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 (!isfinalfeasible())
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 = isfinalfeasible() && (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) {
1213 /** @return whether the current partial trace must be a prefix of a
1214 * feasible trace. */
1215 bool ModelChecker::isfeasibleprefix() const
1217 return promises->size() == 0 && pending_rel_seqs->size() == 0 && !is_infeasible();
1221 * Check if the current partial trace is infeasible. Does not check any
1222 * end-of-execution flags, which might rule out the execution. Thus, this is
1223 * useful only for ruling an execution as infeasible.
1224 * @return whether the current partial trace is infeasible.
1226 bool ModelChecker::is_infeasible() const
1228 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1229 DEBUG("Infeasible: RMW violation\n");
1231 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1235 * Check If the current partial trace is infeasible, while ignoring
1236 * infeasibility related to 2 RMW's reading from the same store. It does not
1237 * check end-of-execution feasibility.
1238 * @see ModelChecker::is_infeasible
1239 * @return whether the current partial trace is infeasible, ignoring multiple
1240 * RMWs reading from the same store.
1242 bool ModelChecker::is_infeasible_ignoreRMW() const
1244 if (DBG_ENABLED()) {
1245 if (mo_graph->checkForCycles())
1246 DEBUG("Infeasible: modification order cycles\n");
1247 if (priv->failed_promise)
1248 DEBUG("Infeasible: failed promise\n");
1249 if (priv->too_many_reads)
1250 DEBUG("Infeasible: too many reads\n");
1251 if (priv->bad_synchronization)
1252 DEBUG("Infeasible: bad synchronization ordering\n");
1253 if (promises_expired())
1254 DEBUG("Infeasible: promises expired\n");
1256 return mo_graph->checkForCycles() || priv->failed_promise ||
1257 priv->too_many_reads || priv->bad_synchronization ||
1261 /** Returns whether the current completed trace is feasible. */
1262 bool ModelChecker::isfinalfeasible() const
1264 if (DBG_ENABLED() && promises->size() != 0)
1265 DEBUG("Infeasible: unrevolved promises\n");
1267 return !is_infeasible() && promises->size() == 0;
1270 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1271 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1272 ModelAction *lastread = get_last_action(act->get_tid());
1273 lastread->process_rmw(act);
1274 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1275 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1276 mo_graph->commitChanges();
1282 * Checks whether a thread has read from the same write for too many times
1283 * without seeing the effects of a later write.
1286 * 1) there must a different write that we could read from that would satisfy the modification order,
1287 * 2) we must have read from the same value in excess of maxreads times, and
1288 * 3) that other write must have been in the reads_from set for maxreads times.
1290 * If so, we decide that the execution is no longer feasible.
1292 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1293 if (params.maxreads != 0) {
1295 if (curr->get_node()->get_read_from_size() <= 1)
1297 //Must make sure that execution is currently feasible... We could
1298 //accidentally clear by rolling back
1299 if (is_infeasible())
1301 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1302 int tid = id_to_int(curr->get_tid());
1305 if ((int)thrd_lists->size() <= tid)
1307 action_list_t *list = &(*thrd_lists)[tid];
1309 action_list_t::reverse_iterator rit = list->rbegin();
1310 /* Skip past curr */
1311 for (; (*rit) != curr; rit++)
1313 /* go past curr now */
1316 action_list_t::reverse_iterator ritcopy = rit;
1317 //See if we have enough reads from the same value
1319 for (; count < params.maxreads; rit++,count++) {
1320 if (rit==list->rend())
1322 ModelAction *act = *rit;
1323 if (!act->is_read())
1326 if (act->get_reads_from() != rf)
1328 if (act->get_node()->get_read_from_size() <= 1)
1331 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1333 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1335 //Need a different write
1339 /* Test to see whether this is a feasible write to read from*/
1340 mo_graph->startChanges();
1341 r_modification_order(curr, write);
1342 bool feasiblereadfrom = !is_infeasible();
1343 mo_graph->rollbackChanges();
1345 if (!feasiblereadfrom)
1349 bool feasiblewrite = true;
1350 //new we need to see if this write works for everyone
1352 for (int loop = count; loop>0; loop--,rit++) {
1353 ModelAction *act=*rit;
1354 bool foundvalue = false;
1355 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1356 if (act->get_node()->get_read_from_at(j)==write) {
1362 feasiblewrite = false;
1366 if (feasiblewrite) {
1367 priv->too_many_reads = true;
1375 * Updates the mo_graph with the constraints imposed from the current
1378 * Basic idea is the following: Go through each other thread and find
1379 * the lastest action that happened before our read. Two cases:
1381 * (1) The action is a write => that write must either occur before
1382 * the write we read from or be the write we read from.
1384 * (2) The action is a read => the write that that action read from
1385 * must occur before the write we read from or be the same write.
1387 * @param curr The current action. Must be a read.
1388 * @param rf The action that curr reads from. Must be a write.
1389 * @return True if modification order edges were added; false otherwise
1391 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1393 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1396 ASSERT(curr->is_read());
1398 /* Iterate over all threads */
1399 for (i = 0; i < thrd_lists->size(); i++) {
1400 /* Iterate over actions in thread, starting from most recent */
1401 action_list_t *list = &(*thrd_lists)[i];
1402 action_list_t::reverse_iterator rit;
1403 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1404 ModelAction *act = *rit;
1407 * Include at most one act per-thread that "happens
1408 * before" curr. Don't consider reflexively.
1410 if (act->happens_before(curr) && act != curr) {
1411 if (act->is_write()) {
1413 mo_graph->addEdge(act, rf);
1417 const ModelAction *prevreadfrom = act->get_reads_from();
1418 //if the previous read is unresolved, keep going...
1419 if (prevreadfrom == NULL)
1422 if (rf != prevreadfrom) {
1423 mo_graph->addEdge(prevreadfrom, rf);
1435 /** This method fixes up the modification order when we resolve a
1436 * promises. The basic problem is that actions that occur after the
1437 * read curr could not property add items to the modification order
1440 * So for each thread, we find the earliest item that happens after
1441 * the read curr. This is the item we have to fix up with additional
1442 * constraints. If that action is write, we add a MO edge between
1443 * the Action rf and that action. If the action is a read, we add a
1444 * MO edge between the Action rf, and whatever the read accessed.
1446 * @param curr is the read ModelAction that we are fixing up MO edges for.
1447 * @param rf is the write ModelAction that curr reads from.
1450 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1452 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1454 ASSERT(curr->is_read());
1456 /* Iterate over all threads */
1457 for (i = 0; i < thrd_lists->size(); i++) {
1458 /* Iterate over actions in thread, starting from most recent */
1459 action_list_t *list = &(*thrd_lists)[i];
1460 action_list_t::reverse_iterator rit;
1461 ModelAction *lastact = NULL;
1463 /* Find last action that happens after curr that is either not curr or a rmw */
1464 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1465 ModelAction *act = *rit;
1466 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1472 /* Include at most one act per-thread that "happens before" curr */
1473 if (lastact != NULL) {
1474 if (lastact==curr) {
1475 //Case 1: The resolved read is a RMW, and we need to make sure
1476 //that the write portion of the RMW mod order after rf
1478 mo_graph->addEdge(rf, lastact);
1479 } else if (lastact->is_read()) {
1480 //Case 2: The resolved read is a normal read and the next
1481 //operation is a read, and we need to make sure the value read
1482 //is mod ordered after rf
1484 const ModelAction *postreadfrom = lastact->get_reads_from();
1485 if (postreadfrom != NULL&&rf != postreadfrom)
1486 mo_graph->addEdge(rf, postreadfrom);
1488 //Case 3: The resolved read is a normal read and the next
1489 //operation is a write, and we need to make sure that the
1490 //write is mod ordered after rf
1492 mo_graph->addEdge(rf, lastact);
1500 * Updates the mo_graph with the constraints imposed from the current write.
1502 * Basic idea is the following: Go through each other thread and find
1503 * the lastest action that happened before our write. Two cases:
1505 * (1) The action is a write => that write must occur before
1508 * (2) The action is a read => the write that that action read from
1509 * must occur before the current write.
1511 * This method also handles two other issues:
1513 * (I) Sequential Consistency: Making sure that if the current write is
1514 * seq_cst, that it occurs after the previous seq_cst write.
1516 * (II) Sending the write back to non-synchronizing reads.
1518 * @param curr The current action. Must be a write.
1519 * @return True if modification order edges were added; false otherwise
1521 bool ModelChecker::w_modification_order(ModelAction *curr)
1523 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1526 ASSERT(curr->is_write());
1528 if (curr->is_seqcst()) {
1529 /* We have to at least see the last sequentially consistent write,
1530 so we are initialized. */
1531 ModelAction *last_seq_cst = get_last_seq_cst(curr);
1532 if (last_seq_cst != NULL) {
1533 mo_graph->addEdge(last_seq_cst, curr);
1538 /* Iterate over all threads */
1539 for (i = 0; i < thrd_lists->size(); i++) {
1540 /* Iterate over actions in thread, starting from most recent */
1541 action_list_t *list = &(*thrd_lists)[i];
1542 action_list_t::reverse_iterator rit;
1543 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1544 ModelAction *act = *rit;
1547 * 1) If RMW and it actually read from something, then we
1548 * already have all relevant edges, so just skip to next
1551 * 2) If RMW and it didn't read from anything, we should
1552 * whatever edge we can get to speed up convergence.
1554 * 3) If normal write, we need to look at earlier actions, so
1555 * continue processing list.
1557 if (curr->is_rmw()) {
1558 if (curr->get_reads_from()!=NULL)
1567 * Include at most one act per-thread that "happens
1570 if (act->happens_before(curr)) {
1572 * Note: if act is RMW, just add edge:
1574 * The following edge should be handled elsewhere:
1575 * readfrom(act) --mo--> act
1577 if (act->is_write())
1578 mo_graph->addEdge(act, curr);
1579 else if (act->is_read()) {
1580 //if previous read accessed a null, just keep going
1581 if (act->get_reads_from() == NULL)
1583 mo_graph->addEdge(act->get_reads_from(), curr);
1587 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1588 !act->same_thread(curr)) {
1589 /* We have an action that:
1590 (1) did not happen before us
1591 (2) is a read and we are a write
1592 (3) cannot synchronize with us
1593 (4) is in a different thread
1595 that read could potentially read from our write. Note that
1596 these checks are overly conservative at this point, we'll
1597 do more checks before actually removing the
1601 if (thin_air_constraint_may_allow(curr, act)) {
1602 if (!is_infeasible() ||
1603 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1604 struct PendingFutureValue pfv = {curr,act};
1605 futurevalues->push_back(pfv);
1615 /** Arbitrary reads from the future are not allowed. Section 29.3
1616 * part 9 places some constraints. This method checks one result of constraint
1617 * constraint. Others require compiler support. */
1618 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1619 if (!writer->is_rmw())
1622 if (!reader->is_rmw())
1625 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1626 if (search == reader)
1628 if (search->get_tid() == reader->get_tid() &&
1629 search->happens_before(reader))
1637 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1638 * some constraints. This method checks one the following constraint (others
1639 * require compiler support):
1641 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1643 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1645 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1647 /* Iterate over all threads */
1648 for (i = 0; i < thrd_lists->size(); i++) {
1649 const ModelAction *write_after_read = NULL;
1651 /* Iterate over actions in thread, starting from most recent */
1652 action_list_t *list = &(*thrd_lists)[i];
1653 action_list_t::reverse_iterator rit;
1654 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1655 ModelAction *act = *rit;
1657 if (!reader->happens_before(act))
1659 else if (act->is_write())
1660 write_after_read = act;
1661 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1662 write_after_read = act->get_reads_from();
1666 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1673 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1674 * The ModelAction under consideration is expected to be taking part in
1675 * release/acquire synchronization as an object of the "reads from" relation.
1676 * Note that this can only provide release sequence support for RMW chains
1677 * which do not read from the future, as those actions cannot be traced until
1678 * their "promise" is fulfilled. Similarly, we may not even establish the
1679 * presence of a release sequence with certainty, as some modification order
1680 * constraints may be decided further in the future. Thus, this function
1681 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1682 * and a boolean representing certainty.
1684 * @param rf The action that might be part of a release sequence. Must be a
1686 * @param release_heads A pass-by-reference style return parameter. After
1687 * execution of this function, release_heads will contain the heads of all the
1688 * relevant release sequences, if any exists with certainty
1689 * @param pending A pass-by-reference style return parameter which is only used
1690 * when returning false (i.e., uncertain). Returns most information regarding
1691 * an uncertain release sequence, including any write operations that might
1692 * break the sequence.
1693 * @return true, if the ModelChecker is certain that release_heads is complete;
1696 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1697 rel_heads_list_t *release_heads,
1698 struct release_seq *pending) const
1700 /* Only check for release sequences if there are no cycles */
1701 if (mo_graph->checkForCycles())
1705 ASSERT(rf->is_write());
1707 if (rf->is_release())
1708 release_heads->push_back(rf);
1710 break; /* End of RMW chain */
1712 /** @todo Need to be smarter here... In the linux lock
1713 * example, this will run to the beginning of the program for
1715 /** @todo The way to be smarter here is to keep going until 1
1716 * thread has a release preceded by an acquire and you've seen
1719 /* acq_rel RMW is a sufficient stopping condition */
1720 if (rf->is_acquire() && rf->is_release())
1721 return true; /* complete */
1723 rf = rf->get_reads_from();
1726 /* read from future: need to settle this later */
1728 return false; /* incomplete */
1731 if (rf->is_release())
1732 return true; /* complete */
1734 /* else relaxed write; check modification order for contiguous subsequence
1735 * -> rf must be same thread as release */
1736 int tid = id_to_int(rf->get_tid());
1737 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1738 action_list_t *list = &(*thrd_lists)[tid];
1739 action_list_t::const_reverse_iterator rit;
1741 /* Find rf in the thread list */
1742 rit = std::find(list->rbegin(), list->rend(), rf);
1743 ASSERT(rit != list->rend());
1745 /* Find the last write/release */
1746 for (; rit != list->rend(); rit++)
1747 if ((*rit)->is_release())
1749 if (rit == list->rend()) {
1750 /* No write-release in this thread */
1751 return true; /* complete */
1753 ModelAction *release = *rit;
1755 ASSERT(rf->same_thread(release));
1757 pending->writes.clear();
1759 bool certain = true;
1760 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1761 if (id_to_int(rf->get_tid()) == (int)i)
1763 list = &(*thrd_lists)[i];
1765 /* Can we ensure no future writes from this thread may break
1766 * the release seq? */
1767 bool future_ordered = false;
1769 ModelAction *last = get_last_action(int_to_id(i));
1770 Thread *th = get_thread(int_to_id(i));
1771 if ((last && rf->happens_before(last)) ||
1774 future_ordered = true;
1776 ASSERT(!th->is_model_thread() || future_ordered);
1778 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1779 const ModelAction *act = *rit;
1780 /* Reach synchronization -> this thread is complete */
1781 if (act->happens_before(release))
1783 if (rf->happens_before(act)) {
1784 future_ordered = true;
1788 /* Only non-RMW writes can break release sequences */
1789 if (!act->is_write() || act->is_rmw())
1792 /* Check modification order */
1793 if (mo_graph->checkReachable(rf, act)) {
1794 /* rf --mo--> act */
1795 future_ordered = true;
1798 if (mo_graph->checkReachable(act, release))
1799 /* act --mo--> release */
1801 if (mo_graph->checkReachable(release, act) &&
1802 mo_graph->checkReachable(act, rf)) {
1803 /* release --mo-> act --mo--> rf */
1804 return true; /* complete */
1806 /* act may break release sequence */
1807 pending->writes.push_back(act);
1810 if (!future_ordered)
1811 certain = false; /* This thread is uncertain */
1815 release_heads->push_back(release);
1816 pending->writes.clear();
1818 pending->release = release;
1825 * A public interface for getting the release sequence head(s) with which a
1826 * given ModelAction must synchronize. This function only returns a non-empty
1827 * result when it can locate a release sequence head with certainty. Otherwise,
1828 * it may mark the internal state of the ModelChecker so that it will handle
1829 * the release sequence at a later time, causing @a act to update its
1830 * synchronization at some later point in execution.
1831 * @param act The 'acquire' action that may read from a release sequence
1832 * @param release_heads A pass-by-reference return parameter. Will be filled
1833 * with the head(s) of the release sequence(s), if they exists with certainty.
1834 * @see ModelChecker::release_seq_heads
1836 void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
1838 const ModelAction *rf = act->get_reads_from();
1839 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
1840 sequence->acquire = act;
1842 if (!release_seq_heads(rf, release_heads, sequence)) {
1843 /* add act to 'lazy checking' list */
1844 pending_rel_seqs->push_back(sequence);
1846 snapshot_free(sequence);
1851 * Attempt to resolve all stashed operations that might synchronize with a
1852 * release sequence for a given location. This implements the "lazy" portion of
1853 * determining whether or not a release sequence was contiguous, since not all
1854 * modification order information is present at the time an action occurs.
1856 * @param location The location/object that should be checked for release
1857 * sequence resolutions. A NULL value means to check all locations.
1858 * @param work_queue The work queue to which to add work items as they are
1860 * @return True if any updates occurred (new synchronization, new mo_graph
1863 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
1865 bool updated = false;
1866 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
1867 while (it != pending_rel_seqs->end()) {
1868 struct release_seq *pending = *it;
1869 ModelAction *act = pending->acquire;
1871 /* Only resolve sequences on the given location, if provided */
1872 if (location && act->get_location() != location) {
1877 const ModelAction *rf = act->get_reads_from();
1878 rel_heads_list_t release_heads;
1880 complete = release_seq_heads(rf, &release_heads, pending);
1881 for (unsigned int i = 0; i < release_heads.size(); i++) {
1882 if (!act->has_synchronized_with(release_heads[i])) {
1883 if (act->synchronize_with(release_heads[i]))
1886 set_bad_synchronization();
1891 /* Re-check all pending release sequences */
1892 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1893 /* Re-check act for mo_graph edges */
1894 work_queue->push_back(MOEdgeWorkEntry(act));
1896 /* propagate synchronization to later actions */
1897 action_list_t::reverse_iterator rit = action_trace->rbegin();
1898 for (; (*rit) != act; rit++) {
1899 ModelAction *propagate = *rit;
1900 if (act->happens_before(propagate)) {
1901 propagate->synchronize_with(act);
1902 /* Re-check 'propagate' for mo_graph edges */
1903 work_queue->push_back(MOEdgeWorkEntry(propagate));
1908 it = pending_rel_seqs->erase(it);
1909 snapshot_free(pending);
1915 // If we resolved promises or data races, see if we have realized a data race.
1922 * Performs various bookkeeping operations for the current ModelAction. For
1923 * instance, adds action to the per-object, per-thread action vector and to the
1924 * action trace list of all thread actions.
1926 * @param act is the ModelAction to add.
1928 void ModelChecker::add_action_to_lists(ModelAction *act)
1930 int tid = id_to_int(act->get_tid());
1931 action_trace->push_back(act);
1933 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
1935 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
1936 if (tid >= (int)vec->size())
1937 vec->resize(priv->next_thread_id);
1938 (*vec)[tid].push_back(act);
1940 if ((int)thrd_last_action->size() <= tid)
1941 thrd_last_action->resize(get_num_threads());
1942 (*thrd_last_action)[tid] = act;
1944 if (act->is_wait()) {
1945 void *mutex_loc=(void *) act->get_value();
1946 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
1948 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
1949 if (tid >= (int)vec->size())
1950 vec->resize(priv->next_thread_id);
1951 (*vec)[tid].push_back(act);
1953 if ((int)thrd_last_action->size() <= tid)
1954 thrd_last_action->resize(get_num_threads());
1955 (*thrd_last_action)[tid] = act;
1960 * @brief Get the last action performed by a particular Thread
1961 * @param tid The thread ID of the Thread in question
1962 * @return The last action in the thread
1964 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
1966 int threadid = id_to_int(tid);
1967 if (threadid < (int)thrd_last_action->size())
1968 return (*thrd_last_action)[id_to_int(tid)];
1974 * Gets the last memory_order_seq_cst write (in the total global sequence)
1975 * performed on a particular object (i.e., memory location), not including the
1977 * @param curr The current ModelAction; also denotes the object location to
1979 * @return The last seq_cst write
1981 ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const
1983 void *location = curr->get_location();
1984 action_list_t *list = get_safe_ptr_action(obj_map, location);
1985 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1986 action_list_t::reverse_iterator rit;
1987 for (rit = list->rbegin(); rit != list->rend(); rit++)
1988 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
1994 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1995 * location). This function identifies the mutex according to the current
1996 * action, which is presumed to perform on the same mutex.
1997 * @param curr The current ModelAction; also denotes the object location to
1999 * @return The last unlock operation
2001 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2003 void *location = curr->get_location();
2004 action_list_t *list = get_safe_ptr_action(obj_map, location);
2005 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2006 action_list_t::reverse_iterator rit;
2007 for (rit = list->rbegin(); rit != list->rend(); rit++)
2008 if ((*rit)->is_unlock() || (*rit)->is_wait())
2013 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
2015 ModelAction *parent = get_last_action(tid);
2017 parent = get_thread(tid)->get_creation();
2022 * Returns the clock vector for a given thread.
2023 * @param tid The thread whose clock vector we want
2024 * @return Desired clock vector
2026 ClockVector * ModelChecker::get_cv(thread_id_t tid)
2028 return get_parent_action(tid)->get_cv();
2032 * Resolve a set of Promises with a current write. The set is provided in the
2033 * Node corresponding to @a write.
2034 * @param write The ModelAction that is fulfilling Promises
2035 * @return True if promises were resolved; false otherwise
2037 bool ModelChecker::resolve_promises(ModelAction *write)
2039 bool resolved = false;
2040 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2042 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2043 Promise *promise = (*promises)[promise_index];
2044 if (write->get_node()->get_promise(i)) {
2045 ModelAction *read = promise->get_action();
2046 if (read->is_rmw()) {
2047 mo_graph->addRMWEdge(write, read);
2049 read->read_from(write);
2050 //First fix up the modification order for actions that happened
2052 r_modification_order(read, write);
2053 //Next fix up the modification order for actions that happened
2055 post_r_modification_order(read, write);
2056 //Make sure the promise's value matches the write's value
2057 ASSERT(promise->get_value() == write->get_value());
2060 promises->erase(promises->begin() + promise_index);
2061 threads_to_check.push_back(read->get_tid());
2068 //Check whether reading these writes has made threads unable to
2071 for(unsigned int i=0;i<threads_to_check.size();i++)
2072 mo_check_promises(threads_to_check[i], write);
2078 * Compute the set of promises that could potentially be satisfied by this
2079 * action. Note that the set computation actually appears in the Node, not in
2081 * @param curr The ModelAction that may satisfy promises
2083 void ModelChecker::compute_promises(ModelAction *curr)
2085 for (unsigned int i = 0; i < promises->size(); i++) {
2086 Promise *promise = (*promises)[i];
2087 const ModelAction *act = promise->get_action();
2088 if (!act->happens_before(curr) &&
2090 !act->could_synchronize_with(curr) &&
2091 !act->same_thread(curr) &&
2092 act->get_location() == curr->get_location() &&
2093 promise->get_value() == curr->get_value()) {
2094 curr->get_node()->set_promise(i, act->is_rmw());
2099 /** Checks promises in response to change in ClockVector Threads. */
2100 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2102 for (unsigned int i = 0; i < promises->size(); i++) {
2103 Promise *promise = (*promises)[i];
2104 const ModelAction *act = promise->get_action();
2105 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2106 merge_cv->synchronized_since(act)) {
2107 if (promise->increment_threads(tid)) {
2108 //Promise has failed
2109 priv->failed_promise = true;
2116 void ModelChecker::check_promises_thread_disabled() {
2117 for (unsigned int i = 0; i < promises->size(); i++) {
2118 Promise *promise = (*promises)[i];
2119 if (promise->check_promise()) {
2120 priv->failed_promise = true;
2126 /** Checks promises in response to addition to modification order for threads.
2128 * pthread is the thread that performed the read that created the promise
2130 * pread is the read that created the promise
2132 * pwrite is either the first write to same location as pread by
2133 * pthread that is sequenced after pread or the value read by the
2134 * first read to the same lcoation as pread by pthread that is
2135 * sequenced after pread..
2137 * 1. If tid=pthread, then we check what other threads are reachable
2138 * through the mode order starting with pwrite. Those threads cannot
2139 * perform a write that will resolve the promise due to modification
2140 * order constraints.
2142 * 2. If the tid is not pthread, we check whether pwrite can reach the
2143 * action write through the modification order. If so, that thread
2144 * cannot perform a future write that will resolve the promise due to
2145 * modificatin order constraints.
2147 * @parem tid The thread that either read from the model action
2148 * write, or actually did the model action write.
2150 * @parem write The ModelAction representing the relevant write.
2153 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2154 void * location = write->get_location();
2155 for (unsigned int i = 0; i < promises->size(); i++) {
2156 Promise *promise = (*promises)[i];
2157 const ModelAction *act = promise->get_action();
2159 //Is this promise on the same location?
2160 if ( act->get_location() != location )
2163 //same thread as the promise
2164 if ( act->get_tid()==tid ) {
2166 //do we have a pwrite for the promise, if not, set it
2167 if (promise->get_write() == NULL ) {
2168 promise->set_write(write);
2169 //The pwrite cannot happen before the promise
2170 if (write->happens_before(act) && (write != act)) {
2171 priv->failed_promise = true;
2175 if (mo_graph->checkPromise(write, promise)) {
2176 priv->failed_promise = true;
2181 //Don't do any lookups twice for the same thread
2182 if (promise->has_sync_thread(tid))
2185 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2186 if (promise->increment_threads(tid)) {
2187 priv->failed_promise = true;
2195 * Compute the set of writes that may break the current pending release
2196 * sequence. This information is extracted from previou release sequence
2199 * @param curr The current ModelAction. Must be a release sequence fixup
2202 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2204 if (pending_rel_seqs->empty())
2207 struct release_seq *pending = pending_rel_seqs->back();
2208 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2209 const ModelAction *write = pending->writes[i];
2210 curr->get_node()->add_relseq_break(write);
2213 /* NULL means don't break the sequence; just synchronize */
2214 curr->get_node()->add_relseq_break(NULL);
2218 * Build up an initial set of all past writes that this 'read' action may read
2219 * from. This set is determined by the clock vector's "happens before"
2221 * @param curr is the current ModelAction that we are exploring; it must be a
2224 void ModelChecker::build_reads_from_past(ModelAction *curr)
2226 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2228 ASSERT(curr->is_read());
2230 ModelAction *last_seq_cst = NULL;
2232 /* Track whether this object has been initialized */
2233 bool initialized = false;
2235 if (curr->is_seqcst()) {
2236 last_seq_cst = get_last_seq_cst(curr);
2237 /* We have to at least see the last sequentially consistent write,
2238 so we are initialized. */
2239 if (last_seq_cst != NULL)
2243 /* Iterate over all threads */
2244 for (i = 0; i < thrd_lists->size(); i++) {
2245 /* Iterate over actions in thread, starting from most recent */
2246 action_list_t *list = &(*thrd_lists)[i];
2247 action_list_t::reverse_iterator rit;
2248 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2249 ModelAction *act = *rit;
2251 /* Only consider 'write' actions */
2252 if (!act->is_write() || act == curr)
2255 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2256 if (!curr->is_seqcst() || (!act->is_seqcst() && (last_seq_cst == NULL || !act->happens_before(last_seq_cst))) || act == last_seq_cst) {
2257 if (!curr->get_sleep_flag() || curr->is_seqcst() || sleep_can_read_from(curr, act)) {
2258 DEBUG("Adding action to may_read_from:\n");
2259 if (DBG_ENABLED()) {
2263 curr->get_node()->add_read_from(act);
2267 /* Include at most one act per-thread that "happens before" curr */
2268 if (act->happens_before(curr)) {
2276 assert_bug("May read from uninitialized atomic");
2278 if (DBG_ENABLED() || !initialized) {
2279 model_print("Reached read action:\n");
2281 model_print("Printing may_read_from\n");
2282 curr->get_node()->print_may_read_from();
2283 model_print("End printing may_read_from\n");
2287 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2289 Node *prevnode=write->get_node()->get_parent();
2291 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2292 if (write->is_release()&&thread_sleep)
2294 if (!write->is_rmw()) {
2297 if (write->get_reads_from()==NULL)
2299 write=write->get_reads_from();
2303 static void print_list(action_list_t *list, int exec_num = -1)
2305 action_list_t::iterator it;
2307 model_print("---------------------------------------------------------------------\n");
2309 model_print("Execution %d:\n", exec_num);
2311 unsigned int hash=0;
2313 for (it = list->begin(); it != list->end(); it++) {
2315 hash=hash^(hash<<3)^((*it)->hash());
2317 model_print("HASH %u\n", hash);
2318 model_print("---------------------------------------------------------------------\n");
2321 #if SUPPORT_MOD_ORDER_DUMP
2322 void ModelChecker::dumpGraph(char *filename) {
2324 sprintf(buffer, "%s.dot",filename);
2325 FILE *file=fopen(buffer, "w");
2326 fprintf(file, "digraph %s {\n",filename);
2327 mo_graph->dumpNodes(file);
2328 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2330 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2331 ModelAction *action=*it;
2332 if (action->is_read()) {
2333 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2334 if (action->get_reads_from()!=NULL)
2335 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2337 if (thread_array[action->get_tid()] != NULL) {
2338 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2341 thread_array[action->get_tid()]=action;
2343 fprintf(file,"}\n");
2344 model_free(thread_array);
2349 /** @brief Prints an execution trace summary. */
2350 void ModelChecker::print_summary() const
2352 #if SUPPORT_MOD_ORDER_DUMP
2354 char buffername[100];
2355 sprintf(buffername, "exec%04u", stats.num_total);
2356 mo_graph->dumpGraphToFile(buffername);
2357 sprintf(buffername, "graph%04u", stats.num_total);
2358 dumpGraph(buffername);
2361 if (!isfinalfeasible())
2362 model_print("INFEASIBLE EXECUTION!\n");
2363 print_list(action_trace, stats.num_total);
2368 * Add a Thread to the system for the first time. Should only be called once
2370 * @param t The Thread to add
2372 void ModelChecker::add_thread(Thread *t)
2374 thread_map->put(id_to_int(t->get_id()), t);
2375 scheduler->add_thread(t);
2379 * Removes a thread from the scheduler.
2380 * @param the thread to remove.
2382 void ModelChecker::remove_thread(Thread *t)
2384 scheduler->remove_thread(t);
2388 * @brief Get a Thread reference by its ID
2389 * @param tid The Thread's ID
2390 * @return A Thread reference
2392 Thread * ModelChecker::get_thread(thread_id_t tid) const
2394 return thread_map->get(id_to_int(tid));
2398 * @brief Get a reference to the Thread in which a ModelAction was executed
2399 * @param act The ModelAction
2400 * @return A Thread reference
2402 Thread * ModelChecker::get_thread(ModelAction *act) const
2404 return get_thread(act->get_tid());
2408 * @brief Check if a Thread is currently enabled
2409 * @param t The Thread to check
2410 * @return True if the Thread is currently enabled
2412 bool ModelChecker::is_enabled(Thread *t) const
2414 return scheduler->is_enabled(t);
2418 * @brief Check if a Thread is currently enabled
2419 * @param tid The ID of the Thread to check
2420 * @return True if the Thread is currently enabled
2422 bool ModelChecker::is_enabled(thread_id_t tid) const
2424 return scheduler->is_enabled(tid);
2428 * Switch from a user-context to the "master thread" context (a.k.a. system
2429 * context). This switch is made with the intention of exploring a particular
2430 * model-checking action (described by a ModelAction object). Must be called
2431 * from a user-thread context.
2433 * @param act The current action that will be explored. May be NULL only if
2434 * trace is exiting via an assertion (see ModelChecker::set_assert and
2435 * ModelChecker::has_asserted).
2436 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2438 int ModelChecker::switch_to_master(ModelAction *act)
2441 Thread *old = thread_current();
2442 set_current_action(act);
2443 old->set_state(THREAD_READY);
2444 return Thread::swap(old, &system_context);
2448 * Takes the next step in the execution, if possible.
2449 * @return Returns true (success) if a step was taken and false otherwise.
2451 bool ModelChecker::take_step() {
2455 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2457 if (curr->get_state() == THREAD_READY) {
2458 ASSERT(priv->current_action);
2460 priv->nextThread = check_current_action(priv->current_action);
2461 priv->current_action = NULL;
2463 if (curr->is_blocked() || curr->is_complete())
2464 scheduler->remove_thread(curr);
2469 Thread *next = scheduler->next_thread(priv->nextThread);
2471 /* Infeasible -> don't take any more steps */
2472 if (is_infeasible())
2474 else if (isfeasibleprefix() && have_bug_reports()) {
2479 if (params.bound != 0) {
2480 if (priv->used_sequence_numbers > params.bound) {
2485 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2486 next ? id_to_int(next->get_id()) : -1);
2489 * Launch end-of-execution release sequence fixups only when there are:
2491 * (1) no more user threads to run (or when execution replay chooses
2492 * the 'model_thread')
2493 * (2) pending release sequences
2494 * (3) pending assertions (i.e., data races)
2495 * (4) no pending promises
2497 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2498 isfinalfeasible() && !unrealizedraces.empty()) {
2499 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2500 pending_rel_seqs->size());
2501 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2502 std::memory_order_seq_cst, NULL, VALUE_NONE,
2504 set_current_action(fixup);
2508 /* next == NULL -> don't take any more steps */
2512 next->set_state(THREAD_RUNNING);
2514 if (next->get_pending() != NULL) {
2515 /* restart a pending action */
2516 set_current_action(next->get_pending());
2517 next->set_pending(NULL);
2518 next->set_state(THREAD_READY);
2522 /* Return false only if swap fails with an error */
2523 return (Thread::swap(&system_context, next) == 0);
2526 /** Wrapper to run the user's main function, with appropriate arguments */
2527 void user_main_wrapper(void *)
2529 user_main(model->params.argc, model->params.argv);
2532 /** @brief Run ModelChecker for the user program */
2533 void ModelChecker::run()
2538 /* Start user program */
2539 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2541 /* Wait for all threads to complete */
2542 while (take_step());
2543 } while (next_execution());