9 #include "snapshot-interface.h"
11 #include "clockvector.h"
12 #include "cyclegraph.h"
15 #include "threads-model.h"
18 #define INITIAL_THREAD_ID 0
23 bug_message(const char *str) {
24 const char *fmt = " [BUG] %s\n";
25 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
26 sprintf(msg, fmt, str);
28 ~bug_message() { if (msg) snapshot_free(msg); }
31 void print() { model_print("%s", msg); }
37 * Structure for holding small ModelChecker members that should be snapshotted
39 struct model_snapshot_members {
40 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),
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;
65 ModelAction *next_backtrack;
66 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
67 struct execution_stats stats;
70 /** @brief Incorrectly-ordered synchronization was made */
71 bool bad_synchronization;
77 /** @brief Constructor */
78 ModelChecker::ModelChecker(struct model_params params) :
79 /* Initialize default scheduler */
81 scheduler(new Scheduler()),
83 earliest_diverge(NULL),
84 action_trace(new action_list_t()),
85 thread_map(new HashTable<int, Thread *, int>()),
86 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
89 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
90 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
91 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
92 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
93 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
94 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
95 node_stack(new NodeStack()),
96 priv(new struct model_snapshot_members()),
97 mo_graph(new CycleGraph())
99 /* Initialize a model-checker thread, for special ModelActions */
100 model_thread = new Thread(get_next_id());
101 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
104 /** @brief Destructor */
105 ModelChecker::~ModelChecker()
107 for (unsigned int i = 0; i < get_num_threads(); i++)
108 delete thread_map->get(i);
113 delete lock_waiters_map;
114 delete condvar_waiters_map;
117 for (unsigned int i = 0; i < promises->size(); i++)
118 delete (*promises)[i];
121 delete pending_rel_seqs;
123 delete thrd_last_action;
124 delete thrd_last_fence_release;
131 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) {
141 std::vector<action_list_t> * tmp=hash->get(ptr);
143 tmp=new std::vector<action_list_t>();
150 * Restores user program to initial state and resets all model-checker data
153 void ModelChecker::reset_to_initial_state()
155 DEBUG("+++ Resetting to initial state +++\n");
156 node_stack->reset_execution();
158 /* Print all model-checker output before rollback */
161 snapshotObject->backTrackBeforeStep(0);
164 /** @return a thread ID for a new Thread */
165 thread_id_t ModelChecker::get_next_id()
167 return priv->next_thread_id++;
170 /** @return the number of user threads created during this execution */
171 unsigned int ModelChecker::get_num_threads() const
173 return priv->next_thread_id;
176 /** @return The currently executing Thread. */
177 Thread * ModelChecker::get_current_thread() const
179 return scheduler->get_current_thread();
182 /** @return a sequence number for a new ModelAction */
183 modelclock_t ModelChecker::get_next_seq_num()
185 return ++priv->used_sequence_numbers;
188 Node * ModelChecker::get_curr_node() const
190 return node_stack->get_head();
194 * @brief Choose the next thread to execute.
196 * This function chooses the next thread that should execute. It can force the
197 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
198 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
199 * The model-checker may have no preference regarding the next thread (i.e.,
200 * when exploring a new execution ordering), in which case this will return
202 * @param curr The current ModelAction. This action might guide the choice of
204 * @return The next thread to run. If the model-checker has no preference, NULL.
206 Thread * ModelChecker::get_next_thread(ModelAction *curr)
211 /* Do not split atomic actions. */
213 return thread_current();
214 /* The THREAD_CREATE action points to the created Thread */
215 else if (curr->get_type() == THREAD_CREATE)
216 return (Thread *)curr->get_location();
219 /* Have we completed exploring the preselected path? */
223 /* Else, we are trying to replay an execution */
224 ModelAction *next = node_stack->get_next()->get_action();
226 if (next == diverge) {
227 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
228 earliest_diverge=diverge;
230 Node *nextnode = next->get_node();
231 Node *prevnode = nextnode->get_parent();
232 scheduler->update_sleep_set(prevnode);
234 /* Reached divergence point */
235 if (nextnode->increment_misc()) {
236 /* The next node will try to satisfy a different misc_index values. */
237 tid = next->get_tid();
238 node_stack->pop_restofstack(2);
239 } else if (nextnode->increment_promise()) {
240 /* The next node will try to satisfy a different set of promises. */
241 tid = next->get_tid();
242 node_stack->pop_restofstack(2);
243 } else if (nextnode->increment_read_from()) {
244 /* The next node will read from a different value. */
245 tid = next->get_tid();
246 node_stack->pop_restofstack(2);
247 } else if (nextnode->increment_future_value()) {
248 /* The next node will try to read from a different future value. */
249 tid = next->get_tid();
250 node_stack->pop_restofstack(2);
251 } else if (nextnode->increment_relseq_break()) {
252 /* The next node will try to resolve a release sequence differently */
253 tid = next->get_tid();
254 node_stack->pop_restofstack(2);
256 /* Make a different thread execute for next step */
257 scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid())));
258 tid = prevnode->get_next_backtrack();
259 /* Make sure the backtracked thread isn't sleeping. */
260 node_stack->pop_restofstack(1);
261 if (diverge==earliest_diverge) {
262 earliest_diverge=prevnode->get_action();
265 /* The correct sleep set is in the parent node. */
268 DEBUG("*** Divergence point ***\n");
272 tid = next->get_tid();
274 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
275 ASSERT(tid != THREAD_ID_T_NONE);
276 return thread_map->get(id_to_int(tid));
280 * We need to know what the next actions of all threads in the sleep
281 * set will be. This method computes them and stores the actions at
282 * the corresponding thread object's pending action.
285 void ModelChecker::execute_sleep_set() {
286 for(unsigned int i=0;i<get_num_threads();i++) {
287 thread_id_t tid=int_to_id(i);
288 Thread *thr=get_thread(tid);
289 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET &&
290 thr->get_pending() == NULL ) {
291 thr->set_state(THREAD_RUNNING);
292 scheduler->next_thread(thr);
293 Thread::swap(&system_context, thr);
294 priv->current_action->set_sleep_flag();
295 thr->set_pending(priv->current_action);
298 priv->current_action = NULL;
301 void ModelChecker::wake_up_sleeping_actions(ModelAction * curr) {
302 for(unsigned int i=0;i<get_num_threads();i++) {
303 thread_id_t tid=int_to_id(i);
304 Thread *thr=get_thread(tid);
305 if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
306 ModelAction *pending_act=thr->get_pending();
307 if ((!curr->is_rmwr())&&pending_act->could_synchronize_with(curr)) {
308 //Remove this thread from sleep set
309 scheduler->remove_sleep(thr);
315 /** @brief Alert the model-checker that an incorrectly-ordered
316 * synchronization was made */
317 void ModelChecker::set_bad_synchronization()
319 priv->bad_synchronization = true;
322 bool ModelChecker::has_asserted() const
324 return priv->asserted;
327 void ModelChecker::set_assert()
329 priv->asserted = true;
333 * Check if we are in a deadlock. Should only be called at the end of an
334 * execution, although it should not give false positives in the middle of an
335 * execution (there should be some ENABLED thread).
337 * @return True if program is in a deadlock; false otherwise
339 bool ModelChecker::is_deadlocked() const
341 bool blocking_threads = false;
342 for (unsigned int i = 0; i < get_num_threads(); i++) {
343 thread_id_t tid = int_to_id(i);
346 Thread *t = get_thread(tid);
347 if (!t->is_model_thread() && t->get_pending())
348 blocking_threads = true;
350 return blocking_threads;
354 * Check if this is a complete execution. That is, have all thread completed
355 * execution (rather than exiting because sleep sets have forced a redundant
358 * @return True if the execution is complete.
360 bool ModelChecker::is_complete_execution() const
362 for (unsigned int i = 0; i < get_num_threads(); i++)
363 if (is_enabled(int_to_id(i)))
369 * @brief Assert a bug in the executing program.
371 * Use this function to assert any sort of bug in the user program. If the
372 * current trace is feasible (actually, a prefix of some feasible execution),
373 * then this execution will be aborted, printing the appropriate message. If
374 * the current trace is not yet feasible, the error message will be stashed and
375 * printed if the execution ever becomes feasible.
377 * @param msg Descriptive message for the bug (do not include newline char)
378 * @return True if bug is immediately-feasible
380 bool ModelChecker::assert_bug(const char *msg)
382 priv->bugs.push_back(new bug_message(msg));
384 if (isfeasibleprefix()) {
392 * @brief Assert a bug in the executing program, asserted by a user thread
393 * @see ModelChecker::assert_bug
394 * @param msg Descriptive message for the bug (do not include newline char)
396 void ModelChecker::assert_user_bug(const char *msg)
398 /* If feasible bug, bail out now */
400 switch_to_master(NULL);
403 /** @return True, if any bugs have been reported for this execution */
404 bool ModelChecker::have_bug_reports() const
406 return priv->bugs.size() != 0;
409 /** @brief Print bug report listing for this execution (if any bugs exist) */
410 void ModelChecker::print_bugs() const
412 if (have_bug_reports()) {
413 model_print("Bug report: %zu bug%s detected\n",
415 priv->bugs.size() > 1 ? "s" : "");
416 for (unsigned int i = 0; i < priv->bugs.size(); i++)
417 priv->bugs[i]->print();
422 * @brief Record end-of-execution stats
424 * Must be run when exiting an execution. Records various stats.
425 * @see struct execution_stats
427 void ModelChecker::record_stats()
430 if (!isfeasibleprefix())
431 stats.num_infeasible++;
432 else if (have_bug_reports())
433 stats.num_buggy_executions++;
434 else if (is_complete_execution())
435 stats.num_complete++;
437 stats.num_redundant++;
440 /** @brief Print execution stats */
441 void ModelChecker::print_stats() const
443 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
444 model_print("Number of redundant executions: %d\n", stats.num_redundant);
445 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
446 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
447 model_print("Total executions: %d\n", stats.num_total);
448 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
452 * @brief End-of-exeuction print
453 * @param printbugs Should any existing bugs be printed?
455 void ModelChecker::print_execution(bool printbugs) const
457 print_program_output();
459 if (DBG_ENABLED() || params.verbose) {
460 model_print("Earliest divergence point since last feasible execution:\n");
461 if (earliest_diverge)
462 earliest_diverge->print();
464 model_print("(Not set)\n");
470 /* Don't print invalid bugs */
479 * Queries the model-checker for more executions to explore and, if one
480 * exists, resets the model-checker state to execute a new execution.
482 * @return If there are more executions to explore, return true. Otherwise,
485 bool ModelChecker::next_execution()
488 /* Is this execution a feasible execution that's worth bug-checking? */
489 bool complete = isfeasibleprefix() && (is_complete_execution() ||
492 /* End-of-execution bug checks */
495 assert_bug("Deadlock detected");
503 if (DBG_ENABLED() || params.verbose || have_bug_reports())
504 print_execution(complete);
506 clear_program_output();
509 earliest_diverge = NULL;
511 if ((diverge = get_next_backtrack()) == NULL)
515 model_print("Next execution will diverge at:\n");
519 reset_to_initial_state();
523 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
525 switch (act->get_type()) {
530 /* Optimization: relaxed operations don't need backtracking */
531 if (act->is_relaxed())
533 /* linear search: from most recent to oldest */
534 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
535 action_list_t::reverse_iterator rit;
536 for (rit = list->rbegin(); rit != list->rend(); rit++) {
537 ModelAction *prev = *rit;
538 if (prev->could_synchronize_with(act))
544 case ATOMIC_TRYLOCK: {
545 /* linear search: from most recent to oldest */
546 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
547 action_list_t::reverse_iterator rit;
548 for (rit = list->rbegin(); rit != list->rend(); rit++) {
549 ModelAction *prev = *rit;
550 if (act->is_conflicting_lock(prev))
555 case ATOMIC_UNLOCK: {
556 /* linear search: from most recent to oldest */
557 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
558 action_list_t::reverse_iterator rit;
559 for (rit = list->rbegin(); rit != list->rend(); rit++) {
560 ModelAction *prev = *rit;
561 if (!act->same_thread(prev)&&prev->is_failed_trylock())
567 /* linear search: from most recent to oldest */
568 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
569 action_list_t::reverse_iterator rit;
570 for (rit = list->rbegin(); rit != list->rend(); rit++) {
571 ModelAction *prev = *rit;
572 if (!act->same_thread(prev)&&prev->is_failed_trylock())
574 if (!act->same_thread(prev)&&prev->is_notify())
580 case ATOMIC_NOTIFY_ALL:
581 case ATOMIC_NOTIFY_ONE: {
582 /* linear search: from most recent to oldest */
583 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
584 action_list_t::reverse_iterator rit;
585 for (rit = list->rbegin(); rit != list->rend(); rit++) {
586 ModelAction *prev = *rit;
587 if (!act->same_thread(prev)&&prev->is_wait())
598 /** This method finds backtracking points where we should try to
599 * reorder the parameter ModelAction against.
601 * @param the ModelAction to find backtracking points for.
603 void ModelChecker::set_backtracking(ModelAction *act)
605 Thread *t = get_thread(act);
606 ModelAction * prev = get_last_conflict(act);
610 Node * node = prev->get_node()->get_parent();
612 int low_tid, high_tid;
613 if (node->is_enabled(t)) {
614 low_tid = id_to_int(act->get_tid());
615 high_tid = low_tid+1;
618 high_tid = get_num_threads();
621 for(int i = low_tid; i < high_tid; i++) {
622 thread_id_t tid = int_to_id(i);
624 /* Make sure this thread can be enabled here. */
625 if (i >= node->get_num_threads())
628 /* Don't backtrack into a point where the thread is disabled or sleeping. */
629 if (node->enabled_status(tid)!=THREAD_ENABLED)
632 /* Check if this has been explored already */
633 if (node->has_been_explored(tid))
636 /* See if fairness allows */
637 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
639 for(int t=0;t<node->get_num_threads();t++) {
640 thread_id_t tother=int_to_id(t);
641 if (node->is_enabled(tother) && node->has_priority(tother)) {
649 /* Cache the latest backtracking point */
650 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
651 priv->next_backtrack = prev;
653 /* If this is a new backtracking point, mark the tree */
654 if (!node->set_backtrack(tid))
656 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
657 id_to_int(prev->get_tid()),
658 id_to_int(t->get_id()));
667 * Returns last backtracking point. The model checker will explore a different
668 * path for this point in the next execution.
669 * @return The ModelAction at which the next execution should diverge.
671 ModelAction * ModelChecker::get_next_backtrack()
673 ModelAction *next = priv->next_backtrack;
674 priv->next_backtrack = NULL;
679 * Processes a read or rmw model action.
680 * @param curr is the read model action to process.
681 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
682 * @return True if processing this read updates the mo_graph.
684 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
686 uint64_t value = VALUE_NONE;
687 bool updated = false;
689 const ModelAction *reads_from = curr->get_node()->get_read_from();
690 if (reads_from != NULL) {
691 mo_graph->startChanges();
693 value = reads_from->get_value();
694 bool r_status = false;
696 if (!second_part_of_rmw) {
697 check_recency(curr, reads_from);
698 r_status = r_modification_order(curr, reads_from);
702 if (!second_part_of_rmw&&is_infeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
703 mo_graph->rollbackChanges();
704 priv->too_many_reads = false;
708 read_from(curr, reads_from);
709 mo_graph->commitChanges();
710 mo_check_promises(curr->get_tid(), reads_from);
713 } else if (!second_part_of_rmw) {
714 /* Read from future value */
715 value = curr->get_node()->get_future_value();
716 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
717 read_from(curr, NULL);
718 Promise *valuepromise = new Promise(curr, value, expiration);
719 promises->push_back(valuepromise);
721 get_thread(curr)->set_return_value(value);
727 * Processes a lock, trylock, or unlock model action. @param curr is
728 * the read model action to process.
730 * The try lock operation checks whether the lock is taken. If not,
731 * it falls to the normal lock operation case. If so, it returns
734 * The lock operation has already been checked that it is enabled, so
735 * it just grabs the lock and synchronizes with the previous unlock.
737 * The unlock operation has to re-enable all of the threads that are
738 * waiting on the lock.
740 * @return True if synchronization was updated; false otherwise
742 bool ModelChecker::process_mutex(ModelAction *curr) {
743 std::mutex *mutex=NULL;
744 struct std::mutex_state *state=NULL;
746 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
747 mutex = (std::mutex *)curr->get_location();
748 state = mutex->get_state();
749 } else if(curr->is_wait()) {
750 mutex = (std::mutex *)curr->get_value();
751 state = mutex->get_state();
754 switch (curr->get_type()) {
755 case ATOMIC_TRYLOCK: {
756 bool success = !state->islocked;
757 curr->set_try_lock(success);
759 get_thread(curr)->set_return_value(0);
762 get_thread(curr)->set_return_value(1);
764 //otherwise fall into the lock case
766 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
767 assert_bug("Lock access before initialization");
768 state->islocked = true;
769 ModelAction *unlock = get_last_unlock(curr);
770 //synchronize with the previous unlock statement
771 if (unlock != NULL) {
772 curr->synchronize_with(unlock);
777 case ATOMIC_UNLOCK: {
779 state->islocked = false;
780 //wake up the other threads
781 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
782 //activate all the waiting threads
783 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
784 scheduler->wake(get_thread(*rit));
791 state->islocked = false;
792 //wake up the other threads
793 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
794 //activate all the waiting threads
795 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
796 scheduler->wake(get_thread(*rit));
799 //check whether we should go to sleep or not...simulate spurious failures
800 if (curr->get_node()->get_misc()==0) {
801 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
803 scheduler->sleep(get_current_thread());
807 case ATOMIC_NOTIFY_ALL: {
808 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
809 //activate all the waiting threads
810 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
811 scheduler->wake(get_thread(*rit));
816 case ATOMIC_NOTIFY_ONE: {
817 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
818 int wakeupthread=curr->get_node()->get_misc();
819 action_list_t::iterator it = waiters->begin();
820 advance(it, wakeupthread);
821 scheduler->wake(get_thread(*it));
833 * Process a write ModelAction
834 * @param curr The ModelAction to process
835 * @return True if the mo_graph was updated or promises were resolved
837 bool ModelChecker::process_write(ModelAction *curr)
839 bool updated_mod_order = w_modification_order(curr);
840 bool updated_promises = resolve_promises(curr);
842 if (promises->size() == 0) {
843 for (unsigned int i = 0; i < futurevalues->size(); i++) {
844 struct PendingFutureValue pfv = (*futurevalues)[i];
845 //Do more ambitious checks now that mo is more complete
846 if (mo_may_allow(pfv.writer, pfv.act)&&
847 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number()+params.maxfuturedelay) &&
848 (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
849 priv->next_backtrack = pfv.act;
851 futurevalues->resize(0);
854 mo_graph->commitChanges();
855 mo_check_promises(curr->get_tid(), curr);
857 get_thread(curr)->set_return_value(VALUE_NONE);
858 return updated_mod_order || updated_promises;
862 * Process a fence ModelAction
863 * @param curr The ModelAction to process
864 * @return True if synchronization was updated
866 bool ModelChecker::process_fence(ModelAction *curr)
869 * fence-relaxed: no-op
870 * fence-release: only log the occurence (not in this function), for
871 * use in later synchronization
872 * fence-acquire (this function): search for hypothetical release
875 bool updated = false;
876 if (curr->is_acquire()) {
877 action_list_t *list = action_trace;
878 action_list_t::reverse_iterator rit;
879 /* Find X : is_read(X) && X --sb-> curr */
880 for (rit = list->rbegin(); rit != list->rend(); rit++) {
881 ModelAction *act = *rit;
884 if (act->get_tid() != curr->get_tid())
886 /* Stop at the beginning of the thread */
887 if (act->is_thread_start())
889 /* Stop once we reach a prior fence-acquire */
890 if (act->is_fence() && act->is_acquire())
894 /* read-acquire will find its own release sequences */
895 if (act->is_acquire())
898 /* Establish hypothetical release sequences */
899 rel_heads_list_t release_heads;
900 get_release_seq_heads(curr, act, &release_heads);
901 for (unsigned int i = 0; i < release_heads.size(); i++)
902 if (!curr->synchronize_with(release_heads[i]))
903 set_bad_synchronization();
904 if (release_heads.size() != 0)
912 * @brief Process the current action for thread-related activity
914 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
915 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
916 * synchronization, etc. This function is a no-op for non-THREAD actions
917 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
919 * @param curr The current action
920 * @return True if synchronization was updated or a thread completed
922 bool ModelChecker::process_thread_action(ModelAction *curr)
924 bool updated = false;
926 switch (curr->get_type()) {
927 case THREAD_CREATE: {
928 Thread *th = (Thread *)curr->get_location();
929 th->set_creation(curr);
933 Thread *blocking = (Thread *)curr->get_location();
934 ModelAction *act = get_last_action(blocking->get_id());
935 curr->synchronize_with(act);
936 updated = true; /* trigger rel-seq checks */
939 case THREAD_FINISH: {
940 Thread *th = get_thread(curr);
941 while (!th->wait_list_empty()) {
942 ModelAction *act = th->pop_wait_list();
943 scheduler->wake(get_thread(act));
946 updated = true; /* trigger rel-seq checks */
950 check_promises(curr->get_tid(), NULL, curr->get_cv());
961 * @brief Process the current action for release sequence fixup activity
963 * Performs model-checker release sequence fixups for the current action,
964 * forcing a single pending release sequence to break (with a given, potential
965 * "loose" write) or to complete (i.e., synchronize). If a pending release
966 * sequence forms a complete release sequence, then we must perform the fixup
967 * synchronization, mo_graph additions, etc.
969 * @param curr The current action; must be a release sequence fixup action
970 * @param work_queue The work queue to which to add work items as they are
973 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
975 const ModelAction *write = curr->get_node()->get_relseq_break();
976 struct release_seq *sequence = pending_rel_seqs->back();
977 pending_rel_seqs->pop_back();
979 ModelAction *acquire = sequence->acquire;
980 const ModelAction *rf = sequence->rf;
981 const ModelAction *release = sequence->release;
985 ASSERT(release->same_thread(rf));
989 * @todo Forcing a synchronization requires that we set
990 * modification order constraints. For instance, we can't allow
991 * a fixup sequence in which two separate read-acquire
992 * operations read from the same sequence, where the first one
993 * synchronizes and the other doesn't. Essentially, we can't
994 * allow any writes to insert themselves between 'release' and
998 /* Must synchronize */
999 if (!acquire->synchronize_with(release)) {
1000 set_bad_synchronization();
1003 /* Re-check all pending release sequences */
1004 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1005 /* Re-check act for mo_graph edges */
1006 work_queue->push_back(MOEdgeWorkEntry(acquire));
1008 /* propagate synchronization to later actions */
1009 action_list_t::reverse_iterator rit = action_trace->rbegin();
1010 for (; (*rit) != acquire; rit++) {
1011 ModelAction *propagate = *rit;
1012 if (acquire->happens_before(propagate)) {
1013 propagate->synchronize_with(acquire);
1014 /* Re-check 'propagate' for mo_graph edges */
1015 work_queue->push_back(MOEdgeWorkEntry(propagate));
1019 /* Break release sequence with new edges:
1020 * release --mo--> write --mo--> rf */
1021 mo_graph->addEdge(release, write);
1022 mo_graph->addEdge(write, rf);
1025 /* See if we have realized a data race */
1030 * Initialize the current action by performing one or more of the following
1031 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1032 * in the NodeStack, manipulating backtracking sets, allocating and
1033 * initializing clock vectors, and computing the promises to fulfill.
1035 * @param curr The current action, as passed from the user context; may be
1036 * freed/invalidated after the execution of this function, with a different
1037 * action "returned" its place (pass-by-reference)
1038 * @return True if curr is a newly-explored action; false otherwise
1040 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1042 ModelAction *newcurr;
1044 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1045 newcurr = process_rmw(*curr);
1048 if (newcurr->is_rmw())
1049 compute_promises(newcurr);
1055 (*curr)->set_seq_number(get_next_seq_num());
1057 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1059 /* First restore type and order in case of RMW operation */
1060 if ((*curr)->is_rmwr())
1061 newcurr->copy_typeandorder(*curr);
1063 ASSERT((*curr)->get_location() == newcurr->get_location());
1064 newcurr->copy_from_new(*curr);
1066 /* Discard duplicate ModelAction; use action from NodeStack */
1069 /* Always compute new clock vector */
1070 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1073 return false; /* Action was explored previously */
1077 /* Always compute new clock vector */
1078 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1080 /* Assign most recent release fence */
1081 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1084 * Perform one-time actions when pushing new ModelAction onto
1087 if (newcurr->is_write())
1088 compute_promises(newcurr);
1089 else if (newcurr->is_relseq_fixup())
1090 compute_relseq_breakwrites(newcurr);
1091 else if (newcurr->is_wait())
1092 newcurr->get_node()->set_misc_max(2);
1093 else if (newcurr->is_notify_one()) {
1094 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1096 return true; /* This was a new ModelAction */
1101 * @brief Establish reads-from relation between two actions
1103 * Perform basic operations involved with establishing a concrete rf relation,
1104 * including setting the ModelAction data and checking for release sequences.
1106 * @param act The action that is reading (must be a read)
1107 * @param rf The action from which we are reading (must be a write)
1109 * @return True if this read established synchronization
1111 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1113 act->set_read_from(rf);
1114 if (rf != NULL && act->is_acquire()) {
1115 rel_heads_list_t release_heads;
1116 get_release_seq_heads(act, act, &release_heads);
1117 int num_heads = release_heads.size();
1118 for (unsigned int i = 0; i < release_heads.size(); i++)
1119 if (!act->synchronize_with(release_heads[i])) {
1120 set_bad_synchronization();
1123 return num_heads > 0;
1129 * @brief Check whether a model action is enabled.
1131 * Checks whether a lock or join operation would be successful (i.e., is the
1132 * lock already locked, or is the joined thread already complete). If not, put
1133 * the action in a waiter list.
1135 * @param curr is the ModelAction to check whether it is enabled.
1136 * @return a bool that indicates whether the action is enabled.
1138 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1139 if (curr->is_lock()) {
1140 std::mutex * lock = (std::mutex *)curr->get_location();
1141 struct std::mutex_state * state = lock->get_state();
1142 if (state->islocked) {
1143 //Stick the action in the appropriate waiting queue
1144 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1147 } else if (curr->get_type() == THREAD_JOIN) {
1148 Thread *blocking = (Thread *)curr->get_location();
1149 if (!blocking->is_complete()) {
1150 blocking->push_wait_list(curr);
1159 * Stores the ModelAction for the current thread action. Call this
1160 * immediately before switching from user- to system-context to pass
1161 * data between them.
1162 * @param act The ModelAction created by the user-thread action
1164 void ModelChecker::set_current_action(ModelAction *act) {
1165 priv->current_action = act;
1169 * This is the heart of the model checker routine. It performs model-checking
1170 * actions corresponding to a given "current action." Among other processes, it
1171 * calculates reads-from relationships, updates synchronization clock vectors,
1172 * forms a memory_order constraints graph, and handles replay/backtrack
1173 * execution when running permutations of previously-observed executions.
1175 * @param curr The current action to process
1176 * @return The next Thread that must be executed. May be NULL if ModelChecker
1177 * makes no choice (e.g., according to replay execution, combining RMW actions,
1180 Thread * ModelChecker::check_current_action(ModelAction *curr)
1183 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1185 if (!check_action_enabled(curr)) {
1186 /* Make the execution look like we chose to run this action
1187 * much later, when a lock/join can succeed */
1188 get_current_thread()->set_pending(curr);
1189 scheduler->sleep(get_current_thread());
1190 return get_next_thread(NULL);
1193 bool newly_explored = initialize_curr_action(&curr);
1195 wake_up_sleeping_actions(curr);
1197 /* Add the action to lists before any other model-checking tasks */
1198 if (!second_part_of_rmw)
1199 add_action_to_lists(curr);
1201 /* Build may_read_from set for newly-created actions */
1202 if (newly_explored && curr->is_read())
1203 build_reads_from_past(curr);
1205 /* Initialize work_queue with the "current action" work */
1206 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1207 while (!work_queue.empty() && !has_asserted()) {
1208 WorkQueueEntry work = work_queue.front();
1209 work_queue.pop_front();
1211 switch (work.type) {
1212 case WORK_CHECK_CURR_ACTION: {
1213 ModelAction *act = work.action;
1214 bool update = false; /* update this location's release seq's */
1215 bool update_all = false; /* update all release seq's */
1217 if (process_thread_action(curr))
1220 if (act->is_read() && process_read(act, second_part_of_rmw))
1223 if (act->is_write() && process_write(act))
1226 if (act->is_fence() && process_fence(act))
1229 if (act->is_mutex_op() && process_mutex(act))
1232 if (act->is_relseq_fixup())
1233 process_relseq_fixup(curr, &work_queue);
1236 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1238 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1241 case WORK_CHECK_RELEASE_SEQ:
1242 resolve_release_sequences(work.location, &work_queue);
1244 case WORK_CHECK_MO_EDGES: {
1245 /** @todo Complete verification of work_queue */
1246 ModelAction *act = work.action;
1247 bool updated = false;
1249 if (act->is_read()) {
1250 const ModelAction *rf = act->get_reads_from();
1251 if (rf != NULL && r_modification_order(act, rf))
1254 if (act->is_write()) {
1255 if (w_modification_order(act))
1258 mo_graph->commitChanges();
1261 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1270 check_curr_backtracking(curr);
1271 set_backtracking(curr);
1272 return get_next_thread(curr);
1275 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
1276 Node *currnode = curr->get_node();
1277 Node *parnode = currnode->get_parent();
1279 if ((!parnode->backtrack_empty() ||
1280 !currnode->misc_empty() ||
1281 !currnode->read_from_empty() ||
1282 !currnode->future_value_empty() ||
1283 !currnode->promise_empty() ||
1284 !currnode->relseq_break_empty())
1285 && (!priv->next_backtrack ||
1286 *curr > *priv->next_backtrack)) {
1287 priv->next_backtrack = curr;
1291 bool ModelChecker::promises_expired() const
1293 for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
1294 Promise *promise = (*promises)[promise_index];
1295 if (promise->get_expiration()<priv->used_sequence_numbers) {
1303 * This is the strongest feasibility check available.
1304 * @return whether the current trace (partial or complete) must be a prefix of
1307 bool ModelChecker::isfeasibleprefix() const
1309 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1313 * Returns whether the current completed trace is feasible, except for pending
1314 * release sequences.
1316 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1318 if (DBG_ENABLED() && promises->size() != 0)
1319 DEBUG("Infeasible: unrevolved promises\n");
1321 return !is_infeasible() && promises->size() == 0;
1325 * Check if the current partial trace is infeasible. Does not check any
1326 * end-of-execution flags, which might rule out the execution. Thus, this is
1327 * useful only for ruling an execution as infeasible.
1328 * @return whether the current partial trace is infeasible.
1330 bool ModelChecker::is_infeasible() const
1332 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1333 DEBUG("Infeasible: RMW violation\n");
1335 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1339 * Check If the current partial trace is infeasible, while ignoring
1340 * infeasibility related to 2 RMW's reading from the same store. It does not
1341 * check end-of-execution feasibility.
1342 * @see ModelChecker::is_infeasible
1343 * @return whether the current partial trace is infeasible, ignoring multiple
1344 * RMWs reading from the same store.
1346 bool ModelChecker::is_infeasible_ignoreRMW() const
1348 if (DBG_ENABLED()) {
1349 if (mo_graph->checkForCycles())
1350 DEBUG("Infeasible: modification order cycles\n");
1351 if (priv->failed_promise)
1352 DEBUG("Infeasible: failed promise\n");
1353 if (priv->too_many_reads)
1354 DEBUG("Infeasible: too many reads\n");
1355 if (priv->bad_synchronization)
1356 DEBUG("Infeasible: bad synchronization ordering\n");
1357 if (promises_expired())
1358 DEBUG("Infeasible: promises expired\n");
1360 return mo_graph->checkForCycles() || priv->failed_promise ||
1361 priv->too_many_reads || priv->bad_synchronization ||
1365 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1366 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1367 ModelAction *lastread = get_last_action(act->get_tid());
1368 lastread->process_rmw(act);
1369 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1370 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1371 mo_graph->commitChanges();
1377 * Checks whether a thread has read from the same write for too many times
1378 * without seeing the effects of a later write.
1381 * 1) there must a different write that we could read from that would satisfy the modification order,
1382 * 2) we must have read from the same value in excess of maxreads times, and
1383 * 3) that other write must have been in the reads_from set for maxreads times.
1385 * If so, we decide that the execution is no longer feasible.
1387 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1388 if (params.maxreads != 0) {
1390 if (curr->get_node()->get_read_from_size() <= 1)
1392 //Must make sure that execution is currently feasible... We could
1393 //accidentally clear by rolling back
1394 if (is_infeasible())
1396 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1397 int tid = id_to_int(curr->get_tid());
1400 if ((int)thrd_lists->size() <= tid)
1402 action_list_t *list = &(*thrd_lists)[tid];
1404 action_list_t::reverse_iterator rit = list->rbegin();
1405 /* Skip past curr */
1406 for (; (*rit) != curr; rit++)
1408 /* go past curr now */
1411 action_list_t::reverse_iterator ritcopy = rit;
1412 //See if we have enough reads from the same value
1414 for (; count < params.maxreads; rit++,count++) {
1415 if (rit==list->rend())
1417 ModelAction *act = *rit;
1418 if (!act->is_read())
1421 if (act->get_reads_from() != rf)
1423 if (act->get_node()->get_read_from_size() <= 1)
1426 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1428 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1430 //Need a different write
1434 /* Test to see whether this is a feasible write to read from*/
1435 mo_graph->startChanges();
1436 r_modification_order(curr, write);
1437 bool feasiblereadfrom = !is_infeasible();
1438 mo_graph->rollbackChanges();
1440 if (!feasiblereadfrom)
1444 bool feasiblewrite = true;
1445 //new we need to see if this write works for everyone
1447 for (int loop = count; loop>0; loop--,rit++) {
1448 ModelAction *act=*rit;
1449 bool foundvalue = false;
1450 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1451 if (act->get_node()->get_read_from_at(j)==write) {
1457 feasiblewrite = false;
1461 if (feasiblewrite) {
1462 priv->too_many_reads = true;
1470 * Updates the mo_graph with the constraints imposed from the current
1473 * Basic idea is the following: Go through each other thread and find
1474 * the lastest action that happened before our read. Two cases:
1476 * (1) The action is a write => that write must either occur before
1477 * the write we read from or be the write we read from.
1479 * (2) The action is a read => the write that that action read from
1480 * must occur before the write we read from or be the same write.
1482 * @param curr The current action. Must be a read.
1483 * @param rf The action that curr reads from. Must be a write.
1484 * @return True if modification order edges were added; false otherwise
1486 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1488 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1491 ASSERT(curr->is_read());
1493 /* Last SC fence in the current thread */
1494 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1496 /* Iterate over all threads */
1497 for (i = 0; i < thrd_lists->size(); i++) {
1498 /* Last SC fence in thread i */
1499 ModelAction *last_sc_fence_thread_local = NULL;
1500 if (int_to_id((int)i) != curr->get_tid())
1501 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1503 /* Last SC fence in thread i, before last SC fence in current thread */
1504 ModelAction *last_sc_fence_thread_before = NULL;
1505 if (last_sc_fence_local)
1506 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1508 /* Iterate over actions in thread, starting from most recent */
1509 action_list_t *list = &(*thrd_lists)[i];
1510 action_list_t::reverse_iterator rit;
1511 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1512 ModelAction *act = *rit;
1514 if (act->is_write() && act != rf && act != curr) {
1515 /* C++, Section 29.3 statement 5 */
1516 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1517 *act < *last_sc_fence_thread_local) {
1518 mo_graph->addEdge(act, rf);
1522 /* C++, Section 29.3 statement 4 */
1523 else if (act->is_seqcst() && last_sc_fence_local &&
1524 *act < *last_sc_fence_local) {
1525 mo_graph->addEdge(act, rf);
1529 /* C++, Section 29.3 statement 6 */
1530 else if (last_sc_fence_thread_before &&
1531 *act < *last_sc_fence_thread_before) {
1532 mo_graph->addEdge(act, rf);
1539 * Include at most one act per-thread that "happens
1540 * before" curr. Don't consider reflexively.
1542 if (act->happens_before(curr) && act != curr) {
1543 if (act->is_write()) {
1545 mo_graph->addEdge(act, rf);
1549 const ModelAction *prevreadfrom = act->get_reads_from();
1550 //if the previous read is unresolved, keep going...
1551 if (prevreadfrom == NULL)
1554 if (rf != prevreadfrom) {
1555 mo_graph->addEdge(prevreadfrom, rf);
1567 /** This method fixes up the modification order when we resolve a
1568 * promises. The basic problem is that actions that occur after the
1569 * read curr could not property add items to the modification order
1572 * So for each thread, we find the earliest item that happens after
1573 * the read curr. This is the item we have to fix up with additional
1574 * constraints. If that action is write, we add a MO edge between
1575 * the Action rf and that action. If the action is a read, we add a
1576 * MO edge between the Action rf, and whatever the read accessed.
1578 * @param curr is the read ModelAction that we are fixing up MO edges for.
1579 * @param rf is the write ModelAction that curr reads from.
1582 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1584 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1586 ASSERT(curr->is_read());
1588 /* Iterate over all threads */
1589 for (i = 0; i < thrd_lists->size(); i++) {
1590 /* Iterate over actions in thread, starting from most recent */
1591 action_list_t *list = &(*thrd_lists)[i];
1592 action_list_t::reverse_iterator rit;
1593 ModelAction *lastact = NULL;
1595 /* Find last action that happens after curr that is either not curr or a rmw */
1596 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1597 ModelAction *act = *rit;
1598 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1604 /* Include at most one act per-thread that "happens before" curr */
1605 if (lastact != NULL) {
1606 if (lastact==curr) {
1607 //Case 1: The resolved read is a RMW, and we need to make sure
1608 //that the write portion of the RMW mod order after rf
1610 mo_graph->addEdge(rf, lastact);
1611 } else if (lastact->is_read()) {
1612 //Case 2: The resolved read is a normal read and the next
1613 //operation is a read, and we need to make sure the value read
1614 //is mod ordered after rf
1616 const ModelAction *postreadfrom = lastact->get_reads_from();
1617 if (postreadfrom != NULL&&rf != postreadfrom)
1618 mo_graph->addEdge(rf, postreadfrom);
1620 //Case 3: The resolved read is a normal read and the next
1621 //operation is a write, and we need to make sure that the
1622 //write is mod ordered after rf
1624 mo_graph->addEdge(rf, lastact);
1632 * Updates the mo_graph with the constraints imposed from the current write.
1634 * Basic idea is the following: Go through each other thread and find
1635 * the lastest action that happened before our write. Two cases:
1637 * (1) The action is a write => that write must occur before
1640 * (2) The action is a read => the write that that action read from
1641 * must occur before the current write.
1643 * This method also handles two other issues:
1645 * (I) Sequential Consistency: Making sure that if the current write is
1646 * seq_cst, that it occurs after the previous seq_cst write.
1648 * (II) Sending the write back to non-synchronizing reads.
1650 * @param curr The current action. Must be a write.
1651 * @return True if modification order edges were added; false otherwise
1653 bool ModelChecker::w_modification_order(ModelAction *curr)
1655 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1658 ASSERT(curr->is_write());
1660 if (curr->is_seqcst()) {
1661 /* We have to at least see the last sequentially consistent write,
1662 so we are initialized. */
1663 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1664 if (last_seq_cst != NULL) {
1665 mo_graph->addEdge(last_seq_cst, curr);
1670 /* Last SC fence in the current thread */
1671 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1673 /* Iterate over all threads */
1674 for (i = 0; i < thrd_lists->size(); i++) {
1675 /* Last SC fence in thread i, before last SC fence in current thread */
1676 ModelAction *last_sc_fence_thread_before = NULL;
1677 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1678 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1680 /* Iterate over actions in thread, starting from most recent */
1681 action_list_t *list = &(*thrd_lists)[i];
1682 action_list_t::reverse_iterator rit;
1683 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1684 ModelAction *act = *rit;
1687 * 1) If RMW and it actually read from something, then we
1688 * already have all relevant edges, so just skip to next
1691 * 2) If RMW and it didn't read from anything, we should
1692 * whatever edge we can get to speed up convergence.
1694 * 3) If normal write, we need to look at earlier actions, so
1695 * continue processing list.
1697 if (curr->is_rmw()) {
1698 if (curr->get_reads_from()!=NULL)
1706 /* C++, Section 29.3 statement 7 */
1707 if (last_sc_fence_thread_before && act->is_write() &&
1708 *act < *last_sc_fence_thread_before) {
1709 mo_graph->addEdge(act, curr);
1715 * Include at most one act per-thread that "happens
1718 if (act->happens_before(curr)) {
1720 * Note: if act is RMW, just add edge:
1722 * The following edge should be handled elsewhere:
1723 * readfrom(act) --mo--> act
1725 if (act->is_write())
1726 mo_graph->addEdge(act, curr);
1727 else if (act->is_read()) {
1728 //if previous read accessed a null, just keep going
1729 if (act->get_reads_from() == NULL)
1731 mo_graph->addEdge(act->get_reads_from(), curr);
1735 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1736 !act->same_thread(curr)) {
1737 /* We have an action that:
1738 (1) did not happen before us
1739 (2) is a read and we are a write
1740 (3) cannot synchronize with us
1741 (4) is in a different thread
1743 that read could potentially read from our write. Note that
1744 these checks are overly conservative at this point, we'll
1745 do more checks before actually removing the
1749 if (thin_air_constraint_may_allow(curr, act)) {
1750 if (!is_infeasible() ||
1751 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1752 struct PendingFutureValue pfv = {curr,act};
1753 futurevalues->push_back(pfv);
1763 /** Arbitrary reads from the future are not allowed. Section 29.3
1764 * part 9 places some constraints. This method checks one result of constraint
1765 * constraint. Others require compiler support. */
1766 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1767 if (!writer->is_rmw())
1770 if (!reader->is_rmw())
1773 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1774 if (search == reader)
1776 if (search->get_tid() == reader->get_tid() &&
1777 search->happens_before(reader))
1785 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1786 * some constraints. This method checks one the following constraint (others
1787 * require compiler support):
1789 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1791 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1793 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1795 /* Iterate over all threads */
1796 for (i = 0; i < thrd_lists->size(); i++) {
1797 const ModelAction *write_after_read = NULL;
1799 /* Iterate over actions in thread, starting from most recent */
1800 action_list_t *list = &(*thrd_lists)[i];
1801 action_list_t::reverse_iterator rit;
1802 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1803 ModelAction *act = *rit;
1805 if (!reader->happens_before(act))
1807 else if (act->is_write())
1808 write_after_read = act;
1809 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1810 write_after_read = act->get_reads_from();
1814 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1821 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1822 * The ModelAction under consideration is expected to be taking part in
1823 * release/acquire synchronization as an object of the "reads from" relation.
1824 * Note that this can only provide release sequence support for RMW chains
1825 * which do not read from the future, as those actions cannot be traced until
1826 * their "promise" is fulfilled. Similarly, we may not even establish the
1827 * presence of a release sequence with certainty, as some modification order
1828 * constraints may be decided further in the future. Thus, this function
1829 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1830 * and a boolean representing certainty.
1832 * @param rf The action that might be part of a release sequence. Must be a
1834 * @param release_heads A pass-by-reference style return parameter. After
1835 * execution of this function, release_heads will contain the heads of all the
1836 * relevant release sequences, if any exists with certainty
1837 * @param pending A pass-by-reference style return parameter which is only used
1838 * when returning false (i.e., uncertain). Returns most information regarding
1839 * an uncertain release sequence, including any write operations that might
1840 * break the sequence.
1841 * @return true, if the ModelChecker is certain that release_heads is complete;
1844 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1845 rel_heads_list_t *release_heads,
1846 struct release_seq *pending) const
1848 /* Only check for release sequences if there are no cycles */
1849 if (mo_graph->checkForCycles())
1853 ASSERT(rf->is_write());
1855 if (rf->is_release())
1856 release_heads->push_back(rf);
1857 else if (rf->get_last_fence_release())
1858 release_heads->push_back(rf->get_last_fence_release());
1860 break; /* End of RMW chain */
1862 /** @todo Need to be smarter here... In the linux lock
1863 * example, this will run to the beginning of the program for
1865 /** @todo The way to be smarter here is to keep going until 1
1866 * thread has a release preceded by an acquire and you've seen
1869 /* acq_rel RMW is a sufficient stopping condition */
1870 if (rf->is_acquire() && rf->is_release())
1871 return true; /* complete */
1873 rf = rf->get_reads_from();
1876 /* read from future: need to settle this later */
1878 return false; /* incomplete */
1881 if (rf->is_release())
1882 return true; /* complete */
1884 /* else relaxed write
1885 * - check for fence-release in the same thread (29.8, stmt. 3)
1886 * - check modification order for contiguous subsequence
1887 * -> rf must be same thread as release */
1889 const ModelAction *fence_release = rf->get_last_fence_release();
1890 /* Synchronize with a fence-release unconditionally; we don't need to
1891 * find any more "contiguous subsequence..." for it */
1893 release_heads->push_back(fence_release);
1895 int tid = id_to_int(rf->get_tid());
1896 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1897 action_list_t *list = &(*thrd_lists)[tid];
1898 action_list_t::const_reverse_iterator rit;
1900 /* Find rf in the thread list */
1901 rit = std::find(list->rbegin(), list->rend(), rf);
1902 ASSERT(rit != list->rend());
1904 /* Find the last {write,fence}-release */
1905 for (; rit != list->rend(); rit++) {
1906 if (fence_release && *(*rit) < *fence_release)
1908 if ((*rit)->is_release())
1911 if (rit == list->rend()) {
1912 /* No write-release in this thread */
1913 return true; /* complete */
1914 } else if (fence_release && *(*rit) < *fence_release) {
1915 /* The fence-release is more recent (and so, "stronger") than
1916 * the most recent write-release */
1917 return true; /* complete */
1918 } /* else, need to establish contiguous release sequence */
1919 ModelAction *release = *rit;
1921 ASSERT(rf->same_thread(release));
1923 pending->writes.clear();
1925 bool certain = true;
1926 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1927 if (id_to_int(rf->get_tid()) == (int)i)
1929 list = &(*thrd_lists)[i];
1931 /* Can we ensure no future writes from this thread may break
1932 * the release seq? */
1933 bool future_ordered = false;
1935 ModelAction *last = get_last_action(int_to_id(i));
1936 Thread *th = get_thread(int_to_id(i));
1937 if ((last && rf->happens_before(last)) ||
1940 future_ordered = true;
1942 ASSERT(!th->is_model_thread() || future_ordered);
1944 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1945 const ModelAction *act = *rit;
1946 /* Reach synchronization -> this thread is complete */
1947 if (act->happens_before(release))
1949 if (rf->happens_before(act)) {
1950 future_ordered = true;
1954 /* Only non-RMW writes can break release sequences */
1955 if (!act->is_write() || act->is_rmw())
1958 /* Check modification order */
1959 if (mo_graph->checkReachable(rf, act)) {
1960 /* rf --mo--> act */
1961 future_ordered = true;
1964 if (mo_graph->checkReachable(act, release))
1965 /* act --mo--> release */
1967 if (mo_graph->checkReachable(release, act) &&
1968 mo_graph->checkReachable(act, rf)) {
1969 /* release --mo-> act --mo--> rf */
1970 return true; /* complete */
1972 /* act may break release sequence */
1973 pending->writes.push_back(act);
1976 if (!future_ordered)
1977 certain = false; /* This thread is uncertain */
1981 release_heads->push_back(release);
1982 pending->writes.clear();
1984 pending->release = release;
1991 * An interface for getting the release sequence head(s) with which a
1992 * given ModelAction must synchronize. This function only returns a non-empty
1993 * result when it can locate a release sequence head with certainty. Otherwise,
1994 * it may mark the internal state of the ModelChecker so that it will handle
1995 * the release sequence at a later time, causing @a acquire to update its
1996 * synchronization at some later point in execution.
1998 * @param acquire The 'acquire' action that may synchronize with a release
2000 * @param read The read action that may read from a release sequence; this may
2001 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2002 * when 'acquire' is a fence-acquire)
2003 * @param release_heads A pass-by-reference return parameter. Will be filled
2004 * with the head(s) of the release sequence(s), if they exists with certainty.
2005 * @see ModelChecker::release_seq_heads
2007 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2008 ModelAction *read, rel_heads_list_t *release_heads)
2010 const ModelAction *rf = read->get_reads_from();
2011 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2012 sequence->acquire = acquire;
2013 sequence->read = read;
2015 if (!release_seq_heads(rf, release_heads, sequence)) {
2016 /* add act to 'lazy checking' list */
2017 pending_rel_seqs->push_back(sequence);
2019 snapshot_free(sequence);
2024 * Attempt to resolve all stashed operations that might synchronize with a
2025 * release sequence for a given location. This implements the "lazy" portion of
2026 * determining whether or not a release sequence was contiguous, since not all
2027 * modification order information is present at the time an action occurs.
2029 * @param location The location/object that should be checked for release
2030 * sequence resolutions. A NULL value means to check all locations.
2031 * @param work_queue The work queue to which to add work items as they are
2033 * @return True if any updates occurred (new synchronization, new mo_graph
2036 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2038 bool updated = false;
2039 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2040 while (it != pending_rel_seqs->end()) {
2041 struct release_seq *pending = *it;
2042 ModelAction *acquire = pending->acquire;
2043 const ModelAction *read = pending->read;
2045 /* Only resolve sequences on the given location, if provided */
2046 if (location && read->get_location() != location) {
2051 const ModelAction *rf = read->get_reads_from();
2052 rel_heads_list_t release_heads;
2054 complete = release_seq_heads(rf, &release_heads, pending);
2055 for (unsigned int i = 0; i < release_heads.size(); i++) {
2056 if (!acquire->has_synchronized_with(release_heads[i])) {
2057 if (acquire->synchronize_with(release_heads[i]))
2060 set_bad_synchronization();
2065 /* Re-check all pending release sequences */
2066 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2067 /* Re-check read-acquire for mo_graph edges */
2068 if (acquire->is_read())
2069 work_queue->push_back(MOEdgeWorkEntry(acquire));
2071 /* propagate synchronization to later actions */
2072 action_list_t::reverse_iterator rit = action_trace->rbegin();
2073 for (; (*rit) != acquire; rit++) {
2074 ModelAction *propagate = *rit;
2075 if (acquire->happens_before(propagate)) {
2076 propagate->synchronize_with(acquire);
2077 /* Re-check 'propagate' for mo_graph edges */
2078 work_queue->push_back(MOEdgeWorkEntry(propagate));
2083 it = pending_rel_seqs->erase(it);
2084 snapshot_free(pending);
2090 // If we resolved promises or data races, see if we have realized a data race.
2097 * Performs various bookkeeping operations for the current ModelAction. For
2098 * instance, adds action to the per-object, per-thread action vector and to the
2099 * action trace list of all thread actions.
2101 * @param act is the ModelAction to add.
2103 void ModelChecker::add_action_to_lists(ModelAction *act)
2105 int tid = id_to_int(act->get_tid());
2106 action_trace->push_back(act);
2108 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
2110 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2111 if (tid >= (int)vec->size())
2112 vec->resize(priv->next_thread_id);
2113 (*vec)[tid].push_back(act);
2115 if ((int)thrd_last_action->size() <= tid)
2116 thrd_last_action->resize(get_num_threads());
2117 (*thrd_last_action)[tid] = act;
2119 if (act->is_fence() && act->is_release()) {
2120 if ((int)thrd_last_fence_release->size() <= tid)
2121 thrd_last_fence_release->resize(get_num_threads());
2122 (*thrd_last_fence_release)[tid] = act;
2125 if (act->is_wait()) {
2126 void *mutex_loc=(void *) act->get_value();
2127 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2129 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2130 if (tid >= (int)vec->size())
2131 vec->resize(priv->next_thread_id);
2132 (*vec)[tid].push_back(act);
2137 * @brief Get the last action performed by a particular Thread
2138 * @param tid The thread ID of the Thread in question
2139 * @return The last action in the thread
2141 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2143 int threadid = id_to_int(tid);
2144 if (threadid < (int)thrd_last_action->size())
2145 return (*thrd_last_action)[id_to_int(tid)];
2151 * @brief Get the last fence release performed by a particular Thread
2152 * @param tid The thread ID of the Thread in question
2153 * @return The last fence release in the thread, if one exists; NULL otherwise
2155 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2157 int threadid = id_to_int(tid);
2158 if (threadid < (int)thrd_last_fence_release->size())
2159 return (*thrd_last_fence_release)[id_to_int(tid)];
2165 * Gets the last memory_order_seq_cst write (in the total global sequence)
2166 * performed on a particular object (i.e., memory location), not including the
2168 * @param curr The current ModelAction; also denotes the object location to
2170 * @return The last seq_cst write
2172 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2174 void *location = curr->get_location();
2175 action_list_t *list = get_safe_ptr_action(obj_map, location);
2176 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2177 action_list_t::reverse_iterator rit;
2178 for (rit = list->rbegin(); rit != list->rend(); rit++)
2179 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2185 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2186 * performed in a particular thread, prior to a particular fence.
2187 * @param tid The ID of the thread to check
2188 * @param before_fence The fence from which to begin the search; if NULL, then
2189 * search for the most recent fence in the thread.
2190 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2192 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2194 /* All fences should have NULL location */
2195 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2196 action_list_t::reverse_iterator rit = list->rbegin();
2199 for (; rit != list->rend(); rit++)
2200 if (*rit == before_fence)
2203 ASSERT(*rit == before_fence);
2207 for (; rit != list->rend(); rit++)
2208 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2214 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2215 * location). This function identifies the mutex according to the current
2216 * action, which is presumed to perform on the same mutex.
2217 * @param curr The current ModelAction; also denotes the object location to
2219 * @return The last unlock operation
2221 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2223 void *location = curr->get_location();
2224 action_list_t *list = get_safe_ptr_action(obj_map, location);
2225 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2226 action_list_t::reverse_iterator rit;
2227 for (rit = list->rbegin(); rit != list->rend(); rit++)
2228 if ((*rit)->is_unlock() || (*rit)->is_wait())
2233 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2235 ModelAction *parent = get_last_action(tid);
2237 parent = get_thread(tid)->get_creation();
2242 * Returns the clock vector for a given thread.
2243 * @param tid The thread whose clock vector we want
2244 * @return Desired clock vector
2246 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2248 return get_parent_action(tid)->get_cv();
2252 * Resolve a set of Promises with a current write. The set is provided in the
2253 * Node corresponding to @a write.
2254 * @param write The ModelAction that is fulfilling Promises
2255 * @return True if promises were resolved; false otherwise
2257 bool ModelChecker::resolve_promises(ModelAction *write)
2259 bool resolved = false;
2260 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2262 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2263 Promise *promise = (*promises)[promise_index];
2264 if (write->get_node()->get_promise(i)) {
2265 ModelAction *read = promise->get_action();
2266 if (read->is_rmw()) {
2267 mo_graph->addRMWEdge(write, read);
2269 read_from(read, write);
2270 //First fix up the modification order for actions that happened
2272 r_modification_order(read, write);
2273 //Next fix up the modification order for actions that happened
2275 post_r_modification_order(read, write);
2276 //Make sure the promise's value matches the write's value
2277 ASSERT(promise->get_value() == write->get_value());
2280 promises->erase(promises->begin() + promise_index);
2281 threads_to_check.push_back(read->get_tid());
2288 //Check whether reading these writes has made threads unable to
2291 for(unsigned int i=0;i<threads_to_check.size();i++)
2292 mo_check_promises(threads_to_check[i], write);
2298 * Compute the set of promises that could potentially be satisfied by this
2299 * action. Note that the set computation actually appears in the Node, not in
2301 * @param curr The ModelAction that may satisfy promises
2303 void ModelChecker::compute_promises(ModelAction *curr)
2305 for (unsigned int i = 0; i < promises->size(); i++) {
2306 Promise *promise = (*promises)[i];
2307 const ModelAction *act = promise->get_action();
2308 if (!act->happens_before(curr) &&
2310 !act->could_synchronize_with(curr) &&
2311 !act->same_thread(curr) &&
2312 act->get_location() == curr->get_location() &&
2313 promise->get_value() == curr->get_value()) {
2314 curr->get_node()->set_promise(i, act->is_rmw());
2319 /** Checks promises in response to change in ClockVector Threads. */
2320 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2322 for (unsigned int i = 0; i < promises->size(); i++) {
2323 Promise *promise = (*promises)[i];
2324 const ModelAction *act = promise->get_action();
2325 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2326 merge_cv->synchronized_since(act)) {
2327 if (promise->increment_threads(tid)) {
2328 //Promise has failed
2329 priv->failed_promise = true;
2336 void ModelChecker::check_promises_thread_disabled() {
2337 for (unsigned int i = 0; i < promises->size(); i++) {
2338 Promise *promise = (*promises)[i];
2339 if (promise->check_promise()) {
2340 priv->failed_promise = true;
2346 /** Checks promises in response to addition to modification order for threads.
2348 * pthread is the thread that performed the read that created the promise
2350 * pread is the read that created the promise
2352 * pwrite is either the first write to same location as pread by
2353 * pthread that is sequenced after pread or the value read by the
2354 * first read to the same lcoation as pread by pthread that is
2355 * sequenced after pread..
2357 * 1. If tid=pthread, then we check what other threads are reachable
2358 * through the mode order starting with pwrite. Those threads cannot
2359 * perform a write that will resolve the promise due to modification
2360 * order constraints.
2362 * 2. If the tid is not pthread, we check whether pwrite can reach the
2363 * action write through the modification order. If so, that thread
2364 * cannot perform a future write that will resolve the promise due to
2365 * modificatin order constraints.
2367 * @parem tid The thread that either read from the model action
2368 * write, or actually did the model action write.
2370 * @parem write The ModelAction representing the relevant write.
2373 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2374 void * location = write->get_location();
2375 for (unsigned int i = 0; i < promises->size(); i++) {
2376 Promise *promise = (*promises)[i];
2377 const ModelAction *act = promise->get_action();
2379 //Is this promise on the same location?
2380 if ( act->get_location() != location )
2383 //same thread as the promise
2384 if ( act->get_tid()==tid ) {
2386 //do we have a pwrite for the promise, if not, set it
2387 if (promise->get_write() == NULL ) {
2388 promise->set_write(write);
2389 //The pwrite cannot happen before the promise
2390 if (write->happens_before(act) && (write != act)) {
2391 priv->failed_promise = true;
2395 if (mo_graph->checkPromise(write, promise)) {
2396 priv->failed_promise = true;
2401 //Don't do any lookups twice for the same thread
2402 if (promise->has_sync_thread(tid))
2405 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2406 if (promise->increment_threads(tid)) {
2407 priv->failed_promise = true;
2415 * Compute the set of writes that may break the current pending release
2416 * sequence. This information is extracted from previou release sequence
2419 * @param curr The current ModelAction. Must be a release sequence fixup
2422 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2424 if (pending_rel_seqs->empty())
2427 struct release_seq *pending = pending_rel_seqs->back();
2428 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2429 const ModelAction *write = pending->writes[i];
2430 curr->get_node()->add_relseq_break(write);
2433 /* NULL means don't break the sequence; just synchronize */
2434 curr->get_node()->add_relseq_break(NULL);
2438 * Build up an initial set of all past writes that this 'read' action may read
2439 * from. This set is determined by the clock vector's "happens before"
2441 * @param curr is the current ModelAction that we are exploring; it must be a
2444 void ModelChecker::build_reads_from_past(ModelAction *curr)
2446 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2448 ASSERT(curr->is_read());
2450 ModelAction *last_sc_write = NULL;
2452 /* Track whether this object has been initialized */
2453 bool initialized = false;
2455 if (curr->is_seqcst()) {
2456 last_sc_write = get_last_seq_cst_write(curr);
2457 /* We have to at least see the last sequentially consistent write,
2458 so we are initialized. */
2459 if (last_sc_write != NULL)
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 DEBUG("Adding action to may_read_from:\n");
2485 if (DBG_ENABLED()) {
2489 curr->get_node()->add_read_from(act);
2492 /* Include at most one act per-thread that "happens before" curr */
2493 if (act->happens_before(curr)) {
2501 assert_bug("May read from uninitialized atomic");
2503 if (DBG_ENABLED() || !initialized) {
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) {
2514 Node *prevnode=write->get_node()->get_parent();
2516 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2517 if (write->is_release()&&thread_sleep)
2519 if (!write->is_rmw()) {
2522 if (write->get_reads_from()==NULL)
2524 write=write->get_reads_from();
2528 static void print_list(action_list_t *list, int exec_num = -1)
2530 action_list_t::iterator it;
2532 model_print("---------------------------------------------------------------------\n");
2534 model_print("Execution %d:\n", exec_num);
2536 unsigned int hash=0;
2538 for (it = list->begin(); it != list->end(); it++) {
2540 hash=hash^(hash<<3)^((*it)->hash());
2542 model_print("HASH %u\n", hash);
2543 model_print("---------------------------------------------------------------------\n");
2546 #if SUPPORT_MOD_ORDER_DUMP
2547 void ModelChecker::dumpGraph(char *filename) {
2549 sprintf(buffer, "%s.dot",filename);
2550 FILE *file=fopen(buffer, "w");
2551 fprintf(file, "digraph %s {\n",filename);
2552 mo_graph->dumpNodes(file);
2553 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2555 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2556 ModelAction *action=*it;
2557 if (action->is_read()) {
2558 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2559 if (action->get_reads_from()!=NULL)
2560 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2562 if (thread_array[action->get_tid()] != NULL) {
2563 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2566 thread_array[action->get_tid()]=action;
2568 fprintf(file,"}\n");
2569 model_free(thread_array);
2574 /** @brief Prints an execution trace summary. */
2575 void ModelChecker::print_summary() const
2577 #if SUPPORT_MOD_ORDER_DUMP
2579 char buffername[100];
2580 sprintf(buffername, "exec%04u", stats.num_total);
2581 mo_graph->dumpGraphToFile(buffername);
2582 sprintf(buffername, "graph%04u", stats.num_total);
2583 dumpGraph(buffername);
2586 if (!isfeasibleprefix())
2587 model_print("INFEASIBLE EXECUTION!\n");
2588 print_list(action_trace, stats.num_total);
2593 * Add a Thread to the system for the first time. Should only be called once
2595 * @param t The Thread to add
2597 void ModelChecker::add_thread(Thread *t)
2599 thread_map->put(id_to_int(t->get_id()), t);
2600 scheduler->add_thread(t);
2604 * Removes a thread from the scheduler.
2605 * @param the thread to remove.
2607 void ModelChecker::remove_thread(Thread *t)
2609 scheduler->remove_thread(t);
2613 * @brief Get a Thread reference by its ID
2614 * @param tid The Thread's ID
2615 * @return A Thread reference
2617 Thread * ModelChecker::get_thread(thread_id_t tid) const
2619 return thread_map->get(id_to_int(tid));
2623 * @brief Get a reference to the Thread in which a ModelAction was executed
2624 * @param act The ModelAction
2625 * @return A Thread reference
2627 Thread * ModelChecker::get_thread(ModelAction *act) const
2629 return get_thread(act->get_tid());
2633 * @brief Check if a Thread is currently enabled
2634 * @param t The Thread to check
2635 * @return True if the Thread is currently enabled
2637 bool ModelChecker::is_enabled(Thread *t) const
2639 return scheduler->is_enabled(t);
2643 * @brief Check if a Thread is currently enabled
2644 * @param tid The ID of the Thread to check
2645 * @return True if the Thread is currently enabled
2647 bool ModelChecker::is_enabled(thread_id_t tid) const
2649 return scheduler->is_enabled(tid);
2653 * Switch from a user-context to the "master thread" context (a.k.a. system
2654 * context). This switch is made with the intention of exploring a particular
2655 * model-checking action (described by a ModelAction object). Must be called
2656 * from a user-thread context.
2658 * @param act The current action that will be explored. May be NULL only if
2659 * trace is exiting via an assertion (see ModelChecker::set_assert and
2660 * ModelChecker::has_asserted).
2661 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2663 int ModelChecker::switch_to_master(ModelAction *act)
2666 Thread *old = thread_current();
2667 set_current_action(act);
2668 old->set_state(THREAD_READY);
2669 return Thread::swap(old, &system_context);
2673 * Takes the next step in the execution, if possible.
2674 * @return Returns true (success) if a step was taken and false otherwise.
2676 bool ModelChecker::take_step() {
2680 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2682 if (curr->get_state() == THREAD_READY) {
2683 ASSERT(priv->current_action);
2685 priv->nextThread = check_current_action(priv->current_action);
2686 priv->current_action = NULL;
2688 if (curr->is_blocked() || curr->is_complete())
2689 scheduler->remove_thread(curr);
2694 Thread *next = scheduler->next_thread(priv->nextThread);
2696 /* Infeasible -> don't take any more steps */
2697 if (is_infeasible())
2699 else if (isfeasibleprefix() && have_bug_reports()) {
2704 if (params.bound != 0) {
2705 if (priv->used_sequence_numbers > params.bound) {
2710 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2711 next ? id_to_int(next->get_id()) : -1);
2714 * Launch end-of-execution release sequence fixups only when there are:
2716 * (1) no more user threads to run (or when execution replay chooses
2717 * the 'model_thread')
2718 * (2) pending release sequences
2719 * (3) pending assertions (i.e., data races)
2720 * (4) no pending promises
2722 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2723 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2724 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2725 pending_rel_seqs->size());
2726 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2727 std::memory_order_seq_cst, NULL, VALUE_NONE,
2729 set_current_action(fixup);
2733 /* next == NULL -> don't take any more steps */
2737 next->set_state(THREAD_RUNNING);
2739 if (next->get_pending() != NULL) {
2740 /* restart a pending action */
2741 set_current_action(next->get_pending());
2742 next->set_pending(NULL);
2743 next->set_state(THREAD_READY);
2747 /* Return false only if swap fails with an error */
2748 return (Thread::swap(&system_context, next) == 0);
2751 /** Wrapper to run the user's main function, with appropriate arguments */
2752 void user_main_wrapper(void *)
2754 user_main(model->params.argc, model->params.argv);
2757 /** @brief Run ModelChecker for the user program */
2758 void ModelChecker::run()
2763 /* Start user program */
2764 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2766 /* Wait for all threads to complete */
2767 while (take_step());
2768 } while (next_execution());