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 const 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 * @brief Check if we are yield-blocked
270 * A program can be "yield-blocked" if all threads are ready to execute a
273 * @return True if the program is yield-blocked; false otherwise
275 bool ModelExecution::is_yieldblocked() const
277 if (!params->yieldblock)
280 for (unsigned int i = 0; i < get_num_threads(); i++) {
281 thread_id_t tid = int_to_id(i);
282 Thread *t = get_thread(tid);
283 if (t->get_pending() && t->get_pending()->is_yield())
290 * Check if this is a complete execution. That is, have all thread completed
291 * execution (rather than exiting because sleep sets have forced a redundant
294 * @return True if the execution is complete.
296 bool ModelExecution::is_complete_execution() const
298 if (is_yieldblocked())
300 for (unsigned int i = 0; i < get_num_threads(); i++)
301 if (is_enabled(int_to_id(i)))
307 * @brief Find the last fence-related backtracking conflict for a ModelAction
309 * This function performs the search for the most recent conflicting action
310 * against which we should perform backtracking, as affected by fence
311 * operations. This includes pairs of potentially-synchronizing actions which
312 * occur due to fence-acquire or fence-release, and hence should be explored in
313 * the opposite execution order.
315 * @param act The current action
316 * @return The most recent action which conflicts with act due to fences
318 ModelAction * ModelExecution::get_last_fence_conflict(ModelAction *act) const
320 /* Only perform release/acquire fence backtracking for stores */
321 if (!act->is_write())
324 /* Find a fence-release (or, act is a release) */
325 ModelAction *last_release;
326 if (act->is_release())
329 last_release = get_last_fence_release(act->get_tid());
333 /* Skip past the release */
334 const action_list_t *list = &action_trace;
335 action_list_t::const_reverse_iterator rit;
336 for (rit = list->rbegin(); rit != list->rend(); rit++)
337 if (*rit == last_release)
339 ASSERT(rit != list->rend());
344 * load --sb-> fence-acquire */
345 ModelVector<ModelAction *> acquire_fences(get_num_threads(), NULL);
346 ModelVector<ModelAction *> prior_loads(get_num_threads(), NULL);
347 bool found_acquire_fences = false;
348 for ( ; rit != list->rend(); rit++) {
349 ModelAction *prev = *rit;
350 if (act->same_thread(prev))
353 int tid = id_to_int(prev->get_tid());
355 if (prev->is_read() && act->same_var(prev)) {
356 if (prev->is_acquire()) {
357 /* Found most recent load-acquire, don't need
358 * to search for more fences */
359 if (!found_acquire_fences)
362 prior_loads[tid] = prev;
365 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
366 found_acquire_fences = true;
367 acquire_fences[tid] = prev;
371 ModelAction *latest_backtrack = NULL;
372 for (unsigned int i = 0; i < acquire_fences.size(); i++)
373 if (acquire_fences[i] && prior_loads[i])
374 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
375 latest_backtrack = acquire_fences[i];
376 return latest_backtrack;
380 * @brief Find the last backtracking conflict for a ModelAction
382 * This function performs the search for the most recent conflicting action
383 * against which we should perform backtracking. This primary includes pairs of
384 * synchronizing actions which should be explored in the opposite execution
387 * @param act The current action
388 * @return The most recent action which conflicts with act
390 ModelAction * ModelExecution::get_last_conflict(ModelAction *act) const
392 switch (act->get_type()) {
394 /* Only seq-cst fences can (directly) cause backtracking */
395 if (!act->is_seqcst())
400 ModelAction *ret = NULL;
402 /* linear search: from most recent to oldest */
403 action_list_t *list = obj_map.get(act->get_location());
404 action_list_t::reverse_iterator rit;
405 for (rit = list->rbegin(); rit != list->rend(); rit++) {
406 ModelAction *prev = *rit;
409 if (prev->could_synchronize_with(act)) {
415 ModelAction *ret2 = get_last_fence_conflict(act);
425 case ATOMIC_TRYLOCK: {
426 /* linear search: from most recent to oldest */
427 action_list_t *list = obj_map.get(act->get_location());
428 action_list_t::reverse_iterator rit;
429 for (rit = list->rbegin(); rit != list->rend(); rit++) {
430 ModelAction *prev = *rit;
431 if (act->is_conflicting_lock(prev))
436 case ATOMIC_UNLOCK: {
437 /* linear search: from most recent to oldest */
438 action_list_t *list = obj_map.get(act->get_location());
439 action_list_t::reverse_iterator rit;
440 for (rit = list->rbegin(); rit != list->rend(); rit++) {
441 ModelAction *prev = *rit;
442 if (!act->same_thread(prev) && prev->is_failed_trylock())
448 /* linear search: from most recent to oldest */
449 action_list_t *list = obj_map.get(act->get_location());
450 action_list_t::reverse_iterator rit;
451 for (rit = list->rbegin(); rit != list->rend(); rit++) {
452 ModelAction *prev = *rit;
453 if (!act->same_thread(prev) && prev->is_failed_trylock())
455 if (!act->same_thread(prev) && prev->is_notify())
461 case ATOMIC_NOTIFY_ALL:
462 case ATOMIC_NOTIFY_ONE: {
463 /* linear search: from most recent to oldest */
464 action_list_t *list = obj_map.get(act->get_location());
465 action_list_t::reverse_iterator rit;
466 for (rit = list->rbegin(); rit != list->rend(); rit++) {
467 ModelAction *prev = *rit;
468 if (!act->same_thread(prev) && prev->is_wait())
479 /** This method finds backtracking points where we should try to
480 * reorder the parameter ModelAction against.
482 * @param the ModelAction to find backtracking points for.
484 void ModelExecution::set_backtracking(ModelAction *act)
486 Thread *t = get_thread(act);
487 ModelAction *prev = get_last_conflict(act);
491 Node *node = prev->get_node()->get_parent();
493 /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
494 int low_tid, high_tid;
495 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
496 low_tid = id_to_int(act->get_tid());
497 high_tid = low_tid + 1;
500 high_tid = get_num_threads();
503 for (int i = low_tid; i < high_tid; i++) {
504 thread_id_t tid = int_to_id(i);
506 /* Make sure this thread can be enabled here. */
507 if (i >= node->get_num_threads())
510 /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
511 /* Don't backtrack into a point where the thread is disabled or sleeping. */
512 if (node->enabled_status(tid) != THREAD_ENABLED)
515 /* Check if this has been explored already */
516 if (node->has_been_explored(tid))
519 /* See if fairness allows */
520 if (params->fairwindow != 0 && !node->has_priority(tid)) {
522 for (int t = 0; t < node->get_num_threads(); t++) {
523 thread_id_t tother = int_to_id(t);
524 if (node->is_enabled(tother) && node->has_priority(tother)) {
533 /* See if CHESS-like yield fairness allows */
534 if (params->yieldon) {
536 for (int t = 0; t < node->get_num_threads(); t++) {
537 thread_id_t tother = int_to_id(t);
538 if (node->is_enabled(tother) && node->has_priority_over(tid, tother)) {
547 /* Cache the latest backtracking point */
548 set_latest_backtrack(prev);
550 /* If this is a new backtracking point, mark the tree */
551 if (!node->set_backtrack(tid))
553 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
554 id_to_int(prev->get_tid()),
555 id_to_int(t->get_id()));
564 * @brief Cache the a backtracking point as the "most recent", if eligible
566 * Note that this does not prepare the NodeStack for this backtracking
567 * operation, it only caches the action on a per-execution basis
569 * @param act The operation at which we should explore a different next action
570 * (i.e., backtracking point)
571 * @return True, if this action is now the most recent backtracking point;
574 bool ModelExecution::set_latest_backtrack(ModelAction *act)
576 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
577 priv->next_backtrack = act;
584 * Returns last backtracking point. The model checker will explore a different
585 * path for this point in the next execution.
586 * @return The ModelAction at which the next execution should diverge.
588 ModelAction * ModelExecution::get_next_backtrack()
590 ModelAction *next = priv->next_backtrack;
591 priv->next_backtrack = NULL;
596 * Processes a read model action.
597 * @param curr is the read model action to process.
598 * @return True if processing this read updates the mo_graph.
600 bool ModelExecution::process_read(ModelAction *curr)
602 Node *node = curr->get_node();
604 bool updated = false;
605 switch (node->get_read_from_status()) {
606 case READ_FROM_PAST: {
607 const ModelAction *rf = node->get_read_from_past();
610 mo_graph->startChanges();
612 ASSERT(!is_infeasible());
613 if (!check_recency(curr, rf)) {
614 if (node->increment_read_from()) {
615 mo_graph->rollbackChanges();
618 priv->too_many_reads = true;
622 updated = r_modification_order(curr, rf);
624 mo_graph->commitChanges();
625 mo_check_promises(curr, true);
628 case READ_FROM_PROMISE: {
629 Promise *promise = curr->get_node()->get_read_from_promise();
630 if (promise->add_reader(curr))
631 priv->failed_promise = true;
632 curr->set_read_from_promise(promise);
633 mo_graph->startChanges();
634 if (!check_recency(curr, promise))
635 priv->too_many_reads = true;
636 updated = r_modification_order(curr, promise);
637 mo_graph->commitChanges();
640 case READ_FROM_FUTURE: {
641 /* Read from future value */
642 struct future_value fv = node->get_future_value();
643 Promise *promise = new Promise(this, curr, fv);
644 curr->set_read_from_promise(promise);
645 promises.push_back(promise);
646 mo_graph->startChanges();
647 updated = r_modification_order(curr, promise);
648 mo_graph->commitChanges();
654 get_thread(curr)->set_return_value(curr->get_return_value());
660 * Processes a lock, trylock, or unlock model action. @param curr is
661 * the read model action to process.
663 * The try lock operation checks whether the lock is taken. If not,
664 * it falls to the normal lock operation case. If so, it returns
667 * The lock operation has already been checked that it is enabled, so
668 * it just grabs the lock and synchronizes with the previous unlock.
670 * The unlock operation has to re-enable all of the threads that are
671 * waiting on the lock.
673 * @return True if synchronization was updated; false otherwise
675 bool ModelExecution::process_mutex(ModelAction *curr)
677 std::mutex *mutex = curr->get_mutex();
678 struct std::mutex_state *state = NULL;
681 state = mutex->get_state();
683 switch (curr->get_type()) {
684 case ATOMIC_TRYLOCK: {
685 bool success = !state->locked;
686 curr->set_try_lock(success);
688 get_thread(curr)->set_return_value(0);
691 get_thread(curr)->set_return_value(1);
693 //otherwise fall into the lock case
695 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
696 assert_bug("Lock access before initialization");
697 state->locked = get_thread(curr);
698 ModelAction *unlock = get_last_unlock(curr);
699 //synchronize with the previous unlock statement
700 if (unlock != NULL) {
701 synchronize(unlock, curr);
707 case ATOMIC_UNLOCK: {
708 /* wake up the other threads */
709 for (unsigned int i = 0; i < get_num_threads(); i++) {
710 Thread *t = get_thread(int_to_id(i));
711 Thread *curr_thrd = get_thread(curr);
712 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
716 /* unlock the lock - after checking who was waiting on it */
717 state->locked = NULL;
719 if (!curr->is_wait())
720 break; /* The rest is only for ATOMIC_WAIT */
722 /* Should we go to sleep? (simulate spurious failures) */
723 if (curr->get_node()->get_misc() == 0) {
724 get_safe_ptr_action(&condvar_waiters_map, curr->get_location())->push_back(curr);
726 scheduler->sleep(get_thread(curr));
730 case ATOMIC_NOTIFY_ALL: {
731 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
732 //activate all the waiting threads
733 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
734 scheduler->wake(get_thread(*rit));
739 case ATOMIC_NOTIFY_ONE: {
740 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
741 int wakeupthread = curr->get_node()->get_misc();
742 action_list_t::iterator it = waiters->begin();
743 advance(it, wakeupthread);
744 scheduler->wake(get_thread(*it));
756 * @brief Check if the current pending promises allow a future value to be sent
758 * If one of the following is true:
759 * (a) there are no pending promises
760 * (b) the reader and writer do not cross any promises
761 * Then, it is safe to pass a future value back now.
763 * Otherwise, we must save the pending future value until (a) or (b) is true
765 * @param writer The operation which sends the future value. Must be a write.
766 * @param reader The operation which will observe the value. Must be a read.
767 * @return True if the future value can be sent now; false if it must wait.
769 bool ModelExecution::promises_may_allow(const ModelAction *writer,
770 const ModelAction *reader) const
772 if (promises.empty())
774 for (int i = promises.size() - 1; i >= 0; i--) {
775 ModelAction *pr = promises[i]->get_reader(0);
776 //reader is after promise...doesn't cross any promise
779 //writer is after promise, reader before...bad...
787 * @brief Add a future value to a reader
789 * This function performs a few additional checks to ensure that the future
790 * value can be feasibly observed by the reader
792 * @param writer The operation whose value is sent. Must be a write.
793 * @param reader The read operation which may read the future value. Must be a read.
795 void ModelExecution::add_future_value(const ModelAction *writer, ModelAction *reader)
797 /* Do more ambitious checks now that mo is more complete */
798 if (!mo_may_allow(writer, reader))
801 Node *node = reader->get_node();
803 /* Find an ancestor thread which exists at the time of the reader */
804 Thread *write_thread = get_thread(writer);
805 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
806 write_thread = write_thread->get_parent();
808 struct future_value fv = {
809 writer->get_write_value(),
810 writer->get_seq_number() + params->maxfuturedelay,
811 write_thread->get_id(),
813 if (node->add_future_value(fv))
814 set_latest_backtrack(reader);
818 * Process a write ModelAction
819 * @param curr The ModelAction to process
820 * @param work The work queue, for adding fixup work
821 * @return True if the mo_graph was updated or promises were resolved
823 bool ModelExecution::process_write(ModelAction *curr, work_queue_t *work)
825 /* Readers to which we may send our future value */
826 ModelVector<ModelAction *> send_fv;
828 const ModelAction *earliest_promise_reader;
829 bool updated_promises = false;
831 bool updated_mod_order = w_modification_order(curr, &send_fv);
832 Promise *promise = pop_promise_to_resolve(curr);
835 earliest_promise_reader = promise->get_reader(0);
836 updated_promises = resolve_promise(curr, promise, work);
838 earliest_promise_reader = NULL;
840 for (unsigned int i = 0; i < send_fv.size(); i++) {
841 ModelAction *read = send_fv[i];
843 /* Don't send future values to reads after the Promise we resolve */
844 if (!earliest_promise_reader || *read < *earliest_promise_reader) {
845 /* Check if future value can be sent immediately */
846 if (promises_may_allow(curr, read)) {
847 add_future_value(curr, read);
849 futurevalues.push_back(PendingFutureValue(curr, read));
854 /* Check the pending future values */
855 for (int i = (int)futurevalues.size() - 1; i >= 0; i--) {
856 struct PendingFutureValue pfv = futurevalues[i];
857 if (promises_may_allow(pfv.writer, pfv.reader)) {
858 add_future_value(pfv.writer, pfv.reader);
859 futurevalues.erase(futurevalues.begin() + i);
863 mo_graph->commitChanges();
864 mo_check_promises(curr, false);
866 get_thread(curr)->set_return_value(VALUE_NONE);
867 return updated_mod_order || updated_promises;
871 * Process a fence ModelAction
872 * @param curr The ModelAction to process
873 * @return True if synchronization was updated
875 bool ModelExecution::process_fence(ModelAction *curr)
878 * fence-relaxed: no-op
879 * fence-release: only log the occurence (not in this function), for
880 * use in later synchronization
881 * fence-acquire (this function): search for hypothetical release
883 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
885 bool updated = false;
886 if (curr->is_acquire()) {
887 action_list_t *list = &action_trace;
888 action_list_t::reverse_iterator rit;
889 /* Find X : is_read(X) && X --sb-> curr */
890 for (rit = list->rbegin(); rit != list->rend(); rit++) {
891 ModelAction *act = *rit;
894 if (act->get_tid() != curr->get_tid())
896 /* Stop at the beginning of the thread */
897 if (act->is_thread_start())
899 /* Stop once we reach a prior fence-acquire */
900 if (act->is_fence() && act->is_acquire())
904 /* read-acquire will find its own release sequences */
905 if (act->is_acquire())
908 /* Establish hypothetical release sequences */
909 rel_heads_list_t release_heads;
910 get_release_seq_heads(curr, act, &release_heads);
911 for (unsigned int i = 0; i < release_heads.size(); i++)
912 synchronize(release_heads[i], curr);
913 if (release_heads.size() != 0)
921 * @brief Process the current action for thread-related activity
923 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
924 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
925 * synchronization, etc. This function is a no-op for non-THREAD actions
926 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
928 * @param curr The current action
929 * @return True if synchronization was updated or a thread completed
931 bool ModelExecution::process_thread_action(ModelAction *curr)
933 bool updated = false;
935 switch (curr->get_type()) {
936 case THREAD_CREATE: {
937 thrd_t *thrd = (thrd_t *)curr->get_location();
938 struct thread_params *params = (struct thread_params *)curr->get_value();
939 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
941 th->set_creation(curr);
942 /* Promises can be satisfied by children */
943 for (unsigned int i = 0; i < promises.size(); i++) {
944 Promise *promise = promises[i];
945 if (promise->thread_is_available(curr->get_tid()))
946 promise->add_thread(th->get_id());
951 Thread *blocking = curr->get_thread_operand();
952 ModelAction *act = get_last_action(blocking->get_id());
953 synchronize(act, curr);
954 updated = true; /* trigger rel-seq checks */
957 case THREAD_FINISH: {
958 Thread *th = get_thread(curr);
959 /* Wake up any joining threads */
960 for (unsigned int i = 0; i < get_num_threads(); i++) {
961 Thread *waiting = get_thread(int_to_id(i));
962 if (waiting->waiting_on() == th &&
963 waiting->get_pending()->is_thread_join())
964 scheduler->wake(waiting);
967 /* Completed thread can't satisfy promises */
968 for (unsigned int i = 0; i < promises.size(); i++) {
969 Promise *promise = promises[i];
970 if (promise->thread_is_available(th->get_id()))
971 if (promise->eliminate_thread(th->get_id()))
972 priv->failed_promise = true;
974 updated = true; /* trigger rel-seq checks */
978 check_promises(curr->get_tid(), NULL, curr->get_cv());
989 * @brief Process the current action for release sequence fixup activity
991 * Performs model-checker release sequence fixups for the current action,
992 * forcing a single pending release sequence to break (with a given, potential
993 * "loose" write) or to complete (i.e., synchronize). If a pending release
994 * sequence forms a complete release sequence, then we must perform the fixup
995 * synchronization, mo_graph additions, etc.
997 * @param curr The current action; must be a release sequence fixup action
998 * @param work_queue The work queue to which to add work items as they are
1001 void ModelExecution::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1003 const ModelAction *write = curr->get_node()->get_relseq_break();
1004 struct release_seq *sequence = pending_rel_seqs.back();
1005 pending_rel_seqs.pop_back();
1007 ModelAction *acquire = sequence->acquire;
1008 const ModelAction *rf = sequence->rf;
1009 const ModelAction *release = sequence->release;
1013 ASSERT(release->same_thread(rf));
1015 if (write == NULL) {
1017 * @todo Forcing a synchronization requires that we set
1018 * modification order constraints. For instance, we can't allow
1019 * a fixup sequence in which two separate read-acquire
1020 * operations read from the same sequence, where the first one
1021 * synchronizes and the other doesn't. Essentially, we can't
1022 * allow any writes to insert themselves between 'release' and
1026 /* Must synchronize */
1027 if (!synchronize(release, acquire))
1030 /* Propagate the changed clock vector */
1031 propagate_clockvector(acquire, work_queue);
1033 /* Break release sequence with new edges:
1034 * release --mo--> write --mo--> rf */
1035 mo_graph->addEdge(release, write);
1036 mo_graph->addEdge(write, rf);
1039 /* See if we have realized a data race */
1044 * Initialize the current action by performing one or more of the following
1045 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1046 * in the NodeStack, manipulating backtracking sets, allocating and
1047 * initializing clock vectors, and computing the promises to fulfill.
1049 * @param curr The current action, as passed from the user context; may be
1050 * freed/invalidated after the execution of this function, with a different
1051 * action "returned" its place (pass-by-reference)
1052 * @return True if curr is a newly-explored action; false otherwise
1054 bool ModelExecution::initialize_curr_action(ModelAction **curr)
1056 ModelAction *newcurr;
1058 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1059 newcurr = process_rmw(*curr);
1062 if (newcurr->is_rmw())
1063 compute_promises(newcurr);
1069 (*curr)->set_seq_number(get_next_seq_num());
1071 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1073 /* First restore type and order in case of RMW operation */
1074 if ((*curr)->is_rmwr())
1075 newcurr->copy_typeandorder(*curr);
1077 ASSERT((*curr)->get_location() == newcurr->get_location());
1078 newcurr->copy_from_new(*curr);
1080 /* Discard duplicate ModelAction; use action from NodeStack */
1083 /* Always compute new clock vector */
1084 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1087 return false; /* Action was explored previously */
1091 /* Always compute new clock vector */
1092 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1094 /* Assign most recent release fence */
1095 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1098 * Perform one-time actions when pushing new ModelAction onto
1101 if (newcurr->is_write())
1102 compute_promises(newcurr);
1103 else if (newcurr->is_relseq_fixup())
1104 compute_relseq_breakwrites(newcurr);
1105 else if (newcurr->is_wait())
1106 newcurr->get_node()->set_misc_max(2);
1107 else if (newcurr->is_notify_one()) {
1108 newcurr->get_node()->set_misc_max(get_safe_ptr_action(&condvar_waiters_map, newcurr->get_location())->size());
1110 return true; /* This was a new ModelAction */
1115 * @brief Establish reads-from relation between two actions
1117 * Perform basic operations involved with establishing a concrete rf relation,
1118 * including setting the ModelAction data and checking for release sequences.
1120 * @param act The action that is reading (must be a read)
1121 * @param rf The action from which we are reading (must be a write)
1123 * @return True if this read established synchronization
1125 bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
1128 ASSERT(rf->is_write());
1130 act->set_read_from(rf);
1131 if (act->is_acquire()) {
1132 rel_heads_list_t release_heads;
1133 get_release_seq_heads(act, act, &release_heads);
1134 int num_heads = release_heads.size();
1135 for (unsigned int i = 0; i < release_heads.size(); i++)
1136 if (!synchronize(release_heads[i], act))
1138 return num_heads > 0;
1144 * @brief Synchronizes two actions
1146 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
1147 * This function performs the synchronization as well as providing other hooks
1148 * for other checks along with synchronization.
1150 * @param first The left-hand side of the synchronizes-with relation
1151 * @param second The right-hand side of the synchronizes-with relation
1152 * @return True if the synchronization was successful (i.e., was consistent
1153 * with the execution order); false otherwise
1155 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
1157 if (*second < *first) {
1158 set_bad_synchronization();
1161 check_promises(first->get_tid(), second->get_cv(), first->get_cv());
1162 return second->synchronize_with(first);
1166 * Check promises and eliminate potentially-satisfying threads when a thread is
1167 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1168 * no longer satisfy a promise generated from that thread.
1170 * @param blocker The thread on which a thread is waiting
1171 * @param waiting The waiting thread
1173 void ModelExecution::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1175 for (unsigned int i = 0; i < promises.size(); i++) {
1176 Promise *promise = promises[i];
1177 if (!promise->thread_is_available(waiting->get_id()))
1179 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1180 ModelAction *reader = promise->get_reader(j);
1181 if (reader->get_tid() != blocker->get_id())
1183 if (promise->eliminate_thread(waiting->get_id())) {
1184 /* Promise has failed */
1185 priv->failed_promise = true;
1187 /* Only eliminate the 'waiting' thread once */
1195 * @brief Check whether a model action is enabled.
1197 * Checks whether an operation would be successful (i.e., is a lock already
1198 * locked, or is the joined thread already complete).
1200 * For yield-blocking, yields are never enabled.
1202 * @param curr is the ModelAction to check whether it is enabled.
1203 * @return a bool that indicates whether the action is enabled.
1205 bool ModelExecution::check_action_enabled(ModelAction *curr) {
1206 if (curr->is_lock()) {
1207 std::mutex *lock = curr->get_mutex();
1208 struct std::mutex_state *state = lock->get_state();
1211 } else if (curr->is_thread_join()) {
1212 Thread *blocking = curr->get_thread_operand();
1213 if (!blocking->is_complete()) {
1214 thread_blocking_check_promises(blocking, get_thread(curr));
1217 } else if (params->yieldblock && curr->is_yield()) {
1225 * This is the heart of the model checker routine. It performs model-checking
1226 * actions corresponding to a given "current action." Among other processes, it
1227 * calculates reads-from relationships, updates synchronization clock vectors,
1228 * forms a memory_order constraints graph, and handles replay/backtrack
1229 * execution when running permutations of previously-observed executions.
1231 * @param curr The current action to process
1232 * @return The ModelAction that is actually executed; may be different than
1235 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
1238 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1239 bool newly_explored = initialize_curr_action(&curr);
1243 wake_up_sleeping_actions(curr);
1245 /* Compute fairness information for CHESS yield algorithm */
1246 if (params->yieldon) {
1247 curr->get_node()->update_yield(scheduler);
1250 /* Add the action to lists before any other model-checking tasks */
1251 if (!second_part_of_rmw)
1252 add_action_to_lists(curr);
1254 /* Build may_read_from set for newly-created actions */
1255 if (newly_explored && curr->is_read())
1256 build_may_read_from(curr);
1258 /* Initialize work_queue with the "current action" work */
1259 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1260 while (!work_queue.empty() && !has_asserted()) {
1261 WorkQueueEntry work = work_queue.front();
1262 work_queue.pop_front();
1264 switch (work.type) {
1265 case WORK_CHECK_CURR_ACTION: {
1266 ModelAction *act = work.action;
1267 bool update = false; /* update this location's release seq's */
1268 bool update_all = false; /* update all release seq's */
1270 if (process_thread_action(curr))
1273 if (act->is_read() && !second_part_of_rmw && process_read(act))
1276 if (act->is_write() && process_write(act, &work_queue))
1279 if (act->is_fence() && process_fence(act))
1282 if (act->is_mutex_op() && process_mutex(act))
1285 if (act->is_relseq_fixup())
1286 process_relseq_fixup(curr, &work_queue);
1289 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1291 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1294 case WORK_CHECK_RELEASE_SEQ:
1295 resolve_release_sequences(work.location, &work_queue);
1297 case WORK_CHECK_MO_EDGES: {
1298 /** @todo Complete verification of work_queue */
1299 ModelAction *act = work.action;
1300 bool updated = false;
1302 if (act->is_read()) {
1303 const ModelAction *rf = act->get_reads_from();
1304 const Promise *promise = act->get_reads_from_promise();
1306 if (r_modification_order(act, rf))
1308 } else if (promise) {
1309 if (r_modification_order(act, promise))
1313 if (act->is_write()) {
1314 if (w_modification_order(act, NULL))
1317 mo_graph->commitChanges();
1320 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1329 check_curr_backtracking(curr);
1330 set_backtracking(curr);
1334 void ModelExecution::check_curr_backtracking(ModelAction *curr)
1336 Node *currnode = curr->get_node();
1337 Node *parnode = currnode->get_parent();
1339 if ((parnode && !parnode->backtrack_empty()) ||
1340 !currnode->misc_empty() ||
1341 !currnode->read_from_empty() ||
1342 !currnode->promise_empty() ||
1343 !currnode->relseq_break_empty()) {
1344 set_latest_backtrack(curr);
1348 bool ModelExecution::promises_expired() const
1350 for (unsigned int i = 0; i < promises.size(); i++) {
1351 Promise *promise = promises[i];
1352 if (promise->get_expiration() < priv->used_sequence_numbers)
1359 * This is the strongest feasibility check available.
1360 * @return whether the current trace (partial or complete) must be a prefix of
1363 bool ModelExecution::isfeasibleprefix() const
1365 return pending_rel_seqs.size() == 0 && is_feasible_prefix_ignore_relseq();
1369 * Print disagnostic information about an infeasible execution
1370 * @param prefix A string to prefix the output with; if NULL, then a default
1371 * message prefix will be provided
1373 void ModelExecution::print_infeasibility(const char *prefix) const
1377 if (mo_graph->checkForCycles())
1378 ptr += sprintf(ptr, "[mo cycle]");
1379 if (priv->failed_promise)
1380 ptr += sprintf(ptr, "[failed promise]");
1381 if (priv->too_many_reads)
1382 ptr += sprintf(ptr, "[too many reads]");
1383 if (priv->no_valid_reads)
1384 ptr += sprintf(ptr, "[no valid reads-from]");
1385 if (priv->bad_synchronization)
1386 ptr += sprintf(ptr, "[bad sw ordering]");
1387 if (promises_expired())
1388 ptr += sprintf(ptr, "[promise expired]");
1389 if (promises.size() != 0)
1390 ptr += sprintf(ptr, "[unresolved promise]");
1392 model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
1396 * Returns whether the current completed trace is feasible, except for pending
1397 * release sequences.
1399 bool ModelExecution::is_feasible_prefix_ignore_relseq() const
1401 return !is_infeasible() && promises.size() == 0;
1405 * Check if the current partial trace is infeasible. Does not check any
1406 * end-of-execution flags, which might rule out the execution. Thus, this is
1407 * useful only for ruling an execution as infeasible.
1408 * @return whether the current partial trace is infeasible.
1410 bool ModelExecution::is_infeasible() const
1412 return mo_graph->checkForCycles() ||
1413 priv->no_valid_reads ||
1414 priv->failed_promise ||
1415 priv->too_many_reads ||
1416 priv->bad_synchronization ||
1420 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1421 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
1422 ModelAction *lastread = get_last_action(act->get_tid());
1423 lastread->process_rmw(act);
1424 if (act->is_rmw()) {
1425 if (lastread->get_reads_from())
1426 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1428 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1429 mo_graph->commitChanges();
1435 * A helper function for ModelExecution::check_recency, to check if the current
1436 * thread is able to read from a different write/promise for 'params.maxreads'
1437 * number of steps and if that write/promise should become visible (i.e., is
1438 * ordered later in the modification order). This helps model memory liveness.
1440 * @param curr The current action. Must be a read.
1441 * @param rf The write/promise from which we plan to read
1442 * @param other_rf The write/promise from which we may read
1443 * @return True if we were able to read from other_rf for params.maxreads steps
1445 template <typename T, typename U>
1446 bool ModelExecution::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
1448 /* Need a different write/promise */
1449 if (other_rf->equals(rf))
1452 /* Only look for "newer" writes/promises */
1453 if (!mo_graph->checkReachable(rf, other_rf))
1456 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1457 action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
1458 action_list_t::reverse_iterator rit = list->rbegin();
1459 ASSERT((*rit) == curr);
1460 /* Skip past curr */
1463 /* Does this write/promise work for everyone? */
1464 for (int i = 0; i < params->maxreads; i++, rit++) {
1465 ModelAction *act = *rit;
1466 if (!act->may_read_from(other_rf))
1473 * Checks whether a thread has read from the same write or Promise for too many
1474 * times without seeing the effects of a later write/Promise.
1477 * 1) there must a different write/promise that we could read from,
1478 * 2) we must have read from the same write/promise in excess of maxreads times,
1479 * 3) that other write/promise must have been in the reads_from set for maxreads times, and
1480 * 4) that other write/promise must be mod-ordered after the write/promise we are reading.
1482 * If so, we decide that the execution is no longer feasible.
1484 * @param curr The current action. Must be a read.
1485 * @param rf The ModelAction/Promise from which we might read.
1486 * @return True if the read should succeed; false otherwise
1488 template <typename T>
1489 bool ModelExecution::check_recency(ModelAction *curr, const T *rf) const
1491 if (!params->maxreads)
1494 //NOTE: Next check is just optimization, not really necessary....
1495 if (curr->get_node()->get_read_from_past_size() +
1496 curr->get_node()->get_read_from_promise_size() <= 1)
1499 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1500 int tid = id_to_int(curr->get_tid());
1501 ASSERT(tid < (int)thrd_lists->size());
1502 action_list_t *list = &(*thrd_lists)[tid];
1503 action_list_t::reverse_iterator rit = list->rbegin();
1504 ASSERT((*rit) == curr);
1505 /* Skip past curr */
1508 action_list_t::reverse_iterator ritcopy = rit;
1509 /* See if we have enough reads from the same value */
1510 for (int count = 0; count < params->maxreads; ritcopy++, count++) {
1511 if (ritcopy == list->rend())
1513 ModelAction *act = *ritcopy;
1514 if (!act->is_read())
1516 if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
1518 if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
1520 if (act->get_node()->get_read_from_past_size() +
1521 act->get_node()->get_read_from_promise_size() <= 1)
1524 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1525 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1526 if (should_read_instead(curr, rf, write))
1527 return false; /* liveness failure */
1529 for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
1530 const Promise *promise = curr->get_node()->get_read_from_promise(i);
1531 if (should_read_instead(curr, rf, promise))
1532 return false; /* liveness failure */
1538 * @brief Updates the mo_graph with the constraints imposed from the current
1541 * Basic idea is the following: Go through each other thread and find
1542 * the last action that happened before our read. Two cases:
1544 * -# The action is a write: that write must either occur before
1545 * the write we read from or be the write we read from.
1546 * -# The action is a read: the write that that action read from
1547 * must occur before the write we read from or be the same write.
1549 * @param curr The current action. Must be a read.
1550 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1551 * @return True if modification order edges were added; false otherwise
1553 template <typename rf_type>
1554 bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
1556 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1559 ASSERT(curr->is_read());
1561 /* Last SC fence in the current thread */
1562 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1563 ModelAction *last_sc_write = NULL;
1564 if (curr->is_seqcst())
1565 last_sc_write = get_last_seq_cst_write(curr);
1567 /* Iterate over all threads */
1568 for (i = 0; i < thrd_lists->size(); i++) {
1569 /* Last SC fence in thread i */
1570 ModelAction *last_sc_fence_thread_local = NULL;
1571 if (int_to_id((int)i) != curr->get_tid())
1572 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1574 /* Last SC fence in thread i, before last SC fence in current thread */
1575 ModelAction *last_sc_fence_thread_before = NULL;
1576 if (last_sc_fence_local)
1577 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1579 /* Iterate over actions in thread, starting from most recent */
1580 action_list_t *list = &(*thrd_lists)[i];
1581 action_list_t::reverse_iterator rit;
1582 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1583 ModelAction *act = *rit;
1588 /* Don't want to add reflexive edges on 'rf' */
1589 if (act->equals(rf)) {
1590 if (act->happens_before(curr))
1596 if (act->is_write()) {
1597 /* C++, Section 29.3 statement 5 */
1598 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1599 *act < *last_sc_fence_thread_local) {
1600 added = mo_graph->addEdge(act, rf) || added;
1603 /* C++, Section 29.3 statement 4 */
1604 else if (act->is_seqcst() && last_sc_fence_local &&
1605 *act < *last_sc_fence_local) {
1606 added = mo_graph->addEdge(act, rf) || added;
1609 /* C++, Section 29.3 statement 6 */
1610 else if (last_sc_fence_thread_before &&
1611 *act < *last_sc_fence_thread_before) {
1612 added = mo_graph->addEdge(act, rf) || added;
1617 /* C++, Section 29.3 statement 3 (second subpoint) */
1618 if (curr->is_seqcst() && last_sc_write && act == last_sc_write) {
1619 added = mo_graph->addEdge(act, rf) || added;
1624 * Include at most one act per-thread that "happens
1627 if (act->happens_before(curr)) {
1628 if (act->is_write()) {
1629 added = mo_graph->addEdge(act, rf) || added;
1631 const ModelAction *prevrf = act->get_reads_from();
1632 const Promise *prevrf_promise = act->get_reads_from_promise();
1634 if (!prevrf->equals(rf))
1635 added = mo_graph->addEdge(prevrf, rf) || added;
1636 } else if (!prevrf_promise->equals(rf)) {
1637 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1646 * All compatible, thread-exclusive promises must be ordered after any
1647 * concrete loads from the same thread
1649 for (unsigned int i = 0; i < promises.size(); i++)
1650 if (promises[i]->is_compatible_exclusive(curr))
1651 added = mo_graph->addEdge(rf, promises[i]) || added;
1657 * Updates the mo_graph with the constraints imposed from the current write.
1659 * Basic idea is the following: Go through each other thread and find
1660 * the lastest action that happened before our write. Two cases:
1662 * (1) The action is a write => that write must occur before
1665 * (2) The action is a read => the write that that action read from
1666 * must occur before the current write.
1668 * This method also handles two other issues:
1670 * (I) Sequential Consistency: Making sure that if the current write is
1671 * seq_cst, that it occurs after the previous seq_cst write.
1673 * (II) Sending the write back to non-synchronizing reads.
1675 * @param curr The current action. Must be a write.
1676 * @param send_fv A vector for stashing reads to which we may pass our future
1677 * value. If NULL, then don't record any future values.
1678 * @return True if modification order edges were added; false otherwise
1680 bool ModelExecution::w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv)
1682 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1685 ASSERT(curr->is_write());
1687 if (curr->is_seqcst()) {
1688 /* We have to at least see the last sequentially consistent write,
1689 so we are initialized. */
1690 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1691 if (last_seq_cst != NULL) {
1692 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1696 /* Last SC fence in the current thread */
1697 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1699 /* Iterate over all threads */
1700 for (i = 0; i < thrd_lists->size(); i++) {
1701 /* Last SC fence in thread i, before last SC fence in current thread */
1702 ModelAction *last_sc_fence_thread_before = NULL;
1703 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1704 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1706 /* Iterate over actions in thread, starting from most recent */
1707 action_list_t *list = &(*thrd_lists)[i];
1708 action_list_t::reverse_iterator rit;
1709 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1710 ModelAction *act = *rit;
1713 * 1) If RMW and it actually read from something, then we
1714 * already have all relevant edges, so just skip to next
1717 * 2) If RMW and it didn't read from anything, we should
1718 * whatever edge we can get to speed up convergence.
1720 * 3) If normal write, we need to look at earlier actions, so
1721 * continue processing list.
1723 if (curr->is_rmw()) {
1724 if (curr->get_reads_from() != NULL)
1732 /* C++, Section 29.3 statement 7 */
1733 if (last_sc_fence_thread_before && act->is_write() &&
1734 *act < *last_sc_fence_thread_before) {
1735 added = mo_graph->addEdge(act, curr) || added;
1740 * Include at most one act per-thread that "happens
1743 if (act->happens_before(curr)) {
1745 * Note: if act is RMW, just add edge:
1747 * The following edge should be handled elsewhere:
1748 * readfrom(act) --mo--> act
1750 if (act->is_write())
1751 added = mo_graph->addEdge(act, curr) || added;
1752 else if (act->is_read()) {
1753 //if previous read accessed a null, just keep going
1754 if (act->get_reads_from() == NULL)
1756 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
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 (send_fv && thin_air_constraint_may_allow(curr, act)) {
1774 if (!is_infeasible())
1775 send_fv->push_back(act);
1776 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1777 add_future_value(curr, act);
1784 * All compatible, thread-exclusive promises must be ordered after any
1785 * concrete stores to the same thread, or else they can be merged with
1788 for (unsigned int i = 0; i < promises.size(); i++)
1789 if (promises[i]->is_compatible_exclusive(curr))
1790 added = mo_graph->addEdge(curr, promises[i]) || added;
1795 /** Arbitrary reads from the future are not allowed. Section 29.3
1796 * part 9 places some constraints. This method checks one result of constraint
1797 * constraint. Others require compiler support. */
1798 bool ModelExecution::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader) const
1800 if (!writer->is_rmw())
1803 if (!reader->is_rmw())
1806 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1807 if (search == reader)
1809 if (search->get_tid() == reader->get_tid() &&
1810 search->happens_before(reader))
1818 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1819 * some constraints. This method checks one the following constraint (others
1820 * require compiler support):
1822 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1823 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
1825 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1827 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1829 /* Iterate over all threads */
1830 for (i = 0; i < thrd_lists->size(); i++) {
1831 const ModelAction *write_after_read = NULL;
1833 /* Iterate over actions in thread, starting from most recent */
1834 action_list_t *list = &(*thrd_lists)[i];
1835 action_list_t::reverse_iterator rit;
1836 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1837 ModelAction *act = *rit;
1839 /* Don't disallow due to act == reader */
1840 if (!reader->happens_before(act) || reader == act)
1842 else if (act->is_write())
1843 write_after_read = act;
1844 else if (act->is_read() && act->get_reads_from() != NULL)
1845 write_after_read = act->get_reads_from();
1848 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1855 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1856 * The ModelAction under consideration is expected to be taking part in
1857 * release/acquire synchronization as an object of the "reads from" relation.
1858 * Note that this can only provide release sequence support for RMW chains
1859 * which do not read from the future, as those actions cannot be traced until
1860 * their "promise" is fulfilled. Similarly, we may not even establish the
1861 * presence of a release sequence with certainty, as some modification order
1862 * constraints may be decided further in the future. Thus, this function
1863 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1864 * and a boolean representing certainty.
1866 * @param rf The action that might be part of a release sequence. Must be a
1868 * @param release_heads A pass-by-reference style return parameter. After
1869 * execution of this function, release_heads will contain the heads of all the
1870 * relevant release sequences, if any exists with certainty
1871 * @param pending A pass-by-reference style return parameter which is only used
1872 * when returning false (i.e., uncertain). Returns most information regarding
1873 * an uncertain release sequence, including any write operations that might
1874 * break the sequence.
1875 * @return true, if the ModelExecution is certain that release_heads is complete;
1878 bool ModelExecution::release_seq_heads(const ModelAction *rf,
1879 rel_heads_list_t *release_heads,
1880 struct release_seq *pending) const
1882 /* Only check for release sequences if there are no cycles */
1883 if (mo_graph->checkForCycles())
1886 for ( ; rf != NULL; rf = rf->get_reads_from()) {
1887 ASSERT(rf->is_write());
1889 if (rf->is_release())
1890 release_heads->push_back(rf);
1891 else if (rf->get_last_fence_release())
1892 release_heads->push_back(rf->get_last_fence_release());
1894 break; /* End of RMW chain */
1896 /** @todo Need to be smarter here... In the linux lock
1897 * example, this will run to the beginning of the program for
1899 /** @todo The way to be smarter here is to keep going until 1
1900 * thread has a release preceded by an acquire and you've seen
1903 /* acq_rel RMW is a sufficient stopping condition */
1904 if (rf->is_acquire() && rf->is_release())
1905 return true; /* complete */
1908 /* read from future: need to settle this later */
1910 return false; /* incomplete */
1913 if (rf->is_release())
1914 return true; /* complete */
1916 /* else relaxed write
1917 * - check for fence-release in the same thread (29.8, stmt. 3)
1918 * - check modification order for contiguous subsequence
1919 * -> rf must be same thread as release */
1921 const ModelAction *fence_release = rf->get_last_fence_release();
1922 /* Synchronize with a fence-release unconditionally; we don't need to
1923 * find any more "contiguous subsequence..." for it */
1925 release_heads->push_back(fence_release);
1927 int tid = id_to_int(rf->get_tid());
1928 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(rf->get_location());
1929 action_list_t *list = &(*thrd_lists)[tid];
1930 action_list_t::const_reverse_iterator rit;
1932 /* Find rf in the thread list */
1933 rit = std::find(list->rbegin(), list->rend(), rf);
1934 ASSERT(rit != list->rend());
1936 /* Find the last {write,fence}-release */
1937 for (; rit != list->rend(); rit++) {
1938 if (fence_release && *(*rit) < *fence_release)
1940 if ((*rit)->is_release())
1943 if (rit == list->rend()) {
1944 /* No write-release in this thread */
1945 return true; /* complete */
1946 } else if (fence_release && *(*rit) < *fence_release) {
1947 /* The fence-release is more recent (and so, "stronger") than
1948 * the most recent write-release */
1949 return true; /* complete */
1950 } /* else, need to establish contiguous release sequence */
1951 ModelAction *release = *rit;
1953 ASSERT(rf->same_thread(release));
1955 pending->writes.clear();
1957 bool certain = true;
1958 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1959 if (id_to_int(rf->get_tid()) == (int)i)
1961 list = &(*thrd_lists)[i];
1963 /* Can we ensure no future writes from this thread may break
1964 * the release seq? */
1965 bool future_ordered = false;
1967 ModelAction *last = get_last_action(int_to_id(i));
1968 Thread *th = get_thread(int_to_id(i));
1969 if ((last && rf->happens_before(last)) ||
1972 future_ordered = true;
1974 ASSERT(!th->is_model_thread() || future_ordered);
1976 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1977 const ModelAction *act = *rit;
1978 /* Reach synchronization -> this thread is complete */
1979 if (act->happens_before(release))
1981 if (rf->happens_before(act)) {
1982 future_ordered = true;
1986 /* Only non-RMW writes can break release sequences */
1987 if (!act->is_write() || act->is_rmw())
1990 /* Check modification order */
1991 if (mo_graph->checkReachable(rf, act)) {
1992 /* rf --mo--> act */
1993 future_ordered = true;
1996 if (mo_graph->checkReachable(act, release))
1997 /* act --mo--> release */
1999 if (mo_graph->checkReachable(release, act) &&
2000 mo_graph->checkReachable(act, rf)) {
2001 /* release --mo-> act --mo--> rf */
2002 return true; /* complete */
2004 /* act may break release sequence */
2005 pending->writes.push_back(act);
2008 if (!future_ordered)
2009 certain = false; /* This thread is uncertain */
2013 release_heads->push_back(release);
2014 pending->writes.clear();
2016 pending->release = release;
2023 * An interface for getting the release sequence head(s) with which a
2024 * given ModelAction must synchronize. This function only returns a non-empty
2025 * result when it can locate a release sequence head with certainty. Otherwise,
2026 * it may mark the internal state of the ModelExecution so that it will handle
2027 * the release sequence at a later time, causing @a acquire to update its
2028 * synchronization at some later point in execution.
2030 * @param acquire The 'acquire' action that may synchronize with a release
2032 * @param read The read action that may read from a release sequence; this may
2033 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2034 * when 'acquire' is a fence-acquire)
2035 * @param release_heads A pass-by-reference return parameter. Will be filled
2036 * with the head(s) of the release sequence(s), if they exists with certainty.
2037 * @see ModelExecution::release_seq_heads
2039 void ModelExecution::get_release_seq_heads(ModelAction *acquire,
2040 ModelAction *read, rel_heads_list_t *release_heads)
2042 const ModelAction *rf = read->get_reads_from();
2043 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2044 sequence->acquire = acquire;
2045 sequence->read = read;
2047 if (!release_seq_heads(rf, release_heads, sequence)) {
2048 /* add act to 'lazy checking' list */
2049 pending_rel_seqs.push_back(sequence);
2051 snapshot_free(sequence);
2056 * @brief Propagate a modified clock vector to actions later in the execution
2059 * After an acquire operation lazily completes a release-sequence
2060 * synchronization, we must update all clock vectors for operations later than
2061 * the acquire in the execution order.
2063 * @param acquire The ModelAction whose clock vector must be propagated
2064 * @param work The work queue to which we can add work items, if this
2065 * propagation triggers more updates (e.g., to the modification order)
2067 void ModelExecution::propagate_clockvector(ModelAction *acquire, work_queue_t *work)
2069 /* Re-check all pending release sequences */
2070 work->push_back(CheckRelSeqWorkEntry(NULL));
2071 /* Re-check read-acquire for mo_graph edges */
2072 work->push_back(MOEdgeWorkEntry(acquire));
2074 /* propagate synchronization to later actions */
2075 action_list_t::reverse_iterator rit = action_trace.rbegin();
2076 for (; (*rit) != acquire; rit++) {
2077 ModelAction *propagate = *rit;
2078 if (acquire->happens_before(propagate)) {
2079 synchronize(acquire, propagate);
2080 /* Re-check 'propagate' for mo_graph edges */
2081 work->push_back(MOEdgeWorkEntry(propagate));
2087 * Attempt to resolve all stashed operations that might synchronize with a
2088 * release sequence for a given location. This implements the "lazy" portion of
2089 * determining whether or not a release sequence was contiguous, since not all
2090 * modification order information is present at the time an action occurs.
2092 * @param location The location/object that should be checked for release
2093 * sequence resolutions. A NULL value means to check all locations.
2094 * @param work_queue The work queue to which to add work items as they are
2096 * @return True if any updates occurred (new synchronization, new mo_graph
2099 bool ModelExecution::resolve_release_sequences(void *location, work_queue_t *work_queue)
2101 bool updated = false;
2102 SnapVector<struct release_seq *>::iterator it = pending_rel_seqs.begin();
2103 while (it != pending_rel_seqs.end()) {
2104 struct release_seq *pending = *it;
2105 ModelAction *acquire = pending->acquire;
2106 const ModelAction *read = pending->read;
2108 /* Only resolve sequences on the given location, if provided */
2109 if (location && read->get_location() != location) {
2114 const ModelAction *rf = read->get_reads_from();
2115 rel_heads_list_t release_heads;
2117 complete = release_seq_heads(rf, &release_heads, pending);
2118 for (unsigned int i = 0; i < release_heads.size(); i++)
2119 if (!acquire->has_synchronized_with(release_heads[i]))
2120 if (synchronize(release_heads[i], acquire))
2124 /* Propagate the changed clock vector */
2125 propagate_clockvector(acquire, work_queue);
2128 it = pending_rel_seqs.erase(it);
2129 snapshot_free(pending);
2135 // If we resolved promises or data races, see if we have realized a data race.
2142 * Performs various bookkeeping operations for the current ModelAction. For
2143 * instance, adds action to the per-object, per-thread action vector and to the
2144 * action trace list of all thread actions.
2146 * @param act is the ModelAction to add.
2148 void ModelExecution::add_action_to_lists(ModelAction *act)
2150 int tid = id_to_int(act->get_tid());
2151 ModelAction *uninit = NULL;
2153 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
2154 if (list->empty() && act->is_atomic_var()) {
2155 uninit = get_uninitialized_action(act);
2156 uninit_id = id_to_int(uninit->get_tid());
2157 list->push_front(uninit);
2159 list->push_back(act);
2161 action_trace.push_back(act);
2163 action_trace.push_front(uninit);
2165 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
2166 if (tid >= (int)vec->size())
2167 vec->resize(priv->next_thread_id);
2168 (*vec)[tid].push_back(act);
2170 (*vec)[uninit_id].push_front(uninit);
2172 if ((int)thrd_last_action.size() <= tid)
2173 thrd_last_action.resize(get_num_threads());
2174 thrd_last_action[tid] = act;
2176 thrd_last_action[uninit_id] = uninit;
2178 if (act->is_fence() && act->is_release()) {
2179 if ((int)thrd_last_fence_release.size() <= tid)
2180 thrd_last_fence_release.resize(get_num_threads());
2181 thrd_last_fence_release[tid] = act;
2184 if (act->is_wait()) {
2185 void *mutex_loc = (void *) act->get_value();
2186 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
2188 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
2189 if (tid >= (int)vec->size())
2190 vec->resize(priv->next_thread_id);
2191 (*vec)[tid].push_back(act);
2196 * @brief Get the last action performed by a particular Thread
2197 * @param tid The thread ID of the Thread in question
2198 * @return The last action in the thread
2200 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
2202 int threadid = id_to_int(tid);
2203 if (threadid < (int)thrd_last_action.size())
2204 return thrd_last_action[id_to_int(tid)];
2210 * @brief Get the last fence release performed by a particular Thread
2211 * @param tid The thread ID of the Thread in question
2212 * @return The last fence release in the thread, if one exists; NULL otherwise
2214 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
2216 int threadid = id_to_int(tid);
2217 if (threadid < (int)thrd_last_fence_release.size())
2218 return thrd_last_fence_release[id_to_int(tid)];
2224 * Gets the last memory_order_seq_cst write (in the total global sequence)
2225 * performed on a particular object (i.e., memory location), not including the
2227 * @param curr The current ModelAction; also denotes the object location to
2229 * @return The last seq_cst write
2231 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
2233 void *location = curr->get_location();
2234 action_list_t *list = obj_map.get(location);
2235 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2236 action_list_t::reverse_iterator rit;
2237 for (rit = list->rbegin(); (*rit) != curr; rit++)
2239 rit++; /* Skip past curr */
2240 for ( ; rit != list->rend(); rit++)
2241 if ((*rit)->is_write() && (*rit)->is_seqcst())
2247 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2248 * performed in a particular thread, prior to a particular fence.
2249 * @param tid The ID of the thread to check
2250 * @param before_fence The fence from which to begin the search; if NULL, then
2251 * search for the most recent fence in the thread.
2252 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2254 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2256 /* All fences should have location FENCE_LOCATION */
2257 action_list_t *list = obj_map.get(FENCE_LOCATION);
2262 action_list_t::reverse_iterator rit = list->rbegin();
2265 for (; rit != list->rend(); rit++)
2266 if (*rit == before_fence)
2269 ASSERT(*rit == before_fence);
2273 for (; rit != list->rend(); rit++)
2274 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2280 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2281 * location). This function identifies the mutex according to the current
2282 * action, which is presumed to perform on the same mutex.
2283 * @param curr The current ModelAction; also denotes the object location to
2285 * @return The last unlock operation
2287 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
2289 void *location = curr->get_location();
2290 action_list_t *list = obj_map.get(location);
2291 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2292 action_list_t::reverse_iterator rit;
2293 for (rit = list->rbegin(); rit != list->rend(); rit++)
2294 if ((*rit)->is_unlock() || (*rit)->is_wait())
2299 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
2301 ModelAction *parent = get_last_action(tid);
2303 parent = get_thread(tid)->get_creation();
2308 * Returns the clock vector for a given thread.
2309 * @param tid The thread whose clock vector we want
2310 * @return Desired clock vector
2312 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
2314 return get_parent_action(tid)->get_cv();
2318 * @brief Find the promise (if any) to resolve for the current action and
2319 * remove it from the pending promise vector
2320 * @param curr The current ModelAction. Should be a write.
2321 * @return The Promise to resolve, if any; otherwise NULL
2323 Promise * ModelExecution::pop_promise_to_resolve(const ModelAction *curr)
2325 for (unsigned int i = 0; i < promises.size(); i++)
2326 if (curr->get_node()->get_promise(i)) {
2327 Promise *ret = promises[i];
2328 promises.erase(promises.begin() + i);
2335 * Resolve a Promise with a current write.
2336 * @param write The ModelAction that is fulfilling Promises
2337 * @param promise The Promise to resolve
2338 * @param work The work queue, for adding new fixup work
2339 * @return True if the Promise was successfully resolved; false otherwise
2341 bool ModelExecution::resolve_promise(ModelAction *write, Promise *promise,
2344 ModelVector<ModelAction *> actions_to_check;
2346 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2347 ModelAction *read = promise->get_reader(i);
2348 if (read_from(read, write)) {
2349 /* Propagate the changed clock vector */
2350 propagate_clockvector(read, work);
2352 actions_to_check.push_back(read);
2354 /* Make sure the promise's value matches the write's value */
2355 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2356 if (!mo_graph->resolvePromise(promise, write))
2357 priv->failed_promise = true;
2360 * @todo It is possible to end up in an inconsistent state, where a
2361 * "resolved" promise may still be referenced if
2362 * CycleGraph::resolvePromise() failed, so don't delete 'promise'.
2364 * Note that the inconsistency only matters when dumping mo_graph to
2370 //Check whether reading these writes has made threads unable to
2372 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2373 ModelAction *read = actions_to_check[i];
2374 mo_check_promises(read, true);
2381 * Compute the set of promises that could potentially be satisfied by this
2382 * action. Note that the set computation actually appears in the Node, not in
2384 * @param curr The ModelAction that may satisfy promises
2386 void ModelExecution::compute_promises(ModelAction *curr)
2388 for (unsigned int i = 0; i < promises.size(); i++) {
2389 Promise *promise = promises[i];
2390 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2393 bool satisfy = true;
2394 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2395 const ModelAction *act = promise->get_reader(j);
2396 if (act->happens_before(curr) ||
2397 act->could_synchronize_with(curr)) {
2403 curr->get_node()->set_promise(i);
2407 /** Checks promises in response to change in ClockVector Threads. */
2408 void ModelExecution::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2410 for (unsigned int i = 0; i < promises.size(); i++) {
2411 Promise *promise = promises[i];
2412 if (!promise->thread_is_available(tid))
2414 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2415 const ModelAction *act = promise->get_reader(j);
2416 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2417 merge_cv->synchronized_since(act)) {
2418 if (promise->eliminate_thread(tid)) {
2419 /* Promise has failed */
2420 priv->failed_promise = true;
2428 void ModelExecution::check_promises_thread_disabled()
2430 for (unsigned int i = 0; i < promises.size(); i++) {
2431 Promise *promise = promises[i];
2432 if (promise->has_failed()) {
2433 priv->failed_promise = true;
2440 * @brief Checks promises in response to addition to modification order for
2443 * We test whether threads are still available for satisfying promises after an
2444 * addition to our modification order constraints. Those that are unavailable
2445 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2446 * that promise has failed.
2448 * @param act The ModelAction which updated the modification order
2449 * @param is_read_check Should be true if act is a read and we must check for
2450 * updates to the store from which it read (there is a distinction here for
2451 * RMW's, which are both a load and a store)
2453 void ModelExecution::mo_check_promises(const ModelAction *act, bool is_read_check)
2455 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2457 for (unsigned int i = 0; i < promises.size(); i++) {
2458 Promise *promise = promises[i];
2460 // Is this promise on the same location?
2461 if (!promise->same_location(write))
2464 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2465 const ModelAction *pread = promise->get_reader(j);
2466 if (!pread->happens_before(act))
2468 if (mo_graph->checkPromise(write, promise)) {
2469 priv->failed_promise = true;
2475 // Don't do any lookups twice for the same thread
2476 if (!promise->thread_is_available(act->get_tid()))
2479 if (mo_graph->checkReachable(promise, write)) {
2480 if (mo_graph->checkPromise(write, promise)) {
2481 priv->failed_promise = true;
2489 * Compute the set of writes that may break the current pending release
2490 * sequence. This information is extracted from previou release sequence
2493 * @param curr The current ModelAction. Must be a release sequence fixup
2496 void ModelExecution::compute_relseq_breakwrites(ModelAction *curr)
2498 if (pending_rel_seqs.empty())
2501 struct release_seq *pending = pending_rel_seqs.back();
2502 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2503 const ModelAction *write = pending->writes[i];
2504 curr->get_node()->add_relseq_break(write);
2507 /* NULL means don't break the sequence; just synchronize */
2508 curr->get_node()->add_relseq_break(NULL);
2512 * Build up an initial set of all past writes that this 'read' action may read
2513 * from, as well as any previously-observed future values that must still be valid.
2515 * @param curr is the current ModelAction that we are exploring; it must be a
2518 void ModelExecution::build_may_read_from(ModelAction *curr)
2520 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
2522 ASSERT(curr->is_read());
2524 ModelAction *last_sc_write = NULL;
2526 if (curr->is_seqcst())
2527 last_sc_write = get_last_seq_cst_write(curr);
2529 /* Iterate over all threads */
2530 for (i = 0; i < thrd_lists->size(); i++) {
2531 /* Iterate over actions in thread, starting from most recent */
2532 action_list_t *list = &(*thrd_lists)[i];
2533 action_list_t::reverse_iterator rit;
2534 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2535 ModelAction *act = *rit;
2537 /* Only consider 'write' actions */
2538 if (!act->is_write() || act == curr)
2541 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2542 bool allow_read = true;
2544 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2546 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2550 /* Only add feasible reads */
2551 mo_graph->startChanges();
2552 r_modification_order(curr, act);
2553 if (!is_infeasible())
2554 curr->get_node()->add_read_from_past(act);
2555 mo_graph->rollbackChanges();
2558 /* Include at most one act per-thread that "happens before" curr */
2559 if (act->happens_before(curr))
2564 /* Inherit existing, promised future values */
2565 for (i = 0; i < promises.size(); i++) {
2566 const Promise *promise = promises[i];
2567 const ModelAction *promise_read = promise->get_reader(0);
2568 if (promise_read->same_var(curr)) {
2569 /* Only add feasible future-values */
2570 mo_graph->startChanges();
2571 r_modification_order(curr, promise);
2572 if (!is_infeasible())
2573 curr->get_node()->add_read_from_promise(promise_read);
2574 mo_graph->rollbackChanges();
2578 /* We may find no valid may-read-from only if the execution is doomed */
2579 if (!curr->get_node()->read_from_size()) {
2580 priv->no_valid_reads = true;
2584 if (DBG_ENABLED()) {
2585 model_print("Reached read action:\n");
2587 model_print("Printing read_from_past\n");
2588 curr->get_node()->print_read_from_past();
2589 model_print("End printing read_from_past\n");
2593 bool ModelExecution::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2595 for ( ; write != NULL; write = write->get_reads_from()) {
2596 /* UNINIT actions don't have a Node, and they never sleep */
2597 if (write->is_uninitialized())
2599 Node *prevnode = write->get_node()->get_parent();
2601 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2602 if (write->is_release() && thread_sleep)
2604 if (!write->is_rmw())
2611 * @brief Get an action representing an uninitialized atomic
2613 * This function may create a new one or try to retrieve one from the NodeStack
2615 * @param curr The current action, which prompts the creation of an UNINIT action
2616 * @return A pointer to the UNINIT ModelAction
2618 ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
2620 Node *node = curr->get_node();
2621 ModelAction *act = node->get_uninit_action();
2623 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
2624 node->set_uninit_action(act);
2626 act->create_cv(NULL);
2630 static void print_list(const action_list_t *list)
2632 action_list_t::const_iterator it;
2634 model_print("------------------------------------------------------------------------------------\n");
2635 model_print("# t Action type MO Location Value Rf CV\n");
2636 model_print("------------------------------------------------------------------------------------\n");
2638 unsigned int hash = 0;
2640 for (it = list->begin(); it != list->end(); it++) {
2641 const ModelAction *act = *it;
2642 if (act->get_seq_number() > 0)
2644 hash = hash^(hash<<3)^((*it)->hash());
2646 model_print("HASH %u\n", hash);
2647 model_print("------------------------------------------------------------------------------------\n");
2650 #if SUPPORT_MOD_ORDER_DUMP
2651 void ModelExecution::dumpGraph(char *filename) const
2654 sprintf(buffer, "%s.dot", filename);
2655 FILE *file = fopen(buffer, "w");
2656 fprintf(file, "digraph %s {\n", filename);
2657 mo_graph->dumpNodes(file);
2658 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2660 for (action_list_t::const_iterator it = action_trace.begin(); it != action_trace.end(); it++) {
2661 ModelAction *act = *it;
2662 if (act->is_read()) {
2663 mo_graph->dot_print_node(file, act);
2664 if (act->get_reads_from())
2665 mo_graph->dot_print_edge(file,
2666 act->get_reads_from(),
2668 "label=\"rf\", color=red, weight=2");
2670 mo_graph->dot_print_edge(file,
2671 act->get_reads_from_promise(),
2673 "label=\"rf\", color=red");
2675 if (thread_array[act->get_tid()]) {
2676 mo_graph->dot_print_edge(file,
2677 thread_array[id_to_int(act->get_tid())],
2679 "label=\"sb\", color=blue, weight=400");
2682 thread_array[act->get_tid()] = act;
2684 fprintf(file, "}\n");
2685 model_free(thread_array);
2690 /** @brief Prints an execution trace summary. */
2691 void ModelExecution::print_summary() const
2693 #if SUPPORT_MOD_ORDER_DUMP
2694 char buffername[100];
2695 sprintf(buffername, "exec%04u", get_execution_number());
2696 mo_graph->dumpGraphToFile(buffername);
2697 sprintf(buffername, "graph%04u", get_execution_number());
2698 dumpGraph(buffername);
2701 model_print("Execution trace %d:", get_execution_number());
2702 if (isfeasibleprefix()) {
2703 if (is_yieldblocked())
2704 model_print(" YIELD BLOCKED");
2705 if (scheduler->all_threads_sleeping())
2706 model_print(" SLEEP-SET REDUNDANT");
2707 if (have_bug_reports())
2708 model_print(" DETECTED BUG(S)");
2710 print_infeasibility(" INFEASIBLE");
2713 print_list(&action_trace);
2716 if (!promises.empty()) {
2717 model_print("Pending promises:\n");
2718 for (unsigned int i = 0; i < promises.size(); i++) {
2719 model_print(" [P%u] ", i);
2720 promises[i]->print();
2727 * Add a Thread to the system for the first time. Should only be called once
2729 * @param t The Thread to add
2731 void ModelExecution::add_thread(Thread *t)
2733 unsigned int i = id_to_int(t->get_id());
2734 if (i >= thread_map.size())
2735 thread_map.resize(i + 1);
2737 if (!t->is_model_thread())
2738 scheduler->add_thread(t);
2742 * @brief Get a Thread reference by its ID
2743 * @param tid The Thread's ID
2744 * @return A Thread reference
2746 Thread * ModelExecution::get_thread(thread_id_t tid) const
2748 unsigned int i = id_to_int(tid);
2749 if (i < thread_map.size())
2750 return thread_map[i];
2755 * @brief Get a reference to the Thread in which a ModelAction was executed
2756 * @param act The ModelAction
2757 * @return A Thread reference
2759 Thread * ModelExecution::get_thread(const ModelAction *act) const
2761 return get_thread(act->get_tid());
2765 * @brief Get a Promise's "promise number"
2767 * A "promise number" is an index number that is unique to a promise, valid
2768 * only for a specific snapshot of an execution trace. Promises may come and go
2769 * as they are generated an resolved, so an index only retains meaning for the
2772 * @param promise The Promise to check
2773 * @return The promise index, if the promise still is valid; otherwise -1
2775 int ModelExecution::get_promise_number(const Promise *promise) const
2777 for (unsigned int i = 0; i < promises.size(); i++)
2778 if (promises[i] == promise)
2785 * @brief Check if a Thread is currently enabled
2786 * @param t The Thread to check
2787 * @return True if the Thread is currently enabled
2789 bool ModelExecution::is_enabled(Thread *t) const
2791 return scheduler->is_enabled(t);
2795 * @brief Check if a Thread is currently enabled
2796 * @param tid The ID of the Thread to check
2797 * @return True if the Thread is currently enabled
2799 bool ModelExecution::is_enabled(thread_id_t tid) const
2801 return scheduler->is_enabled(tid);
2805 * @brief Select the next thread to execute based on the curren action
2807 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
2808 * actions should be followed by the execution of their child thread. In either
2809 * case, the current action should determine the next thread schedule.
2811 * @param curr The current action
2812 * @return The next thread to run, if the current action will determine this
2813 * selection; otherwise NULL
2815 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
2817 /* Do not split atomic RMW */
2818 if (curr->is_rmwr())
2819 return get_thread(curr);
2820 /* Follow CREATE with the created thread */
2821 if (curr->get_type() == THREAD_CREATE)
2822 return curr->get_thread_operand();
2826 /** @return True if the execution has taken too many steps */
2827 bool ModelExecution::too_many_steps() const
2829 return params->bound != 0 && priv->used_sequence_numbers > params->bound;
2833 * Takes the next step in the execution, if possible.
2834 * @param curr The current step to take
2835 * @return Returns the next Thread to run, if any; NULL if this execution
2838 Thread * ModelExecution::take_step(ModelAction *curr)
2840 Thread *curr_thrd = get_thread(curr);
2841 ASSERT(curr_thrd->get_state() == THREAD_READY);
2843 ASSERT(check_action_enabled(curr)); /* May have side effects? */
2844 curr = check_current_action(curr);
2847 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2848 scheduler->remove_thread(curr_thrd);
2850 return action_select_next_thread(curr);
2854 * Launch end-of-execution release sequence fixups only when
2855 * the execution is otherwise feasible AND there are:
2857 * (1) pending release sequences
2858 * (2) pending assertions that could be invalidated by a change
2859 * in clock vectors (i.e., data races)
2860 * (3) no pending promises
2862 void ModelExecution::fixup_release_sequences()
2864 while (!pending_rel_seqs.empty() &&
2865 is_feasible_prefix_ignore_relseq() &&
2866 haveUnrealizedRaces()) {
2867 model_print("*** WARNING: release sequence fixup action "
2868 "(%zu pending release seuqence(s)) ***\n",
2869 pending_rel_seqs.size());
2870 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2871 std::memory_order_seq_cst, NULL, VALUE_NONE,