7 #include "snapshot-interface.h"
9 #include "clockvector.h"
10 #include "cyclegraph.h"
14 #define INITIAL_THREAD_ID 0
18 /** @brief Constructor */
19 ModelChecker::ModelChecker(struct model_params params) :
20 /* Initialize default scheduler */
21 scheduler(new Scheduler()),
22 /* First thread created will have id INITIAL_THREAD_ID */
23 next_thread_id(INITIAL_THREAD_ID),
24 used_sequence_numbers(0),
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 obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
34 promises(new std::vector<Promise *>()),
35 lazy_sync_with_release(new HashTable<void *, std::list<ModelAction *>, uintptr_t, 4>()),
36 thrd_last_action(new std::vector<ModelAction *>(1)),
37 node_stack(new NodeStack()),
39 mo_graph(new CycleGraph()),
40 failed_promise(false),
45 /** @brief Destructor */
46 ModelChecker::~ModelChecker()
48 for (int i = 0; i < get_num_threads(); i++)
49 delete thread_map->get(i);
56 for (unsigned int i = 0; i < promises->size(); i++)
57 delete (*promises)[i];
60 delete lazy_sync_with_release;
62 delete thrd_last_action;
69 * Restores user program to initial state and resets all model-checker data
72 void ModelChecker::reset_to_initial_state()
74 DEBUG("+++ Resetting to initial state +++\n");
75 node_stack->reset_execution();
76 current_action = NULL;
77 next_thread_id = INITIAL_THREAD_ID;
78 used_sequence_numbers = 0;
80 next_backtrack = NULL;
81 failed_promise = false;
83 snapshotObject->backTrackBeforeStep(0);
86 /** @returns a thread ID for a new Thread */
87 thread_id_t ModelChecker::get_next_id()
89 return next_thread_id++;
92 /** @returns the number of user threads created during this execution */
93 int ModelChecker::get_num_threads()
95 return next_thread_id;
98 /** @returns a sequence number for a new ModelAction */
99 modelclock_t ModelChecker::get_next_seq_num()
101 return ++used_sequence_numbers;
105 * Choose the next thread in the replay sequence.
107 * If the replay sequence has reached the 'diverge' point, returns a thread
108 * from the backtracking set. Otherwise, simply returns the next thread in the
109 * sequence that is being replayed.
111 Thread * ModelChecker::get_next_replay_thread()
115 /* Have we completed exploring the preselected path? */
119 /* Else, we are trying to replay an execution */
120 ModelAction *next = node_stack->get_next()->get_action();
122 if (next == diverge) {
123 Node *nextnode = next->get_node();
124 /* Reached divergence point */
125 if (nextnode->increment_promise()) {
126 /* The next node will try to satisfy a different set of promises. */
127 tid = next->get_tid();
128 node_stack->pop_restofstack(2);
129 } else if (nextnode->increment_read_from()) {
130 /* The next node will read from a different value. */
131 tid = next->get_tid();
132 node_stack->pop_restofstack(2);
133 } else if (nextnode->increment_future_value()) {
134 /* The next node will try to read from a different future value. */
135 tid = next->get_tid();
136 node_stack->pop_restofstack(2);
138 /* Make a different thread execute for next step */
139 Node *node = nextnode->get_parent();
140 tid = node->get_next_backtrack();
141 node_stack->pop_restofstack(1);
143 DEBUG("*** Divergence point ***\n");
146 tid = next->get_tid();
148 DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
149 ASSERT(tid != THREAD_ID_T_NONE);
150 return thread_map->get(id_to_int(tid));
154 * Queries the model-checker for more executions to explore and, if one
155 * exists, resets the model-checker state to execute a new execution.
157 * @return If there are more executions to explore, return true. Otherwise,
160 bool ModelChecker::next_execution()
166 if (isfinalfeasible() || DBG_ENABLED())
169 if ((diverge = get_next_backtrack()) == NULL)
173 printf("Next execution will diverge at:\n");
177 reset_to_initial_state();
181 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
183 action_type type = act->get_type();
193 /* linear search: from most recent to oldest */
194 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
195 action_list_t::reverse_iterator rit;
196 for (rit = list->rbegin(); rit != list->rend(); rit++) {
197 ModelAction *prev = *rit;
198 if (act->is_synchronizing(prev))
204 void ModelChecker::set_backtracking(ModelAction *act)
208 Thread *t = get_thread(act->get_tid());
210 prev = get_last_conflict(act);
214 node = prev->get_node()->get_parent();
216 while (!node->is_enabled(t))
219 /* Check if this has been explored already */
220 if (node->has_been_explored(t->get_id()))
223 /* Cache the latest backtracking point */
224 if (!next_backtrack || *prev > *next_backtrack)
225 next_backtrack = prev;
227 /* If this is a new backtracking point, mark the tree */
228 if (!node->set_backtrack(t->get_id()))
230 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
231 prev->get_tid(), t->get_id());
239 * Returns last backtracking point. The model checker will explore a different
240 * path for this point in the next execution.
241 * @return The ModelAction at which the next execution should diverge.
243 ModelAction * ModelChecker::get_next_backtrack()
245 ModelAction *next = next_backtrack;
246 next_backtrack = NULL;
251 * This is the heart of the model checker routine. It performs model-checking
252 * actions corresponding to a given "current action." Among other processes, it
253 * calculates reads-from relationships, updates synchronization clock vectors,
254 * forms a memory_order constraints graph, and handles replay/backtrack
255 * execution when running permutations of previously-observed executions.
257 * @param curr The current action to process
258 * @return The next Thread that must be executed. May be NULL if ModelChecker
259 * makes no choice (e.g., according to replay execution, combining RMW actions,
262 Thread * ModelChecker::check_current_action(ModelAction *curr)
264 bool already_added = false;
268 if (curr->is_rmwc() || curr->is_rmw()) {
269 ModelAction *tmp = process_rmw(curr);
270 already_added = true;
274 ModelAction *tmp = node_stack->explore_action(curr);
276 /* Discard duplicate ModelAction; use action from NodeStack */
277 /* First restore type and order in case of RMW operation */
279 tmp->copy_typeandorder(curr);
281 /* If we have diverged, we need to reset the clock vector. */
283 tmp->create_cv(get_parent_action(tmp->get_tid()));
289 * Perform one-time actions when pushing new ModelAction onto
292 curr->create_cv(get_parent_action(curr->get_tid()));
293 /* Build may_read_from set */
295 build_reads_from_past(curr);
296 if (curr->is_write())
297 compute_promises(curr);
301 /* Assign 'creation' parent */
302 if (curr->get_type() == THREAD_CREATE) {
303 Thread *th = (Thread *)curr->get_location();
304 th->set_creation(curr);
305 } else if (curr->get_type() == THREAD_JOIN) {
307 wait = get_thread(curr->get_tid());
308 join = (Thread *)curr->get_location();
309 if (!join->is_complete())
310 scheduler->wait(wait, join);
311 } else if (curr->get_type() == THREAD_FINISH) {
312 Thread *th = get_thread(curr->get_tid());
313 while (!th->wait_list_empty()) {
314 Thread *wake = th->pop_wait_list();
315 scheduler->wake(wake);
320 /* Deal with new thread */
321 if (curr->get_type() == THREAD_START)
322 check_promises(NULL, curr->get_cv());
324 /* Assign reads_from values */
325 Thread *th = get_thread(curr->get_tid());
326 uint64_t value = VALUE_NONE;
327 bool updated = false;
328 if (curr->is_read()) {
329 const ModelAction *reads_from = curr->get_node()->get_read_from();
330 if (reads_from != NULL) {
331 value = reads_from->get_value();
332 /* Assign reads_from, perform release/acquire synchronization */
333 curr->read_from(reads_from);
334 if (r_modification_order(curr,reads_from))
337 /* Read from future value */
338 value = curr->get_node()->get_future_value();
339 curr->read_from(NULL);
340 Promise *valuepromise = new Promise(curr, value);
341 promises->push_back(valuepromise);
343 } else if (curr->is_write()) {
344 if (w_modification_order(curr))
346 if (resolve_promises(curr))
351 resolve_release_sequences(curr->get_location());
353 th->set_return_value(value);
355 /* Add action to list. */
357 add_action_to_lists(curr);
359 Node *currnode = curr->get_node();
360 Node *parnode = currnode->get_parent();
362 if (!parnode->backtrack_empty() || !currnode->read_from_empty() ||
363 !currnode->future_value_empty() || !currnode->promise_empty())
364 if (!next_backtrack || *curr > *next_backtrack)
365 next_backtrack = curr;
367 set_backtracking(curr);
369 /* Do not split atomic actions. */
371 return thread_current();
373 return get_next_replay_thread();
376 /** @returns whether the current partial trace must be a prefix of a
379 bool ModelChecker::isfeasibleprefix() {
380 return promises->size()==0;
383 /** @returns whether the current partial trace is feasible. */
384 bool ModelChecker::isfeasible() {
385 return !mo_graph->checkForCycles() && !failed_promise;
388 /** Returns whether the current completed trace is feasible. */
389 bool ModelChecker::isfinalfeasible() {
390 return isfeasible() && promises->size() == 0;
393 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
394 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
395 int tid = id_to_int(act->get_tid());
396 ModelAction *lastread = get_last_action(tid);
397 lastread->process_rmw(act);
399 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
404 * Updates the mo_graph with the constraints imposed from the current read.
405 * @param curr The current action. Must be a read.
406 * @param rf The action that curr reads from. Must be a write.
407 * @return True if modification order edges were added; false otherwise
409 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
411 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
414 ASSERT(curr->is_read());
416 /* Iterate over all threads */
417 for (i = 0; i < thrd_lists->size(); i++) {
418 /* Iterate over actions in thread, starting from most recent */
419 action_list_t *list = &(*thrd_lists)[i];
420 action_list_t::reverse_iterator rit;
421 for (rit = list->rbegin(); rit != list->rend(); rit++) {
422 ModelAction *act = *rit;
424 /* Include at most one act per-thread that "happens before" curr */
425 if (act->happens_before(curr)) {
426 if (act->is_read()) {
427 const ModelAction *prevreadfrom = act->get_reads_from();
428 if (prevreadfrom != NULL && rf != prevreadfrom) {
429 mo_graph->addEdge(prevreadfrom, rf);
432 } else if (rf != act) {
433 mo_graph->addEdge(act, rf);
444 /** Updates the mo_graph with the constraints imposed from the current read. */
445 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
447 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
449 ASSERT(curr->is_read());
451 /* Iterate over all threads */
452 for (i = 0; i < thrd_lists->size(); i++) {
453 /* Iterate over actions in thread, starting from most recent */
454 action_list_t *list = &(*thrd_lists)[i];
455 action_list_t::reverse_iterator rit;
456 ModelAction *lastact = NULL;
458 /* Find last action that happens after curr */
459 for (rit = list->rbegin(); rit != list->rend(); rit++) {
460 ModelAction *act = *rit;
461 if (curr->happens_before(act)) {
467 /* Include at most one act per-thread that "happens before" curr */
468 if (lastact != NULL) {
469 if (lastact->is_read()) {
470 const ModelAction *postreadfrom = lastact->get_reads_from();
471 if (postreadfrom != NULL&&rf != postreadfrom)
472 mo_graph->addEdge(rf, postreadfrom);
473 } else if (rf != lastact) {
474 mo_graph->addEdge(rf, lastact);
482 * Updates the mo_graph with the constraints imposed from the current write.
483 * @param curr The current action. Must be a write.
484 * @return True if modification order edges were added; false otherwise
486 bool ModelChecker::w_modification_order(ModelAction *curr)
488 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
491 ASSERT(curr->is_write());
493 if (curr->is_seqcst()) {
494 /* We have to at least see the last sequentially consistent write,
495 so we are initialized. */
496 ModelAction *last_seq_cst = get_last_seq_cst(curr->get_location());
497 if (last_seq_cst != NULL) {
498 mo_graph->addEdge(last_seq_cst, curr);
503 /* Iterate over all threads */
504 for (i = 0; i < thrd_lists->size(); i++) {
505 /* Iterate over actions in thread, starting from most recent */
506 action_list_t *list = &(*thrd_lists)[i];
507 action_list_t::reverse_iterator rit;
508 for (rit = list->rbegin(); rit != list->rend(); rit++) {
509 ModelAction *act = *rit;
511 /* Include at most one act per-thread that "happens before" curr */
512 if (act->happens_before(curr)) {
514 mo_graph->addEdge(act->get_reads_from(), curr);
516 mo_graph->addEdge(act, curr);
519 } else if (act->is_read() && !act->is_synchronizing(curr) &&
520 !act->same_thread(curr)) {
521 /* We have an action that:
522 (1) did not happen before us
523 (2) is a read and we are a write
524 (3) cannot synchronize with us
525 (4) is in a different thread
527 that read could potentially read from our write.
529 if (act->get_node()->add_future_value(curr->get_value()) &&
530 (!next_backtrack || *act > *next_backtrack))
531 next_backtrack = act;
540 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
541 * The ModelAction under consideration is expected to be taking part in
542 * release/acquire synchronization as an object of the "reads from" relation.
543 * Note that this can only provide release sequence support for RMW chains
544 * which do not read from the future, as those actions cannot be traced until
545 * their "promise" is fulfilled. Similarly, we may not even establish the
546 * presence of a release sequence with certainty, as some modification order
547 * constraints may be decided further in the future. Thus, this function
548 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
549 * and a boolean representing certainty.
551 * @todo Finish lazy updating, when promises are fulfilled in the future
552 * @param rf The action that might be part of a release sequence. Must be a
554 * @param release_heads A pass-by-reference style return parameter. After
555 * execution of this function, release_heads will contain the heads of all the
556 * relevant release sequences, if any exists
557 * @return true, if the ModelChecker is certain that release_heads is complete;
560 bool ModelChecker::release_seq_head(const ModelAction *rf,
561 std::vector<const ModelAction *> *release_heads) const
563 ASSERT(rf->is_write());
565 /* read from future: need to settle this later */
566 return false; /* incomplete */
568 if (rf->is_release())
569 release_heads->push_back(rf);
571 if (rf->is_acquire())
572 return true; /* complete */
573 return release_seq_head(rf->get_reads_from(), release_heads);
575 if (rf->is_release())
576 return true; /* complete */
578 /* else relaxed write; check modification order for contiguous subsequence
579 * -> rf must be same thread as release */
580 int tid = id_to_int(rf->get_tid());
581 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
582 action_list_t *list = &(*thrd_lists)[tid];
583 action_list_t::const_reverse_iterator rit;
585 /* Find rf in the thread list */
586 for (rit = list->rbegin(); rit != list->rend(); rit++)
590 /* Find the last write/release */
591 for (; rit != list->rend(); rit++)
592 if ((*rit)->is_release())
594 if (rit == list->rend()) {
595 /* No write-release in this thread */
596 return true; /* complete */
598 ModelAction *release = *rit;
600 ASSERT(rf->same_thread(release));
603 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
604 if (id_to_int(rf->get_tid()) == (int)i)
606 list = &(*thrd_lists)[i];
607 for (rit = list->rbegin(); rit != list->rend(); rit++) {
608 const ModelAction *act = *rit;
609 if (!act->is_write())
611 /* Reach synchronization -> this thread is complete */
612 if (act->happens_before(release))
614 if (rf->happens_before(act))
617 /* Check modification order */
618 if (mo_graph->checkReachable(rf, act))
621 if (mo_graph->checkReachable(act, release))
622 /* act --mo--> release */
624 if (mo_graph->checkReachable(release, act) &&
625 mo_graph->checkReachable(act, rf)) {
626 /* release --mo-> act --mo--> rf */
627 return true; /* complete */
634 release_heads->push_back(release);
639 * A public interface for getting the release sequence head(s) with which a
640 * given ModelAction must synchronize. This function only returns a non-empty
641 * result when it can locate a release sequence head with certainty. Otherwise,
642 * it may mark the internal state of the ModelChecker so that it will handle
643 * the release sequence at a later time, causing @a act to update its
644 * synchronization at some later point in execution.
645 * @param act The 'acquire' action that may read from a release sequence
646 * @param release_heads A pass-by-reference return parameter. Will be filled
647 * with the head(s) of the release sequence(s), if they exists with certainty.
648 * @see ModelChecker::release_seq_head
650 void ModelChecker::get_release_seq_heads(ModelAction *act,
651 std::vector<const ModelAction *> *release_heads)
653 const ModelAction *rf = act->get_reads_from();
655 complete = release_seq_head(rf, release_heads);
657 /* add act to 'lazy checking' list */
658 std::list<ModelAction *> *list;
659 list = lazy_sync_with_release->get_safe_ptr(act->get_location());
660 list->push_back(act);
665 * Attempt to resolve all stashed operations that might synchronize with a
666 * release sequence for a given location. This implements the "lazy" portion of
667 * determining whether or not a release sequence was contiguous, since not all
668 * modification order information is present at the time an action occurs.
670 * @param location The location/object that should be checked for release
671 * sequence resolutions
672 * @return True if any updates occurred (new synchronization, new mo_graph edges)
674 bool ModelChecker::resolve_release_sequences(void *location)
676 std::list<ModelAction *> *list;
677 list = lazy_sync_with_release->getptr(location);
681 bool updated = false;
682 std::list<ModelAction *>::iterator it = list->begin();
683 while (it != list->end()) {
684 ModelAction *act = *it;
685 const ModelAction *rf = act->get_reads_from();
686 std::vector<const ModelAction *> release_heads;
688 complete = release_seq_head(rf, &release_heads);
689 for (unsigned int i = 0; i < release_heads.size(); i++) {
690 if (!act->has_synchronized_with(release_heads[i])) {
692 act->synchronize_with(release_heads[i]);
697 /* propagate synchronization to later actions */
698 action_list_t::reverse_iterator it = action_trace->rbegin();
699 while ((*it) != act) {
700 ModelAction *propagate = *it;
701 if (act->happens_before(propagate))
702 /** @todo new mo_graph edges along with
703 * this synchronization? */
704 propagate->synchronize_with(act);
708 it = list->erase(it);
713 // If we resolved promises or data races, see if we have realized a data race.
714 if (checkDataRaces()) {
722 * Performs various bookkeeping operations for the current ModelAction. For
723 * instance, adds action to the per-object, per-thread action vector and to the
724 * action trace list of all thread actions.
726 * @param act is the ModelAction to add.
728 void ModelChecker::add_action_to_lists(ModelAction *act)
730 int tid = id_to_int(act->get_tid());
731 action_trace->push_back(act);
733 obj_map->get_safe_ptr(act->get_location())->push_back(act);
735 std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
736 if (tid >= (int)vec->size())
737 vec->resize(next_thread_id);
738 (*vec)[tid].push_back(act);
740 if ((int)thrd_last_action->size() <= tid)
741 thrd_last_action->resize(get_num_threads());
742 (*thrd_last_action)[tid] = act;
745 ModelAction * ModelChecker::get_last_action(thread_id_t tid)
747 int nthreads = get_num_threads();
748 if ((int)thrd_last_action->size() < nthreads)
749 thrd_last_action->resize(nthreads);
750 return (*thrd_last_action)[id_to_int(tid)];
754 * Gets the last memory_order_seq_cst action (in the total global sequence)
755 * performed on a particular object (i.e., memory location).
756 * @param location The object location to check
757 * @return The last seq_cst action performed
759 ModelAction * ModelChecker::get_last_seq_cst(const void *location)
761 action_list_t *list = obj_map->get_safe_ptr(location);
762 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
763 action_list_t::reverse_iterator rit;
764 for (rit = list->rbegin(); rit != list->rend(); rit++)
765 if ((*rit)->is_write() && (*rit)->is_seqcst())
770 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
772 ModelAction *parent = get_last_action(tid);
774 parent = get_thread(tid)->get_creation();
779 * Returns the clock vector for a given thread.
780 * @param tid The thread whose clock vector we want
781 * @return Desired clock vector
783 ClockVector * ModelChecker::get_cv(thread_id_t tid)
785 return get_parent_action(tid)->get_cv();
789 * Resolve a set of Promises with a current write. The set is provided in the
790 * Node corresponding to @a write.
791 * @param write The ModelAction that is fulfilling Promises
792 * @return True if promises were resolved; false otherwise
794 bool ModelChecker::resolve_promises(ModelAction *write)
796 bool resolved = false;
797 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
798 Promise *promise = (*promises)[promise_index];
799 if (write->get_node()->get_promise(i)) {
800 ModelAction *read = promise->get_action();
801 read->read_from(write);
802 r_modification_order(read, write);
803 post_r_modification_order(read, write);
804 promises->erase(promises->begin() + promise_index);
814 * Compute the set of promises that could potentially be satisfied by this
815 * action. Note that the set computation actually appears in the Node, not in
817 * @param curr The ModelAction that may satisfy promises
819 void ModelChecker::compute_promises(ModelAction *curr)
821 for (unsigned int i = 0; i < promises->size(); i++) {
822 Promise *promise = (*promises)[i];
823 const ModelAction *act = promise->get_action();
824 if (!act->happens_before(curr) &&
826 !act->is_synchronizing(curr) &&
827 !act->same_thread(curr) &&
828 promise->get_value() == curr->get_value()) {
829 curr->get_node()->set_promise(i);
834 /** Checks promises in response to change in ClockVector Threads. */
835 void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv)
837 for (unsigned int i = 0; i < promises->size(); i++) {
838 Promise *promise = (*promises)[i];
839 const ModelAction *act = promise->get_action();
840 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
841 merge_cv->synchronized_since(act)) {
842 //This thread is no longer able to send values back to satisfy the promise
843 int num_synchronized_threads = promise->increment_threads();
844 if (num_synchronized_threads == get_num_threads()) {
846 failed_promise = true;
854 * Build up an initial set of all past writes that this 'read' action may read
855 * from. This set is determined by the clock vector's "happens before"
857 * @param curr is the current ModelAction that we are exploring; it must be a
860 void ModelChecker::build_reads_from_past(ModelAction *curr)
862 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
864 ASSERT(curr->is_read());
866 ModelAction *last_seq_cst = NULL;
868 /* Track whether this object has been initialized */
869 bool initialized = false;
871 if (curr->is_seqcst()) {
872 last_seq_cst = get_last_seq_cst(curr->get_location());
873 /* We have to at least see the last sequentially consistent write,
874 so we are initialized. */
875 if (last_seq_cst != NULL)
879 /* Iterate over all threads */
880 for (i = 0; i < thrd_lists->size(); i++) {
881 /* Iterate over actions in thread, starting from most recent */
882 action_list_t *list = &(*thrd_lists)[i];
883 action_list_t::reverse_iterator rit;
884 for (rit = list->rbegin(); rit != list->rend(); rit++) {
885 ModelAction *act = *rit;
887 /* Only consider 'write' actions */
888 if (!act->is_write())
891 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
892 if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
893 DEBUG("Adding action to may_read_from:\n");
898 curr->get_node()->add_read_from(act);
901 /* Include at most one act per-thread that "happens before" curr */
902 if (act->happens_before(curr)) {
910 /** @todo Need a more informative way of reporting errors. */
911 printf("ERROR: may read from uninitialized atomic\n");
914 if (DBG_ENABLED() || !initialized) {
915 printf("Reached read action:\n");
917 printf("Printing may_read_from\n");
918 curr->get_node()->print_may_read_from();
919 printf("End printing may_read_from\n");
925 static void print_list(action_list_t *list)
927 action_list_t::iterator it;
929 printf("---------------------------------------------------------------------\n");
932 for (it = list->begin(); it != list->end(); it++) {
935 printf("---------------------------------------------------------------------\n");
938 void ModelChecker::print_summary()
941 printf("Number of executions: %d\n", num_executions);
942 printf("Total nodes created: %d\n", node_stack->get_total_nodes());
946 if (!isfinalfeasible())
947 printf("INFEASIBLE EXECUTION!\n");
948 print_list(action_trace);
953 * Add a Thread to the system for the first time. Should only be called once
955 * @param t The Thread to add
957 void ModelChecker::add_thread(Thread *t)
959 thread_map->put(id_to_int(t->get_id()), t);
960 scheduler->add_thread(t);
963 void ModelChecker::remove_thread(Thread *t)
965 scheduler->remove_thread(t);
969 * Switch from a user-context to the "master thread" context (a.k.a. system
970 * context). This switch is made with the intention of exploring a particular
971 * model-checking action (described by a ModelAction object). Must be called
972 * from a user-thread context.
973 * @param act The current action that will be explored. Must not be NULL.
974 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
976 int ModelChecker::switch_to_master(ModelAction *act)
979 Thread *old = thread_current();
980 set_current_action(act);
981 old->set_state(THREAD_READY);
982 return Thread::swap(old, &system_context);
986 * Takes the next step in the execution, if possible.
987 * @return Returns true (success) if a step was taken and false otherwise.
989 bool ModelChecker::take_step() {
995 curr = thread_current();
997 if (curr->get_state() == THREAD_READY) {
998 ASSERT(current_action);
999 nextThread = check_current_action(current_action);
1000 current_action = NULL;
1001 if (!curr->is_blocked() && !curr->is_complete())
1002 scheduler->add_thread(curr);
1007 next = scheduler->next_thread(nextThread);
1009 /* Infeasible -> don't take any more steps */
1014 next->set_state(THREAD_RUNNING);
1015 DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
1017 /* next == NULL -> don't take any more steps */
1020 /* Return false only if swap fails with an error */
1021 return (Thread::swap(&system_context, next) == 0);
1024 /** Runs the current execution until threre are no more steps to take. */
1025 void ModelChecker::finish_execution() {
1028 while (take_step());