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 promises->size() == 0 && pending_rel_seqs->size() == 0 && !is_infeasible();
1223 /** Returns whether the current completed trace is feasible. */
1224 bool ModelChecker::isfinalfeasible() const
1226 if (DBG_ENABLED() && promises->size() != 0)
1227 DEBUG("Infeasible: unrevolved promises\n");
1229 return !is_infeasible() && promises->size() == 0;
1233 * Check if the current partial trace is infeasible. Does not check any
1234 * end-of-execution flags, which might rule out the execution. Thus, this is
1235 * useful only for ruling an execution as infeasible.
1236 * @return whether the current partial trace is infeasible.
1238 bool ModelChecker::is_infeasible() const
1240 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1241 DEBUG("Infeasible: RMW violation\n");
1243 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1247 * Check If the current partial trace is infeasible, while ignoring
1248 * infeasibility related to 2 RMW's reading from the same store. It does not
1249 * check end-of-execution feasibility.
1250 * @see ModelChecker::is_infeasible
1251 * @return whether the current partial trace is infeasible, ignoring multiple
1252 * RMWs reading from the same store.
1254 bool ModelChecker::is_infeasible_ignoreRMW() const
1256 if (DBG_ENABLED()) {
1257 if (mo_graph->checkForCycles())
1258 DEBUG("Infeasible: modification order cycles\n");
1259 if (priv->failed_promise)
1260 DEBUG("Infeasible: failed promise\n");
1261 if (priv->too_many_reads)
1262 DEBUG("Infeasible: too many reads\n");
1263 if (priv->bad_synchronization)
1264 DEBUG("Infeasible: bad synchronization ordering\n");
1265 if (promises_expired())
1266 DEBUG("Infeasible: promises expired\n");
1268 return mo_graph->checkForCycles() || priv->failed_promise ||
1269 priv->too_many_reads || priv->bad_synchronization ||
1273 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1274 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1275 ModelAction *lastread = get_last_action(act->get_tid());
1276 lastread->process_rmw(act);
1277 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1278 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1279 mo_graph->commitChanges();
1285 * Checks whether a thread has read from the same write for too many times
1286 * without seeing the effects of a later write.
1289 * 1) there must a different write that we could read from that would satisfy the modification order,
1290 * 2) we must have read from the same value in excess of maxreads times, and
1291 * 3) that other write must have been in the reads_from set for maxreads times.
1293 * If so, we decide that the execution is no longer feasible.
1295 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1296 if (params.maxreads != 0) {
1298 if (curr->get_node()->get_read_from_size() <= 1)
1300 //Must make sure that execution is currently feasible... We could
1301 //accidentally clear by rolling back
1302 if (is_infeasible())
1304 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1305 int tid = id_to_int(curr->get_tid());
1308 if ((int)thrd_lists->size() <= tid)
1310 action_list_t *list = &(*thrd_lists)[tid];
1312 action_list_t::reverse_iterator rit = list->rbegin();
1313 /* Skip past curr */
1314 for (; (*rit) != curr; rit++)
1316 /* go past curr now */
1319 action_list_t::reverse_iterator ritcopy = rit;
1320 //See if we have enough reads from the same value
1322 for (; count < params.maxreads; rit++,count++) {
1323 if (rit==list->rend())
1325 ModelAction *act = *rit;
1326 if (!act->is_read())
1329 if (act->get_reads_from() != rf)
1331 if (act->get_node()->get_read_from_size() <= 1)
1334 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1336 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1338 //Need a different write
1342 /* Test to see whether this is a feasible write to read from*/
1343 mo_graph->startChanges();
1344 r_modification_order(curr, write);
1345 bool feasiblereadfrom = !is_infeasible();
1346 mo_graph->rollbackChanges();
1348 if (!feasiblereadfrom)
1352 bool feasiblewrite = true;
1353 //new we need to see if this write works for everyone
1355 for (int loop = count; loop>0; loop--,rit++) {
1356 ModelAction *act=*rit;
1357 bool foundvalue = false;
1358 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1359 if (act->get_node()->get_read_from_at(j)==write) {
1365 feasiblewrite = false;
1369 if (feasiblewrite) {
1370 priv->too_many_reads = true;
1378 * Updates the mo_graph with the constraints imposed from the current
1381 * Basic idea is the following: Go through each other thread and find
1382 * the lastest action that happened before our read. Two cases:
1384 * (1) The action is a write => that write must either occur before
1385 * the write we read from or be the write we read from.
1387 * (2) The action is a read => the write that that action read from
1388 * must occur before the write we read from or be the same write.
1390 * @param curr The current action. Must be a read.
1391 * @param rf The action that curr reads from. Must be a write.
1392 * @return True if modification order edges were added; false otherwise
1394 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1396 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1399 ASSERT(curr->is_read());
1401 /* Iterate over all threads */
1402 for (i = 0; i < thrd_lists->size(); i++) {
1403 /* Iterate over actions in thread, starting from most recent */
1404 action_list_t *list = &(*thrd_lists)[i];
1405 action_list_t::reverse_iterator rit;
1406 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1407 ModelAction *act = *rit;
1410 * Include at most one act per-thread that "happens
1411 * before" curr. Don't consider reflexively.
1413 if (act->happens_before(curr) && act != curr) {
1414 if (act->is_write()) {
1416 mo_graph->addEdge(act, rf);
1420 const ModelAction *prevreadfrom = act->get_reads_from();
1421 //if the previous read is unresolved, keep going...
1422 if (prevreadfrom == NULL)
1425 if (rf != prevreadfrom) {
1426 mo_graph->addEdge(prevreadfrom, rf);
1438 /** This method fixes up the modification order when we resolve a
1439 * promises. The basic problem is that actions that occur after the
1440 * read curr could not property add items to the modification order
1443 * So for each thread, we find the earliest item that happens after
1444 * the read curr. This is the item we have to fix up with additional
1445 * constraints. If that action is write, we add a MO edge between
1446 * the Action rf and that action. If the action is a read, we add a
1447 * MO edge between the Action rf, and whatever the read accessed.
1449 * @param curr is the read ModelAction that we are fixing up MO edges for.
1450 * @param rf is the write ModelAction that curr reads from.
1453 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1455 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1457 ASSERT(curr->is_read());
1459 /* Iterate over all threads */
1460 for (i = 0; i < thrd_lists->size(); i++) {
1461 /* Iterate over actions in thread, starting from most recent */
1462 action_list_t *list = &(*thrd_lists)[i];
1463 action_list_t::reverse_iterator rit;
1464 ModelAction *lastact = NULL;
1466 /* Find last action that happens after curr that is either not curr or a rmw */
1467 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1468 ModelAction *act = *rit;
1469 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1475 /* Include at most one act per-thread that "happens before" curr */
1476 if (lastact != NULL) {
1477 if (lastact==curr) {
1478 //Case 1: The resolved read is a RMW, and we need to make sure
1479 //that the write portion of the RMW mod order after rf
1481 mo_graph->addEdge(rf, lastact);
1482 } else if (lastact->is_read()) {
1483 //Case 2: The resolved read is a normal read and the next
1484 //operation is a read, and we need to make sure the value read
1485 //is mod ordered after rf
1487 const ModelAction *postreadfrom = lastact->get_reads_from();
1488 if (postreadfrom != NULL&&rf != postreadfrom)
1489 mo_graph->addEdge(rf, postreadfrom);
1491 //Case 3: The resolved read is a normal read and the next
1492 //operation is a write, and we need to make sure that the
1493 //write is mod ordered after rf
1495 mo_graph->addEdge(rf, lastact);
1503 * Updates the mo_graph with the constraints imposed from the current write.
1505 * Basic idea is the following: Go through each other thread and find
1506 * the lastest action that happened before our write. Two cases:
1508 * (1) The action is a write => that write must occur before
1511 * (2) The action is a read => the write that that action read from
1512 * must occur before the current write.
1514 * This method also handles two other issues:
1516 * (I) Sequential Consistency: Making sure that if the current write is
1517 * seq_cst, that it occurs after the previous seq_cst write.
1519 * (II) Sending the write back to non-synchronizing reads.
1521 * @param curr The current action. Must be a write.
1522 * @return True if modification order edges were added; false otherwise
1524 bool ModelChecker::w_modification_order(ModelAction *curr)
1526 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1529 ASSERT(curr->is_write());
1531 if (curr->is_seqcst()) {
1532 /* We have to at least see the last sequentially consistent write,
1533 so we are initialized. */
1534 ModelAction *last_seq_cst = get_last_seq_cst(curr);
1535 if (last_seq_cst != NULL) {
1536 mo_graph->addEdge(last_seq_cst, curr);
1541 /* Iterate over all threads */
1542 for (i = 0; i < thrd_lists->size(); i++) {
1543 /* Iterate over actions in thread, starting from most recent */
1544 action_list_t *list = &(*thrd_lists)[i];
1545 action_list_t::reverse_iterator rit;
1546 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1547 ModelAction *act = *rit;
1550 * 1) If RMW and it actually read from something, then we
1551 * already have all relevant edges, so just skip to next
1554 * 2) If RMW and it didn't read from anything, we should
1555 * whatever edge we can get to speed up convergence.
1557 * 3) If normal write, we need to look at earlier actions, so
1558 * continue processing list.
1560 if (curr->is_rmw()) {
1561 if (curr->get_reads_from()!=NULL)
1570 * Include at most one act per-thread that "happens
1573 if (act->happens_before(curr)) {
1575 * Note: if act is RMW, just add edge:
1577 * The following edge should be handled elsewhere:
1578 * readfrom(act) --mo--> act
1580 if (act->is_write())
1581 mo_graph->addEdge(act, curr);
1582 else if (act->is_read()) {
1583 //if previous read accessed a null, just keep going
1584 if (act->get_reads_from() == NULL)
1586 mo_graph->addEdge(act->get_reads_from(), curr);
1590 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1591 !act->same_thread(curr)) {
1592 /* We have an action that:
1593 (1) did not happen before us
1594 (2) is a read and we are a write
1595 (3) cannot synchronize with us
1596 (4) is in a different thread
1598 that read could potentially read from our write. Note that
1599 these checks are overly conservative at this point, we'll
1600 do more checks before actually removing the
1604 if (thin_air_constraint_may_allow(curr, act)) {
1605 if (!is_infeasible() ||
1606 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1607 struct PendingFutureValue pfv = {curr,act};
1608 futurevalues->push_back(pfv);
1618 /** Arbitrary reads from the future are not allowed. Section 29.3
1619 * part 9 places some constraints. This method checks one result of constraint
1620 * constraint. Others require compiler support. */
1621 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1622 if (!writer->is_rmw())
1625 if (!reader->is_rmw())
1628 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1629 if (search == reader)
1631 if (search->get_tid() == reader->get_tid() &&
1632 search->happens_before(reader))
1640 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1641 * some constraints. This method checks one the following constraint (others
1642 * require compiler support):
1644 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1646 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1648 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1650 /* Iterate over all threads */
1651 for (i = 0; i < thrd_lists->size(); i++) {
1652 const ModelAction *write_after_read = NULL;
1654 /* Iterate over actions in thread, starting from most recent */
1655 action_list_t *list = &(*thrd_lists)[i];
1656 action_list_t::reverse_iterator rit;
1657 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1658 ModelAction *act = *rit;
1660 if (!reader->happens_before(act))
1662 else if (act->is_write())
1663 write_after_read = act;
1664 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1665 write_after_read = act->get_reads_from();
1669 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1676 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1677 * The ModelAction under consideration is expected to be taking part in
1678 * release/acquire synchronization as an object of the "reads from" relation.
1679 * Note that this can only provide release sequence support for RMW chains
1680 * which do not read from the future, as those actions cannot be traced until
1681 * their "promise" is fulfilled. Similarly, we may not even establish the
1682 * presence of a release sequence with certainty, as some modification order
1683 * constraints may be decided further in the future. Thus, this function
1684 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1685 * and a boolean representing certainty.
1687 * @param rf The action that might be part of a release sequence. Must be a
1689 * @param release_heads A pass-by-reference style return parameter. After
1690 * execution of this function, release_heads will contain the heads of all the
1691 * relevant release sequences, if any exists with certainty
1692 * @param pending A pass-by-reference style return parameter which is only used
1693 * when returning false (i.e., uncertain). Returns most information regarding
1694 * an uncertain release sequence, including any write operations that might
1695 * break the sequence.
1696 * @return true, if the ModelChecker is certain that release_heads is complete;
1699 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1700 rel_heads_list_t *release_heads,
1701 struct release_seq *pending) const
1703 /* Only check for release sequences if there are no cycles */
1704 if (mo_graph->checkForCycles())
1708 ASSERT(rf->is_write());
1710 if (rf->is_release())
1711 release_heads->push_back(rf);
1713 break; /* End of RMW chain */
1715 /** @todo Need to be smarter here... In the linux lock
1716 * example, this will run to the beginning of the program for
1718 /** @todo The way to be smarter here is to keep going until 1
1719 * thread has a release preceded by an acquire and you've seen
1722 /* acq_rel RMW is a sufficient stopping condition */
1723 if (rf->is_acquire() && rf->is_release())
1724 return true; /* complete */
1726 rf = rf->get_reads_from();
1729 /* read from future: need to settle this later */
1731 return false; /* incomplete */
1734 if (rf->is_release())
1735 return true; /* complete */
1737 /* else relaxed write; check modification order for contiguous subsequence
1738 * -> rf must be same thread as release */
1739 int tid = id_to_int(rf->get_tid());
1740 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1741 action_list_t *list = &(*thrd_lists)[tid];
1742 action_list_t::const_reverse_iterator rit;
1744 /* Find rf in the thread list */
1745 rit = std::find(list->rbegin(), list->rend(), rf);
1746 ASSERT(rit != list->rend());
1748 /* Find the last write/release */
1749 for (; rit != list->rend(); rit++)
1750 if ((*rit)->is_release())
1752 if (rit == list->rend()) {
1753 /* No write-release in this thread */
1754 return true; /* complete */
1756 ModelAction *release = *rit;
1758 ASSERT(rf->same_thread(release));
1760 pending->writes.clear();
1762 bool certain = true;
1763 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1764 if (id_to_int(rf->get_tid()) == (int)i)
1766 list = &(*thrd_lists)[i];
1768 /* Can we ensure no future writes from this thread may break
1769 * the release seq? */
1770 bool future_ordered = false;
1772 ModelAction *last = get_last_action(int_to_id(i));
1773 Thread *th = get_thread(int_to_id(i));
1774 if ((last && rf->happens_before(last)) ||
1777 future_ordered = true;
1779 ASSERT(!th->is_model_thread() || future_ordered);
1781 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1782 const ModelAction *act = *rit;
1783 /* Reach synchronization -> this thread is complete */
1784 if (act->happens_before(release))
1786 if (rf->happens_before(act)) {
1787 future_ordered = true;
1791 /* Only non-RMW writes can break release sequences */
1792 if (!act->is_write() || act->is_rmw())
1795 /* Check modification order */
1796 if (mo_graph->checkReachable(rf, act)) {
1797 /* rf --mo--> act */
1798 future_ordered = true;
1801 if (mo_graph->checkReachable(act, release))
1802 /* act --mo--> release */
1804 if (mo_graph->checkReachable(release, act) &&
1805 mo_graph->checkReachable(act, rf)) {
1806 /* release --mo-> act --mo--> rf */
1807 return true; /* complete */
1809 /* act may break release sequence */
1810 pending->writes.push_back(act);
1813 if (!future_ordered)
1814 certain = false; /* This thread is uncertain */
1818 release_heads->push_back(release);
1819 pending->writes.clear();
1821 pending->release = release;
1828 * A public interface for getting the release sequence head(s) with which a
1829 * given ModelAction must synchronize. This function only returns a non-empty
1830 * result when it can locate a release sequence head with certainty. Otherwise,
1831 * it may mark the internal state of the ModelChecker so that it will handle
1832 * the release sequence at a later time, causing @a act to update its
1833 * synchronization at some later point in execution.
1834 * @param act The 'acquire' action that may read from a release sequence
1835 * @param release_heads A pass-by-reference return parameter. Will be filled
1836 * with the head(s) of the release sequence(s), if they exists with certainty.
1837 * @see ModelChecker::release_seq_heads
1839 void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
1841 const ModelAction *rf = act->get_reads_from();
1842 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
1843 sequence->acquire = act;
1845 if (!release_seq_heads(rf, release_heads, sequence)) {
1846 /* add act to 'lazy checking' list */
1847 pending_rel_seqs->push_back(sequence);
1849 snapshot_free(sequence);
1854 * Attempt to resolve all stashed operations that might synchronize with a
1855 * release sequence for a given location. This implements the "lazy" portion of
1856 * determining whether or not a release sequence was contiguous, since not all
1857 * modification order information is present at the time an action occurs.
1859 * @param location The location/object that should be checked for release
1860 * sequence resolutions. A NULL value means to check all locations.
1861 * @param work_queue The work queue to which to add work items as they are
1863 * @return True if any updates occurred (new synchronization, new mo_graph
1866 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
1868 bool updated = false;
1869 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
1870 while (it != pending_rel_seqs->end()) {
1871 struct release_seq *pending = *it;
1872 ModelAction *act = pending->acquire;
1874 /* Only resolve sequences on the given location, if provided */
1875 if (location && act->get_location() != location) {
1880 const ModelAction *rf = act->get_reads_from();
1881 rel_heads_list_t release_heads;
1883 complete = release_seq_heads(rf, &release_heads, pending);
1884 for (unsigned int i = 0; i < release_heads.size(); i++) {
1885 if (!act->has_synchronized_with(release_heads[i])) {
1886 if (act->synchronize_with(release_heads[i]))
1889 set_bad_synchronization();
1894 /* Re-check all pending release sequences */
1895 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1896 /* Re-check act for mo_graph edges */
1897 work_queue->push_back(MOEdgeWorkEntry(act));
1899 /* propagate synchronization to later actions */
1900 action_list_t::reverse_iterator rit = action_trace->rbegin();
1901 for (; (*rit) != act; rit++) {
1902 ModelAction *propagate = *rit;
1903 if (act->happens_before(propagate)) {
1904 propagate->synchronize_with(act);
1905 /* Re-check 'propagate' for mo_graph edges */
1906 work_queue->push_back(MOEdgeWorkEntry(propagate));
1911 it = pending_rel_seqs->erase(it);
1912 snapshot_free(pending);
1918 // If we resolved promises or data races, see if we have realized a data race.
1925 * Performs various bookkeeping operations for the current ModelAction. For
1926 * instance, adds action to the per-object, per-thread action vector and to the
1927 * action trace list of all thread actions.
1929 * @param act is the ModelAction to add.
1931 void ModelChecker::add_action_to_lists(ModelAction *act)
1933 int tid = id_to_int(act->get_tid());
1934 action_trace->push_back(act);
1936 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
1938 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
1939 if (tid >= (int)vec->size())
1940 vec->resize(priv->next_thread_id);
1941 (*vec)[tid].push_back(act);
1943 if ((int)thrd_last_action->size() <= tid)
1944 thrd_last_action->resize(get_num_threads());
1945 (*thrd_last_action)[tid] = act;
1947 if (act->is_wait()) {
1948 void *mutex_loc=(void *) act->get_value();
1949 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
1951 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
1952 if (tid >= (int)vec->size())
1953 vec->resize(priv->next_thread_id);
1954 (*vec)[tid].push_back(act);
1956 if ((int)thrd_last_action->size() <= tid)
1957 thrd_last_action->resize(get_num_threads());
1958 (*thrd_last_action)[tid] = act;
1963 * @brief Get the last action performed by a particular Thread
1964 * @param tid The thread ID of the Thread in question
1965 * @return The last action in the thread
1967 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
1969 int threadid = id_to_int(tid);
1970 if (threadid < (int)thrd_last_action->size())
1971 return (*thrd_last_action)[id_to_int(tid)];
1977 * Gets the last memory_order_seq_cst write (in the total global sequence)
1978 * performed on a particular object (i.e., memory location), not including the
1980 * @param curr The current ModelAction; also denotes the object location to
1982 * @return The last seq_cst write
1984 ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const
1986 void *location = curr->get_location();
1987 action_list_t *list = get_safe_ptr_action(obj_map, location);
1988 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1989 action_list_t::reverse_iterator rit;
1990 for (rit = list->rbegin(); rit != list->rend(); rit++)
1991 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
1997 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1998 * location). This function identifies the mutex according to the current
1999 * action, which is presumed to perform on the same mutex.
2000 * @param curr The current ModelAction; also denotes the object location to
2002 * @return The last unlock operation
2004 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2006 void *location = curr->get_location();
2007 action_list_t *list = get_safe_ptr_action(obj_map, location);
2008 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2009 action_list_t::reverse_iterator rit;
2010 for (rit = list->rbegin(); rit != list->rend(); rit++)
2011 if ((*rit)->is_unlock() || (*rit)->is_wait())
2016 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
2018 ModelAction *parent = get_last_action(tid);
2020 parent = get_thread(tid)->get_creation();
2025 * Returns the clock vector for a given thread.
2026 * @param tid The thread whose clock vector we want
2027 * @return Desired clock vector
2029 ClockVector * ModelChecker::get_cv(thread_id_t tid)
2031 return get_parent_action(tid)->get_cv();
2035 * Resolve a set of Promises with a current write. The set is provided in the
2036 * Node corresponding to @a write.
2037 * @param write The ModelAction that is fulfilling Promises
2038 * @return True if promises were resolved; false otherwise
2040 bool ModelChecker::resolve_promises(ModelAction *write)
2042 bool resolved = false;
2043 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2045 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2046 Promise *promise = (*promises)[promise_index];
2047 if (write->get_node()->get_promise(i)) {
2048 ModelAction *read = promise->get_action();
2049 if (read->is_rmw()) {
2050 mo_graph->addRMWEdge(write, read);
2052 read->read_from(write);
2053 //First fix up the modification order for actions that happened
2055 r_modification_order(read, write);
2056 //Next fix up the modification order for actions that happened
2058 post_r_modification_order(read, write);
2059 //Make sure the promise's value matches the write's value
2060 ASSERT(promise->get_value() == write->get_value());
2063 promises->erase(promises->begin() + promise_index);
2064 threads_to_check.push_back(read->get_tid());
2071 //Check whether reading these writes has made threads unable to
2074 for(unsigned int i=0;i<threads_to_check.size();i++)
2075 mo_check_promises(threads_to_check[i], write);
2081 * Compute the set of promises that could potentially be satisfied by this
2082 * action. Note that the set computation actually appears in the Node, not in
2084 * @param curr The ModelAction that may satisfy promises
2086 void ModelChecker::compute_promises(ModelAction *curr)
2088 for (unsigned int i = 0; i < promises->size(); i++) {
2089 Promise *promise = (*promises)[i];
2090 const ModelAction *act = promise->get_action();
2091 if (!act->happens_before(curr) &&
2093 !act->could_synchronize_with(curr) &&
2094 !act->same_thread(curr) &&
2095 act->get_location() == curr->get_location() &&
2096 promise->get_value() == curr->get_value()) {
2097 curr->get_node()->set_promise(i, act->is_rmw());
2102 /** Checks promises in response to change in ClockVector Threads. */
2103 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2105 for (unsigned int i = 0; i < promises->size(); i++) {
2106 Promise *promise = (*promises)[i];
2107 const ModelAction *act = promise->get_action();
2108 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2109 merge_cv->synchronized_since(act)) {
2110 if (promise->increment_threads(tid)) {
2111 //Promise has failed
2112 priv->failed_promise = true;
2119 void ModelChecker::check_promises_thread_disabled() {
2120 for (unsigned int i = 0; i < promises->size(); i++) {
2121 Promise *promise = (*promises)[i];
2122 if (promise->check_promise()) {
2123 priv->failed_promise = true;
2129 /** Checks promises in response to addition to modification order for threads.
2131 * pthread is the thread that performed the read that created the promise
2133 * pread is the read that created the promise
2135 * pwrite is either the first write to same location as pread by
2136 * pthread that is sequenced after pread or the value read by the
2137 * first read to the same lcoation as pread by pthread that is
2138 * sequenced after pread..
2140 * 1. If tid=pthread, then we check what other threads are reachable
2141 * through the mode order starting with pwrite. Those threads cannot
2142 * perform a write that will resolve the promise due to modification
2143 * order constraints.
2145 * 2. If the tid is not pthread, we check whether pwrite can reach the
2146 * action write through the modification order. If so, that thread
2147 * cannot perform a future write that will resolve the promise due to
2148 * modificatin order constraints.
2150 * @parem tid The thread that either read from the model action
2151 * write, or actually did the model action write.
2153 * @parem write The ModelAction representing the relevant write.
2156 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2157 void * location = write->get_location();
2158 for (unsigned int i = 0; i < promises->size(); i++) {
2159 Promise *promise = (*promises)[i];
2160 const ModelAction *act = promise->get_action();
2162 //Is this promise on the same location?
2163 if ( act->get_location() != location )
2166 //same thread as the promise
2167 if ( act->get_tid()==tid ) {
2169 //do we have a pwrite for the promise, if not, set it
2170 if (promise->get_write() == NULL ) {
2171 promise->set_write(write);
2172 //The pwrite cannot happen before the promise
2173 if (write->happens_before(act) && (write != act)) {
2174 priv->failed_promise = true;
2178 if (mo_graph->checkPromise(write, promise)) {
2179 priv->failed_promise = true;
2184 //Don't do any lookups twice for the same thread
2185 if (promise->has_sync_thread(tid))
2188 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2189 if (promise->increment_threads(tid)) {
2190 priv->failed_promise = true;
2198 * Compute the set of writes that may break the current pending release
2199 * sequence. This information is extracted from previou release sequence
2202 * @param curr The current ModelAction. Must be a release sequence fixup
2205 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2207 if (pending_rel_seqs->empty())
2210 struct release_seq *pending = pending_rel_seqs->back();
2211 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2212 const ModelAction *write = pending->writes[i];
2213 curr->get_node()->add_relseq_break(write);
2216 /* NULL means don't break the sequence; just synchronize */
2217 curr->get_node()->add_relseq_break(NULL);
2221 * Build up an initial set of all past writes that this 'read' action may read
2222 * from. This set is determined by the clock vector's "happens before"
2224 * @param curr is the current ModelAction that we are exploring; it must be a
2227 void ModelChecker::build_reads_from_past(ModelAction *curr)
2229 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2231 ASSERT(curr->is_read());
2233 ModelAction *last_seq_cst = NULL;
2235 /* Track whether this object has been initialized */
2236 bool initialized = false;
2238 if (curr->is_seqcst()) {
2239 last_seq_cst = get_last_seq_cst(curr);
2240 /* We have to at least see the last sequentially consistent write,
2241 so we are initialized. */
2242 if (last_seq_cst != NULL)
2246 /* Iterate over all threads */
2247 for (i = 0; i < thrd_lists->size(); i++) {
2248 /* Iterate over actions in thread, starting from most recent */
2249 action_list_t *list = &(*thrd_lists)[i];
2250 action_list_t::reverse_iterator rit;
2251 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2252 ModelAction *act = *rit;
2254 /* Only consider 'write' actions */
2255 if (!act->is_write() || act == curr)
2258 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2259 if (!curr->is_seqcst() || (!act->is_seqcst() && (last_seq_cst == NULL || !act->happens_before(last_seq_cst))) || act == last_seq_cst) {
2260 if (!curr->get_sleep_flag() || curr->is_seqcst() || sleep_can_read_from(curr, act)) {
2261 DEBUG("Adding action to may_read_from:\n");
2262 if (DBG_ENABLED()) {
2266 curr->get_node()->add_read_from(act);
2270 /* Include at most one act per-thread that "happens before" curr */
2271 if (act->happens_before(curr)) {
2279 assert_bug("May read from uninitialized atomic");
2281 if (DBG_ENABLED() || !initialized) {
2282 model_print("Reached read action:\n");
2284 model_print("Printing may_read_from\n");
2285 curr->get_node()->print_may_read_from();
2286 model_print("End printing may_read_from\n");
2290 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2292 Node *prevnode=write->get_node()->get_parent();
2294 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2295 if (write->is_release()&&thread_sleep)
2297 if (!write->is_rmw()) {
2300 if (write->get_reads_from()==NULL)
2302 write=write->get_reads_from();
2306 static void print_list(action_list_t *list, int exec_num = -1)
2308 action_list_t::iterator it;
2310 model_print("---------------------------------------------------------------------\n");
2312 model_print("Execution %d:\n", exec_num);
2314 unsigned int hash=0;
2316 for (it = list->begin(); it != list->end(); it++) {
2318 hash=hash^(hash<<3)^((*it)->hash());
2320 model_print("HASH %u\n", hash);
2321 model_print("---------------------------------------------------------------------\n");
2324 #if SUPPORT_MOD_ORDER_DUMP
2325 void ModelChecker::dumpGraph(char *filename) {
2327 sprintf(buffer, "%s.dot",filename);
2328 FILE *file=fopen(buffer, "w");
2329 fprintf(file, "digraph %s {\n",filename);
2330 mo_graph->dumpNodes(file);
2331 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2333 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2334 ModelAction *action=*it;
2335 if (action->is_read()) {
2336 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2337 if (action->get_reads_from()!=NULL)
2338 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2340 if (thread_array[action->get_tid()] != NULL) {
2341 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2344 thread_array[action->get_tid()]=action;
2346 fprintf(file,"}\n");
2347 model_free(thread_array);
2352 /** @brief Prints an execution trace summary. */
2353 void ModelChecker::print_summary() const
2355 #if SUPPORT_MOD_ORDER_DUMP
2357 char buffername[100];
2358 sprintf(buffername, "exec%04u", stats.num_total);
2359 mo_graph->dumpGraphToFile(buffername);
2360 sprintf(buffername, "graph%04u", stats.num_total);
2361 dumpGraph(buffername);
2364 if (!isfeasibleprefix())
2365 model_print("INFEASIBLE EXECUTION!\n");
2366 print_list(action_trace, stats.num_total);
2371 * Add a Thread to the system for the first time. Should only be called once
2373 * @param t The Thread to add
2375 void ModelChecker::add_thread(Thread *t)
2377 thread_map->put(id_to_int(t->get_id()), t);
2378 scheduler->add_thread(t);
2382 * Removes a thread from the scheduler.
2383 * @param the thread to remove.
2385 void ModelChecker::remove_thread(Thread *t)
2387 scheduler->remove_thread(t);
2391 * @brief Get a Thread reference by its ID
2392 * @param tid The Thread's ID
2393 * @return A Thread reference
2395 Thread * ModelChecker::get_thread(thread_id_t tid) const
2397 return thread_map->get(id_to_int(tid));
2401 * @brief Get a reference to the Thread in which a ModelAction was executed
2402 * @param act The ModelAction
2403 * @return A Thread reference
2405 Thread * ModelChecker::get_thread(ModelAction *act) const
2407 return get_thread(act->get_tid());
2411 * @brief Check if a Thread is currently enabled
2412 * @param t The Thread to check
2413 * @return True if the Thread is currently enabled
2415 bool ModelChecker::is_enabled(Thread *t) const
2417 return scheduler->is_enabled(t);
2421 * @brief Check if a Thread is currently enabled
2422 * @param tid The ID of the Thread to check
2423 * @return True if the Thread is currently enabled
2425 bool ModelChecker::is_enabled(thread_id_t tid) const
2427 return scheduler->is_enabled(tid);
2431 * Switch from a user-context to the "master thread" context (a.k.a. system
2432 * context). This switch is made with the intention of exploring a particular
2433 * model-checking action (described by a ModelAction object). Must be called
2434 * from a user-thread context.
2436 * @param act The current action that will be explored. May be NULL only if
2437 * trace is exiting via an assertion (see ModelChecker::set_assert and
2438 * ModelChecker::has_asserted).
2439 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2441 int ModelChecker::switch_to_master(ModelAction *act)
2444 Thread *old = thread_current();
2445 set_current_action(act);
2446 old->set_state(THREAD_READY);
2447 return Thread::swap(old, &system_context);
2451 * Takes the next step in the execution, if possible.
2452 * @return Returns true (success) if a step was taken and false otherwise.
2454 bool ModelChecker::take_step() {
2458 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2460 if (curr->get_state() == THREAD_READY) {
2461 ASSERT(priv->current_action);
2463 priv->nextThread = check_current_action(priv->current_action);
2464 priv->current_action = NULL;
2466 if (curr->is_blocked() || curr->is_complete())
2467 scheduler->remove_thread(curr);
2472 Thread *next = scheduler->next_thread(priv->nextThread);
2474 /* Infeasible -> don't take any more steps */
2475 if (is_infeasible())
2477 else if (isfeasibleprefix() && have_bug_reports()) {
2482 if (params.bound != 0) {
2483 if (priv->used_sequence_numbers > params.bound) {
2488 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2489 next ? id_to_int(next->get_id()) : -1);
2492 * Launch end-of-execution release sequence fixups only when there are:
2494 * (1) no more user threads to run (or when execution replay chooses
2495 * the 'model_thread')
2496 * (2) pending release sequences
2497 * (3) pending assertions (i.e., data races)
2498 * (4) no pending promises
2500 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2501 isfinalfeasible() && !unrealizedraces.empty()) {
2502 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2503 pending_rel_seqs->size());
2504 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2505 std::memory_order_seq_cst, NULL, VALUE_NONE,
2507 set_current_action(fixup);
2511 /* next == NULL -> don't take any more steps */
2515 next->set_state(THREAD_RUNNING);
2517 if (next->get_pending() != NULL) {
2518 /* restart a pending action */
2519 set_current_action(next->get_pending());
2520 next->set_pending(NULL);
2521 next->set_state(THREAD_READY);
2525 /* Return false only if swap fails with an error */
2526 return (Thread::swap(&system_context, next) == 0);
2529 /** Wrapper to run the user's main function, with appropriate arguments */
2530 void user_main_wrapper(void *)
2532 user_main(model->params.argc, model->params.argv);
2535 /** @brief Run ModelChecker for the user program */
2536 void ModelChecker::run()
2541 /* Start user program */
2542 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2544 /* Wait for all threads to complete */
2545 while (take_step());
2546 } while (next_execution());