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);
1521 /* C++, Section 29.3 statement 4 */
1522 else if (act->is_seqcst() && last_sc_fence_local &&
1523 *act < *last_sc_fence_local) {
1524 mo_graph->addEdge(act, rf);
1527 /* C++, Section 29.3 statement 6 */
1528 else if (last_sc_fence_thread_before &&
1529 *act < *last_sc_fence_thread_before) {
1530 mo_graph->addEdge(act, rf);
1536 * Include at most one act per-thread that "happens
1537 * before" curr. Don't consider reflexively.
1539 if (act->happens_before(curr) && act != curr) {
1540 if (act->is_write()) {
1542 mo_graph->addEdge(act, rf);
1546 const ModelAction *prevreadfrom = act->get_reads_from();
1547 //if the previous read is unresolved, keep going...
1548 if (prevreadfrom == NULL)
1551 if (rf != prevreadfrom) {
1552 mo_graph->addEdge(prevreadfrom, rf);
1564 /** This method fixes up the modification order when we resolve a
1565 * promises. The basic problem is that actions that occur after the
1566 * read curr could not property add items to the modification order
1569 * So for each thread, we find the earliest item that happens after
1570 * the read curr. This is the item we have to fix up with additional
1571 * constraints. If that action is write, we add a MO edge between
1572 * the Action rf and that action. If the action is a read, we add a
1573 * MO edge between the Action rf, and whatever the read accessed.
1575 * @param curr is the read ModelAction that we are fixing up MO edges for.
1576 * @param rf is the write ModelAction that curr reads from.
1579 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1581 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1583 ASSERT(curr->is_read());
1585 /* Iterate over all threads */
1586 for (i = 0; i < thrd_lists->size(); i++) {
1587 /* Iterate over actions in thread, starting from most recent */
1588 action_list_t *list = &(*thrd_lists)[i];
1589 action_list_t::reverse_iterator rit;
1590 ModelAction *lastact = NULL;
1592 /* Find last action that happens after curr that is either not curr or a rmw */
1593 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1594 ModelAction *act = *rit;
1595 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1601 /* Include at most one act per-thread that "happens before" curr */
1602 if (lastact != NULL) {
1603 if (lastact==curr) {
1604 //Case 1: The resolved read is a RMW, and we need to make sure
1605 //that the write portion of the RMW mod order after rf
1607 mo_graph->addEdge(rf, lastact);
1608 } else if (lastact->is_read()) {
1609 //Case 2: The resolved read is a normal read and the next
1610 //operation is a read, and we need to make sure the value read
1611 //is mod ordered after rf
1613 const ModelAction *postreadfrom = lastact->get_reads_from();
1614 if (postreadfrom != NULL&&rf != postreadfrom)
1615 mo_graph->addEdge(rf, postreadfrom);
1617 //Case 3: The resolved read is a normal read and the next
1618 //operation is a write, and we need to make sure that the
1619 //write is mod ordered after rf
1621 mo_graph->addEdge(rf, lastact);
1629 * Updates the mo_graph with the constraints imposed from the current write.
1631 * Basic idea is the following: Go through each other thread and find
1632 * the lastest action that happened before our write. Two cases:
1634 * (1) The action is a write => that write must occur before
1637 * (2) The action is a read => the write that that action read from
1638 * must occur before the current write.
1640 * This method also handles two other issues:
1642 * (I) Sequential Consistency: Making sure that if the current write is
1643 * seq_cst, that it occurs after the previous seq_cst write.
1645 * (II) Sending the write back to non-synchronizing reads.
1647 * @param curr The current action. Must be a write.
1648 * @return True if modification order edges were added; false otherwise
1650 bool ModelChecker::w_modification_order(ModelAction *curr)
1652 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1655 ASSERT(curr->is_write());
1657 if (curr->is_seqcst()) {
1658 /* We have to at least see the last sequentially consistent write,
1659 so we are initialized. */
1660 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1661 if (last_seq_cst != NULL) {
1662 mo_graph->addEdge(last_seq_cst, curr);
1667 /* Last SC fence in the current thread */
1668 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1670 /* Iterate over all threads */
1671 for (i = 0; i < thrd_lists->size(); i++) {
1672 /* Last SC fence in thread i, before last SC fence in current thread */
1673 ModelAction *last_sc_fence_thread_before = NULL;
1674 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1675 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1677 /* Iterate over actions in thread, starting from most recent */
1678 action_list_t *list = &(*thrd_lists)[i];
1679 action_list_t::reverse_iterator rit;
1680 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1681 ModelAction *act = *rit;
1684 * 1) If RMW and it actually read from something, then we
1685 * already have all relevant edges, so just skip to next
1688 * 2) If RMW and it didn't read from anything, we should
1689 * whatever edge we can get to speed up convergence.
1691 * 3) If normal write, we need to look at earlier actions, so
1692 * continue processing list.
1694 if (curr->is_rmw()) {
1695 if (curr->get_reads_from()!=NULL)
1703 /* C++, Section 29.3 statement 7 */
1704 if (last_sc_fence_thread_before && act->is_write() &&
1705 *act < *last_sc_fence_thread_before) {
1706 mo_graph->addEdge(act, curr);
1711 * Include at most one act per-thread that "happens
1714 if (act->happens_before(curr)) {
1716 * Note: if act is RMW, just add edge:
1718 * The following edge should be handled elsewhere:
1719 * readfrom(act) --mo--> act
1721 if (act->is_write())
1722 mo_graph->addEdge(act, curr);
1723 else if (act->is_read()) {
1724 //if previous read accessed a null, just keep going
1725 if (act->get_reads_from() == NULL)
1727 mo_graph->addEdge(act->get_reads_from(), curr);
1731 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1732 !act->same_thread(curr)) {
1733 /* We have an action that:
1734 (1) did not happen before us
1735 (2) is a read and we are a write
1736 (3) cannot synchronize with us
1737 (4) is in a different thread
1739 that read could potentially read from our write. Note that
1740 these checks are overly conservative at this point, we'll
1741 do more checks before actually removing the
1745 if (thin_air_constraint_may_allow(curr, act)) {
1746 if (!is_infeasible() ||
1747 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1748 struct PendingFutureValue pfv = {curr,act};
1749 futurevalues->push_back(pfv);
1759 /** Arbitrary reads from the future are not allowed. Section 29.3
1760 * part 9 places some constraints. This method checks one result of constraint
1761 * constraint. Others require compiler support. */
1762 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1763 if (!writer->is_rmw())
1766 if (!reader->is_rmw())
1769 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1770 if (search == reader)
1772 if (search->get_tid() == reader->get_tid() &&
1773 search->happens_before(reader))
1781 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1782 * some constraints. This method checks one the following constraint (others
1783 * require compiler support):
1785 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1787 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1789 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1791 /* Iterate over all threads */
1792 for (i = 0; i < thrd_lists->size(); i++) {
1793 const ModelAction *write_after_read = NULL;
1795 /* Iterate over actions in thread, starting from most recent */
1796 action_list_t *list = &(*thrd_lists)[i];
1797 action_list_t::reverse_iterator rit;
1798 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1799 ModelAction *act = *rit;
1801 if (!reader->happens_before(act))
1803 else if (act->is_write())
1804 write_after_read = act;
1805 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1806 write_after_read = act->get_reads_from();
1810 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1817 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1818 * The ModelAction under consideration is expected to be taking part in
1819 * release/acquire synchronization as an object of the "reads from" relation.
1820 * Note that this can only provide release sequence support for RMW chains
1821 * which do not read from the future, as those actions cannot be traced until
1822 * their "promise" is fulfilled. Similarly, we may not even establish the
1823 * presence of a release sequence with certainty, as some modification order
1824 * constraints may be decided further in the future. Thus, this function
1825 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1826 * and a boolean representing certainty.
1828 * @param rf The action that might be part of a release sequence. Must be a
1830 * @param release_heads A pass-by-reference style return parameter. After
1831 * execution of this function, release_heads will contain the heads of all the
1832 * relevant release sequences, if any exists with certainty
1833 * @param pending A pass-by-reference style return parameter which is only used
1834 * when returning false (i.e., uncertain). Returns most information regarding
1835 * an uncertain release sequence, including any write operations that might
1836 * break the sequence.
1837 * @return true, if the ModelChecker is certain that release_heads is complete;
1840 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1841 rel_heads_list_t *release_heads,
1842 struct release_seq *pending) const
1844 /* Only check for release sequences if there are no cycles */
1845 if (mo_graph->checkForCycles())
1849 ASSERT(rf->is_write());
1851 if (rf->is_release())
1852 release_heads->push_back(rf);
1853 else if (rf->get_last_fence_release())
1854 release_heads->push_back(rf->get_last_fence_release());
1856 break; /* End of RMW chain */
1858 /** @todo Need to be smarter here... In the linux lock
1859 * example, this will run to the beginning of the program for
1861 /** @todo The way to be smarter here is to keep going until 1
1862 * thread has a release preceded by an acquire and you've seen
1865 /* acq_rel RMW is a sufficient stopping condition */
1866 if (rf->is_acquire() && rf->is_release())
1867 return true; /* complete */
1869 rf = rf->get_reads_from();
1872 /* read from future: need to settle this later */
1874 return false; /* incomplete */
1877 if (rf->is_release())
1878 return true; /* complete */
1880 /* else relaxed write
1881 * - check for fence-release in the same thread (29.8, stmt. 3)
1882 * - check modification order for contiguous subsequence
1883 * -> rf must be same thread as release */
1885 const ModelAction *fence_release = rf->get_last_fence_release();
1886 /* Synchronize with a fence-release unconditionally; we don't need to
1887 * find any more "contiguous subsequence..." for it */
1889 release_heads->push_back(fence_release);
1891 int tid = id_to_int(rf->get_tid());
1892 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1893 action_list_t *list = &(*thrd_lists)[tid];
1894 action_list_t::const_reverse_iterator rit;
1896 /* Find rf in the thread list */
1897 rit = std::find(list->rbegin(), list->rend(), rf);
1898 ASSERT(rit != list->rend());
1900 /* Find the last {write,fence}-release */
1901 for (; rit != list->rend(); rit++) {
1902 if (fence_release && *(*rit) < *fence_release)
1904 if ((*rit)->is_release())
1907 if (rit == list->rend()) {
1908 /* No write-release in this thread */
1909 return true; /* complete */
1910 } else if (fence_release && *(*rit) < *fence_release) {
1911 /* The fence-release is more recent (and so, "stronger") than
1912 * the most recent write-release */
1913 return true; /* complete */
1914 } /* else, need to establish contiguous release sequence */
1915 ModelAction *release = *rit;
1917 ASSERT(rf->same_thread(release));
1919 pending->writes.clear();
1921 bool certain = true;
1922 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1923 if (id_to_int(rf->get_tid()) == (int)i)
1925 list = &(*thrd_lists)[i];
1927 /* Can we ensure no future writes from this thread may break
1928 * the release seq? */
1929 bool future_ordered = false;
1931 ModelAction *last = get_last_action(int_to_id(i));
1932 Thread *th = get_thread(int_to_id(i));
1933 if ((last && rf->happens_before(last)) ||
1936 future_ordered = true;
1938 ASSERT(!th->is_model_thread() || future_ordered);
1940 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1941 const ModelAction *act = *rit;
1942 /* Reach synchronization -> this thread is complete */
1943 if (act->happens_before(release))
1945 if (rf->happens_before(act)) {
1946 future_ordered = true;
1950 /* Only non-RMW writes can break release sequences */
1951 if (!act->is_write() || act->is_rmw())
1954 /* Check modification order */
1955 if (mo_graph->checkReachable(rf, act)) {
1956 /* rf --mo--> act */
1957 future_ordered = true;
1960 if (mo_graph->checkReachable(act, release))
1961 /* act --mo--> release */
1963 if (mo_graph->checkReachable(release, act) &&
1964 mo_graph->checkReachable(act, rf)) {
1965 /* release --mo-> act --mo--> rf */
1966 return true; /* complete */
1968 /* act may break release sequence */
1969 pending->writes.push_back(act);
1972 if (!future_ordered)
1973 certain = false; /* This thread is uncertain */
1977 release_heads->push_back(release);
1978 pending->writes.clear();
1980 pending->release = release;
1987 * An interface for getting the release sequence head(s) with which a
1988 * given ModelAction must synchronize. This function only returns a non-empty
1989 * result when it can locate a release sequence head with certainty. Otherwise,
1990 * it may mark the internal state of the ModelChecker so that it will handle
1991 * the release sequence at a later time, causing @a acquire to update its
1992 * synchronization at some later point in execution.
1994 * @param acquire The 'acquire' action that may synchronize with a release
1996 * @param read The read action that may read from a release sequence; this may
1997 * be the same as acquire, or else an earlier action in the same thread (i.e.,
1998 * when 'acquire' is a fence-acquire)
1999 * @param release_heads A pass-by-reference return parameter. Will be filled
2000 * with the head(s) of the release sequence(s), if they exists with certainty.
2001 * @see ModelChecker::release_seq_heads
2003 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2004 ModelAction *read, rel_heads_list_t *release_heads)
2006 const ModelAction *rf = read->get_reads_from();
2007 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2008 sequence->acquire = acquire;
2009 sequence->read = read;
2011 if (!release_seq_heads(rf, release_heads, sequence)) {
2012 /* add act to 'lazy checking' list */
2013 pending_rel_seqs->push_back(sequence);
2015 snapshot_free(sequence);
2020 * Attempt to resolve all stashed operations that might synchronize with a
2021 * release sequence for a given location. This implements the "lazy" portion of
2022 * determining whether or not a release sequence was contiguous, since not all
2023 * modification order information is present at the time an action occurs.
2025 * @param location The location/object that should be checked for release
2026 * sequence resolutions. A NULL value means to check all locations.
2027 * @param work_queue The work queue to which to add work items as they are
2029 * @return True if any updates occurred (new synchronization, new mo_graph
2032 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2034 bool updated = false;
2035 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2036 while (it != pending_rel_seqs->end()) {
2037 struct release_seq *pending = *it;
2038 ModelAction *acquire = pending->acquire;
2039 const ModelAction *read = pending->read;
2041 /* Only resolve sequences on the given location, if provided */
2042 if (location && read->get_location() != location) {
2047 const ModelAction *rf = read->get_reads_from();
2048 rel_heads_list_t release_heads;
2050 complete = release_seq_heads(rf, &release_heads, pending);
2051 for (unsigned int i = 0; i < release_heads.size(); i++) {
2052 if (!acquire->has_synchronized_with(release_heads[i])) {
2053 if (acquire->synchronize_with(release_heads[i]))
2056 set_bad_synchronization();
2061 /* Re-check all pending release sequences */
2062 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2063 /* Re-check read-acquire for mo_graph edges */
2064 if (acquire->is_read())
2065 work_queue->push_back(MOEdgeWorkEntry(acquire));
2067 /* propagate synchronization to later actions */
2068 action_list_t::reverse_iterator rit = action_trace->rbegin();
2069 for (; (*rit) != acquire; rit++) {
2070 ModelAction *propagate = *rit;
2071 if (acquire->happens_before(propagate)) {
2072 propagate->synchronize_with(acquire);
2073 /* Re-check 'propagate' for mo_graph edges */
2074 work_queue->push_back(MOEdgeWorkEntry(propagate));
2079 it = pending_rel_seqs->erase(it);
2080 snapshot_free(pending);
2086 // If we resolved promises or data races, see if we have realized a data race.
2093 * Performs various bookkeeping operations for the current ModelAction. For
2094 * instance, adds action to the per-object, per-thread action vector and to the
2095 * action trace list of all thread actions.
2097 * @param act is the ModelAction to add.
2099 void ModelChecker::add_action_to_lists(ModelAction *act)
2101 int tid = id_to_int(act->get_tid());
2102 action_trace->push_back(act);
2104 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
2106 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2107 if (tid >= (int)vec->size())
2108 vec->resize(priv->next_thread_id);
2109 (*vec)[tid].push_back(act);
2111 if ((int)thrd_last_action->size() <= tid)
2112 thrd_last_action->resize(get_num_threads());
2113 (*thrd_last_action)[tid] = act;
2115 if (act->is_fence() && act->is_release()) {
2116 if ((int)thrd_last_fence_release->size() <= tid)
2117 thrd_last_fence_release->resize(get_num_threads());
2118 (*thrd_last_fence_release)[tid] = act;
2121 if (act->is_wait()) {
2122 void *mutex_loc=(void *) act->get_value();
2123 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2125 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2126 if (tid >= (int)vec->size())
2127 vec->resize(priv->next_thread_id);
2128 (*vec)[tid].push_back(act);
2133 * @brief Get the last action performed by a particular Thread
2134 * @param tid The thread ID of the Thread in question
2135 * @return The last action in the thread
2137 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2139 int threadid = id_to_int(tid);
2140 if (threadid < (int)thrd_last_action->size())
2141 return (*thrd_last_action)[id_to_int(tid)];
2147 * @brief Get the last fence release performed by a particular Thread
2148 * @param tid The thread ID of the Thread in question
2149 * @return The last fence release in the thread, if one exists; NULL otherwise
2151 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2153 int threadid = id_to_int(tid);
2154 if (threadid < (int)thrd_last_fence_release->size())
2155 return (*thrd_last_fence_release)[id_to_int(tid)];
2161 * Gets the last memory_order_seq_cst write (in the total global sequence)
2162 * performed on a particular object (i.e., memory location), not including the
2164 * @param curr The current ModelAction; also denotes the object location to
2166 * @return The last seq_cst write
2168 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2170 void *location = curr->get_location();
2171 action_list_t *list = get_safe_ptr_action(obj_map, location);
2172 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2173 action_list_t::reverse_iterator rit;
2174 for (rit = list->rbegin(); rit != list->rend(); rit++)
2175 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2181 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2182 * performed in a particular thread, prior to a particular fence.
2183 * @param tid The ID of the thread to check
2184 * @param before_fence The fence from which to begin the search; if NULL, then
2185 * search for the most recent fence in the thread.
2186 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2188 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2190 /* All fences should have NULL location */
2191 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2192 action_list_t::reverse_iterator rit = list->rbegin();
2195 for (; rit != list->rend(); rit++)
2196 if (*rit == before_fence)
2199 ASSERT(*rit == before_fence);
2203 for (; rit != list->rend(); rit++)
2204 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2210 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2211 * location). This function identifies the mutex according to the current
2212 * action, which is presumed to perform on the same mutex.
2213 * @param curr The current ModelAction; also denotes the object location to
2215 * @return The last unlock operation
2217 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2219 void *location = curr->get_location();
2220 action_list_t *list = get_safe_ptr_action(obj_map, location);
2221 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2222 action_list_t::reverse_iterator rit;
2223 for (rit = list->rbegin(); rit != list->rend(); rit++)
2224 if ((*rit)->is_unlock() || (*rit)->is_wait())
2229 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2231 ModelAction *parent = get_last_action(tid);
2233 parent = get_thread(tid)->get_creation();
2238 * Returns the clock vector for a given thread.
2239 * @param tid The thread whose clock vector we want
2240 * @return Desired clock vector
2242 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2244 return get_parent_action(tid)->get_cv();
2248 * Resolve a set of Promises with a current write. The set is provided in the
2249 * Node corresponding to @a write.
2250 * @param write The ModelAction that is fulfilling Promises
2251 * @return True if promises were resolved; false otherwise
2253 bool ModelChecker::resolve_promises(ModelAction *write)
2255 bool resolved = false;
2256 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2258 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2259 Promise *promise = (*promises)[promise_index];
2260 if (write->get_node()->get_promise(i)) {
2261 ModelAction *read = promise->get_action();
2262 if (read->is_rmw()) {
2263 mo_graph->addRMWEdge(write, read);
2265 read_from(read, write);
2266 //First fix up the modification order for actions that happened
2268 r_modification_order(read, write);
2269 //Next fix up the modification order for actions that happened
2271 post_r_modification_order(read, write);
2272 //Make sure the promise's value matches the write's value
2273 ASSERT(promise->get_value() == write->get_value());
2276 promises->erase(promises->begin() + promise_index);
2277 threads_to_check.push_back(read->get_tid());
2284 //Check whether reading these writes has made threads unable to
2287 for(unsigned int i=0;i<threads_to_check.size();i++)
2288 mo_check_promises(threads_to_check[i], write);
2294 * Compute the set of promises that could potentially be satisfied by this
2295 * action. Note that the set computation actually appears in the Node, not in
2297 * @param curr The ModelAction that may satisfy promises
2299 void ModelChecker::compute_promises(ModelAction *curr)
2301 for (unsigned int i = 0; i < promises->size(); i++) {
2302 Promise *promise = (*promises)[i];
2303 const ModelAction *act = promise->get_action();
2304 if (!act->happens_before(curr) &&
2306 !act->could_synchronize_with(curr) &&
2307 !act->same_thread(curr) &&
2308 act->get_location() == curr->get_location() &&
2309 promise->get_value() == curr->get_value()) {
2310 curr->get_node()->set_promise(i, act->is_rmw());
2315 /** Checks promises in response to change in ClockVector Threads. */
2316 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2318 for (unsigned int i = 0; i < promises->size(); i++) {
2319 Promise *promise = (*promises)[i];
2320 const ModelAction *act = promise->get_action();
2321 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2322 merge_cv->synchronized_since(act)) {
2323 if (promise->increment_threads(tid)) {
2324 //Promise has failed
2325 priv->failed_promise = true;
2332 void ModelChecker::check_promises_thread_disabled() {
2333 for (unsigned int i = 0; i < promises->size(); i++) {
2334 Promise *promise = (*promises)[i];
2335 if (promise->check_promise()) {
2336 priv->failed_promise = true;
2342 /** Checks promises in response to addition to modification order for threads.
2344 * pthread is the thread that performed the read that created the promise
2346 * pread is the read that created the promise
2348 * pwrite is either the first write to same location as pread by
2349 * pthread that is sequenced after pread or the value read by the
2350 * first read to the same lcoation as pread by pthread that is
2351 * sequenced after pread..
2353 * 1. If tid=pthread, then we check what other threads are reachable
2354 * through the mode order starting with pwrite. Those threads cannot
2355 * perform a write that will resolve the promise due to modification
2356 * order constraints.
2358 * 2. If the tid is not pthread, we check whether pwrite can reach the
2359 * action write through the modification order. If so, that thread
2360 * cannot perform a future write that will resolve the promise due to
2361 * modificatin order constraints.
2363 * @parem tid The thread that either read from the model action
2364 * write, or actually did the model action write.
2366 * @parem write The ModelAction representing the relevant write.
2369 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2370 void * location = write->get_location();
2371 for (unsigned int i = 0; i < promises->size(); i++) {
2372 Promise *promise = (*promises)[i];
2373 const ModelAction *act = promise->get_action();
2375 //Is this promise on the same location?
2376 if ( act->get_location() != location )
2379 //same thread as the promise
2380 if ( act->get_tid()==tid ) {
2382 //do we have a pwrite for the promise, if not, set it
2383 if (promise->get_write() == NULL ) {
2384 promise->set_write(write);
2385 //The pwrite cannot happen before the promise
2386 if (write->happens_before(act) && (write != act)) {
2387 priv->failed_promise = true;
2391 if (mo_graph->checkPromise(write, promise)) {
2392 priv->failed_promise = true;
2397 //Don't do any lookups twice for the same thread
2398 if (promise->has_sync_thread(tid))
2401 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2402 if (promise->increment_threads(tid)) {
2403 priv->failed_promise = true;
2411 * Compute the set of writes that may break the current pending release
2412 * sequence. This information is extracted from previou release sequence
2415 * @param curr The current ModelAction. Must be a release sequence fixup
2418 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2420 if (pending_rel_seqs->empty())
2423 struct release_seq *pending = pending_rel_seqs->back();
2424 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2425 const ModelAction *write = pending->writes[i];
2426 curr->get_node()->add_relseq_break(write);
2429 /* NULL means don't break the sequence; just synchronize */
2430 curr->get_node()->add_relseq_break(NULL);
2434 * Build up an initial set of all past writes that this 'read' action may read
2435 * from. This set is determined by the clock vector's "happens before"
2437 * @param curr is the current ModelAction that we are exploring; it must be a
2440 void ModelChecker::build_reads_from_past(ModelAction *curr)
2442 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2444 ASSERT(curr->is_read());
2446 ModelAction *last_sc_write = NULL;
2448 /* Track whether this object has been initialized */
2449 bool initialized = false;
2451 if (curr->is_seqcst()) {
2452 last_sc_write = get_last_seq_cst_write(curr);
2453 /* We have to at least see the last sequentially consistent write,
2454 so we are initialized. */
2455 if (last_sc_write != NULL)
2459 /* Iterate over all threads */
2460 for (i = 0; i < thrd_lists->size(); i++) {
2461 /* Iterate over actions in thread, starting from most recent */
2462 action_list_t *list = &(*thrd_lists)[i];
2463 action_list_t::reverse_iterator rit;
2464 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2465 ModelAction *act = *rit;
2467 /* Only consider 'write' actions */
2468 if (!act->is_write() || act == curr)
2471 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2472 bool allow_read = true;
2474 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2476 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2480 DEBUG("Adding action to may_read_from:\n");
2481 if (DBG_ENABLED()) {
2485 curr->get_node()->add_read_from(act);
2488 /* Include at most one act per-thread that "happens before" curr */
2489 if (act->happens_before(curr)) {
2497 assert_bug("May read from uninitialized atomic");
2499 if (DBG_ENABLED() || !initialized) {
2500 model_print("Reached read action:\n");
2502 model_print("Printing may_read_from\n");
2503 curr->get_node()->print_may_read_from();
2504 model_print("End printing may_read_from\n");
2508 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2510 Node *prevnode=write->get_node()->get_parent();
2512 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2513 if (write->is_release()&&thread_sleep)
2515 if (!write->is_rmw()) {
2518 if (write->get_reads_from()==NULL)
2520 write=write->get_reads_from();
2524 static void print_list(action_list_t *list, int exec_num = -1)
2526 action_list_t::iterator it;
2528 model_print("---------------------------------------------------------------------\n");
2530 model_print("Execution %d:\n", exec_num);
2532 unsigned int hash=0;
2534 for (it = list->begin(); it != list->end(); it++) {
2536 hash=hash^(hash<<3)^((*it)->hash());
2538 model_print("HASH %u\n", hash);
2539 model_print("---------------------------------------------------------------------\n");
2542 #if SUPPORT_MOD_ORDER_DUMP
2543 void ModelChecker::dumpGraph(char *filename) {
2545 sprintf(buffer, "%s.dot",filename);
2546 FILE *file=fopen(buffer, "w");
2547 fprintf(file, "digraph %s {\n",filename);
2548 mo_graph->dumpNodes(file);
2549 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2551 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2552 ModelAction *action=*it;
2553 if (action->is_read()) {
2554 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2555 if (action->get_reads_from()!=NULL)
2556 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2558 if (thread_array[action->get_tid()] != NULL) {
2559 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2562 thread_array[action->get_tid()]=action;
2564 fprintf(file,"}\n");
2565 model_free(thread_array);
2570 /** @brief Prints an execution trace summary. */
2571 void ModelChecker::print_summary() const
2573 #if SUPPORT_MOD_ORDER_DUMP
2575 char buffername[100];
2576 sprintf(buffername, "exec%04u", stats.num_total);
2577 mo_graph->dumpGraphToFile(buffername);
2578 sprintf(buffername, "graph%04u", stats.num_total);
2579 dumpGraph(buffername);
2582 if (!isfeasibleprefix())
2583 model_print("INFEASIBLE EXECUTION!\n");
2584 print_list(action_trace, stats.num_total);
2589 * Add a Thread to the system for the first time. Should only be called once
2591 * @param t The Thread to add
2593 void ModelChecker::add_thread(Thread *t)
2595 thread_map->put(id_to_int(t->get_id()), t);
2596 scheduler->add_thread(t);
2600 * Removes a thread from the scheduler.
2601 * @param the thread to remove.
2603 void ModelChecker::remove_thread(Thread *t)
2605 scheduler->remove_thread(t);
2609 * @brief Get a Thread reference by its ID
2610 * @param tid The Thread's ID
2611 * @return A Thread reference
2613 Thread * ModelChecker::get_thread(thread_id_t tid) const
2615 return thread_map->get(id_to_int(tid));
2619 * @brief Get a reference to the Thread in which a ModelAction was executed
2620 * @param act The ModelAction
2621 * @return A Thread reference
2623 Thread * ModelChecker::get_thread(ModelAction *act) const
2625 return get_thread(act->get_tid());
2629 * @brief Check if a Thread is currently enabled
2630 * @param t The Thread to check
2631 * @return True if the Thread is currently enabled
2633 bool ModelChecker::is_enabled(Thread *t) const
2635 return scheduler->is_enabled(t);
2639 * @brief Check if a Thread is currently enabled
2640 * @param tid The ID of the Thread to check
2641 * @return True if the Thread is currently enabled
2643 bool ModelChecker::is_enabled(thread_id_t tid) const
2645 return scheduler->is_enabled(tid);
2649 * Switch from a user-context to the "master thread" context (a.k.a. system
2650 * context). This switch is made with the intention of exploring a particular
2651 * model-checking action (described by a ModelAction object). Must be called
2652 * from a user-thread context.
2654 * @param act The current action that will be explored. May be NULL only if
2655 * trace is exiting via an assertion (see ModelChecker::set_assert and
2656 * ModelChecker::has_asserted).
2657 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2659 int ModelChecker::switch_to_master(ModelAction *act)
2662 Thread *old = thread_current();
2663 set_current_action(act);
2664 old->set_state(THREAD_READY);
2665 return Thread::swap(old, &system_context);
2669 * Takes the next step in the execution, if possible.
2670 * @return Returns true (success) if a step was taken and false otherwise.
2672 bool ModelChecker::take_step() {
2676 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2678 if (curr->get_state() == THREAD_READY) {
2679 ASSERT(priv->current_action);
2681 priv->nextThread = check_current_action(priv->current_action);
2682 priv->current_action = NULL;
2684 if (curr->is_blocked() || curr->is_complete())
2685 scheduler->remove_thread(curr);
2690 Thread *next = scheduler->next_thread(priv->nextThread);
2692 /* Infeasible -> don't take any more steps */
2693 if (is_infeasible())
2695 else if (isfeasibleprefix() && have_bug_reports()) {
2700 if (params.bound != 0) {
2701 if (priv->used_sequence_numbers > params.bound) {
2706 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2707 next ? id_to_int(next->get_id()) : -1);
2710 * Launch end-of-execution release sequence fixups only when there are:
2712 * (1) no more user threads to run (or when execution replay chooses
2713 * the 'model_thread')
2714 * (2) pending release sequences
2715 * (3) pending assertions (i.e., data races)
2716 * (4) no pending promises
2718 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2719 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2720 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2721 pending_rel_seqs->size());
2722 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2723 std::memory_order_seq_cst, NULL, VALUE_NONE,
2725 set_current_action(fixup);
2729 /* next == NULL -> don't take any more steps */
2733 next->set_state(THREAD_RUNNING);
2735 if (next->get_pending() != NULL) {
2736 /* restart a pending action */
2737 set_current_action(next->get_pending());
2738 next->set_pending(NULL);
2739 next->set_state(THREAD_READY);
2743 /* Return false only if swap fails with an error */
2744 return (Thread::swap(&system_context, next) == 0);
2747 /** Wrapper to run the user's main function, with appropriate arguments */
2748 void user_main_wrapper(void *)
2750 user_main(model->params.argc, model->params.argv);
2753 /** @brief Run ModelChecker for the user program */
2754 void ModelChecker::run()
2759 /* Start user program */
2760 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2762 /* Wait for all threads to complete */
2763 while (take_step());
2764 } while (next_execution());