10 #include "snapshot-interface.h"
12 #include "clockvector.h"
13 #include "cyclegraph.h"
16 #include "threads-model.h"
19 #define INITIAL_THREAD_ID 0
24 bug_message(const char *str) {
25 const char *fmt = " [BUG] %s\n";
26 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
27 sprintf(msg, fmt, str);
29 ~bug_message() { if (msg) snapshot_free(msg); }
32 void print() { model_print("%s", msg); }
38 * Structure for holding small ModelChecker members that should be snapshotted
40 struct model_snapshot_members {
41 model_snapshot_members() :
43 /* First thread created will have id INITIAL_THREAD_ID */
44 next_thread_id(INITIAL_THREAD_ID),
45 used_sequence_numbers(0),
49 failed_promise(false),
50 too_many_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 ModelAction *current_action;
62 unsigned int next_thread_id;
63 modelclock_t used_sequence_numbers;
64 ModelAction *next_backtrack;
65 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
66 struct execution_stats stats;
69 /** @brief Incorrectly-ordered synchronization was made */
70 bool bad_synchronization;
76 /** @brief Constructor */
77 ModelChecker::ModelChecker(struct model_params params) :
78 /* Initialize default scheduler */
80 scheduler(new Scheduler()),
82 earliest_diverge(NULL),
83 action_trace(new action_list_t()),
84 thread_map(new HashTable<int, Thread *, int>()),
85 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
86 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
89 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
90 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
91 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
92 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
93 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
123 delete thrd_last_fence_release;
130 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
132 action_list_t *tmp = hash->get(ptr);
134 tmp = new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
142 std::vector<action_list_t> *tmp = hash->get(ptr);
144 tmp = new std::vector<action_list_t>();
151 * Restores user program to initial state and resets all model-checker data
154 void ModelChecker::reset_to_initial_state()
156 DEBUG("+++ Resetting to initial state +++\n");
157 node_stack->reset_execution();
159 /* Print all model-checker output before rollback */
162 snapshot_backtrack_before(0);
165 /** @return a thread ID for a new Thread */
166 thread_id_t ModelChecker::get_next_id()
168 return priv->next_thread_id++;
171 /** @return the number of user threads created during this execution */
172 unsigned int ModelChecker::get_num_threads() const
174 return priv->next_thread_id;
178 * Must be called from user-thread context (e.g., through the global
179 * thread_current() interface)
181 * @return The currently executing Thread.
183 Thread * ModelChecker::get_current_thread() const
185 return scheduler->get_current_thread();
188 /** @return a sequence number for a new ModelAction */
189 modelclock_t ModelChecker::get_next_seq_num()
191 return ++priv->used_sequence_numbers;
194 Node * ModelChecker::get_curr_node() const
196 return node_stack->get_head();
200 * @brief Choose the next thread to execute.
202 * This function chooses the next thread that should execute. It can force the
203 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
204 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
205 * The model-checker may have no preference regarding the next thread (i.e.,
206 * when exploring a new execution ordering), in which case this will return
208 * @param curr The current ModelAction. This action might guide the choice of
210 * @return The next thread to run. If the model-checker has no preference, NULL.
212 Thread * ModelChecker::get_next_thread(ModelAction *curr)
217 /* Do not split atomic actions. */
219 return thread_current();
220 else if (curr->get_type() == THREAD_CREATE)
221 return curr->get_thread_operand();
224 /* Have we completed exploring the preselected path? */
228 /* Else, we are trying to replay an execution */
229 ModelAction *next = node_stack->get_next()->get_action();
231 if (next == diverge) {
232 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
233 earliest_diverge = diverge;
235 Node *nextnode = next->get_node();
236 Node *prevnode = nextnode->get_parent();
237 scheduler->update_sleep_set(prevnode);
239 /* Reached divergence point */
240 if (nextnode->increment_misc()) {
241 /* The next node will try to satisfy a different misc_index values. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_promise()) {
245 /* The next node will try to satisfy a different set of promises. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_read_from()) {
249 /* The next node will read from a different value. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_future_value()) {
253 /* The next node will try to read from a different future value. */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
256 } else if (nextnode->increment_relseq_break()) {
257 /* The next node will try to resolve a release sequence differently */
258 tid = next->get_tid();
259 node_stack->pop_restofstack(2);
262 /* Make a different thread execute for next step */
263 scheduler->add_sleep(get_thread(next->get_tid()));
264 tid = prevnode->get_next_backtrack();
265 /* Make sure the backtracked thread isn't sleeping. */
266 node_stack->pop_restofstack(1);
267 if (diverge == earliest_diverge) {
268 earliest_diverge = prevnode->get_action();
271 /* The correct sleep set is in the parent node. */
274 DEBUG("*** Divergence point ***\n");
278 tid = next->get_tid();
280 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
281 ASSERT(tid != THREAD_ID_T_NONE);
282 return thread_map->get(id_to_int(tid));
286 * We need to know what the next actions of all threads in the sleep
287 * set will be. This method computes them and stores the actions at
288 * the corresponding thread object's pending action.
291 void ModelChecker::execute_sleep_set()
293 for (unsigned int i = 0; i < get_num_threads(); i++) {
294 thread_id_t tid = int_to_id(i);
295 Thread *thr = get_thread(tid);
296 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
297 thr->set_state(THREAD_RUNNING);
298 scheduler->next_thread(thr);
299 Thread::swap(&system_context, thr);
300 priv->current_action->set_sleep_flag();
301 thr->set_pending(priv->current_action);
306 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
308 for (unsigned int i = 0; i < get_num_threads(); i++) {
309 Thread *thr = get_thread(int_to_id(i));
310 if (scheduler->is_sleep_set(thr)) {
311 ModelAction *pending_act = thr->get_pending();
312 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
313 //Remove this thread from sleep set
314 scheduler->remove_sleep(thr);
319 /** @brief Alert the model-checker that an incorrectly-ordered
320 * synchronization was made */
321 void ModelChecker::set_bad_synchronization()
323 priv->bad_synchronization = true;
326 bool ModelChecker::has_asserted() const
328 return priv->asserted;
331 void ModelChecker::set_assert()
333 priv->asserted = true;
337 * Check if we are in a deadlock. Should only be called at the end of an
338 * execution, although it should not give false positives in the middle of an
339 * execution (there should be some ENABLED thread).
341 * @return True if program is in a deadlock; false otherwise
343 bool ModelChecker::is_deadlocked() const
345 bool blocking_threads = false;
346 for (unsigned int i = 0; i < get_num_threads(); i++) {
347 thread_id_t tid = int_to_id(i);
350 Thread *t = get_thread(tid);
351 if (!t->is_model_thread() && t->get_pending())
352 blocking_threads = true;
354 return blocking_threads;
358 * Check if this is a complete execution. That is, have all thread completed
359 * execution (rather than exiting because sleep sets have forced a redundant
362 * @return True if the execution is complete.
364 bool ModelChecker::is_complete_execution() const
366 for (unsigned int i = 0; i < get_num_threads(); i++)
367 if (is_enabled(int_to_id(i)))
373 * @brief Assert a bug in the executing program.
375 * Use this function to assert any sort of bug in the user program. If the
376 * current trace is feasible (actually, a prefix of some feasible execution),
377 * then this execution will be aborted, printing the appropriate message. If
378 * the current trace is not yet feasible, the error message will be stashed and
379 * printed if the execution ever becomes feasible.
381 * @param msg Descriptive message for the bug (do not include newline char)
382 * @return True if bug is immediately-feasible
384 bool ModelChecker::assert_bug(const char *msg)
386 priv->bugs.push_back(new bug_message(msg));
388 if (isfeasibleprefix()) {
396 * @brief Assert a bug in the executing program, asserted by a user thread
397 * @see ModelChecker::assert_bug
398 * @param msg Descriptive message for the bug (do not include newline char)
400 void ModelChecker::assert_user_bug(const char *msg)
402 /* If feasible bug, bail out now */
404 switch_to_master(NULL);
407 /** @return True, if any bugs have been reported for this execution */
408 bool ModelChecker::have_bug_reports() const
410 return priv->bugs.size() != 0;
413 /** @brief Print bug report listing for this execution (if any bugs exist) */
414 void ModelChecker::print_bugs() const
416 if (have_bug_reports()) {
417 model_print("Bug report: %zu bug%s detected\n",
419 priv->bugs.size() > 1 ? "s" : "");
420 for (unsigned int i = 0; i < priv->bugs.size(); i++)
421 priv->bugs[i]->print();
426 * @brief Record end-of-execution stats
428 * Must be run when exiting an execution. Records various stats.
429 * @see struct execution_stats
431 void ModelChecker::record_stats()
434 if (!isfeasibleprefix())
435 stats.num_infeasible++;
436 else if (have_bug_reports())
437 stats.num_buggy_executions++;
438 else if (is_complete_execution())
439 stats.num_complete++;
441 stats.num_redundant++;
444 /** @brief Print execution stats */
445 void ModelChecker::print_stats() const
447 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
448 model_print("Number of redundant executions: %d\n", stats.num_redundant);
449 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
450 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
451 model_print("Total executions: %d\n", stats.num_total);
452 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
456 * @brief End-of-exeuction print
457 * @param printbugs Should any existing bugs be printed?
459 void ModelChecker::print_execution(bool printbugs) const
461 print_program_output();
463 if (DBG_ENABLED() || params.verbose) {
464 model_print("Earliest divergence point since last feasible execution:\n");
465 if (earliest_diverge)
466 earliest_diverge->print();
468 model_print("(Not set)\n");
474 /* Don't print invalid bugs */
483 * Queries the model-checker for more executions to explore and, if one
484 * exists, resets the model-checker state to execute a new execution.
486 * @return If there are more executions to explore, return true. Otherwise,
489 bool ModelChecker::next_execution()
492 /* Is this execution a feasible execution that's worth bug-checking? */
493 bool complete = isfeasibleprefix() && (is_complete_execution() ||
496 /* End-of-execution bug checks */
499 assert_bug("Deadlock detected");
507 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
508 print_execution(complete);
510 clear_program_output();
513 earliest_diverge = NULL;
515 if ((diverge = get_next_backtrack()) == NULL)
519 model_print("Next execution will diverge at:\n");
523 reset_to_initial_state();
527 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
529 switch (act->get_type()) {
534 /* Optimization: relaxed operations don't need backtracking */
535 if (act->is_relaxed())
537 /* linear search: from most recent to oldest */
538 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
539 action_list_t::reverse_iterator rit;
540 for (rit = list->rbegin(); rit != list->rend(); rit++) {
541 ModelAction *prev = *rit;
542 if (prev->could_synchronize_with(act))
548 case ATOMIC_TRYLOCK: {
549 /* linear search: from most recent to oldest */
550 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
551 action_list_t::reverse_iterator rit;
552 for (rit = list->rbegin(); rit != list->rend(); rit++) {
553 ModelAction *prev = *rit;
554 if (act->is_conflicting_lock(prev))
559 case ATOMIC_UNLOCK: {
560 /* linear search: from most recent to oldest */
561 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
562 action_list_t::reverse_iterator rit;
563 for (rit = list->rbegin(); rit != list->rend(); rit++) {
564 ModelAction *prev = *rit;
565 if (!act->same_thread(prev) && prev->is_failed_trylock())
571 /* linear search: from most recent to oldest */
572 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
573 action_list_t::reverse_iterator rit;
574 for (rit = list->rbegin(); rit != list->rend(); rit++) {
575 ModelAction *prev = *rit;
576 if (!act->same_thread(prev) && prev->is_failed_trylock())
578 if (!act->same_thread(prev) && prev->is_notify())
584 case ATOMIC_NOTIFY_ALL:
585 case ATOMIC_NOTIFY_ONE: {
586 /* linear search: from most recent to oldest */
587 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
588 action_list_t::reverse_iterator rit;
589 for (rit = list->rbegin(); rit != list->rend(); rit++) {
590 ModelAction *prev = *rit;
591 if (!act->same_thread(prev) && prev->is_wait())
602 /** This method finds backtracking points where we should try to
603 * reorder the parameter ModelAction against.
605 * @param the ModelAction to find backtracking points for.
607 void ModelChecker::set_backtracking(ModelAction *act)
609 Thread *t = get_thread(act);
610 ModelAction *prev = get_last_conflict(act);
614 Node *node = prev->get_node()->get_parent();
616 int low_tid, high_tid;
617 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
618 low_tid = id_to_int(act->get_tid());
619 high_tid = low_tid + 1;
622 high_tid = get_num_threads();
625 for (int i = low_tid; i < high_tid; i++) {
626 thread_id_t tid = int_to_id(i);
628 /* Make sure this thread can be enabled here. */
629 if (i >= node->get_num_threads())
632 /* Don't backtrack into a point where the thread is disabled or sleeping. */
633 if (node->enabled_status(tid) != THREAD_ENABLED)
636 /* Check if this has been explored already */
637 if (node->has_been_explored(tid))
640 /* See if fairness allows */
641 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
643 for (int t = 0; t < node->get_num_threads(); t++) {
644 thread_id_t tother = int_to_id(t);
645 if (node->is_enabled(tother) && node->has_priority(tother)) {
653 /* Cache the latest backtracking point */
654 set_latest_backtrack(prev);
656 /* If this is a new backtracking point, mark the tree */
657 if (!node->set_backtrack(tid))
659 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
660 id_to_int(prev->get_tid()),
661 id_to_int(t->get_id()));
670 * @brief Cache the a backtracking point as the "most recent", if eligible
672 * Note that this does not prepare the NodeStack for this backtracking
673 * operation, it only caches the action on a per-execution basis
675 * @param act The operation at which we should explore a different next action
676 * (i.e., backtracking point)
677 * @return True, if this action is now the most recent backtracking point;
680 bool ModelChecker::set_latest_backtrack(ModelAction *act)
682 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
683 priv->next_backtrack = act;
690 * Returns last backtracking point. The model checker will explore a different
691 * path for this point in the next execution.
692 * @return The ModelAction at which the next execution should diverge.
694 ModelAction * ModelChecker::get_next_backtrack()
696 ModelAction *next = priv->next_backtrack;
697 priv->next_backtrack = NULL;
702 * Processes a read or rmw model action.
703 * @param curr is the read model action to process.
704 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
705 * @return True if processing this read updates the mo_graph.
707 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
709 uint64_t value = VALUE_NONE;
710 bool updated = false;
712 const ModelAction *reads_from = curr->get_node()->get_read_from();
713 if (reads_from != NULL) {
714 mo_graph->startChanges();
716 value = reads_from->get_value();
717 bool r_status = false;
719 if (!second_part_of_rmw) {
720 check_recency(curr, reads_from);
721 r_status = r_modification_order(curr, reads_from);
725 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
726 mo_graph->rollbackChanges();
727 priv->too_many_reads = false;
731 read_from(curr, reads_from);
732 mo_graph->commitChanges();
733 mo_check_promises(curr->get_tid(), reads_from, NULL);
736 } else if (!second_part_of_rmw) {
737 /* Read from future value */
738 struct future_value fv = curr->get_node()->get_future_value();
740 curr->set_read_from(NULL);
741 promises->push_back(new Promise(curr, fv));
743 get_thread(curr)->set_return_value(value);
749 * Processes a lock, trylock, or unlock model action. @param curr is
750 * the read model action to process.
752 * The try lock operation checks whether the lock is taken. If not,
753 * it falls to the normal lock operation case. If so, it returns
756 * The lock operation has already been checked that it is enabled, so
757 * it just grabs the lock and synchronizes with the previous unlock.
759 * The unlock operation has to re-enable all of the threads that are
760 * waiting on the lock.
762 * @return True if synchronization was updated; false otherwise
764 bool ModelChecker::process_mutex(ModelAction *curr)
766 std::mutex *mutex = NULL;
767 struct std::mutex_state *state = NULL;
769 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
770 mutex = (std::mutex *)curr->get_location();
771 state = mutex->get_state();
772 } else if (curr->is_wait()) {
773 mutex = (std::mutex *)curr->get_value();
774 state = mutex->get_state();
777 switch (curr->get_type()) {
778 case ATOMIC_TRYLOCK: {
779 bool success = !state->islocked;
780 curr->set_try_lock(success);
782 get_thread(curr)->set_return_value(0);
785 get_thread(curr)->set_return_value(1);
787 //otherwise fall into the lock case
789 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
790 assert_bug("Lock access before initialization");
791 state->islocked = true;
792 ModelAction *unlock = get_last_unlock(curr);
793 //synchronize with the previous unlock statement
794 if (unlock != NULL) {
795 curr->synchronize_with(unlock);
800 case ATOMIC_UNLOCK: {
802 state->islocked = false;
803 //wake up the other threads
804 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
805 //activate all the waiting threads
806 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
807 scheduler->wake(get_thread(*rit));
814 state->islocked = false;
815 //wake up the other threads
816 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
817 //activate all the waiting threads
818 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
819 scheduler->wake(get_thread(*rit));
822 //check whether we should go to sleep or not...simulate spurious failures
823 if (curr->get_node()->get_misc() == 0) {
824 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
826 scheduler->sleep(get_thread(curr));
830 case ATOMIC_NOTIFY_ALL: {
831 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
832 //activate all the waiting threads
833 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
834 scheduler->wake(get_thread(*rit));
839 case ATOMIC_NOTIFY_ONE: {
840 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
841 int wakeupthread = curr->get_node()->get_misc();
842 action_list_t::iterator it = waiters->begin();
843 advance(it, wakeupthread);
844 scheduler->wake(get_thread(*it));
855 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
857 /* Do more ambitious checks now that mo is more complete */
858 if (mo_may_allow(writer, reader) &&
859 reader->get_node()->add_future_value(writer,
860 writer->get_seq_number() + params.maxfuturedelay))
861 set_latest_backtrack(reader);
865 * Process a write ModelAction
866 * @param curr The ModelAction to process
867 * @return True if the mo_graph was updated or promises were resolved
869 bool ModelChecker::process_write(ModelAction *curr)
871 bool updated_mod_order = w_modification_order(curr);
872 bool updated_promises = resolve_promises(curr);
874 if (promises->size() == 0) {
875 for (unsigned int i = 0; i < futurevalues->size(); i++) {
876 struct PendingFutureValue pfv = (*futurevalues)[i];
877 add_future_value(pfv.writer, pfv.act);
879 futurevalues->clear();
882 mo_graph->commitChanges();
883 mo_check_promises(curr->get_tid(), curr, NULL);
885 get_thread(curr)->set_return_value(VALUE_NONE);
886 return updated_mod_order || updated_promises;
890 * Process a fence ModelAction
891 * @param curr The ModelAction to process
892 * @return True if synchronization was updated
894 bool ModelChecker::process_fence(ModelAction *curr)
897 * fence-relaxed: no-op
898 * fence-release: only log the occurence (not in this function), for
899 * use in later synchronization
900 * fence-acquire (this function): search for hypothetical release
903 bool updated = false;
904 if (curr->is_acquire()) {
905 action_list_t *list = action_trace;
906 action_list_t::reverse_iterator rit;
907 /* Find X : is_read(X) && X --sb-> curr */
908 for (rit = list->rbegin(); rit != list->rend(); rit++) {
909 ModelAction *act = *rit;
912 if (act->get_tid() != curr->get_tid())
914 /* Stop at the beginning of the thread */
915 if (act->is_thread_start())
917 /* Stop once we reach a prior fence-acquire */
918 if (act->is_fence() && act->is_acquire())
922 /* read-acquire will find its own release sequences */
923 if (act->is_acquire())
926 /* Establish hypothetical release sequences */
927 rel_heads_list_t release_heads;
928 get_release_seq_heads(curr, act, &release_heads);
929 for (unsigned int i = 0; i < release_heads.size(); i++)
930 if (!curr->synchronize_with(release_heads[i]))
931 set_bad_synchronization();
932 if (release_heads.size() != 0)
940 * @brief Process the current action for thread-related activity
942 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
943 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
944 * synchronization, etc. This function is a no-op for non-THREAD actions
945 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
947 * @param curr The current action
948 * @return True if synchronization was updated or a thread completed
950 bool ModelChecker::process_thread_action(ModelAction *curr)
952 bool updated = false;
954 switch (curr->get_type()) {
955 case THREAD_CREATE: {
956 Thread *th = curr->get_thread_operand();
957 th->set_creation(curr);
961 Thread *blocking = curr->get_thread_operand();
962 ModelAction *act = get_last_action(blocking->get_id());
963 curr->synchronize_with(act);
964 updated = true; /* trigger rel-seq checks */
967 case THREAD_FINISH: {
968 Thread *th = get_thread(curr);
969 while (!th->wait_list_empty()) {
970 ModelAction *act = th->pop_wait_list();
971 scheduler->wake(get_thread(act));
974 updated = true; /* trigger rel-seq checks */
978 check_promises(curr->get_tid(), NULL, curr->get_cv());
989 * @brief Process the current action for release sequence fixup activity
991 * Performs model-checker release sequence fixups for the current action,
992 * forcing a single pending release sequence to break (with a given, potential
993 * "loose" write) or to complete (i.e., synchronize). If a pending release
994 * sequence forms a complete release sequence, then we must perform the fixup
995 * synchronization, mo_graph additions, etc.
997 * @param curr The current action; must be a release sequence fixup action
998 * @param work_queue The work queue to which to add work items as they are
1001 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1003 const ModelAction *write = curr->get_node()->get_relseq_break();
1004 struct release_seq *sequence = pending_rel_seqs->back();
1005 pending_rel_seqs->pop_back();
1007 ModelAction *acquire = sequence->acquire;
1008 const ModelAction *rf = sequence->rf;
1009 const ModelAction *release = sequence->release;
1013 ASSERT(release->same_thread(rf));
1015 if (write == NULL) {
1017 * @todo Forcing a synchronization requires that we set
1018 * modification order constraints. For instance, we can't allow
1019 * a fixup sequence in which two separate read-acquire
1020 * operations read from the same sequence, where the first one
1021 * synchronizes and the other doesn't. Essentially, we can't
1022 * allow any writes to insert themselves between 'release' and
1026 /* Must synchronize */
1027 if (!acquire->synchronize_with(release)) {
1028 set_bad_synchronization();
1031 /* Re-check all pending release sequences */
1032 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1033 /* Re-check act for mo_graph edges */
1034 work_queue->push_back(MOEdgeWorkEntry(acquire));
1036 /* propagate synchronization to later actions */
1037 action_list_t::reverse_iterator rit = action_trace->rbegin();
1038 for (; (*rit) != acquire; rit++) {
1039 ModelAction *propagate = *rit;
1040 if (acquire->happens_before(propagate)) {
1041 propagate->synchronize_with(acquire);
1042 /* Re-check 'propagate' for mo_graph edges */
1043 work_queue->push_back(MOEdgeWorkEntry(propagate));
1047 /* Break release sequence with new edges:
1048 * release --mo--> write --mo--> rf */
1049 mo_graph->addEdge(release, write);
1050 mo_graph->addEdge(write, rf);
1053 /* See if we have realized a data race */
1058 * Initialize the current action by performing one or more of the following
1059 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1060 * in the NodeStack, manipulating backtracking sets, allocating and
1061 * initializing clock vectors, and computing the promises to fulfill.
1063 * @param curr The current action, as passed from the user context; may be
1064 * freed/invalidated after the execution of this function, with a different
1065 * action "returned" its place (pass-by-reference)
1066 * @return True if curr is a newly-explored action; false otherwise
1068 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1070 ModelAction *newcurr;
1072 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1073 newcurr = process_rmw(*curr);
1076 if (newcurr->is_rmw())
1077 compute_promises(newcurr);
1083 (*curr)->set_seq_number(get_next_seq_num());
1085 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1087 /* First restore type and order in case of RMW operation */
1088 if ((*curr)->is_rmwr())
1089 newcurr->copy_typeandorder(*curr);
1091 ASSERT((*curr)->get_location() == newcurr->get_location());
1092 newcurr->copy_from_new(*curr);
1094 /* Discard duplicate ModelAction; use action from NodeStack */
1097 /* Always compute new clock vector */
1098 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1101 return false; /* Action was explored previously */
1105 /* Always compute new clock vector */
1106 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1108 /* Assign most recent release fence */
1109 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1112 * Perform one-time actions when pushing new ModelAction onto
1115 if (newcurr->is_write())
1116 compute_promises(newcurr);
1117 else if (newcurr->is_relseq_fixup())
1118 compute_relseq_breakwrites(newcurr);
1119 else if (newcurr->is_wait())
1120 newcurr->get_node()->set_misc_max(2);
1121 else if (newcurr->is_notify_one()) {
1122 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1124 return true; /* This was a new ModelAction */
1129 * @brief Establish reads-from relation between two actions
1131 * Perform basic operations involved with establishing a concrete rf relation,
1132 * including setting the ModelAction data and checking for release sequences.
1134 * @param act The action that is reading (must be a read)
1135 * @param rf The action from which we are reading (must be a write)
1137 * @return True if this read established synchronization
1139 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1141 act->set_read_from(rf);
1142 if (rf != NULL && act->is_acquire()) {
1143 rel_heads_list_t release_heads;
1144 get_release_seq_heads(act, act, &release_heads);
1145 int num_heads = release_heads.size();
1146 for (unsigned int i = 0; i < release_heads.size(); i++)
1147 if (!act->synchronize_with(release_heads[i])) {
1148 set_bad_synchronization();
1151 return num_heads > 0;
1157 * @brief Check whether a model action is enabled.
1159 * Checks whether a lock or join operation would be successful (i.e., is the
1160 * lock already locked, or is the joined thread already complete). If not, put
1161 * the action in a waiter list.
1163 * @param curr is the ModelAction to check whether it is enabled.
1164 * @return a bool that indicates whether the action is enabled.
1166 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1167 if (curr->is_lock()) {
1168 std::mutex *lock = (std::mutex *)curr->get_location();
1169 struct std::mutex_state *state = lock->get_state();
1170 if (state->islocked) {
1171 //Stick the action in the appropriate waiting queue
1172 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1175 } else if (curr->get_type() == THREAD_JOIN) {
1176 Thread *blocking = (Thread *)curr->get_location();
1177 if (!blocking->is_complete()) {
1178 blocking->push_wait_list(curr);
1187 * Stores the ModelAction for the current thread action. Call this
1188 * immediately before switching from user- to system-context to pass
1189 * data between them.
1190 * @param act The ModelAction created by the user-thread action
1192 void ModelChecker::set_current_action(ModelAction *act) {
1193 priv->current_action = act;
1197 * This is the heart of the model checker routine. It performs model-checking
1198 * actions corresponding to a given "current action." Among other processes, it
1199 * calculates reads-from relationships, updates synchronization clock vectors,
1200 * forms a memory_order constraints graph, and handles replay/backtrack
1201 * execution when running permutations of previously-observed executions.
1203 * @param curr The current action to process
1204 * @return The ModelAction that is actually executed; may be different than
1205 * curr; may be NULL, if the current action is not enabled to run
1207 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1210 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1212 if (!check_action_enabled(curr)) {
1213 /* Make the execution look like we chose to run this action
1214 * much later, when a lock/join can succeed */
1215 get_thread(curr)->set_pending(curr);
1216 scheduler->sleep(get_thread(curr));
1220 bool newly_explored = initialize_curr_action(&curr);
1226 wake_up_sleeping_actions(curr);
1228 /* Add the action to lists before any other model-checking tasks */
1229 if (!second_part_of_rmw)
1230 add_action_to_lists(curr);
1232 /* Build may_read_from set for newly-created actions */
1233 if (newly_explored && curr->is_read())
1234 build_reads_from_past(curr);
1236 /* Initialize work_queue with the "current action" work */
1237 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1238 while (!work_queue.empty() && !has_asserted()) {
1239 WorkQueueEntry work = work_queue.front();
1240 work_queue.pop_front();
1242 switch (work.type) {
1243 case WORK_CHECK_CURR_ACTION: {
1244 ModelAction *act = work.action;
1245 bool update = false; /* update this location's release seq's */
1246 bool update_all = false; /* update all release seq's */
1248 if (process_thread_action(curr))
1251 if (act->is_read() && process_read(act, second_part_of_rmw))
1254 if (act->is_write() && process_write(act))
1257 if (act->is_fence() && process_fence(act))
1260 if (act->is_mutex_op() && process_mutex(act))
1263 if (act->is_relseq_fixup())
1264 process_relseq_fixup(curr, &work_queue);
1267 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1269 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1272 case WORK_CHECK_RELEASE_SEQ:
1273 resolve_release_sequences(work.location, &work_queue);
1275 case WORK_CHECK_MO_EDGES: {
1276 /** @todo Complete verification of work_queue */
1277 ModelAction *act = work.action;
1278 bool updated = false;
1280 if (act->is_read()) {
1281 const ModelAction *rf = act->get_reads_from();
1282 if (rf != NULL && r_modification_order(act, rf))
1285 if (act->is_write()) {
1286 if (w_modification_order(act))
1289 mo_graph->commitChanges();
1292 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1301 check_curr_backtracking(curr);
1302 set_backtracking(curr);
1306 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1308 Node *currnode = curr->get_node();
1309 Node *parnode = currnode->get_parent();
1311 if ((parnode && !parnode->backtrack_empty()) ||
1312 !currnode->misc_empty() ||
1313 !currnode->read_from_empty() ||
1314 !currnode->future_value_empty() ||
1315 !currnode->promise_empty() ||
1316 !currnode->relseq_break_empty()) {
1317 set_latest_backtrack(curr);
1321 bool ModelChecker::promises_expired() const
1323 for (unsigned int i = 0; i < promises->size(); i++) {
1324 Promise *promise = (*promises)[i];
1325 if (promise->get_expiration() < priv->used_sequence_numbers)
1332 * This is the strongest feasibility check available.
1333 * @return whether the current trace (partial or complete) must be a prefix of
1336 bool ModelChecker::isfeasibleprefix() const
1338 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1342 * Print disagnostic information about an infeasible execution
1343 * @param prefix A string to prefix the output with; if NULL, then a default
1344 * message prefix will be provided
1346 void ModelChecker::print_infeasibility(const char *prefix) const
1350 if (mo_graph->checkForRMWViolation())
1351 ptr += sprintf(ptr, "[RMW atomicity]");
1352 if (mo_graph->checkForCycles())
1353 ptr += sprintf(ptr, "[mo cycle]");
1354 if (priv->failed_promise)
1355 ptr += sprintf(ptr, "[failed promise]");
1356 if (priv->too_many_reads)
1357 ptr += sprintf(ptr, "[too many reads]");
1358 if (priv->bad_synchronization)
1359 ptr += sprintf(ptr, "[bad sw ordering]");
1360 if (promises_expired())
1361 ptr += sprintf(ptr, "[promise expired]");
1362 if (promises->size() != 0)
1363 ptr += sprintf(ptr, "[unresolved promise]");
1365 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1369 * Returns whether the current completed trace is feasible, except for pending
1370 * release sequences.
1372 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1374 return !is_infeasible() && promises->size() == 0;
1378 * Check if the current partial trace is infeasible. Does not check any
1379 * end-of-execution flags, which might rule out the execution. Thus, this is
1380 * useful only for ruling an execution as infeasible.
1381 * @return whether the current partial trace is infeasible.
1383 bool ModelChecker::is_infeasible() const
1385 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1389 * Check If the current partial trace is infeasible, while ignoring
1390 * infeasibility related to 2 RMW's reading from the same store. It does not
1391 * check end-of-execution feasibility.
1392 * @see ModelChecker::is_infeasible
1393 * @return whether the current partial trace is infeasible, ignoring multiple
1394 * RMWs reading from the same store.
1396 bool ModelChecker::is_infeasible_ignoreRMW() const
1398 return mo_graph->checkForCycles() || priv->failed_promise ||
1399 priv->too_many_reads || priv->bad_synchronization ||
1403 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1404 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1405 ModelAction *lastread = get_last_action(act->get_tid());
1406 lastread->process_rmw(act);
1407 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1408 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1409 mo_graph->commitChanges();
1415 * Checks whether a thread has read from the same write for too many times
1416 * without seeing the effects of a later write.
1419 * 1) there must a different write that we could read from that would satisfy the modification order,
1420 * 2) we must have read from the same value in excess of maxreads times, and
1421 * 3) that other write must have been in the reads_from set for maxreads times.
1423 * If so, we decide that the execution is no longer feasible.
1425 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1427 if (params.maxreads != 0) {
1428 if (curr->get_node()->get_read_from_size() <= 1)
1430 //Must make sure that execution is currently feasible... We could
1431 //accidentally clear by rolling back
1432 if (is_infeasible())
1434 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1435 int tid = id_to_int(curr->get_tid());
1438 if ((int)thrd_lists->size() <= tid)
1440 action_list_t *list = &(*thrd_lists)[tid];
1442 action_list_t::reverse_iterator rit = list->rbegin();
1443 /* Skip past curr */
1444 for (; (*rit) != curr; rit++)
1446 /* go past curr now */
1449 action_list_t::reverse_iterator ritcopy = rit;
1450 //See if we have enough reads from the same value
1452 for (; count < params.maxreads; rit++, count++) {
1453 if (rit == list->rend())
1455 ModelAction *act = *rit;
1456 if (!act->is_read())
1459 if (act->get_reads_from() != rf)
1461 if (act->get_node()->get_read_from_size() <= 1)
1464 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1466 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1468 /* Need a different write */
1472 /* Test to see whether this is a feasible write to read from */
1473 mo_graph->startChanges();
1474 r_modification_order(curr, write);
1475 bool feasiblereadfrom = !is_infeasible();
1476 mo_graph->rollbackChanges();
1478 if (!feasiblereadfrom)
1482 bool feasiblewrite = true;
1483 //new we need to see if this write works for everyone
1485 for (int loop = count; loop > 0; loop--, rit++) {
1486 ModelAction *act = *rit;
1487 bool foundvalue = false;
1488 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1489 if (act->get_node()->get_read_from_at(j) == write) {
1495 feasiblewrite = false;
1499 if (feasiblewrite) {
1500 priv->too_many_reads = true;
1508 * Updates the mo_graph with the constraints imposed from the current
1511 * Basic idea is the following: Go through each other thread and find
1512 * the lastest action that happened before our read. Two cases:
1514 * (1) The action is a write => that write must either occur before
1515 * the write we read from or be the write we read from.
1517 * (2) The action is a read => the write that that action read from
1518 * must occur before the write we read from or be the same write.
1520 * @param curr The current action. Must be a read.
1521 * @param rf The action that curr reads from. Must be a write.
1522 * @return True if modification order edges were added; false otherwise
1524 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1526 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1529 ASSERT(curr->is_read());
1531 /* Last SC fence in the current thread */
1532 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1534 /* Iterate over all threads */
1535 for (i = 0; i < thrd_lists->size(); i++) {
1536 /* Last SC fence in thread i */
1537 ModelAction *last_sc_fence_thread_local = NULL;
1538 if (int_to_id((int)i) != curr->get_tid())
1539 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1541 /* Last SC fence in thread i, before last SC fence in current thread */
1542 ModelAction *last_sc_fence_thread_before = NULL;
1543 if (last_sc_fence_local)
1544 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1546 /* Iterate over actions in thread, starting from most recent */
1547 action_list_t *list = &(*thrd_lists)[i];
1548 action_list_t::reverse_iterator rit;
1549 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1550 ModelAction *act = *rit;
1552 if (act->is_write() && act != rf && act != curr) {
1553 /* C++, Section 29.3 statement 5 */
1554 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1555 *act < *last_sc_fence_thread_local) {
1556 mo_graph->addEdge(act, rf);
1560 /* C++, Section 29.3 statement 4 */
1561 else if (act->is_seqcst() && last_sc_fence_local &&
1562 *act < *last_sc_fence_local) {
1563 mo_graph->addEdge(act, rf);
1567 /* C++, Section 29.3 statement 6 */
1568 else if (last_sc_fence_thread_before &&
1569 *act < *last_sc_fence_thread_before) {
1570 mo_graph->addEdge(act, rf);
1577 * Include at most one act per-thread that "happens
1578 * before" curr. Don't consider reflexively.
1580 if (act->happens_before(curr) && act != curr) {
1581 if (act->is_write()) {
1583 mo_graph->addEdge(act, rf);
1587 const ModelAction *prevreadfrom = act->get_reads_from();
1588 //if the previous read is unresolved, keep going...
1589 if (prevreadfrom == NULL)
1592 if (rf != prevreadfrom) {
1593 mo_graph->addEdge(prevreadfrom, rf);
1605 /** This method fixes up the modification order when we resolve a
1606 * promises. The basic problem is that actions that occur after the
1607 * read curr could not property add items to the modification order
1610 * So for each thread, we find the earliest item that happens after
1611 * the read curr. This is the item we have to fix up with additional
1612 * constraints. If that action is write, we add a MO edge between
1613 * the Action rf and that action. If the action is a read, we add a
1614 * MO edge between the Action rf, and whatever the read accessed.
1616 * @param curr is the read ModelAction that we are fixing up MO edges for.
1617 * @param rf is the write ModelAction that curr reads from.
1620 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1622 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1624 ASSERT(curr->is_read());
1626 /* Iterate over all threads */
1627 for (i = 0; i < thrd_lists->size(); i++) {
1628 /* Iterate over actions in thread, starting from most recent */
1629 action_list_t *list = &(*thrd_lists)[i];
1630 action_list_t::reverse_iterator rit;
1631 ModelAction *lastact = NULL;
1633 /* Find last action that happens after curr that is either not curr or a rmw */
1634 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1635 ModelAction *act = *rit;
1636 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1642 /* Include at most one act per-thread that "happens before" curr */
1643 if (lastact != NULL) {
1644 if (lastact == curr) {
1645 //Case 1: The resolved read is a RMW, and we need to make sure
1646 //that the write portion of the RMW mod order after rf
1648 mo_graph->addEdge(rf, lastact);
1649 } else if (lastact->is_read()) {
1650 //Case 2: The resolved read is a normal read and the next
1651 //operation is a read, and we need to make sure the value read
1652 //is mod ordered after rf
1654 const ModelAction *postreadfrom = lastact->get_reads_from();
1655 if (postreadfrom != NULL && rf != postreadfrom)
1656 mo_graph->addEdge(rf, postreadfrom);
1658 //Case 3: The resolved read is a normal read and the next
1659 //operation is a write, and we need to make sure that the
1660 //write is mod ordered after rf
1662 mo_graph->addEdge(rf, lastact);
1670 * Updates the mo_graph with the constraints imposed from the current write.
1672 * Basic idea is the following: Go through each other thread and find
1673 * the lastest action that happened before our write. Two cases:
1675 * (1) The action is a write => that write must occur before
1678 * (2) The action is a read => the write that that action read from
1679 * must occur before the current write.
1681 * This method also handles two other issues:
1683 * (I) Sequential Consistency: Making sure that if the current write is
1684 * seq_cst, that it occurs after the previous seq_cst write.
1686 * (II) Sending the write back to non-synchronizing reads.
1688 * @param curr The current action. Must be a write.
1689 * @return True if modification order edges were added; false otherwise
1691 bool ModelChecker::w_modification_order(ModelAction *curr)
1693 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1696 ASSERT(curr->is_write());
1698 if (curr->is_seqcst()) {
1699 /* We have to at least see the last sequentially consistent write,
1700 so we are initialized. */
1701 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1702 if (last_seq_cst != NULL) {
1703 mo_graph->addEdge(last_seq_cst, curr);
1708 /* Last SC fence in the current thread */
1709 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1711 /* Iterate over all threads */
1712 for (i = 0; i < thrd_lists->size(); i++) {
1713 /* Last SC fence in thread i, before last SC fence in current thread */
1714 ModelAction *last_sc_fence_thread_before = NULL;
1715 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1716 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1718 /* Iterate over actions in thread, starting from most recent */
1719 action_list_t *list = &(*thrd_lists)[i];
1720 action_list_t::reverse_iterator rit;
1721 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1722 ModelAction *act = *rit;
1725 * 1) If RMW and it actually read from something, then we
1726 * already have all relevant edges, so just skip to next
1729 * 2) If RMW and it didn't read from anything, we should
1730 * whatever edge we can get to speed up convergence.
1732 * 3) If normal write, we need to look at earlier actions, so
1733 * continue processing list.
1735 if (curr->is_rmw()) {
1736 if (curr->get_reads_from() != NULL)
1744 /* C++, Section 29.3 statement 7 */
1745 if (last_sc_fence_thread_before && act->is_write() &&
1746 *act < *last_sc_fence_thread_before) {
1747 mo_graph->addEdge(act, curr);
1753 * Include at most one act per-thread that "happens
1756 if (act->happens_before(curr)) {
1758 * Note: if act is RMW, just add edge:
1760 * The following edge should be handled elsewhere:
1761 * readfrom(act) --mo--> act
1763 if (act->is_write())
1764 mo_graph->addEdge(act, curr);
1765 else if (act->is_read()) {
1766 //if previous read accessed a null, just keep going
1767 if (act->get_reads_from() == NULL)
1769 mo_graph->addEdge(act->get_reads_from(), curr);
1773 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1774 !act->same_thread(curr)) {
1775 /* We have an action that:
1776 (1) did not happen before us
1777 (2) is a read and we are a write
1778 (3) cannot synchronize with us
1779 (4) is in a different thread
1781 that read could potentially read from our write. Note that
1782 these checks are overly conservative at this point, we'll
1783 do more checks before actually removing the
1787 if (thin_air_constraint_may_allow(curr, act)) {
1788 if (!is_infeasible() ||
1789 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1790 futurevalues->push_back(PendingFutureValue(curr, act));
1800 /** Arbitrary reads from the future are not allowed. Section 29.3
1801 * part 9 places some constraints. This method checks one result of constraint
1802 * constraint. Others require compiler support. */
1803 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1805 if (!writer->is_rmw())
1808 if (!reader->is_rmw())
1811 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1812 if (search == reader)
1814 if (search->get_tid() == reader->get_tid() &&
1815 search->happens_before(reader))
1823 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1824 * some constraints. This method checks one the following constraint (others
1825 * require compiler support):
1827 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1829 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1831 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1833 /* Iterate over all threads */
1834 for (i = 0; i < thrd_lists->size(); i++) {
1835 const ModelAction *write_after_read = NULL;
1837 /* Iterate over actions in thread, starting from most recent */
1838 action_list_t *list = &(*thrd_lists)[i];
1839 action_list_t::reverse_iterator rit;
1840 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1841 ModelAction *act = *rit;
1843 /* Don't disallow due to act == reader */
1844 if (!reader->happens_before(act) || reader == act)
1846 else if (act->is_write())
1847 write_after_read = act;
1848 else if (act->is_read() && act->get_reads_from() != NULL)
1849 write_after_read = act->get_reads_from();
1852 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1859 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1860 * The ModelAction under consideration is expected to be taking part in
1861 * release/acquire synchronization as an object of the "reads from" relation.
1862 * Note that this can only provide release sequence support for RMW chains
1863 * which do not read from the future, as those actions cannot be traced until
1864 * their "promise" is fulfilled. Similarly, we may not even establish the
1865 * presence of a release sequence with certainty, as some modification order
1866 * constraints may be decided further in the future. Thus, this function
1867 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1868 * and a boolean representing certainty.
1870 * @param rf The action that might be part of a release sequence. Must be a
1872 * @param release_heads A pass-by-reference style return parameter. After
1873 * execution of this function, release_heads will contain the heads of all the
1874 * relevant release sequences, if any exists with certainty
1875 * @param pending A pass-by-reference style return parameter which is only used
1876 * when returning false (i.e., uncertain). Returns most information regarding
1877 * an uncertain release sequence, including any write operations that might
1878 * break the sequence.
1879 * @return true, if the ModelChecker is certain that release_heads is complete;
1882 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1883 rel_heads_list_t *release_heads,
1884 struct release_seq *pending) const
1886 /* Only check for release sequences if there are no cycles */
1887 if (mo_graph->checkForCycles())
1891 ASSERT(rf->is_write());
1893 if (rf->is_release())
1894 release_heads->push_back(rf);
1895 else if (rf->get_last_fence_release())
1896 release_heads->push_back(rf->get_last_fence_release());
1898 break; /* End of RMW chain */
1900 /** @todo Need to be smarter here... In the linux lock
1901 * example, this will run to the beginning of the program for
1903 /** @todo The way to be smarter here is to keep going until 1
1904 * thread has a release preceded by an acquire and you've seen
1907 /* acq_rel RMW is a sufficient stopping condition */
1908 if (rf->is_acquire() && rf->is_release())
1909 return true; /* complete */
1911 rf = rf->get_reads_from();
1914 /* read from future: need to settle this later */
1916 return false; /* incomplete */
1919 if (rf->is_release())
1920 return true; /* complete */
1922 /* else relaxed write
1923 * - check for fence-release in the same thread (29.8, stmt. 3)
1924 * - check modification order for contiguous subsequence
1925 * -> rf must be same thread as release */
1927 const ModelAction *fence_release = rf->get_last_fence_release();
1928 /* Synchronize with a fence-release unconditionally; we don't need to
1929 * find any more "contiguous subsequence..." for it */
1931 release_heads->push_back(fence_release);
1933 int tid = id_to_int(rf->get_tid());
1934 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1935 action_list_t *list = &(*thrd_lists)[tid];
1936 action_list_t::const_reverse_iterator rit;
1938 /* Find rf in the thread list */
1939 rit = std::find(list->rbegin(), list->rend(), rf);
1940 ASSERT(rit != list->rend());
1942 /* Find the last {write,fence}-release */
1943 for (; rit != list->rend(); rit++) {
1944 if (fence_release && *(*rit) < *fence_release)
1946 if ((*rit)->is_release())
1949 if (rit == list->rend()) {
1950 /* No write-release in this thread */
1951 return true; /* complete */
1952 } else if (fence_release && *(*rit) < *fence_release) {
1953 /* The fence-release is more recent (and so, "stronger") than
1954 * the most recent write-release */
1955 return true; /* complete */
1956 } /* else, need to establish contiguous release sequence */
1957 ModelAction *release = *rit;
1959 ASSERT(rf->same_thread(release));
1961 pending->writes.clear();
1963 bool certain = true;
1964 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1965 if (id_to_int(rf->get_tid()) == (int)i)
1967 list = &(*thrd_lists)[i];
1969 /* Can we ensure no future writes from this thread may break
1970 * the release seq? */
1971 bool future_ordered = false;
1973 ModelAction *last = get_last_action(int_to_id(i));
1974 Thread *th = get_thread(int_to_id(i));
1975 if ((last && rf->happens_before(last)) ||
1978 future_ordered = true;
1980 ASSERT(!th->is_model_thread() || future_ordered);
1982 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1983 const ModelAction *act = *rit;
1984 /* Reach synchronization -> this thread is complete */
1985 if (act->happens_before(release))
1987 if (rf->happens_before(act)) {
1988 future_ordered = true;
1992 /* Only non-RMW writes can break release sequences */
1993 if (!act->is_write() || act->is_rmw())
1996 /* Check modification order */
1997 if (mo_graph->checkReachable(rf, act)) {
1998 /* rf --mo--> act */
1999 future_ordered = true;
2002 if (mo_graph->checkReachable(act, release))
2003 /* act --mo--> release */
2005 if (mo_graph->checkReachable(release, act) &&
2006 mo_graph->checkReachable(act, rf)) {
2007 /* release --mo-> act --mo--> rf */
2008 return true; /* complete */
2010 /* act may break release sequence */
2011 pending->writes.push_back(act);
2014 if (!future_ordered)
2015 certain = false; /* This thread is uncertain */
2019 release_heads->push_back(release);
2020 pending->writes.clear();
2022 pending->release = release;
2029 * An interface for getting the release sequence head(s) with which a
2030 * given ModelAction must synchronize. This function only returns a non-empty
2031 * result when it can locate a release sequence head with certainty. Otherwise,
2032 * it may mark the internal state of the ModelChecker so that it will handle
2033 * the release sequence at a later time, causing @a acquire to update its
2034 * synchronization at some later point in execution.
2036 * @param acquire The 'acquire' action that may synchronize with a release
2038 * @param read The read action that may read from a release sequence; this may
2039 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2040 * when 'acquire' is a fence-acquire)
2041 * @param release_heads A pass-by-reference return parameter. Will be filled
2042 * with the head(s) of the release sequence(s), if they exists with certainty.
2043 * @see ModelChecker::release_seq_heads
2045 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2046 ModelAction *read, rel_heads_list_t *release_heads)
2048 const ModelAction *rf = read->get_reads_from();
2049 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2050 sequence->acquire = acquire;
2051 sequence->read = read;
2053 if (!release_seq_heads(rf, release_heads, sequence)) {
2054 /* add act to 'lazy checking' list */
2055 pending_rel_seqs->push_back(sequence);
2057 snapshot_free(sequence);
2062 * Attempt to resolve all stashed operations that might synchronize with a
2063 * release sequence for a given location. This implements the "lazy" portion of
2064 * determining whether or not a release sequence was contiguous, since not all
2065 * modification order information is present at the time an action occurs.
2067 * @param location The location/object that should be checked for release
2068 * sequence resolutions. A NULL value means to check all locations.
2069 * @param work_queue The work queue to which to add work items as they are
2071 * @return True if any updates occurred (new synchronization, new mo_graph
2074 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2076 bool updated = false;
2077 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2078 while (it != pending_rel_seqs->end()) {
2079 struct release_seq *pending = *it;
2080 ModelAction *acquire = pending->acquire;
2081 const ModelAction *read = pending->read;
2083 /* Only resolve sequences on the given location, if provided */
2084 if (location && read->get_location() != location) {
2089 const ModelAction *rf = read->get_reads_from();
2090 rel_heads_list_t release_heads;
2092 complete = release_seq_heads(rf, &release_heads, pending);
2093 for (unsigned int i = 0; i < release_heads.size(); i++) {
2094 if (!acquire->has_synchronized_with(release_heads[i])) {
2095 if (acquire->synchronize_with(release_heads[i]))
2098 set_bad_synchronization();
2103 /* Re-check all pending release sequences */
2104 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2105 /* Re-check read-acquire for mo_graph edges */
2106 if (acquire->is_read())
2107 work_queue->push_back(MOEdgeWorkEntry(acquire));
2109 /* propagate synchronization to later actions */
2110 action_list_t::reverse_iterator rit = action_trace->rbegin();
2111 for (; (*rit) != acquire; rit++) {
2112 ModelAction *propagate = *rit;
2113 if (acquire->happens_before(propagate)) {
2114 propagate->synchronize_with(acquire);
2115 /* Re-check 'propagate' for mo_graph edges */
2116 work_queue->push_back(MOEdgeWorkEntry(propagate));
2121 it = pending_rel_seqs->erase(it);
2122 snapshot_free(pending);
2128 // If we resolved promises or data races, see if we have realized a data race.
2135 * Performs various bookkeeping operations for the current ModelAction. For
2136 * instance, adds action to the per-object, per-thread action vector and to the
2137 * action trace list of all thread actions.
2139 * @param act is the ModelAction to add.
2141 void ModelChecker::add_action_to_lists(ModelAction *act)
2143 int tid = id_to_int(act->get_tid());
2144 ModelAction *uninit = NULL;
2146 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2147 if (list->empty() && act->is_atomic_var()) {
2148 uninit = new_uninitialized_action(act->get_location());
2149 uninit_id = id_to_int(uninit->get_tid());
2150 list->push_back(uninit);
2152 list->push_back(act);
2154 action_trace->push_back(act);
2156 action_trace->push_front(uninit);
2158 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2159 if (tid >= (int)vec->size())
2160 vec->resize(priv->next_thread_id);
2161 (*vec)[tid].push_back(act);
2163 (*vec)[uninit_id].push_front(uninit);
2165 if ((int)thrd_last_action->size() <= tid)
2166 thrd_last_action->resize(get_num_threads());
2167 (*thrd_last_action)[tid] = act;
2169 (*thrd_last_action)[uninit_id] = uninit;
2171 if (act->is_fence() && act->is_release()) {
2172 if ((int)thrd_last_fence_release->size() <= tid)
2173 thrd_last_fence_release->resize(get_num_threads());
2174 (*thrd_last_fence_release)[tid] = act;
2177 if (act->is_wait()) {
2178 void *mutex_loc = (void *) act->get_value();
2179 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2181 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2182 if (tid >= (int)vec->size())
2183 vec->resize(priv->next_thread_id);
2184 (*vec)[tid].push_back(act);
2189 * @brief Get the last action performed by a particular Thread
2190 * @param tid The thread ID of the Thread in question
2191 * @return The last action in the thread
2193 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2195 int threadid = id_to_int(tid);
2196 if (threadid < (int)thrd_last_action->size())
2197 return (*thrd_last_action)[id_to_int(tid)];
2203 * @brief Get the last fence release performed by a particular Thread
2204 * @param tid The thread ID of the Thread in question
2205 * @return The last fence release in the thread, if one exists; NULL otherwise
2207 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2209 int threadid = id_to_int(tid);
2210 if (threadid < (int)thrd_last_fence_release->size())
2211 return (*thrd_last_fence_release)[id_to_int(tid)];
2217 * Gets the last memory_order_seq_cst write (in the total global sequence)
2218 * performed on a particular object (i.e., memory location), not including the
2220 * @param curr The current ModelAction; also denotes the object location to
2222 * @return The last seq_cst write
2224 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2226 void *location = curr->get_location();
2227 action_list_t *list = get_safe_ptr_action(obj_map, location);
2228 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2229 action_list_t::reverse_iterator rit;
2230 for (rit = list->rbegin(); rit != list->rend(); rit++)
2231 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2237 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2238 * performed in a particular thread, prior to a particular fence.
2239 * @param tid The ID of the thread to check
2240 * @param before_fence The fence from which to begin the search; if NULL, then
2241 * search for the most recent fence in the thread.
2242 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2244 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2246 /* All fences should have NULL location */
2247 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2248 action_list_t::reverse_iterator rit = list->rbegin();
2251 for (; rit != list->rend(); rit++)
2252 if (*rit == before_fence)
2255 ASSERT(*rit == before_fence);
2259 for (; rit != list->rend(); rit++)
2260 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2266 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2267 * location). This function identifies the mutex according to the current
2268 * action, which is presumed to perform on the same mutex.
2269 * @param curr The current ModelAction; also denotes the object location to
2271 * @return The last unlock operation
2273 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2275 void *location = curr->get_location();
2276 action_list_t *list = get_safe_ptr_action(obj_map, location);
2277 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2278 action_list_t::reverse_iterator rit;
2279 for (rit = list->rbegin(); rit != list->rend(); rit++)
2280 if ((*rit)->is_unlock() || (*rit)->is_wait())
2285 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2287 ModelAction *parent = get_last_action(tid);
2289 parent = get_thread(tid)->get_creation();
2294 * Returns the clock vector for a given thread.
2295 * @param tid The thread whose clock vector we want
2296 * @return Desired clock vector
2298 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2300 return get_parent_action(tid)->get_cv();
2304 * Resolve a set of Promises with a current write. The set is provided in the
2305 * Node corresponding to @a write.
2306 * @param write The ModelAction that is fulfilling Promises
2307 * @return True if promises were resolved; false otherwise
2309 bool ModelChecker::resolve_promises(ModelAction *write)
2311 bool resolved = false;
2312 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2314 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2315 Promise *promise = (*promises)[promise_index];
2316 if (write->get_node()->get_promise(i)) {
2317 ModelAction *read = promise->get_action();
2318 if (read->is_rmw()) {
2319 mo_graph->addRMWEdge(write, read);
2321 read_from(read, write);
2322 //First fix up the modification order for actions that happened
2324 r_modification_order(read, write);
2325 //Next fix up the modification order for actions that happened
2327 post_r_modification_order(read, write);
2328 //Make sure the promise's value matches the write's value
2329 ASSERT(promise->get_value() == write->get_value());
2332 promises->erase(promises->begin() + promise_index);
2333 actions_to_check.push_back(read);
2340 //Check whether reading these writes has made threads unable to
2343 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2344 ModelAction *read=actions_to_check[i];
2345 mo_check_promises(read->get_tid(), write, read);
2352 * Compute the set of promises that could potentially be satisfied by this
2353 * action. Note that the set computation actually appears in the Node, not in
2355 * @param curr The ModelAction that may satisfy promises
2357 void ModelChecker::compute_promises(ModelAction *curr)
2359 for (unsigned int i = 0; i < promises->size(); i++) {
2360 Promise *promise = (*promises)[i];
2361 const ModelAction *act = promise->get_action();
2362 if (!act->happens_before(curr) &&
2364 !act->could_synchronize_with(curr) &&
2365 !act->same_thread(curr) &&
2366 act->get_location() == curr->get_location() &&
2367 promise->get_value() == curr->get_value()) {
2368 curr->get_node()->set_promise(i, act->is_rmw());
2373 /** Checks promises in response to change in ClockVector Threads. */
2374 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2376 for (unsigned int i = 0; i < promises->size(); i++) {
2377 Promise *promise = (*promises)[i];
2378 const ModelAction *act = promise->get_action();
2379 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2380 merge_cv->synchronized_since(act)) {
2381 if (promise->eliminate_thread(tid)) {
2382 //Promise has failed
2383 priv->failed_promise = true;
2390 void ModelChecker::check_promises_thread_disabled()
2392 for (unsigned int i = 0; i < promises->size(); i++) {
2393 Promise *promise = (*promises)[i];
2394 if (promise->has_failed()) {
2395 priv->failed_promise = true;
2401 /** Checks promises in response to addition to modification order for threads.
2403 * pthread is the thread that performed the read that created the promise
2405 * pread is the read that created the promise
2407 * pwrite is either the first write to same location as pread by
2408 * pthread that is sequenced after pread or the value read by the
2409 * first read to the same lcoation as pread by pthread that is
2410 * sequenced after pread..
2412 * 1. If tid=pthread, then we check what other threads are reachable
2413 * through the mode order starting with pwrite. Those threads cannot
2414 * perform a write that will resolve the promise due to modification
2415 * order constraints.
2417 * 2. If the tid is not pthread, we check whether pwrite can reach the
2418 * action write through the modification order. If so, that thread
2419 * cannot perform a future write that will resolve the promise due to
2420 * modificatin order constraints.
2422 * @param tid The thread that either read from the model action
2423 * write, or actually did the model action write.
2425 * @param write The ModelAction representing the relevant write.
2426 * @param read The ModelAction that reads a promised write, or NULL otherwise.
2428 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write, const ModelAction *read)
2430 void *location = write->get_location();
2431 for (unsigned int i = 0; i < promises->size(); i++) {
2432 Promise *promise = (*promises)[i];
2433 const ModelAction *act = promise->get_action();
2435 //Is this promise on the same location?
2436 if (act->get_location() != location)
2439 //same thread as the promise
2440 if (act->get_tid() == tid) {
2441 //make sure that the reader of this write happens after the promise
2442 if (( read == NULL ) || ( promise->get_action() -> happens_before(read))) {
2443 //do we have a pwrite for the promise, if not, set it
2444 if (promise->get_write() == NULL) {
2445 promise->set_write(write);
2446 //The pwrite cannot happen before the promise
2447 if (write->happens_before(act) && (write != act)) {
2448 priv->failed_promise = true;
2453 if (mo_graph->checkPromise(write, promise)) {
2454 priv->failed_promise = true;
2460 //Don't do any lookups twice for the same thread
2461 if (promise->thread_is_eliminated(tid))
2464 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2465 if (promise->eliminate_thread(tid)) {
2466 priv->failed_promise = true;
2474 * Compute the set of writes that may break the current pending release
2475 * sequence. This information is extracted from previou release sequence
2478 * @param curr The current ModelAction. Must be a release sequence fixup
2481 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2483 if (pending_rel_seqs->empty())
2486 struct release_seq *pending = pending_rel_seqs->back();
2487 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2488 const ModelAction *write = pending->writes[i];
2489 curr->get_node()->add_relseq_break(write);
2492 /* NULL means don't break the sequence; just synchronize */
2493 curr->get_node()->add_relseq_break(NULL);
2497 * Build up an initial set of all past writes that this 'read' action may read
2498 * from. This set is determined by the clock vector's "happens before"
2500 * @param curr is the current ModelAction that we are exploring; it must be a
2503 void ModelChecker::build_reads_from_past(ModelAction *curr)
2505 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2507 ASSERT(curr->is_read());
2509 ModelAction *last_sc_write = NULL;
2511 if (curr->is_seqcst())
2512 last_sc_write = get_last_seq_cst_write(curr);
2514 /* Iterate over all threads */
2515 for (i = 0; i < thrd_lists->size(); i++) {
2516 /* Iterate over actions in thread, starting from most recent */
2517 action_list_t *list = &(*thrd_lists)[i];
2518 action_list_t::reverse_iterator rit;
2519 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2520 ModelAction *act = *rit;
2522 /* Only consider 'write' actions */
2523 if (!act->is_write() || act == curr)
2526 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2527 bool allow_read = true;
2529 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2531 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2535 curr->get_node()->add_read_from(act);
2537 /* Include at most one act per-thread that "happens before" curr */
2538 if (act->happens_before(curr))
2543 if (DBG_ENABLED()) {
2544 model_print("Reached read action:\n");
2546 model_print("Printing may_read_from\n");
2547 curr->get_node()->print_may_read_from();
2548 model_print("End printing may_read_from\n");
2552 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2555 /* UNINIT actions don't have a Node, and they never sleep */
2556 if (write->is_uninitialized())
2558 Node *prevnode = write->get_node()->get_parent();
2560 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2561 if (write->is_release() && thread_sleep)
2563 if (!write->is_rmw()) {
2566 if (write->get_reads_from() == NULL)
2568 write = write->get_reads_from();
2573 * @brief Create a new action representing an uninitialized atomic
2574 * @param location The memory location of the atomic object
2575 * @return A pointer to a new ModelAction
2577 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2579 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2580 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2581 act->create_cv(NULL);
2585 static void print_list(action_list_t *list)
2587 action_list_t::iterator it;
2589 model_print("---------------------------------------------------------------------\n");
2591 unsigned int hash = 0;
2593 for (it = list->begin(); it != list->end(); it++) {
2595 hash = hash^(hash<<3)^((*it)->hash());
2597 model_print("HASH %u\n", hash);
2598 model_print("---------------------------------------------------------------------\n");
2601 #if SUPPORT_MOD_ORDER_DUMP
2602 void ModelChecker::dumpGraph(char *filename) const
2605 sprintf(buffer, "%s.dot", filename);
2606 FILE *file = fopen(buffer, "w");
2607 fprintf(file, "digraph %s {\n", filename);
2608 mo_graph->dumpNodes(file);
2609 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2611 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2612 ModelAction *action = *it;
2613 if (action->is_read()) {
2614 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2615 if (action->get_reads_from() != NULL)
2616 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2618 if (thread_array[action->get_tid()] != NULL) {
2619 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2622 thread_array[action->get_tid()] = action;
2624 fprintf(file, "}\n");
2625 model_free(thread_array);
2630 /** @brief Prints an execution trace summary. */
2631 void ModelChecker::print_summary() const
2633 #if SUPPORT_MOD_ORDER_DUMP
2635 char buffername[100];
2636 sprintf(buffername, "exec%04u", stats.num_total);
2637 mo_graph->dumpGraphToFile(buffername);
2638 sprintf(buffername, "graph%04u", stats.num_total);
2639 dumpGraph(buffername);
2642 model_print("Execution %d:", stats.num_total);
2643 if (isfeasibleprefix())
2646 print_infeasibility(" INFEASIBLE");
2647 print_list(action_trace);
2652 * Add a Thread to the system for the first time. Should only be called once
2654 * @param t The Thread to add
2656 void ModelChecker::add_thread(Thread *t)
2658 thread_map->put(id_to_int(t->get_id()), t);
2659 scheduler->add_thread(t);
2663 * Removes a thread from the scheduler.
2664 * @param the thread to remove.
2666 void ModelChecker::remove_thread(Thread *t)
2668 scheduler->remove_thread(t);
2672 * @brief Get a Thread reference by its ID
2673 * @param tid The Thread's ID
2674 * @return A Thread reference
2676 Thread * ModelChecker::get_thread(thread_id_t tid) const
2678 return thread_map->get(id_to_int(tid));
2682 * @brief Get a reference to the Thread in which a ModelAction was executed
2683 * @param act The ModelAction
2684 * @return A Thread reference
2686 Thread * ModelChecker::get_thread(ModelAction *act) const
2688 return get_thread(act->get_tid());
2692 * @brief Check if a Thread is currently enabled
2693 * @param t The Thread to check
2694 * @return True if the Thread is currently enabled
2696 bool ModelChecker::is_enabled(Thread *t) const
2698 return scheduler->is_enabled(t);
2702 * @brief Check if a Thread is currently enabled
2703 * @param tid The ID of the Thread to check
2704 * @return True if the Thread is currently enabled
2706 bool ModelChecker::is_enabled(thread_id_t tid) const
2708 return scheduler->is_enabled(tid);
2712 * Switch from a user-context to the "master thread" context (a.k.a. system
2713 * context). This switch is made with the intention of exploring a particular
2714 * model-checking action (described by a ModelAction object). Must be called
2715 * from a user-thread context.
2717 * @param act The current action that will be explored. May be NULL only if
2718 * trace is exiting via an assertion (see ModelChecker::set_assert and
2719 * ModelChecker::has_asserted).
2720 * @return Return the value returned by the current action
2722 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2725 Thread *old = thread_current();
2726 set_current_action(act);
2727 old->set_state(THREAD_READY);
2728 if (Thread::swap(old, &system_context) < 0) {
2729 perror("swap threads");
2732 return old->get_return_value();
2736 * Takes the next step in the execution, if possible.
2737 * @param curr The current step to take
2738 * @return Returns true (success) if a step was taken and false otherwise.
2740 bool ModelChecker::take_step(ModelAction *curr)
2745 Thread *curr_thrd = get_thread(curr);
2746 ASSERT(curr_thrd->get_state() == THREAD_READY);
2748 curr = check_current_action(curr);
2750 /* Infeasible -> don't take any more steps */
2751 if (is_infeasible())
2753 else if (isfeasibleprefix() && have_bug_reports()) {
2758 if (params.bound != 0)
2759 if (priv->used_sequence_numbers > params.bound)
2762 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2763 scheduler->remove_thread(curr_thrd);
2765 Thread *next_thrd = get_next_thread(curr);
2766 next_thrd = scheduler->next_thread(next_thrd);
2768 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2769 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2772 * Launch end-of-execution release sequence fixups only when there are:
2774 * (1) no more user threads to run (or when execution replay chooses
2775 * the 'model_thread')
2776 * (2) pending release sequences
2777 * (3) pending assertions (i.e., data races)
2778 * (4) no pending promises
2780 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2781 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2782 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2783 pending_rel_seqs->size());
2784 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2785 std::memory_order_seq_cst, NULL, VALUE_NONE,
2787 set_current_action(fixup);
2791 /* next_thrd == NULL -> don't take any more steps */
2795 next_thrd->set_state(THREAD_RUNNING);
2797 if (next_thrd->get_pending() != NULL) {
2798 /* restart a pending action */
2799 set_current_action(next_thrd->get_pending());
2800 next_thrd->set_pending(NULL);
2801 next_thrd->set_state(THREAD_READY);
2805 /* Return false only if swap fails with an error */
2806 return (Thread::swap(&system_context, next_thrd) == 0);
2809 /** Wrapper to run the user's main function, with appropriate arguments */
2810 void user_main_wrapper(void *)
2812 user_main(model->params.argc, model->params.argv);
2815 /** @brief Run ModelChecker for the user program */
2816 void ModelChecker::run()
2820 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2824 /* Run user thread up to its first action */
2825 scheduler->next_thread(t);
2826 Thread::swap(&system_context, t);
2828 /* Wait for all threads to complete */
2829 while (take_step(priv->current_action));
2830 } while (next_execution());