10 #include "nodestack.h"
13 #include "clockvector.h"
14 #include "cyclegraph.h"
17 #include "threads-model.h"
18 #include "bugmessage.h"
20 #define INITIAL_THREAD_ID 0
23 * Structure for holding small ModelChecker members that should be snapshotted
25 struct model_snapshot_members {
26 model_snapshot_members() :
27 /* First thread created will have id INITIAL_THREAD_ID */
28 next_thread_id(INITIAL_THREAD_ID),
29 used_sequence_numbers(0),
32 failed_promise(false),
33 too_many_reads(false),
34 no_valid_reads(false),
35 bad_synchronization(false),
39 ~model_snapshot_members() {
40 for (unsigned int i = 0; i < bugs.size(); i++)
45 unsigned int next_thread_id;
46 modelclock_t used_sequence_numbers;
47 ModelAction *next_backtrack;
48 SnapVector<bug_message *> bugs;
52 /** @brief Incorrectly-ordered synchronization was made */
53 bool bad_synchronization;
59 /** @brief Constructor */
60 ModelExecution::ModelExecution(ModelChecker *m,
61 struct model_params *params,
63 NodeStack *node_stack) :
68 thread_map(2), /* We'll always need at least 2 threads */
70 condvar_waiters_map(),
76 thrd_last_fence_release(),
77 node_stack(node_stack),
78 priv(new struct model_snapshot_members()),
79 mo_graph(new CycleGraph())
81 /* Initialize a model-checker thread, for special ModelActions */
82 model_thread = new Thread(get_next_id());
83 add_thread(model_thread);
84 scheduler->register_engine(this);
85 node_stack->register_engine(this);
88 /** @brief Destructor */
89 ModelExecution::~ModelExecution()
91 for (unsigned int i = 0; i < get_num_threads(); i++)
92 delete get_thread(int_to_id(i));
94 for (unsigned int i = 0; i < promises.size(); i++)
101 int ModelExecution::get_execution_number() const
103 return model->get_execution_number();
106 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
108 action_list_t *tmp = hash->get(ptr);
110 tmp = new action_list_t();
116 static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
118 SnapVector<action_list_t> *tmp = hash->get(ptr);
120 tmp = new SnapVector<action_list_t>();
126 action_list_t * ModelExecution::get_actions_on_obj(void * obj, thread_id_t tid) const
128 SnapVector<action_list_t> *wrv = obj_thrd_map.get(obj);
131 unsigned int thread=id_to_int(tid);
132 if (thread < wrv->size())
133 return &(*wrv)[thread];
138 /** @return a thread ID for a new Thread */
139 thread_id_t ModelExecution::get_next_id()
141 return priv->next_thread_id++;
144 /** @return the number of user threads created during this execution */
145 unsigned int ModelExecution::get_num_threads() const
147 return priv->next_thread_id;
150 /** @return a sequence number for a new ModelAction */
151 modelclock_t ModelExecution::get_next_seq_num()
153 return ++priv->used_sequence_numbers;
157 * @brief Should the current action wake up a given thread?
159 * @param curr The current action
160 * @param thread The thread that we might wake up
161 * @return True, if we should wake up the sleeping thread; false otherwise
163 bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
165 const ModelAction *asleep = thread->get_pending();
166 /* Don't allow partial RMW to wake anyone up */
169 /* Synchronizing actions may have been backtracked */
170 if (asleep->could_synchronize_with(curr))
172 /* All acquire/release fences and fence-acquire/store-release */
173 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
175 /* Fence-release + store can awake load-acquire on the same location */
176 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
177 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
178 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
184 void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
186 for (unsigned int i = 0; i < get_num_threads(); i++) {
187 Thread *thr = get_thread(int_to_id(i));
188 if (scheduler->is_sleep_set(thr)) {
189 if (should_wake_up(curr, thr))
190 /* Remove this thread from sleep set */
191 scheduler->remove_sleep(thr);
196 /** @brief Alert the model-checker that an incorrectly-ordered
197 * synchronization was made */
198 void ModelExecution::set_bad_synchronization()
200 priv->bad_synchronization = true;
203 bool ModelExecution::assert_bug(const char *msg)
205 priv->bugs.push_back(new bug_message(msg));
207 if (isfeasibleprefix()) {
214 /** @return True, if any bugs have been reported for this execution */
215 bool ModelExecution::have_bug_reports() const
217 return priv->bugs.size() != 0;
220 SnapVector<bug_message *> * ModelExecution::get_bugs() const
226 * Check whether the current trace has triggered an assertion which should halt
229 * @return True, if the execution should be aborted; false otherwise
231 bool ModelExecution::has_asserted() const
233 return priv->asserted;
237 * Trigger a trace assertion which should cause this execution to be halted.
238 * This can be due to a detected bug or due to an infeasibility that should
241 void ModelExecution::set_assert()
243 priv->asserted = true;
247 * Check if we are in a deadlock. Should only be called at the end of an
248 * execution, although it should not give false positives in the middle of an
249 * execution (there should be some ENABLED thread).
251 * @return True if program is in a deadlock; false otherwise
253 bool ModelExecution::is_deadlocked() const
255 bool blocking_threads = false;
256 for (unsigned int i = 0; i < get_num_threads(); i++) {
257 thread_id_t tid = int_to_id(i);
260 Thread *t = get_thread(tid);
261 if (!t->is_model_thread() && t->get_pending())
262 blocking_threads = true;
264 return blocking_threads;
268 * Check if this is a complete execution. That is, have all thread completed
269 * execution (rather than exiting because sleep sets have forced a redundant
272 * @return True if the execution is complete.
274 bool ModelExecution::is_complete_execution() const
276 for (unsigned int i = 0; i < get_num_threads(); i++)
277 if (is_enabled(int_to_id(i)))
283 * @brief Find the last fence-related backtracking conflict for a ModelAction
285 * This function performs the search for the most recent conflicting action
286 * against which we should perform backtracking, as affected by fence
287 * operations. This includes pairs of potentially-synchronizing actions which
288 * occur due to fence-acquire or fence-release, and hence should be explored in
289 * the opposite execution order.
291 * @param act The current action
292 * @return The most recent action which conflicts with act due to fences
294 ModelAction * ModelExecution::get_last_fence_conflict(ModelAction *act) const
296 /* Only perform release/acquire fence backtracking for stores */
297 if (!act->is_write())
300 /* Find a fence-release (or, act is a release) */
301 ModelAction *last_release;
302 if (act->is_release())
305 last_release = get_last_fence_release(act->get_tid());
309 /* Skip past the release */
310 const action_list_t *list = &action_trace;
311 action_list_t::const_reverse_iterator rit;
312 for (rit = list->rbegin(); rit != list->rend(); rit++)
313 if (*rit == last_release)
315 ASSERT(rit != list->rend());
320 * load --sb-> fence-acquire */
321 ModelVector<ModelAction *> acquire_fences(get_num_threads(), NULL);
322 ModelVector<ModelAction *> prior_loads(get_num_threads(), NULL);
323 bool found_acquire_fences = false;
324 for ( ; rit != list->rend(); rit++) {
325 ModelAction *prev = *rit;
326 if (act->same_thread(prev))
329 int tid = id_to_int(prev->get_tid());
331 if (prev->is_read() && act->same_var(prev)) {
332 if (prev->is_acquire()) {
333 /* Found most recent load-acquire, don't need
334 * to search for more fences */
335 if (!found_acquire_fences)
338 prior_loads[tid] = prev;
341 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
342 found_acquire_fences = true;
343 acquire_fences[tid] = prev;
347 ModelAction *latest_backtrack = NULL;
348 for (unsigned int i = 0; i < acquire_fences.size(); i++)
349 if (acquire_fences[i] && prior_loads[i])
350 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
351 latest_backtrack = acquire_fences[i];
352 return latest_backtrack;
356 * @brief Find the last backtracking conflict for a ModelAction
358 * This function performs the search for the most recent conflicting action
359 * against which we should perform backtracking. This primary includes pairs of
360 * synchronizing actions which should be explored in the opposite execution
363 * @param act The current action
364 * @return The most recent action which conflicts with act
366 ModelAction * ModelExecution::get_last_conflict(ModelAction *act) const
368 switch (act->get_type()) {
369 /* case ATOMIC_FENCE: fences don't directly cause backtracking */
373 ModelAction *ret = NULL;
375 /* linear search: from most recent to oldest */
376 action_list_t *list = obj_map.get(act->get_location());
377 action_list_t::reverse_iterator rit;
378 for (rit = list->rbegin(); rit != list->rend(); rit++) {
379 ModelAction *prev = *rit;
380 if (prev->could_synchronize_with(act)) {
386 ModelAction *ret2 = get_last_fence_conflict(act);
396 case ATOMIC_TRYLOCK: {
397 /* linear search: from most recent to oldest */
398 action_list_t *list = obj_map.get(act->get_location());
399 action_list_t::reverse_iterator rit;
400 for (rit = list->rbegin(); rit != list->rend(); rit++) {
401 ModelAction *prev = *rit;
402 if (act->is_conflicting_lock(prev))
407 case ATOMIC_UNLOCK: {
408 /* linear search: from most recent to oldest */
409 action_list_t *list = obj_map.get(act->get_location());
410 action_list_t::reverse_iterator rit;
411 for (rit = list->rbegin(); rit != list->rend(); rit++) {
412 ModelAction *prev = *rit;
413 if (!act->same_thread(prev) && prev->is_failed_trylock())
419 /* linear search: from most recent to oldest */
420 action_list_t *list = obj_map.get(act->get_location());
421 action_list_t::reverse_iterator rit;
422 for (rit = list->rbegin(); rit != list->rend(); rit++) {
423 ModelAction *prev = *rit;
424 if (!act->same_thread(prev) && prev->is_failed_trylock())
426 if (!act->same_thread(prev) && prev->is_notify())
432 case ATOMIC_NOTIFY_ALL:
433 case ATOMIC_NOTIFY_ONE: {
434 /* linear search: from most recent to oldest */
435 action_list_t *list = obj_map.get(act->get_location());
436 action_list_t::reverse_iterator rit;
437 for (rit = list->rbegin(); rit != list->rend(); rit++) {
438 ModelAction *prev = *rit;
439 if (!act->same_thread(prev) && prev->is_wait())
450 /** This method finds backtracking points where we should try to
451 * reorder the parameter ModelAction against.
453 * @param the ModelAction to find backtracking points for.
455 void ModelExecution::set_backtracking(ModelAction *act)
457 Thread *t = get_thread(act);
458 ModelAction *prev = get_last_conflict(act);
462 Node *node = prev->get_node()->get_parent();
464 /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
465 int low_tid, high_tid;
466 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
467 low_tid = id_to_int(act->get_tid());
468 high_tid = low_tid + 1;
471 high_tid = get_num_threads();
474 for (int i = low_tid; i < high_tid; i++) {
475 thread_id_t tid = int_to_id(i);
477 /* Make sure this thread can be enabled here. */
478 if (i >= node->get_num_threads())
481 /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
482 /* Don't backtrack into a point where the thread is disabled or sleeping. */
483 if (node->enabled_status(tid) != THREAD_ENABLED)
486 /* Check if this has been explored already */
487 if (node->has_been_explored(tid))
490 /* See if fairness allows */
491 if (params->fairwindow != 0 && !node->has_priority(tid)) {
493 for (int t = 0; t < node->get_num_threads(); t++) {
494 thread_id_t tother = int_to_id(t);
495 if (node->is_enabled(tother) && node->has_priority(tother)) {
504 /* See if CHESS-like yield fairness allows */
505 if (params->yieldon) {
507 for (int t = 0; t < node->get_num_threads(); t++) {
508 thread_id_t tother = int_to_id(t);
509 if (node->is_enabled(tother) && node->has_priority_over(tid, tother)) {
518 /* Cache the latest backtracking point */
519 set_latest_backtrack(prev);
521 /* If this is a new backtracking point, mark the tree */
522 if (!node->set_backtrack(tid))
524 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
525 id_to_int(prev->get_tid()),
526 id_to_int(t->get_id()));
535 * @brief Cache the a backtracking point as the "most recent", if eligible
537 * Note that this does not prepare the NodeStack for this backtracking
538 * operation, it only caches the action on a per-execution basis
540 * @param act The operation at which we should explore a different next action
541 * (i.e., backtracking point)
542 * @return True, if this action is now the most recent backtracking point;
545 bool ModelExecution::set_latest_backtrack(ModelAction *act)
547 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
548 priv->next_backtrack = act;
555 * Returns last backtracking point. The model checker will explore a different
556 * path for this point in the next execution.
557 * @return The ModelAction at which the next execution should diverge.
559 ModelAction * ModelExecution::get_next_backtrack()
561 ModelAction *next = priv->next_backtrack;
562 priv->next_backtrack = NULL;
567 * Processes a read model action.
568 * @param curr is the read model action to process.
569 * @return True if processing this read updates the mo_graph.
571 bool ModelExecution::process_read(ModelAction *curr)
573 Node *node = curr->get_node();
575 bool updated = false;
576 switch (node->get_read_from_status()) {
577 case READ_FROM_PAST: {
578 const ModelAction *rf = node->get_read_from_past();
581 mo_graph->startChanges();
583 ASSERT(!is_infeasible());
584 if (!check_recency(curr, rf)) {
585 if (node->increment_read_from()) {
586 mo_graph->rollbackChanges();
589 priv->too_many_reads = true;
593 updated = r_modification_order(curr, rf);
595 mo_graph->commitChanges();
596 mo_check_promises(curr, true);
599 case READ_FROM_PROMISE: {
600 Promise *promise = curr->get_node()->get_read_from_promise();
601 if (promise->add_reader(curr))
602 priv->failed_promise = true;
603 curr->set_read_from_promise(promise);
604 mo_graph->startChanges();
605 if (!check_recency(curr, promise))
606 priv->too_many_reads = true;
607 updated = r_modification_order(curr, promise);
608 mo_graph->commitChanges();
611 case READ_FROM_FUTURE: {
612 /* Read from future value */
613 struct future_value fv = node->get_future_value();
614 Promise *promise = new Promise(this, curr, fv);
615 curr->set_read_from_promise(promise);
616 promises.push_back(promise);
617 mo_graph->startChanges();
618 updated = r_modification_order(curr, promise);
619 mo_graph->commitChanges();
625 get_thread(curr)->set_return_value(curr->get_return_value());
631 * Processes a lock, trylock, or unlock model action. @param curr is
632 * the read model action to process.
634 * The try lock operation checks whether the lock is taken. If not,
635 * it falls to the normal lock operation case. If so, it returns
638 * The lock operation has already been checked that it is enabled, so
639 * it just grabs the lock and synchronizes with the previous unlock.
641 * The unlock operation has to re-enable all of the threads that are
642 * waiting on the lock.
644 * @return True if synchronization was updated; false otherwise
646 bool ModelExecution::process_mutex(ModelAction *curr)
648 std::mutex *mutex = curr->get_mutex();
649 struct std::mutex_state *state = NULL;
652 state = mutex->get_state();
654 switch (curr->get_type()) {
655 case ATOMIC_TRYLOCK: {
656 bool success = !state->locked;
657 curr->set_try_lock(success);
659 get_thread(curr)->set_return_value(0);
662 get_thread(curr)->set_return_value(1);
664 //otherwise fall into the lock case
666 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
667 assert_bug("Lock access before initialization");
668 state->locked = get_thread(curr);
669 ModelAction *unlock = get_last_unlock(curr);
670 //synchronize with the previous unlock statement
671 if (unlock != NULL) {
672 synchronize(unlock, curr);
678 case ATOMIC_UNLOCK: {
679 /* wake up the other threads */
680 for (unsigned int i = 0; i < get_num_threads(); i++) {
681 Thread *t = get_thread(int_to_id(i));
682 Thread *curr_thrd = get_thread(curr);
683 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
687 /* unlock the lock - after checking who was waiting on it */
688 state->locked = NULL;
690 if (!curr->is_wait())
691 break; /* The rest is only for ATOMIC_WAIT */
693 /* Should we go to sleep? (simulate spurious failures) */
694 if (curr->get_node()->get_misc() == 0) {
695 get_safe_ptr_action(&condvar_waiters_map, curr->get_location())->push_back(curr);
697 scheduler->sleep(get_thread(curr));
701 case ATOMIC_NOTIFY_ALL: {
702 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
703 //activate all the waiting threads
704 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
705 scheduler->wake(get_thread(*rit));
710 case ATOMIC_NOTIFY_ONE: {
711 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
712 int wakeupthread = curr->get_node()->get_misc();
713 action_list_t::iterator it = waiters->begin();
714 advance(it, wakeupthread);
715 scheduler->wake(get_thread(*it));
727 * @brief Check if the current pending promises allow a future value to be sent
729 * If one of the following is true:
730 * (a) there are no pending promises
731 * (b) the reader and writer do not cross any promises
732 * Then, it is safe to pass a future value back now.
734 * Otherwise, we must save the pending future value until (a) or (b) is true
736 * @param writer The operation which sends the future value. Must be a write.
737 * @param reader The operation which will observe the value. Must be a read.
738 * @return True if the future value can be sent now; false if it must wait.
740 bool ModelExecution::promises_may_allow(const ModelAction *writer,
741 const ModelAction *reader) const
743 if (promises.empty())
745 for (int i = promises.size() - 1; i >= 0; i--) {
746 ModelAction *pr = promises[i]->get_reader(0);
747 //reader is after promise...doesn't cross any promise
750 //writer is after promise, reader before...bad...
758 * @brief Add a future value to a reader
760 * This function performs a few additional checks to ensure that the future
761 * value can be feasibly observed by the reader
763 * @param writer The operation whose value is sent. Must be a write.
764 * @param reader The read operation which may read the future value. Must be a read.
766 void ModelExecution::add_future_value(const ModelAction *writer, ModelAction *reader)
768 /* Do more ambitious checks now that mo is more complete */
769 if (!mo_may_allow(writer, reader))
772 Node *node = reader->get_node();
774 /* Find an ancestor thread which exists at the time of the reader */
775 Thread *write_thread = get_thread(writer);
776 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
777 write_thread = write_thread->get_parent();
779 struct future_value fv = {
780 writer->get_write_value(),
781 writer->get_seq_number() + params->maxfuturedelay,
782 write_thread->get_id(),
784 if (node->add_future_value(fv))
785 set_latest_backtrack(reader);
789 * Process a write ModelAction
790 * @param curr The ModelAction to process
791 * @return True if the mo_graph was updated or promises were resolved
793 bool ModelExecution::process_write(ModelAction *curr)
795 /* Readers to which we may send our future value */
796 ModelVector<ModelAction *> send_fv;
798 const ModelAction *earliest_promise_reader;
799 bool updated_promises = false;
801 bool updated_mod_order = w_modification_order(curr, &send_fv);
802 Promise *promise = pop_promise_to_resolve(curr);
805 earliest_promise_reader = promise->get_reader(0);
806 updated_promises = resolve_promise(curr, promise);
808 earliest_promise_reader = NULL;
810 for (unsigned int i = 0; i < send_fv.size(); i++) {
811 ModelAction *read = send_fv[i];
813 /* Don't send future values to reads after the Promise we resolve */
814 if (!earliest_promise_reader || *read < *earliest_promise_reader) {
815 /* Check if future value can be sent immediately */
816 if (promises_may_allow(curr, read)) {
817 add_future_value(curr, read);
819 futurevalues.push_back(PendingFutureValue(curr, read));
824 /* Check the pending future values */
825 for (int i = (int)futurevalues.size() - 1; i >= 0; i--) {
826 struct PendingFutureValue pfv = futurevalues[i];
827 if (promises_may_allow(pfv.writer, pfv.reader)) {
828 add_future_value(pfv.writer, pfv.reader);
829 futurevalues.erase(futurevalues.begin() + i);
833 mo_graph->commitChanges();
834 mo_check_promises(curr, false);
836 get_thread(curr)->set_return_value(VALUE_NONE);
837 return updated_mod_order || updated_promises;
841 * Process a fence ModelAction
842 * @param curr The ModelAction to process
843 * @return True if synchronization was updated
845 bool ModelExecution::process_fence(ModelAction *curr)
848 * fence-relaxed: no-op
849 * fence-release: only log the occurence (not in this function), for
850 * use in later synchronization
851 * fence-acquire (this function): search for hypothetical release
853 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
855 bool updated = false;
856 if (curr->is_acquire()) {
857 action_list_t *list = &action_trace;
858 action_list_t::reverse_iterator rit;
859 /* Find X : is_read(X) && X --sb-> curr */
860 for (rit = list->rbegin(); rit != list->rend(); rit++) {
861 ModelAction *act = *rit;
864 if (act->get_tid() != curr->get_tid())
866 /* Stop at the beginning of the thread */
867 if (act->is_thread_start())
869 /* Stop once we reach a prior fence-acquire */
870 if (act->is_fence() && act->is_acquire())
874 /* read-acquire will find its own release sequences */
875 if (act->is_acquire())
878 /* Establish hypothetical release sequences */
879 rel_heads_list_t release_heads;
880 get_release_seq_heads(curr, act, &release_heads);
881 for (unsigned int i = 0; i < release_heads.size(); i++)
882 synchronize(release_heads[i], curr);
883 if (release_heads.size() != 0)
891 * @brief Process the current action for thread-related activity
893 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
894 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
895 * synchronization, etc. This function is a no-op for non-THREAD actions
896 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
898 * @param curr The current action
899 * @return True if synchronization was updated or a thread completed
901 bool ModelExecution::process_thread_action(ModelAction *curr)
903 bool updated = false;
905 switch (curr->get_type()) {
906 case THREAD_CREATE: {
907 thrd_t *thrd = (thrd_t *)curr->get_location();
908 struct thread_params *params = (struct thread_params *)curr->get_value();
909 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
911 th->set_creation(curr);
912 /* Promises can be satisfied by children */
913 for (unsigned int i = 0; i < promises.size(); i++) {
914 Promise *promise = promises[i];
915 if (promise->thread_is_available(curr->get_tid()))
916 promise->add_thread(th->get_id());
921 Thread *blocking = curr->get_thread_operand();
922 ModelAction *act = get_last_action(blocking->get_id());
923 synchronize(act, curr);
924 updated = true; /* trigger rel-seq checks */
927 case THREAD_FINISH: {
928 Thread *th = get_thread(curr);
929 /* Wake up any joining threads */
930 for (unsigned int i = 0; i < get_num_threads(); i++) {
931 Thread *waiting = get_thread(int_to_id(i));
932 if (waiting->waiting_on() == th &&
933 waiting->get_pending()->is_thread_join())
934 scheduler->wake(waiting);
937 /* Completed thread can't satisfy promises */
938 for (unsigned int i = 0; i < promises.size(); i++) {
939 Promise *promise = promises[i];
940 if (promise->thread_is_available(th->get_id()))
941 if (promise->eliminate_thread(th->get_id()))
942 priv->failed_promise = true;
944 updated = true; /* trigger rel-seq checks */
948 check_promises(curr->get_tid(), NULL, curr->get_cv());
959 * @brief Process the current action for release sequence fixup activity
961 * Performs model-checker release sequence fixups for the current action,
962 * forcing a single pending release sequence to break (with a given, potential
963 * "loose" write) or to complete (i.e., synchronize). If a pending release
964 * sequence forms a complete release sequence, then we must perform the fixup
965 * synchronization, mo_graph additions, etc.
967 * @param curr The current action; must be a release sequence fixup action
968 * @param work_queue The work queue to which to add work items as they are
971 void ModelExecution::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
973 const ModelAction *write = curr->get_node()->get_relseq_break();
974 struct release_seq *sequence = pending_rel_seqs.back();
975 pending_rel_seqs.pop_back();
977 ModelAction *acquire = sequence->acquire;
978 const ModelAction *rf = sequence->rf;
979 const ModelAction *release = sequence->release;
983 ASSERT(release->same_thread(rf));
987 * @todo Forcing a synchronization requires that we set
988 * modification order constraints. For instance, we can't allow
989 * a fixup sequence in which two separate read-acquire
990 * operations read from the same sequence, where the first one
991 * synchronizes and the other doesn't. Essentially, we can't
992 * allow any writes to insert themselves between 'release' and
996 /* Must synchronize */
997 if (!synchronize(release, acquire))
999 /* Re-check all pending release sequences */
1000 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1001 /* Re-check act for mo_graph edges */
1002 work_queue->push_back(MOEdgeWorkEntry(acquire));
1004 /* propagate synchronization to later actions */
1005 action_list_t::reverse_iterator rit = action_trace.rbegin();
1006 for (; (*rit) != acquire; rit++) {
1007 ModelAction *propagate = *rit;
1008 if (acquire->happens_before(propagate)) {
1009 synchronize(acquire, propagate);
1010 /* Re-check 'propagate' for mo_graph edges */
1011 work_queue->push_back(MOEdgeWorkEntry(propagate));
1015 /* Break release sequence with new edges:
1016 * release --mo--> write --mo--> rf */
1017 mo_graph->addEdge(release, write);
1018 mo_graph->addEdge(write, rf);
1021 /* See if we have realized a data race */
1026 * Initialize the current action by performing one or more of the following
1027 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1028 * in the NodeStack, manipulating backtracking sets, allocating and
1029 * initializing clock vectors, and computing the promises to fulfill.
1031 * @param curr The current action, as passed from the user context; may be
1032 * freed/invalidated after the execution of this function, with a different
1033 * action "returned" its place (pass-by-reference)
1034 * @return True if curr is a newly-explored action; false otherwise
1036 bool ModelExecution::initialize_curr_action(ModelAction **curr)
1038 ModelAction *newcurr;
1040 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1041 newcurr = process_rmw(*curr);
1044 if (newcurr->is_rmw())
1045 compute_promises(newcurr);
1051 (*curr)->set_seq_number(get_next_seq_num());
1053 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1055 /* First restore type and order in case of RMW operation */
1056 if ((*curr)->is_rmwr())
1057 newcurr->copy_typeandorder(*curr);
1059 ASSERT((*curr)->get_location() == newcurr->get_location());
1060 newcurr->copy_from_new(*curr);
1062 /* Discard duplicate ModelAction; use action from NodeStack */
1065 /* Always compute new clock vector */
1066 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1069 return false; /* Action was explored previously */
1073 /* Always compute new clock vector */
1074 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1076 /* Assign most recent release fence */
1077 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1080 * Perform one-time actions when pushing new ModelAction onto
1083 if (newcurr->is_write())
1084 compute_promises(newcurr);
1085 else if (newcurr->is_relseq_fixup())
1086 compute_relseq_breakwrites(newcurr);
1087 else if (newcurr->is_wait())
1088 newcurr->get_node()->set_misc_max(2);
1089 else if (newcurr->is_notify_one()) {
1090 newcurr->get_node()->set_misc_max(get_safe_ptr_action(&condvar_waiters_map, newcurr->get_location())->size());
1092 return true; /* This was a new ModelAction */
1097 * @brief Establish reads-from relation between two actions
1099 * Perform basic operations involved with establishing a concrete rf relation,
1100 * including setting the ModelAction data and checking for release sequences.
1102 * @param act The action that is reading (must be a read)
1103 * @param rf The action from which we are reading (must be a write)
1105 * @return True if this read established synchronization
1107 bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
1110 ASSERT(rf->is_write());
1112 act->set_read_from(rf);
1113 if (act->is_acquire()) {
1114 rel_heads_list_t release_heads;
1115 get_release_seq_heads(act, act, &release_heads);
1116 int num_heads = release_heads.size();
1117 for (unsigned int i = 0; i < release_heads.size(); i++)
1118 if (!synchronize(release_heads[i], act))
1120 return num_heads > 0;
1126 * @brief Synchronizes two actions
1128 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
1129 * This function performs the synchronization as well as providing other hooks
1130 * for other checks along with synchronization.
1132 * @param first The left-hand side of the synchronizes-with relation
1133 * @param second The right-hand side of the synchronizes-with relation
1134 * @return True if the synchronization was successful (i.e., was consistent
1135 * with the execution order); false otherwise
1137 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
1139 if (*second < *first) {
1140 set_bad_synchronization();
1143 check_promises(first->get_tid(), second->get_cv(), first->get_cv());
1144 return second->synchronize_with(first);
1148 * Check promises and eliminate potentially-satisfying threads when a thread is
1149 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1150 * no longer satisfy a promise generated from that thread.
1152 * @param blocker The thread on which a thread is waiting
1153 * @param waiting The waiting thread
1155 void ModelExecution::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1157 for (unsigned int i = 0; i < promises.size(); i++) {
1158 Promise *promise = promises[i];
1159 if (!promise->thread_is_available(waiting->get_id()))
1161 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1162 ModelAction *reader = promise->get_reader(j);
1163 if (reader->get_tid() != blocker->get_id())
1165 if (promise->eliminate_thread(waiting->get_id())) {
1166 /* Promise has failed */
1167 priv->failed_promise = true;
1169 /* Only eliminate the 'waiting' thread once */
1177 * @brief Check whether a model action is enabled.
1179 * Checks whether a lock or join operation would be successful (i.e., is the
1180 * lock already locked, or is the joined thread already complete). If not, put
1181 * the action in a waiter list.
1183 * @param curr is the ModelAction to check whether it is enabled.
1184 * @return a bool that indicates whether the action is enabled.
1186 bool ModelExecution::check_action_enabled(ModelAction *curr) {
1187 if (curr->is_lock()) {
1188 std::mutex *lock = curr->get_mutex();
1189 struct std::mutex_state *state = lock->get_state();
1192 } else if (curr->is_thread_join()) {
1193 Thread *blocking = curr->get_thread_operand();
1194 if (!blocking->is_complete()) {
1195 thread_blocking_check_promises(blocking, get_thread(curr));
1204 * This is the heart of the model checker routine. It performs model-checking
1205 * actions corresponding to a given "current action." Among other processes, it
1206 * calculates reads-from relationships, updates synchronization clock vectors,
1207 * forms a memory_order constraints graph, and handles replay/backtrack
1208 * execution when running permutations of previously-observed executions.
1210 * @param curr The current action to process
1211 * @return The ModelAction that is actually executed; may be different than
1212 * curr; may be NULL, if the current action is not enabled to run
1214 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
1217 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1218 bool newly_explored = initialize_curr_action(&curr);
1222 wake_up_sleeping_actions(curr);
1224 /* Compute fairness information for CHESS yield algorithm */
1225 if (params->yieldon) {
1226 curr->get_node()->update_yield(scheduler);
1229 /* Add the action to lists before any other model-checking tasks */
1230 if (!second_part_of_rmw)
1231 add_action_to_lists(curr);
1233 /* Build may_read_from set for newly-created actions */
1234 if (newly_explored && curr->is_read())
1235 build_may_read_from(curr);
1237 /* Initialize work_queue with the "current action" work */
1238 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1239 while (!work_queue.empty() && !has_asserted()) {
1240 WorkQueueEntry work = work_queue.front();
1241 work_queue.pop_front();
1243 switch (work.type) {
1244 case WORK_CHECK_CURR_ACTION: {
1245 ModelAction *act = work.action;
1246 bool update = false; /* update this location's release seq's */
1247 bool update_all = false; /* update all release seq's */
1249 if (process_thread_action(curr))
1252 if (act->is_read() && !second_part_of_rmw && process_read(act))
1255 if (act->is_write() && process_write(act))
1258 if (act->is_fence() && process_fence(act))
1261 if (act->is_mutex_op() && process_mutex(act))
1264 if (act->is_relseq_fixup())
1265 process_relseq_fixup(curr, &work_queue);
1268 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1270 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1273 case WORK_CHECK_RELEASE_SEQ:
1274 resolve_release_sequences(work.location, &work_queue);
1276 case WORK_CHECK_MO_EDGES: {
1277 /** @todo Complete verification of work_queue */
1278 ModelAction *act = work.action;
1279 bool updated = false;
1281 if (act->is_read()) {
1282 const ModelAction *rf = act->get_reads_from();
1283 const Promise *promise = act->get_reads_from_promise();
1285 if (r_modification_order(act, rf))
1287 } else if (promise) {
1288 if (r_modification_order(act, promise))
1292 if (act->is_write()) {
1293 if (w_modification_order(act, NULL))
1296 mo_graph->commitChanges();
1299 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1308 check_curr_backtracking(curr);
1309 set_backtracking(curr);
1313 void ModelExecution::check_curr_backtracking(ModelAction *curr)
1315 Node *currnode = curr->get_node();
1316 Node *parnode = currnode->get_parent();
1318 if ((parnode && !parnode->backtrack_empty()) ||
1319 !currnode->misc_empty() ||
1320 !currnode->read_from_empty() ||
1321 !currnode->promise_empty() ||
1322 !currnode->relseq_break_empty()) {
1323 set_latest_backtrack(curr);
1327 bool ModelExecution::promises_expired() const
1329 for (unsigned int i = 0; i < promises.size(); i++) {
1330 Promise *promise = promises[i];
1331 if (promise->get_expiration() < priv->used_sequence_numbers)
1338 * This is the strongest feasibility check available.
1339 * @return whether the current trace (partial or complete) must be a prefix of
1342 bool ModelExecution::isfeasibleprefix() const
1344 return pending_rel_seqs.size() == 0 && is_feasible_prefix_ignore_relseq();
1348 * Print disagnostic information about an infeasible execution
1349 * @param prefix A string to prefix the output with; if NULL, then a default
1350 * message prefix will be provided
1352 void ModelExecution::print_infeasibility(const char *prefix) const
1356 if (mo_graph->checkForCycles())
1357 ptr += sprintf(ptr, "[mo cycle]");
1358 if (priv->failed_promise)
1359 ptr += sprintf(ptr, "[failed promise]");
1360 if (priv->too_many_reads)
1361 ptr += sprintf(ptr, "[too many reads]");
1362 if (priv->no_valid_reads)
1363 ptr += sprintf(ptr, "[no valid reads-from]");
1364 if (priv->bad_synchronization)
1365 ptr += sprintf(ptr, "[bad sw ordering]");
1366 if (promises_expired())
1367 ptr += sprintf(ptr, "[promise expired]");
1368 if (promises.size() != 0)
1369 ptr += sprintf(ptr, "[unresolved promise]");
1371 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1375 * Returns whether the current completed trace is feasible, except for pending
1376 * release sequences.
1378 bool ModelExecution::is_feasible_prefix_ignore_relseq() const
1380 return !is_infeasible() && promises.size() == 0;
1384 * Check if the current partial trace is infeasible. Does not check any
1385 * end-of-execution flags, which might rule out the execution. Thus, this is
1386 * useful only for ruling an execution as infeasible.
1387 * @return whether the current partial trace is infeasible.
1389 bool ModelExecution::is_infeasible() const
1391 return mo_graph->checkForCycles() ||
1392 priv->no_valid_reads ||
1393 priv->failed_promise ||
1394 priv->too_many_reads ||
1395 priv->bad_synchronization ||
1399 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1400 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
1401 ModelAction *lastread = get_last_action(act->get_tid());
1402 lastread->process_rmw(act);
1403 if (act->is_rmw()) {
1404 if (lastread->get_reads_from())
1405 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1407 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1408 mo_graph->commitChanges();
1414 * A helper function for ModelExecution::check_recency, to check if the current
1415 * thread is able to read from a different write/promise for 'params.maxreads'
1416 * number of steps and if that write/promise should become visible (i.e., is
1417 * ordered later in the modification order). This helps model memory liveness.
1419 * @param curr The current action. Must be a read.
1420 * @param rf The write/promise from which we plan to read
1421 * @param other_rf The write/promise from which we may read
1422 * @return True if we were able to read from other_rf for params.maxreads steps
1424 template <typename T, typename U>
1425 bool ModelExecution::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
1427 /* Need a different write/promise */
1428 if (other_rf->equals(rf))
1431 /* Only look for "newer" writes/promises */
1432 if (!mo_graph->checkReachable(rf, other_rf))
1435 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1436 action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
1437 action_list_t::reverse_iterator rit = list->rbegin();
1438 ASSERT((*rit) == curr);
1439 /* Skip past curr */
1442 /* Does this write/promise work for everyone? */
1443 for (int i = 0; i < params->maxreads; i++, rit++) {
1444 ModelAction *act = *rit;
1445 if (!act->may_read_from(other_rf))
1452 * Checks whether a thread has read from the same write or Promise for too many
1453 * times without seeing the effects of a later write/Promise.
1456 * 1) there must a different write/promise that we could read from,
1457 * 2) we must have read from the same write/promise in excess of maxreads times,
1458 * 3) that other write/promise must have been in the reads_from set for maxreads times, and
1459 * 4) that other write/promise must be mod-ordered after the write/promise we are reading.
1461 * If so, we decide that the execution is no longer feasible.
1463 * @param curr The current action. Must be a read.
1464 * @param rf The ModelAction/Promise from which we might read.
1465 * @return True if the read should succeed; false otherwise
1467 template <typename T>
1468 bool ModelExecution::check_recency(ModelAction *curr, const T *rf) const
1470 if (!params->maxreads)
1473 //NOTE: Next check is just optimization, not really necessary....
1474 if (curr->get_node()->get_read_from_past_size() +
1475 curr->get_node()->get_read_from_promise_size() <= 1)
1478 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1479 int tid = id_to_int(curr->get_tid());
1480 ASSERT(tid < (int)thrd_lists->size());
1481 action_list_t *list = &(*thrd_lists)[tid];
1482 action_list_t::reverse_iterator rit = list->rbegin();
1483 ASSERT((*rit) == curr);
1484 /* Skip past curr */
1487 action_list_t::reverse_iterator ritcopy = rit;
1488 /* See if we have enough reads from the same value */
1489 for (int count = 0; count < params->maxreads; ritcopy++, count++) {
1490 if (ritcopy == list->rend())
1492 ModelAction *act = *ritcopy;
1493 if (!act->is_read())
1495 if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
1497 if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
1499 if (act->get_node()->get_read_from_past_size() +
1500 act->get_node()->get_read_from_promise_size() <= 1)
1503 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1504 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1505 if (should_read_instead(curr, rf, write))
1506 return false; /* liveness failure */
1508 for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
1509 const Promise *promise = curr->get_node()->get_read_from_promise(i);
1510 if (should_read_instead(curr, rf, promise))
1511 return false; /* liveness failure */
1517 * @brief Updates the mo_graph with the constraints imposed from the current
1520 * Basic idea is the following: Go through each other thread and find
1521 * the last action that happened before our read. Two cases:
1523 * -# The action is a write: that write must either occur before
1524 * the write we read from or be the write we read from.
1525 * -# The action is a read: the write that that action read from
1526 * must occur before the write we read from or be the same write.
1528 * @param curr The current action. Must be a read.
1529 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1530 * @return True if modification order edges were added; false otherwise
1532 template <typename rf_type>
1533 bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
1535 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1538 ASSERT(curr->is_read());
1540 /* Last SC fence in the current thread */
1541 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1542 ModelAction *last_sc_write = NULL;
1543 if (curr->is_seqcst())
1544 last_sc_write = get_last_seq_cst_write(curr);
1546 /* Iterate over all threads */
1547 for (i = 0; i < thrd_lists->size(); i++) {
1548 /* Last SC fence in thread i */
1549 ModelAction *last_sc_fence_thread_local = NULL;
1550 if (int_to_id((int)i) != curr->get_tid())
1551 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1553 /* Last SC fence in thread i, before last SC fence in current thread */
1554 ModelAction *last_sc_fence_thread_before = NULL;
1555 if (last_sc_fence_local)
1556 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1558 /* Iterate over actions in thread, starting from most recent */
1559 action_list_t *list = &(*thrd_lists)[i];
1560 action_list_t::reverse_iterator rit;
1561 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1562 ModelAction *act = *rit;
1567 /* Don't want to add reflexive edges on 'rf' */
1568 if (act->equals(rf)) {
1569 if (act->happens_before(curr))
1575 if (act->is_write()) {
1576 /* C++, Section 29.3 statement 5 */
1577 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1578 *act < *last_sc_fence_thread_local) {
1579 added = mo_graph->addEdge(act, rf) || added;
1582 /* C++, Section 29.3 statement 4 */
1583 else if (act->is_seqcst() && last_sc_fence_local &&
1584 *act < *last_sc_fence_local) {
1585 added = mo_graph->addEdge(act, rf) || added;
1588 /* C++, Section 29.3 statement 6 */
1589 else if (last_sc_fence_thread_before &&
1590 *act < *last_sc_fence_thread_before) {
1591 added = mo_graph->addEdge(act, rf) || added;
1596 /* C++, Section 29.3 statement 3 (second subpoint) */
1597 if (curr->is_seqcst() && last_sc_write && act == last_sc_write) {
1598 added = mo_graph->addEdge(act, rf) || added;
1603 * Include at most one act per-thread that "happens
1606 if (act->happens_before(curr)) {
1607 if (act->is_write()) {
1608 added = mo_graph->addEdge(act, rf) || added;
1610 const ModelAction *prevrf = act->get_reads_from();
1611 const Promise *prevrf_promise = act->get_reads_from_promise();
1613 if (!prevrf->equals(rf))
1614 added = mo_graph->addEdge(prevrf, rf) || added;
1615 } else if (!prevrf_promise->equals(rf)) {
1616 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1625 * All compatible, thread-exclusive promises must be ordered after any
1626 * concrete loads from the same thread
1628 for (unsigned int i = 0; i < promises.size(); i++)
1629 if (promises[i]->is_compatible_exclusive(curr))
1630 added = mo_graph->addEdge(rf, promises[i]) || added;
1636 * Updates the mo_graph with the constraints imposed from the current write.
1638 * Basic idea is the following: Go through each other thread and find
1639 * the lastest action that happened before our write. Two cases:
1641 * (1) The action is a write => that write must occur before
1644 * (2) The action is a read => the write that that action read from
1645 * must occur before the current write.
1647 * This method also handles two other issues:
1649 * (I) Sequential Consistency: Making sure that if the current write is
1650 * seq_cst, that it occurs after the previous seq_cst write.
1652 * (II) Sending the write back to non-synchronizing reads.
1654 * @param curr The current action. Must be a write.
1655 * @param send_fv A vector for stashing reads to which we may pass our future
1656 * value. If NULL, then don't record any future values.
1657 * @return True if modification order edges were added; false otherwise
1659 bool ModelExecution::w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv)
1661 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1664 ASSERT(curr->is_write());
1666 if (curr->is_seqcst()) {
1667 /* We have to at least see the last sequentially consistent write,
1668 so we are initialized. */
1669 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1670 if (last_seq_cst != NULL) {
1671 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1675 /* Last SC fence in the current thread */
1676 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1678 /* Iterate over all threads */
1679 for (i = 0; i < thrd_lists->size(); i++) {
1680 /* Last SC fence in thread i, before last SC fence in current thread */
1681 ModelAction *last_sc_fence_thread_before = NULL;
1682 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1683 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1685 /* Iterate over actions in thread, starting from most recent */
1686 action_list_t *list = &(*thrd_lists)[i];
1687 action_list_t::reverse_iterator rit;
1688 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1689 ModelAction *act = *rit;
1692 * 1) If RMW and it actually read from something, then we
1693 * already have all relevant edges, so just skip to next
1696 * 2) If RMW and it didn't read from anything, we should
1697 * whatever edge we can get to speed up convergence.
1699 * 3) If normal write, we need to look at earlier actions, so
1700 * continue processing list.
1702 if (curr->is_rmw()) {
1703 if (curr->get_reads_from() != NULL)
1711 /* C++, Section 29.3 statement 7 */
1712 if (last_sc_fence_thread_before && act->is_write() &&
1713 *act < *last_sc_fence_thread_before) {
1714 added = mo_graph->addEdge(act, curr) || added;
1719 * Include at most one act per-thread that "happens
1722 if (act->happens_before(curr)) {
1724 * Note: if act is RMW, just add edge:
1726 * The following edge should be handled elsewhere:
1727 * readfrom(act) --mo--> act
1729 if (act->is_write())
1730 added = mo_graph->addEdge(act, curr) || added;
1731 else if (act->is_read()) {
1732 //if previous read accessed a null, just keep going
1733 if (act->get_reads_from() == NULL)
1735 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1738 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1739 !act->same_thread(curr)) {
1740 /* We have an action that:
1741 (1) did not happen before us
1742 (2) is a read and we are a write
1743 (3) cannot synchronize with us
1744 (4) is in a different thread
1746 that read could potentially read from our write. Note that
1747 these checks are overly conservative at this point, we'll
1748 do more checks before actually removing the
1752 if (send_fv && thin_air_constraint_may_allow(curr, act)) {
1753 if (!is_infeasible())
1754 send_fv->push_back(act);
1755 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1756 add_future_value(curr, act);
1763 * All compatible, thread-exclusive promises must be ordered after any
1764 * concrete stores to the same thread, or else they can be merged with
1767 for (unsigned int i = 0; i < promises.size(); i++)
1768 if (promises[i]->is_compatible_exclusive(curr))
1769 added = mo_graph->addEdge(curr, promises[i]) || added;
1774 /** Arbitrary reads from the future are not allowed. Section 29.3
1775 * part 9 places some constraints. This method checks one result of constraint
1776 * constraint. Others require compiler support. */
1777 bool ModelExecution::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader) const
1779 if (!writer->is_rmw())
1782 if (!reader->is_rmw())
1785 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1786 if (search == reader)
1788 if (search->get_tid() == reader->get_tid() &&
1789 search->happens_before(reader))
1797 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1798 * some constraints. This method checks one the following constraint (others
1799 * require compiler support):
1801 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1803 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1805 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1807 /* Iterate over all threads */
1808 for (i = 0; i < thrd_lists->size(); i++) {
1809 const ModelAction *write_after_read = NULL;
1811 /* Iterate over actions in thread, starting from most recent */
1812 action_list_t *list = &(*thrd_lists)[i];
1813 action_list_t::reverse_iterator rit;
1814 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1815 ModelAction *act = *rit;
1817 /* Don't disallow due to act == reader */
1818 if (!reader->happens_before(act) || reader == act)
1820 else if (act->is_write())
1821 write_after_read = act;
1822 else if (act->is_read() && act->get_reads_from() != NULL)
1823 write_after_read = act->get_reads_from();
1826 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1833 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1834 * The ModelAction under consideration is expected to be taking part in
1835 * release/acquire synchronization as an object of the "reads from" relation.
1836 * Note that this can only provide release sequence support for RMW chains
1837 * which do not read from the future, as those actions cannot be traced until
1838 * their "promise" is fulfilled. Similarly, we may not even establish the
1839 * presence of a release sequence with certainty, as some modification order
1840 * constraints may be decided further in the future. Thus, this function
1841 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1842 * and a boolean representing certainty.
1844 * @param rf The action that might be part of a release sequence. Must be a
1846 * @param release_heads A pass-by-reference style return parameter. After
1847 * execution of this function, release_heads will contain the heads of all the
1848 * relevant release sequences, if any exists with certainty
1849 * @param pending A pass-by-reference style return parameter which is only used
1850 * when returning false (i.e., uncertain). Returns most information regarding
1851 * an uncertain release sequence, including any write operations that might
1852 * break the sequence.
1853 * @return true, if the ModelExecution is certain that release_heads is complete;
1856 bool ModelExecution::release_seq_heads(const ModelAction *rf,
1857 rel_heads_list_t *release_heads,
1858 struct release_seq *pending) const
1860 /* Only check for release sequences if there are no cycles */
1861 if (mo_graph->checkForCycles())
1864 for ( ; rf != NULL; rf = rf->get_reads_from()) {
1865 ASSERT(rf->is_write());
1867 if (rf->is_release())
1868 release_heads->push_back(rf);
1869 else if (rf->get_last_fence_release())
1870 release_heads->push_back(rf->get_last_fence_release());
1872 break; /* End of RMW chain */
1874 /** @todo Need to be smarter here... In the linux lock
1875 * example, this will run to the beginning of the program for
1877 /** @todo The way to be smarter here is to keep going until 1
1878 * thread has a release preceded by an acquire and you've seen
1881 /* acq_rel RMW is a sufficient stopping condition */
1882 if (rf->is_acquire() && rf->is_release())
1883 return true; /* complete */
1886 /* read from future: need to settle this later */
1888 return false; /* incomplete */
1891 if (rf->is_release())
1892 return true; /* complete */
1894 /* else relaxed write
1895 * - check for fence-release in the same thread (29.8, stmt. 3)
1896 * - check modification order for contiguous subsequence
1897 * -> rf must be same thread as release */
1899 const ModelAction *fence_release = rf->get_last_fence_release();
1900 /* Synchronize with a fence-release unconditionally; we don't need to
1901 * find any more "contiguous subsequence..." for it */
1903 release_heads->push_back(fence_release);
1905 int tid = id_to_int(rf->get_tid());
1906 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(rf->get_location());
1907 action_list_t *list = &(*thrd_lists)[tid];
1908 action_list_t::const_reverse_iterator rit;
1910 /* Find rf in the thread list */
1911 rit = std::find(list->rbegin(), list->rend(), rf);
1912 ASSERT(rit != list->rend());
1914 /* Find the last {write,fence}-release */
1915 for (; rit != list->rend(); rit++) {
1916 if (fence_release && *(*rit) < *fence_release)
1918 if ((*rit)->is_release())
1921 if (rit == list->rend()) {
1922 /* No write-release in this thread */
1923 return true; /* complete */
1924 } else if (fence_release && *(*rit) < *fence_release) {
1925 /* The fence-release is more recent (and so, "stronger") than
1926 * the most recent write-release */
1927 return true; /* complete */
1928 } /* else, need to establish contiguous release sequence */
1929 ModelAction *release = *rit;
1931 ASSERT(rf->same_thread(release));
1933 pending->writes.clear();
1935 bool certain = true;
1936 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1937 if (id_to_int(rf->get_tid()) == (int)i)
1939 list = &(*thrd_lists)[i];
1941 /* Can we ensure no future writes from this thread may break
1942 * the release seq? */
1943 bool future_ordered = false;
1945 ModelAction *last = get_last_action(int_to_id(i));
1946 Thread *th = get_thread(int_to_id(i));
1947 if ((last && rf->happens_before(last)) ||
1950 future_ordered = true;
1952 ASSERT(!th->is_model_thread() || future_ordered);
1954 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1955 const ModelAction *act = *rit;
1956 /* Reach synchronization -> this thread is complete */
1957 if (act->happens_before(release))
1959 if (rf->happens_before(act)) {
1960 future_ordered = true;
1964 /* Only non-RMW writes can break release sequences */
1965 if (!act->is_write() || act->is_rmw())
1968 /* Check modification order */
1969 if (mo_graph->checkReachable(rf, act)) {
1970 /* rf --mo--> act */
1971 future_ordered = true;
1974 if (mo_graph->checkReachable(act, release))
1975 /* act --mo--> release */
1977 if (mo_graph->checkReachable(release, act) &&
1978 mo_graph->checkReachable(act, rf)) {
1979 /* release --mo-> act --mo--> rf */
1980 return true; /* complete */
1982 /* act may break release sequence */
1983 pending->writes.push_back(act);
1986 if (!future_ordered)
1987 certain = false; /* This thread is uncertain */
1991 release_heads->push_back(release);
1992 pending->writes.clear();
1994 pending->release = release;
2001 * An interface for getting the release sequence head(s) with which a
2002 * given ModelAction must synchronize. This function only returns a non-empty
2003 * result when it can locate a release sequence head with certainty. Otherwise,
2004 * it may mark the internal state of the ModelExecution so that it will handle
2005 * the release sequence at a later time, causing @a acquire to update its
2006 * synchronization at some later point in execution.
2008 * @param acquire The 'acquire' action that may synchronize with a release
2010 * @param read The read action that may read from a release sequence; this may
2011 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2012 * when 'acquire' is a fence-acquire)
2013 * @param release_heads A pass-by-reference return parameter. Will be filled
2014 * with the head(s) of the release sequence(s), if they exists with certainty.
2015 * @see ModelExecution::release_seq_heads
2017 void ModelExecution::get_release_seq_heads(ModelAction *acquire,
2018 ModelAction *read, rel_heads_list_t *release_heads)
2020 const ModelAction *rf = read->get_reads_from();
2021 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2022 sequence->acquire = acquire;
2023 sequence->read = read;
2025 if (!release_seq_heads(rf, release_heads, sequence)) {
2026 /* add act to 'lazy checking' list */
2027 pending_rel_seqs.push_back(sequence);
2029 snapshot_free(sequence);
2034 * Attempt to resolve all stashed operations that might synchronize with a
2035 * release sequence for a given location. This implements the "lazy" portion of
2036 * determining whether or not a release sequence was contiguous, since not all
2037 * modification order information is present at the time an action occurs.
2039 * @param location The location/object that should be checked for release
2040 * sequence resolutions. A NULL value means to check all locations.
2041 * @param work_queue The work queue to which to add work items as they are
2043 * @return True if any updates occurred (new synchronization, new mo_graph
2046 bool ModelExecution::resolve_release_sequences(void *location, work_queue_t *work_queue)
2048 bool updated = false;
2049 SnapVector<struct release_seq *>::iterator it = pending_rel_seqs.begin();
2050 while (it != pending_rel_seqs.end()) {
2051 struct release_seq *pending = *it;
2052 ModelAction *acquire = pending->acquire;
2053 const ModelAction *read = pending->read;
2055 /* Only resolve sequences on the given location, if provided */
2056 if (location && read->get_location() != location) {
2061 const ModelAction *rf = read->get_reads_from();
2062 rel_heads_list_t release_heads;
2064 complete = release_seq_heads(rf, &release_heads, pending);
2065 for (unsigned int i = 0; i < release_heads.size(); i++)
2066 if (!acquire->has_synchronized_with(release_heads[i]))
2067 if (synchronize(release_heads[i], acquire))
2071 /* Re-check all pending release sequences */
2072 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2073 /* Re-check read-acquire for mo_graph edges */
2074 if (acquire->is_read())
2075 work_queue->push_back(MOEdgeWorkEntry(acquire));
2077 /* propagate synchronization to later actions */
2078 action_list_t::reverse_iterator rit = action_trace.rbegin();
2079 for (; (*rit) != acquire; rit++) {
2080 ModelAction *propagate = *rit;
2081 if (acquire->happens_before(propagate)) {
2082 synchronize(acquire, propagate);
2083 /* Re-check 'propagate' for mo_graph edges */
2084 work_queue->push_back(MOEdgeWorkEntry(propagate));
2089 it = pending_rel_seqs.erase(it);
2090 snapshot_free(pending);
2096 // If we resolved promises or data races, see if we have realized a data race.
2103 * Performs various bookkeeping operations for the current ModelAction. For
2104 * instance, adds action to the per-object, per-thread action vector and to the
2105 * action trace list of all thread actions.
2107 * @param act is the ModelAction to add.
2109 void ModelExecution::add_action_to_lists(ModelAction *act)
2111 int tid = id_to_int(act->get_tid());
2112 ModelAction *uninit = NULL;
2114 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
2115 if (list->empty() && act->is_atomic_var()) {
2116 uninit = get_uninitialized_action(act);
2117 uninit_id = id_to_int(uninit->get_tid());
2118 list->push_front(uninit);
2120 list->push_back(act);
2122 action_trace.push_back(act);
2124 action_trace.push_front(uninit);
2126 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
2127 if (tid >= (int)vec->size())
2128 vec->resize(priv->next_thread_id);
2129 (*vec)[tid].push_back(act);
2131 (*vec)[uninit_id].push_front(uninit);
2133 if ((int)thrd_last_action.size() <= tid)
2134 thrd_last_action.resize(get_num_threads());
2135 thrd_last_action[tid] = act;
2137 thrd_last_action[uninit_id] = uninit;
2139 if (act->is_fence() && act->is_release()) {
2140 if ((int)thrd_last_fence_release.size() <= tid)
2141 thrd_last_fence_release.resize(get_num_threads());
2142 thrd_last_fence_release[tid] = act;
2145 if (act->is_wait()) {
2146 void *mutex_loc = (void *) act->get_value();
2147 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
2149 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
2150 if (tid >= (int)vec->size())
2151 vec->resize(priv->next_thread_id);
2152 (*vec)[tid].push_back(act);
2157 * @brief Get the last action performed by a particular Thread
2158 * @param tid The thread ID of the Thread in question
2159 * @return The last action in the thread
2161 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
2163 int threadid = id_to_int(tid);
2164 if (threadid < (int)thrd_last_action.size())
2165 return thrd_last_action[id_to_int(tid)];
2171 * @brief Get the last fence release performed by a particular Thread
2172 * @param tid The thread ID of the Thread in question
2173 * @return The last fence release in the thread, if one exists; NULL otherwise
2175 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
2177 int threadid = id_to_int(tid);
2178 if (threadid < (int)thrd_last_fence_release.size())
2179 return thrd_last_fence_release[id_to_int(tid)];
2185 * Gets the last memory_order_seq_cst write (in the total global sequence)
2186 * performed on a particular object (i.e., memory location), not including the
2188 * @param curr The current ModelAction; also denotes the object location to
2190 * @return The last seq_cst write
2192 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
2194 void *location = curr->get_location();
2195 action_list_t *list = obj_map.get(location);
2196 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2197 action_list_t::reverse_iterator rit;
2198 for (rit = list->rbegin(); (*rit) != curr; rit++)
2200 rit++; /* Skip past curr */
2201 for ( ; rit != list->rend(); rit++)
2202 if ((*rit)->is_write() && (*rit)->is_seqcst())
2208 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2209 * performed in a particular thread, prior to a particular fence.
2210 * @param tid The ID of the thread to check
2211 * @param before_fence The fence from which to begin the search; if NULL, then
2212 * search for the most recent fence in the thread.
2213 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2215 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2217 /* All fences should have location FENCE_LOCATION */
2218 action_list_t *list = obj_map.get(FENCE_LOCATION);
2223 action_list_t::reverse_iterator rit = list->rbegin();
2226 for (; rit != list->rend(); rit++)
2227 if (*rit == before_fence)
2230 ASSERT(*rit == before_fence);
2234 for (; rit != list->rend(); rit++)
2235 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2241 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2242 * location). This function identifies the mutex according to the current
2243 * action, which is presumed to perform on the same mutex.
2244 * @param curr The current ModelAction; also denotes the object location to
2246 * @return The last unlock operation
2248 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
2250 void *location = curr->get_location();
2251 action_list_t *list = obj_map.get(location);
2252 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2253 action_list_t::reverse_iterator rit;
2254 for (rit = list->rbegin(); rit != list->rend(); rit++)
2255 if ((*rit)->is_unlock() || (*rit)->is_wait())
2260 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
2262 ModelAction *parent = get_last_action(tid);
2264 parent = get_thread(tid)->get_creation();
2269 * Returns the clock vector for a given thread.
2270 * @param tid The thread whose clock vector we want
2271 * @return Desired clock vector
2273 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
2275 return get_parent_action(tid)->get_cv();
2279 * @brief Find the promise (if any) to resolve for the current action and
2280 * remove it from the pending promise vector
2281 * @param curr The current ModelAction. Should be a write.
2282 * @return The Promise to resolve, if any; otherwise NULL
2284 Promise * ModelExecution::pop_promise_to_resolve(const ModelAction *curr)
2286 for (unsigned int i = 0; i < promises.size(); i++)
2287 if (curr->get_node()->get_promise(i)) {
2288 Promise *ret = promises[i];
2289 promises.erase(promises.begin() + i);
2296 * Resolve a Promise with a current write.
2297 * @param write The ModelAction that is fulfilling Promises
2298 * @param promise The Promise to resolve
2299 * @return True if the Promise was successfully resolved; false otherwise
2301 bool ModelExecution::resolve_promise(ModelAction *write, Promise *promise)
2303 ModelVector<ModelAction *> actions_to_check;
2305 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2306 ModelAction *read = promise->get_reader(i);
2307 read_from(read, write);
2308 actions_to_check.push_back(read);
2310 /* Make sure the promise's value matches the write's value */
2311 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2312 if (!mo_graph->resolvePromise(promise, write))
2313 priv->failed_promise = true;
2316 * @todo It is possible to end up in an inconsistent state, where a
2317 * "resolved" promise may still be referenced if
2318 * CycleGraph::resolvePromise() failed, so don't delete 'promise'.
2320 * Note that the inconsistency only matters when dumping mo_graph to
2326 //Check whether reading these writes has made threads unable to
2328 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2329 ModelAction *read = actions_to_check[i];
2330 mo_check_promises(read, true);
2337 * Compute the set of promises that could potentially be satisfied by this
2338 * action. Note that the set computation actually appears in the Node, not in
2340 * @param curr The ModelAction that may satisfy promises
2342 void ModelExecution::compute_promises(ModelAction *curr)
2344 for (unsigned int i = 0; i < promises.size(); i++) {
2345 Promise *promise = promises[i];
2346 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2349 bool satisfy = true;
2350 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2351 const ModelAction *act = promise->get_reader(j);
2352 if (act->happens_before(curr) ||
2353 act->could_synchronize_with(curr)) {
2359 curr->get_node()->set_promise(i);
2363 /** Checks promises in response to change in ClockVector Threads. */
2364 void ModelExecution::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2366 for (unsigned int i = 0; i < promises.size(); i++) {
2367 Promise *promise = promises[i];
2368 if (!promise->thread_is_available(tid))
2370 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2371 const ModelAction *act = promise->get_reader(j);
2372 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2373 merge_cv->synchronized_since(act)) {
2374 if (promise->eliminate_thread(tid)) {
2375 /* Promise has failed */
2376 priv->failed_promise = true;
2384 void ModelExecution::check_promises_thread_disabled()
2386 for (unsigned int i = 0; i < promises.size(); i++) {
2387 Promise *promise = promises[i];
2388 if (promise->has_failed()) {
2389 priv->failed_promise = true;
2396 * @brief Checks promises in response to addition to modification order for
2399 * We test whether threads are still available for satisfying promises after an
2400 * addition to our modification order constraints. Those that are unavailable
2401 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2402 * that promise has failed.
2404 * @param act The ModelAction which updated the modification order
2405 * @param is_read_check Should be true if act is a read and we must check for
2406 * updates to the store from which it read (there is a distinction here for
2407 * RMW's, which are both a load and a store)
2409 void ModelExecution::mo_check_promises(const ModelAction *act, bool is_read_check)
2411 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2413 for (unsigned int i = 0; i < promises.size(); i++) {
2414 Promise *promise = promises[i];
2416 // Is this promise on the same location?
2417 if (!promise->same_location(write))
2420 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2421 const ModelAction *pread = promise->get_reader(j);
2422 if (!pread->happens_before(act))
2424 if (mo_graph->checkPromise(write, promise)) {
2425 priv->failed_promise = true;
2431 // Don't do any lookups twice for the same thread
2432 if (!promise->thread_is_available(act->get_tid()))
2435 if (mo_graph->checkReachable(promise, write)) {
2436 if (mo_graph->checkPromise(write, promise)) {
2437 priv->failed_promise = true;
2445 * Compute the set of writes that may break the current pending release
2446 * sequence. This information is extracted from previou release sequence
2449 * @param curr The current ModelAction. Must be a release sequence fixup
2452 void ModelExecution::compute_relseq_breakwrites(ModelAction *curr)
2454 if (pending_rel_seqs.empty())
2457 struct release_seq *pending = pending_rel_seqs.back();
2458 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2459 const ModelAction *write = pending->writes[i];
2460 curr->get_node()->add_relseq_break(write);
2463 /* NULL means don't break the sequence; just synchronize */
2464 curr->get_node()->add_relseq_break(NULL);
2468 * Build up an initial set of all past writes that this 'read' action may read
2469 * from, as well as any previously-observed future values that must still be valid.
2471 * @param curr is the current ModelAction that we are exploring; it must be a
2474 void ModelExecution::build_may_read_from(ModelAction *curr)
2476 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
2478 ASSERT(curr->is_read());
2480 ModelAction *last_sc_write = NULL;
2482 if (curr->is_seqcst())
2483 last_sc_write = get_last_seq_cst_write(curr);
2485 /* Iterate over all threads */
2486 for (i = 0; i < thrd_lists->size(); i++) {
2487 /* Iterate over actions in thread, starting from most recent */
2488 action_list_t *list = &(*thrd_lists)[i];
2489 action_list_t::reverse_iterator rit;
2490 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2491 ModelAction *act = *rit;
2493 /* Only consider 'write' actions */
2494 if (!act->is_write() || act == curr)
2497 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2498 bool allow_read = true;
2500 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2502 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2506 /* Only add feasible reads */
2507 mo_graph->startChanges();
2508 r_modification_order(curr, act);
2509 if (!is_infeasible())
2510 curr->get_node()->add_read_from_past(act);
2511 mo_graph->rollbackChanges();
2514 /* Include at most one act per-thread that "happens before" curr */
2515 if (act->happens_before(curr))
2520 /* Inherit existing, promised future values */
2521 for (i = 0; i < promises.size(); i++) {
2522 const Promise *promise = promises[i];
2523 const ModelAction *promise_read = promise->get_reader(0);
2524 if (promise_read->same_var(curr)) {
2525 /* Only add feasible future-values */
2526 mo_graph->startChanges();
2527 r_modification_order(curr, promise);
2528 if (!is_infeasible())
2529 curr->get_node()->add_read_from_promise(promise_read);
2530 mo_graph->rollbackChanges();
2534 /* We may find no valid may-read-from only if the execution is doomed */
2535 if (!curr->get_node()->read_from_size()) {
2536 priv->no_valid_reads = true;
2540 if (DBG_ENABLED()) {
2541 model_print("Reached read action:\n");
2543 model_print("Printing read_from_past\n");
2544 curr->get_node()->print_read_from_past();
2545 model_print("End printing read_from_past\n");
2549 bool ModelExecution::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2551 for ( ; write != NULL; write = write->get_reads_from()) {
2552 /* UNINIT actions don't have a Node, and they never sleep */
2553 if (write->is_uninitialized())
2555 Node *prevnode = write->get_node()->get_parent();
2557 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2558 if (write->is_release() && thread_sleep)
2560 if (!write->is_rmw())
2567 * @brief Get an action representing an uninitialized atomic
2569 * This function may create a new one or try to retrieve one from the NodeStack
2571 * @param curr The current action, which prompts the creation of an UNINIT action
2572 * @return A pointer to the UNINIT ModelAction
2574 ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
2576 Node *node = curr->get_node();
2577 ModelAction *act = node->get_uninit_action();
2579 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
2580 node->set_uninit_action(act);
2582 act->create_cv(NULL);
2586 static void print_list(const action_list_t *list)
2588 action_list_t::const_iterator it;
2590 model_print("---------------------------------------------------------------------\n");
2592 unsigned int hash = 0;
2594 for (it = list->begin(); it != list->end(); it++) {
2595 const ModelAction *act = *it;
2596 if (act->get_seq_number() > 0)
2598 hash = hash^(hash<<3)^((*it)->hash());
2600 model_print("HASH %u\n", hash);
2601 model_print("---------------------------------------------------------------------\n");
2604 #if SUPPORT_MOD_ORDER_DUMP
2605 void ModelExecution::dumpGraph(char *filename) const
2608 sprintf(buffer, "%s.dot", filename);
2609 FILE *file = fopen(buffer, "w");
2610 fprintf(file, "digraph %s {\n", filename);
2611 mo_graph->dumpNodes(file);
2612 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2614 for (action_list_t::iterator it = action_trace.begin(); it != action_trace.end(); it++) {
2615 ModelAction *act = *it;
2616 if (act->is_read()) {
2617 mo_graph->dot_print_node(file, act);
2618 if (act->get_reads_from())
2619 mo_graph->dot_print_edge(file,
2620 act->get_reads_from(),
2622 "label=\"rf\", color=red, weight=2");
2624 mo_graph->dot_print_edge(file,
2625 act->get_reads_from_promise(),
2627 "label=\"rf\", color=red");
2629 if (thread_array[act->get_tid()]) {
2630 mo_graph->dot_print_edge(file,
2631 thread_array[id_to_int(act->get_tid())],
2633 "label=\"sb\", color=blue, weight=400");
2636 thread_array[act->get_tid()] = act;
2638 fprintf(file, "}\n");
2639 model_free(thread_array);
2644 /** @brief Prints an execution trace summary. */
2645 void ModelExecution::print_summary() const
2647 #if SUPPORT_MOD_ORDER_DUMP
2648 char buffername[100];
2649 sprintf(buffername, "exec%04u", get_execution_number());
2650 mo_graph->dumpGraphToFile(buffername);
2651 sprintf(buffername, "graph%04u", get_execution_number());
2652 dumpGraph(buffername);
2655 model_print("Execution %d:", get_execution_number());
2656 if (isfeasibleprefix()) {
2657 if (scheduler->all_threads_sleeping())
2658 model_print(" SLEEP-SET REDUNDANT");
2661 print_infeasibility(" INFEASIBLE");
2662 print_list(&action_trace);
2664 if (!promises.empty()) {
2665 model_print("Pending promises:\n");
2666 for (unsigned int i = 0; i < promises.size(); i++) {
2667 model_print(" [P%u] ", i);
2668 promises[i]->print();
2675 * Add a Thread to the system for the first time. Should only be called once
2677 * @param t The Thread to add
2679 void ModelExecution::add_thread(Thread *t)
2681 unsigned int i = id_to_int(t->get_id());
2682 if (i >= thread_map.size())
2683 thread_map.resize(i + 1);
2685 if (!t->is_model_thread())
2686 scheduler->add_thread(t);
2690 * @brief Get a Thread reference by its ID
2691 * @param tid The Thread's ID
2692 * @return A Thread reference
2694 Thread * ModelExecution::get_thread(thread_id_t tid) const
2696 unsigned int i = id_to_int(tid);
2697 if (i < thread_map.size())
2698 return thread_map[i];
2703 * @brief Get a reference to the Thread in which a ModelAction was executed
2704 * @param act The ModelAction
2705 * @return A Thread reference
2707 Thread * ModelExecution::get_thread(const ModelAction *act) const
2709 return get_thread(act->get_tid());
2713 * @brief Get a Promise's "promise number"
2715 * A "promise number" is an index number that is unique to a promise, valid
2716 * only for a specific snapshot of an execution trace. Promises may come and go
2717 * as they are generated an resolved, so an index only retains meaning for the
2720 * @param promise The Promise to check
2721 * @return The promise index, if the promise still is valid; otherwise -1
2723 int ModelExecution::get_promise_number(const Promise *promise) const
2725 for (unsigned int i = 0; i < promises.size(); i++)
2726 if (promises[i] == promise)
2733 * @brief Check if a Thread is currently enabled
2734 * @param t The Thread to check
2735 * @return True if the Thread is currently enabled
2737 bool ModelExecution::is_enabled(Thread *t) const
2739 return scheduler->is_enabled(t);
2743 * @brief Check if a Thread is currently enabled
2744 * @param tid The ID of the Thread to check
2745 * @return True if the Thread is currently enabled
2747 bool ModelExecution::is_enabled(thread_id_t tid) const
2749 return scheduler->is_enabled(tid);
2753 * @brief Select the next thread to execute based on the curren action
2755 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
2756 * actions should be followed by the execution of their child thread. In either
2757 * case, the current action should determine the next thread schedule.
2759 * @param curr The current action
2760 * @return The next thread to run, if the current action will determine this
2761 * selection; otherwise NULL
2763 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
2765 /* Do not split atomic RMW */
2766 if (curr->is_rmwr())
2767 return get_thread(curr);
2768 /* Follow CREATE with the created thread */
2769 if (curr->get_type() == THREAD_CREATE)
2770 return curr->get_thread_operand();
2774 /** @return True if the execution has taken too many steps */
2775 bool ModelExecution::too_many_steps() const
2777 return params->bound != 0 && priv->used_sequence_numbers > params->bound;
2781 * Takes the next step in the execution, if possible.
2782 * @param curr The current step to take
2783 * @return Returns the next Thread to run, if any; NULL if this execution
2786 Thread * ModelExecution::take_step(ModelAction *curr)
2788 Thread *curr_thrd = get_thread(curr);
2789 ASSERT(curr_thrd->get_state() == THREAD_READY);
2791 ASSERT(check_action_enabled(curr)); /* May have side effects? */
2792 curr = check_current_action(curr);
2795 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2796 scheduler->remove_thread(curr_thrd);
2798 return action_select_next_thread(curr);
2802 * Launch end-of-execution release sequence fixups only when
2803 * the execution is otherwise feasible AND there are:
2805 * (1) pending release sequences
2806 * (2) pending assertions that could be invalidated by a change
2807 * in clock vectors (i.e., data races)
2808 * (3) no pending promises
2810 void ModelExecution::fixup_release_sequences()
2812 while (!pending_rel_seqs.empty() &&
2813 is_feasible_prefix_ignore_relseq() &&
2814 !unrealizedraces.empty()) {
2815 model_print("*** WARNING: release sequence fixup action "
2816 "(%zu pending release seuqence(s)) ***\n",
2817 pending_rel_seqs.size());
2818 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2819 std::memory_order_seq_cst, NULL, VALUE_NONE,