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 futurevalues(new std::vector<struct PendingFutureValue>()),
32 lazy_sync_with_release(new HashTable<void *, std::list<ModelAction *>, uintptr_t, 4>()),
33 thrd_last_action(new std::vector<ModelAction *>(1)),
34 node_stack(new NodeStack()),
35 mo_graph(new CycleGraph()),
36 failed_promise(false),
37 too_many_reads(false),
40 /* Allocate this "size" on the snapshotting heap */
41 priv = (struct model_snapshot_members *)calloc(1, sizeof(*priv));
42 /* First thread created will have id INITIAL_THREAD_ID */
43 priv->next_thread_id = INITIAL_THREAD_ID;
45 lazy_sync_size = &priv->lazy_sync_size;
48 /** @brief Destructor */
49 ModelChecker::~ModelChecker()
51 for (int i = 0; i < get_num_threads(); i++)
52 delete thread_map->get(i);
59 for (unsigned int i = 0; i < promises->size(); i++)
60 delete (*promises)[i];
63 delete lazy_sync_with_release;
65 delete thrd_last_action;
72 * Restores user program to initial state and resets all model-checker data
75 void ModelChecker::reset_to_initial_state()
77 DEBUG("+++ Resetting to initial state +++\n");
78 node_stack->reset_execution();
79 failed_promise = false;
80 too_many_reads = false;
82 snapshotObject->backTrackBeforeStep(0);
85 /** @returns a thread ID for a new Thread */
86 thread_id_t ModelChecker::get_next_id()
88 return priv->next_thread_id++;
91 /** @returns the number of user threads created during this execution */
92 int ModelChecker::get_num_threads()
94 return priv->next_thread_id;
97 /** @returns a sequence number for a new ModelAction */
98 modelclock_t ModelChecker::get_next_seq_num()
100 return ++priv->used_sequence_numbers;
104 * @brief Choose the next thread to execute.
106 * This function chooses the next thread that should execute. It can force the
107 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
108 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
109 * The model-checker may have no preference regarding the next thread (i.e.,
110 * when exploring a new execution ordering), in which case this will return
112 * @param curr The current ModelAction. This action might guide the choice of
114 * @return The next thread to run. If the model-checker has no preference, NULL.
116 Thread * ModelChecker::get_next_thread(ModelAction *curr)
120 /* Do not split atomic actions. */
122 return thread_current();
123 /* The THREAD_CREATE action points to the created Thread */
124 else if (curr->get_type() == THREAD_CREATE)
125 return (Thread *)curr->get_location();
127 /* Have we completed exploring the preselected path? */
131 /* Else, we are trying to replay an execution */
132 ModelAction *next = node_stack->get_next()->get_action();
134 if (next == diverge) {
135 Node *nextnode = next->get_node();
136 /* Reached divergence point */
137 if (nextnode->increment_promise()) {
138 /* The next node will try to satisfy a different set of promises. */
139 tid = next->get_tid();
140 node_stack->pop_restofstack(2);
141 } else if (nextnode->increment_read_from()) {
142 /* The next node will read from a different value. */
143 tid = next->get_tid();
144 node_stack->pop_restofstack(2);
145 } else if (nextnode->increment_future_value()) {
146 /* The next node will try to read from a different future value. */
147 tid = next->get_tid();
148 node_stack->pop_restofstack(2);
150 /* Make a different thread execute for next step */
151 Node *node = nextnode->get_parent();
152 tid = node->get_next_backtrack();
153 node_stack->pop_restofstack(1);
155 DEBUG("*** Divergence point ***\n");
158 tid = next->get_tid();
160 DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
161 ASSERT(tid != THREAD_ID_T_NONE);
162 return thread_map->get(id_to_int(tid));
166 * Queries the model-checker for more executions to explore and, if one
167 * exists, resets the model-checker state to execute a new execution.
169 * @return If there are more executions to explore, return true. Otherwise,
172 bool ModelChecker::next_execution()
178 if (isfinalfeasible() || DBG_ENABLED())
181 if ((diverge = get_next_backtrack()) == NULL)
185 printf("Next execution will diverge at:\n");
189 reset_to_initial_state();
193 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
195 action_type type = act->get_type();
205 /* linear search: from most recent to oldest */
206 action_list_t *list = obj_map->get_safe_ptr(act->get_location());
207 action_list_t::reverse_iterator rit;
208 for (rit = list->rbegin(); rit != list->rend(); rit++) {
209 ModelAction *prev = *rit;
210 if (act->is_synchronizing(prev))
216 void ModelChecker::set_backtracking(ModelAction *act)
220 Thread *t = get_thread(act);
222 prev = get_last_conflict(act);
226 node = prev->get_node()->get_parent();
228 while (!node->is_enabled(t))
231 /* Check if this has been explored already */
232 if (node->has_been_explored(t->get_id()))
235 /* Cache the latest backtracking point */
236 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
237 priv->next_backtrack = prev;
239 /* If this is a new backtracking point, mark the tree */
240 if (!node->set_backtrack(t->get_id()))
242 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
243 prev->get_tid(), t->get_id());
251 * Returns last backtracking point. The model checker will explore a different
252 * path for this point in the next execution.
253 * @return The ModelAction at which the next execution should diverge.
255 ModelAction * ModelChecker::get_next_backtrack()
257 ModelAction *next = priv->next_backtrack;
258 priv->next_backtrack = NULL;
263 * Processes a read or rmw model action.
264 * @param curr is the read model action to process.
265 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
266 * @return True if processing this read updates the mo_graph.
268 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
271 bool updated = false;
273 const ModelAction *reads_from = curr->get_node()->get_read_from();
274 if (reads_from != NULL) {
275 mo_graph->startChanges();
277 value = reads_from->get_value();
278 bool r_status = false;
280 if (!second_part_of_rmw) {
281 check_recency(curr,false);
282 r_status = r_modification_order(curr, reads_from);
286 if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
287 mo_graph->rollbackChanges();
288 too_many_reads = false;
292 curr->read_from(reads_from);
293 mo_graph->commitChanges();
295 } else if (!second_part_of_rmw) {
296 /* Read from future value */
297 value = curr->get_node()->get_future_value();
298 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
299 curr->read_from(NULL);
300 Promise *valuepromise = new Promise(curr, value, expiration);
301 promises->push_back(valuepromise);
303 get_thread(curr)->set_return_value(value);
309 * Process a write ModelAction
310 * @param curr The ModelAction to process
311 * @return True if the mo_graph was updated or promises were resolved
313 bool ModelChecker::process_write(ModelAction *curr)
315 bool updated_mod_order = w_modification_order(curr);
316 bool updated_promises = resolve_promises(curr);
318 if (promises->size() == 0) {
319 for (unsigned int i = 0; i<futurevalues->size(); i++) {
320 struct PendingFutureValue pfv = (*futurevalues)[i];
321 if (pfv.act->get_node()->add_future_value(pfv.value, pfv.expiration) &&
322 (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
323 priv->next_backtrack = pfv.act;
325 futurevalues->resize(0);
328 mo_graph->commitChanges();
329 get_thread(curr)->set_return_value(VALUE_NONE);
330 return updated_mod_order || updated_promises;
334 * This is the heart of the model checker routine. It performs model-checking
335 * actions corresponding to a given "current action." Among other processes, it
336 * calculates reads-from relationships, updates synchronization clock vectors,
337 * forms a memory_order constraints graph, and handles replay/backtrack
338 * execution when running permutations of previously-observed executions.
340 * @param curr The current action to process
341 * @return The next Thread that must be executed. May be NULL if ModelChecker
342 * makes no choice (e.g., according to replay execution, combining RMW actions,
345 Thread * ModelChecker::check_current_action(ModelAction *curr)
347 bool second_part_of_rmw = false;
351 if (curr->is_rmwc() || curr->is_rmw()) {
352 ModelAction *tmp = process_rmw(curr);
353 second_part_of_rmw = true;
356 compute_promises(curr);
358 ModelAction *tmp = node_stack->explore_action(curr);
360 /* Discard duplicate ModelAction; use action from NodeStack */
361 /* First restore type and order in case of RMW operation */
363 tmp->copy_typeandorder(curr);
365 /* If we have diverged, we need to reset the clock vector. */
367 tmp->create_cv(get_parent_action(tmp->get_tid()));
373 * Perform one-time actions when pushing new ModelAction onto
376 curr->create_cv(get_parent_action(curr->get_tid()));
377 /* Build may_read_from set */
379 build_reads_from_past(curr);
380 if (curr->is_write())
381 compute_promises(curr);
385 /* Thread specific actions */
386 switch (curr->get_type()) {
387 case THREAD_CREATE: {
388 Thread *th = (Thread *)curr->get_location();
389 th->set_creation(curr);
393 Thread *waiting, *blocking;
394 waiting = get_thread(curr);
395 blocking = (Thread *)curr->get_location();
396 if (!blocking->is_complete()) {
397 blocking->push_wait_list(curr);
398 scheduler->sleep(waiting);
402 case THREAD_FINISH: {
403 Thread *th = get_thread(curr);
404 while (!th->wait_list_empty()) {
405 ModelAction *act = th->pop_wait_list();
406 Thread *wake = get_thread(act);
407 scheduler->wake(wake);
413 check_promises(NULL, curr->get_cv());
420 bool updated = false;
422 if (curr->is_read() && process_read(curr, second_part_of_rmw))
425 if (curr->is_write() && process_write(curr))
429 resolve_release_sequences(curr->get_location());
431 /* Add action to list. */
432 if (!second_part_of_rmw)
433 add_action_to_lists(curr);
435 check_curr_backtracking(curr);
437 set_backtracking(curr);
439 return get_next_thread(curr);
442 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
443 Node *currnode = curr->get_node();
444 Node *parnode = currnode->get_parent();
446 if ((!parnode->backtrack_empty() ||
447 !currnode->read_from_empty() ||
448 !currnode->future_value_empty() ||
449 !currnode->promise_empty())
450 && (!priv->next_backtrack ||
451 *curr > *priv->next_backtrack)) {
452 priv->next_backtrack = curr;
456 bool ModelChecker::promises_expired() {
457 for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
458 Promise *promise = (*promises)[promise_index];
459 if (promise->get_expiration()<priv->used_sequence_numbers) {
466 /** @returns whether the current partial trace must be a prefix of a
468 bool ModelChecker::isfeasibleprefix() {
469 return promises->size() == 0 && *lazy_sync_size == 0;
472 /** @returns whether the current partial trace is feasible. */
473 bool ModelChecker::isfeasible() {
474 return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW();
477 /** @returns whether the current partial trace is feasible other than
478 * multiple RMW reading from the same store. */
479 bool ModelChecker::isfeasibleotherthanRMW() {
480 return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !promises_expired();
483 /** Returns whether the current completed trace is feasible. */
484 bool ModelChecker::isfinalfeasible() {
485 return isfeasible() && promises->size() == 0;
488 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
489 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
490 int tid = id_to_int(act->get_tid());
491 ModelAction *lastread = get_last_action(tid);
492 lastread->process_rmw(act);
493 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
494 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
495 mo_graph->commitChanges();
501 * Checks whether a thread has read from the same write for too many times
502 * without seeing the effects of a later write.
505 * 1) there must a different write that we could read from that would satisfy the modification order,
506 * 2) we must have read from the same value in excess of maxreads times, and
507 * 3) that other write must have been in the reads_from set for maxreads times.
509 * If so, we decide that the execution is no longer feasible.
511 void ModelChecker::check_recency(ModelAction *curr, bool already_added) {
512 if (params.maxreads != 0) {
513 if (curr->get_node()->get_read_from_size() <= 1)
516 //Must make sure that execution is currently feasible... We could
517 //accidentally clear by rolling back
521 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
522 int tid = id_to_int(curr->get_tid());
525 if ((int)thrd_lists->size() <= tid)
528 action_list_t *list = &(*thrd_lists)[tid];
530 action_list_t::reverse_iterator rit = list->rbegin();
533 for (; (*rit) != curr; rit++)
535 /* go past curr now */
539 action_list_t::reverse_iterator ritcopy = rit;
540 //See if we have enough reads from the same value
542 for (; count < params.maxreads; rit++,count++) {
543 if (rit==list->rend())
545 ModelAction *act = *rit;
548 if (act->get_reads_from() != curr->get_reads_from())
550 if (act->get_node()->get_read_from_size() <= 1)
554 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
556 const ModelAction * write = curr->get_node()->get_read_from_at(i);
557 //Need a different write
558 if (write==curr->get_reads_from())
561 /* Test to see whether this is a feasible write to read from*/
562 mo_graph->startChanges();
563 r_modification_order(curr, write);
564 bool feasiblereadfrom = isfeasible();
565 mo_graph->rollbackChanges();
567 if (!feasiblereadfrom)
571 bool feasiblewrite = true;
572 //new we need to see if this write works for everyone
574 for (int loop = count; loop>0; loop--,rit++) {
575 ModelAction *act=*rit;
576 bool foundvalue = false;
577 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
578 if (act->get_node()->get_read_from_at(i)==write) {
584 feasiblewrite = false;
589 too_many_reads = true;
597 * Updates the mo_graph with the constraints imposed from the current read.
598 * @param curr The current action. Must be a read.
599 * @param rf The action that curr reads from. Must be a write.
600 * @return True if modification order edges were added; false otherwise
602 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
604 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
607 ASSERT(curr->is_read());
609 /* Iterate over all threads */
610 for (i = 0; i < thrd_lists->size(); i++) {
611 /* Iterate over actions in thread, starting from most recent */
612 action_list_t *list = &(*thrd_lists)[i];
613 action_list_t::reverse_iterator rit;
614 for (rit = list->rbegin(); rit != list->rend(); rit++) {
615 ModelAction *act = *rit;
617 /* Include at most one act per-thread that "happens before" curr */
618 if (act->happens_before(curr)) {
619 if (act->is_write()) {
620 if (rf != act && act != curr) {
621 mo_graph->addEdge(act, rf);
625 const ModelAction *prevreadfrom = act->get_reads_from();
626 if (prevreadfrom != NULL && rf != prevreadfrom) {
627 mo_graph->addEdge(prevreadfrom, rf);
640 /** Updates the mo_graph with the constraints imposed from the current read. */
641 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
643 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
645 ASSERT(curr->is_read());
647 /* Iterate over all threads */
648 for (i = 0; i < thrd_lists->size(); i++) {
649 /* Iterate over actions in thread, starting from most recent */
650 action_list_t *list = &(*thrd_lists)[i];
651 action_list_t::reverse_iterator rit;
652 ModelAction *lastact = NULL;
654 /* Find last action that happens after curr */
655 for (rit = list->rbegin(); rit != list->rend(); rit++) {
656 ModelAction *act = *rit;
657 if (curr->happens_before(act)) {
663 /* Include at most one act per-thread that "happens before" curr */
664 if (lastact != NULL) {
665 if (lastact->is_read()) {
666 const ModelAction *postreadfrom = lastact->get_reads_from();
667 if (postreadfrom != NULL&&rf != postreadfrom)
668 mo_graph->addEdge(rf, postreadfrom);
669 } else if (rf != lastact) {
670 mo_graph->addEdge(rf, lastact);
678 * Updates the mo_graph with the constraints imposed from the current write.
679 * @param curr The current action. Must be a write.
680 * @return True if modification order edges were added; false otherwise
682 bool ModelChecker::w_modification_order(ModelAction *curr)
684 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
687 ASSERT(curr->is_write());
689 if (curr->is_seqcst()) {
690 /* We have to at least see the last sequentially consistent write,
691 so we are initialized. */
692 ModelAction *last_seq_cst = get_last_seq_cst(curr->get_location());
693 if (last_seq_cst != NULL) {
694 mo_graph->addEdge(last_seq_cst, curr);
699 /* Iterate over all threads */
700 for (i = 0; i < thrd_lists->size(); i++) {
701 /* Iterate over actions in thread, starting from most recent */
702 action_list_t *list = &(*thrd_lists)[i];
703 action_list_t::reverse_iterator rit;
704 for (rit = list->rbegin(); rit != list->rend(); rit++) {
705 ModelAction *act = *rit;
707 /* Include at most one act per-thread that "happens before" curr */
708 if (act->happens_before(curr)) {
710 * Note: if act is RMW, just add edge:
712 * The following edge should be handled elsewhere:
713 * readfrom(act) --mo--> act
715 if (act->is_write()) {
716 //RMW shouldn't have an edge to themselves
718 mo_graph->addEdge(act, curr);
719 } else if (act->is_read() && act->get_reads_from() != NULL)
720 mo_graph->addEdge(act->get_reads_from(), curr);
723 } else if (act->is_read() && !act->is_synchronizing(curr) &&
724 !act->same_thread(curr)) {
725 /* We have an action that:
726 (1) did not happen before us
727 (2) is a read and we are a write
728 (3) cannot synchronize with us
729 (4) is in a different thread
731 that read could potentially read from our write.
733 if (thin_air_constraint_may_allow(curr, act)) {
735 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from()==act->get_reads_from() && isfeasibleotherthanRMW())) {
736 struct PendingFutureValue pfv = {curr->get_value(),curr->get_seq_number()+params.maxfuturedelay,act};
737 futurevalues->push_back(pfv);
747 /** Arbitrary reads from the future are not allowed. Section 29.3
748 * part 9 places some constraints. This method checks one result of constraint
749 * constraint. Others require compiler support. */
751 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
752 if (!writer->is_rmw())
755 if (!reader->is_rmw())
758 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
761 if (search->get_tid() == reader->get_tid() &&
762 search->happens_before(reader))
770 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
771 * The ModelAction under consideration is expected to be taking part in
772 * release/acquire synchronization as an object of the "reads from" relation.
773 * Note that this can only provide release sequence support for RMW chains
774 * which do not read from the future, as those actions cannot be traced until
775 * their "promise" is fulfilled. Similarly, we may not even establish the
776 * presence of a release sequence with certainty, as some modification order
777 * constraints may be decided further in the future. Thus, this function
778 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
779 * and a boolean representing certainty.
781 * @todo Finish lazy updating, when promises are fulfilled in the future
782 * @param rf The action that might be part of a release sequence. Must be a
784 * @param release_heads A pass-by-reference style return parameter. After
785 * execution of this function, release_heads will contain the heads of all the
786 * relevant release sequences, if any exists
787 * @return true, if the ModelChecker is certain that release_heads is complete;
790 bool ModelChecker::release_seq_head(const ModelAction *rf,
791 std::vector< const ModelAction *, MyAlloc<const ModelAction *> > *release_heads) const
794 /* read from future: need to settle this later */
795 return false; /* incomplete */
798 ASSERT(rf->is_write());
800 if (rf->is_release())
801 release_heads->push_back(rf);
803 /* We need a RMW action that is both an acquire and release to stop */
804 /** @todo Need to be smarter here... In the linux lock
805 * example, this will run to the beginning of the program for
807 if (rf->is_acquire() && rf->is_release())
808 return true; /* complete */
809 return release_seq_head(rf->get_reads_from(), release_heads);
811 if (rf->is_release())
812 return true; /* complete */
814 /* else relaxed write; check modification order for contiguous subsequence
815 * -> rf must be same thread as release */
816 int tid = id_to_int(rf->get_tid());
817 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
818 action_list_t *list = &(*thrd_lists)[tid];
819 action_list_t::const_reverse_iterator rit;
821 /* Find rf in the thread list */
822 rit = std::find(list->rbegin(), list->rend(), rf);
823 ASSERT(rit != list->rend());
825 /* Find the last write/release */
826 for (; rit != list->rend(); rit++)
827 if ((*rit)->is_release())
829 if (rit == list->rend()) {
830 /* No write-release in this thread */
831 return true; /* complete */
833 ModelAction *release = *rit;
835 ASSERT(rf->same_thread(release));
838 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
839 if (id_to_int(rf->get_tid()) == (int)i)
841 list = &(*thrd_lists)[i];
843 /* Can we ensure no future writes from this thread may break
844 * the release seq? */
845 bool future_ordered = false;
847 for (rit = list->rbegin(); rit != list->rend(); rit++) {
848 const ModelAction *act = *rit;
849 if (!act->is_write())
851 /* Reach synchronization -> this thread is complete */
852 if (act->happens_before(release))
854 if (rf->happens_before(act)) {
855 future_ordered = true;
859 /* Check modification order */
860 if (mo_graph->checkReachable(rf, act)) {
862 future_ordered = true;
865 if (mo_graph->checkReachable(act, release))
866 /* act --mo--> release */
868 if (mo_graph->checkReachable(release, act) &&
869 mo_graph->checkReachable(act, rf)) {
870 /* release --mo-> act --mo--> rf */
871 return true; /* complete */
876 return false; /* This thread is uncertain */
880 release_heads->push_back(release);
885 * A public interface for getting the release sequence head(s) with which a
886 * given ModelAction must synchronize. This function only returns a non-empty
887 * result when it can locate a release sequence head with certainty. Otherwise,
888 * it may mark the internal state of the ModelChecker so that it will handle
889 * the release sequence at a later time, causing @a act to update its
890 * synchronization at some later point in execution.
891 * @param act The 'acquire' action that may read from a release sequence
892 * @param release_heads A pass-by-reference return parameter. Will be filled
893 * with the head(s) of the release sequence(s), if they exists with certainty.
894 * @see ModelChecker::release_seq_head
896 void ModelChecker::get_release_seq_heads(ModelAction *act,
897 std::vector< const ModelAction *, MyAlloc<const ModelAction *> > *release_heads)
899 const ModelAction *rf = act->get_reads_from();
901 complete = release_seq_head(rf, release_heads);
903 /* add act to 'lazy checking' list */
904 std::list<ModelAction *> *list;
905 list = lazy_sync_with_release->get_safe_ptr(act->get_location());
906 list->push_back(act);
912 * Attempt to resolve all stashed operations that might synchronize with a
913 * release sequence for a given location. This implements the "lazy" portion of
914 * determining whether or not a release sequence was contiguous, since not all
915 * modification order information is present at the time an action occurs.
917 * @param location The location/object that should be checked for release
918 * sequence resolutions
919 * @return True if any updates occurred (new synchronization, new mo_graph edges)
921 bool ModelChecker::resolve_release_sequences(void *location)
923 std::list<ModelAction *> *list;
924 list = lazy_sync_with_release->getptr(location);
928 bool updated = false;
929 std::list<ModelAction *>::iterator it = list->begin();
930 while (it != list->end()) {
931 ModelAction *act = *it;
932 const ModelAction *rf = act->get_reads_from();
933 std::vector< const ModelAction *, MyAlloc<const ModelAction *> > release_heads;
935 complete = release_seq_head(rf, &release_heads);
936 for (unsigned int i = 0; i < release_heads.size(); i++) {
937 if (!act->has_synchronized_with(release_heads[i])) {
939 act->synchronize_with(release_heads[i]);
944 /* propagate synchronization to later actions */
945 action_list_t::reverse_iterator it = action_trace->rbegin();
946 while ((*it) != act) {
947 ModelAction *propagate = *it;
948 if (act->happens_before(propagate))
949 /** @todo new mo_graph edges along with
950 * this synchronization? */
951 propagate->synchronize_with(act);
955 it = list->erase(it);
961 // If we resolved promises or data races, see if we have realized a data race.
962 if (checkDataRaces()) {
970 * Performs various bookkeeping operations for the current ModelAction. For
971 * instance, adds action to the per-object, per-thread action vector and to the
972 * action trace list of all thread actions.
974 * @param act is the ModelAction to add.
976 void ModelChecker::add_action_to_lists(ModelAction *act)
978 int tid = id_to_int(act->get_tid());
979 action_trace->push_back(act);
981 obj_map->get_safe_ptr(act->get_location())->push_back(act);
983 std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
984 if (tid >= (int)vec->size())
985 vec->resize(priv->next_thread_id);
986 (*vec)[tid].push_back(act);
988 if ((int)thrd_last_action->size() <= tid)
989 thrd_last_action->resize(get_num_threads());
990 (*thrd_last_action)[tid] = act;
993 ModelAction * ModelChecker::get_last_action(thread_id_t tid)
995 int nthreads = get_num_threads();
996 if ((int)thrd_last_action->size() < nthreads)
997 thrd_last_action->resize(nthreads);
998 return (*thrd_last_action)[id_to_int(tid)];
1002 * Gets the last memory_order_seq_cst action (in the total global sequence)
1003 * performed on a particular object (i.e., memory location).
1004 * @param location The object location to check
1005 * @return The last seq_cst action performed
1007 ModelAction * ModelChecker::get_last_seq_cst(const void *location)
1009 action_list_t *list = obj_map->get_safe_ptr(location);
1010 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1011 action_list_t::reverse_iterator rit;
1012 for (rit = list->rbegin(); rit != list->rend(); rit++)
1013 if ((*rit)->is_write() && (*rit)->is_seqcst())
1018 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
1020 ModelAction *parent = get_last_action(tid);
1022 parent = get_thread(tid)->get_creation();
1027 * Returns the clock vector for a given thread.
1028 * @param tid The thread whose clock vector we want
1029 * @return Desired clock vector
1031 ClockVector * ModelChecker::get_cv(thread_id_t tid)
1033 return get_parent_action(tid)->get_cv();
1037 * Resolve a set of Promises with a current write. The set is provided in the
1038 * Node corresponding to @a write.
1039 * @param write The ModelAction that is fulfilling Promises
1040 * @return True if promises were resolved; false otherwise
1042 bool ModelChecker::resolve_promises(ModelAction *write)
1044 bool resolved = false;
1046 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
1047 Promise *promise = (*promises)[promise_index];
1048 if (write->get_node()->get_promise(i)) {
1049 ModelAction *read = promise->get_action();
1050 read->read_from(write);
1051 if (read->is_rmw()) {
1052 mo_graph->addRMWEdge(write, read);
1054 r_modification_order(read, write);
1055 post_r_modification_order(read, write);
1056 promises->erase(promises->begin() + promise_index);
1065 * Compute the set of promises that could potentially be satisfied by this
1066 * action. Note that the set computation actually appears in the Node, not in
1068 * @param curr The ModelAction that may satisfy promises
1070 void ModelChecker::compute_promises(ModelAction *curr)
1072 for (unsigned int i = 0; i < promises->size(); i++) {
1073 Promise *promise = (*promises)[i];
1074 const ModelAction *act = promise->get_action();
1075 if (!act->happens_before(curr) &&
1077 !act->is_synchronizing(curr) &&
1078 !act->same_thread(curr) &&
1079 promise->get_value() == curr->get_value()) {
1080 curr->get_node()->set_promise(i);
1085 /** Checks promises in response to change in ClockVector Threads. */
1086 void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv)
1088 for (unsigned int i = 0; i < promises->size(); i++) {
1089 Promise *promise = (*promises)[i];
1090 const ModelAction *act = promise->get_action();
1091 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
1092 merge_cv->synchronized_since(act)) {
1093 //This thread is no longer able to send values back to satisfy the promise
1094 int num_synchronized_threads = promise->increment_threads();
1095 if (num_synchronized_threads == get_num_threads()) {
1096 //Promise has failed
1097 failed_promise = true;
1105 * Build up an initial set of all past writes that this 'read' action may read
1106 * from. This set is determined by the clock vector's "happens before"
1108 * @param curr is the current ModelAction that we are exploring; it must be a
1111 void ModelChecker::build_reads_from_past(ModelAction *curr)
1113 std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
1115 ASSERT(curr->is_read());
1117 ModelAction *last_seq_cst = NULL;
1119 /* Track whether this object has been initialized */
1120 bool initialized = false;
1122 if (curr->is_seqcst()) {
1123 last_seq_cst = get_last_seq_cst(curr->get_location());
1124 /* We have to at least see the last sequentially consistent write,
1125 so we are initialized. */
1126 if (last_seq_cst != NULL)
1130 /* Iterate over all threads */
1131 for (i = 0; i < thrd_lists->size(); i++) {
1132 /* Iterate over actions in thread, starting from most recent */
1133 action_list_t *list = &(*thrd_lists)[i];
1134 action_list_t::reverse_iterator rit;
1135 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1136 ModelAction *act = *rit;
1138 /* Only consider 'write' actions */
1139 if (!act->is_write())
1142 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1143 if (!curr->is_seqcst()|| (!act->is_seqcst() && (last_seq_cst==NULL||!act->happens_before(last_seq_cst))) || act == last_seq_cst) {
1144 DEBUG("Adding action to may_read_from:\n");
1145 if (DBG_ENABLED()) {
1149 curr->get_node()->add_read_from(act);
1152 /* Include at most one act per-thread that "happens before" curr */
1153 if (act->happens_before(curr)) {
1161 /** @todo Need a more informative way of reporting errors. */
1162 printf("ERROR: may read from uninitialized atomic\n");
1165 if (DBG_ENABLED() || !initialized) {
1166 printf("Reached read action:\n");
1168 printf("Printing may_read_from\n");
1169 curr->get_node()->print_may_read_from();
1170 printf("End printing may_read_from\n");
1173 ASSERT(initialized);
1176 static void print_list(action_list_t *list)
1178 action_list_t::iterator it;
1180 printf("---------------------------------------------------------------------\n");
1183 for (it = list->begin(); it != list->end(); it++) {
1186 printf("---------------------------------------------------------------------\n");
1189 void ModelChecker::print_summary()
1192 printf("Number of executions: %d\n", num_executions);
1193 printf("Total nodes created: %d\n", node_stack->get_total_nodes());
1197 if (!isfinalfeasible())
1198 printf("INFEASIBLE EXECUTION!\n");
1199 print_list(action_trace);
1204 * Add a Thread to the system for the first time. Should only be called once
1206 * @param t The Thread to add
1208 void ModelChecker::add_thread(Thread *t)
1210 thread_map->put(id_to_int(t->get_id()), t);
1211 scheduler->add_thread(t);
1214 void ModelChecker::remove_thread(Thread *t)
1216 scheduler->remove_thread(t);
1220 * Switch from a user-context to the "master thread" context (a.k.a. system
1221 * context). This switch is made with the intention of exploring a particular
1222 * model-checking action (described by a ModelAction object). Must be called
1223 * from a user-thread context.
1224 * @param act The current action that will be explored. Must not be NULL.
1225 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
1227 int ModelChecker::switch_to_master(ModelAction *act)
1230 Thread *old = thread_current();
1231 set_current_action(act);
1232 old->set_state(THREAD_READY);
1233 return Thread::swap(old, &system_context);
1237 * Takes the next step in the execution, if possible.
1238 * @return Returns true (success) if a step was taken and false otherwise.
1240 bool ModelChecker::take_step() {
1241 Thread *curr, *next;
1246 curr = thread_current();
1248 if (curr->get_state() == THREAD_READY) {
1249 ASSERT(priv->current_action);
1251 priv->nextThread = check_current_action(priv->current_action);
1252 priv->current_action = NULL;
1253 if (!curr->is_blocked() && !curr->is_complete())
1254 scheduler->add_thread(curr);
1259 next = scheduler->next_thread(priv->nextThread);
1261 /* Infeasible -> don't take any more steps */
1266 next->set_state(THREAD_RUNNING);
1267 DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
1269 /* next == NULL -> don't take any more steps */
1272 /* Return false only if swap fails with an error */
1273 return (Thread::swap(&system_context, next) == 0);
1276 /** Runs the current execution until threre are no more steps to take. */
1277 void ModelChecker::finish_execution() {
1280 while (take_step());