8 #include "snapshot-interface.h"
10 #include "clockvector.h"
11 #include "cyclegraph.h"
15 #define INITIAL_THREAD_ID 0
19 /** @brief Constructor */
20 ModelChecker::ModelChecker(struct model_params params) :
21 /* Initialize default scheduler */
22 scheduler(new Scheduler()),
26 action_trace(new action_list_t()),
27 thread_map(new HashTable<int, Thread *, int>()),
28 obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
29 obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
30 promises(new std::vector<Promise *>()),
31 lazy_sync_with_release(new HashTable<void *, std::list<ModelAction *>, uintptr_t, 4>()),
32 thrd_last_action(new std::vector<ModelAction *>(1)),
33 node_stack(new NodeStack()),
34 mo_graph(new CycleGraph()),
35 failed_promise(false),
36 too_many_reads(false),
39 /* Allocate this "size" on the snapshotting heap */
40 priv = (struct model_snapshot_members *)calloc(1, sizeof(*priv));
41 /* First thread created will have id INITIAL_THREAD_ID */
42 priv->next_thread_id = INITIAL_THREAD_ID;
44 lazy_sync_size = &priv->lazy_sync_size;
47 /** @brief Destructor */
48 ModelChecker::~ModelChecker()
50 for (int i = 0; i < get_num_threads(); i++)
51 delete thread_map->get(i);
58 for (unsigned int i = 0; i < promises->size(); i++)
59 delete (*promises)[i];
62 delete lazy_sync_with_release;
64 delete thrd_last_action;
71 * Restores user program to initial state and resets all model-checker data
74 void ModelChecker::reset_to_initial_state()
76 DEBUG("+++ Resetting to initial state +++\n");
77 node_stack->reset_execution();
78 failed_promise = false;
79 too_many_reads = false;
81 snapshotObject->backTrackBeforeStep(0);
84 /** @returns a thread ID for a new Thread */
85 thread_id_t ModelChecker::get_next_id()
87 return priv->next_thread_id++;
90 /** @returns the number of user threads created during this execution */
91 int ModelChecker::get_num_threads()
93 return priv->next_thread_id;
96 /** @returns a sequence number for a new ModelAction */
97 modelclock_t ModelChecker::get_next_seq_num()
99 return ++priv->used_sequence_numbers;
103 * Choose the next thread in the replay sequence.
105 * If the replay sequence has reached the 'diverge' point, returns a thread
106 * from the backtracking set. Otherwise, simply returns the next thread in the
107 * sequence that is being replayed.
109 Thread * ModelChecker::get_next_replay_thread()
113 /* Have we completed exploring the preselected path? */
117 /* Else, we are trying to replay an execution */
118 ModelAction *next = node_stack->get_next()->get_action();
120 if (next == diverge) {
121 Node *nextnode = next->get_node();
122 /* Reached divergence point */
123 if (nextnode->increment_promise()) {
124 /* The next node will try to satisfy a different set of promises. */
125 tid = next->get_tid();
126 node_stack->pop_restofstack(2);
127 } else if (nextnode->increment_read_from()) {
128 /* The next node will read from a different value. */
129 tid = next->get_tid();
130 node_stack->pop_restofstack(2);
131 } else if (nextnode->increment_future_value()) {
132 /* The next node will try to read from a different future value. */
133 tid = next->get_tid();
134 node_stack->pop_restofstack(2);
136 /* Make a different thread execute for next step */
137 Node *node = nextnode->get_parent();
138 tid = node->get_next_backtrack();
139 node_stack->pop_restofstack(1);
141 DEBUG("*** Divergence point ***\n");
144 tid = next->get_tid();
146 DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
147 ASSERT(tid != THREAD_ID_T_NONE);
148 return thread_map->get(id_to_int(tid));
152 * Queries the model-checker for more executions to explore and, if one
153 * exists, resets the model-checker state to execute a new execution.
155 * @return If there are more executions to explore, return true. Otherwise,
158 bool ModelChecker::next_execution()
164 if (isfinalfeasible() || DBG_ENABLED())
167 if ((diverge = get_next_backtrack()) == NULL)
171 printf("Next execution will diverge at:\n");
175 reset_to_initial_state();
179 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
181 action_type type = act->get_type();
191 /* linear search: from most recent to oldest */
192 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
193 action_list_t::reverse_iterator rit;
194 for (rit = list->rbegin(); rit != list->rend(); rit++) {
195 ModelAction *prev = *rit;
196 if (act->is_synchronizing(prev))
202 void ModelChecker::set_backtracking(ModelAction *act)
206 Thread *t = get_thread(act->get_tid());
208 prev = get_last_conflict(act);
212 node = prev->get_node()->get_parent();
214 while (!node->is_enabled(t))
217 /* Check if this has been explored already */
218 if (node->has_been_explored(t->get_id()))
221 /* Cache the latest backtracking point */
222 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
223 priv->next_backtrack = prev;
225 /* If this is a new backtracking point, mark the tree */
226 if (!node->set_backtrack(t->get_id()))
228 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
229 prev->get_tid(), t->get_id());
237 * Returns last backtracking point. The model checker will explore a different
238 * path for this point in the next execution.
239 * @return The ModelAction at which the next execution should diverge.
241 ModelAction * ModelChecker::get_next_backtrack()
243 ModelAction *next = priv->next_backtrack;
244 priv->next_backtrack = NULL;
249 * This is the heart of the model checker routine. It performs model-checking
250 * actions corresponding to a given "current action." Among other processes, it
251 * calculates reads-from relationships, updates synchronization clock vectors,
252 * forms a memory_order constraints graph, and handles replay/backtrack
253 * execution when running permutations of previously-observed executions.
255 * @param curr The current action to process
256 * @return The next Thread that must be executed. May be NULL if ModelChecker
257 * makes no choice (e.g., according to replay execution, combining RMW actions,
260 Thread * ModelChecker::check_current_action(ModelAction *curr)
262 bool already_added = false;
266 if (curr->is_rmwc() || curr->is_rmw()) {
267 ModelAction *tmp = process_rmw(curr);
268 already_added = true;
272 ModelAction *tmp = node_stack->explore_action(curr);
274 /* Discard duplicate ModelAction; use action from NodeStack */
275 /* First restore type and order in case of RMW operation */
277 tmp->copy_typeandorder(curr);
279 /* If we have diverged, we need to reset the clock vector. */
281 tmp->create_cv(get_parent_action(tmp->get_tid()));
287 * Perform one-time actions when pushing new ModelAction onto
290 curr->create_cv(get_parent_action(curr->get_tid()));
291 /* Build may_read_from set */
293 build_reads_from_past(curr);
294 if (curr->is_write())
295 compute_promises(curr);
299 /* Assign 'creation' parent */
300 if (curr->get_type() == THREAD_CREATE) {
301 Thread *th = (Thread *)curr->get_location();
302 th->set_creation(curr);
303 } else if (curr->get_type() == THREAD_JOIN) {
305 wait = get_thread(curr->get_tid());
306 join = (Thread *)curr->get_location();
307 if (!join->is_complete())
308 scheduler->wait(wait, join);
309 } else if (curr->get_type() == THREAD_FINISH) {
310 Thread *th = get_thread(curr->get_tid());
311 while (!th->wait_list_empty()) {
312 Thread *wake = th->pop_wait_list();
313 scheduler->wake(wake);
318 /* Deal with new thread */
319 if (curr->get_type() == THREAD_START)
320 check_promises(NULL, curr->get_cv());
322 /* Assign reads_from values */
323 Thread *th = get_thread(curr->get_tid());
324 uint64_t value = VALUE_NONE;
325 bool updated = false;
326 if (curr->is_read()) {
327 const ModelAction *reads_from = curr->get_node()->get_read_from();
328 if (reads_from != NULL) {
329 value = reads_from->get_value();
330 /* Assign reads_from, perform release/acquire synchronization */
331 curr->read_from(reads_from);
332 if (r_modification_order(curr,reads_from))
335 /* Read from future value */
336 value = curr->get_node()->get_future_value();
337 curr->read_from(NULL);
338 Promise *valuepromise = new Promise(curr, value);
339 promises->push_back(valuepromise);
341 } else if (curr->is_write()) {
342 if (w_modification_order(curr))
344 if (resolve_promises(curr))
349 resolve_release_sequences(curr->get_location());
351 th->set_return_value(value);
353 /* Add action to list. */
355 add_action_to_lists(curr);
357 Node *currnode = curr->get_node();
358 Node *parnode = currnode->get_parent();
360 if (!parnode->backtrack_empty() || !currnode->read_from_empty() ||
361 !currnode->future_value_empty() || !currnode->promise_empty())
362 if (!priv->next_backtrack || *curr > *priv->next_backtrack)
363 priv->next_backtrack = curr;
365 set_backtracking(curr);
367 /* Do not split atomic actions. */
369 return thread_current();
370 /* The THREAD_CREATE action points to the created Thread */
371 else if (curr->get_type() == THREAD_CREATE)
372 return (Thread *)curr->get_location();
374 return get_next_replay_thread();
377 /** @returns whether the current partial trace must be a prefix of a
379 bool ModelChecker::isfeasibleprefix() {
380 return promises->size() == 0 && *lazy_sync_size == 0;
383 /** @returns whether the current partial trace is feasible. */
384 bool ModelChecker::isfeasible() {
385 return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads;
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 (!priv->next_backtrack || *act > *priv->next_backtrack))
531 priv->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 /* We need a RMW action that is both an acquire and release to stop */
572 /** @todo Need to be smarter here... In the linux lock
573 * example, this will run to the beginning of the program for
575 if (rf->is_acquire() && rf->is_release())
576 return true; /* complete */
577 return release_seq_head(rf->get_reads_from(), release_heads);
579 if (rf->is_release())
580 return true; /* complete */
582 /* else relaxed write; check modification order for contiguous subsequence
583 * -> rf must be same thread as release */
584 int tid = id_to_int(rf->get_tid());
585 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
586 action_list_t *list = &(*thrd_lists)[tid];
587 action_list_t::const_reverse_iterator rit;
589 /* Find rf in the thread list */
590 rit = std::find(list->rbegin(), list->rend(), rf);
591 ASSERT(rit != list->rend());
593 /* Find the last write/release */
594 for (; rit != list->rend(); rit++)
595 if ((*rit)->is_release())
597 if (rit == list->rend()) {
598 /* No write-release in this thread */
599 return true; /* complete */
601 ModelAction *release = *rit;
603 ASSERT(rf->same_thread(release));
606 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
607 if (id_to_int(rf->get_tid()) == (int)i)
609 list = &(*thrd_lists)[i];
611 /* Can we ensure no future writes from this thread may break
612 * the release seq? */
613 bool future_ordered = false;
615 for (rit = list->rbegin(); rit != list->rend(); rit++) {
616 const ModelAction *act = *rit;
617 if (!act->is_write())
619 /* Reach synchronization -> this thread is complete */
620 if (act->happens_before(release))
622 if (rf->happens_before(act)) {
623 future_ordered = true;
627 /* Check modification order */
628 if (mo_graph->checkReachable(rf, act)) {
630 future_ordered = true;
633 if (mo_graph->checkReachable(act, release))
634 /* act --mo--> release */
636 if (mo_graph->checkReachable(release, act) &&
637 mo_graph->checkReachable(act, rf)) {
638 /* release --mo-> act --mo--> rf */
639 return true; /* complete */
644 return false; /* This thread is uncertain */
648 release_heads->push_back(release);
653 * A public interface for getting the release sequence head(s) with which a
654 * given ModelAction must synchronize. This function only returns a non-empty
655 * result when it can locate a release sequence head with certainty. Otherwise,
656 * it may mark the internal state of the ModelChecker so that it will handle
657 * the release sequence at a later time, causing @a act to update its
658 * synchronization at some later point in execution.
659 * @param act The 'acquire' action that may read from a release sequence
660 * @param release_heads A pass-by-reference return parameter. Will be filled
661 * with the head(s) of the release sequence(s), if they exists with certainty.
662 * @see ModelChecker::release_seq_head
664 void ModelChecker::get_release_seq_heads(ModelAction *act,
665 std::vector<const ModelAction *> *release_heads)
667 const ModelAction *rf = act->get_reads_from();
669 complete = release_seq_head(rf, release_heads);
671 /* add act to 'lazy checking' list */
672 std::list<ModelAction *> *list;
673 list = lazy_sync_with_release->get_safe_ptr(act->get_location());
674 list->push_back(act);
680 * Attempt to resolve all stashed operations that might synchronize with a
681 * release sequence for a given location. This implements the "lazy" portion of
682 * determining whether or not a release sequence was contiguous, since not all
683 * modification order information is present at the time an action occurs.
685 * @param location The location/object that should be checked for release
686 * sequence resolutions
687 * @return True if any updates occurred (new synchronization, new mo_graph edges)
689 bool ModelChecker::resolve_release_sequences(void *location)
691 std::list<ModelAction *> *list;
692 list = lazy_sync_with_release->getptr(location);
696 bool updated = false;
697 std::list<ModelAction *>::iterator it = list->begin();
698 while (it != list->end()) {
699 ModelAction *act = *it;
700 const ModelAction *rf = act->get_reads_from();
701 std::vector<const ModelAction *> release_heads;
703 complete = release_seq_head(rf, &release_heads);
704 for (unsigned int i = 0; i < release_heads.size(); i++) {
705 if (!act->has_synchronized_with(release_heads[i])) {
707 act->synchronize_with(release_heads[i]);
712 /* propagate synchronization to later actions */
713 action_list_t::reverse_iterator it = action_trace->rbegin();
714 while ((*it) != act) {
715 ModelAction *propagate = *it;
716 if (act->happens_before(propagate))
717 /** @todo new mo_graph edges along with
718 * this synchronization? */
719 propagate->synchronize_with(act);
723 it = list->erase(it);
729 // If we resolved promises or data races, see if we have realized a data race.
730 if (checkDataRaces()) {
738 * Performs various bookkeeping operations for the current ModelAction. For
739 * instance, adds action to the per-object, per-thread action vector and to the
740 * action trace list of all thread actions.
742 * @param act is the ModelAction to add.
744 void ModelChecker::add_action_to_lists(ModelAction *act)
746 int tid = id_to_int(act->get_tid());
747 action_trace->push_back(act);
749 obj_map->get_safe_ptr(act->get_location())->push_back(act);
751 std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
752 if (tid >= (int)vec->size())
753 vec->resize(priv->next_thread_id);
754 (*vec)[tid].push_back(act);
756 if ((int)thrd_last_action->size() <= tid)
757 thrd_last_action->resize(get_num_threads());
758 (*thrd_last_action)[tid] = act;
761 ModelAction * ModelChecker::get_last_action(thread_id_t tid)
763 int nthreads = get_num_threads();
764 if ((int)thrd_last_action->size() < nthreads)
765 thrd_last_action->resize(nthreads);
766 return (*thrd_last_action)[id_to_int(tid)];
770 * Gets the last memory_order_seq_cst action (in the total global sequence)
771 * performed on a particular object (i.e., memory location).
772 * @param location The object location to check
773 * @return The last seq_cst action performed
775 ModelAction * ModelChecker::get_last_seq_cst(const void *location)
777 action_list_t *list = obj_map->get_safe_ptr(location);
778 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
779 action_list_t::reverse_iterator rit;
780 for (rit = list->rbegin(); rit != list->rend(); rit++)
781 if ((*rit)->is_write() && (*rit)->is_seqcst())
786 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
788 ModelAction *parent = get_last_action(tid);
790 parent = get_thread(tid)->get_creation();
795 * Returns the clock vector for a given thread.
796 * @param tid The thread whose clock vector we want
797 * @return Desired clock vector
799 ClockVector * ModelChecker::get_cv(thread_id_t tid)
801 return get_parent_action(tid)->get_cv();
805 * Resolve a set of Promises with a current write. The set is provided in the
806 * Node corresponding to @a write.
807 * @param write The ModelAction that is fulfilling Promises
808 * @return True if promises were resolved; false otherwise
810 bool ModelChecker::resolve_promises(ModelAction *write)
812 bool resolved = false;
813 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
814 Promise *promise = (*promises)[promise_index];
815 if (write->get_node()->get_promise(i)) {
816 ModelAction *read = promise->get_action();
817 read->read_from(write);
818 r_modification_order(read, write);
819 post_r_modification_order(read, write);
820 promises->erase(promises->begin() + promise_index);
830 * Compute the set of promises that could potentially be satisfied by this
831 * action. Note that the set computation actually appears in the Node, not in
833 * @param curr The ModelAction that may satisfy promises
835 void ModelChecker::compute_promises(ModelAction *curr)
837 for (unsigned int i = 0; i < promises->size(); i++) {
838 Promise *promise = (*promises)[i];
839 const ModelAction *act = promise->get_action();
840 if (!act->happens_before(curr) &&
842 !act->is_synchronizing(curr) &&
843 !act->same_thread(curr) &&
844 promise->get_value() == curr->get_value()) {
845 curr->get_node()->set_promise(i);
850 /** Checks promises in response to change in ClockVector Threads. */
851 void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv)
853 for (unsigned int i = 0; i < promises->size(); i++) {
854 Promise *promise = (*promises)[i];
855 const ModelAction *act = promise->get_action();
856 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
857 merge_cv->synchronized_since(act)) {
858 //This thread is no longer able to send values back to satisfy the promise
859 int num_synchronized_threads = promise->increment_threads();
860 if (num_synchronized_threads == get_num_threads()) {
862 failed_promise = true;
870 * Build up an initial set of all past writes that this 'read' action may read
871 * from. This set is determined by the clock vector's "happens before"
873 * @param curr is the current ModelAction that we are exploring; it must be a
876 void ModelChecker::build_reads_from_past(ModelAction *curr)
878 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
880 ASSERT(curr->is_read());
882 ModelAction *last_seq_cst = NULL;
884 /* Track whether this object has been initialized */
885 bool initialized = false;
887 if (curr->is_seqcst()) {
888 last_seq_cst = get_last_seq_cst(curr->get_location());
889 /* We have to at least see the last sequentially consistent write,
890 so we are initialized. */
891 if (last_seq_cst != NULL)
895 /* Iterate over all threads */
896 for (i = 0; i < thrd_lists->size(); i++) {
897 /* Iterate over actions in thread, starting from most recent */
898 action_list_t *list = &(*thrd_lists)[i];
899 action_list_t::reverse_iterator rit;
900 for (rit = list->rbegin(); rit != list->rend(); rit++) {
901 ModelAction *act = *rit;
903 /* Only consider 'write' actions */
904 if (!act->is_write())
907 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
908 if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
909 DEBUG("Adding action to may_read_from:\n");
914 curr->get_node()->add_read_from(act);
917 /* Include at most one act per-thread that "happens before" curr */
918 if (act->happens_before(curr)) {
926 /** @todo Need a more informative way of reporting errors. */
927 printf("ERROR: may read from uninitialized atomic\n");
930 if (DBG_ENABLED() || !initialized) {
931 printf("Reached read action:\n");
933 printf("Printing may_read_from\n");
934 curr->get_node()->print_may_read_from();
935 printf("End printing may_read_from\n");
941 static void print_list(action_list_t *list)
943 action_list_t::iterator it;
945 printf("---------------------------------------------------------------------\n");
948 for (it = list->begin(); it != list->end(); it++) {
951 printf("---------------------------------------------------------------------\n");
954 void ModelChecker::print_summary()
957 printf("Number of executions: %d\n", num_executions);
958 printf("Total nodes created: %d\n", node_stack->get_total_nodes());
962 if (!isfinalfeasible())
963 printf("INFEASIBLE EXECUTION!\n");
964 print_list(action_trace);
969 * Add a Thread to the system for the first time. Should only be called once
971 * @param t The Thread to add
973 void ModelChecker::add_thread(Thread *t)
975 thread_map->put(id_to_int(t->get_id()), t);
976 scheduler->add_thread(t);
979 void ModelChecker::remove_thread(Thread *t)
981 scheduler->remove_thread(t);
985 * Switch from a user-context to the "master thread" context (a.k.a. system
986 * context). This switch is made with the intention of exploring a particular
987 * model-checking action (described by a ModelAction object). Must be called
988 * from a user-thread context.
989 * @param act The current action that will be explored. Must not be NULL.
990 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
992 int ModelChecker::switch_to_master(ModelAction *act)
995 Thread *old = thread_current();
996 set_current_action(act);
997 old->set_state(THREAD_READY);
998 return Thread::swap(old, &system_context);
1002 * Takes the next step in the execution, if possible.
1003 * @return Returns true (success) if a step was taken and false otherwise.
1005 bool ModelChecker::take_step() {
1006 Thread *curr, *next;
1011 curr = thread_current();
1013 if (curr->get_state() == THREAD_READY) {
1014 ASSERT(priv->current_action);
1015 priv->nextThread = check_current_action(priv->current_action);
1016 priv->current_action = NULL;
1017 if (!curr->is_blocked() && !curr->is_complete())
1018 scheduler->add_thread(curr);
1023 next = scheduler->next_thread(priv->nextThread);
1025 /* Infeasible -> don't take any more steps */
1030 next->set_state(THREAD_RUNNING);
1031 DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
1033 /* next == NULL -> don't take any more steps */
1036 /* Return false only if swap fails with an error */
1037 return (Thread::swap(&system_context, next) == 0);
1040 /** Runs the current execution until threre are no more steps to take. */
1041 void ModelChecker::finish_execution() {
1044 while (take_step());