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->is_enabled(t)) {
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);
736 } else if (!second_part_of_rmw) {
737 /* Read from future value */
738 value = curr->get_node()->get_future_value();
739 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
740 curr->set_read_from(NULL);
741 Promise *valuepromise = new Promise(curr, value, expiration);
742 promises->push_back(valuepromise);
744 get_thread(curr)->set_return_value(value);
750 * Processes a lock, trylock, or unlock model action. @param curr is
751 * the read model action to process.
753 * The try lock operation checks whether the lock is taken. If not,
754 * it falls to the normal lock operation case. If so, it returns
757 * The lock operation has already been checked that it is enabled, so
758 * it just grabs the lock and synchronizes with the previous unlock.
760 * The unlock operation has to re-enable all of the threads that are
761 * waiting on the lock.
763 * @return True if synchronization was updated; false otherwise
765 bool ModelChecker::process_mutex(ModelAction *curr)
767 std::mutex *mutex = NULL;
768 struct std::mutex_state *state = NULL;
770 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
771 mutex = (std::mutex *)curr->get_location();
772 state = mutex->get_state();
773 } else if (curr->is_wait()) {
774 mutex = (std::mutex *)curr->get_value();
775 state = mutex->get_state();
778 switch (curr->get_type()) {
779 case ATOMIC_TRYLOCK: {
780 bool success = !state->islocked;
781 curr->set_try_lock(success);
783 get_thread(curr)->set_return_value(0);
786 get_thread(curr)->set_return_value(1);
788 //otherwise fall into the lock case
790 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
791 assert_bug("Lock access before initialization");
792 state->islocked = true;
793 ModelAction *unlock = get_last_unlock(curr);
794 //synchronize with the previous unlock statement
795 if (unlock != NULL) {
796 curr->synchronize_with(unlock);
801 case ATOMIC_UNLOCK: {
803 state->islocked = false;
804 //wake up the other threads
805 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
806 //activate all the waiting threads
807 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
808 scheduler->wake(get_thread(*rit));
815 state->islocked = false;
816 //wake up the other threads
817 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
818 //activate all the waiting threads
819 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
820 scheduler->wake(get_thread(*rit));
823 //check whether we should go to sleep or not...simulate spurious failures
824 if (curr->get_node()->get_misc() == 0) {
825 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
827 scheduler->sleep(get_thread(curr));
831 case ATOMIC_NOTIFY_ALL: {
832 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
833 //activate all the waiting threads
834 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
835 scheduler->wake(get_thread(*rit));
840 case ATOMIC_NOTIFY_ONE: {
841 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
842 int wakeupthread = curr->get_node()->get_misc();
843 action_list_t::iterator it = waiters->begin();
844 advance(it, wakeupthread);
845 scheduler->wake(get_thread(*it));
857 * Process a write ModelAction
858 * @param curr The ModelAction to process
859 * @return True if the mo_graph was updated or promises were resolved
861 bool ModelChecker::process_write(ModelAction *curr)
863 bool updated_mod_order = w_modification_order(curr);
864 bool updated_promises = resolve_promises(curr);
866 if (promises->size() == 0) {
867 for (unsigned int i = 0; i < futurevalues->size(); i++) {
868 struct PendingFutureValue pfv = (*futurevalues)[i];
869 //Do more ambitious checks now that mo is more complete
870 if (mo_may_allow(pfv.writer, pfv.act) &&
871 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number() + params.maxfuturedelay))
872 set_latest_backtrack(pfv.act);
874 futurevalues->resize(0);
877 mo_graph->commitChanges();
878 mo_check_promises(curr->get_tid(), curr);
880 get_thread(curr)->set_return_value(VALUE_NONE);
881 return updated_mod_order || updated_promises;
885 * Process a fence ModelAction
886 * @param curr The ModelAction to process
887 * @return True if synchronization was updated
889 bool ModelChecker::process_fence(ModelAction *curr)
892 * fence-relaxed: no-op
893 * fence-release: only log the occurence (not in this function), for
894 * use in later synchronization
895 * fence-acquire (this function): search for hypothetical release
898 bool updated = false;
899 if (curr->is_acquire()) {
900 action_list_t *list = action_trace;
901 action_list_t::reverse_iterator rit;
902 /* Find X : is_read(X) && X --sb-> curr */
903 for (rit = list->rbegin(); rit != list->rend(); rit++) {
904 ModelAction *act = *rit;
907 if (act->get_tid() != curr->get_tid())
909 /* Stop at the beginning of the thread */
910 if (act->is_thread_start())
912 /* Stop once we reach a prior fence-acquire */
913 if (act->is_fence() && act->is_acquire())
917 /* read-acquire will find its own release sequences */
918 if (act->is_acquire())
921 /* Establish hypothetical release sequences */
922 rel_heads_list_t release_heads;
923 get_release_seq_heads(curr, act, &release_heads);
924 for (unsigned int i = 0; i < release_heads.size(); i++)
925 if (!curr->synchronize_with(release_heads[i]))
926 set_bad_synchronization();
927 if (release_heads.size() != 0)
935 * @brief Process the current action for thread-related activity
937 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
938 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
939 * synchronization, etc. This function is a no-op for non-THREAD actions
940 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
942 * @param curr The current action
943 * @return True if synchronization was updated or a thread completed
945 bool ModelChecker::process_thread_action(ModelAction *curr)
947 bool updated = false;
949 switch (curr->get_type()) {
950 case THREAD_CREATE: {
951 Thread *th = curr->get_thread_operand();
952 th->set_creation(curr);
956 Thread *blocking = curr->get_thread_operand();
957 ModelAction *act = get_last_action(blocking->get_id());
958 curr->synchronize_with(act);
959 updated = true; /* trigger rel-seq checks */
962 case THREAD_FINISH: {
963 Thread *th = get_thread(curr);
964 while (!th->wait_list_empty()) {
965 ModelAction *act = th->pop_wait_list();
966 scheduler->wake(get_thread(act));
969 updated = true; /* trigger rel-seq checks */
973 check_promises(curr->get_tid(), NULL, curr->get_cv());
984 * @brief Process the current action for release sequence fixup activity
986 * Performs model-checker release sequence fixups for the current action,
987 * forcing a single pending release sequence to break (with a given, potential
988 * "loose" write) or to complete (i.e., synchronize). If a pending release
989 * sequence forms a complete release sequence, then we must perform the fixup
990 * synchronization, mo_graph additions, etc.
992 * @param curr The current action; must be a release sequence fixup action
993 * @param work_queue The work queue to which to add work items as they are
996 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
998 const ModelAction *write = curr->get_node()->get_relseq_break();
999 struct release_seq *sequence = pending_rel_seqs->back();
1000 pending_rel_seqs->pop_back();
1002 ModelAction *acquire = sequence->acquire;
1003 const ModelAction *rf = sequence->rf;
1004 const ModelAction *release = sequence->release;
1008 ASSERT(release->same_thread(rf));
1010 if (write == NULL) {
1012 * @todo Forcing a synchronization requires that we set
1013 * modification order constraints. For instance, we can't allow
1014 * a fixup sequence in which two separate read-acquire
1015 * operations read from the same sequence, where the first one
1016 * synchronizes and the other doesn't. Essentially, we can't
1017 * allow any writes to insert themselves between 'release' and
1021 /* Must synchronize */
1022 if (!acquire->synchronize_with(release)) {
1023 set_bad_synchronization();
1026 /* Re-check all pending release sequences */
1027 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1028 /* Re-check act for mo_graph edges */
1029 work_queue->push_back(MOEdgeWorkEntry(acquire));
1031 /* propagate synchronization to later actions */
1032 action_list_t::reverse_iterator rit = action_trace->rbegin();
1033 for (; (*rit) != acquire; rit++) {
1034 ModelAction *propagate = *rit;
1035 if (acquire->happens_before(propagate)) {
1036 propagate->synchronize_with(acquire);
1037 /* Re-check 'propagate' for mo_graph edges */
1038 work_queue->push_back(MOEdgeWorkEntry(propagate));
1042 /* Break release sequence with new edges:
1043 * release --mo--> write --mo--> rf */
1044 mo_graph->addEdge(release, write);
1045 mo_graph->addEdge(write, rf);
1048 /* See if we have realized a data race */
1053 * Initialize the current action by performing one or more of the following
1054 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1055 * in the NodeStack, manipulating backtracking sets, allocating and
1056 * initializing clock vectors, and computing the promises to fulfill.
1058 * @param curr The current action, as passed from the user context; may be
1059 * freed/invalidated after the execution of this function, with a different
1060 * action "returned" its place (pass-by-reference)
1061 * @return True if curr is a newly-explored action; false otherwise
1063 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1065 ModelAction *newcurr;
1067 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1068 newcurr = process_rmw(*curr);
1071 if (newcurr->is_rmw())
1072 compute_promises(newcurr);
1078 (*curr)->set_seq_number(get_next_seq_num());
1080 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1082 /* First restore type and order in case of RMW operation */
1083 if ((*curr)->is_rmwr())
1084 newcurr->copy_typeandorder(*curr);
1086 ASSERT((*curr)->get_location() == newcurr->get_location());
1087 newcurr->copy_from_new(*curr);
1089 /* Discard duplicate ModelAction; use action from NodeStack */
1092 /* Always compute new clock vector */
1093 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1096 return false; /* Action was explored previously */
1100 /* Always compute new clock vector */
1101 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1103 /* Assign most recent release fence */
1104 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1107 * Perform one-time actions when pushing new ModelAction onto
1110 if (newcurr->is_write())
1111 compute_promises(newcurr);
1112 else if (newcurr->is_relseq_fixup())
1113 compute_relseq_breakwrites(newcurr);
1114 else if (newcurr->is_wait())
1115 newcurr->get_node()->set_misc_max(2);
1116 else if (newcurr->is_notify_one()) {
1117 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1119 return true; /* This was a new ModelAction */
1124 * @brief Establish reads-from relation between two actions
1126 * Perform basic operations involved with establishing a concrete rf relation,
1127 * including setting the ModelAction data and checking for release sequences.
1129 * @param act The action that is reading (must be a read)
1130 * @param rf The action from which we are reading (must be a write)
1132 * @return True if this read established synchronization
1134 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1136 act->set_read_from(rf);
1137 if (rf != NULL && act->is_acquire()) {
1138 rel_heads_list_t release_heads;
1139 get_release_seq_heads(act, act, &release_heads);
1140 int num_heads = release_heads.size();
1141 for (unsigned int i = 0; i < release_heads.size(); i++)
1142 if (!act->synchronize_with(release_heads[i])) {
1143 set_bad_synchronization();
1146 return num_heads > 0;
1152 * @brief Check whether a model action is enabled.
1154 * Checks whether a lock or join operation would be successful (i.e., is the
1155 * lock already locked, or is the joined thread already complete). If not, put
1156 * the action in a waiter list.
1158 * @param curr is the ModelAction to check whether it is enabled.
1159 * @return a bool that indicates whether the action is enabled.
1161 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1162 if (curr->is_lock()) {
1163 std::mutex *lock = (std::mutex *)curr->get_location();
1164 struct std::mutex_state *state = lock->get_state();
1165 if (state->islocked) {
1166 //Stick the action in the appropriate waiting queue
1167 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1170 } else if (curr->get_type() == THREAD_JOIN) {
1171 Thread *blocking = (Thread *)curr->get_location();
1172 if (!blocking->is_complete()) {
1173 blocking->push_wait_list(curr);
1182 * Stores the ModelAction for the current thread action. Call this
1183 * immediately before switching from user- to system-context to pass
1184 * data between them.
1185 * @param act The ModelAction created by the user-thread action
1187 void ModelChecker::set_current_action(ModelAction *act) {
1188 priv->current_action = act;
1192 * This is the heart of the model checker routine. It performs model-checking
1193 * actions corresponding to a given "current action." Among other processes, it
1194 * calculates reads-from relationships, updates synchronization clock vectors,
1195 * forms a memory_order constraints graph, and handles replay/backtrack
1196 * execution when running permutations of previously-observed executions.
1198 * @param curr The current action to process
1199 * @return The ModelAction that is actually executed; may be different than
1200 * curr; may be NULL, if the current action is not enabled to run
1202 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1205 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1207 if (!check_action_enabled(curr)) {
1208 /* Make the execution look like we chose to run this action
1209 * much later, when a lock/join can succeed */
1210 get_thread(curr)->set_pending(curr);
1211 scheduler->sleep(get_thread(curr));
1215 bool newly_explored = initialize_curr_action(&curr);
1221 wake_up_sleeping_actions(curr);
1223 /* Add the action to lists before any other model-checking tasks */
1224 if (!second_part_of_rmw)
1225 add_action_to_lists(curr);
1227 /* Build may_read_from set for newly-created actions */
1228 if (newly_explored && curr->is_read())
1229 build_reads_from_past(curr);
1231 /* Initialize work_queue with the "current action" work */
1232 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1233 while (!work_queue.empty() && !has_asserted()) {
1234 WorkQueueEntry work = work_queue.front();
1235 work_queue.pop_front();
1237 switch (work.type) {
1238 case WORK_CHECK_CURR_ACTION: {
1239 ModelAction *act = work.action;
1240 bool update = false; /* update this location's release seq's */
1241 bool update_all = false; /* update all release seq's */
1243 if (process_thread_action(curr))
1246 if (act->is_read() && process_read(act, second_part_of_rmw))
1249 if (act->is_write() && process_write(act))
1252 if (act->is_fence() && process_fence(act))
1255 if (act->is_mutex_op() && process_mutex(act))
1258 if (act->is_relseq_fixup())
1259 process_relseq_fixup(curr, &work_queue);
1262 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1264 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1267 case WORK_CHECK_RELEASE_SEQ:
1268 resolve_release_sequences(work.location, &work_queue);
1270 case WORK_CHECK_MO_EDGES: {
1271 /** @todo Complete verification of work_queue */
1272 ModelAction *act = work.action;
1273 bool updated = false;
1275 if (act->is_read()) {
1276 const ModelAction *rf = act->get_reads_from();
1277 if (rf != NULL && r_modification_order(act, rf))
1280 if (act->is_write()) {
1281 if (w_modification_order(act))
1284 mo_graph->commitChanges();
1287 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1296 check_curr_backtracking(curr);
1297 set_backtracking(curr);
1301 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1303 Node *currnode = curr->get_node();
1304 Node *parnode = currnode->get_parent();
1306 if ((parnode && !parnode->backtrack_empty()) ||
1307 !currnode->misc_empty() ||
1308 !currnode->read_from_empty() ||
1309 !currnode->future_value_empty() ||
1310 !currnode->promise_empty() ||
1311 !currnode->relseq_break_empty()) {
1312 set_latest_backtrack(curr);
1316 bool ModelChecker::promises_expired() const
1318 for (unsigned int i = 0; i < promises->size(); i++) {
1319 Promise *promise = (*promises)[i];
1320 if (promise->get_expiration() < priv->used_sequence_numbers)
1327 * This is the strongest feasibility check available.
1328 * @return whether the current trace (partial or complete) must be a prefix of
1331 bool ModelChecker::isfeasibleprefix() const
1333 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1337 * Returns whether the current completed trace is feasible, except for pending
1338 * release sequences.
1340 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1342 if (DBG_ENABLED() && promises->size() != 0)
1343 DEBUG("Infeasible: unrevolved promises\n");
1345 return !is_infeasible() && promises->size() == 0;
1349 * Check if the current partial trace is infeasible. Does not check any
1350 * end-of-execution flags, which might rule out the execution. Thus, this is
1351 * useful only for ruling an execution as infeasible.
1352 * @return whether the current partial trace is infeasible.
1354 bool ModelChecker::is_infeasible() const
1356 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1357 DEBUG("Infeasible: RMW violation\n");
1359 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1363 * Check If the current partial trace is infeasible, while ignoring
1364 * infeasibility related to 2 RMW's reading from the same store. It does not
1365 * check end-of-execution feasibility.
1366 * @see ModelChecker::is_infeasible
1367 * @return whether the current partial trace is infeasible, ignoring multiple
1368 * RMWs reading from the same store.
1370 bool ModelChecker::is_infeasible_ignoreRMW() const
1372 if (DBG_ENABLED()) {
1373 if (mo_graph->checkForCycles())
1374 DEBUG("Infeasible: modification order cycles\n");
1375 if (priv->failed_promise)
1376 DEBUG("Infeasible: failed promise\n");
1377 if (priv->too_many_reads)
1378 DEBUG("Infeasible: too many reads\n");
1379 if (priv->bad_synchronization)
1380 DEBUG("Infeasible: bad synchronization ordering\n");
1381 if (promises_expired())
1382 DEBUG("Infeasible: promises expired\n");
1384 return mo_graph->checkForCycles() || priv->failed_promise ||
1385 priv->too_many_reads || priv->bad_synchronization ||
1389 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1390 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1391 ModelAction *lastread = get_last_action(act->get_tid());
1392 lastread->process_rmw(act);
1393 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1394 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1395 mo_graph->commitChanges();
1401 * Checks whether a thread has read from the same write for too many times
1402 * without seeing the effects of a later write.
1405 * 1) there must a different write that we could read from that would satisfy the modification order,
1406 * 2) we must have read from the same value in excess of maxreads times, and
1407 * 3) that other write must have been in the reads_from set for maxreads times.
1409 * If so, we decide that the execution is no longer feasible.
1411 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1413 if (params.maxreads != 0) {
1414 if (curr->get_node()->get_read_from_size() <= 1)
1416 //Must make sure that execution is currently feasible... We could
1417 //accidentally clear by rolling back
1418 if (is_infeasible())
1420 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1421 int tid = id_to_int(curr->get_tid());
1424 if ((int)thrd_lists->size() <= tid)
1426 action_list_t *list = &(*thrd_lists)[tid];
1428 action_list_t::reverse_iterator rit = list->rbegin();
1429 /* Skip past curr */
1430 for (; (*rit) != curr; rit++)
1432 /* go past curr now */
1435 action_list_t::reverse_iterator ritcopy = rit;
1436 //See if we have enough reads from the same value
1438 for (; count < params.maxreads; rit++, count++) {
1439 if (rit == list->rend())
1441 ModelAction *act = *rit;
1442 if (!act->is_read())
1445 if (act->get_reads_from() != rf)
1447 if (act->get_node()->get_read_from_size() <= 1)
1450 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1452 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1454 /* Need a different write */
1458 /* Test to see whether this is a feasible write to read from */
1459 mo_graph->startChanges();
1460 r_modification_order(curr, write);
1461 bool feasiblereadfrom = !is_infeasible();
1462 mo_graph->rollbackChanges();
1464 if (!feasiblereadfrom)
1468 bool feasiblewrite = true;
1469 //new we need to see if this write works for everyone
1471 for (int loop = count; loop > 0; loop--, rit++) {
1472 ModelAction *act = *rit;
1473 bool foundvalue = false;
1474 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1475 if (act->get_node()->get_read_from_at(j) == write) {
1481 feasiblewrite = false;
1485 if (feasiblewrite) {
1486 priv->too_many_reads = true;
1494 * Updates the mo_graph with the constraints imposed from the current
1497 * Basic idea is the following: Go through each other thread and find
1498 * the lastest action that happened before our read. Two cases:
1500 * (1) The action is a write => that write must either occur before
1501 * the write we read from or be the write we read from.
1503 * (2) The action is a read => the write that that action read from
1504 * must occur before the write we read from or be the same write.
1506 * @param curr The current action. Must be a read.
1507 * @param rf The action that curr reads from. Must be a write.
1508 * @return True if modification order edges were added; false otherwise
1510 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1512 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1515 ASSERT(curr->is_read());
1517 /* Last SC fence in the current thread */
1518 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1520 /* Iterate over all threads */
1521 for (i = 0; i < thrd_lists->size(); i++) {
1522 /* Last SC fence in thread i */
1523 ModelAction *last_sc_fence_thread_local = NULL;
1524 if (int_to_id((int)i) != curr->get_tid())
1525 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1527 /* Last SC fence in thread i, before last SC fence in current thread */
1528 ModelAction *last_sc_fence_thread_before = NULL;
1529 if (last_sc_fence_local)
1530 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1532 /* Iterate over actions in thread, starting from most recent */
1533 action_list_t *list = &(*thrd_lists)[i];
1534 action_list_t::reverse_iterator rit;
1535 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1536 ModelAction *act = *rit;
1538 if (act->is_write() && act != rf && act != curr) {
1539 /* C++, Section 29.3 statement 5 */
1540 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1541 *act < *last_sc_fence_thread_local) {
1542 mo_graph->addEdge(act, rf);
1546 /* C++, Section 29.3 statement 4 */
1547 else if (act->is_seqcst() && last_sc_fence_local &&
1548 *act < *last_sc_fence_local) {
1549 mo_graph->addEdge(act, rf);
1553 /* C++, Section 29.3 statement 6 */
1554 else if (last_sc_fence_thread_before &&
1555 *act < *last_sc_fence_thread_before) {
1556 mo_graph->addEdge(act, rf);
1563 * Include at most one act per-thread that "happens
1564 * before" curr. Don't consider reflexively.
1566 if (act->happens_before(curr) && act != curr) {
1567 if (act->is_write()) {
1569 mo_graph->addEdge(act, rf);
1573 const ModelAction *prevreadfrom = act->get_reads_from();
1574 //if the previous read is unresolved, keep going...
1575 if (prevreadfrom == NULL)
1578 if (rf != prevreadfrom) {
1579 mo_graph->addEdge(prevreadfrom, rf);
1591 /** This method fixes up the modification order when we resolve a
1592 * promises. The basic problem is that actions that occur after the
1593 * read curr could not property add items to the modification order
1596 * So for each thread, we find the earliest item that happens after
1597 * the read curr. This is the item we have to fix up with additional
1598 * constraints. If that action is write, we add a MO edge between
1599 * the Action rf and that action. If the action is a read, we add a
1600 * MO edge between the Action rf, and whatever the read accessed.
1602 * @param curr is the read ModelAction that we are fixing up MO edges for.
1603 * @param rf is the write ModelAction that curr reads from.
1606 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1608 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1610 ASSERT(curr->is_read());
1612 /* Iterate over all threads */
1613 for (i = 0; i < thrd_lists->size(); i++) {
1614 /* Iterate over actions in thread, starting from most recent */
1615 action_list_t *list = &(*thrd_lists)[i];
1616 action_list_t::reverse_iterator rit;
1617 ModelAction *lastact = NULL;
1619 /* Find last action that happens after curr that is either not curr or a rmw */
1620 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1621 ModelAction *act = *rit;
1622 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1628 /* Include at most one act per-thread that "happens before" curr */
1629 if (lastact != NULL) {
1630 if (lastact == curr) {
1631 //Case 1: The resolved read is a RMW, and we need to make sure
1632 //that the write portion of the RMW mod order after rf
1634 mo_graph->addEdge(rf, lastact);
1635 } else if (lastact->is_read()) {
1636 //Case 2: The resolved read is a normal read and the next
1637 //operation is a read, and we need to make sure the value read
1638 //is mod ordered after rf
1640 const ModelAction *postreadfrom = lastact->get_reads_from();
1641 if (postreadfrom != NULL && rf != postreadfrom)
1642 mo_graph->addEdge(rf, postreadfrom);
1644 //Case 3: The resolved read is a normal read and the next
1645 //operation is a write, and we need to make sure that the
1646 //write is mod ordered after rf
1648 mo_graph->addEdge(rf, lastact);
1656 * Updates the mo_graph with the constraints imposed from the current write.
1658 * Basic idea is the following: Go through each other thread and find
1659 * the lastest action that happened before our write. Two cases:
1661 * (1) The action is a write => that write must occur before
1664 * (2) The action is a read => the write that that action read from
1665 * must occur before the current write.
1667 * This method also handles two other issues:
1669 * (I) Sequential Consistency: Making sure that if the current write is
1670 * seq_cst, that it occurs after the previous seq_cst write.
1672 * (II) Sending the write back to non-synchronizing reads.
1674 * @param curr The current action. Must be a write.
1675 * @return True if modification order edges were added; false otherwise
1677 bool ModelChecker::w_modification_order(ModelAction *curr)
1679 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1682 ASSERT(curr->is_write());
1684 if (curr->is_seqcst()) {
1685 /* We have to at least see the last sequentially consistent write,
1686 so we are initialized. */
1687 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1688 if (last_seq_cst != NULL) {
1689 mo_graph->addEdge(last_seq_cst, curr);
1694 /* Last SC fence in the current thread */
1695 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1697 /* Iterate over all threads */
1698 for (i = 0; i < thrd_lists->size(); i++) {
1699 /* Last SC fence in thread i, before last SC fence in current thread */
1700 ModelAction *last_sc_fence_thread_before = NULL;
1701 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1702 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1704 /* Iterate over actions in thread, starting from most recent */
1705 action_list_t *list = &(*thrd_lists)[i];
1706 action_list_t::reverse_iterator rit;
1707 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1708 ModelAction *act = *rit;
1711 * 1) If RMW and it actually read from something, then we
1712 * already have all relevant edges, so just skip to next
1715 * 2) If RMW and it didn't read from anything, we should
1716 * whatever edge we can get to speed up convergence.
1718 * 3) If normal write, we need to look at earlier actions, so
1719 * continue processing list.
1721 if (curr->is_rmw()) {
1722 if (curr->get_reads_from() != NULL)
1730 /* C++, Section 29.3 statement 7 */
1731 if (last_sc_fence_thread_before && act->is_write() &&
1732 *act < *last_sc_fence_thread_before) {
1733 mo_graph->addEdge(act, curr);
1739 * Include at most one act per-thread that "happens
1742 if (act->happens_before(curr)) {
1744 * Note: if act is RMW, just add edge:
1746 * The following edge should be handled elsewhere:
1747 * readfrom(act) --mo--> act
1749 if (act->is_write())
1750 mo_graph->addEdge(act, curr);
1751 else if (act->is_read()) {
1752 //if previous read accessed a null, just keep going
1753 if (act->get_reads_from() == NULL)
1755 mo_graph->addEdge(act->get_reads_from(), curr);
1759 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1760 !act->same_thread(curr)) {
1761 /* We have an action that:
1762 (1) did not happen before us
1763 (2) is a read and we are a write
1764 (3) cannot synchronize with us
1765 (4) is in a different thread
1767 that read could potentially read from our write. Note that
1768 these checks are overly conservative at this point, we'll
1769 do more checks before actually removing the
1773 if (thin_air_constraint_may_allow(curr, act)) {
1774 if (!is_infeasible() ||
1775 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1776 struct PendingFutureValue pfv = {curr, act};
1777 futurevalues->push_back(pfv);
1787 /** Arbitrary reads from the future are not allowed. Section 29.3
1788 * part 9 places some constraints. This method checks one result of constraint
1789 * constraint. Others require compiler support. */
1790 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1792 if (!writer->is_rmw())
1795 if (!reader->is_rmw())
1798 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1799 if (search == reader)
1801 if (search->get_tid() == reader->get_tid() &&
1802 search->happens_before(reader))
1810 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1811 * some constraints. This method checks one the following constraint (others
1812 * require compiler support):
1814 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1816 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1818 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1820 /* Iterate over all threads */
1821 for (i = 0; i < thrd_lists->size(); i++) {
1822 const ModelAction *write_after_read = NULL;
1824 /* Iterate over actions in thread, starting from most recent */
1825 action_list_t *list = &(*thrd_lists)[i];
1826 action_list_t::reverse_iterator rit;
1827 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1828 ModelAction *act = *rit;
1830 /* Don't disallow due to act == reader */
1831 if (!reader->happens_before(act) || reader == act)
1833 else if (act->is_write())
1834 write_after_read = act;
1835 else if (act->is_read() && act->get_reads_from() != NULL)
1836 write_after_read = act->get_reads_from();
1839 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1846 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1847 * The ModelAction under consideration is expected to be taking part in
1848 * release/acquire synchronization as an object of the "reads from" relation.
1849 * Note that this can only provide release sequence support for RMW chains
1850 * which do not read from the future, as those actions cannot be traced until
1851 * their "promise" is fulfilled. Similarly, we may not even establish the
1852 * presence of a release sequence with certainty, as some modification order
1853 * constraints may be decided further in the future. Thus, this function
1854 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1855 * and a boolean representing certainty.
1857 * @param rf The action that might be part of a release sequence. Must be a
1859 * @param release_heads A pass-by-reference style return parameter. After
1860 * execution of this function, release_heads will contain the heads of all the
1861 * relevant release sequences, if any exists with certainty
1862 * @param pending A pass-by-reference style return parameter which is only used
1863 * when returning false (i.e., uncertain). Returns most information regarding
1864 * an uncertain release sequence, including any write operations that might
1865 * break the sequence.
1866 * @return true, if the ModelChecker is certain that release_heads is complete;
1869 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1870 rel_heads_list_t *release_heads,
1871 struct release_seq *pending) const
1873 /* Only check for release sequences if there are no cycles */
1874 if (mo_graph->checkForCycles())
1878 ASSERT(rf->is_write());
1880 if (rf->is_release())
1881 release_heads->push_back(rf);
1882 else if (rf->get_last_fence_release())
1883 release_heads->push_back(rf->get_last_fence_release());
1885 break; /* End of RMW chain */
1887 /** @todo Need to be smarter here... In the linux lock
1888 * example, this will run to the beginning of the program for
1890 /** @todo The way to be smarter here is to keep going until 1
1891 * thread has a release preceded by an acquire and you've seen
1894 /* acq_rel RMW is a sufficient stopping condition */
1895 if (rf->is_acquire() && rf->is_release())
1896 return true; /* complete */
1898 rf = rf->get_reads_from();
1901 /* read from future: need to settle this later */
1903 return false; /* incomplete */
1906 if (rf->is_release())
1907 return true; /* complete */
1909 /* else relaxed write
1910 * - check for fence-release in the same thread (29.8, stmt. 3)
1911 * - check modification order for contiguous subsequence
1912 * -> rf must be same thread as release */
1914 const ModelAction *fence_release = rf->get_last_fence_release();
1915 /* Synchronize with a fence-release unconditionally; we don't need to
1916 * find any more "contiguous subsequence..." for it */
1918 release_heads->push_back(fence_release);
1920 int tid = id_to_int(rf->get_tid());
1921 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1922 action_list_t *list = &(*thrd_lists)[tid];
1923 action_list_t::const_reverse_iterator rit;
1925 /* Find rf in the thread list */
1926 rit = std::find(list->rbegin(), list->rend(), rf);
1927 ASSERT(rit != list->rend());
1929 /* Find the last {write,fence}-release */
1930 for (; rit != list->rend(); rit++) {
1931 if (fence_release && *(*rit) < *fence_release)
1933 if ((*rit)->is_release())
1936 if (rit == list->rend()) {
1937 /* No write-release in this thread */
1938 return true; /* complete */
1939 } else if (fence_release && *(*rit) < *fence_release) {
1940 /* The fence-release is more recent (and so, "stronger") than
1941 * the most recent write-release */
1942 return true; /* complete */
1943 } /* else, need to establish contiguous release sequence */
1944 ModelAction *release = *rit;
1946 ASSERT(rf->same_thread(release));
1948 pending->writes.clear();
1950 bool certain = true;
1951 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1952 if (id_to_int(rf->get_tid()) == (int)i)
1954 list = &(*thrd_lists)[i];
1956 /* Can we ensure no future writes from this thread may break
1957 * the release seq? */
1958 bool future_ordered = false;
1960 ModelAction *last = get_last_action(int_to_id(i));
1961 Thread *th = get_thread(int_to_id(i));
1962 if ((last && rf->happens_before(last)) ||
1965 future_ordered = true;
1967 ASSERT(!th->is_model_thread() || future_ordered);
1969 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1970 const ModelAction *act = *rit;
1971 /* Reach synchronization -> this thread is complete */
1972 if (act->happens_before(release))
1974 if (rf->happens_before(act)) {
1975 future_ordered = true;
1979 /* Only non-RMW writes can break release sequences */
1980 if (!act->is_write() || act->is_rmw())
1983 /* Check modification order */
1984 if (mo_graph->checkReachable(rf, act)) {
1985 /* rf --mo--> act */
1986 future_ordered = true;
1989 if (mo_graph->checkReachable(act, release))
1990 /* act --mo--> release */
1992 if (mo_graph->checkReachable(release, act) &&
1993 mo_graph->checkReachable(act, rf)) {
1994 /* release --mo-> act --mo--> rf */
1995 return true; /* complete */
1997 /* act may break release sequence */
1998 pending->writes.push_back(act);
2001 if (!future_ordered)
2002 certain = false; /* This thread is uncertain */
2006 release_heads->push_back(release);
2007 pending->writes.clear();
2009 pending->release = release;
2016 * An interface for getting the release sequence head(s) with which a
2017 * given ModelAction must synchronize. This function only returns a non-empty
2018 * result when it can locate a release sequence head with certainty. Otherwise,
2019 * it may mark the internal state of the ModelChecker so that it will handle
2020 * the release sequence at a later time, causing @a acquire to update its
2021 * synchronization at some later point in execution.
2023 * @param acquire The 'acquire' action that may synchronize with a release
2025 * @param read The read action that may read from a release sequence; this may
2026 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2027 * when 'acquire' is a fence-acquire)
2028 * @param release_heads A pass-by-reference return parameter. Will be filled
2029 * with the head(s) of the release sequence(s), if they exists with certainty.
2030 * @see ModelChecker::release_seq_heads
2032 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2033 ModelAction *read, rel_heads_list_t *release_heads)
2035 const ModelAction *rf = read->get_reads_from();
2036 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2037 sequence->acquire = acquire;
2038 sequence->read = read;
2040 if (!release_seq_heads(rf, release_heads, sequence)) {
2041 /* add act to 'lazy checking' list */
2042 pending_rel_seqs->push_back(sequence);
2044 snapshot_free(sequence);
2049 * Attempt to resolve all stashed operations that might synchronize with a
2050 * release sequence for a given location. This implements the "lazy" portion of
2051 * determining whether or not a release sequence was contiguous, since not all
2052 * modification order information is present at the time an action occurs.
2054 * @param location The location/object that should be checked for release
2055 * sequence resolutions. A NULL value means to check all locations.
2056 * @param work_queue The work queue to which to add work items as they are
2058 * @return True if any updates occurred (new synchronization, new mo_graph
2061 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2063 bool updated = false;
2064 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2065 while (it != pending_rel_seqs->end()) {
2066 struct release_seq *pending = *it;
2067 ModelAction *acquire = pending->acquire;
2068 const ModelAction *read = pending->read;
2070 /* Only resolve sequences on the given location, if provided */
2071 if (location && read->get_location() != location) {
2076 const ModelAction *rf = read->get_reads_from();
2077 rel_heads_list_t release_heads;
2079 complete = release_seq_heads(rf, &release_heads, pending);
2080 for (unsigned int i = 0; i < release_heads.size(); i++) {
2081 if (!acquire->has_synchronized_with(release_heads[i])) {
2082 if (acquire->synchronize_with(release_heads[i]))
2085 set_bad_synchronization();
2090 /* Re-check all pending release sequences */
2091 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2092 /* Re-check read-acquire for mo_graph edges */
2093 if (acquire->is_read())
2094 work_queue->push_back(MOEdgeWorkEntry(acquire));
2096 /* propagate synchronization to later actions */
2097 action_list_t::reverse_iterator rit = action_trace->rbegin();
2098 for (; (*rit) != acquire; rit++) {
2099 ModelAction *propagate = *rit;
2100 if (acquire->happens_before(propagate)) {
2101 propagate->synchronize_with(acquire);
2102 /* Re-check 'propagate' for mo_graph edges */
2103 work_queue->push_back(MOEdgeWorkEntry(propagate));
2108 it = pending_rel_seqs->erase(it);
2109 snapshot_free(pending);
2115 // If we resolved promises or data races, see if we have realized a data race.
2122 * Performs various bookkeeping operations for the current ModelAction. For
2123 * instance, adds action to the per-object, per-thread action vector and to the
2124 * action trace list of all thread actions.
2126 * @param act is the ModelAction to add.
2128 void ModelChecker::add_action_to_lists(ModelAction *act)
2130 int tid = id_to_int(act->get_tid());
2131 ModelAction *uninit = NULL;
2133 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2134 if (list->empty() && act->is_atomic_var()) {
2135 uninit = new_uninitialized_action(act->get_location());
2136 uninit_id = id_to_int(uninit->get_tid());
2137 list->push_back(uninit);
2139 list->push_back(act);
2141 action_trace->push_back(act);
2143 action_trace->push_front(uninit);
2145 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2146 if (tid >= (int)vec->size())
2147 vec->resize(priv->next_thread_id);
2148 (*vec)[tid].push_back(act);
2150 (*vec)[uninit_id].push_front(uninit);
2152 if ((int)thrd_last_action->size() <= tid)
2153 thrd_last_action->resize(get_num_threads());
2154 (*thrd_last_action)[tid] = act;
2156 (*thrd_last_action)[uninit_id] = uninit;
2158 if (act->is_fence() && act->is_release()) {
2159 if ((int)thrd_last_fence_release->size() <= tid)
2160 thrd_last_fence_release->resize(get_num_threads());
2161 (*thrd_last_fence_release)[tid] = act;
2164 if (act->is_wait()) {
2165 void *mutex_loc = (void *) act->get_value();
2166 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2168 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2169 if (tid >= (int)vec->size())
2170 vec->resize(priv->next_thread_id);
2171 (*vec)[tid].push_back(act);
2176 * @brief Get the last action performed by a particular Thread
2177 * @param tid The thread ID of the Thread in question
2178 * @return The last action in the thread
2180 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2182 int threadid = id_to_int(tid);
2183 if (threadid < (int)thrd_last_action->size())
2184 return (*thrd_last_action)[id_to_int(tid)];
2190 * @brief Get the last fence release performed by a particular Thread
2191 * @param tid The thread ID of the Thread in question
2192 * @return The last fence release in the thread, if one exists; NULL otherwise
2194 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2196 int threadid = id_to_int(tid);
2197 if (threadid < (int)thrd_last_fence_release->size())
2198 return (*thrd_last_fence_release)[id_to_int(tid)];
2204 * Gets the last memory_order_seq_cst write (in the total global sequence)
2205 * performed on a particular object (i.e., memory location), not including the
2207 * @param curr The current ModelAction; also denotes the object location to
2209 * @return The last seq_cst write
2211 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2213 void *location = curr->get_location();
2214 action_list_t *list = get_safe_ptr_action(obj_map, location);
2215 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2216 action_list_t::reverse_iterator rit;
2217 for (rit = list->rbegin(); rit != list->rend(); rit++)
2218 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2224 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2225 * performed in a particular thread, prior to a particular fence.
2226 * @param tid The ID of the thread to check
2227 * @param before_fence The fence from which to begin the search; if NULL, then
2228 * search for the most recent fence in the thread.
2229 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2231 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2233 /* All fences should have NULL location */
2234 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2235 action_list_t::reverse_iterator rit = list->rbegin();
2238 for (; rit != list->rend(); rit++)
2239 if (*rit == before_fence)
2242 ASSERT(*rit == before_fence);
2246 for (; rit != list->rend(); rit++)
2247 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2253 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2254 * location). This function identifies the mutex according to the current
2255 * action, which is presumed to perform on the same mutex.
2256 * @param curr The current ModelAction; also denotes the object location to
2258 * @return The last unlock operation
2260 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2262 void *location = curr->get_location();
2263 action_list_t *list = get_safe_ptr_action(obj_map, location);
2264 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2265 action_list_t::reverse_iterator rit;
2266 for (rit = list->rbegin(); rit != list->rend(); rit++)
2267 if ((*rit)->is_unlock() || (*rit)->is_wait())
2272 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2274 ModelAction *parent = get_last_action(tid);
2276 parent = get_thread(tid)->get_creation();
2281 * Returns the clock vector for a given thread.
2282 * @param tid The thread whose clock vector we want
2283 * @return Desired clock vector
2285 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2287 return get_parent_action(tid)->get_cv();
2291 * Resolve a set of Promises with a current write. The set is provided in the
2292 * Node corresponding to @a write.
2293 * @param write The ModelAction that is fulfilling Promises
2294 * @return True if promises were resolved; false otherwise
2296 bool ModelChecker::resolve_promises(ModelAction *write)
2298 bool resolved = false;
2299 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2301 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2302 Promise *promise = (*promises)[promise_index];
2303 if (write->get_node()->get_promise(i)) {
2304 ModelAction *read = promise->get_action();
2305 if (read->is_rmw()) {
2306 mo_graph->addRMWEdge(write, read);
2308 read_from(read, write);
2309 //First fix up the modification order for actions that happened
2311 r_modification_order(read, write);
2312 //Next fix up the modification order for actions that happened
2314 post_r_modification_order(read, write);
2315 //Make sure the promise's value matches the write's value
2316 ASSERT(promise->get_value() == write->get_value());
2319 promises->erase(promises->begin() + promise_index);
2320 threads_to_check.push_back(read->get_tid());
2327 //Check whether reading these writes has made threads unable to
2330 for (unsigned int i = 0; i < threads_to_check.size(); i++)
2331 mo_check_promises(threads_to_check[i], write);
2337 * Compute the set of promises that could potentially be satisfied by this
2338 * action. Note that the set computation actually appears in the Node, not in
2340 * @param curr The ModelAction that may satisfy promises
2342 void ModelChecker::compute_promises(ModelAction *curr)
2344 for (unsigned int i = 0; i < promises->size(); i++) {
2345 Promise *promise = (*promises)[i];
2346 const ModelAction *act = promise->get_action();
2347 if (!act->happens_before(curr) &&
2349 !act->could_synchronize_with(curr) &&
2350 !act->same_thread(curr) &&
2351 act->get_location() == curr->get_location() &&
2352 promise->get_value() == curr->get_value()) {
2353 curr->get_node()->set_promise(i, act->is_rmw());
2358 /** Checks promises in response to change in ClockVector Threads. */
2359 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2361 for (unsigned int i = 0; i < promises->size(); i++) {
2362 Promise *promise = (*promises)[i];
2363 const ModelAction *act = promise->get_action();
2364 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2365 merge_cv->synchronized_since(act)) {
2366 if (promise->increment_threads(tid)) {
2367 //Promise has failed
2368 priv->failed_promise = true;
2375 void ModelChecker::check_promises_thread_disabled() {
2376 for (unsigned int i = 0; i < promises->size(); i++) {
2377 Promise *promise = (*promises)[i];
2378 if (promise->check_promise()) {
2379 priv->failed_promise = true;
2385 /** Checks promises in response to addition to modification order for threads.
2387 * pthread is the thread that performed the read that created the promise
2389 * pread is the read that created the promise
2391 * pwrite is either the first write to same location as pread by
2392 * pthread that is sequenced after pread or the value read by the
2393 * first read to the same lcoation as pread by pthread that is
2394 * sequenced after pread..
2396 * 1. If tid=pthread, then we check what other threads are reachable
2397 * through the mode order starting with pwrite. Those threads cannot
2398 * perform a write that will resolve the promise due to modification
2399 * order constraints.
2401 * 2. If the tid is not pthread, we check whether pwrite can reach the
2402 * action write through the modification order. If so, that thread
2403 * cannot perform a future write that will resolve the promise due to
2404 * modificatin order constraints.
2406 * @param tid The thread that either read from the model action
2407 * write, or actually did the model action write.
2409 * @param write The ModelAction representing the relevant write.
2411 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write)
2413 void *location = write->get_location();
2414 for (unsigned int i = 0; i < promises->size(); i++) {
2415 Promise *promise = (*promises)[i];
2416 const ModelAction *act = promise->get_action();
2418 //Is this promise on the same location?
2419 if (act->get_location() != location)
2422 //same thread as the promise
2423 if (act->get_tid() == tid) {
2425 //do we have a pwrite for the promise, if not, set it
2426 if (promise->get_write() == NULL) {
2427 promise->set_write(write);
2428 //The pwrite cannot happen before the promise
2429 if (write->happens_before(act) && (write != act)) {
2430 priv->failed_promise = true;
2434 if (mo_graph->checkPromise(write, promise)) {
2435 priv->failed_promise = true;
2440 //Don't do any lookups twice for the same thread
2441 if (promise->has_sync_thread(tid))
2444 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2445 if (promise->increment_threads(tid)) {
2446 priv->failed_promise = true;
2454 * Compute the set of writes that may break the current pending release
2455 * sequence. This information is extracted from previou release sequence
2458 * @param curr The current ModelAction. Must be a release sequence fixup
2461 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2463 if (pending_rel_seqs->empty())
2466 struct release_seq *pending = pending_rel_seqs->back();
2467 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2468 const ModelAction *write = pending->writes[i];
2469 curr->get_node()->add_relseq_break(write);
2472 /* NULL means don't break the sequence; just synchronize */
2473 curr->get_node()->add_relseq_break(NULL);
2477 * Build up an initial set of all past writes that this 'read' action may read
2478 * from. This set is determined by the clock vector's "happens before"
2480 * @param curr is the current ModelAction that we are exploring; it must be a
2483 void ModelChecker::build_reads_from_past(ModelAction *curr)
2485 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2487 ASSERT(curr->is_read());
2489 ModelAction *last_sc_write = NULL;
2491 if (curr->is_seqcst())
2492 last_sc_write = get_last_seq_cst_write(curr);
2494 /* Iterate over all threads */
2495 for (i = 0; i < thrd_lists->size(); i++) {
2496 /* Iterate over actions in thread, starting from most recent */
2497 action_list_t *list = &(*thrd_lists)[i];
2498 action_list_t::reverse_iterator rit;
2499 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2500 ModelAction *act = *rit;
2502 /* Only consider 'write' actions */
2503 if (!act->is_write() || act == curr)
2506 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2507 bool allow_read = true;
2509 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2511 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2515 curr->get_node()->add_read_from(act);
2517 /* Include at most one act per-thread that "happens before" curr */
2518 if (act->happens_before(curr))
2523 if (DBG_ENABLED()) {
2524 model_print("Reached read action:\n");
2526 model_print("Printing may_read_from\n");
2527 curr->get_node()->print_may_read_from();
2528 model_print("End printing may_read_from\n");
2532 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2535 /* UNINIT actions don't have a Node, and they never sleep */
2536 if (write->is_uninitialized())
2538 Node *prevnode = write->get_node()->get_parent();
2540 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2541 if (write->is_release() && thread_sleep)
2543 if (!write->is_rmw()) {
2546 if (write->get_reads_from() == NULL)
2548 write = write->get_reads_from();
2553 * @brief Create a new action representing an uninitialized atomic
2554 * @param location The memory location of the atomic object
2555 * @return A pointer to a new ModelAction
2557 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2559 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2560 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2561 act->create_cv(NULL);
2565 static void print_list(action_list_t *list, int exec_num = -1)
2567 action_list_t::iterator it;
2569 model_print("---------------------------------------------------------------------\n");
2571 model_print("Execution %d:\n", exec_num);
2573 unsigned int hash = 0;
2575 for (it = list->begin(); it != list->end(); it++) {
2577 hash = hash^(hash<<3)^((*it)->hash());
2579 model_print("HASH %u\n", hash);
2580 model_print("---------------------------------------------------------------------\n");
2583 #if SUPPORT_MOD_ORDER_DUMP
2584 void ModelChecker::dumpGraph(char *filename) const
2587 sprintf(buffer, "%s.dot", filename);
2588 FILE *file = fopen(buffer, "w");
2589 fprintf(file, "digraph %s {\n", filename);
2590 mo_graph->dumpNodes(file);
2591 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2593 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2594 ModelAction *action = *it;
2595 if (action->is_read()) {
2596 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2597 if (action->get_reads_from() != NULL)
2598 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2600 if (thread_array[action->get_tid()] != NULL) {
2601 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2604 thread_array[action->get_tid()] = action;
2606 fprintf(file, "}\n");
2607 model_free(thread_array);
2612 /** @brief Prints an execution trace summary. */
2613 void ModelChecker::print_summary() const
2615 #if SUPPORT_MOD_ORDER_DUMP
2617 char buffername[100];
2618 sprintf(buffername, "exec%04u", stats.num_total);
2619 mo_graph->dumpGraphToFile(buffername);
2620 sprintf(buffername, "graph%04u", stats.num_total);
2621 dumpGraph(buffername);
2624 if (!isfeasibleprefix())
2625 model_print("INFEASIBLE EXECUTION!\n");
2626 print_list(action_trace, stats.num_total);
2631 * Add a Thread to the system for the first time. Should only be called once
2633 * @param t The Thread to add
2635 void ModelChecker::add_thread(Thread *t)
2637 thread_map->put(id_to_int(t->get_id()), t);
2638 scheduler->add_thread(t);
2642 * Removes a thread from the scheduler.
2643 * @param the thread to remove.
2645 void ModelChecker::remove_thread(Thread *t)
2647 scheduler->remove_thread(t);
2651 * @brief Get a Thread reference by its ID
2652 * @param tid The Thread's ID
2653 * @return A Thread reference
2655 Thread * ModelChecker::get_thread(thread_id_t tid) const
2657 return thread_map->get(id_to_int(tid));
2661 * @brief Get a reference to the Thread in which a ModelAction was executed
2662 * @param act The ModelAction
2663 * @return A Thread reference
2665 Thread * ModelChecker::get_thread(ModelAction *act) const
2667 return get_thread(act->get_tid());
2671 * @brief Check if a Thread is currently enabled
2672 * @param t The Thread to check
2673 * @return True if the Thread is currently enabled
2675 bool ModelChecker::is_enabled(Thread *t) const
2677 return scheduler->is_enabled(t);
2681 * @brief Check if a Thread is currently enabled
2682 * @param tid The ID of the Thread to check
2683 * @return True if the Thread is currently enabled
2685 bool ModelChecker::is_enabled(thread_id_t tid) const
2687 return scheduler->is_enabled(tid);
2691 * Switch from a user-context to the "master thread" context (a.k.a. system
2692 * context). This switch is made with the intention of exploring a particular
2693 * model-checking action (described by a ModelAction object). Must be called
2694 * from a user-thread context.
2696 * @param act The current action that will be explored. May be NULL only if
2697 * trace is exiting via an assertion (see ModelChecker::set_assert and
2698 * ModelChecker::has_asserted).
2699 * @return Return the value returned by the current action
2701 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2704 Thread *old = thread_current();
2705 set_current_action(act);
2706 old->set_state(THREAD_READY);
2707 if (Thread::swap(old, &system_context) < 0) {
2708 perror("swap threads");
2711 return old->get_return_value();
2715 * Takes the next step in the execution, if possible.
2716 * @param curr The current step to take
2717 * @return Returns true (success) if a step was taken and false otherwise.
2719 bool ModelChecker::take_step(ModelAction *curr)
2724 Thread *curr_thrd = get_thread(curr);
2725 ASSERT(curr_thrd->get_state() == THREAD_READY);
2727 curr = check_current_action(curr);
2729 /* Infeasible -> don't take any more steps */
2730 if (is_infeasible())
2732 else if (isfeasibleprefix() && have_bug_reports()) {
2737 if (params.bound != 0)
2738 if (priv->used_sequence_numbers > params.bound)
2741 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2742 scheduler->remove_thread(curr_thrd);
2744 Thread *next_thrd = get_next_thread(curr);
2745 next_thrd = scheduler->next_thread(next_thrd);
2747 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2748 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2751 * Launch end-of-execution release sequence fixups only when there are:
2753 * (1) no more user threads to run (or when execution replay chooses
2754 * the 'model_thread')
2755 * (2) pending release sequences
2756 * (3) pending assertions (i.e., data races)
2757 * (4) no pending promises
2759 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2760 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2761 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2762 pending_rel_seqs->size());
2763 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2764 std::memory_order_seq_cst, NULL, VALUE_NONE,
2766 set_current_action(fixup);
2770 /* next_thrd == NULL -> don't take any more steps */
2774 next_thrd->set_state(THREAD_RUNNING);
2776 if (next_thrd->get_pending() != NULL) {
2777 /* restart a pending action */
2778 set_current_action(next_thrd->get_pending());
2779 next_thrd->set_pending(NULL);
2780 next_thrd->set_state(THREAD_READY);
2784 /* Return false only if swap fails with an error */
2785 return (Thread::swap(&system_context, next_thrd) == 0);
2788 /** Wrapper to run the user's main function, with appropriate arguments */
2789 void user_main_wrapper(void *)
2791 user_main(model->params.argc, model->params.argv);
2794 /** @brief Run ModelChecker for the user program */
2795 void ModelChecker::run()
2799 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2803 /* Run user thread up to its first action */
2804 scheduler->next_thread(t);
2805 Thread::swap(&system_context, t);
2807 /* Wait for all threads to complete */
2808 while (take_step(priv->current_action));
2809 } while (next_execution());