10 #include "snapshot-interface.h"
12 #include "clockvector.h"
13 #include "cyclegraph.h"
16 #include "threads-model.h"
19 #define INITIAL_THREAD_ID 0
24 bug_message(const char *str) {
25 const char *fmt = " [BUG] %s\n";
26 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
27 sprintf(msg, fmt, str);
29 ~bug_message() { if (msg) snapshot_free(msg); }
32 void print() { model_print("%s", msg); }
38 * Structure for holding small ModelChecker members that should be snapshotted
40 struct model_snapshot_members {
41 model_snapshot_members() :
43 /* First thread created will have id INITIAL_THREAD_ID */
44 next_thread_id(INITIAL_THREAD_ID),
45 used_sequence_numbers(0),
49 failed_promise(false),
50 too_many_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 ModelAction *current_action;
62 unsigned int next_thread_id;
63 modelclock_t used_sequence_numbers;
64 ModelAction *next_backtrack;
65 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
66 struct execution_stats stats;
69 /** @brief Incorrectly-ordered synchronization was made */
70 bool bad_synchronization;
76 /** @brief Constructor */
77 ModelChecker::ModelChecker(struct model_params params) :
78 /* Initialize default scheduler */
80 scheduler(new Scheduler()),
82 earliest_diverge(NULL),
83 action_trace(new action_list_t()),
84 thread_map(new HashTable<int, Thread *, int>()),
85 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
86 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
89 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
90 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
91 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
92 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
93 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
123 delete thrd_last_fence_release;
130 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
132 action_list_t *tmp = hash->get(ptr);
134 tmp = new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
142 std::vector<action_list_t> *tmp = hash->get(ptr);
144 tmp = new std::vector<action_list_t>();
151 * Restores user program to initial state and resets all model-checker data
154 void ModelChecker::reset_to_initial_state()
156 DEBUG("+++ Resetting to initial state +++\n");
157 node_stack->reset_execution();
159 /* Print all model-checker output before rollback */
162 snapshot_backtrack_before(0);
165 /** @return a thread ID for a new Thread */
166 thread_id_t ModelChecker::get_next_id()
168 return priv->next_thread_id++;
171 /** @return the number of user threads created during this execution */
172 unsigned int ModelChecker::get_num_threads() const
174 return priv->next_thread_id;
178 * Must be called from user-thread context (e.g., through the global
179 * thread_current() interface)
181 * @return The currently executing Thread.
183 Thread * ModelChecker::get_current_thread() const
185 return scheduler->get_current_thread();
188 /** @return a sequence number for a new ModelAction */
189 modelclock_t ModelChecker::get_next_seq_num()
191 return ++priv->used_sequence_numbers;
194 Node * ModelChecker::get_curr_node() const
196 return node_stack->get_head();
200 * @brief Choose the next thread to execute.
202 * This function chooses the next thread that should execute. It can force the
203 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
204 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
205 * The model-checker may have no preference regarding the next thread (i.e.,
206 * when exploring a new execution ordering), in which case this will return
208 * @param curr The current ModelAction. This action might guide the choice of
210 * @return The next thread to run. If the model-checker has no preference, NULL.
212 Thread * ModelChecker::get_next_thread(ModelAction *curr)
217 /* Do not split atomic actions. */
219 return thread_current();
220 else if (curr->get_type() == THREAD_CREATE)
221 return curr->get_thread_operand();
224 /* Have we completed exploring the preselected path? */
228 /* Else, we are trying to replay an execution */
229 ModelAction *next = node_stack->get_next()->get_action();
231 if (next == diverge) {
232 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
233 earliest_diverge = diverge;
235 Node *nextnode = next->get_node();
236 Node *prevnode = nextnode->get_parent();
237 scheduler->update_sleep_set(prevnode);
239 /* Reached divergence point */
240 if (nextnode->increment_misc()) {
241 /* The next node will try to satisfy a different misc_index values. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_promise()) {
245 /* The next node will try to satisfy a different set of promises. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_read_from()) {
249 /* The next node will read from a different value. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_future_value()) {
253 /* The next node will try to read from a different future value. */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
256 } else if (nextnode->increment_relseq_break()) {
257 /* The next node will try to resolve a release sequence differently */
258 tid = next->get_tid();
259 node_stack->pop_restofstack(2);
262 /* Make a different thread execute for next step */
263 scheduler->add_sleep(get_thread(next->get_tid()));
264 tid = prevnode->get_next_backtrack();
265 /* Make sure the backtracked thread isn't sleeping. */
266 node_stack->pop_restofstack(1);
267 if (diverge == earliest_diverge) {
268 earliest_diverge = prevnode->get_action();
271 /* The correct sleep set is in the parent node. */
274 DEBUG("*** Divergence point ***\n");
278 tid = next->get_tid();
280 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
281 ASSERT(tid != THREAD_ID_T_NONE);
282 return thread_map->get(id_to_int(tid));
286 * We need to know what the next actions of all threads in the sleep
287 * set will be. This method computes them and stores the actions at
288 * the corresponding thread object's pending action.
291 void ModelChecker::execute_sleep_set()
293 for (unsigned int i = 0; i < get_num_threads(); i++) {
294 thread_id_t tid = int_to_id(i);
295 Thread *thr = get_thread(tid);
296 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
297 thr->set_state(THREAD_RUNNING);
298 scheduler->next_thread(thr);
299 Thread::swap(&system_context, thr);
300 priv->current_action->set_sleep_flag();
301 thr->set_pending(priv->current_action);
306 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
308 for (unsigned int i = 0; i < get_num_threads(); i++) {
309 Thread *thr = get_thread(int_to_id(i));
310 if (scheduler->is_sleep_set(thr)) {
311 ModelAction *pending_act = thr->get_pending();
312 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
313 //Remove this thread from sleep set
314 scheduler->remove_sleep(thr);
319 /** @brief Alert the model-checker that an incorrectly-ordered
320 * synchronization was made */
321 void ModelChecker::set_bad_synchronization()
323 priv->bad_synchronization = true;
326 bool ModelChecker::has_asserted() const
328 return priv->asserted;
331 void ModelChecker::set_assert()
333 priv->asserted = true;
337 * Check if we are in a deadlock. Should only be called at the end of an
338 * execution, although it should not give false positives in the middle of an
339 * execution (there should be some ENABLED thread).
341 * @return True if program is in a deadlock; false otherwise
343 bool ModelChecker::is_deadlocked() const
345 bool blocking_threads = false;
346 for (unsigned int i = 0; i < get_num_threads(); i++) {
347 thread_id_t tid = int_to_id(i);
350 Thread *t = get_thread(tid);
351 if (!t->is_model_thread() && t->get_pending())
352 blocking_threads = true;
354 return blocking_threads;
358 * Check if this is a complete execution. That is, have all thread completed
359 * execution (rather than exiting because sleep sets have forced a redundant
362 * @return True if the execution is complete.
364 bool ModelChecker::is_complete_execution() const
366 for (unsigned int i = 0; i < get_num_threads(); i++)
367 if (is_enabled(int_to_id(i)))
373 * @brief Assert a bug in the executing program.
375 * Use this function to assert any sort of bug in the user program. If the
376 * current trace is feasible (actually, a prefix of some feasible execution),
377 * then this execution will be aborted, printing the appropriate message. If
378 * the current trace is not yet feasible, the error message will be stashed and
379 * printed if the execution ever becomes feasible.
381 * @param msg Descriptive message for the bug (do not include newline char)
382 * @return True if bug is immediately-feasible
384 bool ModelChecker::assert_bug(const char *msg)
386 priv->bugs.push_back(new bug_message(msg));
388 if (isfeasibleprefix()) {
396 * @brief Assert a bug in the executing program, asserted by a user thread
397 * @see ModelChecker::assert_bug
398 * @param msg Descriptive message for the bug (do not include newline char)
400 void ModelChecker::assert_user_bug(const char *msg)
402 /* If feasible bug, bail out now */
404 switch_to_master(NULL);
407 /** @return True, if any bugs have been reported for this execution */
408 bool ModelChecker::have_bug_reports() const
410 return priv->bugs.size() != 0;
413 /** @brief Print bug report listing for this execution (if any bugs exist) */
414 void ModelChecker::print_bugs() const
416 if (have_bug_reports()) {
417 model_print("Bug report: %zu bug%s detected\n",
419 priv->bugs.size() > 1 ? "s" : "");
420 for (unsigned int i = 0; i < priv->bugs.size(); i++)
421 priv->bugs[i]->print();
426 * @brief Record end-of-execution stats
428 * Must be run when exiting an execution. Records various stats.
429 * @see struct execution_stats
431 void ModelChecker::record_stats()
434 if (!isfeasibleprefix())
435 stats.num_infeasible++;
436 else if (have_bug_reports())
437 stats.num_buggy_executions++;
438 else if (is_complete_execution())
439 stats.num_complete++;
441 stats.num_redundant++;
444 /** @brief Print execution stats */
445 void ModelChecker::print_stats() const
447 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
448 model_print("Number of redundant executions: %d\n", stats.num_redundant);
449 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
450 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
451 model_print("Total executions: %d\n", stats.num_total);
452 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
456 * @brief End-of-exeuction print
457 * @param printbugs Should any existing bugs be printed?
459 void ModelChecker::print_execution(bool printbugs) const
461 print_program_output();
463 if (DBG_ENABLED() || params.verbose) {
464 model_print("Earliest divergence point since last feasible execution:\n");
465 if (earliest_diverge)
466 earliest_diverge->print();
468 model_print("(Not set)\n");
474 /* Don't print invalid bugs */
483 * Queries the model-checker for more executions to explore and, if one
484 * exists, resets the model-checker state to execute a new execution.
486 * @return If there are more executions to explore, return true. Otherwise,
489 bool ModelChecker::next_execution()
492 /* Is this execution a feasible execution that's worth bug-checking? */
493 bool complete = isfeasibleprefix() && (is_complete_execution() ||
496 /* End-of-execution bug checks */
499 assert_bug("Deadlock detected");
507 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
508 print_execution(complete);
510 clear_program_output();
513 earliest_diverge = NULL;
515 if ((diverge = get_next_backtrack()) == NULL)
519 model_print("Next execution will diverge at:\n");
523 reset_to_initial_state();
527 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
529 switch (act->get_type()) {
534 /* Optimization: relaxed operations don't need backtracking */
535 if (act->is_relaxed())
537 /* linear search: from most recent to oldest */
538 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
539 action_list_t::reverse_iterator rit;
540 for (rit = list->rbegin(); rit != list->rend(); rit++) {
541 ModelAction *prev = *rit;
542 if (prev->could_synchronize_with(act))
548 case ATOMIC_TRYLOCK: {
549 /* linear search: from most recent to oldest */
550 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
551 action_list_t::reverse_iterator rit;
552 for (rit = list->rbegin(); rit != list->rend(); rit++) {
553 ModelAction *prev = *rit;
554 if (act->is_conflicting_lock(prev))
559 case ATOMIC_UNLOCK: {
560 /* linear search: from most recent to oldest */
561 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
562 action_list_t::reverse_iterator rit;
563 for (rit = list->rbegin(); rit != list->rend(); rit++) {
564 ModelAction *prev = *rit;
565 if (!act->same_thread(prev) && prev->is_failed_trylock())
571 /* linear search: from most recent to oldest */
572 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
573 action_list_t::reverse_iterator rit;
574 for (rit = list->rbegin(); rit != list->rend(); rit++) {
575 ModelAction *prev = *rit;
576 if (!act->same_thread(prev) && prev->is_failed_trylock())
578 if (!act->same_thread(prev) && prev->is_notify())
584 case ATOMIC_NOTIFY_ALL:
585 case ATOMIC_NOTIFY_ONE: {
586 /* linear search: from most recent to oldest */
587 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
588 action_list_t::reverse_iterator rit;
589 for (rit = list->rbegin(); rit != list->rend(); rit++) {
590 ModelAction *prev = *rit;
591 if (!act->same_thread(prev) && prev->is_wait())
602 /** This method finds backtracking points where we should try to
603 * reorder the parameter ModelAction against.
605 * @param the ModelAction to find backtracking points for.
607 void ModelChecker::set_backtracking(ModelAction *act)
609 Thread *t = get_thread(act);
610 ModelAction *prev = get_last_conflict(act);
614 Node *node = prev->get_node()->get_parent();
616 int low_tid, high_tid;
617 if (node->is_enabled(t)) {
618 low_tid = id_to_int(act->get_tid());
619 high_tid = low_tid + 1;
622 high_tid = get_num_threads();
625 for (int i = low_tid; i < high_tid; i++) {
626 thread_id_t tid = int_to_id(i);
628 /* Make sure this thread can be enabled here. */
629 if (i >= node->get_num_threads())
632 /* Don't backtrack into a point where the thread is disabled or sleeping. */
633 if (node->enabled_status(tid) != THREAD_ENABLED)
636 /* Check if this has been explored already */
637 if (node->has_been_explored(tid))
640 /* See if fairness allows */
641 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
643 for (int t = 0; t < node->get_num_threads(); t++) {
644 thread_id_t tother = int_to_id(t);
645 if (node->is_enabled(tother) && node->has_priority(tother)) {
653 /* Cache the latest backtracking point */
654 set_latest_backtrack(prev);
656 /* If this is a new backtracking point, mark the tree */
657 if (!node->set_backtrack(tid))
659 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
660 id_to_int(prev->get_tid()),
661 id_to_int(t->get_id()));
670 * @brief Cache the a backtracking point as the "most recent", if eligible
672 * Note that this does not prepare the NodeStack for this backtracking
673 * operation, it only caches the action on a per-execution basis
675 * @param act The operation at which we should explore a different next action
676 * (i.e., backtracking point)
677 * @return True, if this action is now the most recent backtracking point;
680 bool ModelChecker::set_latest_backtrack(ModelAction *act)
682 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
683 priv->next_backtrack = act;
690 * Returns last backtracking point. The model checker will explore a different
691 * path for this point in the next execution.
692 * @return The ModelAction at which the next execution should diverge.
694 ModelAction * ModelChecker::get_next_backtrack()
696 ModelAction *next = priv->next_backtrack;
697 priv->next_backtrack = NULL;
702 * Processes a read or rmw model action.
703 * @param curr is the read model action to process.
704 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
705 * @return True if processing this read updates the mo_graph.
707 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
709 uint64_t value = VALUE_NONE;
710 bool updated = false;
712 const ModelAction *reads_from = curr->get_node()->get_read_from();
713 if (reads_from != NULL) {
714 mo_graph->startChanges();
716 value = reads_from->get_value();
717 bool r_status = false;
719 if (!second_part_of_rmw) {
720 check_recency(curr, reads_from);
721 r_status = r_modification_order(curr, reads_from);
725 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
726 mo_graph->rollbackChanges();
727 priv->too_many_reads = false;
731 read_from(curr, reads_from);
732 mo_graph->commitChanges();
733 mo_check_promises(curr->get_tid(), reads_from);
736 } else if (!second_part_of_rmw) {
737 /* Read from future value */
738 value = curr->get_node()->get_future_value();
739 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
740 curr->set_read_from(NULL);
741 Promise *valuepromise = new Promise(curr, value, expiration);
742 promises->push_back(valuepromise);
744 get_thread(curr)->set_return_value(value);
750 * Processes a lock, trylock, or unlock model action. @param curr is
751 * the read model action to process.
753 * The try lock operation checks whether the lock is taken. If not,
754 * it falls to the normal lock operation case. If so, it returns
757 * The lock operation has already been checked that it is enabled, so
758 * it just grabs the lock and synchronizes with the previous unlock.
760 * The unlock operation has to re-enable all of the threads that are
761 * waiting on the lock.
763 * @return True if synchronization was updated; false otherwise
765 bool ModelChecker::process_mutex(ModelAction *curr)
767 std::mutex *mutex = NULL;
768 struct std::mutex_state *state = NULL;
770 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
771 mutex = (std::mutex *)curr->get_location();
772 state = mutex->get_state();
773 } else if (curr->is_wait()) {
774 mutex = (std::mutex *)curr->get_value();
775 state = mutex->get_state();
778 switch (curr->get_type()) {
779 case ATOMIC_TRYLOCK: {
780 bool success = !state->islocked;
781 curr->set_try_lock(success);
783 get_thread(curr)->set_return_value(0);
786 get_thread(curr)->set_return_value(1);
788 //otherwise fall into the lock case
790 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
791 assert_bug("Lock access before initialization");
792 state->islocked = true;
793 ModelAction *unlock = get_last_unlock(curr);
794 //synchronize with the previous unlock statement
795 if (unlock != NULL) {
796 curr->synchronize_with(unlock);
801 case ATOMIC_UNLOCK: {
803 state->islocked = false;
804 //wake up the other threads
805 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
806 //activate all the waiting threads
807 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
808 scheduler->wake(get_thread(*rit));
815 state->islocked = false;
816 //wake up the other threads
817 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
818 //activate all the waiting threads
819 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
820 scheduler->wake(get_thread(*rit));
823 //check whether we should go to sleep or not...simulate spurious failures
824 if (curr->get_node()->get_misc() == 0) {
825 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
827 scheduler->sleep(get_thread(curr));
831 case ATOMIC_NOTIFY_ALL: {
832 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
833 //activate all the waiting threads
834 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
835 scheduler->wake(get_thread(*rit));
840 case ATOMIC_NOTIFY_ONE: {
841 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
842 int wakeupthread = curr->get_node()->get_misc();
843 action_list_t::iterator it = waiters->begin();
844 advance(it, wakeupthread);
845 scheduler->wake(get_thread(*it));
857 * Process a write ModelAction
858 * @param curr The ModelAction to process
859 * @return True if the mo_graph was updated or promises were resolved
861 bool ModelChecker::process_write(ModelAction *curr)
863 bool updated_mod_order = w_modification_order(curr);
864 bool updated_promises = resolve_promises(curr);
866 if (promises->size() == 0) {
867 for (unsigned int i = 0; i < futurevalues->size(); i++) {
868 struct PendingFutureValue pfv = (*futurevalues)[i];
869 //Do more ambitious checks now that mo is more complete
870 if (mo_may_allow(pfv.writer, pfv.act) &&
871 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number() + params.maxfuturedelay))
872 set_latest_backtrack(pfv.act);
874 futurevalues->clear();
877 mo_graph->commitChanges();
878 mo_check_promises(curr->get_tid(), curr);
880 get_thread(curr)->set_return_value(VALUE_NONE);
881 return updated_mod_order || updated_promises;
885 * Process a fence ModelAction
886 * @param curr The ModelAction to process
887 * @return True if synchronization was updated
889 bool ModelChecker::process_fence(ModelAction *curr)
892 * fence-relaxed: no-op
893 * fence-release: only log the occurence (not in this function), for
894 * use in later synchronization
895 * fence-acquire (this function): search for hypothetical release
898 bool updated = false;
899 if (curr->is_acquire()) {
900 action_list_t *list = action_trace;
901 action_list_t::reverse_iterator rit;
902 /* Find X : is_read(X) && X --sb-> curr */
903 for (rit = list->rbegin(); rit != list->rend(); rit++) {
904 ModelAction *act = *rit;
907 if (act->get_tid() != curr->get_tid())
909 /* Stop at the beginning of the thread */
910 if (act->is_thread_start())
912 /* Stop once we reach a prior fence-acquire */
913 if (act->is_fence() && act->is_acquire())
917 /* read-acquire will find its own release sequences */
918 if (act->is_acquire())
921 /* Establish hypothetical release sequences */
922 rel_heads_list_t release_heads;
923 get_release_seq_heads(curr, act, &release_heads);
924 for (unsigned int i = 0; i < release_heads.size(); i++)
925 if (!curr->synchronize_with(release_heads[i]))
926 set_bad_synchronization();
927 if (release_heads.size() != 0)
935 * @brief Process the current action for thread-related activity
937 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
938 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
939 * synchronization, etc. This function is a no-op for non-THREAD actions
940 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
942 * @param curr The current action
943 * @return True if synchronization was updated or a thread completed
945 bool ModelChecker::process_thread_action(ModelAction *curr)
947 bool updated = false;
949 switch (curr->get_type()) {
950 case THREAD_CREATE: {
951 Thread *th = curr->get_thread_operand();
952 th->set_creation(curr);
956 Thread *blocking = curr->get_thread_operand();
957 ModelAction *act = get_last_action(blocking->get_id());
958 curr->synchronize_with(act);
959 updated = true; /* trigger rel-seq checks */
962 case THREAD_FINISH: {
963 Thread *th = get_thread(curr);
964 while (!th->wait_list_empty()) {
965 ModelAction *act = th->pop_wait_list();
966 scheduler->wake(get_thread(act));
969 updated = true; /* trigger rel-seq checks */
973 check_promises(curr->get_tid(), NULL, curr->get_cv());
984 * @brief Process the current action for release sequence fixup activity
986 * Performs model-checker release sequence fixups for the current action,
987 * forcing a single pending release sequence to break (with a given, potential
988 * "loose" write) or to complete (i.e., synchronize). If a pending release
989 * sequence forms a complete release sequence, then we must perform the fixup
990 * synchronization, mo_graph additions, etc.
992 * @param curr The current action; must be a release sequence fixup action
993 * @param work_queue The work queue to which to add work items as they are
996 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
998 const ModelAction *write = curr->get_node()->get_relseq_break();
999 struct release_seq *sequence = pending_rel_seqs->back();
1000 pending_rel_seqs->pop_back();
1002 ModelAction *acquire = sequence->acquire;
1003 const ModelAction *rf = sequence->rf;
1004 const ModelAction *release = sequence->release;
1008 ASSERT(release->same_thread(rf));
1010 if (write == NULL) {
1012 * @todo Forcing a synchronization requires that we set
1013 * modification order constraints. For instance, we can't allow
1014 * a fixup sequence in which two separate read-acquire
1015 * operations read from the same sequence, where the first one
1016 * synchronizes and the other doesn't. Essentially, we can't
1017 * allow any writes to insert themselves between 'release' and
1021 /* Must synchronize */
1022 if (!acquire->synchronize_with(release)) {
1023 set_bad_synchronization();
1026 /* Re-check all pending release sequences */
1027 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1028 /* Re-check act for mo_graph edges */
1029 work_queue->push_back(MOEdgeWorkEntry(acquire));
1031 /* propagate synchronization to later actions */
1032 action_list_t::reverse_iterator rit = action_trace->rbegin();
1033 for (; (*rit) != acquire; rit++) {
1034 ModelAction *propagate = *rit;
1035 if (acquire->happens_before(propagate)) {
1036 propagate->synchronize_with(acquire);
1037 /* Re-check 'propagate' for mo_graph edges */
1038 work_queue->push_back(MOEdgeWorkEntry(propagate));
1042 /* Break release sequence with new edges:
1043 * release --mo--> write --mo--> rf */
1044 mo_graph->addEdge(release, write);
1045 mo_graph->addEdge(write, rf);
1048 /* See if we have realized a data race */
1053 * Initialize the current action by performing one or more of the following
1054 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1055 * in the NodeStack, manipulating backtracking sets, allocating and
1056 * initializing clock vectors, and computing the promises to fulfill.
1058 * @param curr The current action, as passed from the user context; may be
1059 * freed/invalidated after the execution of this function, with a different
1060 * action "returned" its place (pass-by-reference)
1061 * @return True if curr is a newly-explored action; false otherwise
1063 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1065 ModelAction *newcurr;
1067 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1068 newcurr = process_rmw(*curr);
1071 if (newcurr->is_rmw())
1072 compute_promises(newcurr);
1078 (*curr)->set_seq_number(get_next_seq_num());
1080 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1082 /* First restore type and order in case of RMW operation */
1083 if ((*curr)->is_rmwr())
1084 newcurr->copy_typeandorder(*curr);
1086 ASSERT((*curr)->get_location() == newcurr->get_location());
1087 newcurr->copy_from_new(*curr);
1089 /* Discard duplicate ModelAction; use action from NodeStack */
1092 /* Always compute new clock vector */
1093 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1096 return false; /* Action was explored previously */
1100 /* Always compute new clock vector */
1101 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1103 /* Assign most recent release fence */
1104 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1107 * Perform one-time actions when pushing new ModelAction onto
1110 if (newcurr->is_write())
1111 compute_promises(newcurr);
1112 else if (newcurr->is_relseq_fixup())
1113 compute_relseq_breakwrites(newcurr);
1114 else if (newcurr->is_wait())
1115 newcurr->get_node()->set_misc_max(2);
1116 else if (newcurr->is_notify_one()) {
1117 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1119 return true; /* This was a new ModelAction */
1124 * @brief Establish reads-from relation between two actions
1126 * Perform basic operations involved with establishing a concrete rf relation,
1127 * including setting the ModelAction data and checking for release sequences.
1129 * @param act The action that is reading (must be a read)
1130 * @param rf The action from which we are reading (must be a write)
1132 * @return True if this read established synchronization
1134 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1136 act->set_read_from(rf);
1137 if (rf != NULL && act->is_acquire()) {
1138 rel_heads_list_t release_heads;
1139 get_release_seq_heads(act, act, &release_heads);
1140 int num_heads = release_heads.size();
1141 for (unsigned int i = 0; i < release_heads.size(); i++)
1142 if (!act->synchronize_with(release_heads[i])) {
1143 set_bad_synchronization();
1146 return num_heads > 0;
1152 * @brief Check whether a model action is enabled.
1154 * Checks whether a lock or join operation would be successful (i.e., is the
1155 * lock already locked, or is the joined thread already complete). If not, put
1156 * the action in a waiter list.
1158 * @param curr is the ModelAction to check whether it is enabled.
1159 * @return a bool that indicates whether the action is enabled.
1161 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1162 if (curr->is_lock()) {
1163 std::mutex *lock = (std::mutex *)curr->get_location();
1164 struct std::mutex_state *state = lock->get_state();
1165 if (state->islocked) {
1166 //Stick the action in the appropriate waiting queue
1167 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1170 } else if (curr->get_type() == THREAD_JOIN) {
1171 Thread *blocking = (Thread *)curr->get_location();
1172 if (!blocking->is_complete()) {
1173 blocking->push_wait_list(curr);
1182 * Stores the ModelAction for the current thread action. Call this
1183 * immediately before switching from user- to system-context to pass
1184 * data between them.
1185 * @param act The ModelAction created by the user-thread action
1187 void ModelChecker::set_current_action(ModelAction *act) {
1188 priv->current_action = act;
1192 * This is the heart of the model checker routine. It performs model-checking
1193 * actions corresponding to a given "current action." Among other processes, it
1194 * calculates reads-from relationships, updates synchronization clock vectors,
1195 * forms a memory_order constraints graph, and handles replay/backtrack
1196 * execution when running permutations of previously-observed executions.
1198 * @param curr The current action to process
1199 * @return The ModelAction that is actually executed; may be different than
1200 * curr; may be NULL, if the current action is not enabled to run
1202 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1205 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1207 if (!check_action_enabled(curr)) {
1208 /* Make the execution look like we chose to run this action
1209 * much later, when a lock/join can succeed */
1210 get_thread(curr)->set_pending(curr);
1211 scheduler->sleep(get_thread(curr));
1215 bool newly_explored = initialize_curr_action(&curr);
1221 wake_up_sleeping_actions(curr);
1223 /* Add the action to lists before any other model-checking tasks */
1224 if (!second_part_of_rmw)
1225 add_action_to_lists(curr);
1227 /* Build may_read_from set for newly-created actions */
1228 if (newly_explored && curr->is_read())
1229 build_reads_from_past(curr);
1231 /* Initialize work_queue with the "current action" work */
1232 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1233 while (!work_queue.empty() && !has_asserted()) {
1234 WorkQueueEntry work = work_queue.front();
1235 work_queue.pop_front();
1237 switch (work.type) {
1238 case WORK_CHECK_CURR_ACTION: {
1239 ModelAction *act = work.action;
1240 bool update = false; /* update this location's release seq's */
1241 bool update_all = false; /* update all release seq's */
1243 if (process_thread_action(curr))
1246 if (act->is_read() && process_read(act, second_part_of_rmw))
1249 if (act->is_write() && process_write(act))
1252 if (act->is_fence() && process_fence(act))
1255 if (act->is_mutex_op() && process_mutex(act))
1258 if (act->is_relseq_fixup())
1259 process_relseq_fixup(curr, &work_queue);
1262 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1264 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1267 case WORK_CHECK_RELEASE_SEQ:
1268 resolve_release_sequences(work.location, &work_queue);
1270 case WORK_CHECK_MO_EDGES: {
1271 /** @todo Complete verification of work_queue */
1272 ModelAction *act = work.action;
1273 bool updated = false;
1275 if (act->is_read()) {
1276 const ModelAction *rf = act->get_reads_from();
1277 if (rf != NULL && r_modification_order(act, rf))
1280 if (act->is_write()) {
1281 if (w_modification_order(act))
1284 mo_graph->commitChanges();
1287 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1296 check_curr_backtracking(curr);
1297 set_backtracking(curr);
1301 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1303 Node *currnode = curr->get_node();
1304 Node *parnode = currnode->get_parent();
1306 if ((parnode && !parnode->backtrack_empty()) ||
1307 !currnode->misc_empty() ||
1308 !currnode->read_from_empty() ||
1309 !currnode->future_value_empty() ||
1310 !currnode->promise_empty() ||
1311 !currnode->relseq_break_empty()) {
1312 set_latest_backtrack(curr);
1316 bool ModelChecker::promises_expired() const
1318 for (unsigned int i = 0; i < promises->size(); i++) {
1319 Promise *promise = (*promises)[i];
1320 if (promise->get_expiration() < priv->used_sequence_numbers)
1327 * This is the strongest feasibility check available.
1328 * @return whether the current trace (partial or complete) must be a prefix of
1331 bool ModelChecker::isfeasibleprefix() const
1333 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1337 * Returns whether the current completed trace is feasible, except for pending
1338 * release sequences.
1340 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1342 if (DBG_ENABLED() && promises->size() != 0)
1343 DEBUG("Infeasible: unrevolved promises\n");
1345 return !is_infeasible() && promises->size() == 0;
1349 * Check if the current partial trace is infeasible. Does not check any
1350 * end-of-execution flags, which might rule out the execution. Thus, this is
1351 * useful only for ruling an execution as infeasible.
1352 * @return whether the current partial trace is infeasible.
1354 bool ModelChecker::is_infeasible() const
1356 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1357 DEBUG("Infeasible: RMW violation\n");
1359 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1363 * Check If the current partial trace is infeasible, while ignoring
1364 * infeasibility related to 2 RMW's reading from the same store. It does not
1365 * check end-of-execution feasibility.
1366 * @see ModelChecker::is_infeasible
1367 * @return whether the current partial trace is infeasible, ignoring multiple
1368 * RMWs reading from the same store.
1370 bool ModelChecker::is_infeasible_ignoreRMW() const
1372 if (DBG_ENABLED()) {
1373 if (mo_graph->checkForCycles())
1374 DEBUG("Infeasible: modification order cycles\n");
1375 if (priv->failed_promise)
1376 DEBUG("Infeasible: failed promise\n");
1377 if (priv->too_many_reads)
1378 DEBUG("Infeasible: too many reads\n");
1379 if (priv->bad_synchronization)
1380 DEBUG("Infeasible: bad synchronization ordering\n");
1381 if (promises_expired())
1382 DEBUG("Infeasible: promises expired\n");
1384 return mo_graph->checkForCycles() || priv->failed_promise ||
1385 priv->too_many_reads || priv->bad_synchronization ||
1389 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1390 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1391 ModelAction *lastread = get_last_action(act->get_tid());
1392 lastread->process_rmw(act);
1393 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1394 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1395 mo_graph->commitChanges();
1401 * Checks whether a thread has read from the same write for too many times
1402 * without seeing the effects of a later write.
1405 * 1) there must a different write that we could read from that would satisfy the modification order,
1406 * 2) we must have read from the same value in excess of maxreads times, and
1407 * 3) that other write must have been in the reads_from set for maxreads times.
1409 * If so, we decide that the execution is no longer feasible.
1411 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1413 if (params.maxreads != 0) {
1414 if (curr->get_node()->get_read_from_size() <= 1)
1416 //Must make sure that execution is currently feasible... We could
1417 //accidentally clear by rolling back
1418 if (is_infeasible())
1420 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1421 int tid = id_to_int(curr->get_tid());
1424 if ((int)thrd_lists->size() <= tid)
1426 action_list_t *list = &(*thrd_lists)[tid];
1428 action_list_t::reverse_iterator rit = list->rbegin();
1429 /* Skip past curr */
1430 for (; (*rit) != curr; rit++)
1432 /* go past curr now */
1435 action_list_t::reverse_iterator ritcopy = rit;
1436 //See if we have enough reads from the same value
1438 for (; count < params.maxreads; rit++, count++) {
1439 if (rit == list->rend())
1441 ModelAction *act = *rit;
1442 if (!act->is_read())
1445 if (act->get_reads_from() != rf)
1447 if (act->get_node()->get_read_from_size() <= 1)
1450 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1452 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1454 /* Need a different write */
1458 /* Test to see whether this is a feasible write to read from */
1459 mo_graph->startChanges();
1460 r_modification_order(curr, write);
1461 bool feasiblereadfrom = !is_infeasible();
1462 mo_graph->rollbackChanges();
1464 if (!feasiblereadfrom)
1468 bool feasiblewrite = true;
1469 //new we need to see if this write works for everyone
1471 for (int loop = count; loop > 0; loop--, rit++) {
1472 ModelAction *act = *rit;
1473 bool foundvalue = false;
1474 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1475 if (act->get_node()->get_read_from_at(j) == write) {
1481 feasiblewrite = false;
1485 if (feasiblewrite) {
1486 priv->too_many_reads = true;
1494 * Updates the mo_graph with the constraints imposed from the current
1497 * Basic idea is the following: Go through each other thread and find
1498 * the lastest action that happened before our read. Two cases:
1500 * (1) The action is a write => that write must either occur before
1501 * the write we read from or be the write we read from.
1503 * (2) The action is a read => the write that that action read from
1504 * must occur before the write we read from or be the same write.
1506 * @param curr The current action. Must be a read.
1507 * @param rf The action that curr reads from. Must be a write.
1508 * @return True if modification order edges were added; false otherwise
1510 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1512 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1515 ASSERT(curr->is_read());
1517 /* Last SC fence in the current thread */
1518 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1520 /* Iterate over all threads */
1521 for (i = 0; i < thrd_lists->size(); i++) {
1522 /* Last SC fence in thread i */
1523 ModelAction *last_sc_fence_thread_local = NULL;
1524 if (int_to_id((int)i) != curr->get_tid())
1525 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1527 /* Last SC fence in thread i, before last SC fence in current thread */
1528 ModelAction *last_sc_fence_thread_before = NULL;
1529 if (last_sc_fence_local)
1530 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1532 /* Iterate over actions in thread, starting from most recent */
1533 action_list_t *list = &(*thrd_lists)[i];
1534 action_list_t::reverse_iterator rit;
1535 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1536 ModelAction *act = *rit;
1538 if (act->is_write() && act != rf && act != curr) {
1539 /* C++, Section 29.3 statement 5 */
1540 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1541 *act < *last_sc_fence_thread_local) {
1542 mo_graph->addEdge(act, rf);
1546 /* C++, Section 29.3 statement 4 */
1547 else if (act->is_seqcst() && last_sc_fence_local &&
1548 *act < *last_sc_fence_local) {
1549 mo_graph->addEdge(act, rf);
1553 /* C++, Section 29.3 statement 6 */
1554 else if (last_sc_fence_thread_before &&
1555 *act < *last_sc_fence_thread_before) {
1556 mo_graph->addEdge(act, rf);
1563 * Include at most one act per-thread that "happens
1564 * before" curr. Don't consider reflexively.
1566 if (act->happens_before(curr) && act != curr) {
1567 if (act->is_write()) {
1569 mo_graph->addEdge(act, rf);
1573 const ModelAction *prevreadfrom = act->get_reads_from();
1574 //if the previous read is unresolved, keep going...
1575 if (prevreadfrom == NULL)
1578 if (rf != prevreadfrom) {
1579 mo_graph->addEdge(prevreadfrom, rf);
1591 /** This method fixes up the modification order when we resolve a
1592 * promises. The basic problem is that actions that occur after the
1593 * read curr could not property add items to the modification order
1596 * So for each thread, we find the earliest item that happens after
1597 * the read curr. This is the item we have to fix up with additional
1598 * constraints. If that action is write, we add a MO edge between
1599 * the Action rf and that action. If the action is a read, we add a
1600 * MO edge between the Action rf, and whatever the read accessed.
1602 * @param curr is the read ModelAction that we are fixing up MO edges for.
1603 * @param rf is the write ModelAction that curr reads from.
1606 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1608 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1610 ASSERT(curr->is_read());
1612 /* Iterate over all threads */
1613 for (i = 0; i < thrd_lists->size(); i++) {
1614 /* Iterate over actions in thread, starting from most recent */
1615 action_list_t *list = &(*thrd_lists)[i];
1616 action_list_t::reverse_iterator rit;
1617 ModelAction *lastact = NULL;
1619 /* Find last action that happens after curr that is either not curr or a rmw */
1620 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1621 ModelAction *act = *rit;
1622 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1628 /* Include at most one act per-thread that "happens before" curr */
1629 if (lastact != NULL) {
1630 if (lastact == curr) {
1631 //Case 1: The resolved read is a RMW, and we need to make sure
1632 //that the write portion of the RMW mod order after rf
1634 mo_graph->addEdge(rf, lastact);
1635 } else if (lastact->is_read()) {
1636 //Case 2: The resolved read is a normal read and the next
1637 //operation is a read, and we need to make sure the value read
1638 //is mod ordered after rf
1640 const ModelAction *postreadfrom = lastact->get_reads_from();
1641 if (postreadfrom != NULL && rf != postreadfrom)
1642 mo_graph->addEdge(rf, postreadfrom);
1644 //Case 3: The resolved read is a normal read and the next
1645 //operation is a write, and we need to make sure that the
1646 //write is mod ordered after rf
1648 mo_graph->addEdge(rf, lastact);
1656 * Updates the mo_graph with the constraints imposed from the current write.
1658 * Basic idea is the following: Go through each other thread and find
1659 * the lastest action that happened before our write. Two cases:
1661 * (1) The action is a write => that write must occur before
1664 * (2) The action is a read => the write that that action read from
1665 * must occur before the current write.
1667 * This method also handles two other issues:
1669 * (I) Sequential Consistency: Making sure that if the current write is
1670 * seq_cst, that it occurs after the previous seq_cst write.
1672 * (II) Sending the write back to non-synchronizing reads.
1674 * @param curr The current action. Must be a write.
1675 * @return True if modification order edges were added; false otherwise
1677 bool ModelChecker::w_modification_order(ModelAction *curr)
1679 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1682 ASSERT(curr->is_write());
1684 if (curr->is_seqcst()) {
1685 /* We have to at least see the last sequentially consistent write,
1686 so we are initialized. */
1687 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1688 if (last_seq_cst != NULL) {
1689 mo_graph->addEdge(last_seq_cst, curr);
1694 /* Last SC fence in the current thread */
1695 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1697 /* Iterate over all threads */
1698 for (i = 0; i < thrd_lists->size(); i++) {
1699 /* Last SC fence in thread i, before last SC fence in current thread */
1700 ModelAction *last_sc_fence_thread_before = NULL;
1701 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1702 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1704 /* Iterate over actions in thread, starting from most recent */
1705 action_list_t *list = &(*thrd_lists)[i];
1706 action_list_t::reverse_iterator rit;
1707 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1708 ModelAction *act = *rit;
1711 * 1) If RMW and it actually read from something, then we
1712 * already have all relevant edges, so just skip to next
1715 * 2) If RMW and it didn't read from anything, we should
1716 * whatever edge we can get to speed up convergence.
1718 * 3) If normal write, we need to look at earlier actions, so
1719 * continue processing list.
1721 if (curr->is_rmw()) {
1722 if (curr->get_reads_from() != NULL)
1730 /* C++, Section 29.3 statement 7 */
1731 if (last_sc_fence_thread_before && act->is_write() &&
1732 *act < *last_sc_fence_thread_before) {
1733 mo_graph->addEdge(act, curr);
1739 * Include at most one act per-thread that "happens
1742 if (act->happens_before(curr)) {
1744 * Note: if act is RMW, just add edge:
1746 * The following edge should be handled elsewhere:
1747 * readfrom(act) --mo--> act
1749 if (act->is_write())
1750 mo_graph->addEdge(act, curr);
1751 else if (act->is_read()) {
1752 //if previous read accessed a null, just keep going
1753 if (act->get_reads_from() == NULL)
1755 mo_graph->addEdge(act->get_reads_from(), curr);
1759 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1760 !act->same_thread(curr)) {
1761 /* We have an action that:
1762 (1) did not happen before us
1763 (2) is a read and we are a write
1764 (3) cannot synchronize with us
1765 (4) is in a different thread
1767 that read could potentially read from our write. Note that
1768 these checks are overly conservative at this point, we'll
1769 do more checks before actually removing the
1773 if (thin_air_constraint_may_allow(curr, act)) {
1774 if (!is_infeasible() ||
1775 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1776 futurevalues->push_back(PendingFutureValue(curr, act));
1786 /** Arbitrary reads from the future are not allowed. Section 29.3
1787 * part 9 places some constraints. This method checks one result of constraint
1788 * constraint. Others require compiler support. */
1789 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1791 if (!writer->is_rmw())
1794 if (!reader->is_rmw())
1797 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1798 if (search == reader)
1800 if (search->get_tid() == reader->get_tid() &&
1801 search->happens_before(reader))
1809 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1810 * some constraints. This method checks one the following constraint (others
1811 * require compiler support):
1813 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1815 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1817 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1819 /* Iterate over all threads */
1820 for (i = 0; i < thrd_lists->size(); i++) {
1821 const ModelAction *write_after_read = NULL;
1823 /* Iterate over actions in thread, starting from most recent */
1824 action_list_t *list = &(*thrd_lists)[i];
1825 action_list_t::reverse_iterator rit;
1826 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1827 ModelAction *act = *rit;
1829 /* Don't disallow due to act == reader */
1830 if (!reader->happens_before(act) || reader == act)
1832 else if (act->is_write())
1833 write_after_read = act;
1834 else if (act->is_read() && act->get_reads_from() != NULL)
1835 write_after_read = act->get_reads_from();
1838 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1845 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1846 * The ModelAction under consideration is expected to be taking part in
1847 * release/acquire synchronization as an object of the "reads from" relation.
1848 * Note that this can only provide release sequence support for RMW chains
1849 * which do not read from the future, as those actions cannot be traced until
1850 * their "promise" is fulfilled. Similarly, we may not even establish the
1851 * presence of a release sequence with certainty, as some modification order
1852 * constraints may be decided further in the future. Thus, this function
1853 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1854 * and a boolean representing certainty.
1856 * @param rf The action that might be part of a release sequence. Must be a
1858 * @param release_heads A pass-by-reference style return parameter. After
1859 * execution of this function, release_heads will contain the heads of all the
1860 * relevant release sequences, if any exists with certainty
1861 * @param pending A pass-by-reference style return parameter which is only used
1862 * when returning false (i.e., uncertain). Returns most information regarding
1863 * an uncertain release sequence, including any write operations that might
1864 * break the sequence.
1865 * @return true, if the ModelChecker is certain that release_heads is complete;
1868 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1869 rel_heads_list_t *release_heads,
1870 struct release_seq *pending) const
1872 /* Only check for release sequences if there are no cycles */
1873 if (mo_graph->checkForCycles())
1877 ASSERT(rf->is_write());
1879 if (rf->is_release())
1880 release_heads->push_back(rf);
1881 else if (rf->get_last_fence_release())
1882 release_heads->push_back(rf->get_last_fence_release());
1884 break; /* End of RMW chain */
1886 /** @todo Need to be smarter here... In the linux lock
1887 * example, this will run to the beginning of the program for
1889 /** @todo The way to be smarter here is to keep going until 1
1890 * thread has a release preceded by an acquire and you've seen
1893 /* acq_rel RMW is a sufficient stopping condition */
1894 if (rf->is_acquire() && rf->is_release())
1895 return true; /* complete */
1897 rf = rf->get_reads_from();
1900 /* read from future: need to settle this later */
1902 return false; /* incomplete */
1905 if (rf->is_release())
1906 return true; /* complete */
1908 /* else relaxed write
1909 * - check for fence-release in the same thread (29.8, stmt. 3)
1910 * - check modification order for contiguous subsequence
1911 * -> rf must be same thread as release */
1913 const ModelAction *fence_release = rf->get_last_fence_release();
1914 /* Synchronize with a fence-release unconditionally; we don't need to
1915 * find any more "contiguous subsequence..." for it */
1917 release_heads->push_back(fence_release);
1919 int tid = id_to_int(rf->get_tid());
1920 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1921 action_list_t *list = &(*thrd_lists)[tid];
1922 action_list_t::const_reverse_iterator rit;
1924 /* Find rf in the thread list */
1925 rit = std::find(list->rbegin(), list->rend(), rf);
1926 ASSERT(rit != list->rend());
1928 /* Find the last {write,fence}-release */
1929 for (; rit != list->rend(); rit++) {
1930 if (fence_release && *(*rit) < *fence_release)
1932 if ((*rit)->is_release())
1935 if (rit == list->rend()) {
1936 /* No write-release in this thread */
1937 return true; /* complete */
1938 } else if (fence_release && *(*rit) < *fence_release) {
1939 /* The fence-release is more recent (and so, "stronger") than
1940 * the most recent write-release */
1941 return true; /* complete */
1942 } /* else, need to establish contiguous release sequence */
1943 ModelAction *release = *rit;
1945 ASSERT(rf->same_thread(release));
1947 pending->writes.clear();
1949 bool certain = true;
1950 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1951 if (id_to_int(rf->get_tid()) == (int)i)
1953 list = &(*thrd_lists)[i];
1955 /* Can we ensure no future writes from this thread may break
1956 * the release seq? */
1957 bool future_ordered = false;
1959 ModelAction *last = get_last_action(int_to_id(i));
1960 Thread *th = get_thread(int_to_id(i));
1961 if ((last && rf->happens_before(last)) ||
1964 future_ordered = true;
1966 ASSERT(!th->is_model_thread() || future_ordered);
1968 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1969 const ModelAction *act = *rit;
1970 /* Reach synchronization -> this thread is complete */
1971 if (act->happens_before(release))
1973 if (rf->happens_before(act)) {
1974 future_ordered = true;
1978 /* Only non-RMW writes can break release sequences */
1979 if (!act->is_write() || act->is_rmw())
1982 /* Check modification order */
1983 if (mo_graph->checkReachable(rf, act)) {
1984 /* rf --mo--> act */
1985 future_ordered = true;
1988 if (mo_graph->checkReachable(act, release))
1989 /* act --mo--> release */
1991 if (mo_graph->checkReachable(release, act) &&
1992 mo_graph->checkReachable(act, rf)) {
1993 /* release --mo-> act --mo--> rf */
1994 return true; /* complete */
1996 /* act may break release sequence */
1997 pending->writes.push_back(act);
2000 if (!future_ordered)
2001 certain = false; /* This thread is uncertain */
2005 release_heads->push_back(release);
2006 pending->writes.clear();
2008 pending->release = release;
2015 * An interface for getting the release sequence head(s) with which a
2016 * given ModelAction must synchronize. This function only returns a non-empty
2017 * result when it can locate a release sequence head with certainty. Otherwise,
2018 * it may mark the internal state of the ModelChecker so that it will handle
2019 * the release sequence at a later time, causing @a acquire to update its
2020 * synchronization at some later point in execution.
2022 * @param acquire The 'acquire' action that may synchronize with a release
2024 * @param read The read action that may read from a release sequence; this may
2025 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2026 * when 'acquire' is a fence-acquire)
2027 * @param release_heads A pass-by-reference return parameter. Will be filled
2028 * with the head(s) of the release sequence(s), if they exists with certainty.
2029 * @see ModelChecker::release_seq_heads
2031 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2032 ModelAction *read, rel_heads_list_t *release_heads)
2034 const ModelAction *rf = read->get_reads_from();
2035 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2036 sequence->acquire = acquire;
2037 sequence->read = read;
2039 if (!release_seq_heads(rf, release_heads, sequence)) {
2040 /* add act to 'lazy checking' list */
2041 pending_rel_seqs->push_back(sequence);
2043 snapshot_free(sequence);
2048 * Attempt to resolve all stashed operations that might synchronize with a
2049 * release sequence for a given location. This implements the "lazy" portion of
2050 * determining whether or not a release sequence was contiguous, since not all
2051 * modification order information is present at the time an action occurs.
2053 * @param location The location/object that should be checked for release
2054 * sequence resolutions. A NULL value means to check all locations.
2055 * @param work_queue The work queue to which to add work items as they are
2057 * @return True if any updates occurred (new synchronization, new mo_graph
2060 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2062 bool updated = false;
2063 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2064 while (it != pending_rel_seqs->end()) {
2065 struct release_seq *pending = *it;
2066 ModelAction *acquire = pending->acquire;
2067 const ModelAction *read = pending->read;
2069 /* Only resolve sequences on the given location, if provided */
2070 if (location && read->get_location() != location) {
2075 const ModelAction *rf = read->get_reads_from();
2076 rel_heads_list_t release_heads;
2078 complete = release_seq_heads(rf, &release_heads, pending);
2079 for (unsigned int i = 0; i < release_heads.size(); i++) {
2080 if (!acquire->has_synchronized_with(release_heads[i])) {
2081 if (acquire->synchronize_with(release_heads[i]))
2084 set_bad_synchronization();
2089 /* Re-check all pending release sequences */
2090 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2091 /* Re-check read-acquire for mo_graph edges */
2092 if (acquire->is_read())
2093 work_queue->push_back(MOEdgeWorkEntry(acquire));
2095 /* propagate synchronization to later actions */
2096 action_list_t::reverse_iterator rit = action_trace->rbegin();
2097 for (; (*rit) != acquire; rit++) {
2098 ModelAction *propagate = *rit;
2099 if (acquire->happens_before(propagate)) {
2100 propagate->synchronize_with(acquire);
2101 /* Re-check 'propagate' for mo_graph edges */
2102 work_queue->push_back(MOEdgeWorkEntry(propagate));
2107 it = pending_rel_seqs->erase(it);
2108 snapshot_free(pending);
2114 // If we resolved promises or data races, see if we have realized a data race.
2121 * Performs various bookkeeping operations for the current ModelAction. For
2122 * instance, adds action to the per-object, per-thread action vector and to the
2123 * action trace list of all thread actions.
2125 * @param act is the ModelAction to add.
2127 void ModelChecker::add_action_to_lists(ModelAction *act)
2129 int tid = id_to_int(act->get_tid());
2130 ModelAction *uninit = NULL;
2132 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2133 if (list->empty() && act->is_atomic_var()) {
2134 uninit = new_uninitialized_action(act->get_location());
2135 uninit_id = id_to_int(uninit->get_tid());
2136 list->push_back(uninit);
2138 list->push_back(act);
2140 action_trace->push_back(act);
2142 action_trace->push_front(uninit);
2144 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2145 if (tid >= (int)vec->size())
2146 vec->resize(priv->next_thread_id);
2147 (*vec)[tid].push_back(act);
2149 (*vec)[uninit_id].push_front(uninit);
2151 if ((int)thrd_last_action->size() <= tid)
2152 thrd_last_action->resize(get_num_threads());
2153 (*thrd_last_action)[tid] = act;
2155 (*thrd_last_action)[uninit_id] = uninit;
2157 if (act->is_fence() && act->is_release()) {
2158 if ((int)thrd_last_fence_release->size() <= tid)
2159 thrd_last_fence_release->resize(get_num_threads());
2160 (*thrd_last_fence_release)[tid] = act;
2163 if (act->is_wait()) {
2164 void *mutex_loc = (void *) act->get_value();
2165 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2167 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2168 if (tid >= (int)vec->size())
2169 vec->resize(priv->next_thread_id);
2170 (*vec)[tid].push_back(act);
2175 * @brief Get the last action performed by a particular Thread
2176 * @param tid The thread ID of the Thread in question
2177 * @return The last action in the thread
2179 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2181 int threadid = id_to_int(tid);
2182 if (threadid < (int)thrd_last_action->size())
2183 return (*thrd_last_action)[id_to_int(tid)];
2189 * @brief Get the last fence release performed by a particular Thread
2190 * @param tid The thread ID of the Thread in question
2191 * @return The last fence release in the thread, if one exists; NULL otherwise
2193 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2195 int threadid = id_to_int(tid);
2196 if (threadid < (int)thrd_last_fence_release->size())
2197 return (*thrd_last_fence_release)[id_to_int(tid)];
2203 * Gets the last memory_order_seq_cst write (in the total global sequence)
2204 * performed on a particular object (i.e., memory location), not including the
2206 * @param curr The current ModelAction; also denotes the object location to
2208 * @return The last seq_cst write
2210 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2212 void *location = curr->get_location();
2213 action_list_t *list = get_safe_ptr_action(obj_map, location);
2214 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2215 action_list_t::reverse_iterator rit;
2216 for (rit = list->rbegin(); rit != list->rend(); rit++)
2217 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2223 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2224 * performed in a particular thread, prior to a particular fence.
2225 * @param tid The ID of the thread to check
2226 * @param before_fence The fence from which to begin the search; if NULL, then
2227 * search for the most recent fence in the thread.
2228 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2230 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2232 /* All fences should have NULL location */
2233 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2234 action_list_t::reverse_iterator rit = list->rbegin();
2237 for (; rit != list->rend(); rit++)
2238 if (*rit == before_fence)
2241 ASSERT(*rit == before_fence);
2245 for (; rit != list->rend(); rit++)
2246 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2252 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2253 * location). This function identifies the mutex according to the current
2254 * action, which is presumed to perform on the same mutex.
2255 * @param curr The current ModelAction; also denotes the object location to
2257 * @return The last unlock operation
2259 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2261 void *location = curr->get_location();
2262 action_list_t *list = get_safe_ptr_action(obj_map, location);
2263 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2264 action_list_t::reverse_iterator rit;
2265 for (rit = list->rbegin(); rit != list->rend(); rit++)
2266 if ((*rit)->is_unlock() || (*rit)->is_wait())
2271 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2273 ModelAction *parent = get_last_action(tid);
2275 parent = get_thread(tid)->get_creation();
2280 * Returns the clock vector for a given thread.
2281 * @param tid The thread whose clock vector we want
2282 * @return Desired clock vector
2284 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2286 return get_parent_action(tid)->get_cv();
2290 * Resolve a set of Promises with a current write. The set is provided in the
2291 * Node corresponding to @a write.
2292 * @param write The ModelAction that is fulfilling Promises
2293 * @return True if promises were resolved; false otherwise
2295 bool ModelChecker::resolve_promises(ModelAction *write)
2297 bool resolved = false;
2298 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2300 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2301 Promise *promise = (*promises)[promise_index];
2302 if (write->get_node()->get_promise(i)) {
2303 ModelAction *read = promise->get_action();
2304 if (read->is_rmw()) {
2305 mo_graph->addRMWEdge(write, read);
2307 read_from(read, write);
2308 //First fix up the modification order for actions that happened
2310 r_modification_order(read, write);
2311 //Next fix up the modification order for actions that happened
2313 post_r_modification_order(read, write);
2314 //Make sure the promise's value matches the write's value
2315 ASSERT(promise->get_value() == write->get_value());
2318 promises->erase(promises->begin() + promise_index);
2319 threads_to_check.push_back(read->get_tid());
2326 //Check whether reading these writes has made threads unable to
2329 for (unsigned int i = 0; i < threads_to_check.size(); i++)
2330 mo_check_promises(threads_to_check[i], write);
2336 * Compute the set of promises that could potentially be satisfied by this
2337 * action. Note that the set computation actually appears in the Node, not in
2339 * @param curr The ModelAction that may satisfy promises
2341 void ModelChecker::compute_promises(ModelAction *curr)
2343 for (unsigned int i = 0; i < promises->size(); i++) {
2344 Promise *promise = (*promises)[i];
2345 const ModelAction *act = promise->get_action();
2346 if (!act->happens_before(curr) &&
2348 !act->could_synchronize_with(curr) &&
2349 !act->same_thread(curr) &&
2350 act->get_location() == curr->get_location() &&
2351 promise->get_value() == curr->get_value()) {
2352 curr->get_node()->set_promise(i, act->is_rmw());
2357 /** Checks promises in response to change in ClockVector Threads. */
2358 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2360 for (unsigned int i = 0; i < promises->size(); i++) {
2361 Promise *promise = (*promises)[i];
2362 const ModelAction *act = promise->get_action();
2363 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2364 merge_cv->synchronized_since(act)) {
2365 if (promise->increment_threads(tid)) {
2366 //Promise has failed
2367 priv->failed_promise = true;
2374 void ModelChecker::check_promises_thread_disabled() {
2375 for (unsigned int i = 0; i < promises->size(); i++) {
2376 Promise *promise = (*promises)[i];
2377 if (promise->check_promise()) {
2378 priv->failed_promise = true;
2384 /** Checks promises in response to addition to modification order for threads.
2386 * pthread is the thread that performed the read that created the promise
2388 * pread is the read that created the promise
2390 * pwrite is either the first write to same location as pread by
2391 * pthread that is sequenced after pread or the value read by the
2392 * first read to the same lcoation as pread by pthread that is
2393 * sequenced after pread..
2395 * 1. If tid=pthread, then we check what other threads are reachable
2396 * through the mode order starting with pwrite. Those threads cannot
2397 * perform a write that will resolve the promise due to modification
2398 * order constraints.
2400 * 2. If the tid is not pthread, we check whether pwrite can reach the
2401 * action write through the modification order. If so, that thread
2402 * cannot perform a future write that will resolve the promise due to
2403 * modificatin order constraints.
2405 * @param tid The thread that either read from the model action
2406 * write, or actually did the model action write.
2408 * @param write The ModelAction representing the relevant write.
2410 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write)
2412 void *location = write->get_location();
2413 for (unsigned int i = 0; i < promises->size(); i++) {
2414 Promise *promise = (*promises)[i];
2415 const ModelAction *act = promise->get_action();
2417 //Is this promise on the same location?
2418 if (act->get_location() != location)
2421 //same thread as the promise
2422 if (act->get_tid() == tid) {
2424 //do we have a pwrite for the promise, if not, set it
2425 if (promise->get_write() == NULL) {
2426 promise->set_write(write);
2427 //The pwrite cannot happen before the promise
2428 if (write->happens_before(act) && (write != act)) {
2429 priv->failed_promise = true;
2433 if (mo_graph->checkPromise(write, promise)) {
2434 priv->failed_promise = true;
2439 //Don't do any lookups twice for the same thread
2440 if (promise->has_sync_thread(tid))
2443 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2444 if (promise->increment_threads(tid)) {
2445 priv->failed_promise = true;
2453 * Compute the set of writes that may break the current pending release
2454 * sequence. This information is extracted from previou release sequence
2457 * @param curr The current ModelAction. Must be a release sequence fixup
2460 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2462 if (pending_rel_seqs->empty())
2465 struct release_seq *pending = pending_rel_seqs->back();
2466 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2467 const ModelAction *write = pending->writes[i];
2468 curr->get_node()->add_relseq_break(write);
2471 /* NULL means don't break the sequence; just synchronize */
2472 curr->get_node()->add_relseq_break(NULL);
2476 * Build up an initial set of all past writes that this 'read' action may read
2477 * from. This set is determined by the clock vector's "happens before"
2479 * @param curr is the current ModelAction that we are exploring; it must be a
2482 void ModelChecker::build_reads_from_past(ModelAction *curr)
2484 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2486 ASSERT(curr->is_read());
2488 ModelAction *last_sc_write = NULL;
2490 if (curr->is_seqcst())
2491 last_sc_write = get_last_seq_cst_write(curr);
2493 /* Iterate over all threads */
2494 for (i = 0; i < thrd_lists->size(); i++) {
2495 /* Iterate over actions in thread, starting from most recent */
2496 action_list_t *list = &(*thrd_lists)[i];
2497 action_list_t::reverse_iterator rit;
2498 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2499 ModelAction *act = *rit;
2501 /* Only consider 'write' actions */
2502 if (!act->is_write() || act == curr)
2505 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2506 bool allow_read = true;
2508 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2510 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2514 curr->get_node()->add_read_from(act);
2516 /* Include at most one act per-thread that "happens before" curr */
2517 if (act->happens_before(curr))
2522 if (DBG_ENABLED()) {
2523 model_print("Reached read action:\n");
2525 model_print("Printing may_read_from\n");
2526 curr->get_node()->print_may_read_from();
2527 model_print("End printing may_read_from\n");
2531 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2534 /* UNINIT actions don't have a Node, and they never sleep */
2535 if (write->is_uninitialized())
2537 Node *prevnode = write->get_node()->get_parent();
2539 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2540 if (write->is_release() && thread_sleep)
2542 if (!write->is_rmw()) {
2545 if (write->get_reads_from() == NULL)
2547 write = write->get_reads_from();
2552 * @brief Create a new action representing an uninitialized atomic
2553 * @param location The memory location of the atomic object
2554 * @return A pointer to a new ModelAction
2556 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2558 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2559 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2560 act->create_cv(NULL);
2564 static void print_list(action_list_t *list, int exec_num = -1)
2566 action_list_t::iterator it;
2568 model_print("---------------------------------------------------------------------\n");
2570 model_print("Execution %d:\n", exec_num);
2572 unsigned int hash = 0;
2574 for (it = list->begin(); it != list->end(); it++) {
2576 hash = hash^(hash<<3)^((*it)->hash());
2578 model_print("HASH %u\n", hash);
2579 model_print("---------------------------------------------------------------------\n");
2582 #if SUPPORT_MOD_ORDER_DUMP
2583 void ModelChecker::dumpGraph(char *filename) const
2586 sprintf(buffer, "%s.dot", filename);
2587 FILE *file = fopen(buffer, "w");
2588 fprintf(file, "digraph %s {\n", filename);
2589 mo_graph->dumpNodes(file);
2590 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2592 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2593 ModelAction *action = *it;
2594 if (action->is_read()) {
2595 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2596 if (action->get_reads_from() != NULL)
2597 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2599 if (thread_array[action->get_tid()] != NULL) {
2600 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2603 thread_array[action->get_tid()] = action;
2605 fprintf(file, "}\n");
2606 model_free(thread_array);
2611 /** @brief Prints an execution trace summary. */
2612 void ModelChecker::print_summary() const
2614 #if SUPPORT_MOD_ORDER_DUMP
2616 char buffername[100];
2617 sprintf(buffername, "exec%04u", stats.num_total);
2618 mo_graph->dumpGraphToFile(buffername);
2619 sprintf(buffername, "graph%04u", stats.num_total);
2620 dumpGraph(buffername);
2623 if (!isfeasibleprefix())
2624 model_print("INFEASIBLE EXECUTION!\n");
2625 print_list(action_trace, stats.num_total);
2630 * Add a Thread to the system for the first time. Should only be called once
2632 * @param t The Thread to add
2634 void ModelChecker::add_thread(Thread *t)
2636 thread_map->put(id_to_int(t->get_id()), t);
2637 scheduler->add_thread(t);
2641 * Removes a thread from the scheduler.
2642 * @param the thread to remove.
2644 void ModelChecker::remove_thread(Thread *t)
2646 scheduler->remove_thread(t);
2650 * @brief Get a Thread reference by its ID
2651 * @param tid The Thread's ID
2652 * @return A Thread reference
2654 Thread * ModelChecker::get_thread(thread_id_t tid) const
2656 return thread_map->get(id_to_int(tid));
2660 * @brief Get a reference to the Thread in which a ModelAction was executed
2661 * @param act The ModelAction
2662 * @return A Thread reference
2664 Thread * ModelChecker::get_thread(ModelAction *act) const
2666 return get_thread(act->get_tid());
2670 * @brief Check if a Thread is currently enabled
2671 * @param t The Thread to check
2672 * @return True if the Thread is currently enabled
2674 bool ModelChecker::is_enabled(Thread *t) const
2676 return scheduler->is_enabled(t);
2680 * @brief Check if a Thread is currently enabled
2681 * @param tid The ID of the Thread to check
2682 * @return True if the Thread is currently enabled
2684 bool ModelChecker::is_enabled(thread_id_t tid) const
2686 return scheduler->is_enabled(tid);
2690 * Switch from a user-context to the "master thread" context (a.k.a. system
2691 * context). This switch is made with the intention of exploring a particular
2692 * model-checking action (described by a ModelAction object). Must be called
2693 * from a user-thread context.
2695 * @param act The current action that will be explored. May be NULL only if
2696 * trace is exiting via an assertion (see ModelChecker::set_assert and
2697 * ModelChecker::has_asserted).
2698 * @return Return the value returned by the current action
2700 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2703 Thread *old = thread_current();
2704 set_current_action(act);
2705 old->set_state(THREAD_READY);
2706 if (Thread::swap(old, &system_context) < 0) {
2707 perror("swap threads");
2710 return old->get_return_value();
2714 * Takes the next step in the execution, if possible.
2715 * @param curr The current step to take
2716 * @return Returns true (success) if a step was taken and false otherwise.
2718 bool ModelChecker::take_step(ModelAction *curr)
2723 Thread *curr_thrd = get_thread(curr);
2724 ASSERT(curr_thrd->get_state() == THREAD_READY);
2726 curr = check_current_action(curr);
2728 /* Infeasible -> don't take any more steps */
2729 if (is_infeasible())
2731 else if (isfeasibleprefix() && have_bug_reports()) {
2736 if (params.bound != 0)
2737 if (priv->used_sequence_numbers > params.bound)
2740 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2741 scheduler->remove_thread(curr_thrd);
2743 Thread *next_thrd = get_next_thread(curr);
2744 next_thrd = scheduler->next_thread(next_thrd);
2746 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2747 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2750 * Launch end-of-execution release sequence fixups only when there are:
2752 * (1) no more user threads to run (or when execution replay chooses
2753 * the 'model_thread')
2754 * (2) pending release sequences
2755 * (3) pending assertions (i.e., data races)
2756 * (4) no pending promises
2758 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2759 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2760 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2761 pending_rel_seqs->size());
2762 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2763 std::memory_order_seq_cst, NULL, VALUE_NONE,
2765 set_current_action(fixup);
2769 /* next_thrd == NULL -> don't take any more steps */
2773 next_thrd->set_state(THREAD_RUNNING);
2775 if (next_thrd->get_pending() != NULL) {
2776 /* restart a pending action */
2777 set_current_action(next_thrd->get_pending());
2778 next_thrd->set_pending(NULL);
2779 next_thrd->set_state(THREAD_READY);
2783 /* Return false only if swap fails with an error */
2784 return (Thread::swap(&system_context, next_thrd) == 0);
2787 /** Wrapper to run the user's main function, with appropriate arguments */
2788 void user_main_wrapper(void *)
2790 user_main(model->params.argc, model->params.argv);
2793 /** @brief Run ModelChecker for the user program */
2794 void ModelChecker::run()
2798 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2802 /* Run user thread up to its first action */
2803 scheduler->next_thread(t);
2804 Thread::swap(&system_context, t);
2806 /* Wait for all threads to complete */
2807 while (take_step(priv->current_action));
2808 } while (next_execution());