9 #include "snapshot-interface.h"
11 #include "clockvector.h"
12 #include "cyclegraph.h"
15 #include "threads-model.h"
18 #define INITIAL_THREAD_ID 0
23 bug_message(const char *str) {
24 const char *fmt = " [BUG] %s\n";
25 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
26 sprintf(msg, fmt, str);
28 ~bug_message() { if (msg) snapshot_free(msg); }
31 void print() { model_print("%s", msg); }
37 * Structure for holding small ModelChecker members that should be snapshotted
39 struct model_snapshot_members {
40 model_snapshot_members() :
42 /* First thread created will have id INITIAL_THREAD_ID */
43 next_thread_id(INITIAL_THREAD_ID),
44 used_sequence_numbers(0),
49 failed_promise(false),
50 too_many_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 ModelAction *current_action;
62 unsigned int next_thread_id;
63 modelclock_t used_sequence_numbers;
65 ModelAction *next_backtrack;
66 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
67 struct execution_stats stats;
70 /** @brief Incorrectly-ordered synchronization was made */
71 bool bad_synchronization;
77 /** @brief Constructor */
78 ModelChecker::ModelChecker(struct model_params params) :
79 /* Initialize default scheduler */
81 scheduler(new Scheduler()),
83 earliest_diverge(NULL),
84 action_trace(new action_list_t()),
85 thread_map(new HashTable<int, Thread *, int>()),
86 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
89 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
90 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
91 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
92 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
93 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
129 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr) {
130 action_list_t * tmp=hash->get(ptr);
132 tmp=new action_list_t();
138 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr) {
139 std::vector<action_list_t> * tmp=hash->get(ptr);
141 tmp=new std::vector<action_list_t>();
148 * Restores user program to initial state and resets all model-checker data
151 void ModelChecker::reset_to_initial_state()
153 DEBUG("+++ Resetting to initial state +++\n");
154 node_stack->reset_execution();
156 /* Print all model-checker output before rollback */
159 snapshotObject->backTrackBeforeStep(0);
162 /** @return a thread ID for a new Thread */
163 thread_id_t ModelChecker::get_next_id()
165 return priv->next_thread_id++;
168 /** @return the number of user threads created during this execution */
169 unsigned int ModelChecker::get_num_threads() const
171 return priv->next_thread_id;
174 /** @return The currently executing Thread. */
175 Thread * ModelChecker::get_current_thread()
177 return scheduler->get_current_thread();
180 /** @return a sequence number for a new ModelAction */
181 modelclock_t ModelChecker::get_next_seq_num()
183 return ++priv->used_sequence_numbers;
186 Node * ModelChecker::get_curr_node() {
187 return node_stack->get_head();
191 * @brief Choose the next thread to execute.
193 * This function chooses the next thread that should execute. It can force the
194 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
195 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
196 * The model-checker may have no preference regarding the next thread (i.e.,
197 * when exploring a new execution ordering), in which case this will return
199 * @param curr The current ModelAction. This action might guide the choice of
201 * @return The next thread to run. If the model-checker has no preference, NULL.
203 Thread * ModelChecker::get_next_thread(ModelAction *curr)
208 /* Do not split atomic actions. */
210 return thread_current();
211 /* The THREAD_CREATE action points to the created Thread */
212 else if (curr->get_type() == THREAD_CREATE)
213 return (Thread *)curr->get_location();
216 /* Have we completed exploring the preselected path? */
220 /* Else, we are trying to replay an execution */
221 ModelAction *next = node_stack->get_next()->get_action();
223 if (next == diverge) {
224 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
225 earliest_diverge=diverge;
227 Node *nextnode = next->get_node();
228 Node *prevnode = nextnode->get_parent();
229 scheduler->update_sleep_set(prevnode);
231 /* Reached divergence point */
232 if (nextnode->increment_misc()) {
233 /* The next node will try to satisfy a different misc_index values. */
234 tid = next->get_tid();
235 node_stack->pop_restofstack(2);
236 } else if (nextnode->increment_promise()) {
237 /* The next node will try to satisfy a different set of promises. */
238 tid = next->get_tid();
239 node_stack->pop_restofstack(2);
240 } else if (nextnode->increment_read_from()) {
241 /* The next node will read from a different value. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_future_value()) {
245 /* The next node will try to read from a different future value. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_relseq_break()) {
249 /* The next node will try to resolve a release sequence differently */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
253 /* Make a different thread execute for next step */
254 scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid())));
255 tid = prevnode->get_next_backtrack();
256 /* Make sure the backtracked thread isn't sleeping. */
257 node_stack->pop_restofstack(1);
258 if (diverge==earliest_diverge) {
259 earliest_diverge=prevnode->get_action();
262 /* The correct sleep set is in the parent node. */
265 DEBUG("*** Divergence point ***\n");
269 tid = next->get_tid();
271 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
272 ASSERT(tid != THREAD_ID_T_NONE);
273 return thread_map->get(id_to_int(tid));
277 * We need to know what the next actions of all threads in the sleep
278 * set will be. This method computes them and stores the actions at
279 * the corresponding thread object's pending action.
282 void ModelChecker::execute_sleep_set() {
283 for(unsigned int i=0;i<get_num_threads();i++) {
284 thread_id_t tid=int_to_id(i);
285 Thread *thr=get_thread(tid);
286 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET &&
287 thr->get_pending() == NULL ) {
288 thr->set_state(THREAD_RUNNING);
289 scheduler->next_thread(thr);
290 Thread::swap(&system_context, thr);
291 priv->current_action->set_sleep_flag();
292 thr->set_pending(priv->current_action);
295 priv->current_action = NULL;
298 void ModelChecker::wake_up_sleeping_actions(ModelAction * curr) {
299 for(unsigned int i=0;i<get_num_threads();i++) {
300 thread_id_t tid=int_to_id(i);
301 Thread *thr=get_thread(tid);
302 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
303 ModelAction *pending_act=thr->get_pending();
304 if ((!curr->is_rmwr())&&pending_act->could_synchronize_with(curr)) {
305 //Remove this thread from sleep set
306 scheduler->remove_sleep(thr);
312 /** @brief Alert the model-checker that an incorrectly-ordered
313 * synchronization was made */
314 void ModelChecker::set_bad_synchronization()
316 priv->bad_synchronization = true;
319 bool ModelChecker::has_asserted() const
321 return priv->asserted;
324 void ModelChecker::set_assert()
326 priv->asserted = true;
330 * Check if we are in a deadlock. Should only be called at the end of an
331 * execution, although it should not give false positives in the middle of an
332 * execution (there should be some ENABLED thread).
334 * @return True if program is in a deadlock; false otherwise
336 bool ModelChecker::is_deadlocked() const
338 bool blocking_threads = false;
339 for (unsigned int i = 0; i < get_num_threads(); i++) {
340 thread_id_t tid = int_to_id(i);
343 Thread *t = get_thread(tid);
344 if (!t->is_model_thread() && t->get_pending())
345 blocking_threads = true;
347 return blocking_threads;
351 * Check if this is a complete execution. That is, have all thread completed
352 * execution (rather than exiting because sleep sets have forced a redundant
355 * @return True if the execution is complete.
357 bool ModelChecker::is_complete_execution() const
359 for (unsigned int i = 0; i < get_num_threads(); i++)
360 if (is_enabled(int_to_id(i)))
366 * @brief Assert a bug in the executing program.
368 * Use this function to assert any sort of bug in the user program. If the
369 * current trace is feasible (actually, a prefix of some feasible execution),
370 * then this execution will be aborted, printing the appropriate message. If
371 * the current trace is not yet feasible, the error message will be stashed and
372 * printed if the execution ever becomes feasible.
374 * @param msg Descriptive message for the bug (do not include newline char)
375 * @return True if bug is immediately-feasible
377 bool ModelChecker::assert_bug(const char *msg)
379 priv->bugs.push_back(new bug_message(msg));
381 if (isfeasibleprefix()) {
389 * @brief Assert a bug in the executing program, asserted by a user thread
390 * @see ModelChecker::assert_bug
391 * @param msg Descriptive message for the bug (do not include newline char)
393 void ModelChecker::assert_user_bug(const char *msg)
395 /* If feasible bug, bail out now */
397 switch_to_master(NULL);
400 /** @return True, if any bugs have been reported for this execution */
401 bool ModelChecker::have_bug_reports() const
403 return priv->bugs.size() != 0;
406 /** @brief Print bug report listing for this execution (if any bugs exist) */
407 void ModelChecker::print_bugs() const
409 if (have_bug_reports()) {
410 model_print("Bug report: %zu bug%s detected\n",
412 priv->bugs.size() > 1 ? "s" : "");
413 for (unsigned int i = 0; i < priv->bugs.size(); i++)
414 priv->bugs[i]->print();
419 * @brief Record end-of-execution stats
421 * Must be run when exiting an execution. Records various stats.
422 * @see struct execution_stats
424 void ModelChecker::record_stats()
427 if (!isfeasibleprefix())
428 stats.num_infeasible++;
429 else if (have_bug_reports())
430 stats.num_buggy_executions++;
431 else if (is_complete_execution())
432 stats.num_complete++;
434 stats.num_redundant++;
437 /** @brief Print execution stats */
438 void ModelChecker::print_stats() const
440 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
441 model_print("Number of redundant executions: %d\n", stats.num_redundant);
442 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
443 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
444 model_print("Total executions: %d\n", stats.num_total);
445 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
449 * @brief End-of-exeuction print
450 * @param printbugs Should any existing bugs be printed?
452 void ModelChecker::print_execution(bool printbugs) const
454 print_program_output();
456 if (DBG_ENABLED() || params.verbose) {
457 model_print("Earliest divergence point since last feasible execution:\n");
458 if (earliest_diverge)
459 earliest_diverge->print();
461 model_print("(Not set)\n");
467 /* Don't print invalid bugs */
476 * Queries the model-checker for more executions to explore and, if one
477 * exists, resets the model-checker state to execute a new execution.
479 * @return If there are more executions to explore, return true. Otherwise,
482 bool ModelChecker::next_execution()
485 /* Is this execution a feasible execution that's worth bug-checking? */
486 bool complete = isfeasibleprefix() && (is_complete_execution() ||
489 /* End-of-execution bug checks */
492 assert_bug("Deadlock detected");
500 if (DBG_ENABLED() || params.verbose || have_bug_reports())
501 print_execution(complete);
503 clear_program_output();
506 earliest_diverge = NULL;
508 if ((diverge = get_next_backtrack()) == NULL)
512 model_print("Next execution will diverge at:\n");
516 reset_to_initial_state();
520 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
522 switch (act->get_type()) {
526 /* Optimization: relaxed operations don't need backtracking */
527 if (act->is_relaxed())
529 /* linear search: from most recent to oldest */
530 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
531 action_list_t::reverse_iterator rit;
532 for (rit = list->rbegin(); rit != list->rend(); rit++) {
533 ModelAction *prev = *rit;
534 if (prev->could_synchronize_with(act))
540 case ATOMIC_TRYLOCK: {
541 /* linear search: from most recent to oldest */
542 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
543 action_list_t::reverse_iterator rit;
544 for (rit = list->rbegin(); rit != list->rend(); rit++) {
545 ModelAction *prev = *rit;
546 if (act->is_conflicting_lock(prev))
551 case ATOMIC_UNLOCK: {
552 /* linear search: from most recent to oldest */
553 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
554 action_list_t::reverse_iterator rit;
555 for (rit = list->rbegin(); rit != list->rend(); rit++) {
556 ModelAction *prev = *rit;
557 if (!act->same_thread(prev)&&prev->is_failed_trylock())
563 /* linear search: from most recent to oldest */
564 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
565 action_list_t::reverse_iterator rit;
566 for (rit = list->rbegin(); rit != list->rend(); rit++) {
567 ModelAction *prev = *rit;
568 if (!act->same_thread(prev)&&prev->is_failed_trylock())
570 if (!act->same_thread(prev)&&prev->is_notify())
576 case ATOMIC_NOTIFY_ALL:
577 case ATOMIC_NOTIFY_ONE: {
578 /* linear search: from most recent to oldest */
579 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
580 action_list_t::reverse_iterator rit;
581 for (rit = list->rbegin(); rit != list->rend(); rit++) {
582 ModelAction *prev = *rit;
583 if (!act->same_thread(prev)&&prev->is_wait())
594 /** This method finds backtracking points where we should try to
595 * reorder the parameter ModelAction against.
597 * @param the ModelAction to find backtracking points for.
599 void ModelChecker::set_backtracking(ModelAction *act)
601 Thread *t = get_thread(act);
602 ModelAction * prev = get_last_conflict(act);
606 Node * node = prev->get_node()->get_parent();
608 int low_tid, high_tid;
609 if (node->is_enabled(t)) {
610 low_tid = id_to_int(act->get_tid());
611 high_tid = low_tid+1;
614 high_tid = get_num_threads();
617 for(int i = low_tid; i < high_tid; i++) {
618 thread_id_t tid = int_to_id(i);
620 /* Make sure this thread can be enabled here. */
621 if (i >= node->get_num_threads())
624 /* Don't backtrack into a point where the thread is disabled or sleeping. */
625 if (node->enabled_status(tid)!=THREAD_ENABLED)
628 /* Check if this has been explored already */
629 if (node->has_been_explored(tid))
632 /* See if fairness allows */
633 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
635 for(int t=0;t<node->get_num_threads();t++) {
636 thread_id_t tother=int_to_id(t);
637 if (node->is_enabled(tother) && node->has_priority(tother)) {
645 /* Cache the latest backtracking point */
646 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
647 priv->next_backtrack = prev;
649 /* If this is a new backtracking point, mark the tree */
650 if (!node->set_backtrack(tid))
652 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
653 id_to_int(prev->get_tid()),
654 id_to_int(t->get_id()));
663 * Returns last backtracking point. The model checker will explore a different
664 * path for this point in the next execution.
665 * @return The ModelAction at which the next execution should diverge.
667 ModelAction * ModelChecker::get_next_backtrack()
669 ModelAction *next = priv->next_backtrack;
670 priv->next_backtrack = NULL;
675 * Processes a read or rmw model action.
676 * @param curr is the read model action to process.
677 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
678 * @return True if processing this read updates the mo_graph.
680 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
682 uint64_t value = VALUE_NONE;
683 bool updated = false;
685 const ModelAction *reads_from = curr->get_node()->get_read_from();
686 if (reads_from != NULL) {
687 mo_graph->startChanges();
689 value = reads_from->get_value();
690 bool r_status = false;
692 if (!second_part_of_rmw) {
693 check_recency(curr, reads_from);
694 r_status = r_modification_order(curr, reads_from);
698 if (!second_part_of_rmw&&is_infeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
699 mo_graph->rollbackChanges();
700 priv->too_many_reads = false;
704 curr->read_from(reads_from);
705 mo_graph->commitChanges();
706 mo_check_promises(curr->get_tid(), reads_from);
709 } else if (!second_part_of_rmw) {
710 /* Read from future value */
711 value = curr->get_node()->get_future_value();
712 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
713 curr->read_from(NULL);
714 Promise *valuepromise = new Promise(curr, value, expiration);
715 promises->push_back(valuepromise);
717 get_thread(curr)->set_return_value(value);
723 * Processes a lock, trylock, or unlock model action. @param curr is
724 * the read model action to process.
726 * The try lock operation checks whether the lock is taken. If not,
727 * it falls to the normal lock operation case. If so, it returns
730 * The lock operation has already been checked that it is enabled, so
731 * it just grabs the lock and synchronizes with the previous unlock.
733 * The unlock operation has to re-enable all of the threads that are
734 * waiting on the lock.
736 * @return True if synchronization was updated; false otherwise
738 bool ModelChecker::process_mutex(ModelAction *curr) {
739 std::mutex *mutex=NULL;
740 struct std::mutex_state *state=NULL;
742 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
743 mutex = (std::mutex *)curr->get_location();
744 state = mutex->get_state();
745 } else if(curr->is_wait()) {
746 mutex = (std::mutex *)curr->get_value();
747 state = mutex->get_state();
750 switch (curr->get_type()) {
751 case ATOMIC_TRYLOCK: {
752 bool success = !state->islocked;
753 curr->set_try_lock(success);
755 get_thread(curr)->set_return_value(0);
758 get_thread(curr)->set_return_value(1);
760 //otherwise fall into the lock case
762 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
763 assert_bug("Lock access before initialization");
764 state->islocked = true;
765 ModelAction *unlock = get_last_unlock(curr);
766 //synchronize with the previous unlock statement
767 if (unlock != NULL) {
768 curr->synchronize_with(unlock);
773 case ATOMIC_UNLOCK: {
775 state->islocked = false;
776 //wake up the other threads
777 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
778 //activate all the waiting threads
779 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
780 scheduler->wake(get_thread(*rit));
787 state->islocked = false;
788 //wake up the other threads
789 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
790 //activate all the waiting threads
791 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
792 scheduler->wake(get_thread(*rit));
795 //check whether we should go to sleep or not...simulate spurious failures
796 if (curr->get_node()->get_misc()==0) {
797 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
799 scheduler->sleep(get_current_thread());
803 case ATOMIC_NOTIFY_ALL: {
804 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
805 //activate all the waiting threads
806 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
807 scheduler->wake(get_thread(*rit));
812 case ATOMIC_NOTIFY_ONE: {
813 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
814 int wakeupthread=curr->get_node()->get_misc();
815 action_list_t::iterator it = waiters->begin();
816 advance(it, wakeupthread);
817 scheduler->wake(get_thread(*it));
829 * Process a write ModelAction
830 * @param curr The ModelAction to process
831 * @return True if the mo_graph was updated or promises were resolved
833 bool ModelChecker::process_write(ModelAction *curr)
835 bool updated_mod_order = w_modification_order(curr);
836 bool updated_promises = resolve_promises(curr);
838 if (promises->size() == 0) {
839 for (unsigned int i = 0; i < futurevalues->size(); i++) {
840 struct PendingFutureValue pfv = (*futurevalues)[i];
841 //Do more ambitious checks now that mo is more complete
842 if (mo_may_allow(pfv.writer, pfv.act)&&
843 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number()+params.maxfuturedelay) &&
844 (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
845 priv->next_backtrack = pfv.act;
847 futurevalues->resize(0);
850 mo_graph->commitChanges();
851 mo_check_promises(curr->get_tid(), curr);
853 get_thread(curr)->set_return_value(VALUE_NONE);
854 return updated_mod_order || updated_promises;
858 * @brief Process the current action for thread-related activity
860 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
861 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
862 * synchronization, etc. This function is a no-op for non-THREAD actions
863 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
865 * @param curr The current action
866 * @return True if synchronization was updated or a thread completed
868 bool ModelChecker::process_thread_action(ModelAction *curr)
870 bool updated = false;
872 switch (curr->get_type()) {
873 case THREAD_CREATE: {
874 Thread *th = (Thread *)curr->get_location();
875 th->set_creation(curr);
879 Thread *blocking = (Thread *)curr->get_location();
880 ModelAction *act = get_last_action(blocking->get_id());
881 curr->synchronize_with(act);
882 updated = true; /* trigger rel-seq checks */
885 case THREAD_FINISH: {
886 Thread *th = get_thread(curr);
887 while (!th->wait_list_empty()) {
888 ModelAction *act = th->pop_wait_list();
889 scheduler->wake(get_thread(act));
892 updated = true; /* trigger rel-seq checks */
896 check_promises(curr->get_tid(), NULL, curr->get_cv());
907 * @brief Process the current action for release sequence fixup activity
909 * Performs model-checker release sequence fixups for the current action,
910 * forcing a single pending release sequence to break (with a given, potential
911 * "loose" write) or to complete (i.e., synchronize). If a pending release
912 * sequence forms a complete release sequence, then we must perform the fixup
913 * synchronization, mo_graph additions, etc.
915 * @param curr The current action; must be a release sequence fixup action
916 * @param work_queue The work queue to which to add work items as they are
919 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
921 const ModelAction *write = curr->get_node()->get_relseq_break();
922 struct release_seq *sequence = pending_rel_seqs->back();
923 pending_rel_seqs->pop_back();
925 ModelAction *acquire = sequence->acquire;
926 const ModelAction *rf = sequence->rf;
927 const ModelAction *release = sequence->release;
931 ASSERT(release->same_thread(rf));
935 * @todo Forcing a synchronization requires that we set
936 * modification order constraints. For instance, we can't allow
937 * a fixup sequence in which two separate read-acquire
938 * operations read from the same sequence, where the first one
939 * synchronizes and the other doesn't. Essentially, we can't
940 * allow any writes to insert themselves between 'release' and
944 /* Must synchronize */
945 if (!acquire->synchronize_with(release)) {
946 set_bad_synchronization();
949 /* Re-check all pending release sequences */
950 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
951 /* Re-check act for mo_graph edges */
952 work_queue->push_back(MOEdgeWorkEntry(acquire));
954 /* propagate synchronization to later actions */
955 action_list_t::reverse_iterator rit = action_trace->rbegin();
956 for (; (*rit) != acquire; rit++) {
957 ModelAction *propagate = *rit;
958 if (acquire->happens_before(propagate)) {
959 propagate->synchronize_with(acquire);
960 /* Re-check 'propagate' for mo_graph edges */
961 work_queue->push_back(MOEdgeWorkEntry(propagate));
965 /* Break release sequence with new edges:
966 * release --mo--> write --mo--> rf */
967 mo_graph->addEdge(release, write);
968 mo_graph->addEdge(write, rf);
971 /* See if we have realized a data race */
976 * Initialize the current action by performing one or more of the following
977 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
978 * in the NodeStack, manipulating backtracking sets, allocating and
979 * initializing clock vectors, and computing the promises to fulfill.
981 * @param curr The current action, as passed from the user context; may be
982 * freed/invalidated after the execution of this function, with a different
983 * action "returned" its place (pass-by-reference)
984 * @return True if curr is a newly-explored action; false otherwise
986 bool ModelChecker::initialize_curr_action(ModelAction **curr)
988 ModelAction *newcurr;
990 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
991 newcurr = process_rmw(*curr);
994 if (newcurr->is_rmw())
995 compute_promises(newcurr);
1001 (*curr)->set_seq_number(get_next_seq_num());
1003 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled());
1005 /* First restore type and order in case of RMW operation */
1006 if ((*curr)->is_rmwr())
1007 newcurr->copy_typeandorder(*curr);
1009 ASSERT((*curr)->get_location() == newcurr->get_location());
1010 newcurr->copy_from_new(*curr);
1012 /* Discard duplicate ModelAction; use action from NodeStack */
1015 /* Always compute new clock vector */
1016 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1019 return false; /* Action was explored previously */
1023 /* Always compute new clock vector */
1024 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1026 * Perform one-time actions when pushing new ModelAction onto
1029 if (newcurr->is_write())
1030 compute_promises(newcurr);
1031 else if (newcurr->is_relseq_fixup())
1032 compute_relseq_breakwrites(newcurr);
1033 else if (newcurr->is_wait())
1034 newcurr->get_node()->set_misc_max(2);
1035 else if (newcurr->is_notify_one()) {
1036 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1038 return true; /* This was a new ModelAction */
1043 * @brief Check whether a model action is enabled.
1045 * Checks whether a lock or join operation would be successful (i.e., is the
1046 * lock already locked, or is the joined thread already complete). If not, put
1047 * the action in a waiter list.
1049 * @param curr is the ModelAction to check whether it is enabled.
1050 * @return a bool that indicates whether the action is enabled.
1052 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1053 if (curr->is_lock()) {
1054 std::mutex * lock = (std::mutex *)curr->get_location();
1055 struct std::mutex_state * state = lock->get_state();
1056 if (state->islocked) {
1057 //Stick the action in the appropriate waiting queue
1058 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1061 } else if (curr->get_type() == THREAD_JOIN) {
1062 Thread *blocking = (Thread *)curr->get_location();
1063 if (!blocking->is_complete()) {
1064 blocking->push_wait_list(curr);
1073 * Stores the ModelAction for the current thread action. Call this
1074 * immediately before switching from user- to system-context to pass
1075 * data between them.
1076 * @param act The ModelAction created by the user-thread action
1078 void ModelChecker::set_current_action(ModelAction *act) {
1079 priv->current_action = act;
1083 * This is the heart of the model checker routine. It performs model-checking
1084 * actions corresponding to a given "current action." Among other processes, it
1085 * calculates reads-from relationships, updates synchronization clock vectors,
1086 * forms a memory_order constraints graph, and handles replay/backtrack
1087 * execution when running permutations of previously-observed executions.
1089 * @param curr The current action to process
1090 * @return The next Thread that must be executed. May be NULL if ModelChecker
1091 * makes no choice (e.g., according to replay execution, combining RMW actions,
1094 Thread * ModelChecker::check_current_action(ModelAction *curr)
1097 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1099 if (!check_action_enabled(curr)) {
1100 /* Make the execution look like we chose to run this action
1101 * much later, when a lock/join can succeed */
1102 get_current_thread()->set_pending(curr);
1103 scheduler->sleep(get_current_thread());
1104 return get_next_thread(NULL);
1107 bool newly_explored = initialize_curr_action(&curr);
1109 wake_up_sleeping_actions(curr);
1111 /* Add the action to lists before any other model-checking tasks */
1112 if (!second_part_of_rmw)
1113 add_action_to_lists(curr);
1115 /* Build may_read_from set for newly-created actions */
1116 if (newly_explored && curr->is_read())
1117 build_reads_from_past(curr);
1119 /* Initialize work_queue with the "current action" work */
1120 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1121 while (!work_queue.empty() && !has_asserted()) {
1122 WorkQueueEntry work = work_queue.front();
1123 work_queue.pop_front();
1125 switch (work.type) {
1126 case WORK_CHECK_CURR_ACTION: {
1127 ModelAction *act = work.action;
1128 bool update = false; /* update this location's release seq's */
1129 bool update_all = false; /* update all release seq's */
1131 if (process_thread_action(curr))
1134 if (act->is_read() && process_read(act, second_part_of_rmw))
1137 if (act->is_write() && process_write(act))
1140 if (act->is_mutex_op() && process_mutex(act))
1143 if (act->is_relseq_fixup())
1144 process_relseq_fixup(curr, &work_queue);
1147 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1149 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1152 case WORK_CHECK_RELEASE_SEQ:
1153 resolve_release_sequences(work.location, &work_queue);
1155 case WORK_CHECK_MO_EDGES: {
1156 /** @todo Complete verification of work_queue */
1157 ModelAction *act = work.action;
1158 bool updated = false;
1160 if (act->is_read()) {
1161 const ModelAction *rf = act->get_reads_from();
1162 if (rf != NULL && r_modification_order(act, rf))
1165 if (act->is_write()) {
1166 if (w_modification_order(act))
1169 mo_graph->commitChanges();
1172 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1181 check_curr_backtracking(curr);
1182 set_backtracking(curr);
1183 return get_next_thread(curr);
1186 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
1187 Node *currnode = curr->get_node();
1188 Node *parnode = currnode->get_parent();
1190 if ((!parnode->backtrack_empty() ||
1191 !currnode->misc_empty() ||
1192 !currnode->read_from_empty() ||
1193 !currnode->future_value_empty() ||
1194 !currnode->promise_empty() ||
1195 !currnode->relseq_break_empty())
1196 && (!priv->next_backtrack ||
1197 *curr > *priv->next_backtrack)) {
1198 priv->next_backtrack = curr;
1202 bool ModelChecker::promises_expired() const
1204 for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
1205 Promise *promise = (*promises)[promise_index];
1206 if (promise->get_expiration()<priv->used_sequence_numbers) {
1214 * This is the strongest feasibility check available.
1215 * @return whether the current trace (partial or complete) must be a prefix of
1218 bool ModelChecker::isfeasibleprefix() const
1220 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1224 * Returns whether the current completed trace is feasible, except for pending
1225 * release sequences.
1227 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1229 if (DBG_ENABLED() && promises->size() != 0)
1230 DEBUG("Infeasible: unrevolved promises\n");
1232 return !is_infeasible() && promises->size() == 0;
1236 * Check if the current partial trace is infeasible. Does not check any
1237 * end-of-execution flags, which might rule out the execution. Thus, this is
1238 * useful only for ruling an execution as infeasible.
1239 * @return whether the current partial trace is infeasible.
1241 bool ModelChecker::is_infeasible() const
1243 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1244 DEBUG("Infeasible: RMW violation\n");
1246 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1250 * Check If the current partial trace is infeasible, while ignoring
1251 * infeasibility related to 2 RMW's reading from the same store. It does not
1252 * check end-of-execution feasibility.
1253 * @see ModelChecker::is_infeasible
1254 * @return whether the current partial trace is infeasible, ignoring multiple
1255 * RMWs reading from the same store.
1257 bool ModelChecker::is_infeasible_ignoreRMW() const
1259 if (DBG_ENABLED()) {
1260 if (mo_graph->checkForCycles())
1261 DEBUG("Infeasible: modification order cycles\n");
1262 if (priv->failed_promise)
1263 DEBUG("Infeasible: failed promise\n");
1264 if (priv->too_many_reads)
1265 DEBUG("Infeasible: too many reads\n");
1266 if (priv->bad_synchronization)
1267 DEBUG("Infeasible: bad synchronization ordering\n");
1268 if (promises_expired())
1269 DEBUG("Infeasible: promises expired\n");
1271 return mo_graph->checkForCycles() || priv->failed_promise ||
1272 priv->too_many_reads || priv->bad_synchronization ||
1276 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1277 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1278 ModelAction *lastread = get_last_action(act->get_tid());
1279 lastread->process_rmw(act);
1280 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1281 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1282 mo_graph->commitChanges();
1288 * Checks whether a thread has read from the same write for too many times
1289 * without seeing the effects of a later write.
1292 * 1) there must a different write that we could read from that would satisfy the modification order,
1293 * 2) we must have read from the same value in excess of maxreads times, and
1294 * 3) that other write must have been in the reads_from set for maxreads times.
1296 * If so, we decide that the execution is no longer feasible.
1298 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1299 if (params.maxreads != 0) {
1301 if (curr->get_node()->get_read_from_size() <= 1)
1303 //Must make sure that execution is currently feasible... We could
1304 //accidentally clear by rolling back
1305 if (is_infeasible())
1307 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1308 int tid = id_to_int(curr->get_tid());
1311 if ((int)thrd_lists->size() <= tid)
1313 action_list_t *list = &(*thrd_lists)[tid];
1315 action_list_t::reverse_iterator rit = list->rbegin();
1316 /* Skip past curr */
1317 for (; (*rit) != curr; rit++)
1319 /* go past curr now */
1322 action_list_t::reverse_iterator ritcopy = rit;
1323 //See if we have enough reads from the same value
1325 for (; count < params.maxreads; rit++,count++) {
1326 if (rit==list->rend())
1328 ModelAction *act = *rit;
1329 if (!act->is_read())
1332 if (act->get_reads_from() != rf)
1334 if (act->get_node()->get_read_from_size() <= 1)
1337 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1339 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1341 //Need a different write
1345 /* Test to see whether this is a feasible write to read from*/
1346 mo_graph->startChanges();
1347 r_modification_order(curr, write);
1348 bool feasiblereadfrom = !is_infeasible();
1349 mo_graph->rollbackChanges();
1351 if (!feasiblereadfrom)
1355 bool feasiblewrite = true;
1356 //new we need to see if this write works for everyone
1358 for (int loop = count; loop>0; loop--,rit++) {
1359 ModelAction *act=*rit;
1360 bool foundvalue = false;
1361 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1362 if (act->get_node()->get_read_from_at(j)==write) {
1368 feasiblewrite = false;
1372 if (feasiblewrite) {
1373 priv->too_many_reads = true;
1381 * Updates the mo_graph with the constraints imposed from the current
1384 * Basic idea is the following: Go through each other thread and find
1385 * the lastest action that happened before our read. Two cases:
1387 * (1) The action is a write => that write must either occur before
1388 * the write we read from or be the write we read from.
1390 * (2) The action is a read => the write that that action read from
1391 * must occur before the write we read from or be the same write.
1393 * @param curr The current action. Must be a read.
1394 * @param rf The action that curr reads from. Must be a write.
1395 * @return True if modification order edges were added; false otherwise
1397 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1399 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1402 ASSERT(curr->is_read());
1404 /* Iterate over all threads */
1405 for (i = 0; i < thrd_lists->size(); i++) {
1406 /* Iterate over actions in thread, starting from most recent */
1407 action_list_t *list = &(*thrd_lists)[i];
1408 action_list_t::reverse_iterator rit;
1409 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1410 ModelAction *act = *rit;
1413 * Include at most one act per-thread that "happens
1414 * before" curr. Don't consider reflexively.
1416 if (act->happens_before(curr) && act != curr) {
1417 if (act->is_write()) {
1419 mo_graph->addEdge(act, rf);
1423 const ModelAction *prevreadfrom = act->get_reads_from();
1424 //if the previous read is unresolved, keep going...
1425 if (prevreadfrom == NULL)
1428 if (rf != prevreadfrom) {
1429 mo_graph->addEdge(prevreadfrom, rf);
1441 /** This method fixes up the modification order when we resolve a
1442 * promises. The basic problem is that actions that occur after the
1443 * read curr could not property add items to the modification order
1446 * So for each thread, we find the earliest item that happens after
1447 * the read curr. This is the item we have to fix up with additional
1448 * constraints. If that action is write, we add a MO edge between
1449 * the Action rf and that action. If the action is a read, we add a
1450 * MO edge between the Action rf, and whatever the read accessed.
1452 * @param curr is the read ModelAction that we are fixing up MO edges for.
1453 * @param rf is the write ModelAction that curr reads from.
1456 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1458 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1460 ASSERT(curr->is_read());
1462 /* Iterate over all threads */
1463 for (i = 0; i < thrd_lists->size(); i++) {
1464 /* Iterate over actions in thread, starting from most recent */
1465 action_list_t *list = &(*thrd_lists)[i];
1466 action_list_t::reverse_iterator rit;
1467 ModelAction *lastact = NULL;
1469 /* Find last action that happens after curr that is either not curr or a rmw */
1470 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1471 ModelAction *act = *rit;
1472 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1478 /* Include at most one act per-thread that "happens before" curr */
1479 if (lastact != NULL) {
1480 if (lastact==curr) {
1481 //Case 1: The resolved read is a RMW, and we need to make sure
1482 //that the write portion of the RMW mod order after rf
1484 mo_graph->addEdge(rf, lastact);
1485 } else if (lastact->is_read()) {
1486 //Case 2: The resolved read is a normal read and the next
1487 //operation is a read, and we need to make sure the value read
1488 //is mod ordered after rf
1490 const ModelAction *postreadfrom = lastact->get_reads_from();
1491 if (postreadfrom != NULL&&rf != postreadfrom)
1492 mo_graph->addEdge(rf, postreadfrom);
1494 //Case 3: The resolved read is a normal read and the next
1495 //operation is a write, and we need to make sure that the
1496 //write is mod ordered after rf
1498 mo_graph->addEdge(rf, lastact);
1506 * Updates the mo_graph with the constraints imposed from the current write.
1508 * Basic idea is the following: Go through each other thread and find
1509 * the lastest action that happened before our write. Two cases:
1511 * (1) The action is a write => that write must occur before
1514 * (2) The action is a read => the write that that action read from
1515 * must occur before the current write.
1517 * This method also handles two other issues:
1519 * (I) Sequential Consistency: Making sure that if the current write is
1520 * seq_cst, that it occurs after the previous seq_cst write.
1522 * (II) Sending the write back to non-synchronizing reads.
1524 * @param curr The current action. Must be a write.
1525 * @return True if modification order edges were added; false otherwise
1527 bool ModelChecker::w_modification_order(ModelAction *curr)
1529 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1532 ASSERT(curr->is_write());
1534 if (curr->is_seqcst()) {
1535 /* We have to at least see the last sequentially consistent write,
1536 so we are initialized. */
1537 ModelAction *last_seq_cst = get_last_seq_cst(curr);
1538 if (last_seq_cst != NULL) {
1539 mo_graph->addEdge(last_seq_cst, curr);
1544 /* Iterate over all threads */
1545 for (i = 0; i < thrd_lists->size(); i++) {
1546 /* Iterate over actions in thread, starting from most recent */
1547 action_list_t *list = &(*thrd_lists)[i];
1548 action_list_t::reverse_iterator rit;
1549 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1550 ModelAction *act = *rit;
1553 * 1) If RMW and it actually read from something, then we
1554 * already have all relevant edges, so just skip to next
1557 * 2) If RMW and it didn't read from anything, we should
1558 * whatever edge we can get to speed up convergence.
1560 * 3) If normal write, we need to look at earlier actions, so
1561 * continue processing list.
1563 if (curr->is_rmw()) {
1564 if (curr->get_reads_from()!=NULL)
1573 * Include at most one act per-thread that "happens
1576 if (act->happens_before(curr)) {
1578 * Note: if act is RMW, just add edge:
1580 * The following edge should be handled elsewhere:
1581 * readfrom(act) --mo--> act
1583 if (act->is_write())
1584 mo_graph->addEdge(act, curr);
1585 else if (act->is_read()) {
1586 //if previous read accessed a null, just keep going
1587 if (act->get_reads_from() == NULL)
1589 mo_graph->addEdge(act->get_reads_from(), curr);
1593 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1594 !act->same_thread(curr)) {
1595 /* We have an action that:
1596 (1) did not happen before us
1597 (2) is a read and we are a write
1598 (3) cannot synchronize with us
1599 (4) is in a different thread
1601 that read could potentially read from our write. Note that
1602 these checks are overly conservative at this point, we'll
1603 do more checks before actually removing the
1607 if (thin_air_constraint_may_allow(curr, act)) {
1608 if (!is_infeasible() ||
1609 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1610 struct PendingFutureValue pfv = {curr,act};
1611 futurevalues->push_back(pfv);
1621 /** Arbitrary reads from the future are not allowed. Section 29.3
1622 * part 9 places some constraints. This method checks one result of constraint
1623 * constraint. Others require compiler support. */
1624 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1625 if (!writer->is_rmw())
1628 if (!reader->is_rmw())
1631 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1632 if (search == reader)
1634 if (search->get_tid() == reader->get_tid() &&
1635 search->happens_before(reader))
1643 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1644 * some constraints. This method checks one the following constraint (others
1645 * require compiler support):
1647 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1649 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1651 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1653 /* Iterate over all threads */
1654 for (i = 0; i < thrd_lists->size(); i++) {
1655 const ModelAction *write_after_read = NULL;
1657 /* Iterate over actions in thread, starting from most recent */
1658 action_list_t *list = &(*thrd_lists)[i];
1659 action_list_t::reverse_iterator rit;
1660 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1661 ModelAction *act = *rit;
1663 if (!reader->happens_before(act))
1665 else if (act->is_write())
1666 write_after_read = act;
1667 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1668 write_after_read = act->get_reads_from();
1672 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1679 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1680 * The ModelAction under consideration is expected to be taking part in
1681 * release/acquire synchronization as an object of the "reads from" relation.
1682 * Note that this can only provide release sequence support for RMW chains
1683 * which do not read from the future, as those actions cannot be traced until
1684 * their "promise" is fulfilled. Similarly, we may not even establish the
1685 * presence of a release sequence with certainty, as some modification order
1686 * constraints may be decided further in the future. Thus, this function
1687 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1688 * and a boolean representing certainty.
1690 * @param rf The action that might be part of a release sequence. Must be a
1692 * @param release_heads A pass-by-reference style return parameter. After
1693 * execution of this function, release_heads will contain the heads of all the
1694 * relevant release sequences, if any exists with certainty
1695 * @param pending A pass-by-reference style return parameter which is only used
1696 * when returning false (i.e., uncertain). Returns most information regarding
1697 * an uncertain release sequence, including any write operations that might
1698 * break the sequence.
1699 * @return true, if the ModelChecker is certain that release_heads is complete;
1702 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1703 rel_heads_list_t *release_heads,
1704 struct release_seq *pending) const
1706 /* Only check for release sequences if there are no cycles */
1707 if (mo_graph->checkForCycles())
1711 ASSERT(rf->is_write());
1713 if (rf->is_release())
1714 release_heads->push_back(rf);
1716 break; /* End of RMW chain */
1718 /** @todo Need to be smarter here... In the linux lock
1719 * example, this will run to the beginning of the program for
1721 /** @todo The way to be smarter here is to keep going until 1
1722 * thread has a release preceded by an acquire and you've seen
1725 /* acq_rel RMW is a sufficient stopping condition */
1726 if (rf->is_acquire() && rf->is_release())
1727 return true; /* complete */
1729 rf = rf->get_reads_from();
1732 /* read from future: need to settle this later */
1734 return false; /* incomplete */
1737 if (rf->is_release())
1738 return true; /* complete */
1740 /* else relaxed write; check modification order for contiguous subsequence
1741 * -> rf must be same thread as release */
1742 int tid = id_to_int(rf->get_tid());
1743 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1744 action_list_t *list = &(*thrd_lists)[tid];
1745 action_list_t::const_reverse_iterator rit;
1747 /* Find rf in the thread list */
1748 rit = std::find(list->rbegin(), list->rend(), rf);
1749 ASSERT(rit != list->rend());
1751 /* Find the last write/release */
1752 for (; rit != list->rend(); rit++)
1753 if ((*rit)->is_release())
1755 if (rit == list->rend()) {
1756 /* No write-release in this thread */
1757 return true; /* complete */
1759 ModelAction *release = *rit;
1761 ASSERT(rf->same_thread(release));
1763 pending->writes.clear();
1765 bool certain = true;
1766 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1767 if (id_to_int(rf->get_tid()) == (int)i)
1769 list = &(*thrd_lists)[i];
1771 /* Can we ensure no future writes from this thread may break
1772 * the release seq? */
1773 bool future_ordered = false;
1775 ModelAction *last = get_last_action(int_to_id(i));
1776 Thread *th = get_thread(int_to_id(i));
1777 if ((last && rf->happens_before(last)) ||
1780 future_ordered = true;
1782 ASSERT(!th->is_model_thread() || future_ordered);
1784 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1785 const ModelAction *act = *rit;
1786 /* Reach synchronization -> this thread is complete */
1787 if (act->happens_before(release))
1789 if (rf->happens_before(act)) {
1790 future_ordered = true;
1794 /* Only non-RMW writes can break release sequences */
1795 if (!act->is_write() || act->is_rmw())
1798 /* Check modification order */
1799 if (mo_graph->checkReachable(rf, act)) {
1800 /* rf --mo--> act */
1801 future_ordered = true;
1804 if (mo_graph->checkReachable(act, release))
1805 /* act --mo--> release */
1807 if (mo_graph->checkReachable(release, act) &&
1808 mo_graph->checkReachable(act, rf)) {
1809 /* release --mo-> act --mo--> rf */
1810 return true; /* complete */
1812 /* act may break release sequence */
1813 pending->writes.push_back(act);
1816 if (!future_ordered)
1817 certain = false; /* This thread is uncertain */
1821 release_heads->push_back(release);
1822 pending->writes.clear();
1824 pending->release = release;
1831 * A public interface for getting the release sequence head(s) with which a
1832 * given ModelAction must synchronize. This function only returns a non-empty
1833 * result when it can locate a release sequence head with certainty. Otherwise,
1834 * it may mark the internal state of the ModelChecker so that it will handle
1835 * the release sequence at a later time, causing @a act to update its
1836 * synchronization at some later point in execution.
1837 * @param act The 'acquire' action that may read from a release sequence
1838 * @param release_heads A pass-by-reference return parameter. Will be filled
1839 * with the head(s) of the release sequence(s), if they exists with certainty.
1840 * @see ModelChecker::release_seq_heads
1842 void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
1844 const ModelAction *rf = act->get_reads_from();
1845 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
1846 sequence->acquire = act;
1848 if (!release_seq_heads(rf, release_heads, sequence)) {
1849 /* add act to 'lazy checking' list */
1850 pending_rel_seqs->push_back(sequence);
1852 snapshot_free(sequence);
1857 * Attempt to resolve all stashed operations that might synchronize with a
1858 * release sequence for a given location. This implements the "lazy" portion of
1859 * determining whether or not a release sequence was contiguous, since not all
1860 * modification order information is present at the time an action occurs.
1862 * @param location The location/object that should be checked for release
1863 * sequence resolutions. A NULL value means to check all locations.
1864 * @param work_queue The work queue to which to add work items as they are
1866 * @return True if any updates occurred (new synchronization, new mo_graph
1869 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
1871 bool updated = false;
1872 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
1873 while (it != pending_rel_seqs->end()) {
1874 struct release_seq *pending = *it;
1875 ModelAction *act = pending->acquire;
1877 /* Only resolve sequences on the given location, if provided */
1878 if (location && act->get_location() != location) {
1883 const ModelAction *rf = act->get_reads_from();
1884 rel_heads_list_t release_heads;
1886 complete = release_seq_heads(rf, &release_heads, pending);
1887 for (unsigned int i = 0; i < release_heads.size(); i++) {
1888 if (!act->has_synchronized_with(release_heads[i])) {
1889 if (act->synchronize_with(release_heads[i]))
1892 set_bad_synchronization();
1897 /* Re-check all pending release sequences */
1898 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1899 /* Re-check act for mo_graph edges */
1900 work_queue->push_back(MOEdgeWorkEntry(act));
1902 /* propagate synchronization to later actions */
1903 action_list_t::reverse_iterator rit = action_trace->rbegin();
1904 for (; (*rit) != act; rit++) {
1905 ModelAction *propagate = *rit;
1906 if (act->happens_before(propagate)) {
1907 propagate->synchronize_with(act);
1908 /* Re-check 'propagate' for mo_graph edges */
1909 work_queue->push_back(MOEdgeWorkEntry(propagate));
1914 it = pending_rel_seqs->erase(it);
1915 snapshot_free(pending);
1921 // If we resolved promises or data races, see if we have realized a data race.
1928 * Performs various bookkeeping operations for the current ModelAction. For
1929 * instance, adds action to the per-object, per-thread action vector and to the
1930 * action trace list of all thread actions.
1932 * @param act is the ModelAction to add.
1934 void ModelChecker::add_action_to_lists(ModelAction *act)
1936 int tid = id_to_int(act->get_tid());
1937 action_trace->push_back(act);
1939 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
1941 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
1942 if (tid >= (int)vec->size())
1943 vec->resize(priv->next_thread_id);
1944 (*vec)[tid].push_back(act);
1946 if ((int)thrd_last_action->size() <= tid)
1947 thrd_last_action->resize(get_num_threads());
1948 (*thrd_last_action)[tid] = act;
1950 if (act->is_wait()) {
1951 void *mutex_loc=(void *) act->get_value();
1952 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
1954 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
1955 if (tid >= (int)vec->size())
1956 vec->resize(priv->next_thread_id);
1957 (*vec)[tid].push_back(act);
1959 if ((int)thrd_last_action->size() <= tid)
1960 thrd_last_action->resize(get_num_threads());
1961 (*thrd_last_action)[tid] = act;
1966 * @brief Get the last action performed by a particular Thread
1967 * @param tid The thread ID of the Thread in question
1968 * @return The last action in the thread
1970 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
1972 int threadid = id_to_int(tid);
1973 if (threadid < (int)thrd_last_action->size())
1974 return (*thrd_last_action)[id_to_int(tid)];
1980 * Gets the last memory_order_seq_cst write (in the total global sequence)
1981 * performed on a particular object (i.e., memory location), not including the
1983 * @param curr The current ModelAction; also denotes the object location to
1985 * @return The last seq_cst write
1987 ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const
1989 void *location = curr->get_location();
1990 action_list_t *list = get_safe_ptr_action(obj_map, location);
1991 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1992 action_list_t::reverse_iterator rit;
1993 for (rit = list->rbegin(); rit != list->rend(); rit++)
1994 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2000 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2001 * location). This function identifies the mutex according to the current
2002 * action, which is presumed to perform on the same mutex.
2003 * @param curr The current ModelAction; also denotes the object location to
2005 * @return The last unlock operation
2007 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2009 void *location = curr->get_location();
2010 action_list_t *list = get_safe_ptr_action(obj_map, location);
2011 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2012 action_list_t::reverse_iterator rit;
2013 for (rit = list->rbegin(); rit != list->rend(); rit++)
2014 if ((*rit)->is_unlock() || (*rit)->is_wait())
2019 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
2021 ModelAction *parent = get_last_action(tid);
2023 parent = get_thread(tid)->get_creation();
2028 * Returns the clock vector for a given thread.
2029 * @param tid The thread whose clock vector we want
2030 * @return Desired clock vector
2032 ClockVector * ModelChecker::get_cv(thread_id_t tid)
2034 return get_parent_action(tid)->get_cv();
2038 * Resolve a set of Promises with a current write. The set is provided in the
2039 * Node corresponding to @a write.
2040 * @param write The ModelAction that is fulfilling Promises
2041 * @return True if promises were resolved; false otherwise
2043 bool ModelChecker::resolve_promises(ModelAction *write)
2045 bool resolved = false;
2046 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2048 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2049 Promise *promise = (*promises)[promise_index];
2050 if (write->get_node()->get_promise(i)) {
2051 ModelAction *read = promise->get_action();
2052 if (read->is_rmw()) {
2053 mo_graph->addRMWEdge(write, read);
2055 read->read_from(write);
2056 //First fix up the modification order for actions that happened
2058 r_modification_order(read, write);
2059 //Next fix up the modification order for actions that happened
2061 post_r_modification_order(read, write);
2062 //Make sure the promise's value matches the write's value
2063 ASSERT(promise->get_value() == write->get_value());
2066 promises->erase(promises->begin() + promise_index);
2067 threads_to_check.push_back(read->get_tid());
2074 //Check whether reading these writes has made threads unable to
2077 for(unsigned int i=0;i<threads_to_check.size();i++)
2078 mo_check_promises(threads_to_check[i], write);
2084 * Compute the set of promises that could potentially be satisfied by this
2085 * action. Note that the set computation actually appears in the Node, not in
2087 * @param curr The ModelAction that may satisfy promises
2089 void ModelChecker::compute_promises(ModelAction *curr)
2091 for (unsigned int i = 0; i < promises->size(); i++) {
2092 Promise *promise = (*promises)[i];
2093 const ModelAction *act = promise->get_action();
2094 if (!act->happens_before(curr) &&
2096 !act->could_synchronize_with(curr) &&
2097 !act->same_thread(curr) &&
2098 act->get_location() == curr->get_location() &&
2099 promise->get_value() == curr->get_value()) {
2100 curr->get_node()->set_promise(i, act->is_rmw());
2105 /** Checks promises in response to change in ClockVector Threads. */
2106 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2108 for (unsigned int i = 0; i < promises->size(); i++) {
2109 Promise *promise = (*promises)[i];
2110 const ModelAction *act = promise->get_action();
2111 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2112 merge_cv->synchronized_since(act)) {
2113 if (promise->increment_threads(tid)) {
2114 //Promise has failed
2115 priv->failed_promise = true;
2122 void ModelChecker::check_promises_thread_disabled() {
2123 for (unsigned int i = 0; i < promises->size(); i++) {
2124 Promise *promise = (*promises)[i];
2125 if (promise->check_promise()) {
2126 priv->failed_promise = true;
2132 /** Checks promises in response to addition to modification order for threads.
2134 * pthread is the thread that performed the read that created the promise
2136 * pread is the read that created the promise
2138 * pwrite is either the first write to same location as pread by
2139 * pthread that is sequenced after pread or the value read by the
2140 * first read to the same lcoation as pread by pthread that is
2141 * sequenced after pread..
2143 * 1. If tid=pthread, then we check what other threads are reachable
2144 * through the mode order starting with pwrite. Those threads cannot
2145 * perform a write that will resolve the promise due to modification
2146 * order constraints.
2148 * 2. If the tid is not pthread, we check whether pwrite can reach the
2149 * action write through the modification order. If so, that thread
2150 * cannot perform a future write that will resolve the promise due to
2151 * modificatin order constraints.
2153 * @parem tid The thread that either read from the model action
2154 * write, or actually did the model action write.
2156 * @parem write The ModelAction representing the relevant write.
2159 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2160 void * location = write->get_location();
2161 for (unsigned int i = 0; i < promises->size(); i++) {
2162 Promise *promise = (*promises)[i];
2163 const ModelAction *act = promise->get_action();
2165 //Is this promise on the same location?
2166 if ( act->get_location() != location )
2169 //same thread as the promise
2170 if ( act->get_tid()==tid ) {
2172 //do we have a pwrite for the promise, if not, set it
2173 if (promise->get_write() == NULL ) {
2174 promise->set_write(write);
2175 //The pwrite cannot happen before the promise
2176 if (write->happens_before(act) && (write != act)) {
2177 priv->failed_promise = true;
2181 if (mo_graph->checkPromise(write, promise)) {
2182 priv->failed_promise = true;
2187 //Don't do any lookups twice for the same thread
2188 if (promise->has_sync_thread(tid))
2191 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2192 if (promise->increment_threads(tid)) {
2193 priv->failed_promise = true;
2201 * Compute the set of writes that may break the current pending release
2202 * sequence. This information is extracted from previou release sequence
2205 * @param curr The current ModelAction. Must be a release sequence fixup
2208 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2210 if (pending_rel_seqs->empty())
2213 struct release_seq *pending = pending_rel_seqs->back();
2214 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2215 const ModelAction *write = pending->writes[i];
2216 curr->get_node()->add_relseq_break(write);
2219 /* NULL means don't break the sequence; just synchronize */
2220 curr->get_node()->add_relseq_break(NULL);
2224 * Build up an initial set of all past writes that this 'read' action may read
2225 * from. This set is determined by the clock vector's "happens before"
2227 * @param curr is the current ModelAction that we are exploring; it must be a
2230 void ModelChecker::build_reads_from_past(ModelAction *curr)
2232 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2234 ASSERT(curr->is_read());
2236 ModelAction *last_seq_cst = NULL;
2238 /* Track whether this object has been initialized */
2239 bool initialized = false;
2241 if (curr->is_seqcst()) {
2242 last_seq_cst = get_last_seq_cst(curr);
2243 /* We have to at least see the last sequentially consistent write,
2244 so we are initialized. */
2245 if (last_seq_cst != NULL)
2249 /* Iterate over all threads */
2250 for (i = 0; i < thrd_lists->size(); i++) {
2251 /* Iterate over actions in thread, starting from most recent */
2252 action_list_t *list = &(*thrd_lists)[i];
2253 action_list_t::reverse_iterator rit;
2254 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2255 ModelAction *act = *rit;
2257 /* Only consider 'write' actions */
2258 if (!act->is_write() || act == curr)
2261 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2262 if (!curr->is_seqcst() || (!act->is_seqcst() && (last_seq_cst == NULL || !act->happens_before(last_seq_cst))) || act == last_seq_cst) {
2263 if (!curr->get_sleep_flag() || curr->is_seqcst() || sleep_can_read_from(curr, act)) {
2264 DEBUG("Adding action to may_read_from:\n");
2265 if (DBG_ENABLED()) {
2269 curr->get_node()->add_read_from(act);
2273 /* Include at most one act per-thread that "happens before" curr */
2274 if (act->happens_before(curr)) {
2282 assert_bug("May read from uninitialized atomic");
2284 if (DBG_ENABLED() || !initialized) {
2285 model_print("Reached read action:\n");
2287 model_print("Printing may_read_from\n");
2288 curr->get_node()->print_may_read_from();
2289 model_print("End printing may_read_from\n");
2293 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2295 Node *prevnode=write->get_node()->get_parent();
2297 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2298 if (write->is_release()&&thread_sleep)
2300 if (!write->is_rmw()) {
2303 if (write->get_reads_from()==NULL)
2305 write=write->get_reads_from();
2309 static void print_list(action_list_t *list, int exec_num = -1)
2311 action_list_t::iterator it;
2313 model_print("---------------------------------------------------------------------\n");
2315 model_print("Execution %d:\n", exec_num);
2317 unsigned int hash=0;
2319 for (it = list->begin(); it != list->end(); it++) {
2321 hash=hash^(hash<<3)^((*it)->hash());
2323 model_print("HASH %u\n", hash);
2324 model_print("---------------------------------------------------------------------\n");
2327 #if SUPPORT_MOD_ORDER_DUMP
2328 void ModelChecker::dumpGraph(char *filename) {
2330 sprintf(buffer, "%s.dot",filename);
2331 FILE *file=fopen(buffer, "w");
2332 fprintf(file, "digraph %s {\n",filename);
2333 mo_graph->dumpNodes(file);
2334 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2336 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2337 ModelAction *action=*it;
2338 if (action->is_read()) {
2339 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2340 if (action->get_reads_from()!=NULL)
2341 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2343 if (thread_array[action->get_tid()] != NULL) {
2344 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2347 thread_array[action->get_tid()]=action;
2349 fprintf(file,"}\n");
2350 model_free(thread_array);
2355 /** @brief Prints an execution trace summary. */
2356 void ModelChecker::print_summary() const
2358 #if SUPPORT_MOD_ORDER_DUMP
2360 char buffername[100];
2361 sprintf(buffername, "exec%04u", stats.num_total);
2362 mo_graph->dumpGraphToFile(buffername);
2363 sprintf(buffername, "graph%04u", stats.num_total);
2364 dumpGraph(buffername);
2367 if (!isfeasibleprefix())
2368 model_print("INFEASIBLE EXECUTION!\n");
2369 print_list(action_trace, stats.num_total);
2374 * Add a Thread to the system for the first time. Should only be called once
2376 * @param t The Thread to add
2378 void ModelChecker::add_thread(Thread *t)
2380 thread_map->put(id_to_int(t->get_id()), t);
2381 scheduler->add_thread(t);
2385 * Removes a thread from the scheduler.
2386 * @param the thread to remove.
2388 void ModelChecker::remove_thread(Thread *t)
2390 scheduler->remove_thread(t);
2394 * @brief Get a Thread reference by its ID
2395 * @param tid The Thread's ID
2396 * @return A Thread reference
2398 Thread * ModelChecker::get_thread(thread_id_t tid) const
2400 return thread_map->get(id_to_int(tid));
2404 * @brief Get a reference to the Thread in which a ModelAction was executed
2405 * @param act The ModelAction
2406 * @return A Thread reference
2408 Thread * ModelChecker::get_thread(ModelAction *act) const
2410 return get_thread(act->get_tid());
2414 * @brief Check if a Thread is currently enabled
2415 * @param t The Thread to check
2416 * @return True if the Thread is currently enabled
2418 bool ModelChecker::is_enabled(Thread *t) const
2420 return scheduler->is_enabled(t);
2424 * @brief Check if a Thread is currently enabled
2425 * @param tid The ID of the Thread to check
2426 * @return True if the Thread is currently enabled
2428 bool ModelChecker::is_enabled(thread_id_t tid) const
2430 return scheduler->is_enabled(tid);
2434 * Switch from a user-context to the "master thread" context (a.k.a. system
2435 * context). This switch is made with the intention of exploring a particular
2436 * model-checking action (described by a ModelAction object). Must be called
2437 * from a user-thread context.
2439 * @param act The current action that will be explored. May be NULL only if
2440 * trace is exiting via an assertion (see ModelChecker::set_assert and
2441 * ModelChecker::has_asserted).
2442 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2444 int ModelChecker::switch_to_master(ModelAction *act)
2447 Thread *old = thread_current();
2448 set_current_action(act);
2449 old->set_state(THREAD_READY);
2450 return Thread::swap(old, &system_context);
2454 * Takes the next step in the execution, if possible.
2455 * @return Returns true (success) if a step was taken and false otherwise.
2457 bool ModelChecker::take_step() {
2461 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2463 if (curr->get_state() == THREAD_READY) {
2464 ASSERT(priv->current_action);
2466 priv->nextThread = check_current_action(priv->current_action);
2467 priv->current_action = NULL;
2469 if (curr->is_blocked() || curr->is_complete())
2470 scheduler->remove_thread(curr);
2475 Thread *next = scheduler->next_thread(priv->nextThread);
2477 /* Infeasible -> don't take any more steps */
2478 if (is_infeasible())
2480 else if (isfeasibleprefix() && have_bug_reports()) {
2485 if (params.bound != 0) {
2486 if (priv->used_sequence_numbers > params.bound) {
2491 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2492 next ? id_to_int(next->get_id()) : -1);
2495 * Launch end-of-execution release sequence fixups only when there are:
2497 * (1) no more user threads to run (or when execution replay chooses
2498 * the 'model_thread')
2499 * (2) pending release sequences
2500 * (3) pending assertions (i.e., data races)
2501 * (4) no pending promises
2503 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2504 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2505 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2506 pending_rel_seqs->size());
2507 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2508 std::memory_order_seq_cst, NULL, VALUE_NONE,
2510 set_current_action(fixup);
2514 /* next == NULL -> don't take any more steps */
2518 next->set_state(THREAD_RUNNING);
2520 if (next->get_pending() != NULL) {
2521 /* restart a pending action */
2522 set_current_action(next->get_pending());
2523 next->set_pending(NULL);
2524 next->set_state(THREAD_READY);
2528 /* Return false only if swap fails with an error */
2529 return (Thread::swap(&system_context, next) == 0);
2532 /** Wrapper to run the user's main function, with appropriate arguments */
2533 void user_main_wrapper(void *)
2535 user_main(model->params.argc, model->params.argv);
2538 /** @brief Run ModelChecker for the user program */
2539 void ModelChecker::run()
2544 /* Start user program */
2545 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2547 /* Wait for all threads to complete */
2548 while (take_step());
2549 } while (next_execution());