9 #include "snapshot-interface.h"
11 #include "clockvector.h"
12 #include "cyclegraph.h"
15 #include "threads-model.h"
17 #define INITIAL_THREAD_ID 0
21 /** @brief Constructor */
22 ModelChecker::ModelChecker(struct model_params params) :
23 /* Initialize default scheduler */
25 scheduler(new Scheduler()),
27 num_feasible_executions(0),
29 earliest_diverge(NULL),
30 action_trace(new action_list_t()),
31 thread_map(new HashTable<int, Thread *, int>()),
32 obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
33 lock_waiters_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
34 condvar_waiters_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
35 obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
36 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
37 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
38 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
39 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
40 node_stack(new NodeStack()),
41 mo_graph(new CycleGraph()),
42 failed_promise(false),
43 too_many_reads(false),
45 bad_synchronization(false)
47 /* Allocate this "size" on the snapshotting heap */
48 priv = (struct model_snapshot_members *)calloc(1, sizeof(*priv));
49 /* First thread created will have id INITIAL_THREAD_ID */
50 priv->next_thread_id = INITIAL_THREAD_ID;
52 /* Initialize a model-checker thread, for special ModelActions */
53 model_thread = new Thread(get_next_id());
54 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
57 /** @brief Destructor */
58 ModelChecker::~ModelChecker()
60 for (unsigned int i = 0; i < get_num_threads(); i++)
61 delete thread_map->get(i);
66 delete lock_waiters_map;
67 delete condvar_waiters_map;
70 for (unsigned int i = 0; i < promises->size(); i++)
71 delete (*promises)[i];
74 delete pending_rel_seqs;
76 delete thrd_last_action;
83 * Restores user program to initial state and resets all model-checker data
86 void ModelChecker::reset_to_initial_state()
88 DEBUG("+++ Resetting to initial state +++\n");
89 node_stack->reset_execution();
90 failed_promise = false;
91 too_many_reads = false;
92 bad_synchronization = false;
94 snapshotObject->backTrackBeforeStep(0);
97 /** @return a thread ID for a new Thread */
98 thread_id_t ModelChecker::get_next_id()
100 return priv->next_thread_id++;
103 /** @return the number of user threads created during this execution */
104 unsigned int ModelChecker::get_num_threads()
106 return priv->next_thread_id;
109 /** @return The currently executing Thread. */
110 Thread * ModelChecker::get_current_thread()
112 return scheduler->get_current_thread();
115 /** @return a sequence number for a new ModelAction */
116 modelclock_t ModelChecker::get_next_seq_num()
118 return ++priv->used_sequence_numbers;
121 Node * ModelChecker::get_curr_node() {
122 return node_stack->get_head();
126 * @brief Choose the next thread to execute.
128 * This function chooses the next thread that should execute. It can force the
129 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
130 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
131 * The model-checker may have no preference regarding the next thread (i.e.,
132 * when exploring a new execution ordering), in which case this will return
134 * @param curr The current ModelAction. This action might guide the choice of
136 * @return The next thread to run. If the model-checker has no preference, NULL.
138 Thread * ModelChecker::get_next_thread(ModelAction *curr)
143 /* Do not split atomic actions. */
145 return thread_current();
146 /* The THREAD_CREATE action points to the created Thread */
147 else if (curr->get_type() == THREAD_CREATE)
148 return (Thread *)curr->get_location();
151 /* Have we completed exploring the preselected path? */
155 /* Else, we are trying to replay an execution */
156 ModelAction *next = node_stack->get_next()->get_action();
158 if (next == diverge) {
159 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
160 earliest_diverge=diverge;
162 Node *nextnode = next->get_node();
163 Node *prevnode = nextnode->get_parent();
164 scheduler->update_sleep_set(prevnode);
166 /* Reached divergence point */
167 if (nextnode->increment_misc()) {
168 /* The next node will try to satisfy a different misc_index values. */
169 tid = next->get_tid();
170 node_stack->pop_restofstack(2);
171 } else if (nextnode->increment_promise()) {
172 /* The next node will try to satisfy a different set of promises. */
173 tid = next->get_tid();
174 node_stack->pop_restofstack(2);
175 } else if (nextnode->increment_read_from()) {
176 /* The next node will read from a different value. */
177 tid = next->get_tid();
178 node_stack->pop_restofstack(2);
179 } else if (nextnode->increment_future_value()) {
180 /* The next node will try to read from a different future value. */
181 tid = next->get_tid();
182 node_stack->pop_restofstack(2);
183 } else if (nextnode->increment_relseq_break()) {
184 /* The next node will try to resolve a release sequence differently */
185 tid = next->get_tid();
186 node_stack->pop_restofstack(2);
188 /* Make a different thread execute for next step */
189 scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid())));
190 tid = prevnode->get_next_backtrack();
191 /* Make sure the backtracked thread isn't sleeping. */
192 node_stack->pop_restofstack(1);
193 if (diverge==earliest_diverge) {
194 earliest_diverge=prevnode->get_action();
197 /* The correct sleep set is in the parent node. */
200 DEBUG("*** Divergence point ***\n");
204 tid = next->get_tid();
206 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
207 ASSERT(tid != THREAD_ID_T_NONE);
208 return thread_map->get(id_to_int(tid));
212 * We need to know what the next actions of all threads in the sleep
213 * set will be. This method computes them and stores the actions at
214 * the corresponding thread object's pending action.
217 void ModelChecker::execute_sleep_set() {
218 for(unsigned int i=0;i<get_num_threads();i++) {
219 thread_id_t tid=int_to_id(i);
220 Thread *thr=get_thread(tid);
221 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
222 thr->set_state(THREAD_RUNNING);
223 scheduler->next_thread(thr);
224 Thread::swap(&system_context, thr);
225 priv->current_action->set_sleep_flag();
226 thr->set_pending(priv->current_action);
229 priv->current_action = NULL;
232 void ModelChecker::wake_up_sleeping_actions(ModelAction * curr) {
233 for(unsigned int i=0;i<get_num_threads();i++) {
234 thread_id_t tid=int_to_id(i);
235 Thread *thr=get_thread(tid);
236 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
237 ModelAction *pending_act=thr->get_pending();
238 if (pending_act->could_synchronize_with(curr)) {
239 //Remove this thread from sleep set
240 scheduler->remove_sleep(thr);
247 * Queries the model-checker for more executions to explore and, if one
248 * exists, resets the model-checker state to execute a new execution.
250 * @return If there are more executions to explore, return true. Otherwise,
253 bool ModelChecker::next_execution()
259 if (isfinalfeasible()) {
260 printf("Earliest divergence point since last feasible execution:\n");
261 if (earliest_diverge)
262 earliest_diverge->print();
264 printf("(Not set)\n");
266 earliest_diverge = NULL;
267 num_feasible_executions++;
270 DEBUG("Number of acquires waiting on pending release sequences: %zu\n",
271 pending_rel_seqs->size());
274 if (isfinalfeasible() || (params.bound != 0 && priv->used_sequence_numbers > params.bound ) || DBG_ENABLED() )
277 if ((diverge = get_next_backtrack()) == NULL)
281 printf("Next execution will diverge at:\n");
285 reset_to_initial_state();
289 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
291 switch (act->get_type()) {
295 /* linear search: from most recent to oldest */
296 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
297 action_list_t::reverse_iterator rit;
298 for (rit = list->rbegin(); rit != list->rend(); rit++) {
299 ModelAction *prev = *rit;
300 if (prev->could_synchronize_with(act))
306 case ATOMIC_TRYLOCK: {
307 /* linear search: from most recent to oldest */
308 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
309 action_list_t::reverse_iterator rit;
310 for (rit = list->rbegin(); rit != list->rend(); rit++) {
311 ModelAction *prev = *rit;
312 if (act->is_conflicting_lock(prev))
317 case ATOMIC_UNLOCK: {
318 /* linear search: from most recent to oldest */
319 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
320 action_list_t::reverse_iterator rit;
321 for (rit = list->rbegin(); rit != list->rend(); rit++) {
322 ModelAction *prev = *rit;
323 if (!act->same_thread(prev)&&prev->is_failed_trylock())
329 /* linear search: from most recent to oldest */
330 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
331 action_list_t::reverse_iterator rit;
332 for (rit = list->rbegin(); rit != list->rend(); rit++) {
333 ModelAction *prev = *rit;
334 if (!act->same_thread(prev)&&prev->is_failed_trylock())
336 if (!act->same_thread(prev)&&prev->is_notify())
342 case ATOMIC_NOTIFY_ALL:
343 case ATOMIC_NOTIFY_ONE: {
344 /* linear search: from most recent to oldest */
345 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
346 action_list_t::reverse_iterator rit;
347 for (rit = list->rbegin(); rit != list->rend(); rit++) {
348 ModelAction *prev = *rit;
349 if (!act->same_thread(prev)&&prev->is_wait())
360 /** This method finds backtracking points where we should try to
361 * reorder the parameter ModelAction against.
363 * @param the ModelAction to find backtracking points for.
365 void ModelChecker::set_backtracking(ModelAction *act)
367 Thread *t = get_thread(act);
368 ModelAction * prev = get_last_conflict(act);
372 Node * node = prev->get_node()->get_parent();
374 int low_tid, high_tid;
375 if (node->is_enabled(t)) {
376 low_tid = id_to_int(act->get_tid());
377 high_tid = low_tid+1;
380 high_tid = get_num_threads();
383 for(int i = low_tid; i < high_tid; i++) {
384 thread_id_t tid = int_to_id(i);
386 /* Don't backtrack into a point where the thread is disabled or sleeping. */
387 if (node->get_enabled_array()[i]!=THREAD_ENABLED)
390 /* Check if this has been explored already */
391 if (node->has_been_explored(tid))
394 /* See if fairness allows */
395 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
397 for(int t=0;t<node->get_num_threads();t++) {
398 thread_id_t tother=int_to_id(t);
399 if (node->is_enabled(tother) && node->has_priority(tother)) {
407 /* Cache the latest backtracking point */
408 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
409 priv->next_backtrack = prev;
411 /* If this is a new backtracking point, mark the tree */
412 if (!node->set_backtrack(tid))
414 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
415 id_to_int(prev->get_tid()),
416 id_to_int(t->get_id()));
425 * Returns last backtracking point. The model checker will explore a different
426 * path for this point in the next execution.
427 * @return The ModelAction at which the next execution should diverge.
429 ModelAction * ModelChecker::get_next_backtrack()
431 ModelAction *next = priv->next_backtrack;
432 priv->next_backtrack = NULL;
437 * Processes a read or rmw model action.
438 * @param curr is the read model action to process.
439 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
440 * @return True if processing this read updates the mo_graph.
442 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
444 uint64_t value = VALUE_NONE;
445 bool updated = false;
447 const ModelAction *reads_from = curr->get_node()->get_read_from();
448 if (reads_from != NULL) {
449 mo_graph->startChanges();
451 value = reads_from->get_value();
452 bool r_status = false;
454 if (!second_part_of_rmw) {
455 check_recency(curr, reads_from);
456 r_status = r_modification_order(curr, reads_from);
460 if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
461 mo_graph->rollbackChanges();
462 too_many_reads = false;
466 curr->read_from(reads_from);
467 mo_graph->commitChanges();
468 mo_check_promises(curr->get_tid(), reads_from);
471 } else if (!second_part_of_rmw) {
472 /* Read from future value */
473 value = curr->get_node()->get_future_value();
474 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
475 curr->read_from(NULL);
476 Promise *valuepromise = new Promise(curr, value, expiration);
477 promises->push_back(valuepromise);
479 get_thread(curr)->set_return_value(value);
485 * Processes a lock, trylock, or unlock model action. @param curr is
486 * the read model action to process.
488 * The try lock operation checks whether the lock is taken. If not,
489 * it falls to the normal lock operation case. If so, it returns
492 * The lock operation has already been checked that it is enabled, so
493 * it just grabs the lock and synchronizes with the previous unlock.
495 * The unlock operation has to re-enable all of the threads that are
496 * waiting on the lock.
498 * @return True if synchronization was updated; false otherwise
500 bool ModelChecker::process_mutex(ModelAction *curr) {
501 std::mutex *mutex=NULL;
502 struct std::mutex_state *state=NULL;
504 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
505 mutex = (std::mutex *)curr->get_location();
506 state = mutex->get_state();
507 } else if(curr->is_wait()) {
508 mutex = (std::mutex *)curr->get_value();
509 state = mutex->get_state();
512 switch (curr->get_type()) {
513 case ATOMIC_TRYLOCK: {
514 bool success = !state->islocked;
515 curr->set_try_lock(success);
517 get_thread(curr)->set_return_value(0);
520 get_thread(curr)->set_return_value(1);
522 //otherwise fall into the lock case
524 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock) {
525 printf("Lock access before initialization\n");
528 state->islocked = true;
529 ModelAction *unlock = get_last_unlock(curr);
530 //synchronize with the previous unlock statement
531 if (unlock != NULL) {
532 curr->synchronize_with(unlock);
537 case ATOMIC_UNLOCK: {
539 state->islocked = false;
540 //wake up the other threads
541 action_list_t *waiters = lock_waiters_map->get_safe_ptr(curr->get_location());
542 //activate all the waiting threads
543 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
544 scheduler->wake(get_thread(*rit));
551 state->islocked = false;
552 //wake up the other threads
553 action_list_t *waiters = lock_waiters_map->get_safe_ptr((void *) curr->get_value());
554 //activate all the waiting threads
555 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
556 scheduler->wake(get_thread(*rit));
559 //check whether we should go to sleep or not...simulate spurious failures
560 if (curr->get_node()->get_misc()==0) {
561 condvar_waiters_map->get_safe_ptr(curr->get_location())->push_back(curr);
563 scheduler->sleep(get_current_thread());
567 case ATOMIC_NOTIFY_ALL: {
568 action_list_t *waiters = condvar_waiters_map->get_safe_ptr(curr->get_location());
569 //activate all the waiting threads
570 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
571 scheduler->wake(get_thread(*rit));
576 case ATOMIC_NOTIFY_ONE: {
577 action_list_t *waiters = condvar_waiters_map->get_safe_ptr(curr->get_location());
578 int wakeupthread=curr->get_node()->get_misc();
579 action_list_t::iterator it = waiters->begin();
580 advance(it, wakeupthread);
581 scheduler->wake(get_thread(*it));
593 * Process a write ModelAction
594 * @param curr The ModelAction to process
595 * @return True if the mo_graph was updated or promises were resolved
597 bool ModelChecker::process_write(ModelAction *curr)
599 bool updated_mod_order = w_modification_order(curr);
600 bool updated_promises = resolve_promises(curr);
602 if (promises->size() == 0) {
603 for (unsigned int i = 0; i < futurevalues->size(); i++) {
604 struct PendingFutureValue pfv = (*futurevalues)[i];
605 //Do more ambitious checks now that mo is more complete
606 if (mo_may_allow(pfv.writer, pfv.act)&&
607 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number()+params.maxfuturedelay) &&
608 (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
609 priv->next_backtrack = pfv.act;
611 futurevalues->resize(0);
614 mo_graph->commitChanges();
615 mo_check_promises(curr->get_tid(), curr);
617 get_thread(curr)->set_return_value(VALUE_NONE);
618 return updated_mod_order || updated_promises;
622 * @brief Process the current action for thread-related activity
624 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
625 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
626 * synchronization, etc. This function is a no-op for non-THREAD actions
627 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
629 * @param curr The current action
630 * @return True if synchronization was updated or a thread completed
632 bool ModelChecker::process_thread_action(ModelAction *curr)
634 bool updated = false;
636 switch (curr->get_type()) {
637 case THREAD_CREATE: {
638 Thread *th = (Thread *)curr->get_location();
639 th->set_creation(curr);
643 Thread *blocking = (Thread *)curr->get_location();
644 ModelAction *act = get_last_action(blocking->get_id());
645 curr->synchronize_with(act);
646 updated = true; /* trigger rel-seq checks */
649 case THREAD_FINISH: {
650 Thread *th = get_thread(curr);
651 while (!th->wait_list_empty()) {
652 ModelAction *act = th->pop_wait_list();
653 scheduler->wake(get_thread(act));
656 updated = true; /* trigger rel-seq checks */
660 check_promises(curr->get_tid(), NULL, curr->get_cv());
671 * @brief Process the current action for release sequence fixup activity
673 * Performs model-checker release sequence fixups for the current action,
674 * forcing a single pending release sequence to break (with a given, potential
675 * "loose" write) or to complete (i.e., synchronize). If a pending release
676 * sequence forms a complete release sequence, then we must perform the fixup
677 * synchronization, mo_graph additions, etc.
679 * @param curr The current action; must be a release sequence fixup action
680 * @param work_queue The work queue to which to add work items as they are
683 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
685 const ModelAction *write = curr->get_node()->get_relseq_break();
686 struct release_seq *sequence = pending_rel_seqs->back();
687 pending_rel_seqs->pop_back();
689 ModelAction *acquire = sequence->acquire;
690 const ModelAction *rf = sequence->rf;
691 const ModelAction *release = sequence->release;
695 ASSERT(release->same_thread(rf));
699 * @todo Forcing a synchronization requires that we set
700 * modification order constraints. For instance, we can't allow
701 * a fixup sequence in which two separate read-acquire
702 * operations read from the same sequence, where the first one
703 * synchronizes and the other doesn't. Essentially, we can't
704 * allow any writes to insert themselves between 'release' and
708 /* Must synchronize */
709 if (!acquire->synchronize_with(release)) {
710 set_bad_synchronization();
713 /* Re-check all pending release sequences */
714 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
715 /* Re-check act for mo_graph edges */
716 work_queue->push_back(MOEdgeWorkEntry(acquire));
718 /* propagate synchronization to later actions */
719 action_list_t::reverse_iterator rit = action_trace->rbegin();
720 for (; (*rit) != acquire; rit++) {
721 ModelAction *propagate = *rit;
722 if (acquire->happens_before(propagate)) {
723 propagate->synchronize_with(acquire);
724 /* Re-check 'propagate' for mo_graph edges */
725 work_queue->push_back(MOEdgeWorkEntry(propagate));
729 /* Break release sequence with new edges:
730 * release --mo--> write --mo--> rf */
731 mo_graph->addEdge(release, write);
732 mo_graph->addEdge(write, rf);
735 /* See if we have realized a data race */
736 if (checkDataRaces())
741 * Initialize the current action by performing one or more of the following
742 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
743 * in the NodeStack, manipulating backtracking sets, allocating and
744 * initializing clock vectors, and computing the promises to fulfill.
746 * @param curr The current action, as passed from the user context; may be
747 * freed/invalidated after the execution of this function
748 * @return The current action, as processed by the ModelChecker. Is only the
749 * same as the parameter @a curr if this is a newly-explored action.
751 ModelAction * ModelChecker::initialize_curr_action(ModelAction *curr)
753 ModelAction *newcurr;
755 if (curr->is_rmwc() || curr->is_rmw()) {
756 newcurr = process_rmw(curr);
759 if (newcurr->is_rmw())
760 compute_promises(newcurr);
764 curr->set_seq_number(get_next_seq_num());
766 newcurr = node_stack->explore_action(curr, scheduler->get_enabled());
768 /* First restore type and order in case of RMW operation */
770 newcurr->copy_typeandorder(curr);
772 ASSERT(curr->get_location() == newcurr->get_location());
773 newcurr->copy_from_new(curr);
775 /* Discard duplicate ModelAction; use action from NodeStack */
778 /* Always compute new clock vector */
779 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
783 /* Always compute new clock vector */
784 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
786 * Perform one-time actions when pushing new ModelAction onto
789 if (newcurr->is_write())
790 compute_promises(newcurr);
791 else if (newcurr->is_relseq_fixup())
792 compute_relseq_breakwrites(newcurr);
793 else if (newcurr->is_wait())
794 newcurr->get_node()->set_misc_max(2);
795 else if (newcurr->is_notify_one()) {
796 newcurr->get_node()->set_misc_max(condvar_waiters_map->get_safe_ptr(newcurr->get_location())->size());
803 * @brief Check whether a model action is enabled.
805 * Checks whether a lock or join operation would be successful (i.e., is the
806 * lock already locked, or is the joined thread already complete). If not, put
807 * the action in a waiter list.
809 * @param curr is the ModelAction to check whether it is enabled.
810 * @return a bool that indicates whether the action is enabled.
812 bool ModelChecker::check_action_enabled(ModelAction *curr) {
813 if (curr->is_lock()) {
814 std::mutex * lock = (std::mutex *)curr->get_location();
815 struct std::mutex_state * state = lock->get_state();
816 if (state->islocked) {
817 //Stick the action in the appropriate waiting queue
818 lock_waiters_map->get_safe_ptr(curr->get_location())->push_back(curr);
821 } else if (curr->get_type() == THREAD_JOIN) {
822 Thread *blocking = (Thread *)curr->get_location();
823 if (!blocking->is_complete()) {
824 blocking->push_wait_list(curr);
833 * This is the heart of the model checker routine. It performs model-checking
834 * actions corresponding to a given "current action." Among other processes, it
835 * calculates reads-from relationships, updates synchronization clock vectors,
836 * forms a memory_order constraints graph, and handles replay/backtrack
837 * execution when running permutations of previously-observed executions.
839 * @param curr The current action to process
840 * @return The next Thread that must be executed. May be NULL if ModelChecker
841 * makes no choice (e.g., according to replay execution, combining RMW actions,
844 Thread * ModelChecker::check_current_action(ModelAction *curr)
847 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
849 if (!check_action_enabled(curr)) {
850 /* Make the execution look like we chose to run this action
851 * much later, when a lock/join can succeed */
852 get_current_thread()->set_pending(curr);
853 scheduler->sleep(get_current_thread());
854 return get_next_thread(NULL);
857 ModelAction *newcurr = initialize_curr_action(curr);
859 wake_up_sleeping_actions(curr);
861 /* Add the action to lists before any other model-checking tasks */
862 if (!second_part_of_rmw)
863 add_action_to_lists(newcurr);
865 /* Build may_read_from set for newly-created actions */
866 if (curr == newcurr && curr->is_read())
867 build_reads_from_past(curr);
870 /* Initialize work_queue with the "current action" work */
871 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
872 while (!work_queue.empty()) {
873 WorkQueueEntry work = work_queue.front();
874 work_queue.pop_front();
877 case WORK_CHECK_CURR_ACTION: {
878 ModelAction *act = work.action;
879 bool update = false; /* update this location's release seq's */
880 bool update_all = false; /* update all release seq's */
882 if (process_thread_action(curr))
885 if (act->is_read() && process_read(act, second_part_of_rmw))
888 if (act->is_write() && process_write(act))
891 if (act->is_mutex_op() && process_mutex(act))
894 if (act->is_relseq_fixup())
895 process_relseq_fixup(curr, &work_queue);
898 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
900 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
903 case WORK_CHECK_RELEASE_SEQ:
904 resolve_release_sequences(work.location, &work_queue);
906 case WORK_CHECK_MO_EDGES: {
907 /** @todo Complete verification of work_queue */
908 ModelAction *act = work.action;
909 bool updated = false;
911 if (act->is_read()) {
912 const ModelAction *rf = act->get_reads_from();
913 if (rf != NULL && r_modification_order(act, rf))
916 if (act->is_write()) {
917 if (w_modification_order(act))
920 mo_graph->commitChanges();
923 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
932 check_curr_backtracking(curr);
933 set_backtracking(curr);
934 return get_next_thread(curr);
937 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
938 Node *currnode = curr->get_node();
939 Node *parnode = currnode->get_parent();
941 if ((!parnode->backtrack_empty() ||
942 !currnode->misc_empty() ||
943 !currnode->read_from_empty() ||
944 !currnode->future_value_empty() ||
945 !currnode->promise_empty() ||
946 !currnode->relseq_break_empty())
947 && (!priv->next_backtrack ||
948 *curr > *priv->next_backtrack)) {
949 priv->next_backtrack = curr;
953 bool ModelChecker::promises_expired() {
954 for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
955 Promise *promise = (*promises)[promise_index];
956 if (promise->get_expiration()<priv->used_sequence_numbers) {
963 /** @return whether the current partial trace must be a prefix of a
965 bool ModelChecker::isfeasibleprefix() {
966 return promises->size() == 0 && pending_rel_seqs->size() == 0;
969 /** @return whether the current partial trace is feasible. */
970 bool ModelChecker::isfeasible() {
971 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
972 DEBUG("Infeasible: RMW violation\n");
974 return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW();
977 /** @return whether the current partial trace is feasible other than
978 * multiple RMW reading from the same store. */
979 bool ModelChecker::isfeasibleotherthanRMW() {
981 if (mo_graph->checkForCycles())
982 DEBUG("Infeasible: modification order cycles\n");
984 DEBUG("Infeasible: failed promise\n");
986 DEBUG("Infeasible: too many reads\n");
987 if (bad_synchronization)
988 DEBUG("Infeasible: bad synchronization ordering\n");
989 if (promises_expired())
990 DEBUG("Infeasible: promises expired\n");
992 return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !bad_synchronization && !promises_expired();
995 /** Returns whether the current completed trace is feasible. */
996 bool ModelChecker::isfinalfeasible() {
997 if (DBG_ENABLED() && promises->size() != 0)
998 DEBUG("Infeasible: unrevolved promises\n");
1000 return isfeasible() && promises->size() == 0;
1003 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1004 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1005 ModelAction *lastread = get_last_action(act->get_tid());
1006 lastread->process_rmw(act);
1007 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1008 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1009 mo_graph->commitChanges();
1015 * Checks whether a thread has read from the same write for too many times
1016 * without seeing the effects of a later write.
1019 * 1) there must a different write that we could read from that would satisfy the modification order,
1020 * 2) we must have read from the same value in excess of maxreads times, and
1021 * 3) that other write must have been in the reads_from set for maxreads times.
1023 * If so, we decide that the execution is no longer feasible.
1025 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1026 if (params.maxreads != 0) {
1028 if (curr->get_node()->get_read_from_size() <= 1)
1030 //Must make sure that execution is currently feasible... We could
1031 //accidentally clear by rolling back
1034 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1035 int tid = id_to_int(curr->get_tid());
1038 if ((int)thrd_lists->size() <= tid)
1040 action_list_t *list = &(*thrd_lists)[tid];
1042 action_list_t::reverse_iterator rit = list->rbegin();
1043 /* Skip past curr */
1044 for (; (*rit) != curr; rit++)
1046 /* go past curr now */
1049 action_list_t::reverse_iterator ritcopy = rit;
1050 //See if we have enough reads from the same value
1052 for (; count < params.maxreads; rit++,count++) {
1053 if (rit==list->rend())
1055 ModelAction *act = *rit;
1056 if (!act->is_read())
1059 if (act->get_reads_from() != rf)
1061 if (act->get_node()->get_read_from_size() <= 1)
1064 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1066 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1068 //Need a different write
1072 /* Test to see whether this is a feasible write to read from*/
1073 mo_graph->startChanges();
1074 r_modification_order(curr, write);
1075 bool feasiblereadfrom = isfeasible();
1076 mo_graph->rollbackChanges();
1078 if (!feasiblereadfrom)
1082 bool feasiblewrite = true;
1083 //new we need to see if this write works for everyone
1085 for (int loop = count; loop>0; loop--,rit++) {
1086 ModelAction *act=*rit;
1087 bool foundvalue = false;
1088 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1089 if (act->get_node()->get_read_from_at(i)==write) {
1095 feasiblewrite = false;
1099 if (feasiblewrite) {
1100 too_many_reads = true;
1108 * Updates the mo_graph with the constraints imposed from the current
1111 * Basic idea is the following: Go through each other thread and find
1112 * the lastest action that happened before our read. Two cases:
1114 * (1) The action is a write => that write must either occur before
1115 * the write we read from or be the write we read from.
1117 * (2) The action is a read => the write that that action read from
1118 * must occur before the write we read from or be the same write.
1120 * @param curr The current action. Must be a read.
1121 * @param rf The action that curr reads from. Must be a write.
1122 * @return True if modification order edges were added; false otherwise
1124 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1126 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1129 ASSERT(curr->is_read());
1131 /* Iterate over all threads */
1132 for (i = 0; i < thrd_lists->size(); i++) {
1133 /* Iterate over actions in thread, starting from most recent */
1134 action_list_t *list = &(*thrd_lists)[i];
1135 action_list_t::reverse_iterator rit;
1136 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1137 ModelAction *act = *rit;
1140 * Include at most one act per-thread that "happens
1141 * before" curr. Don't consider reflexively.
1143 if (act->happens_before(curr) && act != curr) {
1144 if (act->is_write()) {
1146 mo_graph->addEdge(act, rf);
1150 const ModelAction *prevreadfrom = act->get_reads_from();
1151 //if the previous read is unresolved, keep going...
1152 if (prevreadfrom == NULL)
1155 if (rf != prevreadfrom) {
1156 mo_graph->addEdge(prevreadfrom, rf);
1168 /** This method fixes up the modification order when we resolve a
1169 * promises. The basic problem is that actions that occur after the
1170 * read curr could not property add items to the modification order
1173 * So for each thread, we find the earliest item that happens after
1174 * the read curr. This is the item we have to fix up with additional
1175 * constraints. If that action is write, we add a MO edge between
1176 * the Action rf and that action. If the action is a read, we add a
1177 * MO edge between the Action rf, and whatever the read accessed.
1179 * @param curr is the read ModelAction that we are fixing up MO edges for.
1180 * @param rf is the write ModelAction that curr reads from.
1183 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1185 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1187 ASSERT(curr->is_read());
1189 /* Iterate over all threads */
1190 for (i = 0; i < thrd_lists->size(); i++) {
1191 /* Iterate over actions in thread, starting from most recent */
1192 action_list_t *list = &(*thrd_lists)[i];
1193 action_list_t::reverse_iterator rit;
1194 ModelAction *lastact = NULL;
1196 /* Find last action that happens after curr that is either not curr or a rmw */
1197 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1198 ModelAction *act = *rit;
1199 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1205 /* Include at most one act per-thread that "happens before" curr */
1206 if (lastact != NULL) {
1207 if (lastact==curr) {
1208 //Case 1: The resolved read is a RMW, and we need to make sure
1209 //that the write portion of the RMW mod order after rf
1211 mo_graph->addEdge(rf, lastact);
1212 } else if (lastact->is_read()) {
1213 //Case 2: The resolved read is a normal read and the next
1214 //operation is a read, and we need to make sure the value read
1215 //is mod ordered after rf
1217 const ModelAction *postreadfrom = lastact->get_reads_from();
1218 if (postreadfrom != NULL&&rf != postreadfrom)
1219 mo_graph->addEdge(rf, postreadfrom);
1221 //Case 3: The resolved read is a normal read and the next
1222 //operation is a write, and we need to make sure that the
1223 //write is mod ordered after rf
1225 mo_graph->addEdge(rf, lastact);
1233 * Updates the mo_graph with the constraints imposed from the current write.
1235 * Basic idea is the following: Go through each other thread and find
1236 * the lastest action that happened before our write. Two cases:
1238 * (1) The action is a write => that write must occur before
1241 * (2) The action is a read => the write that that action read from
1242 * must occur before the current write.
1244 * This method also handles two other issues:
1246 * (I) Sequential Consistency: Making sure that if the current write is
1247 * seq_cst, that it occurs after the previous seq_cst write.
1249 * (II) Sending the write back to non-synchronizing reads.
1251 * @param curr The current action. Must be a write.
1252 * @return True if modification order edges were added; false otherwise
1254 bool ModelChecker::w_modification_order(ModelAction *curr)
1256 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1259 ASSERT(curr->is_write());
1261 if (curr->is_seqcst()) {
1262 /* We have to at least see the last sequentially consistent write,
1263 so we are initialized. */
1264 ModelAction *last_seq_cst = get_last_seq_cst(curr);
1265 if (last_seq_cst != NULL) {
1266 mo_graph->addEdge(last_seq_cst, curr);
1271 /* Iterate over all threads */
1272 for (i = 0; i < thrd_lists->size(); i++) {
1273 /* Iterate over actions in thread, starting from most recent */
1274 action_list_t *list = &(*thrd_lists)[i];
1275 action_list_t::reverse_iterator rit;
1276 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1277 ModelAction *act = *rit;
1280 * 1) If RMW and it actually read from something, then we
1281 * already have all relevant edges, so just skip to next
1284 * 2) If RMW and it didn't read from anything, we should
1285 * whatever edge we can get to speed up convergence.
1287 * 3) If normal write, we need to look at earlier actions, so
1288 * continue processing list.
1290 if (curr->is_rmw()) {
1291 if (curr->get_reads_from()!=NULL)
1300 * Include at most one act per-thread that "happens
1303 if (act->happens_before(curr)) {
1305 * Note: if act is RMW, just add edge:
1307 * The following edge should be handled elsewhere:
1308 * readfrom(act) --mo--> act
1310 if (act->is_write())
1311 mo_graph->addEdge(act, curr);
1312 else if (act->is_read()) {
1313 //if previous read accessed a null, just keep going
1314 if (act->get_reads_from() == NULL)
1316 mo_graph->addEdge(act->get_reads_from(), curr);
1320 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1321 !act->same_thread(curr)) {
1322 /* We have an action that:
1323 (1) did not happen before us
1324 (2) is a read and we are a write
1325 (3) cannot synchronize with us
1326 (4) is in a different thread
1328 that read could potentially read from our write. Note that
1329 these checks are overly conservative at this point, we'll
1330 do more checks before actually removing the
1334 if (thin_air_constraint_may_allow(curr, act)) {
1336 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && isfeasibleotherthanRMW())) {
1337 struct PendingFutureValue pfv = {curr,act};
1338 futurevalues->push_back(pfv);
1348 /** Arbitrary reads from the future are not allowed. Section 29.3
1349 * part 9 places some constraints. This method checks one result of constraint
1350 * constraint. Others require compiler support. */
1351 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1352 if (!writer->is_rmw())
1355 if (!reader->is_rmw())
1358 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1359 if (search == reader)
1361 if (search->get_tid() == reader->get_tid() &&
1362 search->happens_before(reader))
1370 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1371 * some constraints. This method checks one the following constraint (others
1372 * require compiler support):
1374 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1376 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1378 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(reader->get_location());
1381 /* Iterate over all threads */
1382 for (i = 0; i < thrd_lists->size(); i++) {
1383 ModelAction *write_after_read = NULL;
1385 /* Iterate over actions in thread, starting from most recent */
1386 action_list_t *list = &(*thrd_lists)[i];
1387 action_list_t::reverse_iterator rit;
1388 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1389 ModelAction *act = *rit;
1391 if (!reader->happens_before(act))
1393 else if (act->is_write())
1394 write_after_read = act;
1397 if (write_after_read && mo_graph->checkReachable(write_after_read, writer))
1405 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1406 * The ModelAction under consideration is expected to be taking part in
1407 * release/acquire synchronization as an object of the "reads from" relation.
1408 * Note that this can only provide release sequence support for RMW chains
1409 * which do not read from the future, as those actions cannot be traced until
1410 * their "promise" is fulfilled. Similarly, we may not even establish the
1411 * presence of a release sequence with certainty, as some modification order
1412 * constraints may be decided further in the future. Thus, this function
1413 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1414 * and a boolean representing certainty.
1416 * @param rf The action that might be part of a release sequence. Must be a
1418 * @param release_heads A pass-by-reference style return parameter. After
1419 * execution of this function, release_heads will contain the heads of all the
1420 * relevant release sequences, if any exists with certainty
1421 * @param pending A pass-by-reference style return parameter which is only used
1422 * when returning false (i.e., uncertain). Returns most information regarding
1423 * an uncertain release sequence, including any write operations that might
1424 * break the sequence.
1425 * @return true, if the ModelChecker is certain that release_heads is complete;
1428 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1429 rel_heads_list_t *release_heads,
1430 struct release_seq *pending) const
1432 /* Only check for release sequences if there are no cycles */
1433 if (mo_graph->checkForCycles())
1437 ASSERT(rf->is_write());
1439 if (rf->is_release())
1440 release_heads->push_back(rf);
1442 break; /* End of RMW chain */
1444 /** @todo Need to be smarter here... In the linux lock
1445 * example, this will run to the beginning of the program for
1447 /** @todo The way to be smarter here is to keep going until 1
1448 * thread has a release preceded by an acquire and you've seen
1451 /* acq_rel RMW is a sufficient stopping condition */
1452 if (rf->is_acquire() && rf->is_release())
1453 return true; /* complete */
1455 rf = rf->get_reads_from();
1458 /* read from future: need to settle this later */
1460 return false; /* incomplete */
1463 if (rf->is_release())
1464 return true; /* complete */
1466 /* else relaxed write; check modification order for contiguous subsequence
1467 * -> rf must be same thread as release */
1468 int tid = id_to_int(rf->get_tid());
1469 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
1470 action_list_t *list = &(*thrd_lists)[tid];
1471 action_list_t::const_reverse_iterator rit;
1473 /* Find rf in the thread list */
1474 rit = std::find(list->rbegin(), list->rend(), rf);
1475 ASSERT(rit != list->rend());
1477 /* Find the last write/release */
1478 for (; rit != list->rend(); rit++)
1479 if ((*rit)->is_release())
1481 if (rit == list->rend()) {
1482 /* No write-release in this thread */
1483 return true; /* complete */
1485 ModelAction *release = *rit;
1487 ASSERT(rf->same_thread(release));
1489 pending->writes.clear();
1491 bool certain = true;
1492 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1493 if (id_to_int(rf->get_tid()) == (int)i)
1495 list = &(*thrd_lists)[i];
1497 /* Can we ensure no future writes from this thread may break
1498 * the release seq? */
1499 bool future_ordered = false;
1501 ModelAction *last = get_last_action(int_to_id(i));
1502 Thread *th = get_thread(int_to_id(i));
1503 if ((last && rf->happens_before(last)) ||
1504 !scheduler->is_enabled(th) ||
1506 future_ordered = true;
1508 ASSERT(!th->is_model_thread() || future_ordered);
1510 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1511 const ModelAction *act = *rit;
1512 /* Reach synchronization -> this thread is complete */
1513 if (act->happens_before(release))
1515 if (rf->happens_before(act)) {
1516 future_ordered = true;
1520 /* Only non-RMW writes can break release sequences */
1521 if (!act->is_write() || act->is_rmw())
1524 /* Check modification order */
1525 if (mo_graph->checkReachable(rf, act)) {
1526 /* rf --mo--> act */
1527 future_ordered = true;
1530 if (mo_graph->checkReachable(act, release))
1531 /* act --mo--> release */
1533 if (mo_graph->checkReachable(release, act) &&
1534 mo_graph->checkReachable(act, rf)) {
1535 /* release --mo-> act --mo--> rf */
1536 return true; /* complete */
1538 /* act may break release sequence */
1539 pending->writes.push_back(act);
1542 if (!future_ordered)
1543 certain = false; /* This thread is uncertain */
1547 release_heads->push_back(release);
1548 pending->writes.clear();
1550 pending->release = release;
1557 * A public interface for getting the release sequence head(s) with which a
1558 * given ModelAction must synchronize. This function only returns a non-empty
1559 * result when it can locate a release sequence head with certainty. Otherwise,
1560 * it may mark the internal state of the ModelChecker so that it will handle
1561 * the release sequence at a later time, causing @a act to update its
1562 * synchronization at some later point in execution.
1563 * @param act The 'acquire' action that may read from a release sequence
1564 * @param release_heads A pass-by-reference return parameter. Will be filled
1565 * with the head(s) of the release sequence(s), if they exists with certainty.
1566 * @see ModelChecker::release_seq_heads
1568 void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
1570 const ModelAction *rf = act->get_reads_from();
1571 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
1572 sequence->acquire = act;
1574 if (!release_seq_heads(rf, release_heads, sequence)) {
1575 /* add act to 'lazy checking' list */
1576 pending_rel_seqs->push_back(sequence);
1578 snapshot_free(sequence);
1583 * Attempt to resolve all stashed operations that might synchronize with a
1584 * release sequence for a given location. This implements the "lazy" portion of
1585 * determining whether or not a release sequence was contiguous, since not all
1586 * modification order information is present at the time an action occurs.
1588 * @param location The location/object that should be checked for release
1589 * sequence resolutions. A NULL value means to check all locations.
1590 * @param work_queue The work queue to which to add work items as they are
1592 * @return True if any updates occurred (new synchronization, new mo_graph
1595 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
1597 bool updated = false;
1598 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
1599 while (it != pending_rel_seqs->end()) {
1600 struct release_seq *pending = *it;
1601 ModelAction *act = pending->acquire;
1603 /* Only resolve sequences on the given location, if provided */
1604 if (location && act->get_location() != location) {
1609 const ModelAction *rf = act->get_reads_from();
1610 rel_heads_list_t release_heads;
1612 complete = release_seq_heads(rf, &release_heads, pending);
1613 for (unsigned int i = 0; i < release_heads.size(); i++) {
1614 if (!act->has_synchronized_with(release_heads[i])) {
1615 if (act->synchronize_with(release_heads[i]))
1618 set_bad_synchronization();
1623 /* Re-check all pending release sequences */
1624 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1625 /* Re-check act for mo_graph edges */
1626 work_queue->push_back(MOEdgeWorkEntry(act));
1628 /* propagate synchronization to later actions */
1629 action_list_t::reverse_iterator rit = action_trace->rbegin();
1630 for (; (*rit) != act; rit++) {
1631 ModelAction *propagate = *rit;
1632 if (act->happens_before(propagate)) {
1633 propagate->synchronize_with(act);
1634 /* Re-check 'propagate' for mo_graph edges */
1635 work_queue->push_back(MOEdgeWorkEntry(propagate));
1640 it = pending_rel_seqs->erase(it);
1641 snapshot_free(pending);
1647 // If we resolved promises or data races, see if we have realized a data race.
1648 if (checkDataRaces()) {
1656 * Performs various bookkeeping operations for the current ModelAction. For
1657 * instance, adds action to the per-object, per-thread action vector and to the
1658 * action trace list of all thread actions.
1660 * @param act is the ModelAction to add.
1662 void ModelChecker::add_action_to_lists(ModelAction *act)
1664 int tid = id_to_int(act->get_tid());
1665 action_trace->push_back(act);
1667 obj_map->get_safe_ptr(act->get_location())->push_back(act);
1669 std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
1670 if (tid >= (int)vec->size())
1671 vec->resize(priv->next_thread_id);
1672 (*vec)[tid].push_back(act);
1674 if ((int)thrd_last_action->size() <= tid)
1675 thrd_last_action->resize(get_num_threads());
1676 (*thrd_last_action)[tid] = act;
1678 if (act->is_wait()) {
1679 void *mutex_loc=(void *) act->get_value();
1680 obj_map->get_safe_ptr(mutex_loc)->push_back(act);
1682 std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(mutex_loc);
1683 if (tid >= (int)vec->size())
1684 vec->resize(priv->next_thread_id);
1685 (*vec)[tid].push_back(act);
1687 if ((int)thrd_last_action->size() <= tid)
1688 thrd_last_action->resize(get_num_threads());
1689 (*thrd_last_action)[tid] = act;
1694 * @brief Get the last action performed by a particular Thread
1695 * @param tid The thread ID of the Thread in question
1696 * @return The last action in the thread
1698 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
1700 int threadid = id_to_int(tid);
1701 if (threadid < (int)thrd_last_action->size())
1702 return (*thrd_last_action)[id_to_int(tid)];
1708 * Gets the last memory_order_seq_cst write (in the total global sequence)
1709 * performed on a particular object (i.e., memory location), not including the
1711 * @param curr The current ModelAction; also denotes the object location to
1713 * @return The last seq_cst write
1715 ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const
1717 void *location = curr->get_location();
1718 action_list_t *list = obj_map->get_safe_ptr(location);
1719 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1720 action_list_t::reverse_iterator rit;
1721 for (rit = list->rbegin(); rit != list->rend(); rit++)
1722 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
1728 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1729 * location). This function identifies the mutex according to the current
1730 * action, which is presumed to perform on the same mutex.
1731 * @param curr The current ModelAction; also denotes the object location to
1733 * @return The last unlock operation
1735 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
1737 void *location = curr->get_location();
1738 action_list_t *list = obj_map->get_safe_ptr(location);
1739 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1740 action_list_t::reverse_iterator rit;
1741 for (rit = list->rbegin(); rit != list->rend(); rit++)
1742 if ((*rit)->is_unlock() || (*rit)->is_wait())
1747 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
1749 ModelAction *parent = get_last_action(tid);
1751 parent = get_thread(tid)->get_creation();
1756 * Returns the clock vector for a given thread.
1757 * @param tid The thread whose clock vector we want
1758 * @return Desired clock vector
1760 ClockVector * ModelChecker::get_cv(thread_id_t tid)
1762 return get_parent_action(tid)->get_cv();
1766 * Resolve a set of Promises with a current write. The set is provided in the
1767 * Node corresponding to @a write.
1768 * @param write The ModelAction that is fulfilling Promises
1769 * @return True if promises were resolved; false otherwise
1771 bool ModelChecker::resolve_promises(ModelAction *write)
1773 bool resolved = false;
1774 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
1776 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
1777 Promise *promise = (*promises)[promise_index];
1778 if (write->get_node()->get_promise(i)) {
1779 ModelAction *read = promise->get_action();
1780 if (read->is_rmw()) {
1781 mo_graph->addRMWEdge(write, read);
1783 read->read_from(write);
1784 //First fix up the modification order for actions that happened
1786 r_modification_order(read, write);
1787 //Next fix up the modification order for actions that happened
1789 post_r_modification_order(read, write);
1790 //Make sure the promise's value matches the write's value
1791 ASSERT(promise->get_value() == write->get_value());
1794 promises->erase(promises->begin() + promise_index);
1795 threads_to_check.push_back(read->get_tid());
1802 //Check whether reading these writes has made threads unable to
1805 for(unsigned int i=0;i<threads_to_check.size();i++)
1806 mo_check_promises(threads_to_check[i], write);
1812 * Compute the set of promises that could potentially be satisfied by this
1813 * action. Note that the set computation actually appears in the Node, not in
1815 * @param curr The ModelAction that may satisfy promises
1817 void ModelChecker::compute_promises(ModelAction *curr)
1819 for (unsigned int i = 0; i < promises->size(); i++) {
1820 Promise *promise = (*promises)[i];
1821 const ModelAction *act = promise->get_action();
1822 if (!act->happens_before(curr) &&
1824 !act->could_synchronize_with(curr) &&
1825 !act->same_thread(curr) &&
1826 act->get_location() == curr->get_location() &&
1827 promise->get_value() == curr->get_value()) {
1828 curr->get_node()->set_promise(i);
1833 /** Checks promises in response to change in ClockVector Threads. */
1834 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
1836 for (unsigned int i = 0; i < promises->size(); i++) {
1837 Promise *promise = (*promises)[i];
1838 const ModelAction *act = promise->get_action();
1839 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
1840 merge_cv->synchronized_since(act)) {
1841 if (promise->increment_threads(tid)) {
1842 //Promise has failed
1843 failed_promise = true;
1850 /** Checks promises in response to addition to modification order for threads.
1852 * pthread is the thread that performed the read that created the promise
1854 * pread is the read that created the promise
1856 * pwrite is either the first write to same location as pread by
1857 * pthread that is sequenced after pread or the value read by the
1858 * first read to the same lcoation as pread by pthread that is
1859 * sequenced after pread..
1861 * 1. If tid=pthread, then we check what other threads are reachable
1862 * through the mode order starting with pwrite. Those threads cannot
1863 * perform a write that will resolve the promise due to modification
1864 * order constraints.
1866 * 2. If the tid is not pthread, we check whether pwrite can reach the
1867 * action write through the modification order. If so, that thread
1868 * cannot perform a future write that will resolve the promise due to
1869 * modificatin order constraints.
1871 * @parem tid The thread that either read from the model action
1872 * write, or actually did the model action write.
1874 * @parem write The ModelAction representing the relevant write.
1877 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
1878 void * location = write->get_location();
1879 for (unsigned int i = 0; i < promises->size(); i++) {
1880 Promise *promise = (*promises)[i];
1881 const ModelAction *act = promise->get_action();
1883 //Is this promise on the same location?
1884 if ( act->get_location() != location )
1887 //same thread as the promise
1888 if ( act->get_tid()==tid ) {
1890 //do we have a pwrite for the promise, if not, set it
1891 if (promise->get_write() == NULL ) {
1892 promise->set_write(write);
1893 //The pwrite cannot happen before the promise
1894 if (write->happens_before(act) && (write != act)) {
1895 failed_promise = true;
1899 if (mo_graph->checkPromise(write, promise)) {
1900 failed_promise = true;
1905 //Don't do any lookups twice for the same thread
1906 if (promise->has_sync_thread(tid))
1909 if (mo_graph->checkReachable(promise->get_write(), write)) {
1910 if (promise->increment_threads(tid)) {
1911 failed_promise = true;
1919 * Compute the set of writes that may break the current pending release
1920 * sequence. This information is extracted from previou release sequence
1923 * @param curr The current ModelAction. Must be a release sequence fixup
1926 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
1928 if (pending_rel_seqs->empty())
1931 struct release_seq *pending = pending_rel_seqs->back();
1932 for (unsigned int i = 0; i < pending->writes.size(); i++) {
1933 const ModelAction *write = pending->writes[i];
1934 curr->get_node()->add_relseq_break(write);
1937 /* NULL means don't break the sequence; just synchronize */
1938 curr->get_node()->add_relseq_break(NULL);
1942 * Build up an initial set of all past writes that this 'read' action may read
1943 * from. This set is determined by the clock vector's "happens before"
1945 * @param curr is the current ModelAction that we are exploring; it must be a
1948 void ModelChecker::build_reads_from_past(ModelAction *curr)
1950 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1952 ASSERT(curr->is_read());
1954 ModelAction *last_seq_cst = NULL;
1956 /* Track whether this object has been initialized */
1957 bool initialized = false;
1959 if (curr->is_seqcst()) {
1960 last_seq_cst = get_last_seq_cst(curr);
1961 /* We have to at least see the last sequentially consistent write,
1962 so we are initialized. */
1963 if (last_seq_cst != NULL)
1967 /* Iterate over all threads */
1968 for (i = 0; i < thrd_lists->size(); i++) {
1969 /* Iterate over actions in thread, starting from most recent */
1970 action_list_t *list = &(*thrd_lists)[i];
1971 action_list_t::reverse_iterator rit;
1972 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1973 ModelAction *act = *rit;
1975 /* Only consider 'write' actions */
1976 if (!act->is_write() || act == curr)
1979 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1980 if (!curr->is_seqcst() || (!act->is_seqcst() && (last_seq_cst == NULL || !act->happens_before(last_seq_cst))) || act == last_seq_cst) {
1981 DEBUG("Adding action to may_read_from:\n");
1982 if (DBG_ENABLED()) {
1987 if (curr->get_sleep_flag() && ! curr->is_seqcst()) {
1988 if (sleep_can_read_from(curr, act))
1989 curr->get_node()->add_read_from(act);
1991 curr->get_node()->add_read_from(act);
1994 /* Include at most one act per-thread that "happens before" curr */
1995 if (act->happens_before(curr)) {
2003 /** @todo Need a more informative way of reporting errors. */
2004 printf("ERROR: may read from uninitialized atomic\n");
2008 if (DBG_ENABLED() || !initialized) {
2009 printf("Reached read action:\n");
2011 printf("Printing may_read_from\n");
2012 curr->get_node()->print_may_read_from();
2013 printf("End printing may_read_from\n");
2017 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2019 Node *prevnode=write->get_node()->get_parent();
2020 bool thread_sleep=prevnode->get_enabled_array()[id_to_int(curr->get_tid())]==THREAD_SLEEP_SET;
2021 if (write->is_release()&&thread_sleep)
2023 if (!write->is_rmw()) {
2026 if (write->get_reads_from()==NULL)
2028 write=write->get_reads_from();
2032 static void print_list(action_list_t *list)
2034 action_list_t::iterator it;
2036 printf("---------------------------------------------------------------------\n");
2038 unsigned int hash=0;
2040 for (it = list->begin(); it != list->end(); it++) {
2042 hash=hash^(hash<<3)^((*it)->hash());
2044 printf("HASH %u\n", hash);
2045 printf("---------------------------------------------------------------------\n");
2048 #if SUPPORT_MOD_ORDER_DUMP
2049 void ModelChecker::dumpGraph(char *filename) {
2051 sprintf(buffer, "%s.dot",filename);
2052 FILE *file=fopen(buffer, "w");
2053 fprintf(file, "digraph %s {\n",filename);
2054 mo_graph->dumpNodes(file);
2055 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2057 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2058 ModelAction *action=*it;
2059 if (action->is_read()) {
2060 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2061 if (action->get_reads_from()!=NULL)
2062 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2064 if (thread_array[action->get_tid()] != NULL) {
2065 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2068 thread_array[action->get_tid()]=action;
2070 fprintf(file,"}\n");
2071 model_free(thread_array);
2076 void ModelChecker::print_summary()
2079 printf("Number of executions: %d\n", num_executions);
2080 printf("Number of feasible executions: %d\n", num_feasible_executions);
2081 printf("Total nodes created: %d\n", node_stack->get_total_nodes());
2083 #if SUPPORT_MOD_ORDER_DUMP
2085 char buffername[100];
2086 sprintf(buffername, "exec%04u", num_executions);
2087 mo_graph->dumpGraphToFile(buffername);
2088 sprintf(buffername, "graph%04u", num_executions);
2089 dumpGraph(buffername);
2092 if (!isfinalfeasible())
2093 printf("INFEASIBLE EXECUTION!\n");
2094 print_list(action_trace);
2099 * Add a Thread to the system for the first time. Should only be called once
2101 * @param t The Thread to add
2103 void ModelChecker::add_thread(Thread *t)
2105 thread_map->put(id_to_int(t->get_id()), t);
2106 scheduler->add_thread(t);
2110 * Removes a thread from the scheduler.
2111 * @param the thread to remove.
2113 void ModelChecker::remove_thread(Thread *t)
2115 scheduler->remove_thread(t);
2119 * @brief Get a Thread reference by its ID
2120 * @param tid The Thread's ID
2121 * @return A Thread reference
2123 Thread * ModelChecker::get_thread(thread_id_t tid) const
2125 return thread_map->get(id_to_int(tid));
2129 * @brief Get a reference to the Thread in which a ModelAction was executed
2130 * @param act The ModelAction
2131 * @return A Thread reference
2133 Thread * ModelChecker::get_thread(ModelAction *act) const
2135 return get_thread(act->get_tid());
2139 * Switch from a user-context to the "master thread" context (a.k.a. system
2140 * context). This switch is made with the intention of exploring a particular
2141 * model-checking action (described by a ModelAction object). Must be called
2142 * from a user-thread context.
2144 * @param act The current action that will be explored. May be NULL only if
2145 * trace is exiting via an assertion (see ModelChecker::set_assert and
2146 * ModelChecker::has_asserted).
2147 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2149 int ModelChecker::switch_to_master(ModelAction *act)
2152 Thread *old = thread_current();
2153 set_current_action(act);
2154 old->set_state(THREAD_READY);
2155 return Thread::swap(old, &system_context);
2159 * Takes the next step in the execution, if possible.
2160 * @return Returns true (success) if a step was taken and false otherwise.
2162 bool ModelChecker::take_step() {
2166 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2168 if (curr->get_state() == THREAD_READY) {
2169 ASSERT(priv->current_action);
2171 priv->nextThread = check_current_action(priv->current_action);
2172 priv->current_action = NULL;
2174 if (curr->is_blocked() || curr->is_complete())
2175 scheduler->remove_thread(curr);
2180 Thread *next = scheduler->next_thread(priv->nextThread);
2182 /* Infeasible -> don't take any more steps */
2186 if (params.bound != 0) {
2187 if (priv->used_sequence_numbers > params.bound) {
2192 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2193 next ? id_to_int(next->get_id()) : -1);
2196 * Launch end-of-execution release sequence fixups only when there are:
2198 * (1) no more user threads to run (or when execution replay chooses
2199 * the 'model_thread')
2200 * (2) pending release sequences
2201 * (3) pending assertions (i.e., data races)
2202 * (4) no pending promises
2204 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2205 isfinalfeasible() && !unrealizedraces.empty()) {
2206 printf("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2207 pending_rel_seqs->size());
2208 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2209 std::memory_order_seq_cst, NULL, VALUE_NONE,
2211 set_current_action(fixup);
2215 /* next == NULL -> don't take any more steps */
2219 next->set_state(THREAD_RUNNING);
2221 if (next->get_pending() != NULL) {
2222 /* restart a pending action */
2223 set_current_action(next->get_pending());
2224 next->set_pending(NULL);
2225 next->set_state(THREAD_READY);
2229 /* Return false only if swap fails with an error */
2230 return (Thread::swap(&system_context, next) == 0);
2233 /** Runs the current execution until threre are no more steps to take. */
2234 void ModelChecker::finish_execution() {
2237 while (take_step());