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() :
42 /* First thread created will have id INITIAL_THREAD_ID */
43 next_thread_id(INITIAL_THREAD_ID),
44 used_sequence_numbers(0),
48 failed_promise(false),
49 too_many_reads(false),
50 no_valid_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 unsigned int next_thread_id;
62 modelclock_t used_sequence_numbers;
63 ModelAction *next_backtrack;
64 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
65 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 */
163 * FIXME: if we utilize partial rollback, we will need to free only
164 * those pending actions which were NOT pending before the rollback
167 for (unsigned int i = 0; i < get_num_threads(); i++)
168 delete get_thread(int_to_id(i))->get_pending();
170 snapshot_backtrack_before(0);
173 /** @return a thread ID for a new Thread */
174 thread_id_t ModelChecker::get_next_id()
176 return priv->next_thread_id++;
179 /** @return the number of user threads created during this execution */
180 unsigned int ModelChecker::get_num_threads() const
182 return priv->next_thread_id;
186 * Must be called from user-thread context (e.g., through the global
187 * thread_current() interface)
189 * @return The currently executing Thread.
191 Thread * ModelChecker::get_current_thread() const
193 return scheduler->get_current_thread();
196 /** @return a sequence number for a new ModelAction */
197 modelclock_t ModelChecker::get_next_seq_num()
199 return ++priv->used_sequence_numbers;
202 Node * ModelChecker::get_curr_node() const
204 return node_stack->get_head();
208 * @brief Choose the next thread to execute.
210 * This function chooses the next thread that should execute. It can force the
211 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
212 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
213 * The model-checker may have no preference regarding the next thread (i.e.,
214 * when exploring a new execution ordering), in which case this will return
216 * @param curr The current ModelAction. This action might guide the choice of
218 * @return The next thread to run. If the model-checker has no preference, NULL.
220 Thread * ModelChecker::get_next_thread(ModelAction *curr)
225 /* Do not split atomic actions. */
227 return get_thread(curr);
228 else if (curr->get_type() == THREAD_CREATE)
229 return curr->get_thread_operand();
232 /* Have we completed exploring the preselected path? */
236 /* Else, we are trying to replay an execution */
237 ModelAction *next = node_stack->get_next()->get_action();
239 if (next == diverge) {
240 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
241 earliest_diverge = diverge;
243 Node *nextnode = next->get_node();
244 Node *prevnode = nextnode->get_parent();
245 scheduler->update_sleep_set(prevnode);
247 /* Reached divergence point */
248 if (nextnode->increment_misc()) {
249 /* The next node will try to satisfy a different misc_index values. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_promise()) {
253 /* The next node will try to satisfy a different set of promises. */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
256 } else if (nextnode->increment_read_from()) {
257 /* The next node will read from a different value. */
258 tid = next->get_tid();
259 node_stack->pop_restofstack(2);
260 } else if (nextnode->increment_future_value()) {
261 /* The next node will try to read from a different future value. */
262 tid = next->get_tid();
263 node_stack->pop_restofstack(2);
264 } else if (nextnode->increment_relseq_break()) {
265 /* The next node will try to resolve a release sequence differently */
266 tid = next->get_tid();
267 node_stack->pop_restofstack(2);
270 /* Make a different thread execute for next step */
271 scheduler->add_sleep(get_thread(next->get_tid()));
272 tid = prevnode->get_next_backtrack();
273 /* Make sure the backtracked thread isn't sleeping. */
274 node_stack->pop_restofstack(1);
275 if (diverge == earliest_diverge) {
276 earliest_diverge = prevnode->get_action();
279 /* The correct sleep set is in the parent node. */
282 DEBUG("*** Divergence point ***\n");
286 tid = next->get_tid();
288 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
289 ASSERT(tid != THREAD_ID_T_NONE);
290 return thread_map->get(id_to_int(tid));
294 * We need to know what the next actions of all threads in the sleep
295 * set will be. This method computes them and stores the actions at
296 * the corresponding thread object's pending action.
299 void ModelChecker::execute_sleep_set()
301 for (unsigned int i = 0; i < get_num_threads(); i++) {
302 thread_id_t tid = int_to_id(i);
303 Thread *thr = get_thread(tid);
304 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
305 thr->get_pending()->set_sleep_flag();
310 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
312 for (unsigned int i = 0; i < get_num_threads(); i++) {
313 Thread *thr = get_thread(int_to_id(i));
314 if (scheduler->is_sleep_set(thr)) {
315 ModelAction *pending_act = thr->get_pending();
316 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
317 //Remove this thread from sleep set
318 scheduler->remove_sleep(thr);
323 /** @brief Alert the model-checker that an incorrectly-ordered
324 * synchronization was made */
325 void ModelChecker::set_bad_synchronization()
327 priv->bad_synchronization = true;
331 * Check whether the current trace has triggered an assertion which should halt
334 * @return True, if the execution should be aborted; false otherwise
336 bool ModelChecker::has_asserted() const
338 return priv->asserted;
342 * Trigger a trace assertion which should cause this execution to be halted.
343 * This can be due to a detected bug or due to an infeasibility that should
346 void ModelChecker::set_assert()
348 priv->asserted = true;
352 * Check if we are in a deadlock. Should only be called at the end of an
353 * execution, although it should not give false positives in the middle of an
354 * execution (there should be some ENABLED thread).
356 * @return True if program is in a deadlock; false otherwise
358 bool ModelChecker::is_deadlocked() const
360 bool blocking_threads = false;
361 for (unsigned int i = 0; i < get_num_threads(); i++) {
362 thread_id_t tid = int_to_id(i);
365 Thread *t = get_thread(tid);
366 if (!t->is_model_thread() && t->get_pending())
367 blocking_threads = true;
369 return blocking_threads;
373 * Check if this is a complete execution. That is, have all thread completed
374 * execution (rather than exiting because sleep sets have forced a redundant
377 * @return True if the execution is complete.
379 bool ModelChecker::is_complete_execution() const
381 for (unsigned int i = 0; i < get_num_threads(); i++)
382 if (is_enabled(int_to_id(i)))
388 * @brief Assert a bug in the executing program.
390 * Use this function to assert any sort of bug in the user program. If the
391 * current trace is feasible (actually, a prefix of some feasible execution),
392 * then this execution will be aborted, printing the appropriate message. If
393 * the current trace is not yet feasible, the error message will be stashed and
394 * printed if the execution ever becomes feasible.
396 * @param msg Descriptive message for the bug (do not include newline char)
397 * @return True if bug is immediately-feasible
399 bool ModelChecker::assert_bug(const char *msg)
401 priv->bugs.push_back(new bug_message(msg));
403 if (isfeasibleprefix()) {
411 * @brief Assert a bug in the executing program, asserted by a user thread
412 * @see ModelChecker::assert_bug
413 * @param msg Descriptive message for the bug (do not include newline char)
415 void ModelChecker::assert_user_bug(const char *msg)
417 /* If feasible bug, bail out now */
419 switch_to_master(NULL);
422 /** @return True, if any bugs have been reported for this execution */
423 bool ModelChecker::have_bug_reports() const
425 return priv->bugs.size() != 0;
428 /** @brief Print bug report listing for this execution (if any bugs exist) */
429 void ModelChecker::print_bugs() const
431 if (have_bug_reports()) {
432 model_print("Bug report: %zu bug%s detected\n",
434 priv->bugs.size() > 1 ? "s" : "");
435 for (unsigned int i = 0; i < priv->bugs.size(); i++)
436 priv->bugs[i]->print();
441 * @brief Record end-of-execution stats
443 * Must be run when exiting an execution. Records various stats.
444 * @see struct execution_stats
446 void ModelChecker::record_stats()
449 if (!isfeasibleprefix())
450 stats.num_infeasible++;
451 else if (have_bug_reports())
452 stats.num_buggy_executions++;
453 else if (is_complete_execution())
454 stats.num_complete++;
456 stats.num_redundant++;
459 /** @brief Print execution stats */
460 void ModelChecker::print_stats() const
462 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
463 model_print("Number of redundant executions: %d\n", stats.num_redundant);
464 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
465 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
466 model_print("Total executions: %d\n", stats.num_total);
467 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
471 * @brief End-of-exeuction print
472 * @param printbugs Should any existing bugs be printed?
474 void ModelChecker::print_execution(bool printbugs) const
476 print_program_output();
478 if (DBG_ENABLED() || params.verbose) {
479 model_print("Earliest divergence point since last feasible execution:\n");
480 if (earliest_diverge)
481 earliest_diverge->print();
483 model_print("(Not set)\n");
489 /* Don't print invalid bugs */
498 * Queries the model-checker for more executions to explore and, if one
499 * exists, resets the model-checker state to execute a new execution.
501 * @return If there are more executions to explore, return true. Otherwise,
504 bool ModelChecker::next_execution()
507 /* Is this execution a feasible execution that's worth bug-checking? */
508 bool complete = isfeasibleprefix() && (is_complete_execution() ||
511 /* End-of-execution bug checks */
514 assert_bug("Deadlock detected");
522 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
523 print_execution(complete);
525 clear_program_output();
528 earliest_diverge = NULL;
530 if ((diverge = get_next_backtrack()) == NULL)
534 model_print("Next execution will diverge at:\n");
538 reset_to_initial_state();
542 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
544 switch (act->get_type()) {
549 /* Optimization: relaxed operations don't need backtracking */
550 if (act->is_relaxed())
552 /* linear search: from most recent to oldest */
553 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
554 action_list_t::reverse_iterator rit;
555 for (rit = list->rbegin(); rit != list->rend(); rit++) {
556 ModelAction *prev = *rit;
557 if (prev->could_synchronize_with(act))
563 case ATOMIC_TRYLOCK: {
564 /* linear search: from most recent to oldest */
565 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
566 action_list_t::reverse_iterator rit;
567 for (rit = list->rbegin(); rit != list->rend(); rit++) {
568 ModelAction *prev = *rit;
569 if (act->is_conflicting_lock(prev))
574 case ATOMIC_UNLOCK: {
575 /* linear search: from most recent to oldest */
576 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
577 action_list_t::reverse_iterator rit;
578 for (rit = list->rbegin(); rit != list->rend(); rit++) {
579 ModelAction *prev = *rit;
580 if (!act->same_thread(prev) && prev->is_failed_trylock())
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_failed_trylock())
593 if (!act->same_thread(prev) && prev->is_notify())
599 case ATOMIC_NOTIFY_ALL:
600 case ATOMIC_NOTIFY_ONE: {
601 /* linear search: from most recent to oldest */
602 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
603 action_list_t::reverse_iterator rit;
604 for (rit = list->rbegin(); rit != list->rend(); rit++) {
605 ModelAction *prev = *rit;
606 if (!act->same_thread(prev) && prev->is_wait())
617 /** This method finds backtracking points where we should try to
618 * reorder the parameter ModelAction against.
620 * @param the ModelAction to find backtracking points for.
622 void ModelChecker::set_backtracking(ModelAction *act)
624 Thread *t = get_thread(act);
625 ModelAction *prev = get_last_conflict(act);
629 Node *node = prev->get_node()->get_parent();
631 int low_tid, high_tid;
632 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
633 low_tid = id_to_int(act->get_tid());
634 high_tid = low_tid + 1;
637 high_tid = get_num_threads();
640 for (int i = low_tid; i < high_tid; i++) {
641 thread_id_t tid = int_to_id(i);
643 /* Make sure this thread can be enabled here. */
644 if (i >= node->get_num_threads())
647 /* Don't backtrack into a point where the thread is disabled or sleeping. */
648 if (node->enabled_status(tid) != THREAD_ENABLED)
651 /* Check if this has been explored already */
652 if (node->has_been_explored(tid))
655 /* See if fairness allows */
656 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
658 for (int t = 0; t < node->get_num_threads(); t++) {
659 thread_id_t tother = int_to_id(t);
660 if (node->is_enabled(tother) && node->has_priority(tother)) {
668 /* Cache the latest backtracking point */
669 set_latest_backtrack(prev);
671 /* If this is a new backtracking point, mark the tree */
672 if (!node->set_backtrack(tid))
674 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
675 id_to_int(prev->get_tid()),
676 id_to_int(t->get_id()));
685 * @brief Cache the a backtracking point as the "most recent", if eligible
687 * Note that this does not prepare the NodeStack for this backtracking
688 * operation, it only caches the action on a per-execution basis
690 * @param act The operation at which we should explore a different next action
691 * (i.e., backtracking point)
692 * @return True, if this action is now the most recent backtracking point;
695 bool ModelChecker::set_latest_backtrack(ModelAction *act)
697 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
698 priv->next_backtrack = act;
705 * Returns last backtracking point. The model checker will explore a different
706 * path for this point in the next execution.
707 * @return The ModelAction at which the next execution should diverge.
709 ModelAction * ModelChecker::get_next_backtrack()
711 ModelAction *next = priv->next_backtrack;
712 priv->next_backtrack = NULL;
717 * Processes a read or rmw model action.
718 * @param curr is the read model action to process.
719 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
720 * @return True if processing this read updates the mo_graph.
722 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
724 uint64_t value = VALUE_NONE;
725 bool updated = false;
727 const ModelAction *reads_from = curr->get_node()->get_read_from();
728 if (reads_from != NULL) {
729 mo_graph->startChanges();
731 value = reads_from->get_value();
732 bool r_status = false;
734 if (!second_part_of_rmw) {
735 check_recency(curr, reads_from);
736 r_status = r_modification_order(curr, reads_from);
739 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
740 mo_graph->rollbackChanges();
741 priv->too_many_reads = false;
745 read_from(curr, reads_from);
746 mo_graph->commitChanges();
747 mo_check_promises(curr, true);
750 } else if (!second_part_of_rmw) {
751 /* Read from future value */
752 struct future_value fv = curr->get_node()->get_future_value();
753 Promise *promise = new Promise(curr, fv);
755 curr->set_read_from_promise(promise);
756 promises->push_back(promise);
757 mo_graph->startChanges();
758 updated = r_modification_order(curr, promise);
759 mo_graph->commitChanges();
761 get_thread(curr)->set_return_value(value);
767 * Processes a lock, trylock, or unlock model action. @param curr is
768 * the read model action to process.
770 * The try lock operation checks whether the lock is taken. If not,
771 * it falls to the normal lock operation case. If so, it returns
774 * The lock operation has already been checked that it is enabled, so
775 * it just grabs the lock and synchronizes with the previous unlock.
777 * The unlock operation has to re-enable all of the threads that are
778 * waiting on the lock.
780 * @return True if synchronization was updated; false otherwise
782 bool ModelChecker::process_mutex(ModelAction *curr)
784 std::mutex *mutex = NULL;
785 struct std::mutex_state *state = NULL;
787 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
788 mutex = (std::mutex *)curr->get_location();
789 state = mutex->get_state();
790 } else if (curr->is_wait()) {
791 mutex = (std::mutex *)curr->get_value();
792 state = mutex->get_state();
795 switch (curr->get_type()) {
796 case ATOMIC_TRYLOCK: {
797 bool success = !state->islocked;
798 curr->set_try_lock(success);
800 get_thread(curr)->set_return_value(0);
803 get_thread(curr)->set_return_value(1);
805 //otherwise fall into the lock case
807 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
808 assert_bug("Lock access before initialization");
809 state->islocked = true;
810 ModelAction *unlock = get_last_unlock(curr);
811 //synchronize with the previous unlock statement
812 if (unlock != NULL) {
813 curr->synchronize_with(unlock);
818 case ATOMIC_UNLOCK: {
820 state->islocked = false;
821 //wake up the other threads
822 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
823 //activate all the waiting threads
824 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
825 scheduler->wake(get_thread(*rit));
832 state->islocked = false;
833 //wake up the other threads
834 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
835 //activate all the waiting threads
836 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
837 scheduler->wake(get_thread(*rit));
840 //check whether we should go to sleep or not...simulate spurious failures
841 if (curr->get_node()->get_misc() == 0) {
842 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
844 scheduler->sleep(get_thread(curr));
848 case ATOMIC_NOTIFY_ALL: {
849 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
850 //activate all the waiting threads
851 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
852 scheduler->wake(get_thread(*rit));
857 case ATOMIC_NOTIFY_ONE: {
858 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
859 int wakeupthread = curr->get_node()->get_misc();
860 action_list_t::iterator it = waiters->begin();
861 advance(it, wakeupthread);
862 scheduler->wake(get_thread(*it));
873 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
875 /* Do more ambitious checks now that mo is more complete */
876 if (mo_may_allow(writer, reader)) {
877 Node *node = reader->get_node();
879 /* Find an ancestor thread which exists at the time of the reader */
880 Thread *write_thread = get_thread(writer);
881 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
882 write_thread = write_thread->get_parent();
884 struct future_value fv = {
886 writer->get_seq_number() + params.maxfuturedelay,
887 write_thread->get_id(),
889 if (node->add_future_value(fv))
890 set_latest_backtrack(reader);
895 * Process a write ModelAction
896 * @param curr The ModelAction to process
897 * @return True if the mo_graph was updated or promises were resolved
899 bool ModelChecker::process_write(ModelAction *curr)
901 bool updated_mod_order = w_modification_order(curr);
902 bool updated_promises = resolve_promises(curr);
904 if (promises->size() == 0) {
905 for (unsigned int i = 0; i < futurevalues->size(); i++) {
906 struct PendingFutureValue pfv = (*futurevalues)[i];
907 add_future_value(pfv.writer, pfv.act);
909 futurevalues->clear();
912 mo_graph->commitChanges();
913 mo_check_promises(curr, false);
915 get_thread(curr)->set_return_value(VALUE_NONE);
916 return updated_mod_order || updated_promises;
920 * Process a fence ModelAction
921 * @param curr The ModelAction to process
922 * @return True if synchronization was updated
924 bool ModelChecker::process_fence(ModelAction *curr)
927 * fence-relaxed: no-op
928 * fence-release: only log the occurence (not in this function), for
929 * use in later synchronization
930 * fence-acquire (this function): search for hypothetical release
933 bool updated = false;
934 if (curr->is_acquire()) {
935 action_list_t *list = action_trace;
936 action_list_t::reverse_iterator rit;
937 /* Find X : is_read(X) && X --sb-> curr */
938 for (rit = list->rbegin(); rit != list->rend(); rit++) {
939 ModelAction *act = *rit;
942 if (act->get_tid() != curr->get_tid())
944 /* Stop at the beginning of the thread */
945 if (act->is_thread_start())
947 /* Stop once we reach a prior fence-acquire */
948 if (act->is_fence() && act->is_acquire())
952 /* read-acquire will find its own release sequences */
953 if (act->is_acquire())
956 /* Establish hypothetical release sequences */
957 rel_heads_list_t release_heads;
958 get_release_seq_heads(curr, act, &release_heads);
959 for (unsigned int i = 0; i < release_heads.size(); i++)
960 if (!curr->synchronize_with(release_heads[i]))
961 set_bad_synchronization();
962 if (release_heads.size() != 0)
970 * @brief Process the current action for thread-related activity
972 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
973 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
974 * synchronization, etc. This function is a no-op for non-THREAD actions
975 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
977 * @param curr The current action
978 * @return True if synchronization was updated or a thread completed
980 bool ModelChecker::process_thread_action(ModelAction *curr)
982 bool updated = false;
984 switch (curr->get_type()) {
985 case THREAD_CREATE: {
986 thrd_t *thrd = (thrd_t *)curr->get_location();
987 struct thread_params *params = (struct thread_params *)curr->get_value();
988 Thread *th = new Thread(thrd, params->func, params->arg);
990 th->set_creation(curr);
991 /* Promises can be satisfied by children */
992 for (unsigned int i = 0; i < promises->size(); i++) {
993 Promise *promise = (*promises)[i];
994 if (promise->thread_is_available(curr->get_tid()))
995 promise->add_thread(th->get_id());
1000 Thread *blocking = curr->get_thread_operand();
1001 ModelAction *act = get_last_action(blocking->get_id());
1002 curr->synchronize_with(act);
1003 updated = true; /* trigger rel-seq checks */
1006 case THREAD_FINISH: {
1007 Thread *th = get_thread(curr);
1008 while (!th->wait_list_empty()) {
1009 ModelAction *act = th->pop_wait_list();
1010 scheduler->wake(get_thread(act));
1013 /* Completed thread can't satisfy promises */
1014 for (unsigned int i = 0; i < promises->size(); i++) {
1015 Promise *promise = (*promises)[i];
1016 if (promise->thread_is_available(th->get_id()))
1017 if (promise->eliminate_thread(th->get_id()))
1018 priv->failed_promise = true;
1020 updated = true; /* trigger rel-seq checks */
1023 case THREAD_START: {
1024 check_promises(curr->get_tid(), NULL, curr->get_cv());
1035 * @brief Process the current action for release sequence fixup activity
1037 * Performs model-checker release sequence fixups for the current action,
1038 * forcing a single pending release sequence to break (with a given, potential
1039 * "loose" write) or to complete (i.e., synchronize). If a pending release
1040 * sequence forms a complete release sequence, then we must perform the fixup
1041 * synchronization, mo_graph additions, etc.
1043 * @param curr The current action; must be a release sequence fixup action
1044 * @param work_queue The work queue to which to add work items as they are
1047 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1049 const ModelAction *write = curr->get_node()->get_relseq_break();
1050 struct release_seq *sequence = pending_rel_seqs->back();
1051 pending_rel_seqs->pop_back();
1053 ModelAction *acquire = sequence->acquire;
1054 const ModelAction *rf = sequence->rf;
1055 const ModelAction *release = sequence->release;
1059 ASSERT(release->same_thread(rf));
1061 if (write == NULL) {
1063 * @todo Forcing a synchronization requires that we set
1064 * modification order constraints. For instance, we can't allow
1065 * a fixup sequence in which two separate read-acquire
1066 * operations read from the same sequence, where the first one
1067 * synchronizes and the other doesn't. Essentially, we can't
1068 * allow any writes to insert themselves between 'release' and
1072 /* Must synchronize */
1073 if (!acquire->synchronize_with(release)) {
1074 set_bad_synchronization();
1077 /* Re-check all pending release sequences */
1078 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1079 /* Re-check act for mo_graph edges */
1080 work_queue->push_back(MOEdgeWorkEntry(acquire));
1082 /* propagate synchronization to later actions */
1083 action_list_t::reverse_iterator rit = action_trace->rbegin();
1084 for (; (*rit) != acquire; rit++) {
1085 ModelAction *propagate = *rit;
1086 if (acquire->happens_before(propagate)) {
1087 propagate->synchronize_with(acquire);
1088 /* Re-check 'propagate' for mo_graph edges */
1089 work_queue->push_back(MOEdgeWorkEntry(propagate));
1093 /* Break release sequence with new edges:
1094 * release --mo--> write --mo--> rf */
1095 mo_graph->addEdge(release, write);
1096 mo_graph->addEdge(write, rf);
1099 /* See if we have realized a data race */
1104 * Initialize the current action by performing one or more of the following
1105 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1106 * in the NodeStack, manipulating backtracking sets, allocating and
1107 * initializing clock vectors, and computing the promises to fulfill.
1109 * @param curr The current action, as passed from the user context; may be
1110 * freed/invalidated after the execution of this function, with a different
1111 * action "returned" its place (pass-by-reference)
1112 * @return True if curr is a newly-explored action; false otherwise
1114 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1116 ModelAction *newcurr;
1118 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1119 newcurr = process_rmw(*curr);
1122 if (newcurr->is_rmw())
1123 compute_promises(newcurr);
1129 (*curr)->set_seq_number(get_next_seq_num());
1131 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1133 /* First restore type and order in case of RMW operation */
1134 if ((*curr)->is_rmwr())
1135 newcurr->copy_typeandorder(*curr);
1137 ASSERT((*curr)->get_location() == newcurr->get_location());
1138 newcurr->copy_from_new(*curr);
1140 /* Discard duplicate ModelAction; use action from NodeStack */
1143 /* Always compute new clock vector */
1144 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1147 return false; /* Action was explored previously */
1151 /* Always compute new clock vector */
1152 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1154 /* Assign most recent release fence */
1155 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1158 * Perform one-time actions when pushing new ModelAction onto
1161 if (newcurr->is_write())
1162 compute_promises(newcurr);
1163 else if (newcurr->is_relseq_fixup())
1164 compute_relseq_breakwrites(newcurr);
1165 else if (newcurr->is_wait())
1166 newcurr->get_node()->set_misc_max(2);
1167 else if (newcurr->is_notify_one()) {
1168 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1170 return true; /* This was a new ModelAction */
1175 * @brief Establish reads-from relation between two actions
1177 * Perform basic operations involved with establishing a concrete rf relation,
1178 * including setting the ModelAction data and checking for release sequences.
1180 * @param act The action that is reading (must be a read)
1181 * @param rf The action from which we are reading (must be a write)
1183 * @return True if this read established synchronization
1185 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1187 act->set_read_from(rf);
1188 if (rf != NULL && act->is_acquire()) {
1189 rel_heads_list_t release_heads;
1190 get_release_seq_heads(act, act, &release_heads);
1191 int num_heads = release_heads.size();
1192 for (unsigned int i = 0; i < release_heads.size(); i++)
1193 if (!act->synchronize_with(release_heads[i])) {
1194 set_bad_synchronization();
1197 return num_heads > 0;
1203 * @brief Check whether a model action is enabled.
1205 * Checks whether a lock or join operation would be successful (i.e., is the
1206 * lock already locked, or is the joined thread already complete). If not, put
1207 * the action in a waiter list.
1209 * @param curr is the ModelAction to check whether it is enabled.
1210 * @return a bool that indicates whether the action is enabled.
1212 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1213 if (curr->is_lock()) {
1214 std::mutex *lock = (std::mutex *)curr->get_location();
1215 struct std::mutex_state *state = lock->get_state();
1216 if (state->islocked) {
1217 //Stick the action in the appropriate waiting queue
1218 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1221 } else if (curr->get_type() == THREAD_JOIN) {
1222 Thread *blocking = (Thread *)curr->get_location();
1223 if (!blocking->is_complete()) {
1224 blocking->push_wait_list(curr);
1233 * This is the heart of the model checker routine. It performs model-checking
1234 * actions corresponding to a given "current action." Among other processes, it
1235 * calculates reads-from relationships, updates synchronization clock vectors,
1236 * forms a memory_order constraints graph, and handles replay/backtrack
1237 * execution when running permutations of previously-observed executions.
1239 * @param curr The current action to process
1240 * @return The ModelAction that is actually executed; may be different than
1241 * curr; may be NULL, if the current action is not enabled to run
1243 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1246 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1248 if (!check_action_enabled(curr)) {
1249 /* Make the execution look like we chose to run this action
1250 * much later, when a lock/join can succeed */
1251 get_thread(curr)->set_pending(curr);
1252 scheduler->sleep(get_thread(curr));
1256 bool newly_explored = initialize_curr_action(&curr);
1262 wake_up_sleeping_actions(curr);
1264 /* Add the action to lists before any other model-checking tasks */
1265 if (!second_part_of_rmw)
1266 add_action_to_lists(curr);
1268 /* Build may_read_from set for newly-created actions */
1269 if (newly_explored && curr->is_read())
1270 build_reads_from_past(curr);
1272 /* Initialize work_queue with the "current action" work */
1273 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1274 while (!work_queue.empty() && !has_asserted()) {
1275 WorkQueueEntry work = work_queue.front();
1276 work_queue.pop_front();
1278 switch (work.type) {
1279 case WORK_CHECK_CURR_ACTION: {
1280 ModelAction *act = work.action;
1281 bool update = false; /* update this location's release seq's */
1282 bool update_all = false; /* update all release seq's */
1284 if (process_thread_action(curr))
1287 if (act->is_read() && process_read(act, second_part_of_rmw))
1290 if (act->is_write() && process_write(act))
1293 if (act->is_fence() && process_fence(act))
1296 if (act->is_mutex_op() && process_mutex(act))
1299 if (act->is_relseq_fixup())
1300 process_relseq_fixup(curr, &work_queue);
1303 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1305 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1308 case WORK_CHECK_RELEASE_SEQ:
1309 resolve_release_sequences(work.location, &work_queue);
1311 case WORK_CHECK_MO_EDGES: {
1312 /** @todo Complete verification of work_queue */
1313 ModelAction *act = work.action;
1314 bool updated = false;
1316 if (act->is_read()) {
1317 const ModelAction *rf = act->get_reads_from();
1318 const Promise *promise = act->get_reads_from_promise();
1320 if (r_modification_order(act, rf))
1322 } else if (promise) {
1323 if (r_modification_order(act, promise))
1327 if (act->is_write()) {
1328 if (w_modification_order(act))
1331 mo_graph->commitChanges();
1334 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1343 check_curr_backtracking(curr);
1344 set_backtracking(curr);
1348 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1350 Node *currnode = curr->get_node();
1351 Node *parnode = currnode->get_parent();
1353 if ((parnode && !parnode->backtrack_empty()) ||
1354 !currnode->misc_empty() ||
1355 !currnode->read_from_empty() ||
1356 !currnode->future_value_empty() ||
1357 !currnode->promise_empty() ||
1358 !currnode->relseq_break_empty()) {
1359 set_latest_backtrack(curr);
1363 bool ModelChecker::promises_expired() const
1365 for (unsigned int i = 0; i < promises->size(); i++) {
1366 Promise *promise = (*promises)[i];
1367 if (promise->get_expiration() < priv->used_sequence_numbers)
1374 * This is the strongest feasibility check available.
1375 * @return whether the current trace (partial or complete) must be a prefix of
1378 bool ModelChecker::isfeasibleprefix() const
1380 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1384 * Print disagnostic information about an infeasible execution
1385 * @param prefix A string to prefix the output with; if NULL, then a default
1386 * message prefix will be provided
1388 void ModelChecker::print_infeasibility(const char *prefix) const
1392 if (mo_graph->checkForCycles())
1393 ptr += sprintf(ptr, "[mo cycle]");
1394 if (priv->failed_promise)
1395 ptr += sprintf(ptr, "[failed promise]");
1396 if (priv->too_many_reads)
1397 ptr += sprintf(ptr, "[too many reads]");
1398 if (priv->no_valid_reads)
1399 ptr += sprintf(ptr, "[no valid reads-from]");
1400 if (priv->bad_synchronization)
1401 ptr += sprintf(ptr, "[bad sw ordering]");
1402 if (promises_expired())
1403 ptr += sprintf(ptr, "[promise expired]");
1404 if (promises->size() != 0)
1405 ptr += sprintf(ptr, "[unresolved promise]");
1407 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1411 * Returns whether the current completed trace is feasible, except for pending
1412 * release sequences.
1414 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1416 return !is_infeasible() && promises->size() == 0;
1420 * Check if the current partial trace is infeasible. Does not check any
1421 * end-of-execution flags, which might rule out the execution. Thus, this is
1422 * useful only for ruling an execution as infeasible.
1423 * @return whether the current partial trace is infeasible.
1425 bool ModelChecker::is_infeasible() const
1427 return mo_graph->checkForCycles() ||
1428 priv->no_valid_reads ||
1429 priv->failed_promise ||
1430 priv->too_many_reads ||
1431 priv->bad_synchronization ||
1435 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1436 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1437 ModelAction *lastread = get_last_action(act->get_tid());
1438 lastread->process_rmw(act);
1439 if (act->is_rmw()) {
1440 if (lastread->get_reads_from())
1441 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1443 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1444 mo_graph->commitChanges();
1450 * Checks whether a thread has read from the same write for too many times
1451 * without seeing the effects of a later write.
1454 * 1) there must a different write that we could read from that would satisfy the modification order,
1455 * 2) we must have read from the same value in excess of maxreads times, and
1456 * 3) that other write must have been in the reads_from set for maxreads times.
1458 * If so, we decide that the execution is no longer feasible.
1460 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1462 if (params.maxreads != 0) {
1463 if (curr->get_node()->get_read_from_size() <= 1)
1465 //Must make sure that execution is currently feasible... We could
1466 //accidentally clear by rolling back
1467 if (is_infeasible())
1469 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1470 int tid = id_to_int(curr->get_tid());
1473 if ((int)thrd_lists->size() <= tid)
1475 action_list_t *list = &(*thrd_lists)[tid];
1477 action_list_t::reverse_iterator rit = list->rbegin();
1478 /* Skip past curr */
1479 for (; (*rit) != curr; rit++)
1481 /* go past curr now */
1484 action_list_t::reverse_iterator ritcopy = rit;
1485 //See if we have enough reads from the same value
1487 for (; count < params.maxreads; rit++, count++) {
1488 if (rit == list->rend())
1490 ModelAction *act = *rit;
1491 if (!act->is_read())
1494 if (act->get_reads_from() != rf)
1496 if (act->get_node()->get_read_from_size() <= 1)
1499 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1501 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1503 /* Need a different write */
1507 /* Test to see whether this is a feasible write to read from */
1508 /** NOTE: all members of read-from set should be
1509 * feasible, so we no longer check it here **/
1513 bool feasiblewrite = true;
1514 //new we need to see if this write works for everyone
1516 for (int loop = count; loop > 0; loop--, rit++) {
1517 ModelAction *act = *rit;
1518 bool foundvalue = false;
1519 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1520 if (act->get_node()->get_read_from_at(j) == write) {
1526 feasiblewrite = false;
1530 if (feasiblewrite) {
1531 priv->too_many_reads = true;
1539 * Updates the mo_graph with the constraints imposed from the current
1542 * Basic idea is the following: Go through each other thread and find
1543 * the last action that happened before our read. Two cases:
1545 * (1) The action is a write => that write must either occur before
1546 * the write we read from or be the write we read from.
1548 * (2) The action is a read => the write that that action read from
1549 * must occur before the write we read from or be the same write.
1551 * @param curr The current action. Must be a read.
1552 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1553 * @return True if modification order edges were added; false otherwise
1555 template <typename rf_type>
1556 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1558 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1561 ASSERT(curr->is_read());
1563 /* Last SC fence in the current thread */
1564 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1566 /* Iterate over all threads */
1567 for (i = 0; i < thrd_lists->size(); i++) {
1568 /* Last SC fence in thread i */
1569 ModelAction *last_sc_fence_thread_local = NULL;
1570 if (int_to_id((int)i) != curr->get_tid())
1571 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1573 /* Last SC fence in thread i, before last SC fence in current thread */
1574 ModelAction *last_sc_fence_thread_before = NULL;
1575 if (last_sc_fence_local)
1576 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1578 /* Iterate over actions in thread, starting from most recent */
1579 action_list_t *list = &(*thrd_lists)[i];
1580 action_list_t::reverse_iterator rit;
1581 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1582 ModelAction *act = *rit;
1584 if (act->is_write() && !act->equals(rf) && act != curr) {
1585 /* C++, Section 29.3 statement 5 */
1586 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1587 *act < *last_sc_fence_thread_local) {
1588 added = mo_graph->addEdge(act, rf) || added;
1591 /* C++, Section 29.3 statement 4 */
1592 else if (act->is_seqcst() && last_sc_fence_local &&
1593 *act < *last_sc_fence_local) {
1594 added = mo_graph->addEdge(act, rf) || added;
1597 /* C++, Section 29.3 statement 6 */
1598 else if (last_sc_fence_thread_before &&
1599 *act < *last_sc_fence_thread_before) {
1600 added = mo_graph->addEdge(act, rf) || added;
1606 * Include at most one act per-thread that "happens
1607 * before" curr. Don't consider reflexively.
1609 if (act->happens_before(curr) && act != curr) {
1610 if (act->is_write()) {
1611 if (!act->equals(rf)) {
1612 added = mo_graph->addEdge(act, rf) || added;
1615 const ModelAction *prevreadfrom = act->get_reads_from();
1616 //if the previous read is unresolved, keep going...
1617 if (prevreadfrom == NULL)
1620 if (!prevreadfrom->equals(rf)) {
1621 added = mo_graph->addEdge(prevreadfrom, rf) || added;
1630 * All compatible, thread-exclusive promises must be ordered after any
1631 * concrete loads from the same thread
1633 for (unsigned int i = 0; i < promises->size(); i++)
1634 if ((*promises)[i]->is_compatible_exclusive(curr))
1635 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1641 * Updates the mo_graph with the constraints imposed from the current write.
1643 * Basic idea is the following: Go through each other thread and find
1644 * the lastest action that happened before our write. Two cases:
1646 * (1) The action is a write => that write must occur before
1649 * (2) The action is a read => the write that that action read from
1650 * must occur before the current write.
1652 * This method also handles two other issues:
1654 * (I) Sequential Consistency: Making sure that if the current write is
1655 * seq_cst, that it occurs after the previous seq_cst write.
1657 * (II) Sending the write back to non-synchronizing reads.
1659 * @param curr The current action. Must be a write.
1660 * @return True if modification order edges were added; false otherwise
1662 bool ModelChecker::w_modification_order(ModelAction *curr)
1664 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1667 ASSERT(curr->is_write());
1669 if (curr->is_seqcst()) {
1670 /* We have to at least see the last sequentially consistent write,
1671 so we are initialized. */
1672 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1673 if (last_seq_cst != NULL) {
1674 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1678 /* Last SC fence in the current thread */
1679 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1681 /* Iterate over all threads */
1682 for (i = 0; i < thrd_lists->size(); i++) {
1683 /* Last SC fence in thread i, before last SC fence in current thread */
1684 ModelAction *last_sc_fence_thread_before = NULL;
1685 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1686 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1688 /* Iterate over actions in thread, starting from most recent */
1689 action_list_t *list = &(*thrd_lists)[i];
1690 action_list_t::reverse_iterator rit;
1691 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1692 ModelAction *act = *rit;
1695 * 1) If RMW and it actually read from something, then we
1696 * already have all relevant edges, so just skip to next
1699 * 2) If RMW and it didn't read from anything, we should
1700 * whatever edge we can get to speed up convergence.
1702 * 3) If normal write, we need to look at earlier actions, so
1703 * continue processing list.
1705 if (curr->is_rmw()) {
1706 if (curr->get_reads_from() != NULL)
1714 /* C++, Section 29.3 statement 7 */
1715 if (last_sc_fence_thread_before && act->is_write() &&
1716 *act < *last_sc_fence_thread_before) {
1717 added = mo_graph->addEdge(act, curr) || added;
1722 * Include at most one act per-thread that "happens
1725 if (act->happens_before(curr)) {
1727 * Note: if act is RMW, just add edge:
1729 * The following edge should be handled elsewhere:
1730 * readfrom(act) --mo--> act
1732 if (act->is_write())
1733 added = mo_graph->addEdge(act, curr) || added;
1734 else if (act->is_read()) {
1735 //if previous read accessed a null, just keep going
1736 if (act->get_reads_from() == NULL)
1738 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1741 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1742 !act->same_thread(curr)) {
1743 /* We have an action that:
1744 (1) did not happen before us
1745 (2) is a read and we are a write
1746 (3) cannot synchronize with us
1747 (4) is in a different thread
1749 that read could potentially read from our write. Note that
1750 these checks are overly conservative at this point, we'll
1751 do more checks before actually removing the
1755 if (thin_air_constraint_may_allow(curr, act)) {
1756 if (!is_infeasible())
1757 futurevalues->push_back(PendingFutureValue(curr, act));
1758 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1759 add_future_value(curr, act);
1766 * All compatible, thread-exclusive promises must be ordered after any
1767 * concrete stores to the same thread, or else they can be merged with
1770 for (unsigned int i = 0; i < promises->size(); i++)
1771 if ((*promises)[i]->is_compatible_exclusive(curr))
1772 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1777 /** Arbitrary reads from the future are not allowed. Section 29.3
1778 * part 9 places some constraints. This method checks one result of constraint
1779 * constraint. Others require compiler support. */
1780 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1782 if (!writer->is_rmw())
1785 if (!reader->is_rmw())
1788 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1789 if (search == reader)
1791 if (search->get_tid() == reader->get_tid() &&
1792 search->happens_before(reader))
1800 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1801 * some constraints. This method checks one the following constraint (others
1802 * require compiler support):
1804 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1806 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1808 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1810 /* Iterate over all threads */
1811 for (i = 0; i < thrd_lists->size(); i++) {
1812 const ModelAction *write_after_read = NULL;
1814 /* Iterate over actions in thread, starting from most recent */
1815 action_list_t *list = &(*thrd_lists)[i];
1816 action_list_t::reverse_iterator rit;
1817 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1818 ModelAction *act = *rit;
1820 /* Don't disallow due to act == reader */
1821 if (!reader->happens_before(act) || reader == act)
1823 else if (act->is_write())
1824 write_after_read = act;
1825 else if (act->is_read() && act->get_reads_from() != NULL)
1826 write_after_read = act->get_reads_from();
1829 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1836 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1837 * The ModelAction under consideration is expected to be taking part in
1838 * release/acquire synchronization as an object of the "reads from" relation.
1839 * Note that this can only provide release sequence support for RMW chains
1840 * which do not read from the future, as those actions cannot be traced until
1841 * their "promise" is fulfilled. Similarly, we may not even establish the
1842 * presence of a release sequence with certainty, as some modification order
1843 * constraints may be decided further in the future. Thus, this function
1844 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1845 * and a boolean representing certainty.
1847 * @param rf The action that might be part of a release sequence. Must be a
1849 * @param release_heads A pass-by-reference style return parameter. After
1850 * execution of this function, release_heads will contain the heads of all the
1851 * relevant release sequences, if any exists with certainty
1852 * @param pending A pass-by-reference style return parameter which is only used
1853 * when returning false (i.e., uncertain). Returns most information regarding
1854 * an uncertain release sequence, including any write operations that might
1855 * break the sequence.
1856 * @return true, if the ModelChecker is certain that release_heads is complete;
1859 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1860 rel_heads_list_t *release_heads,
1861 struct release_seq *pending) const
1863 /* Only check for release sequences if there are no cycles */
1864 if (mo_graph->checkForCycles())
1868 ASSERT(rf->is_write());
1870 if (rf->is_release())
1871 release_heads->push_back(rf);
1872 else if (rf->get_last_fence_release())
1873 release_heads->push_back(rf->get_last_fence_release());
1875 break; /* End of RMW chain */
1877 /** @todo Need to be smarter here... In the linux lock
1878 * example, this will run to the beginning of the program for
1880 /** @todo The way to be smarter here is to keep going until 1
1881 * thread has a release preceded by an acquire and you've seen
1884 /* acq_rel RMW is a sufficient stopping condition */
1885 if (rf->is_acquire() && rf->is_release())
1886 return true; /* complete */
1888 rf = rf->get_reads_from();
1891 /* read from future: need to settle this later */
1893 return false; /* incomplete */
1896 if (rf->is_release())
1897 return true; /* complete */
1899 /* else relaxed write
1900 * - check for fence-release in the same thread (29.8, stmt. 3)
1901 * - check modification order for contiguous subsequence
1902 * -> rf must be same thread as release */
1904 const ModelAction *fence_release = rf->get_last_fence_release();
1905 /* Synchronize with a fence-release unconditionally; we don't need to
1906 * find any more "contiguous subsequence..." for it */
1908 release_heads->push_back(fence_release);
1910 int tid = id_to_int(rf->get_tid());
1911 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1912 action_list_t *list = &(*thrd_lists)[tid];
1913 action_list_t::const_reverse_iterator rit;
1915 /* Find rf in the thread list */
1916 rit = std::find(list->rbegin(), list->rend(), rf);
1917 ASSERT(rit != list->rend());
1919 /* Find the last {write,fence}-release */
1920 for (; rit != list->rend(); rit++) {
1921 if (fence_release && *(*rit) < *fence_release)
1923 if ((*rit)->is_release())
1926 if (rit == list->rend()) {
1927 /* No write-release in this thread */
1928 return true; /* complete */
1929 } else if (fence_release && *(*rit) < *fence_release) {
1930 /* The fence-release is more recent (and so, "stronger") than
1931 * the most recent write-release */
1932 return true; /* complete */
1933 } /* else, need to establish contiguous release sequence */
1934 ModelAction *release = *rit;
1936 ASSERT(rf->same_thread(release));
1938 pending->writes.clear();
1940 bool certain = true;
1941 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1942 if (id_to_int(rf->get_tid()) == (int)i)
1944 list = &(*thrd_lists)[i];
1946 /* Can we ensure no future writes from this thread may break
1947 * the release seq? */
1948 bool future_ordered = false;
1950 ModelAction *last = get_last_action(int_to_id(i));
1951 Thread *th = get_thread(int_to_id(i));
1952 if ((last && rf->happens_before(last)) ||
1955 future_ordered = true;
1957 ASSERT(!th->is_model_thread() || future_ordered);
1959 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1960 const ModelAction *act = *rit;
1961 /* Reach synchronization -> this thread is complete */
1962 if (act->happens_before(release))
1964 if (rf->happens_before(act)) {
1965 future_ordered = true;
1969 /* Only non-RMW writes can break release sequences */
1970 if (!act->is_write() || act->is_rmw())
1973 /* Check modification order */
1974 if (mo_graph->checkReachable(rf, act)) {
1975 /* rf --mo--> act */
1976 future_ordered = true;
1979 if (mo_graph->checkReachable(act, release))
1980 /* act --mo--> release */
1982 if (mo_graph->checkReachable(release, act) &&
1983 mo_graph->checkReachable(act, rf)) {
1984 /* release --mo-> act --mo--> rf */
1985 return true; /* complete */
1987 /* act may break release sequence */
1988 pending->writes.push_back(act);
1991 if (!future_ordered)
1992 certain = false; /* This thread is uncertain */
1996 release_heads->push_back(release);
1997 pending->writes.clear();
1999 pending->release = release;
2006 * An interface for getting the release sequence head(s) with which a
2007 * given ModelAction must synchronize. This function only returns a non-empty
2008 * result when it can locate a release sequence head with certainty. Otherwise,
2009 * it may mark the internal state of the ModelChecker so that it will handle
2010 * the release sequence at a later time, causing @a acquire to update its
2011 * synchronization at some later point in execution.
2013 * @param acquire The 'acquire' action that may synchronize with a release
2015 * @param read The read action that may read from a release sequence; this may
2016 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2017 * when 'acquire' is a fence-acquire)
2018 * @param release_heads A pass-by-reference return parameter. Will be filled
2019 * with the head(s) of the release sequence(s), if they exists with certainty.
2020 * @see ModelChecker::release_seq_heads
2022 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2023 ModelAction *read, rel_heads_list_t *release_heads)
2025 const ModelAction *rf = read->get_reads_from();
2026 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2027 sequence->acquire = acquire;
2028 sequence->read = read;
2030 if (!release_seq_heads(rf, release_heads, sequence)) {
2031 /* add act to 'lazy checking' list */
2032 pending_rel_seqs->push_back(sequence);
2034 snapshot_free(sequence);
2039 * Attempt to resolve all stashed operations that might synchronize with a
2040 * release sequence for a given location. This implements the "lazy" portion of
2041 * determining whether or not a release sequence was contiguous, since not all
2042 * modification order information is present at the time an action occurs.
2044 * @param location The location/object that should be checked for release
2045 * sequence resolutions. A NULL value means to check all locations.
2046 * @param work_queue The work queue to which to add work items as they are
2048 * @return True if any updates occurred (new synchronization, new mo_graph
2051 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2053 bool updated = false;
2054 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2055 while (it != pending_rel_seqs->end()) {
2056 struct release_seq *pending = *it;
2057 ModelAction *acquire = pending->acquire;
2058 const ModelAction *read = pending->read;
2060 /* Only resolve sequences on the given location, if provided */
2061 if (location && read->get_location() != location) {
2066 const ModelAction *rf = read->get_reads_from();
2067 rel_heads_list_t release_heads;
2069 complete = release_seq_heads(rf, &release_heads, pending);
2070 for (unsigned int i = 0; i < release_heads.size(); i++) {
2071 if (!acquire->has_synchronized_with(release_heads[i])) {
2072 if (acquire->synchronize_with(release_heads[i]))
2075 set_bad_synchronization();
2080 /* Re-check all pending release sequences */
2081 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2082 /* Re-check read-acquire for mo_graph edges */
2083 if (acquire->is_read())
2084 work_queue->push_back(MOEdgeWorkEntry(acquire));
2086 /* propagate synchronization to later actions */
2087 action_list_t::reverse_iterator rit = action_trace->rbegin();
2088 for (; (*rit) != acquire; rit++) {
2089 ModelAction *propagate = *rit;
2090 if (acquire->happens_before(propagate)) {
2091 propagate->synchronize_with(acquire);
2092 /* Re-check 'propagate' for mo_graph edges */
2093 work_queue->push_back(MOEdgeWorkEntry(propagate));
2098 it = pending_rel_seqs->erase(it);
2099 snapshot_free(pending);
2105 // If we resolved promises or data races, see if we have realized a data race.
2112 * Performs various bookkeeping operations for the current ModelAction. For
2113 * instance, adds action to the per-object, per-thread action vector and to the
2114 * action trace list of all thread actions.
2116 * @param act is the ModelAction to add.
2118 void ModelChecker::add_action_to_lists(ModelAction *act)
2120 int tid = id_to_int(act->get_tid());
2121 ModelAction *uninit = NULL;
2123 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2124 if (list->empty() && act->is_atomic_var()) {
2125 uninit = new_uninitialized_action(act->get_location());
2126 uninit_id = id_to_int(uninit->get_tid());
2127 list->push_back(uninit);
2129 list->push_back(act);
2131 action_trace->push_back(act);
2133 action_trace->push_front(uninit);
2135 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2136 if (tid >= (int)vec->size())
2137 vec->resize(priv->next_thread_id);
2138 (*vec)[tid].push_back(act);
2140 (*vec)[uninit_id].push_front(uninit);
2142 if ((int)thrd_last_action->size() <= tid)
2143 thrd_last_action->resize(get_num_threads());
2144 (*thrd_last_action)[tid] = act;
2146 (*thrd_last_action)[uninit_id] = uninit;
2148 if (act->is_fence() && act->is_release()) {
2149 if ((int)thrd_last_fence_release->size() <= tid)
2150 thrd_last_fence_release->resize(get_num_threads());
2151 (*thrd_last_fence_release)[tid] = act;
2154 if (act->is_wait()) {
2155 void *mutex_loc = (void *) act->get_value();
2156 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2158 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2159 if (tid >= (int)vec->size())
2160 vec->resize(priv->next_thread_id);
2161 (*vec)[tid].push_back(act);
2166 * @brief Get the last action performed by a particular Thread
2167 * @param tid The thread ID of the Thread in question
2168 * @return The last action in the thread
2170 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2172 int threadid = id_to_int(tid);
2173 if (threadid < (int)thrd_last_action->size())
2174 return (*thrd_last_action)[id_to_int(tid)];
2180 * @brief Get the last fence release performed by a particular Thread
2181 * @param tid The thread ID of the Thread in question
2182 * @return The last fence release in the thread, if one exists; NULL otherwise
2184 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2186 int threadid = id_to_int(tid);
2187 if (threadid < (int)thrd_last_fence_release->size())
2188 return (*thrd_last_fence_release)[id_to_int(tid)];
2194 * Gets the last memory_order_seq_cst write (in the total global sequence)
2195 * performed on a particular object (i.e., memory location), not including the
2197 * @param curr The current ModelAction; also denotes the object location to
2199 * @return The last seq_cst write
2201 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2203 void *location = curr->get_location();
2204 action_list_t *list = get_safe_ptr_action(obj_map, location);
2205 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2206 action_list_t::reverse_iterator rit;
2207 for (rit = list->rbegin(); rit != list->rend(); rit++)
2208 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2214 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2215 * performed in a particular thread, prior to a particular fence.
2216 * @param tid The ID of the thread to check
2217 * @param before_fence The fence from which to begin the search; if NULL, then
2218 * search for the most recent fence in the thread.
2219 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2221 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2223 /* All fences should have NULL location */
2224 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2225 action_list_t::reverse_iterator rit = list->rbegin();
2228 for (; rit != list->rend(); rit++)
2229 if (*rit == before_fence)
2232 ASSERT(*rit == before_fence);
2236 for (; rit != list->rend(); rit++)
2237 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2243 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2244 * location). This function identifies the mutex according to the current
2245 * action, which is presumed to perform on the same mutex.
2246 * @param curr The current ModelAction; also denotes the object location to
2248 * @return The last unlock operation
2250 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2252 void *location = curr->get_location();
2253 action_list_t *list = get_safe_ptr_action(obj_map, location);
2254 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2255 action_list_t::reverse_iterator rit;
2256 for (rit = list->rbegin(); rit != list->rend(); rit++)
2257 if ((*rit)->is_unlock() || (*rit)->is_wait())
2262 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2264 ModelAction *parent = get_last_action(tid);
2266 parent = get_thread(tid)->get_creation();
2271 * Returns the clock vector for a given thread.
2272 * @param tid The thread whose clock vector we want
2273 * @return Desired clock vector
2275 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2277 return get_parent_action(tid)->get_cv();
2281 * Resolve a set of Promises with a current write. The set is provided in the
2282 * Node corresponding to @a write.
2283 * @param write The ModelAction that is fulfilling Promises
2284 * @return True if promises were resolved; false otherwise
2286 bool ModelChecker::resolve_promises(ModelAction *write)
2288 bool haveResolved = false;
2289 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2290 promise_list_t mustResolve, resolved;
2292 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2293 Promise *promise = (*promises)[promise_index];
2294 if (write->get_node()->get_promise(i)) {
2295 ModelAction *read = promise->get_action();
2296 read_from(read, write);
2297 //Make sure the promise's value matches the write's value
2298 ASSERT(promise->is_compatible(write));
2299 mo_graph->resolvePromise(read, write, &mustResolve);
2301 resolved.push_back(promise);
2302 promises->erase(promises->begin() + promise_index);
2303 actions_to_check.push_back(read);
2305 haveResolved = true;
2310 for (unsigned int i = 0; i < mustResolve.size(); i++) {
2311 if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
2313 priv->failed_promise = true;
2315 for (unsigned int i = 0; i < resolved.size(); i++)
2317 //Check whether reading these writes has made threads unable to
2320 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2321 ModelAction *read = actions_to_check[i];
2322 mo_check_promises(read, true);
2325 return haveResolved;
2329 * Compute the set of promises that could potentially be satisfied by this
2330 * action. Note that the set computation actually appears in the Node, not in
2332 * @param curr The ModelAction that may satisfy promises
2334 void ModelChecker::compute_promises(ModelAction *curr)
2336 for (unsigned int i = 0; i < promises->size(); i++) {
2337 Promise *promise = (*promises)[i];
2338 const ModelAction *act = promise->get_action();
2339 if (!act->happens_before(curr) &&
2341 !act->could_synchronize_with(curr) &&
2342 !act->same_thread(curr) &&
2343 act->get_location() == curr->get_location() &&
2344 promise->get_value() == curr->get_value()) {
2345 curr->get_node()->set_promise(i, act->is_rmw());
2350 /** Checks promises in response to change in ClockVector Threads. */
2351 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2353 for (unsigned int i = 0; i < promises->size(); i++) {
2354 Promise *promise = (*promises)[i];
2355 const ModelAction *act = promise->get_action();
2356 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2357 merge_cv->synchronized_since(act)) {
2358 if (promise->eliminate_thread(tid)) {
2359 //Promise has failed
2360 priv->failed_promise = true;
2367 void ModelChecker::check_promises_thread_disabled()
2369 for (unsigned int i = 0; i < promises->size(); i++) {
2370 Promise *promise = (*promises)[i];
2371 if (promise->has_failed()) {
2372 priv->failed_promise = true;
2379 * @brief Checks promises in response to addition to modification order for
2382 * We test whether threads are still available for satisfying promises after an
2383 * addition to our modification order constraints. Those that are unavailable
2384 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2385 * that promise has failed.
2387 * @param act The ModelAction which updated the modification order
2388 * @param is_read_check Should be true if act is a read and we must check for
2389 * updates to the store from which it read (there is a distinction here for
2390 * RMW's, which are both a load and a store)
2392 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2394 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2396 for (unsigned int i = 0; i < promises->size(); i++) {
2397 Promise *promise = (*promises)[i];
2398 const ModelAction *pread = promise->get_action();
2400 // Is this promise on the same location?
2401 if (!pread->same_var(write))
2404 if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
2405 priv->failed_promise = true;
2409 // Don't do any lookups twice for the same thread
2410 if (!promise->thread_is_available(act->get_tid()))
2413 if (mo_graph->checkReachable(promise, write)) {
2414 if (mo_graph->checkPromise(write, promise)) {
2415 priv->failed_promise = true;
2423 * Compute the set of writes that may break the current pending release
2424 * sequence. This information is extracted from previou release sequence
2427 * @param curr The current ModelAction. Must be a release sequence fixup
2430 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2432 if (pending_rel_seqs->empty())
2435 struct release_seq *pending = pending_rel_seqs->back();
2436 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2437 const ModelAction *write = pending->writes[i];
2438 curr->get_node()->add_relseq_break(write);
2441 /* NULL means don't break the sequence; just synchronize */
2442 curr->get_node()->add_relseq_break(NULL);
2446 * Build up an initial set of all past writes that this 'read' action may read
2447 * from. This set is determined by the clock vector's "happens before"
2449 * @param curr is the current ModelAction that we are exploring; it must be a
2452 void ModelChecker::build_reads_from_past(ModelAction *curr)
2454 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2456 ASSERT(curr->is_read());
2458 ModelAction *last_sc_write = NULL;
2460 if (curr->is_seqcst())
2461 last_sc_write = get_last_seq_cst_write(curr);
2463 /* Iterate over all threads */
2464 for (i = 0; i < thrd_lists->size(); i++) {
2465 /* Iterate over actions in thread, starting from most recent */
2466 action_list_t *list = &(*thrd_lists)[i];
2467 action_list_t::reverse_iterator rit;
2468 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2469 ModelAction *act = *rit;
2471 /* Only consider 'write' actions */
2472 if (!act->is_write() || act == curr)
2475 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2476 bool allow_read = true;
2478 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2480 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2484 /* Only add feasible reads */
2485 mo_graph->startChanges();
2486 r_modification_order(curr, act);
2487 if (!is_infeasible())
2488 curr->get_node()->add_read_from(act);
2489 mo_graph->rollbackChanges();
2492 /* Include at most one act per-thread that "happens before" curr */
2493 if (act->happens_before(curr))
2497 /* We may find no valid may-read-from only if the execution is doomed */
2498 if (!curr->get_node()->get_read_from_size()) {
2499 priv->no_valid_reads = true;
2503 if (DBG_ENABLED()) {
2504 model_print("Reached read action:\n");
2506 model_print("Printing may_read_from\n");
2507 curr->get_node()->print_may_read_from();
2508 model_print("End printing may_read_from\n");
2512 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2515 /* UNINIT actions don't have a Node, and they never sleep */
2516 if (write->is_uninitialized())
2518 Node *prevnode = write->get_node()->get_parent();
2520 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2521 if (write->is_release() && thread_sleep)
2523 if (!write->is_rmw()) {
2526 if (write->get_reads_from() == NULL)
2528 write = write->get_reads_from();
2533 * @brief Create a new action representing an uninitialized atomic
2534 * @param location The memory location of the atomic object
2535 * @return A pointer to a new ModelAction
2537 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2539 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2540 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2541 act->create_cv(NULL);
2545 static void print_list(action_list_t *list)
2547 action_list_t::iterator it;
2549 model_print("---------------------------------------------------------------------\n");
2551 unsigned int hash = 0;
2553 for (it = list->begin(); it != list->end(); it++) {
2555 hash = hash^(hash<<3)^((*it)->hash());
2557 model_print("HASH %u\n", hash);
2558 model_print("---------------------------------------------------------------------\n");
2561 #if SUPPORT_MOD_ORDER_DUMP
2562 void ModelChecker::dumpGraph(char *filename) const
2565 sprintf(buffer, "%s.dot", filename);
2566 FILE *file = fopen(buffer, "w");
2567 fprintf(file, "digraph %s {\n", filename);
2568 mo_graph->dumpNodes(file);
2569 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2571 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2572 ModelAction *action = *it;
2573 if (action->is_read()) {
2574 fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2575 if (action->get_reads_from() != NULL)
2576 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2578 if (thread_array[action->get_tid()] != NULL) {
2579 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2582 thread_array[action->get_tid()] = action;
2584 fprintf(file, "}\n");
2585 model_free(thread_array);
2590 /** @brief Prints an execution trace summary. */
2591 void ModelChecker::print_summary() const
2593 #if SUPPORT_MOD_ORDER_DUMP
2594 char buffername[100];
2595 sprintf(buffername, "exec%04u", stats.num_total);
2596 mo_graph->dumpGraphToFile(buffername);
2597 sprintf(buffername, "graph%04u", stats.num_total);
2598 dumpGraph(buffername);
2601 model_print("Execution %d:", stats.num_total);
2602 if (isfeasibleprefix())
2605 print_infeasibility(" INFEASIBLE");
2606 print_list(action_trace);
2611 * Add a Thread to the system for the first time. Should only be called once
2613 * @param t The Thread to add
2615 void ModelChecker::add_thread(Thread *t)
2617 thread_map->put(id_to_int(t->get_id()), t);
2618 scheduler->add_thread(t);
2622 * Removes a thread from the scheduler.
2623 * @param the thread to remove.
2625 void ModelChecker::remove_thread(Thread *t)
2627 scheduler->remove_thread(t);
2631 * @brief Get a Thread reference by its ID
2632 * @param tid The Thread's ID
2633 * @return A Thread reference
2635 Thread * ModelChecker::get_thread(thread_id_t tid) const
2637 return thread_map->get(id_to_int(tid));
2641 * @brief Get a reference to the Thread in which a ModelAction was executed
2642 * @param act The ModelAction
2643 * @return A Thread reference
2645 Thread * ModelChecker::get_thread(const ModelAction *act) const
2647 return get_thread(act->get_tid());
2651 * @brief Check if a Thread is currently enabled
2652 * @param t The Thread to check
2653 * @return True if the Thread is currently enabled
2655 bool ModelChecker::is_enabled(Thread *t) const
2657 return scheduler->is_enabled(t);
2661 * @brief Check if a Thread is currently enabled
2662 * @param tid The ID of the Thread to check
2663 * @return True if the Thread is currently enabled
2665 bool ModelChecker::is_enabled(thread_id_t tid) const
2667 return scheduler->is_enabled(tid);
2671 * Switch from a user-context to the "master thread" context (a.k.a. system
2672 * context). This switch is made with the intention of exploring a particular
2673 * model-checking action (described by a ModelAction object). Must be called
2674 * from a user-thread context.
2676 * @param act The current action that will be explored. May be NULL only if
2677 * trace is exiting via an assertion (see ModelChecker::set_assert and
2678 * ModelChecker::has_asserted).
2679 * @return Return the value returned by the current action
2681 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2684 Thread *old = thread_current();
2685 ASSERT(!old->get_pending());
2686 old->set_pending(act);
2687 if (Thread::swap(old, &system_context) < 0) {
2688 perror("swap threads");
2691 return old->get_return_value();
2695 * Takes the next step in the execution, if possible.
2696 * @param curr The current step to take
2697 * @return Returns the next Thread to run, if any; NULL if this execution
2700 Thread * ModelChecker::take_step(ModelAction *curr)
2702 Thread *curr_thrd = get_thread(curr);
2703 ASSERT(curr_thrd->get_state() == THREAD_READY);
2705 curr = check_current_action(curr);
2707 /* Infeasible -> don't take any more steps */
2708 if (is_infeasible())
2710 else if (isfeasibleprefix() && have_bug_reports()) {
2715 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2718 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2719 scheduler->remove_thread(curr_thrd);
2721 Thread *next_thrd = get_next_thread(curr);
2722 /* Only ask for the next thread from Scheduler if we haven't chosen one
2725 next_thrd = scheduler->next_thread(next_thrd);
2727 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2728 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2733 /** Wrapper to run the user's main function, with appropriate arguments */
2734 void user_main_wrapper(void *)
2736 user_main(model->params.argc, model->params.argv);
2739 /** @brief Run ModelChecker for the user program */
2740 void ModelChecker::run()
2744 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2749 * Stash next pending action(s) for thread(s). There
2750 * should only need to stash one thread's action--the
2751 * thread which just took a step--plus the first step
2752 * for any newly-created thread
2754 for (unsigned int i = 0; i < get_num_threads(); i++) {
2755 thread_id_t tid = int_to_id(i);
2756 Thread *thr = get_thread(tid);
2757 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
2758 scheduler->next_thread(thr);
2759 Thread::swap(&system_context, thr);
2763 /* Catch assertions from prior take_step or from
2764 * between-ModelAction bugs (e.g., data races) */
2768 /* Consume the next action for a Thread */
2769 ModelAction *curr = t->get_pending();
2770 t->set_pending(NULL);
2771 t = take_step(curr);
2772 } while (t && !t->is_model_thread());
2775 * Launch end-of-execution release sequence fixups only when
2776 * the execution is otherwise feasible AND there are:
2778 * (1) pending release sequences
2779 * (2) pending assertions that could be invalidated by a change
2780 * in clock vectors (i.e., data races)
2781 * (3) no pending promises
2783 while (!pending_rel_seqs->empty() &&
2784 is_feasible_prefix_ignore_relseq() &&
2785 !unrealizedraces.empty()) {
2786 model_print("*** WARNING: release sequence fixup action "
2787 "(%zu pending release seuqence(s)) ***\n",
2788 pending_rel_seqs->size());
2789 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2790 std::memory_order_seq_cst, NULL, VALUE_NONE,
2794 } while (next_execution());