7 #include "snapshot-interface.h"
9 #include "clockvector.h"
10 #include "cyclegraph.h"
13 #define INITIAL_THREAD_ID 0
17 /** @brief Constructor */
18 ModelChecker::ModelChecker(struct model_params params) :
19 /* Initialize default scheduler */
20 scheduler(new Scheduler()),
21 /* First thread created will have id INITIAL_THREAD_ID */
22 next_thread_id(INITIAL_THREAD_ID),
23 used_sequence_numbers(0),
29 action_trace(new action_list_t()),
30 thread_map(new HashTable<int, Thread *, int>()),
31 obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
32 obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
33 promises(new std::vector<Promise *>()),
34 lazy_sync_with_release(new HashTable<void *, std::list<ModelAction *>, uintptr_t, 4>()),
35 thrd_last_action(new std::vector<ModelAction *>(1)),
36 node_stack(new NodeStack()),
38 mo_graph(new CycleGraph()),
43 /** @brief Destructor */
44 ModelChecker::~ModelChecker()
46 for (int i = 0; i < get_num_threads(); i++)
47 delete thread_map->get(i);
54 for (unsigned int i = 0; i < promises->size(); i++)
55 delete (*promises)[i];
58 delete lazy_sync_with_release;
60 delete thrd_last_action;
67 * Restores user program to initial state and resets all model-checker data
70 void ModelChecker::reset_to_initial_state()
72 DEBUG("+++ Resetting to initial state +++\n");
73 node_stack->reset_execution();
74 current_action = NULL;
75 next_thread_id = INITIAL_THREAD_ID;
76 used_sequence_numbers = 0;
78 next_backtrack = NULL;
79 failed_promise = false;
80 snapshotObject->backTrackBeforeStep(0);
83 /** @returns a thread ID for a new Thread */
84 thread_id_t ModelChecker::get_next_id()
86 return next_thread_id++;
89 /** @returns the number of user threads created during this execution */
90 int ModelChecker::get_num_threads()
92 return next_thread_id;
95 /** @returns a sequence number for a new ModelAction */
96 modelclock_t ModelChecker::get_next_seq_num()
98 return ++used_sequence_numbers;
102 * Choose the next thread in the replay sequence.
104 * If the replay sequence has reached the 'diverge' point, returns a thread
105 * from the backtracking set. Otherwise, simply returns the next thread in the
106 * sequence that is being replayed.
108 Thread * ModelChecker::get_next_replay_thread()
112 /* Have we completed exploring the preselected path? */
116 /* Else, we are trying to replay an execution */
117 ModelAction *next = node_stack->get_next()->get_action();
119 if (next == diverge) {
120 Node *nextnode = next->get_node();
121 /* Reached divergence point */
122 if (nextnode->increment_promise()) {
123 /* The next node will try to satisfy a different set of promises. */
124 tid = next->get_tid();
125 node_stack->pop_restofstack(2);
126 } else if (nextnode->increment_read_from()) {
127 /* The next node will read from a different value. */
128 tid = next->get_tid();
129 node_stack->pop_restofstack(2);
130 } else if (nextnode->increment_future_value()) {
131 /* The next node will try to read from a different future value. */
132 tid = next->get_tid();
133 node_stack->pop_restofstack(2);
135 /* Make a different thread execute for next step */
136 Node *node = nextnode->get_parent();
137 tid = node->get_next_backtrack();
138 node_stack->pop_restofstack(1);
140 DEBUG("*** Divergence point ***\n");
143 tid = next->get_tid();
145 DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
146 ASSERT(tid != THREAD_ID_T_NONE);
147 return thread_map->get(id_to_int(tid));
151 * Queries the model-checker for more executions to explore and, if one
152 * exists, resets the model-checker state to execute a new execution.
154 * @return If there are more executions to explore, return true. Otherwise,
157 bool ModelChecker::next_execution()
163 if (isfinalfeasible() || DBG_ENABLED())
166 if ((diverge = model->get_next_backtrack()) == NULL)
170 printf("Next execution will diverge at:\n");
174 model->reset_to_initial_state();
178 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
180 action_type type = act->get_type();
190 /* linear search: from most recent to oldest */
191 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
192 action_list_t::reverse_iterator rit;
193 for (rit = list->rbegin(); rit != list->rend(); rit++) {
194 ModelAction *prev = *rit;
195 if (act->is_synchronizing(prev))
201 void ModelChecker::set_backtracking(ModelAction *act)
205 Thread *t = get_thread(act->get_tid());
207 prev = get_last_conflict(act);
211 node = prev->get_node()->get_parent();
213 while (!node->is_enabled(t))
216 /* Check if this has been explored already */
217 if (node->has_been_explored(t->get_id()))
220 /* Cache the latest backtracking point */
221 if (!next_backtrack || *prev > *next_backtrack)
222 next_backtrack = prev;
224 /* If this is a new backtracking point, mark the tree */
225 if (!node->set_backtrack(t->get_id()))
227 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
228 prev->get_tid(), t->get_id());
236 * Returns last backtracking point. The model checker will explore a different
237 * path for this point in the next execution.
238 * @return The ModelAction at which the next execution should diverge.
240 ModelAction * ModelChecker::get_next_backtrack()
242 ModelAction *next = next_backtrack;
243 next_backtrack = NULL;
247 void ModelChecker::check_current_action(void)
249 ModelAction *curr = this->current_action;
250 bool already_added = false;
251 this->current_action = NULL;
253 DEBUG("trying to push NULL action...\n");
257 if (curr->is_rmwc() || curr->is_rmw()) {
258 ModelAction *tmp = process_rmw(curr);
259 already_added = true;
263 ModelAction *tmp = node_stack->explore_action(curr);
265 /* Discard duplicate ModelAction; use action from NodeStack */
266 /* First restore type and order in case of RMW operation */
268 tmp->copy_typeandorder(curr);
270 /* If we have diverged, we need to reset the clock vector. */
272 tmp->create_cv(get_parent_action(tmp->get_tid()));
278 * Perform one-time actions when pushing new ModelAction onto
281 curr->create_cv(get_parent_action(curr->get_tid()));
282 /* Build may_read_from set */
284 build_reads_from_past(curr);
285 if (curr->is_write())
286 compute_promises(curr);
290 /* Assign 'creation' parent */
291 if (curr->get_type() == THREAD_CREATE) {
292 Thread *th = (Thread *)curr->get_location();
293 th->set_creation(curr);
296 /* Deal with new thread */
297 if (curr->get_type() == THREAD_START)
298 check_promises(NULL, curr->get_cv());
300 /* Assign reads_from values */
301 Thread *th = get_thread(curr->get_tid());
302 uint64_t value = VALUE_NONE;
303 bool updated = false;
304 if (curr->is_read()) {
305 const ModelAction *reads_from = curr->get_node()->get_read_from();
306 if (reads_from != NULL) {
307 value = reads_from->get_value();
308 /* Assign reads_from, perform release/acquire synchronization */
309 curr->read_from(reads_from);
310 if (r_modification_order(curr,reads_from))
313 /* Read from future value */
314 value = curr->get_node()->get_future_value();
315 curr->read_from(NULL);
316 Promise *valuepromise = new Promise(curr, value);
317 promises->push_back(valuepromise);
319 } else if (curr->is_write()) {
320 if (w_modification_order(curr))
322 if (resolve_promises(curr))
327 resolve_release_sequences(curr->get_location());
329 th->set_return_value(value);
331 /* Add action to list. */
333 add_action_to_lists(curr);
335 /** @todo Is there a better interface for setting the next thread rather
336 than this field/convoluted approach? Perhaps like just returning
339 /* Do not split atomic actions. */
341 nextThread = thread_current();
343 nextThread = get_next_replay_thread();
345 Node *currnode = curr->get_node();
346 Node *parnode = currnode->get_parent();
348 if (!parnode->backtrack_empty() || !currnode->read_from_empty() ||
349 !currnode->future_value_empty() || !currnode->promise_empty())
350 if (!next_backtrack || *curr > *next_backtrack)
351 next_backtrack = curr;
353 set_backtracking(curr);
356 /** @returns whether the current partial trace is feasible. */
357 bool ModelChecker::isfeasible() {
358 return !mo_graph->checkForCycles() && !failed_promise;
361 /** Returns whether the current completed trace is feasible. */
362 bool ModelChecker::isfinalfeasible() {
363 return isfeasible() && promises->size() == 0;
366 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
367 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
368 int tid = id_to_int(act->get_tid());
369 ModelAction *lastread = get_last_action(tid);
370 lastread->process_rmw(act);
372 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
377 * Updates the mo_graph with the constraints imposed from the current read.
378 * @param curr The current action. Must be a read.
379 * @param rf The action that curr reads from. Must be a write.
380 * @return True if modification order edges were added; false otherwise
382 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
384 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
387 ASSERT(curr->is_read());
389 /* Iterate over all threads */
390 for (i = 0; i < thrd_lists->size(); i++) {
391 /* Iterate over actions in thread, starting from most recent */
392 action_list_t *list = &(*thrd_lists)[i];
393 action_list_t::reverse_iterator rit;
394 for (rit = list->rbegin(); rit != list->rend(); rit++) {
395 ModelAction *act = *rit;
397 /* Include at most one act per-thread that "happens before" curr */
398 if (act->happens_before(curr)) {
399 if (act->is_read()) {
400 const ModelAction *prevreadfrom = act->get_reads_from();
401 if (prevreadfrom != NULL && rf != prevreadfrom) {
402 mo_graph->addEdge(prevreadfrom, rf);
405 } else if (rf != act) {
406 mo_graph->addEdge(act, rf);
417 /** Updates the mo_graph with the constraints imposed from the current read. */
418 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
420 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
422 ASSERT(curr->is_read());
424 /* Iterate over all threads */
425 for (i = 0; i < thrd_lists->size(); i++) {
426 /* Iterate over actions in thread, starting from most recent */
427 action_list_t *list = &(*thrd_lists)[i];
428 action_list_t::reverse_iterator rit;
429 ModelAction *lastact = NULL;
431 /* Find last action that happens after curr */
432 for (rit = list->rbegin(); rit != list->rend(); rit++) {
433 ModelAction *act = *rit;
434 if (curr->happens_before(act)) {
440 /* Include at most one act per-thread that "happens before" curr */
441 if (lastact != NULL) {
442 if (lastact->is_read()) {
443 const ModelAction *postreadfrom = lastact->get_reads_from();
444 if (postreadfrom != NULL&&rf != postreadfrom)
445 mo_graph->addEdge(rf, postreadfrom);
446 } else if (rf != lastact) {
447 mo_graph->addEdge(rf, lastact);
455 * Updates the mo_graph with the constraints imposed from the current write.
456 * @param curr The current action. Must be a write.
457 * @return True if modification order edges were added; false otherwise
459 bool ModelChecker::w_modification_order(ModelAction *curr)
461 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
464 ASSERT(curr->is_write());
466 if (curr->is_seqcst()) {
467 /* We have to at least see the last sequentially consistent write,
468 so we are initialized. */
469 ModelAction *last_seq_cst = get_last_seq_cst(curr->get_location());
470 if (last_seq_cst != NULL) {
471 mo_graph->addEdge(last_seq_cst, curr);
476 /* Iterate over all threads */
477 for (i = 0; i < thrd_lists->size(); i++) {
478 /* Iterate over actions in thread, starting from most recent */
479 action_list_t *list = &(*thrd_lists)[i];
480 action_list_t::reverse_iterator rit;
481 for (rit = list->rbegin(); rit != list->rend(); rit++) {
482 ModelAction *act = *rit;
484 /* Include at most one act per-thread that "happens before" curr */
485 if (act->happens_before(curr)) {
487 mo_graph->addEdge(act->get_reads_from(), curr);
489 mo_graph->addEdge(act, curr);
492 } else if (act->is_read() && !act->is_synchronizing(curr) &&
493 !act->same_thread(curr)) {
494 /* We have an action that:
495 (1) did not happen before us
496 (2) is a read and we are a write
497 (3) cannot synchronize with us
498 (4) is in a different thread
500 that read could potentially read from our write.
502 if (act->get_node()->add_future_value(curr->get_value()) &&
503 (!next_backtrack || *act > *next_backtrack))
504 next_backtrack = act;
513 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
514 * The ModelAction under consideration is expected to be taking part in
515 * release/acquire synchronization as an object of the "reads from" relation.
516 * Note that this can only provide release sequence support for RMW chains
517 * which do not read from the future, as those actions cannot be traced until
518 * their "promise" is fulfilled. Similarly, we may not even establish the
519 * presence of a release sequence with certainty, as some modification order
520 * constraints may be decided further in the future. Thus, this function
521 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
522 * and a boolean representing certainty.
524 * @todo Finish lazy updating, when promises are fulfilled in the future
525 * @param rf The action that might be part of a release sequence. Must be a
527 * @param release_heads A pass-by-reference style return parameter. After
528 * execution of this function, release_heads will contain the heads of all the
529 * relevant release sequences, if any exists
530 * @return true, if the ModelChecker is certain that release_heads is complete;
533 bool ModelChecker::release_seq_head(const ModelAction *rf,
534 std::vector<const ModelAction *> *release_heads) const
536 ASSERT(rf->is_write());
538 /* read from future: need to settle this later */
539 return false; /* incomplete */
541 if (rf->is_release())
542 release_heads->push_back(rf);
544 if (rf->is_acquire())
545 return true; /* complete */
546 return release_seq_head(rf->get_reads_from(), release_heads);
548 if (rf->is_release())
549 return true; /* complete */
551 /* else relaxed write; check modification order for contiguous subsequence
552 * -> rf must be same thread as release */
553 int tid = id_to_int(rf->get_tid());
554 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
555 action_list_t *list = &(*thrd_lists)[tid];
556 action_list_t::const_reverse_iterator rit;
558 /* Find rf in the thread list */
559 for (rit = list->rbegin(); rit != list->rend(); rit++)
563 /* Find the last write/release */
564 for (; rit != list->rend(); rit++)
565 if ((*rit)->is_release())
567 if (rit == list->rend()) {
568 /* No write-release in this thread */
569 return true; /* complete */
571 ModelAction *release = *rit;
573 ASSERT(rf->same_thread(release));
576 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
577 if (id_to_int(rf->get_tid()) == (int)i)
579 list = &(*thrd_lists)[i];
580 for (rit = list->rbegin(); rit != list->rend(); rit++) {
581 const ModelAction *act = *rit;
582 if (!act->is_write())
584 /* Reach synchronization -> this thread is complete */
585 if (act->happens_before(release))
587 if (rf->happens_before(act))
590 /* Check modification order */
591 if (mo_graph->checkReachable(rf, act))
594 if (mo_graph->checkReachable(act, release))
595 /* act --mo--> release */
597 if (mo_graph->checkReachable(release, act) &&
598 mo_graph->checkReachable(act, rf)) {
599 /* release --mo-> act --mo--> rf */
600 return true; /* complete */
607 release_heads->push_back(release);
612 * A public interface for getting the release sequence head(s) with which a
613 * given ModelAction must synchronize. This function only returns a non-empty
614 * result when it can locate a release sequence head with certainty. Otherwise,
615 * it may mark the internal state of the ModelChecker so that it will handle
616 * the release sequence at a later time, causing @a act to update its
617 * synchronization at some later point in execution.
618 * @param act The 'acquire' action that may read from a release sequence
619 * @param release_heads A pass-by-reference return parameter. Will be filled
620 * with the head(s) of the release sequence(s), if they exists with certainty.
621 * @see ModelChecker::release_seq_head
623 void ModelChecker::get_release_seq_heads(ModelAction *act,
624 std::vector<const ModelAction *> *release_heads)
626 const ModelAction *rf = act->get_reads_from();
628 complete = release_seq_head(rf, release_heads);
630 /* add act to 'lazy checking' list */
631 std::list<ModelAction *> *list;
632 list = lazy_sync_with_release->get_safe_ptr(act->get_location());
633 list->push_back(act);
638 * Attempt to resolve all stashed operations that might synchronize with a
639 * release sequence for a given location. This implements the "lazy" portion of
640 * determining whether or not a release sequence was contiguous, since not all
641 * modification order information is present at the time an action occurs.
643 * @param location The location/object that should be checked for release
644 * sequence resolutions
645 * @return True if any updates occurred (new synchronization, new mo_graph edges)
647 bool ModelChecker::resolve_release_sequences(void *location)
649 std::list<ModelAction *> *list;
650 list = lazy_sync_with_release->getptr(location);
654 bool updated = false;
655 std::list<ModelAction *>::iterator it = list->begin();
656 while (it != list->end()) {
657 ModelAction *act = *it;
658 const ModelAction *rf = act->get_reads_from();
659 std::vector<const ModelAction *> release_heads;
661 complete = release_seq_head(rf, &release_heads);
662 for (unsigned int i = 0; i < release_heads.size(); i++) {
663 if (!act->has_synchronized_with(release_heads[i])) {
665 act->synchronize_with(release_heads[i]);
670 /* propagate synchronization to later actions */
671 action_list_t::reverse_iterator it = action_trace->rbegin();
672 while ((*it) != act) {
673 ModelAction *propagate = *it;
674 if (act->happens_before(propagate))
675 /** @todo new mo_graph edges along with
676 * this synchronization? */
677 propagate->synchronize_with(act);
681 it = list->erase(it);
690 * Performs various bookkeeping operations for the current ModelAction. For
691 * instance, adds action to the per-object, per-thread action vector and to the
692 * action trace list of all thread actions.
694 * @param act is the ModelAction to add.
696 void ModelChecker::add_action_to_lists(ModelAction *act)
698 int tid = id_to_int(act->get_tid());
699 action_trace->push_back(act);
701 obj_map->get_safe_ptr(act->get_location())->push_back(act);
703 std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
704 if (tid >= (int)vec->size())
705 vec->resize(next_thread_id);
706 (*vec)[tid].push_back(act);
708 if ((int)thrd_last_action->size() <= tid)
709 thrd_last_action->resize(get_num_threads());
710 (*thrd_last_action)[tid] = act;
713 ModelAction * ModelChecker::get_last_action(thread_id_t tid)
715 int nthreads = get_num_threads();
716 if ((int)thrd_last_action->size() < nthreads)
717 thrd_last_action->resize(nthreads);
718 return (*thrd_last_action)[id_to_int(tid)];
722 * Gets the last memory_order_seq_cst action (in the total global sequence)
723 * performed on a particular object (i.e., memory location).
724 * @param location The object location to check
725 * @return The last seq_cst action performed
727 ModelAction * ModelChecker::get_last_seq_cst(const void *location)
729 action_list_t *list = obj_map->get_safe_ptr(location);
730 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
731 action_list_t::reverse_iterator rit;
732 for (rit = list->rbegin(); rit != list->rend(); rit++)
733 if ((*rit)->is_write() && (*rit)->is_seqcst())
738 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
740 ModelAction *parent = get_last_action(tid);
742 parent = get_thread(tid)->get_creation();
747 * Returns the clock vector for a given thread.
748 * @param tid The thread whose clock vector we want
749 * @return Desired clock vector
751 ClockVector * ModelChecker::get_cv(thread_id_t tid)
753 return get_parent_action(tid)->get_cv();
757 * Resolve a set of Promises with a current write. The set is provided in the
758 * Node corresponding to @a write.
759 * @param write The ModelAction that is fulfilling Promises
760 * @return True if promises were resolved; false otherwise
762 bool ModelChecker::resolve_promises(ModelAction *write)
764 bool resolved = false;
765 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
766 Promise *promise = (*promises)[promise_index];
767 if (write->get_node()->get_promise(i)) {
768 ModelAction *read = promise->get_action();
769 read->read_from(write);
770 r_modification_order(read, write);
771 post_r_modification_order(read, write);
772 promises->erase(promises->begin() + promise_index);
781 * Compute the set of promises that could potentially be satisfied by this
782 * action. Note that the set computation actually appears in the Node, not in
784 * @param curr The ModelAction that may satisfy promises
786 void ModelChecker::compute_promises(ModelAction *curr)
788 for (unsigned int i = 0; i < promises->size(); i++) {
789 Promise *promise = (*promises)[i];
790 const ModelAction *act = promise->get_action();
791 if (!act->happens_before(curr) &&
793 !act->is_synchronizing(curr) &&
794 !act->same_thread(curr) &&
795 promise->get_value() == curr->get_value()) {
796 curr->get_node()->set_promise(i);
801 /** Checks promises in response to change in ClockVector Threads. */
802 void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv)
804 for (unsigned int i = 0; i < promises->size(); i++) {
805 Promise *promise = (*promises)[i];
806 const ModelAction *act = promise->get_action();
807 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
808 merge_cv->synchronized_since(act)) {
809 //This thread is no longer able to send values back to satisfy the promise
810 int num_synchronized_threads = promise->increment_threads();
811 if (num_synchronized_threads == model->get_num_threads()) {
813 failed_promise = true;
821 * Build up an initial set of all past writes that this 'read' action may read
822 * from. This set is determined by the clock vector's "happens before"
824 * @param curr is the current ModelAction that we are exploring; it must be a
827 void ModelChecker::build_reads_from_past(ModelAction *curr)
829 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
831 ASSERT(curr->is_read());
833 ModelAction *last_seq_cst = NULL;
835 /* Track whether this object has been initialized */
836 bool initialized = false;
838 if (curr->is_seqcst()) {
839 last_seq_cst = get_last_seq_cst(curr->get_location());
840 /* We have to at least see the last sequentially consistent write,
841 so we are initialized. */
842 if (last_seq_cst != NULL)
846 /* Iterate over all threads */
847 for (i = 0; i < thrd_lists->size(); i++) {
848 /* Iterate over actions in thread, starting from most recent */
849 action_list_t *list = &(*thrd_lists)[i];
850 action_list_t::reverse_iterator rit;
851 for (rit = list->rbegin(); rit != list->rend(); rit++) {
852 ModelAction *act = *rit;
854 /* Only consider 'write' actions */
855 if (!act->is_write())
858 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
859 if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
860 DEBUG("Adding action to may_read_from:\n");
865 curr->get_node()->add_read_from(act);
868 /* Include at most one act per-thread that "happens before" curr */
869 if (act->happens_before(curr)) {
877 /** @todo Need a more informative way of reporting errors. */
878 printf("ERROR: may read from uninitialized atomic\n");
881 if (DBG_ENABLED() || !initialized) {
882 printf("Reached read action:\n");
884 printf("Printing may_read_from\n");
885 curr->get_node()->print_may_read_from();
886 printf("End printing may_read_from\n");
892 static void print_list(action_list_t *list)
894 action_list_t::iterator it;
896 printf("---------------------------------------------------------------------\n");
899 for (it = list->begin(); it != list->end(); it++) {
902 printf("---------------------------------------------------------------------\n");
905 void ModelChecker::print_summary()
908 printf("Number of executions: %d\n", num_executions);
909 printf("Total nodes created: %d\n", node_stack->get_total_nodes());
913 if (!isfinalfeasible())
914 printf("INFEASIBLE EXECUTION!\n");
915 print_list(action_trace);
920 * Add a Thread to the system for the first time. Should only be called once
922 * @param t The Thread to add
924 void ModelChecker::add_thread(Thread *t)
926 thread_map->put(id_to_int(t->get_id()), t);
927 scheduler->add_thread(t);
930 void ModelChecker::remove_thread(Thread *t)
932 scheduler->remove_thread(t);
936 * Switch from a user-context to the "master thread" context (a.k.a. system
937 * context). This switch is made with the intention of exploring a particular
938 * model-checking action (described by a ModelAction object). Must be called
939 * from a user-thread context.
940 * @param act The current action that will be explored. May be NULL, although
941 * there is little reason to switch to the model-checker without an action to
942 * explore (note: act == NULL is sometimes used as a hack to allow a thread to
943 * yield control without performing any progress; see thrd_join()).
944 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
946 int ModelChecker::switch_to_master(ModelAction *act)
949 Thread *old = thread_current();
950 set_current_action(act);
951 old->set_state(THREAD_READY);
952 return Thread::swap(old, &system_context);
956 * Takes the next step in the execution, if possible.
957 * @return Returns true (success) if a step was taken and false otherwise.
959 bool ModelChecker::take_step() {
962 curr = thread_current();
964 if (curr->get_state() == THREAD_READY) {
965 check_current_action();
966 scheduler->add_thread(curr);
967 } else if (curr->get_state() == THREAD_RUNNING) {
968 /* Stopped while running; i.e., completed */
974 next = scheduler->next_thread(nextThread);
976 /* Infeasible -> don't take any more steps */
981 next->set_state(THREAD_RUNNING);
982 DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
984 /* next == NULL -> don't take any more steps */
987 /* Return false only if swap fails with an error */
988 return (Thread::swap(&system_context, next) == 0);
991 /** Runs the current execution until threre are no more steps to take. */
992 void ModelChecker::finish_execution() {