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 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
95 node_stack(new NodeStack()),
96 priv(new struct model_snapshot_members()),
97 mo_graph(new CycleGraph())
99 /* Initialize a model-checker thread, for special ModelActions */
100 model_thread = new Thread(get_next_id());
101 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
104 /** @brief Destructor */
105 ModelChecker::~ModelChecker()
107 for (unsigned int i = 0; i < get_num_threads(); i++)
108 delete thread_map->get(i);
113 delete lock_waiters_map;
114 delete condvar_waiters_map;
117 for (unsigned int i = 0; i < promises->size(); i++)
118 delete (*promises)[i];
121 delete pending_rel_seqs;
123 delete thrd_last_action;
124 delete thrd_last_fence_release;
131 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr) {
132 action_list_t * tmp=hash->get(ptr);
134 tmp=new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr) {
141 std::vector<action_list_t> * tmp=hash->get(ptr);
143 tmp=new std::vector<action_list_t>();
150 * Restores user program to initial state and resets all model-checker data
153 void ModelChecker::reset_to_initial_state()
155 DEBUG("+++ Resetting to initial state +++\n");
156 node_stack->reset_execution();
158 /* Print all model-checker output before rollback */
161 snapshotObject->backTrackBeforeStep(0);
164 /** @return a thread ID for a new Thread */
165 thread_id_t ModelChecker::get_next_id()
167 return priv->next_thread_id++;
170 /** @return the number of user threads created during this execution */
171 unsigned int ModelChecker::get_num_threads() const
173 return priv->next_thread_id;
176 /** @return The currently executing Thread. */
177 Thread * ModelChecker::get_current_thread() const
179 return scheduler->get_current_thread();
182 /** @return a sequence number for a new ModelAction */
183 modelclock_t ModelChecker::get_next_seq_num()
185 return ++priv->used_sequence_numbers;
188 Node * ModelChecker::get_curr_node() const
190 return node_stack->get_head();
194 * @brief Choose the next thread to execute.
196 * This function chooses the next thread that should execute. It can force the
197 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
198 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
199 * The model-checker may have no preference regarding the next thread (i.e.,
200 * when exploring a new execution ordering), in which case this will return
202 * @param curr The current ModelAction. This action might guide the choice of
204 * @return The next thread to run. If the model-checker has no preference, NULL.
206 Thread * ModelChecker::get_next_thread(ModelAction *curr)
211 /* Do not split atomic actions. */
213 return thread_current();
214 /* The THREAD_CREATE action points to the created Thread */
215 else if (curr->get_type() == THREAD_CREATE)
216 return (Thread *)curr->get_location();
219 /* Have we completed exploring the preselected path? */
223 /* Else, we are trying to replay an execution */
224 ModelAction *next = node_stack->get_next()->get_action();
226 if (next == diverge) {
227 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
228 earliest_diverge=diverge;
230 Node *nextnode = next->get_node();
231 Node *prevnode = nextnode->get_parent();
232 scheduler->update_sleep_set(prevnode);
234 /* Reached divergence point */
235 if (nextnode->increment_misc()) {
236 /* The next node will try to satisfy a different misc_index values. */
237 tid = next->get_tid();
238 node_stack->pop_restofstack(2);
239 } else if (nextnode->increment_promise()) {
240 /* The next node will try to satisfy a different set of promises. */
241 tid = next->get_tid();
242 node_stack->pop_restofstack(2);
243 } else if (nextnode->increment_read_from()) {
244 /* The next node will read from a different value. */
245 tid = next->get_tid();
246 node_stack->pop_restofstack(2);
247 } else if (nextnode->increment_future_value()) {
248 /* The next node will try to read from a different future value. */
249 tid = next->get_tid();
250 node_stack->pop_restofstack(2);
251 } else if (nextnode->increment_relseq_break()) {
252 /* The next node will try to resolve a release sequence differently */
253 tid = next->get_tid();
254 node_stack->pop_restofstack(2);
256 /* Make a different thread execute for next step */
257 scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid())));
258 tid = prevnode->get_next_backtrack();
259 /* Make sure the backtracked thread isn't sleeping. */
260 node_stack->pop_restofstack(1);
261 if (diverge==earliest_diverge) {
262 earliest_diverge=prevnode->get_action();
265 /* The correct sleep set is in the parent node. */
268 DEBUG("*** Divergence point ***\n");
272 tid = next->get_tid();
274 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
275 ASSERT(tid != THREAD_ID_T_NONE);
276 return thread_map->get(id_to_int(tid));
280 * We need to know what the next actions of all threads in the sleep
281 * set will be. This method computes them and stores the actions at
282 * the corresponding thread object's pending action.
285 void ModelChecker::execute_sleep_set() {
286 for(unsigned int i=0;i<get_num_threads();i++) {
287 thread_id_t tid=int_to_id(i);
288 Thread *thr=get_thread(tid);
289 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET &&
290 thr->get_pending() == NULL ) {
291 thr->set_state(THREAD_RUNNING);
292 scheduler->next_thread(thr);
293 Thread::swap(&system_context, thr);
294 priv->current_action->set_sleep_flag();
295 thr->set_pending(priv->current_action);
298 priv->current_action = NULL;
301 void ModelChecker::wake_up_sleeping_actions(ModelAction * curr) {
302 for(unsigned int i=0;i<get_num_threads();i++) {
303 thread_id_t tid=int_to_id(i);
304 Thread *thr=get_thread(tid);
305 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
306 ModelAction *pending_act=thr->get_pending();
307 if ((!curr->is_rmwr())&&pending_act->could_synchronize_with(curr)) {
308 //Remove this thread from sleep set
309 scheduler->remove_sleep(thr);
315 /** @brief Alert the model-checker that an incorrectly-ordered
316 * synchronization was made */
317 void ModelChecker::set_bad_synchronization()
319 priv->bad_synchronization = true;
322 bool ModelChecker::has_asserted() const
324 return priv->asserted;
327 void ModelChecker::set_assert()
329 priv->asserted = true;
333 * Check if we are in a deadlock. Should only be called at the end of an
334 * execution, although it should not give false positives in the middle of an
335 * execution (there should be some ENABLED thread).
337 * @return True if program is in a deadlock; false otherwise
339 bool ModelChecker::is_deadlocked() const
341 bool blocking_threads = false;
342 for (unsigned int i = 0; i < get_num_threads(); i++) {
343 thread_id_t tid = int_to_id(i);
346 Thread *t = get_thread(tid);
347 if (!t->is_model_thread() && t->get_pending())
348 blocking_threads = true;
350 return blocking_threads;
354 * Check if this is a complete execution. That is, have all thread completed
355 * execution (rather than exiting because sleep sets have forced a redundant
358 * @return True if the execution is complete.
360 bool ModelChecker::is_complete_execution() const
362 for (unsigned int i = 0; i < get_num_threads(); i++)
363 if (is_enabled(int_to_id(i)))
369 * @brief Assert a bug in the executing program.
371 * Use this function to assert any sort of bug in the user program. If the
372 * current trace is feasible (actually, a prefix of some feasible execution),
373 * then this execution will be aborted, printing the appropriate message. If
374 * the current trace is not yet feasible, the error message will be stashed and
375 * printed if the execution ever becomes feasible.
377 * @param msg Descriptive message for the bug (do not include newline char)
378 * @return True if bug is immediately-feasible
380 bool ModelChecker::assert_bug(const char *msg)
382 priv->bugs.push_back(new bug_message(msg));
384 if (isfeasibleprefix()) {
392 * @brief Assert a bug in the executing program, asserted by a user thread
393 * @see ModelChecker::assert_bug
394 * @param msg Descriptive message for the bug (do not include newline char)
396 void ModelChecker::assert_user_bug(const char *msg)
398 /* If feasible bug, bail out now */
400 switch_to_master(NULL);
403 /** @return True, if any bugs have been reported for this execution */
404 bool ModelChecker::have_bug_reports() const
406 return priv->bugs.size() != 0;
409 /** @brief Print bug report listing for this execution (if any bugs exist) */
410 void ModelChecker::print_bugs() const
412 if (have_bug_reports()) {
413 model_print("Bug report: %zu bug%s detected\n",
415 priv->bugs.size() > 1 ? "s" : "");
416 for (unsigned int i = 0; i < priv->bugs.size(); i++)
417 priv->bugs[i]->print();
422 * @brief Record end-of-execution stats
424 * Must be run when exiting an execution. Records various stats.
425 * @see struct execution_stats
427 void ModelChecker::record_stats()
430 if (!isfeasibleprefix())
431 stats.num_infeasible++;
432 else if (have_bug_reports())
433 stats.num_buggy_executions++;
434 else if (is_complete_execution())
435 stats.num_complete++;
437 stats.num_redundant++;
440 /** @brief Print execution stats */
441 void ModelChecker::print_stats() const
443 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
444 model_print("Number of redundant executions: %d\n", stats.num_redundant);
445 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
446 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
447 model_print("Total executions: %d\n", stats.num_total);
448 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
452 * @brief End-of-exeuction print
453 * @param printbugs Should any existing bugs be printed?
455 void ModelChecker::print_execution(bool printbugs) const
457 print_program_output();
459 if (DBG_ENABLED() || params.verbose) {
460 model_print("Earliest divergence point since last feasible execution:\n");
461 if (earliest_diverge)
462 earliest_diverge->print();
464 model_print("(Not set)\n");
470 /* Don't print invalid bugs */
479 * Queries the model-checker for more executions to explore and, if one
480 * exists, resets the model-checker state to execute a new execution.
482 * @return If there are more executions to explore, return true. Otherwise,
485 bool ModelChecker::next_execution()
488 /* Is this execution a feasible execution that's worth bug-checking? */
489 bool complete = isfeasibleprefix() && (is_complete_execution() ||
492 /* End-of-execution bug checks */
495 assert_bug("Deadlock detected");
503 if (DBG_ENABLED() || params.verbose || have_bug_reports())
504 print_execution(complete);
506 clear_program_output();
509 earliest_diverge = NULL;
511 if ((diverge = get_next_backtrack()) == NULL)
515 model_print("Next execution will diverge at:\n");
519 reset_to_initial_state();
523 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
525 switch (act->get_type()) {
530 /* Optimization: relaxed operations don't need backtracking */
531 if (act->is_relaxed())
533 /* linear search: from most recent to oldest */
534 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
535 action_list_t::reverse_iterator rit;
536 for (rit = list->rbegin(); rit != list->rend(); rit++) {
537 ModelAction *prev = *rit;
538 if (prev->could_synchronize_with(act))
544 case ATOMIC_TRYLOCK: {
545 /* linear search: from most recent to oldest */
546 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
547 action_list_t::reverse_iterator rit;
548 for (rit = list->rbegin(); rit != list->rend(); rit++) {
549 ModelAction *prev = *rit;
550 if (act->is_conflicting_lock(prev))
555 case ATOMIC_UNLOCK: {
556 /* linear search: from most recent to oldest */
557 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
558 action_list_t::reverse_iterator rit;
559 for (rit = list->rbegin(); rit != list->rend(); rit++) {
560 ModelAction *prev = *rit;
561 if (!act->same_thread(prev)&&prev->is_failed_trylock())
567 /* linear search: from most recent to oldest */
568 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
569 action_list_t::reverse_iterator rit;
570 for (rit = list->rbegin(); rit != list->rend(); rit++) {
571 ModelAction *prev = *rit;
572 if (!act->same_thread(prev)&&prev->is_failed_trylock())
574 if (!act->same_thread(prev)&&prev->is_notify())
580 case ATOMIC_NOTIFY_ALL:
581 case ATOMIC_NOTIFY_ONE: {
582 /* linear search: from most recent to oldest */
583 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
584 action_list_t::reverse_iterator rit;
585 for (rit = list->rbegin(); rit != list->rend(); rit++) {
586 ModelAction *prev = *rit;
587 if (!act->same_thread(prev)&&prev->is_wait())
598 /** This method finds backtracking points where we should try to
599 * reorder the parameter ModelAction against.
601 * @param the ModelAction to find backtracking points for.
603 void ModelChecker::set_backtracking(ModelAction *act)
605 Thread *t = get_thread(act);
606 ModelAction * prev = get_last_conflict(act);
610 Node * node = prev->get_node()->get_parent();
612 int low_tid, high_tid;
613 if (node->is_enabled(t)) {
614 low_tid = id_to_int(act->get_tid());
615 high_tid = low_tid+1;
618 high_tid = get_num_threads();
621 for(int i = low_tid; i < high_tid; i++) {
622 thread_id_t tid = int_to_id(i);
624 /* Make sure this thread can be enabled here. */
625 if (i >= node->get_num_threads())
628 /* Don't backtrack into a point where the thread is disabled or sleeping. */
629 if (node->enabled_status(tid)!=THREAD_ENABLED)
632 /* Check if this has been explored already */
633 if (node->has_been_explored(tid))
636 /* See if fairness allows */
637 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
639 for(int t=0;t<node->get_num_threads();t++) {
640 thread_id_t tother=int_to_id(t);
641 if (node->is_enabled(tother) && node->has_priority(tother)) {
649 /* Cache the latest backtracking point */
650 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
651 priv->next_backtrack = prev;
653 /* If this is a new backtracking point, mark the tree */
654 if (!node->set_backtrack(tid))
656 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
657 id_to_int(prev->get_tid()),
658 id_to_int(t->get_id()));
667 * Returns last backtracking point. The model checker will explore a different
668 * path for this point in the next execution.
669 * @return The ModelAction at which the next execution should diverge.
671 ModelAction * ModelChecker::get_next_backtrack()
673 ModelAction *next = priv->next_backtrack;
674 priv->next_backtrack = NULL;
679 * Processes a read or rmw model action.
680 * @param curr is the read model action to process.
681 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
682 * @return True if processing this read updates the mo_graph.
684 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
686 uint64_t value = VALUE_NONE;
687 bool updated = false;
689 const ModelAction *reads_from = curr->get_node()->get_read_from();
690 if (reads_from != NULL) {
691 mo_graph->startChanges();
693 value = reads_from->get_value();
694 bool r_status = false;
696 if (!second_part_of_rmw) {
697 check_recency(curr, reads_from);
698 r_status = r_modification_order(curr, reads_from);
702 if (!second_part_of_rmw&&is_infeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
703 mo_graph->rollbackChanges();
704 priv->too_many_reads = false;
708 read_from(curr, reads_from);
709 mo_graph->commitChanges();
710 mo_check_promises(curr->get_tid(), reads_from);
713 } else if (!second_part_of_rmw) {
714 /* Read from future value */
715 value = curr->get_node()->get_future_value();
716 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
717 read_from(curr, NULL);
718 Promise *valuepromise = new Promise(curr, value, expiration);
719 promises->push_back(valuepromise);
721 get_thread(curr)->set_return_value(value);
727 * Processes a lock, trylock, or unlock model action. @param curr is
728 * the read model action to process.
730 * The try lock operation checks whether the lock is taken. If not,
731 * it falls to the normal lock operation case. If so, it returns
734 * The lock operation has already been checked that it is enabled, so
735 * it just grabs the lock and synchronizes with the previous unlock.
737 * The unlock operation has to re-enable all of the threads that are
738 * waiting on the lock.
740 * @return True if synchronization was updated; false otherwise
742 bool ModelChecker::process_mutex(ModelAction *curr) {
743 std::mutex *mutex=NULL;
744 struct std::mutex_state *state=NULL;
746 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
747 mutex = (std::mutex *)curr->get_location();
748 state = mutex->get_state();
749 } else if(curr->is_wait()) {
750 mutex = (std::mutex *)curr->get_value();
751 state = mutex->get_state();
754 switch (curr->get_type()) {
755 case ATOMIC_TRYLOCK: {
756 bool success = !state->islocked;
757 curr->set_try_lock(success);
759 get_thread(curr)->set_return_value(0);
762 get_thread(curr)->set_return_value(1);
764 //otherwise fall into the lock case
766 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
767 assert_bug("Lock access before initialization");
768 state->islocked = true;
769 ModelAction *unlock = get_last_unlock(curr);
770 //synchronize with the previous unlock statement
771 if (unlock != NULL) {
772 curr->synchronize_with(unlock);
777 case ATOMIC_UNLOCK: {
779 state->islocked = false;
780 //wake up the other threads
781 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
782 //activate all the waiting threads
783 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
784 scheduler->wake(get_thread(*rit));
791 state->islocked = false;
792 //wake up the other threads
793 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
794 //activate all the waiting threads
795 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
796 scheduler->wake(get_thread(*rit));
799 //check whether we should go to sleep or not...simulate spurious failures
800 if (curr->get_node()->get_misc()==0) {
801 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
803 scheduler->sleep(get_current_thread());
807 case ATOMIC_NOTIFY_ALL: {
808 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
809 //activate all the waiting threads
810 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
811 scheduler->wake(get_thread(*rit));
816 case ATOMIC_NOTIFY_ONE: {
817 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
818 int wakeupthread=curr->get_node()->get_misc();
819 action_list_t::iterator it = waiters->begin();
820 advance(it, wakeupthread);
821 scheduler->wake(get_thread(*it));
833 * Process a write ModelAction
834 * @param curr The ModelAction to process
835 * @return True if the mo_graph was updated or promises were resolved
837 bool ModelChecker::process_write(ModelAction *curr)
839 bool updated_mod_order = w_modification_order(curr);
840 bool updated_promises = resolve_promises(curr);
842 if (promises->size() == 0) {
843 for (unsigned int i = 0; i < futurevalues->size(); i++) {
844 struct PendingFutureValue pfv = (*futurevalues)[i];
845 //Do more ambitious checks now that mo is more complete
846 if (mo_may_allow(pfv.writer, pfv.act)&&
847 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number()+params.maxfuturedelay) &&
848 (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
849 priv->next_backtrack = pfv.act;
851 futurevalues->resize(0);
854 mo_graph->commitChanges();
855 mo_check_promises(curr->get_tid(), curr);
857 get_thread(curr)->set_return_value(VALUE_NONE);
858 return updated_mod_order || updated_promises;
862 * @brief Process the current action for thread-related activity
864 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
865 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
866 * synchronization, etc. This function is a no-op for non-THREAD actions
867 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
869 * @param curr The current action
870 * @return True if synchronization was updated or a thread completed
872 bool ModelChecker::process_thread_action(ModelAction *curr)
874 bool updated = false;
876 switch (curr->get_type()) {
877 case THREAD_CREATE: {
878 Thread *th = (Thread *)curr->get_location();
879 th->set_creation(curr);
883 Thread *blocking = (Thread *)curr->get_location();
884 ModelAction *act = get_last_action(blocking->get_id());
885 curr->synchronize_with(act);
886 updated = true; /* trigger rel-seq checks */
889 case THREAD_FINISH: {
890 Thread *th = get_thread(curr);
891 while (!th->wait_list_empty()) {
892 ModelAction *act = th->pop_wait_list();
893 scheduler->wake(get_thread(act));
896 updated = true; /* trigger rel-seq checks */
900 check_promises(curr->get_tid(), NULL, curr->get_cv());
911 * @brief Process the current action for release sequence fixup activity
913 * Performs model-checker release sequence fixups for the current action,
914 * forcing a single pending release sequence to break (with a given, potential
915 * "loose" write) or to complete (i.e., synchronize). If a pending release
916 * sequence forms a complete release sequence, then we must perform the fixup
917 * synchronization, mo_graph additions, etc.
919 * @param curr The current action; must be a release sequence fixup action
920 * @param work_queue The work queue to which to add work items as they are
923 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
925 const ModelAction *write = curr->get_node()->get_relseq_break();
926 struct release_seq *sequence = pending_rel_seqs->back();
927 pending_rel_seqs->pop_back();
929 ModelAction *acquire = sequence->acquire;
930 const ModelAction *rf = sequence->rf;
931 const ModelAction *release = sequence->release;
935 ASSERT(release->same_thread(rf));
939 * @todo Forcing a synchronization requires that we set
940 * modification order constraints. For instance, we can't allow
941 * a fixup sequence in which two separate read-acquire
942 * operations read from the same sequence, where the first one
943 * synchronizes and the other doesn't. Essentially, we can't
944 * allow any writes to insert themselves between 'release' and
948 /* Must synchronize */
949 if (!acquire->synchronize_with(release)) {
950 set_bad_synchronization();
953 /* Re-check all pending release sequences */
954 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
955 /* Re-check act for mo_graph edges */
956 work_queue->push_back(MOEdgeWorkEntry(acquire));
958 /* propagate synchronization to later actions */
959 action_list_t::reverse_iterator rit = action_trace->rbegin();
960 for (; (*rit) != acquire; rit++) {
961 ModelAction *propagate = *rit;
962 if (acquire->happens_before(propagate)) {
963 propagate->synchronize_with(acquire);
964 /* Re-check 'propagate' for mo_graph edges */
965 work_queue->push_back(MOEdgeWorkEntry(propagate));
969 /* Break release sequence with new edges:
970 * release --mo--> write --mo--> rf */
971 mo_graph->addEdge(release, write);
972 mo_graph->addEdge(write, rf);
975 /* See if we have realized a data race */
980 * Initialize the current action by performing one or more of the following
981 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
982 * in the NodeStack, manipulating backtracking sets, allocating and
983 * initializing clock vectors, and computing the promises to fulfill.
985 * @param curr The current action, as passed from the user context; may be
986 * freed/invalidated after the execution of this function, with a different
987 * action "returned" its place (pass-by-reference)
988 * @return True if curr is a newly-explored action; false otherwise
990 bool ModelChecker::initialize_curr_action(ModelAction **curr)
992 ModelAction *newcurr;
994 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
995 newcurr = process_rmw(*curr);
998 if (newcurr->is_rmw())
999 compute_promises(newcurr);
1005 (*curr)->set_seq_number(get_next_seq_num());
1007 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1009 /* First restore type and order in case of RMW operation */
1010 if ((*curr)->is_rmwr())
1011 newcurr->copy_typeandorder(*curr);
1013 ASSERT((*curr)->get_location() == newcurr->get_location());
1014 newcurr->copy_from_new(*curr);
1016 /* Discard duplicate ModelAction; use action from NodeStack */
1019 /* Always compute new clock vector */
1020 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1023 return false; /* Action was explored previously */
1027 /* Always compute new clock vector */
1028 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1030 /* Assign most recent release fence */
1031 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1034 * Perform one-time actions when pushing new ModelAction onto
1037 if (newcurr->is_write())
1038 compute_promises(newcurr);
1039 else if (newcurr->is_relseq_fixup())
1040 compute_relseq_breakwrites(newcurr);
1041 else if (newcurr->is_wait())
1042 newcurr->get_node()->set_misc_max(2);
1043 else if (newcurr->is_notify_one()) {
1044 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1046 return true; /* This was a new ModelAction */
1051 * @brief Establish reads-from relation between two actions
1053 * Perform basic operations involved with establishing a concrete rf relation,
1054 * including setting the ModelAction data and checking for release sequences.
1056 * @param act The action that is reading (must be a read)
1057 * @param rf The action from which we are reading (must be a write)
1059 * @return True if this read established synchronization
1061 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1063 act->set_read_from(rf);
1064 if (rf != NULL && act->is_acquire()) {
1065 rel_heads_list_t release_heads;
1066 get_release_seq_heads(act, &release_heads);
1067 int num_heads = release_heads.size();
1068 for (unsigned int i = 0; i < release_heads.size(); i++)
1069 if (!act->synchronize_with(release_heads[i])) {
1070 set_bad_synchronization();
1073 return num_heads > 0;
1079 * @brief Check whether a model action is enabled.
1081 * Checks whether a lock or join operation would be successful (i.e., is the
1082 * lock already locked, or is the joined thread already complete). If not, put
1083 * the action in a waiter list.
1085 * @param curr is the ModelAction to check whether it is enabled.
1086 * @return a bool that indicates whether the action is enabled.
1088 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1089 if (curr->is_lock()) {
1090 std::mutex * lock = (std::mutex *)curr->get_location();
1091 struct std::mutex_state * state = lock->get_state();
1092 if (state->islocked) {
1093 //Stick the action in the appropriate waiting queue
1094 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1097 } else if (curr->get_type() == THREAD_JOIN) {
1098 Thread *blocking = (Thread *)curr->get_location();
1099 if (!blocking->is_complete()) {
1100 blocking->push_wait_list(curr);
1109 * Stores the ModelAction for the current thread action. Call this
1110 * immediately before switching from user- to system-context to pass
1111 * data between them.
1112 * @param act The ModelAction created by the user-thread action
1114 void ModelChecker::set_current_action(ModelAction *act) {
1115 priv->current_action = act;
1119 * This is the heart of the model checker routine. It performs model-checking
1120 * actions corresponding to a given "current action." Among other processes, it
1121 * calculates reads-from relationships, updates synchronization clock vectors,
1122 * forms a memory_order constraints graph, and handles replay/backtrack
1123 * execution when running permutations of previously-observed executions.
1125 * @param curr The current action to process
1126 * @return The next Thread that must be executed. May be NULL if ModelChecker
1127 * makes no choice (e.g., according to replay execution, combining RMW actions,
1130 Thread * ModelChecker::check_current_action(ModelAction *curr)
1133 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1135 if (!check_action_enabled(curr)) {
1136 /* Make the execution look like we chose to run this action
1137 * much later, when a lock/join can succeed */
1138 get_current_thread()->set_pending(curr);
1139 scheduler->sleep(get_current_thread());
1140 return get_next_thread(NULL);
1143 bool newly_explored = initialize_curr_action(&curr);
1145 wake_up_sleeping_actions(curr);
1147 /* Add the action to lists before any other model-checking tasks */
1148 if (!second_part_of_rmw)
1149 add_action_to_lists(curr);
1151 /* Build may_read_from set for newly-created actions */
1152 if (newly_explored && curr->is_read())
1153 build_reads_from_past(curr);
1155 /* Initialize work_queue with the "current action" work */
1156 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1157 while (!work_queue.empty() && !has_asserted()) {
1158 WorkQueueEntry work = work_queue.front();
1159 work_queue.pop_front();
1161 switch (work.type) {
1162 case WORK_CHECK_CURR_ACTION: {
1163 ModelAction *act = work.action;
1164 bool update = false; /* update this location's release seq's */
1165 bool update_all = false; /* update all release seq's */
1167 if (process_thread_action(curr))
1170 if (act->is_read() && process_read(act, second_part_of_rmw))
1173 if (act->is_write() && process_write(act))
1176 if (act->is_mutex_op() && process_mutex(act))
1179 if (act->is_relseq_fixup())
1180 process_relseq_fixup(curr, &work_queue);
1183 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1185 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1188 case WORK_CHECK_RELEASE_SEQ:
1189 resolve_release_sequences(work.location, &work_queue);
1191 case WORK_CHECK_MO_EDGES: {
1192 /** @todo Complete verification of work_queue */
1193 ModelAction *act = work.action;
1194 bool updated = false;
1196 if (act->is_read()) {
1197 const ModelAction *rf = act->get_reads_from();
1198 if (rf != NULL && r_modification_order(act, rf))
1201 if (act->is_write()) {
1202 if (w_modification_order(act))
1205 mo_graph->commitChanges();
1208 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1217 check_curr_backtracking(curr);
1218 set_backtracking(curr);
1219 return get_next_thread(curr);
1222 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
1223 Node *currnode = curr->get_node();
1224 Node *parnode = currnode->get_parent();
1226 if ((!parnode->backtrack_empty() ||
1227 !currnode->misc_empty() ||
1228 !currnode->read_from_empty() ||
1229 !currnode->future_value_empty() ||
1230 !currnode->promise_empty() ||
1231 !currnode->relseq_break_empty())
1232 && (!priv->next_backtrack ||
1233 *curr > *priv->next_backtrack)) {
1234 priv->next_backtrack = curr;
1238 bool ModelChecker::promises_expired() const
1240 for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
1241 Promise *promise = (*promises)[promise_index];
1242 if (promise->get_expiration()<priv->used_sequence_numbers) {
1250 * This is the strongest feasibility check available.
1251 * @return whether the current trace (partial or complete) must be a prefix of
1254 bool ModelChecker::isfeasibleprefix() const
1256 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1260 * Returns whether the current completed trace is feasible, except for pending
1261 * release sequences.
1263 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1265 if (DBG_ENABLED() && promises->size() != 0)
1266 DEBUG("Infeasible: unrevolved promises\n");
1268 return !is_infeasible() && promises->size() == 0;
1272 * Check if the current partial trace is infeasible. Does not check any
1273 * end-of-execution flags, which might rule out the execution. Thus, this is
1274 * useful only for ruling an execution as infeasible.
1275 * @return whether the current partial trace is infeasible.
1277 bool ModelChecker::is_infeasible() const
1279 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1280 DEBUG("Infeasible: RMW violation\n");
1282 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1286 * Check If the current partial trace is infeasible, while ignoring
1287 * infeasibility related to 2 RMW's reading from the same store. It does not
1288 * check end-of-execution feasibility.
1289 * @see ModelChecker::is_infeasible
1290 * @return whether the current partial trace is infeasible, ignoring multiple
1291 * RMWs reading from the same store.
1293 bool ModelChecker::is_infeasible_ignoreRMW() const
1295 if (DBG_ENABLED()) {
1296 if (mo_graph->checkForCycles())
1297 DEBUG("Infeasible: modification order cycles\n");
1298 if (priv->failed_promise)
1299 DEBUG("Infeasible: failed promise\n");
1300 if (priv->too_many_reads)
1301 DEBUG("Infeasible: too many reads\n");
1302 if (priv->bad_synchronization)
1303 DEBUG("Infeasible: bad synchronization ordering\n");
1304 if (promises_expired())
1305 DEBUG("Infeasible: promises expired\n");
1307 return mo_graph->checkForCycles() || priv->failed_promise ||
1308 priv->too_many_reads || priv->bad_synchronization ||
1312 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1313 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1314 ModelAction *lastread = get_last_action(act->get_tid());
1315 lastread->process_rmw(act);
1316 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1317 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1318 mo_graph->commitChanges();
1324 * Checks whether a thread has read from the same write for too many times
1325 * without seeing the effects of a later write.
1328 * 1) there must a different write that we could read from that would satisfy the modification order,
1329 * 2) we must have read from the same value in excess of maxreads times, and
1330 * 3) that other write must have been in the reads_from set for maxreads times.
1332 * If so, we decide that the execution is no longer feasible.
1334 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1335 if (params.maxreads != 0) {
1337 if (curr->get_node()->get_read_from_size() <= 1)
1339 //Must make sure that execution is currently feasible... We could
1340 //accidentally clear by rolling back
1341 if (is_infeasible())
1343 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1344 int tid = id_to_int(curr->get_tid());
1347 if ((int)thrd_lists->size() <= tid)
1349 action_list_t *list = &(*thrd_lists)[tid];
1351 action_list_t::reverse_iterator rit = list->rbegin();
1352 /* Skip past curr */
1353 for (; (*rit) != curr; rit++)
1355 /* go past curr now */
1358 action_list_t::reverse_iterator ritcopy = rit;
1359 //See if we have enough reads from the same value
1361 for (; count < params.maxreads; rit++,count++) {
1362 if (rit==list->rend())
1364 ModelAction *act = *rit;
1365 if (!act->is_read())
1368 if (act->get_reads_from() != rf)
1370 if (act->get_node()->get_read_from_size() <= 1)
1373 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1375 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1377 //Need a different write
1381 /* Test to see whether this is a feasible write to read from*/
1382 mo_graph->startChanges();
1383 r_modification_order(curr, write);
1384 bool feasiblereadfrom = !is_infeasible();
1385 mo_graph->rollbackChanges();
1387 if (!feasiblereadfrom)
1391 bool feasiblewrite = true;
1392 //new we need to see if this write works for everyone
1394 for (int loop = count; loop>0; loop--,rit++) {
1395 ModelAction *act=*rit;
1396 bool foundvalue = false;
1397 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1398 if (act->get_node()->get_read_from_at(j)==write) {
1404 feasiblewrite = false;
1408 if (feasiblewrite) {
1409 priv->too_many_reads = true;
1417 * Updates the mo_graph with the constraints imposed from the current
1420 * Basic idea is the following: Go through each other thread and find
1421 * the lastest action that happened before our read. Two cases:
1423 * (1) The action is a write => that write must either occur before
1424 * the write we read from or be the write we read from.
1426 * (2) The action is a read => the write that that action read from
1427 * must occur before the write we read from or be the same write.
1429 * @param curr The current action. Must be a read.
1430 * @param rf The action that curr reads from. Must be a write.
1431 * @return True if modification order edges were added; false otherwise
1433 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1435 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1438 ASSERT(curr->is_read());
1440 /* Last SC fence in the current thread */
1441 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1443 /* Iterate over all threads */
1444 for (i = 0; i < thrd_lists->size(); i++) {
1445 /* Last SC fence in thread i */
1446 ModelAction *last_sc_fence_thread_local = NULL;
1447 if (int_to_id((int)i) != curr->get_tid())
1448 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1450 /* Last SC fence in thread i, before last SC fence in current thread */
1451 ModelAction *last_sc_fence_thread_before = NULL;
1452 if (last_sc_fence_local)
1453 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1455 /* Iterate over actions in thread, starting from most recent */
1456 action_list_t *list = &(*thrd_lists)[i];
1457 action_list_t::reverse_iterator rit;
1458 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1459 ModelAction *act = *rit;
1461 if (act->is_write() && act != rf && act != curr) {
1462 /* C++, Section 29.3 statement 5 */
1463 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1464 *act < *last_sc_fence_thread_local) {
1465 mo_graph->addEdge(act, rf);
1468 /* C++, Section 29.3 statement 4 */
1469 else if (act->is_seqcst() && last_sc_fence_local &&
1470 *act < *last_sc_fence_local) {
1471 mo_graph->addEdge(act, rf);
1474 /* C++, Section 29.3 statement 6 */
1475 else if (last_sc_fence_thread_before &&
1476 *act < *last_sc_fence_thread_before) {
1477 mo_graph->addEdge(act, rf);
1483 * Include at most one act per-thread that "happens
1484 * before" curr. Don't consider reflexively.
1486 if (act->happens_before(curr) && act != curr) {
1487 if (act->is_write()) {
1489 mo_graph->addEdge(act, rf);
1493 const ModelAction *prevreadfrom = act->get_reads_from();
1494 //if the previous read is unresolved, keep going...
1495 if (prevreadfrom == NULL)
1498 if (rf != prevreadfrom) {
1499 mo_graph->addEdge(prevreadfrom, rf);
1511 /** This method fixes up the modification order when we resolve a
1512 * promises. The basic problem is that actions that occur after the
1513 * read curr could not property add items to the modification order
1516 * So for each thread, we find the earliest item that happens after
1517 * the read curr. This is the item we have to fix up with additional
1518 * constraints. If that action is write, we add a MO edge between
1519 * the Action rf and that action. If the action is a read, we add a
1520 * MO edge between the Action rf, and whatever the read accessed.
1522 * @param curr is the read ModelAction that we are fixing up MO edges for.
1523 * @param rf is the write ModelAction that curr reads from.
1526 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1528 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1530 ASSERT(curr->is_read());
1532 /* Iterate over all threads */
1533 for (i = 0; i < thrd_lists->size(); i++) {
1534 /* Iterate over actions in thread, starting from most recent */
1535 action_list_t *list = &(*thrd_lists)[i];
1536 action_list_t::reverse_iterator rit;
1537 ModelAction *lastact = NULL;
1539 /* Find last action that happens after curr that is either not curr or a rmw */
1540 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1541 ModelAction *act = *rit;
1542 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1548 /* Include at most one act per-thread that "happens before" curr */
1549 if (lastact != NULL) {
1550 if (lastact==curr) {
1551 //Case 1: The resolved read is a RMW, and we need to make sure
1552 //that the write portion of the RMW mod order after rf
1554 mo_graph->addEdge(rf, lastact);
1555 } else if (lastact->is_read()) {
1556 //Case 2: The resolved read is a normal read and the next
1557 //operation is a read, and we need to make sure the value read
1558 //is mod ordered after rf
1560 const ModelAction *postreadfrom = lastact->get_reads_from();
1561 if (postreadfrom != NULL&&rf != postreadfrom)
1562 mo_graph->addEdge(rf, postreadfrom);
1564 //Case 3: The resolved read is a normal read and the next
1565 //operation is a write, and we need to make sure that the
1566 //write is mod ordered after rf
1568 mo_graph->addEdge(rf, lastact);
1576 * Updates the mo_graph with the constraints imposed from the current write.
1578 * Basic idea is the following: Go through each other thread and find
1579 * the lastest action that happened before our write. Two cases:
1581 * (1) The action is a write => that write must occur before
1584 * (2) The action is a read => the write that that action read from
1585 * must occur before the current write.
1587 * This method also handles two other issues:
1589 * (I) Sequential Consistency: Making sure that if the current write is
1590 * seq_cst, that it occurs after the previous seq_cst write.
1592 * (II) Sending the write back to non-synchronizing reads.
1594 * @param curr The current action. Must be a write.
1595 * @return True if modification order edges were added; false otherwise
1597 bool ModelChecker::w_modification_order(ModelAction *curr)
1599 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1602 ASSERT(curr->is_write());
1604 if (curr->is_seqcst()) {
1605 /* We have to at least see the last sequentially consistent write,
1606 so we are initialized. */
1607 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1608 if (last_seq_cst != NULL) {
1609 mo_graph->addEdge(last_seq_cst, curr);
1614 /* Last SC fence in the current thread */
1615 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1617 /* Iterate over all threads */
1618 for (i = 0; i < thrd_lists->size(); i++) {
1619 /* Last SC fence in thread i, before last SC fence in current thread */
1620 ModelAction *last_sc_fence_thread_before = NULL;
1621 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1622 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1624 /* Iterate over actions in thread, starting from most recent */
1625 action_list_t *list = &(*thrd_lists)[i];
1626 action_list_t::reverse_iterator rit;
1627 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1628 ModelAction *act = *rit;
1631 * 1) If RMW and it actually read from something, then we
1632 * already have all relevant edges, so just skip to next
1635 * 2) If RMW and it didn't read from anything, we should
1636 * whatever edge we can get to speed up convergence.
1638 * 3) If normal write, we need to look at earlier actions, so
1639 * continue processing list.
1641 if (curr->is_rmw()) {
1642 if (curr->get_reads_from()!=NULL)
1650 /* C++, Section 29.3 statement 7 */
1651 if (last_sc_fence_thread_before && act->is_write() &&
1652 *act < *last_sc_fence_thread_before) {
1653 mo_graph->addEdge(act, curr);
1658 * Include at most one act per-thread that "happens
1661 if (act->happens_before(curr)) {
1663 * Note: if act is RMW, just add edge:
1665 * The following edge should be handled elsewhere:
1666 * readfrom(act) --mo--> act
1668 if (act->is_write())
1669 mo_graph->addEdge(act, curr);
1670 else if (act->is_read()) {
1671 //if previous read accessed a null, just keep going
1672 if (act->get_reads_from() == NULL)
1674 mo_graph->addEdge(act->get_reads_from(), curr);
1678 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1679 !act->same_thread(curr)) {
1680 /* We have an action that:
1681 (1) did not happen before us
1682 (2) is a read and we are a write
1683 (3) cannot synchronize with us
1684 (4) is in a different thread
1686 that read could potentially read from our write. Note that
1687 these checks are overly conservative at this point, we'll
1688 do more checks before actually removing the
1692 if (thin_air_constraint_may_allow(curr, act)) {
1693 if (!is_infeasible() ||
1694 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1695 struct PendingFutureValue pfv = {curr,act};
1696 futurevalues->push_back(pfv);
1706 /** Arbitrary reads from the future are not allowed. Section 29.3
1707 * part 9 places some constraints. This method checks one result of constraint
1708 * constraint. Others require compiler support. */
1709 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1710 if (!writer->is_rmw())
1713 if (!reader->is_rmw())
1716 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1717 if (search == reader)
1719 if (search->get_tid() == reader->get_tid() &&
1720 search->happens_before(reader))
1728 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1729 * some constraints. This method checks one the following constraint (others
1730 * require compiler support):
1732 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1734 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1736 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1738 /* Iterate over all threads */
1739 for (i = 0; i < thrd_lists->size(); i++) {
1740 const ModelAction *write_after_read = NULL;
1742 /* Iterate over actions in thread, starting from most recent */
1743 action_list_t *list = &(*thrd_lists)[i];
1744 action_list_t::reverse_iterator rit;
1745 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1746 ModelAction *act = *rit;
1748 if (!reader->happens_before(act))
1750 else if (act->is_write())
1751 write_after_read = act;
1752 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1753 write_after_read = act->get_reads_from();
1757 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1764 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1765 * The ModelAction under consideration is expected to be taking part in
1766 * release/acquire synchronization as an object of the "reads from" relation.
1767 * Note that this can only provide release sequence support for RMW chains
1768 * which do not read from the future, as those actions cannot be traced until
1769 * their "promise" is fulfilled. Similarly, we may not even establish the
1770 * presence of a release sequence with certainty, as some modification order
1771 * constraints may be decided further in the future. Thus, this function
1772 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1773 * and a boolean representing certainty.
1775 * @param rf The action that might be part of a release sequence. Must be a
1777 * @param release_heads A pass-by-reference style return parameter. After
1778 * execution of this function, release_heads will contain the heads of all the
1779 * relevant release sequences, if any exists with certainty
1780 * @param pending A pass-by-reference style return parameter which is only used
1781 * when returning false (i.e., uncertain). Returns most information regarding
1782 * an uncertain release sequence, including any write operations that might
1783 * break the sequence.
1784 * @return true, if the ModelChecker is certain that release_heads is complete;
1787 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1788 rel_heads_list_t *release_heads,
1789 struct release_seq *pending) const
1791 /* Only check for release sequences if there are no cycles */
1792 if (mo_graph->checkForCycles())
1796 ASSERT(rf->is_write());
1798 if (rf->is_release())
1799 release_heads->push_back(rf);
1801 break; /* End of RMW chain */
1803 /** @todo Need to be smarter here... In the linux lock
1804 * example, this will run to the beginning of the program for
1806 /** @todo The way to be smarter here is to keep going until 1
1807 * thread has a release preceded by an acquire and you've seen
1810 /* acq_rel RMW is a sufficient stopping condition */
1811 if (rf->is_acquire() && rf->is_release())
1812 return true; /* complete */
1814 rf = rf->get_reads_from();
1817 /* read from future: need to settle this later */
1819 return false; /* incomplete */
1822 if (rf->is_release())
1823 return true; /* complete */
1825 /* else relaxed write; check modification order for contiguous subsequence
1826 * -> rf must be same thread as release */
1827 int tid = id_to_int(rf->get_tid());
1828 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1829 action_list_t *list = &(*thrd_lists)[tid];
1830 action_list_t::const_reverse_iterator rit;
1832 /* Find rf in the thread list */
1833 rit = std::find(list->rbegin(), list->rend(), rf);
1834 ASSERT(rit != list->rend());
1836 /* Find the last write/release */
1837 for (; rit != list->rend(); rit++)
1838 if ((*rit)->is_release())
1840 if (rit == list->rend()) {
1841 /* No write-release in this thread */
1842 return true; /* complete */
1844 ModelAction *release = *rit;
1846 ASSERT(rf->same_thread(release));
1848 pending->writes.clear();
1850 bool certain = true;
1851 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1852 if (id_to_int(rf->get_tid()) == (int)i)
1854 list = &(*thrd_lists)[i];
1856 /* Can we ensure no future writes from this thread may break
1857 * the release seq? */
1858 bool future_ordered = false;
1860 ModelAction *last = get_last_action(int_to_id(i));
1861 Thread *th = get_thread(int_to_id(i));
1862 if ((last && rf->happens_before(last)) ||
1865 future_ordered = true;
1867 ASSERT(!th->is_model_thread() || future_ordered);
1869 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1870 const ModelAction *act = *rit;
1871 /* Reach synchronization -> this thread is complete */
1872 if (act->happens_before(release))
1874 if (rf->happens_before(act)) {
1875 future_ordered = true;
1879 /* Only non-RMW writes can break release sequences */
1880 if (!act->is_write() || act->is_rmw())
1883 /* Check modification order */
1884 if (mo_graph->checkReachable(rf, act)) {
1885 /* rf --mo--> act */
1886 future_ordered = true;
1889 if (mo_graph->checkReachable(act, release))
1890 /* act --mo--> release */
1892 if (mo_graph->checkReachable(release, act) &&
1893 mo_graph->checkReachable(act, rf)) {
1894 /* release --mo-> act --mo--> rf */
1895 return true; /* complete */
1897 /* act may break release sequence */
1898 pending->writes.push_back(act);
1901 if (!future_ordered)
1902 certain = false; /* This thread is uncertain */
1906 release_heads->push_back(release);
1907 pending->writes.clear();
1909 pending->release = release;
1916 * A public interface for getting the release sequence head(s) with which a
1917 * given ModelAction must synchronize. This function only returns a non-empty
1918 * result when it can locate a release sequence head with certainty. Otherwise,
1919 * it may mark the internal state of the ModelChecker so that it will handle
1920 * the release sequence at a later time, causing @a act to update its
1921 * synchronization at some later point in execution.
1922 * @param act The 'acquire' action that may read from a release sequence
1923 * @param release_heads A pass-by-reference return parameter. Will be filled
1924 * with the head(s) of the release sequence(s), if they exists with certainty.
1925 * @see ModelChecker::release_seq_heads
1927 void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
1929 const ModelAction *rf = act->get_reads_from();
1930 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
1931 sequence->acquire = act;
1933 if (!release_seq_heads(rf, release_heads, sequence)) {
1934 /* add act to 'lazy checking' list */
1935 pending_rel_seqs->push_back(sequence);
1937 snapshot_free(sequence);
1942 * Attempt to resolve all stashed operations that might synchronize with a
1943 * release sequence for a given location. This implements the "lazy" portion of
1944 * determining whether or not a release sequence was contiguous, since not all
1945 * modification order information is present at the time an action occurs.
1947 * @param location The location/object that should be checked for release
1948 * sequence resolutions. A NULL value means to check all locations.
1949 * @param work_queue The work queue to which to add work items as they are
1951 * @return True if any updates occurred (new synchronization, new mo_graph
1954 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
1956 bool updated = false;
1957 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
1958 while (it != pending_rel_seqs->end()) {
1959 struct release_seq *pending = *it;
1960 ModelAction *act = pending->acquire;
1962 /* Only resolve sequences on the given location, if provided */
1963 if (location && act->get_location() != location) {
1968 const ModelAction *rf = act->get_reads_from();
1969 rel_heads_list_t release_heads;
1971 complete = release_seq_heads(rf, &release_heads, pending);
1972 for (unsigned int i = 0; i < release_heads.size(); i++) {
1973 if (!act->has_synchronized_with(release_heads[i])) {
1974 if (act->synchronize_with(release_heads[i]))
1977 set_bad_synchronization();
1982 /* Re-check all pending release sequences */
1983 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1984 /* Re-check act for mo_graph edges */
1985 work_queue->push_back(MOEdgeWorkEntry(act));
1987 /* propagate synchronization to later actions */
1988 action_list_t::reverse_iterator rit = action_trace->rbegin();
1989 for (; (*rit) != act; rit++) {
1990 ModelAction *propagate = *rit;
1991 if (act->happens_before(propagate)) {
1992 propagate->synchronize_with(act);
1993 /* Re-check 'propagate' for mo_graph edges */
1994 work_queue->push_back(MOEdgeWorkEntry(propagate));
1999 it = pending_rel_seqs->erase(it);
2000 snapshot_free(pending);
2006 // If we resolved promises or data races, see if we have realized a data race.
2013 * Performs various bookkeeping operations for the current ModelAction. For
2014 * instance, adds action to the per-object, per-thread action vector and to the
2015 * action trace list of all thread actions.
2017 * @param act is the ModelAction to add.
2019 void ModelChecker::add_action_to_lists(ModelAction *act)
2021 int tid = id_to_int(act->get_tid());
2022 action_trace->push_back(act);
2024 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
2026 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2027 if (tid >= (int)vec->size())
2028 vec->resize(priv->next_thread_id);
2029 (*vec)[tid].push_back(act);
2031 if ((int)thrd_last_action->size() <= tid)
2032 thrd_last_action->resize(get_num_threads());
2033 (*thrd_last_action)[tid] = act;
2035 if (act->is_fence() && act->is_release()) {
2036 if ((int)thrd_last_fence_release->size() <= tid)
2037 thrd_last_fence_release->resize(get_num_threads());
2038 (*thrd_last_fence_release)[tid] = act;
2041 if (act->is_wait()) {
2042 void *mutex_loc=(void *) act->get_value();
2043 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2045 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2046 if (tid >= (int)vec->size())
2047 vec->resize(priv->next_thread_id);
2048 (*vec)[tid].push_back(act);
2053 * @brief Get the last action performed by a particular Thread
2054 * @param tid The thread ID of the Thread in question
2055 * @return The last action in the thread
2057 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2059 int threadid = id_to_int(tid);
2060 if (threadid < (int)thrd_last_action->size())
2061 return (*thrd_last_action)[id_to_int(tid)];
2067 * @brief Get the last fence release performed by a particular Thread
2068 * @param tid The thread ID of the Thread in question
2069 * @return The last fence release in the thread, if one exists; NULL otherwise
2071 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2073 int threadid = id_to_int(tid);
2074 if (threadid < (int)thrd_last_fence_release->size())
2075 return (*thrd_last_fence_release)[id_to_int(tid)];
2081 * Gets the last memory_order_seq_cst write (in the total global sequence)
2082 * performed on a particular object (i.e., memory location), not including the
2084 * @param curr The current ModelAction; also denotes the object location to
2086 * @return The last seq_cst write
2088 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2090 void *location = curr->get_location();
2091 action_list_t *list = get_safe_ptr_action(obj_map, location);
2092 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2093 action_list_t::reverse_iterator rit;
2094 for (rit = list->rbegin(); rit != list->rend(); rit++)
2095 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2101 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2102 * performed in a particular thread, prior to a particular fence.
2103 * @param tid The ID of the thread to check
2104 * @param before_fence The fence from which to begin the search; if NULL, then
2105 * search for the most recent fence in the thread.
2106 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2108 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2110 /* All fences should have NULL location */
2111 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2112 action_list_t::reverse_iterator rit = list->rbegin();
2115 for (; rit != list->rend(); rit++)
2116 if (*rit == before_fence)
2119 ASSERT(*rit == before_fence);
2123 for (; rit != list->rend(); rit++)
2124 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2130 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2131 * location). This function identifies the mutex according to the current
2132 * action, which is presumed to perform on the same mutex.
2133 * @param curr The current ModelAction; also denotes the object location to
2135 * @return The last unlock operation
2137 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2139 void *location = curr->get_location();
2140 action_list_t *list = get_safe_ptr_action(obj_map, location);
2141 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2142 action_list_t::reverse_iterator rit;
2143 for (rit = list->rbegin(); rit != list->rend(); rit++)
2144 if ((*rit)->is_unlock() || (*rit)->is_wait())
2149 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2151 ModelAction *parent = get_last_action(tid);
2153 parent = get_thread(tid)->get_creation();
2158 * Returns the clock vector for a given thread.
2159 * @param tid The thread whose clock vector we want
2160 * @return Desired clock vector
2162 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2164 return get_parent_action(tid)->get_cv();
2168 * Resolve a set of Promises with a current write. The set is provided in the
2169 * Node corresponding to @a write.
2170 * @param write The ModelAction that is fulfilling Promises
2171 * @return True if promises were resolved; false otherwise
2173 bool ModelChecker::resolve_promises(ModelAction *write)
2175 bool resolved = false;
2176 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2178 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2179 Promise *promise = (*promises)[promise_index];
2180 if (write->get_node()->get_promise(i)) {
2181 ModelAction *read = promise->get_action();
2182 if (read->is_rmw()) {
2183 mo_graph->addRMWEdge(write, read);
2185 read_from(read, write);
2186 //First fix up the modification order for actions that happened
2188 r_modification_order(read, write);
2189 //Next fix up the modification order for actions that happened
2191 post_r_modification_order(read, write);
2192 //Make sure the promise's value matches the write's value
2193 ASSERT(promise->get_value() == write->get_value());
2196 promises->erase(promises->begin() + promise_index);
2197 threads_to_check.push_back(read->get_tid());
2204 //Check whether reading these writes has made threads unable to
2207 for(unsigned int i=0;i<threads_to_check.size();i++)
2208 mo_check_promises(threads_to_check[i], write);
2214 * Compute the set of promises that could potentially be satisfied by this
2215 * action. Note that the set computation actually appears in the Node, not in
2217 * @param curr The ModelAction that may satisfy promises
2219 void ModelChecker::compute_promises(ModelAction *curr)
2221 for (unsigned int i = 0; i < promises->size(); i++) {
2222 Promise *promise = (*promises)[i];
2223 const ModelAction *act = promise->get_action();
2224 if (!act->happens_before(curr) &&
2226 !act->could_synchronize_with(curr) &&
2227 !act->same_thread(curr) &&
2228 act->get_location() == curr->get_location() &&
2229 promise->get_value() == curr->get_value()) {
2230 curr->get_node()->set_promise(i, act->is_rmw());
2235 /** Checks promises in response to change in ClockVector Threads. */
2236 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2238 for (unsigned int i = 0; i < promises->size(); i++) {
2239 Promise *promise = (*promises)[i];
2240 const ModelAction *act = promise->get_action();
2241 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2242 merge_cv->synchronized_since(act)) {
2243 if (promise->increment_threads(tid)) {
2244 //Promise has failed
2245 priv->failed_promise = true;
2252 void ModelChecker::check_promises_thread_disabled() {
2253 for (unsigned int i = 0; i < promises->size(); i++) {
2254 Promise *promise = (*promises)[i];
2255 if (promise->check_promise()) {
2256 priv->failed_promise = true;
2262 /** Checks promises in response to addition to modification order for threads.
2264 * pthread is the thread that performed the read that created the promise
2266 * pread is the read that created the promise
2268 * pwrite is either the first write to same location as pread by
2269 * pthread that is sequenced after pread or the value read by the
2270 * first read to the same lcoation as pread by pthread that is
2271 * sequenced after pread..
2273 * 1. If tid=pthread, then we check what other threads are reachable
2274 * through the mode order starting with pwrite. Those threads cannot
2275 * perform a write that will resolve the promise due to modification
2276 * order constraints.
2278 * 2. If the tid is not pthread, we check whether pwrite can reach the
2279 * action write through the modification order. If so, that thread
2280 * cannot perform a future write that will resolve the promise due to
2281 * modificatin order constraints.
2283 * @parem tid The thread that either read from the model action
2284 * write, or actually did the model action write.
2286 * @parem write The ModelAction representing the relevant write.
2289 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2290 void * location = write->get_location();
2291 for (unsigned int i = 0; i < promises->size(); i++) {
2292 Promise *promise = (*promises)[i];
2293 const ModelAction *act = promise->get_action();
2295 //Is this promise on the same location?
2296 if ( act->get_location() != location )
2299 //same thread as the promise
2300 if ( act->get_tid()==tid ) {
2302 //do we have a pwrite for the promise, if not, set it
2303 if (promise->get_write() == NULL ) {
2304 promise->set_write(write);
2305 //The pwrite cannot happen before the promise
2306 if (write->happens_before(act) && (write != act)) {
2307 priv->failed_promise = true;
2311 if (mo_graph->checkPromise(write, promise)) {
2312 priv->failed_promise = true;
2317 //Don't do any lookups twice for the same thread
2318 if (promise->has_sync_thread(tid))
2321 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2322 if (promise->increment_threads(tid)) {
2323 priv->failed_promise = true;
2331 * Compute the set of writes that may break the current pending release
2332 * sequence. This information is extracted from previou release sequence
2335 * @param curr The current ModelAction. Must be a release sequence fixup
2338 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2340 if (pending_rel_seqs->empty())
2343 struct release_seq *pending = pending_rel_seqs->back();
2344 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2345 const ModelAction *write = pending->writes[i];
2346 curr->get_node()->add_relseq_break(write);
2349 /* NULL means don't break the sequence; just synchronize */
2350 curr->get_node()->add_relseq_break(NULL);
2354 * Build up an initial set of all past writes that this 'read' action may read
2355 * from. This set is determined by the clock vector's "happens before"
2357 * @param curr is the current ModelAction that we are exploring; it must be a
2360 void ModelChecker::build_reads_from_past(ModelAction *curr)
2362 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2364 ASSERT(curr->is_read());
2366 ModelAction *last_sc_write = NULL;
2368 /* Track whether this object has been initialized */
2369 bool initialized = false;
2371 if (curr->is_seqcst()) {
2372 last_sc_write = get_last_seq_cst_write(curr);
2373 /* We have to at least see the last sequentially consistent write,
2374 so we are initialized. */
2375 if (last_sc_write != NULL)
2379 /* Iterate over all threads */
2380 for (i = 0; i < thrd_lists->size(); i++) {
2381 /* Iterate over actions in thread, starting from most recent */
2382 action_list_t *list = &(*thrd_lists)[i];
2383 action_list_t::reverse_iterator rit;
2384 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2385 ModelAction *act = *rit;
2387 /* Only consider 'write' actions */
2388 if (!act->is_write() || act == curr)
2391 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2392 bool allow_read = true;
2394 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2396 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2400 DEBUG("Adding action to may_read_from:\n");
2401 if (DBG_ENABLED()) {
2405 curr->get_node()->add_read_from(act);
2408 /* Include at most one act per-thread that "happens before" curr */
2409 if (act->happens_before(curr)) {
2417 assert_bug("May read from uninitialized atomic");
2419 if (DBG_ENABLED() || !initialized) {
2420 model_print("Reached read action:\n");
2422 model_print("Printing may_read_from\n");
2423 curr->get_node()->print_may_read_from();
2424 model_print("End printing may_read_from\n");
2428 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2430 Node *prevnode=write->get_node()->get_parent();
2432 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2433 if (write->is_release()&&thread_sleep)
2435 if (!write->is_rmw()) {
2438 if (write->get_reads_from()==NULL)
2440 write=write->get_reads_from();
2444 static void print_list(action_list_t *list, int exec_num = -1)
2446 action_list_t::iterator it;
2448 model_print("---------------------------------------------------------------------\n");
2450 model_print("Execution %d:\n", exec_num);
2452 unsigned int hash=0;
2454 for (it = list->begin(); it != list->end(); it++) {
2456 hash=hash^(hash<<3)^((*it)->hash());
2458 model_print("HASH %u\n", hash);
2459 model_print("---------------------------------------------------------------------\n");
2462 #if SUPPORT_MOD_ORDER_DUMP
2463 void ModelChecker::dumpGraph(char *filename) {
2465 sprintf(buffer, "%s.dot",filename);
2466 FILE *file=fopen(buffer, "w");
2467 fprintf(file, "digraph %s {\n",filename);
2468 mo_graph->dumpNodes(file);
2469 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2471 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2472 ModelAction *action=*it;
2473 if (action->is_read()) {
2474 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2475 if (action->get_reads_from()!=NULL)
2476 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2478 if (thread_array[action->get_tid()] != NULL) {
2479 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2482 thread_array[action->get_tid()]=action;
2484 fprintf(file,"}\n");
2485 model_free(thread_array);
2490 /** @brief Prints an execution trace summary. */
2491 void ModelChecker::print_summary() const
2493 #if SUPPORT_MOD_ORDER_DUMP
2495 char buffername[100];
2496 sprintf(buffername, "exec%04u", stats.num_total);
2497 mo_graph->dumpGraphToFile(buffername);
2498 sprintf(buffername, "graph%04u", stats.num_total);
2499 dumpGraph(buffername);
2502 if (!isfeasibleprefix())
2503 model_print("INFEASIBLE EXECUTION!\n");
2504 print_list(action_trace, stats.num_total);
2509 * Add a Thread to the system for the first time. Should only be called once
2511 * @param t The Thread to add
2513 void ModelChecker::add_thread(Thread *t)
2515 thread_map->put(id_to_int(t->get_id()), t);
2516 scheduler->add_thread(t);
2520 * Removes a thread from the scheduler.
2521 * @param the thread to remove.
2523 void ModelChecker::remove_thread(Thread *t)
2525 scheduler->remove_thread(t);
2529 * @brief Get a Thread reference by its ID
2530 * @param tid The Thread's ID
2531 * @return A Thread reference
2533 Thread * ModelChecker::get_thread(thread_id_t tid) const
2535 return thread_map->get(id_to_int(tid));
2539 * @brief Get a reference to the Thread in which a ModelAction was executed
2540 * @param act The ModelAction
2541 * @return A Thread reference
2543 Thread * ModelChecker::get_thread(ModelAction *act) const
2545 return get_thread(act->get_tid());
2549 * @brief Check if a Thread is currently enabled
2550 * @param t The Thread to check
2551 * @return True if the Thread is currently enabled
2553 bool ModelChecker::is_enabled(Thread *t) const
2555 return scheduler->is_enabled(t);
2559 * @brief Check if a Thread is currently enabled
2560 * @param tid The ID of the Thread to check
2561 * @return True if the Thread is currently enabled
2563 bool ModelChecker::is_enabled(thread_id_t tid) const
2565 return scheduler->is_enabled(tid);
2569 * Switch from a user-context to the "master thread" context (a.k.a. system
2570 * context). This switch is made with the intention of exploring a particular
2571 * model-checking action (described by a ModelAction object). Must be called
2572 * from a user-thread context.
2574 * @param act The current action that will be explored. May be NULL only if
2575 * trace is exiting via an assertion (see ModelChecker::set_assert and
2576 * ModelChecker::has_asserted).
2577 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2579 int ModelChecker::switch_to_master(ModelAction *act)
2582 Thread *old = thread_current();
2583 set_current_action(act);
2584 old->set_state(THREAD_READY);
2585 return Thread::swap(old, &system_context);
2589 * Takes the next step in the execution, if possible.
2590 * @return Returns true (success) if a step was taken and false otherwise.
2592 bool ModelChecker::take_step() {
2596 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2598 if (curr->get_state() == THREAD_READY) {
2599 ASSERT(priv->current_action);
2601 priv->nextThread = check_current_action(priv->current_action);
2602 priv->current_action = NULL;
2604 if (curr->is_blocked() || curr->is_complete())
2605 scheduler->remove_thread(curr);
2610 Thread *next = scheduler->next_thread(priv->nextThread);
2612 /* Infeasible -> don't take any more steps */
2613 if (is_infeasible())
2615 else if (isfeasibleprefix() && have_bug_reports()) {
2620 if (params.bound != 0) {
2621 if (priv->used_sequence_numbers > params.bound) {
2626 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2627 next ? id_to_int(next->get_id()) : -1);
2630 * Launch end-of-execution release sequence fixups only when there are:
2632 * (1) no more user threads to run (or when execution replay chooses
2633 * the 'model_thread')
2634 * (2) pending release sequences
2635 * (3) pending assertions (i.e., data races)
2636 * (4) no pending promises
2638 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2639 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2640 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2641 pending_rel_seqs->size());
2642 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2643 std::memory_order_seq_cst, NULL, VALUE_NONE,
2645 set_current_action(fixup);
2649 /* next == NULL -> don't take any more steps */
2653 next->set_state(THREAD_RUNNING);
2655 if (next->get_pending() != NULL) {
2656 /* restart a pending action */
2657 set_current_action(next->get_pending());
2658 next->set_pending(NULL);
2659 next->set_state(THREAD_READY);
2663 /* Return false only if swap fails with an error */
2664 return (Thread::swap(&system_context, next) == 0);
2667 /** Wrapper to run the user's main function, with appropriate arguments */
2668 void user_main_wrapper(void *)
2670 user_main(model->params.argc, model->params.argv);
2673 /** @brief Run ModelChecker for the user program */
2674 void ModelChecker::run()
2679 /* Start user program */
2680 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2682 /* Wait for all threads to complete */
2683 while (take_step());
2684 } while (next_execution());