this
1669 * selection; otherwise NULL
1671 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
1673 /* Do not split atomic RMW */
1674 if (curr->is_rmwr() && !paused_by_fuzzer(curr))
1675 return get_thread(curr);
1676 /* Follow CREATE with the created thread */
1677 /* which is not needed, because model.cc takes care of this */
1678 if (curr->get_type() == THREAD_CREATE)
1679 return curr->get_thread_operand();
1680 if (curr->get_type() == PTHREAD_CREATE) {
1681 return curr->get_thread_operand();
1686 /** @param act A read atomic action */
1687 bool ModelExecution::paused_by_fuzzer(const ModelAction * act) const
1689 ASSERT(act->is_read());
1691 // Actions paused by fuzzer have their sequence number reset to 0
1692 return act->get_seq_number() == 0;
1696 * Takes the next step in the execution, if possible.
1697 * @param curr The current step to take
1698 * @return Returns the next Thread to run, if any; NULL if this execution
1701 Thread * ModelExecution::take_step(ModelAction *curr)
1703 Thread *curr_thrd = get_thread(curr);
1704 ASSERT(curr_thrd->get_state() == THREAD_READY);
1706 ASSERT(check_action_enabled(curr)); /* May have side effects? */
1707 curr = check_current_action(curr);
1710 /* Process this action in ModelHistory for records */
1711 model->get_history()->process_action( curr, curr->get_tid() );
1713 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
1714 scheduler->remove_thread(curr_thrd);
1716 return action_select_next_thread(curr);
1719 Fuzzer * ModelExecution::getFuzzer() {