12 #include "clockvector.h"
13 #include "cyclegraph.h"
15 #include "threads-model.h"
16 #include "bugmessage.h"
18 #define INITIAL_THREAD_ID 0
21 * Structure for holding small ModelChecker members that should be snapshotted
23 struct model_snapshot_members {
24 model_snapshot_members() :
25 /* First thread created will have id INITIAL_THREAD_ID */
26 next_thread_id(INITIAL_THREAD_ID),
27 used_sequence_numbers(0),
30 failed_promise(false),
31 hard_failed_promise(false),
32 too_many_reads(false),
33 no_valid_reads(false),
34 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;
50 bool hard_failed_promise;
53 /** @brief Incorrectly-ordered synchronization was made */
54 bool bad_synchronization;
61 /** @brief Constructor */
62 ModelExecution::ModelExecution(ModelChecker *m,
63 const struct model_params *params,
65 NodeStack *node_stack) :
70 thread_map(2), /* We'll always need at least 2 threads */
74 condvar_waiters_map(),
81 thrd_last_fence_release(),
82 node_stack(node_stack),
83 priv(new struct model_snapshot_members()),
84 mo_graph(new CycleGraph())
86 /* Initialize a model-checker thread, for special ModelActions */
87 model_thread = new Thread(get_next_id()); // L: Create model thread
88 add_thread(model_thread); // L: Add model thread to scheduler
89 scheduler->register_engine(this);
90 node_stack->register_engine(this);
93 /** @brief Destructor */
94 ModelExecution::~ModelExecution()
96 for (unsigned int i = 0; i < get_num_threads(); i++)
97 delete get_thread(int_to_id(i));
99 for (unsigned int i = 0; i < promises.size(); i++)
106 int ModelExecution::get_execution_number() const
108 return model->get_execution_number();
111 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
113 action_list_t *tmp = hash->get(ptr);
115 tmp = new action_list_t();
121 static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
123 SnapVector<action_list_t> *tmp = hash->get(ptr);
125 tmp = new SnapVector<action_list_t>();
131 action_list_t * ModelExecution::get_actions_on_obj(void * obj, thread_id_t tid) const
133 SnapVector<action_list_t> *wrv = obj_thrd_map.get(obj);
136 unsigned int thread=id_to_int(tid);
137 if (thread < wrv->size())
138 return &(*wrv)[thread];
143 /** @return a thread ID for a new Thread */
144 thread_id_t ModelExecution::get_next_id()
146 return priv->next_thread_id++;
149 /** @return the number of user threads created during this execution */
150 unsigned int ModelExecution::get_num_threads() const
152 return priv->next_thread_id;
155 /** @return a sequence number for a new ModelAction */
156 modelclock_t ModelExecution::get_next_seq_num()
158 return ++priv->used_sequence_numbers;
162 * @brief Should the current action wake up a given thread?
164 * @param curr The current action
165 * @param thread The thread that we might wake up
166 * @return True, if we should wake up the sleeping thread; false otherwise
168 bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
170 const ModelAction *asleep = thread->get_pending();
171 /* Don't allow partial RMW to wake anyone up */
174 /* Synchronizing actions may have been backtracked */
175 if (asleep->could_synchronize_with(curr))
177 /* All acquire/release fences and fence-acquire/store-release */
178 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
180 /* Fence-release + store can awake load-acquire on the same location */
181 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
182 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
183 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
189 void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
191 for (unsigned int i = 0; i < get_num_threads(); i++) {
192 Thread *thr = get_thread(int_to_id(i));
193 if (scheduler->is_sleep_set(thr)) {
194 if (should_wake_up(curr, thr))
195 /* Remove this thread from sleep set */
196 scheduler->remove_sleep(thr);
201 /** @brief Alert the model-checker that an incorrectly-ordered
202 * synchronization was made */
203 void ModelExecution::set_bad_synchronization()
205 priv->bad_synchronization = true;
208 /** @brief Alert the model-checker that an incorrectly-ordered
209 * synchronization was made */
210 void ModelExecution::set_bad_sc_read()
212 priv->bad_sc_read = true;
215 bool ModelExecution::assert_bug(const char *msg)
217 priv->bugs.push_back(new bug_message(msg));
219 if (isfeasibleprefix()) {
226 /** @return True, if any bugs have been reported for this execution */
227 bool ModelExecution::have_bug_reports() const
229 return priv->bugs.size() != 0;
232 SnapVector<bug_message *> * ModelExecution::get_bugs() const
238 * Check whether the current trace has triggered an assertion which should halt
241 * @return True, if the execution should be aborted; false otherwise
243 bool ModelExecution::has_asserted() const
245 return priv->asserted;
249 * Trigger a trace assertion which should cause this execution to be halted.
250 * This can be due to a detected bug or due to an infeasibility that should
253 void ModelExecution::set_assert()
255 priv->asserted = true;
259 * Check if we are in a deadlock. Should only be called at the end of an
260 * execution, although it should not give false positives in the middle of an
261 * execution (there should be some ENABLED thread).
263 * @return True if program is in a deadlock; false otherwise
265 bool ModelExecution::is_deadlocked() const
267 bool blocking_threads = false;
268 for (unsigned int i = 0; i < get_num_threads(); i++) {
269 thread_id_t tid = int_to_id(i);
272 Thread *t = get_thread(tid);
273 if (!t->is_model_thread() && t->get_pending())
274 blocking_threads = true;
276 return blocking_threads;
280 * @brief Check if we are yield-blocked
282 * A program can be "yield-blocked" if all threads are ready to execute a
285 * @return True if the program is yield-blocked; false otherwise
287 bool ModelExecution::is_yieldblocked() const
289 if (!params->yieldblock)
292 for (unsigned int i = 0; i < get_num_threads(); i++) {
293 thread_id_t tid = int_to_id(i);
294 Thread *t = get_thread(tid);
295 if (t->get_pending() && t->get_pending()->is_yield())
302 * Check if this is a complete execution. That is, have all thread completed
303 * execution (rather than exiting because sleep sets have forced a redundant
306 * @return True if the execution is complete.
308 bool ModelExecution::is_complete_execution() const
310 if (is_yieldblocked())
312 for (unsigned int i = 0; i < get_num_threads(); i++)
313 if (is_enabled(int_to_id(i)))
319 * @brief Find the last fence-related backtracking conflict for a ModelAction
321 * This function performs the search for the most recent conflicting action
322 * against which we should perform backtracking, as affected by fence
323 * operations. This includes pairs of potentially-synchronizing actions which
324 * occur due to fence-acquire or fence-release, and hence should be explored in
325 * the opposite execution order.
327 * @param act The current action
328 * @return The most recent action which conflicts with act due to fences
330 ModelAction * ModelExecution::get_last_fence_conflict(ModelAction *act) const
332 /* Only perform release/acquire fence backtracking for stores */
333 if (!act->is_write())
336 /* Find a fence-release (or, act is a release) */
337 ModelAction *last_release;
338 if (act->is_release())
341 last_release = get_last_fence_release(act->get_tid());
345 /* Skip past the release */
346 const action_list_t *list = &action_trace;
347 action_list_t::const_reverse_iterator rit;
348 for (rit = list->rbegin(); rit != list->rend(); rit++)
349 if (*rit == last_release)
351 ASSERT(rit != list->rend());
356 * load --sb-> fence-acquire */
357 ModelVector<ModelAction *> acquire_fences(get_num_threads(), NULL);
358 ModelVector<ModelAction *> prior_loads(get_num_threads(), NULL);
359 bool found_acquire_fences = false;
360 for ( ; rit != list->rend(); rit++) {
361 ModelAction *prev = *rit;
362 if (act->same_thread(prev))
365 int tid = id_to_int(prev->get_tid());
367 if (prev->is_read() && act->same_var(prev)) {
368 if (prev->is_acquire()) {
369 /* Found most recent load-acquire, don't need
370 * to search for more fences */
371 if (!found_acquire_fences)
374 prior_loads[tid] = prev;
377 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
378 found_acquire_fences = true;
379 acquire_fences[tid] = prev;
383 ModelAction *latest_backtrack = NULL;
384 for (unsigned int i = 0; i < acquire_fences.size(); i++)
385 if (acquire_fences[i] && prior_loads[i])
386 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
387 latest_backtrack = acquire_fences[i];
388 return latest_backtrack;
392 * @brief Find the last backtracking conflict for a ModelAction
394 * This function performs the search for the most recent conflicting action
395 * against which we should perform backtracking. This primary includes pairs of
396 * synchronizing actions which should be explored in the opposite execution
399 * @param act The current action
400 * @return The most recent action which conflicts with act
402 ModelAction * ModelExecution::get_last_conflict(ModelAction *act) const
404 switch (act->get_type()) {
406 /* Only seq-cst fences can (directly) cause backtracking */
407 if (!act->is_seqcst())
412 ModelAction *ret = NULL;
414 /* linear search: from most recent to oldest */
415 action_list_t *list = obj_map.get(act->get_location());
416 action_list_t::reverse_iterator rit;
417 for (rit = list->rbegin(); rit != list->rend(); rit++) {
418 ModelAction *prev = *rit;
421 if (prev->could_synchronize_with(act)) {
427 ModelAction *ret2 = get_last_fence_conflict(act);
437 case ATOMIC_TRYLOCK: {
438 /* linear search: from most recent to oldest */
439 action_list_t *list = obj_map.get(act->get_location());
440 action_list_t::reverse_iterator rit;
441 for (rit = list->rbegin(); rit != list->rend(); rit++) {
442 ModelAction *prev = *rit;
443 if (act->is_conflicting_lock(prev))
448 case ATOMIC_UNLOCK: {
449 /* linear search: from most recent to oldest */
450 action_list_t *list = obj_map.get(act->get_location());
451 action_list_t::reverse_iterator rit;
452 for (rit = list->rbegin(); rit != list->rend(); rit++) {
453 ModelAction *prev = *rit;
454 if (!act->same_thread(prev) && prev->is_failed_trylock())
460 /* linear search: from most recent to oldest */
461 action_list_t *list = obj_map.get(act->get_location());
462 action_list_t::reverse_iterator rit;
463 for (rit = list->rbegin(); rit != list->rend(); rit++) {
464 ModelAction *prev = *rit;
465 if (!act->same_thread(prev) && prev->is_failed_trylock())
467 if (!act->same_thread(prev) && prev->is_notify())
473 case ATOMIC_NOTIFY_ALL:
474 case ATOMIC_NOTIFY_ONE: {
475 /* linear search: from most recent to oldest */
476 action_list_t *list = obj_map.get(act->get_location());
477 action_list_t::reverse_iterator rit;
478 for (rit = list->rbegin(); rit != list->rend(); rit++) {
479 ModelAction *prev = *rit;
480 if (!act->same_thread(prev) && prev->is_wait())
491 /** This method finds backtracking points where we should try to
492 * reorder the parameter ModelAction against.
494 * @param the ModelAction to find backtracking points for.
496 void ModelExecution::set_backtracking(ModelAction *act)
498 Thread *t = get_thread(act);
499 ModelAction *prev = get_last_conflict(act);
503 Node *node = prev->get_node()->get_parent();
505 /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
506 int low_tid, high_tid;
507 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
508 low_tid = id_to_int(act->get_tid());
509 high_tid = low_tid + 1;
512 high_tid = get_num_threads();
515 for (int i = low_tid; i < high_tid; i++) {
516 thread_id_t tid = int_to_id(i);
518 /* Make sure this thread can be enabled here. */
519 if (i >= node->get_num_threads())
522 /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
523 /* Don't backtrack into a point where the thread is disabled or sleeping. */
524 if (node->enabled_status(tid) != THREAD_ENABLED)
527 /* Check if this has been explored already */
528 if (node->has_been_explored(tid))
531 /* See if fairness allows */
532 if (params->fairwindow != 0 && !node->has_priority(tid)) {
534 for (int t = 0; t < node->get_num_threads(); t++) {
535 thread_id_t tother = int_to_id(t);
536 if (node->is_enabled(tother) && node->has_priority(tother)) {
545 /* See if CHESS-like yield fairness allows */
546 if (params->yieldon) {
548 for (int t = 0; t < node->get_num_threads(); t++) {
549 thread_id_t tother = int_to_id(t);
550 if (node->is_enabled(tother) && node->has_priority_over(tid, tother)) {
559 /* Cache the latest backtracking point */
560 set_latest_backtrack(prev);
562 /* If this is a new backtracking point, mark the tree */
563 if (!node->set_backtrack(tid))
565 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
566 id_to_int(prev->get_tid()),
567 id_to_int(t->get_id()));
576 * @brief Cache the a backtracking point as the "most recent", if eligible
578 * Note that this does not prepare the NodeStack for this backtracking
579 * operation, it only caches the action on a per-execution basis
581 * @param act The operation at which we should explore a different next action
582 * (i.e., backtracking point)
583 * @return True, if this action is now the most recent backtracking point;
586 bool ModelExecution::set_latest_backtrack(ModelAction *act)
588 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
589 priv->next_backtrack = act;
596 * Returns last backtracking point. The model checker will explore a different
597 * path for this point in the next execution.
598 * @return The ModelAction at which the next execution should diverge.
600 ModelAction * ModelExecution::get_next_backtrack()
602 ModelAction *next = priv->next_backtrack;
603 priv->next_backtrack = NULL;
608 * Processes a read model action.
609 * @param curr is the read model action to process.
610 * @return True if processing this read updates the mo_graph.
612 bool ModelExecution::process_read(ModelAction *curr)
614 Node *node = curr->get_node();
616 bool updated = false;
617 switch (node->get_read_from_status()) {
618 case READ_FROM_PAST: {
619 const ModelAction *rf = node->get_read_from_past();
622 mo_graph->startChanges();
624 ASSERT(!is_infeasible());
625 if (!check_recency(curr, rf)) {
626 if (node->increment_read_from()) {
627 mo_graph->rollbackChanges();
630 priv->too_many_reads = true;
634 updated = r_modification_order(curr, rf);
636 mo_graph->commitChanges();
637 mo_check_promises(curr, true);
640 case READ_FROM_PROMISE: {
641 Promise *promise = curr->get_node()->get_read_from_promise();
642 if (promise->add_reader(curr))
643 priv->failed_promise = true;
644 curr->set_read_from_promise(promise);
645 mo_graph->startChanges();
646 if (!check_recency(curr, promise))
647 priv->too_many_reads = true;
648 updated = r_modification_order(curr, promise);
649 mo_graph->commitChanges();
652 case READ_FROM_FUTURE: {
653 /* Read from future value */
654 struct future_value fv = node->get_future_value();
655 Promise *promise = new Promise(this, curr, fv);
656 curr->set_read_from_promise(promise);
657 promises.push_back(promise);
658 mo_graph->startChanges();
659 updated = r_modification_order(curr, promise);
660 mo_graph->commitChanges();
666 get_thread(curr)->set_return_value(curr->get_return_value());
672 * Processes a lock, trylock, or unlock model action. @param curr is
673 * the read model action to process.
675 * The try lock operation checks whether the lock is taken. If not,
676 * it falls to the normal lock operation case. If so, it returns
679 * The lock operation has already been checked that it is enabled, so
680 * it just grabs the lock and synchronizes with the previous unlock.
682 * The unlock operation has to re-enable all of the threads that are
683 * waiting on the lock.
685 * @return True if synchronization was updated; false otherwise
687 bool ModelExecution::process_mutex(ModelAction *curr)
689 cdsc::mutex *mutex = curr->get_mutex();
690 struct cdsc::mutex_state *state = NULL;
693 state = mutex->get_state();
695 switch (curr->get_type()) {
696 case ATOMIC_TRYLOCK: {
697 bool success = !state->locked;
698 curr->set_try_lock(success);
700 get_thread(curr)->set_return_value(0);
703 get_thread(curr)->set_return_value(1);
705 //otherwise fall into the lock case
707 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
708 assert_bug("Lock access before initialization");
709 state->locked = get_thread(curr);
710 ModelAction *unlock = get_last_unlock(curr);
711 //synchronize with the previous unlock statement
712 if (unlock != NULL) {
713 synchronize(unlock, curr);
719 case ATOMIC_UNLOCK: {
720 /* wake up the other threads */
721 for (unsigned int i = 0; i < get_num_threads(); i++) {
722 Thread *t = get_thread(int_to_id(i));
723 Thread *curr_thrd = get_thread(curr);
724 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
728 /* unlock the lock - after checking who was waiting on it */
729 state->locked = NULL;
731 if (!curr->is_wait())
732 break; /* The rest is only for ATOMIC_WAIT */
734 /* Should we go to sleep? (simulate spurious failures) */
735 if (curr->get_node()->get_misc() == 0) {
736 get_safe_ptr_action(&condvar_waiters_map, curr->get_location())->push_back(curr);
738 scheduler->sleep(get_thread(curr));
742 case ATOMIC_NOTIFY_ALL: {
743 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
744 //activate all the waiting threads
745 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
746 scheduler->wake(get_thread(*rit));
751 case ATOMIC_NOTIFY_ONE: {
752 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
753 int wakeupthread = curr->get_node()->get_misc();
754 action_list_t::iterator it = waiters->begin();
757 if (it == waiters->end())
760 advance(it, wakeupthread);
761 scheduler->wake(get_thread(*it));
773 * @brief Check if the current pending promises allow a future value to be sent
775 * It is unsafe to pass a future value back if there exists a pending promise Pr
778 * reader --exec-> Pr --exec-> writer
780 * If such Pr exists, we must save the pending future value until Pr is
783 * @param writer The operation which sends the future value. Must be a write.
784 * @param reader The operation which will observe the value. Must be a read.
785 * @return True if the future value can be sent now; false if it must wait.
787 bool ModelExecution::promises_may_allow(const ModelAction *writer,
788 const ModelAction *reader) const
790 for (int i = promises.size() - 1; i >= 0; i--) {
791 ModelAction *pr = promises[i]->get_reader(0);
792 //reader is after promise...doesn't cross any promise
795 //writer is after promise, reader before...bad...
803 * @brief Add a future value to a reader
805 * This function performs a few additional checks to ensure that the future
806 * value can be feasibly observed by the reader
808 * @param writer The operation whose value is sent. Must be a write.
809 * @param reader The read operation which may read the future value. Must be a read.
811 void ModelExecution::add_future_value(const ModelAction *writer, ModelAction *reader)
813 /* Do more ambitious checks now that mo is more complete */
814 if (!mo_may_allow(writer, reader))
817 Node *node = reader->get_node();
819 /* Find an ancestor thread which exists at the time of the reader */
820 Thread *write_thread = get_thread(writer);
821 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
822 write_thread = write_thread->get_parent();
824 struct future_value fv = {
825 writer->get_write_value(),
826 writer->get_seq_number() + params->maxfuturedelay,
827 write_thread->get_id(),
829 if (node->add_future_value(fv))
830 set_latest_backtrack(reader);
834 * Process a write ModelAction
835 * @param curr The ModelAction to process
836 * @param work The work queue, for adding fixup work
837 * @return True if the mo_graph was updated or promises were resolved
839 bool ModelExecution::process_write(ModelAction *curr, work_queue_t *work)
841 /* Readers to which we may send our future value */
842 ModelVector<ModelAction *> send_fv;
844 const ModelAction *earliest_promise_reader;
845 bool updated_promises = false;
847 bool updated_mod_order = w_modification_order(curr, &send_fv);
848 Promise *promise = pop_promise_to_resolve(curr);
851 earliest_promise_reader = promise->get_reader(0);
852 updated_promises = resolve_promise(curr, promise, work);
854 earliest_promise_reader = NULL;
856 for (unsigned int i = 0; i < send_fv.size(); i++) {
857 ModelAction *read = send_fv[i];
859 /* Don't send future values to reads after the Promise we resolve */
860 if (!earliest_promise_reader || *read < *earliest_promise_reader) {
861 /* Check if future value can be sent immediately */
862 if (promises_may_allow(curr, read)) {
863 add_future_value(curr, read);
865 futurevalues.push_back(PendingFutureValue(curr, read));
870 /* Check the pending future values */
871 for (int i = (int)futurevalues.size() - 1; i >= 0; i--) {
872 struct PendingFutureValue pfv = futurevalues[i];
873 if (promises_may_allow(pfv.writer, pfv.reader)) {
874 add_future_value(pfv.writer, pfv.reader);
875 futurevalues.erase(futurevalues.begin() + i);
879 mo_graph->commitChanges();
880 mo_check_promises(curr, false);
882 get_thread(curr)->set_return_value(VALUE_NONE);
883 return updated_mod_order || updated_promises;
887 * Process a fence ModelAction
888 * @param curr The ModelAction to process
889 * @return True if synchronization was updated
891 bool ModelExecution::process_fence(ModelAction *curr)
894 * fence-relaxed: no-op
895 * fence-release: only log the occurence (not in this function), for
896 * use in later synchronization
897 * fence-acquire (this function): search for hypothetical release
899 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
901 bool updated = false;
902 if (curr->is_acquire()) {
903 action_list_t *list = &action_trace;
904 action_list_t::reverse_iterator rit;
905 /* Find X : is_read(X) && X --sb-> curr */
906 for (rit = list->rbegin(); rit != list->rend(); rit++) {
907 ModelAction *act = *rit;
910 if (act->get_tid() != curr->get_tid())
912 /* Stop at the beginning of the thread */
913 if (act->is_thread_start())
915 /* Stop once we reach a prior fence-acquire */
916 if (act->is_fence() && act->is_acquire())
920 /* read-acquire will find its own release sequences */
921 if (act->is_acquire())
924 /* Establish hypothetical release sequences */
925 rel_heads_list_t release_heads;
926 get_release_seq_heads(curr, act, &release_heads);
927 for (unsigned int i = 0; i < release_heads.size(); i++)
928 synchronize(release_heads[i], curr);
929 if (release_heads.size() != 0)
937 * @brief Process the current action for thread-related activity
939 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
940 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
941 * synchronization, etc. This function is a no-op for non-THREAD actions
942 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
944 * @param curr The current action
945 * @return True if synchronization was updated or a thread completed
947 bool ModelExecution::process_thread_action(ModelAction *curr)
949 bool updated = false;
951 switch (curr->get_type()) {
952 case THREAD_CREATE: {
953 thrd_t *thrd = (thrd_t *)curr->get_location();
954 struct thread_params *params = (struct thread_params *)curr->get_value();
955 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
956 curr->set_thread_operand(th);
958 th->set_creation(curr);
959 /* Promises can be satisfied by children */
960 for (unsigned int i = 0; i < promises.size(); i++) {
961 Promise *promise = promises[i];
962 if (promise->thread_is_available(curr->get_tid()))
963 promise->add_thread(th->get_id());
967 case PTHREAD_CREATE: {
968 (*(pthread_t *)curr->get_location()) = pthread_counter++;
970 struct pthread_params *params = (struct pthread_params *)curr->get_value();
971 Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
972 curr->set_thread_operand(th);
974 th->set_creation(curr);
976 if ( pthread_map.size() < pthread_counter )
977 pthread_map.resize( pthread_counter );
978 pthread_map[ pthread_counter-1 ] = th;
980 /* Promises can be satisfied by children */
981 for (unsigned int i = 0; i < promises.size(); i++) {
982 Promise *promise = promises[i];
983 if (promise->thread_is_available(curr->get_tid()))
984 promise->add_thread(th->get_id());
990 Thread *blocking = curr->get_thread_operand();
991 ModelAction *act = get_last_action(blocking->get_id());
992 synchronize(act, curr);
993 updated = true; /* trigger rel-seq checks */
997 Thread *blocking = curr->get_thread_operand();
998 ModelAction *act = get_last_action(blocking->get_id());
999 synchronize(act, curr);
1000 updated = true; /* trigger rel-seq checks */
1001 break; // WL: to be add (modified)
1004 case THREAD_FINISH: {
1005 Thread *th = get_thread(curr);
1006 /* Wake up any joining threads */
1007 for (unsigned int i = 0; i < get_num_threads(); i++) {
1008 Thread *waiting = get_thread(int_to_id(i));
1009 if (waiting->waiting_on() == th &&
1010 waiting->get_pending()->is_thread_join())
1011 scheduler->wake(waiting);
1014 /* Completed thread can't satisfy promises */
1015 for (unsigned int i = 0; i < promises.size(); i++) {
1016 Promise *promise = promises[i];
1017 if (promise->thread_is_available(th->get_id()))
1018 if (promise->eliminate_thread(th->get_id()))
1019 priv->failed_promise = true;
1021 updated = true; /* trigger rel-seq checks */
1024 case THREAD_START: {
1025 check_promises(curr->get_tid(), NULL, curr->get_cv());
1036 * @brief Process the current action for release sequence fixup activity
1038 * Performs model-checker release sequence fixups for the current action,
1039 * forcing a single pending release sequence to break (with a given, potential
1040 * "loose" write) or to complete (i.e., synchronize). If a pending release
1041 * sequence forms a complete release sequence, then we must perform the fixup
1042 * synchronization, mo_graph additions, etc.
1044 * @param curr The current action; must be a release sequence fixup action
1045 * @param work_queue The work queue to which to add work items as they are
1048 void ModelExecution::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1050 const ModelAction *write = curr->get_node()->get_relseq_break();
1051 struct release_seq *sequence = pending_rel_seqs.back();
1052 pending_rel_seqs.pop_back();
1054 ModelAction *acquire = sequence->acquire;
1055 const ModelAction *rf = sequence->rf;
1056 const ModelAction *release = sequence->release;
1060 ASSERT(release->same_thread(rf));
1062 if (write == NULL) {
1064 * @todo Forcing a synchronization requires that we set
1065 * modification order constraints. For instance, we can't allow
1066 * a fixup sequence in which two separate read-acquire
1067 * operations read from the same sequence, where the first one
1068 * synchronizes and the other doesn't. Essentially, we can't
1069 * allow any writes to insert themselves between 'release' and
1073 /* Must synchronize */
1074 if (!synchronize(release, acquire))
1077 /* Propagate the changed clock vector */
1078 propagate_clockvector(acquire, work_queue);
1080 /* Break release sequence with new edges:
1081 * release --mo--> write --mo--> rf */
1082 mo_graph->addEdge(release, write);
1083 mo_graph->addEdge(write, rf);
1086 /* See if we have realized a data race */
1091 * Initialize the current action by performing one or more of the following
1092 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1093 * in the NodeStack, manipulating backtracking sets, allocating and
1094 * initializing clock vectors, and computing the promises to fulfill.
1096 * @param curr The current action, as passed from the user context; may be
1097 * freed/invalidated after the execution of this function, with a different
1098 * action "returned" its place (pass-by-reference)
1099 * @return True if curr is a newly-explored action; false otherwise
1101 bool ModelExecution::initialize_curr_action(ModelAction **curr)
1103 ModelAction *newcurr;
1105 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1106 newcurr = process_rmw(*curr);
1109 if (newcurr->is_rmw())
1110 compute_promises(newcurr);
1116 (*curr)->set_seq_number(get_next_seq_num());
1118 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1120 /* First restore type and order in case of RMW operation */
1121 if ((*curr)->is_rmwr())
1122 newcurr->copy_typeandorder(*curr);
1124 ASSERT((*curr)->get_location() == newcurr->get_location());
1125 newcurr->copy_from_new(*curr);
1127 /* Discard duplicate ModelAction; use action from NodeStack */
1130 /* Always compute new clock vector */
1131 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1134 return false; /* Action was explored previously */
1138 /* Always compute new clock vector */
1139 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1141 /* Assign most recent release fence */
1142 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1145 * Perform one-time actions when pushing new ModelAction onto
1148 if (newcurr->is_write())
1149 compute_promises(newcurr);
1150 else if (newcurr->is_relseq_fixup())
1151 compute_relseq_breakwrites(newcurr);
1152 else if (newcurr->is_wait())
1153 newcurr->get_node()->set_misc_max(2);
1154 else if (newcurr->is_notify_one()) {
1155 newcurr->get_node()->set_misc_max(get_safe_ptr_action(&condvar_waiters_map, newcurr->get_location())->size());
1157 return true; /* This was a new ModelAction */
1162 * @brief Establish reads-from relation between two actions
1164 * Perform basic operations involved with establishing a concrete rf relation,
1165 * including setting the ModelAction data and checking for release sequences.
1167 * @param act The action that is reading (must be a read)
1168 * @param rf The action from which we are reading (must be a write)
1170 * @return True if this read established synchronization
1173 bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
1176 ASSERT(rf->is_write());
1178 act->set_read_from(rf);
1179 if (act->is_acquire()) {
1180 rel_heads_list_t release_heads;
1181 get_release_seq_heads(act, act, &release_heads);
1182 int num_heads = release_heads.size();
1183 for (unsigned int i = 0; i < release_heads.size(); i++)
1184 if (!synchronize(release_heads[i], act))
1186 return num_heads > 0;
1192 * @brief Synchronizes two actions
1194 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
1195 * This function performs the synchronization as well as providing other hooks
1196 * for other checks along with synchronization.
1198 * @param first The left-hand side of the synchronizes-with relation
1199 * @param second The right-hand side of the synchronizes-with relation
1200 * @return True if the synchronization was successful (i.e., was consistent
1201 * with the execution order); false otherwise
1203 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
1205 if (*second < *first) {
1206 set_bad_synchronization();
1209 check_promises(first->get_tid(), second->get_cv(), first->get_cv());
1210 return second->synchronize_with(first);
1214 * Check promises and eliminate potentially-satisfying threads when a thread is
1215 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1216 * no longer satisfy a promise generated from that thread.
1218 * @param blocker The thread on which a thread is waiting
1219 * @param waiting The waiting thread
1221 void ModelExecution::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1223 for (unsigned int i = 0; i < promises.size(); i++) {
1224 Promise *promise = promises[i];
1225 if (!promise->thread_is_available(waiting->get_id()))
1227 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1228 ModelAction *reader = promise->get_reader(j);
1229 if (reader->get_tid() != blocker->get_id())
1231 if (promise->eliminate_thread(waiting->get_id())) {
1232 /* Promise has failed */
1233 priv->failed_promise = true;
1235 /* Only eliminate the 'waiting' thread once */
1243 * @brief Check whether a model action is enabled.
1245 * Checks whether an operation would be successful (i.e., is a lock already
1246 * locked, or is the joined thread already complete).
1248 * For yield-blocking, yields are never enabled.
1250 * @param curr is the ModelAction to check whether it is enabled.
1251 * @return a bool that indicates whether the action is enabled.
1253 bool ModelExecution::check_action_enabled(ModelAction *curr) {
1254 if (curr->is_lock()) {
1255 cdsc::mutex *lock = curr->get_mutex();
1256 struct cdsc::mutex_state *state = lock->get_state();
1259 } else if (curr->is_thread_join()) {
1260 Thread *blocking = curr->get_thread_operand();
1261 if (!blocking->is_complete()) {
1262 thread_blocking_check_promises(blocking, get_thread(curr));
1265 } else if (params->yieldblock && curr->is_yield()) {
1273 * This is the heart of the model checker routine. It performs model-checking
1274 * actions corresponding to a given "current action." Among other processes, it
1275 * calculates reads-from relationships, updates synchronization clock vectors,
1276 * forms a memory_order constraints graph, and handles replay/backtrack
1277 * execution when running permutations of previously-observed executions.
1279 * @param curr The current action to process
1280 * @return The ModelAction that is actually executed; may be different than
1283 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
1286 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1287 bool newly_explored = initialize_curr_action(&curr);
1291 wake_up_sleeping_actions(curr);
1293 /* Compute fairness information for CHESS yield algorithm */
1294 if (params->yieldon) {
1295 curr->get_node()->update_yield(scheduler);
1298 /* Add the action to lists before any other model-checking tasks */
1299 if (!second_part_of_rmw)
1300 add_action_to_lists(curr);
1302 /* Build may_read_from set for newly-created actions */
1303 if (newly_explored && curr->is_read())
1304 build_may_read_from(curr);
1306 /* Initialize work_queue with the "current action" work */
1307 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1308 while (!work_queue.empty() && !has_asserted()) {
1309 WorkQueueEntry work = work_queue.front();
1310 work_queue.pop_front();
1312 switch (work.type) {
1313 case WORK_CHECK_CURR_ACTION: {
1314 ModelAction *act = work.action;
1315 bool update = false; /* update this location's release seq's */
1316 bool update_all = false; /* update all release seq's */
1318 if (process_thread_action(curr))
1321 if (act->is_read() && !second_part_of_rmw && process_read(act))
1324 if (act->is_write() && process_write(act, &work_queue))
1327 if (act->is_fence() && process_fence(act))
1330 if (act->is_mutex_op() && process_mutex(act))
1333 if (act->is_relseq_fixup())
1334 process_relseq_fixup(curr, &work_queue);
1337 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1339 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1342 case WORK_CHECK_RELEASE_SEQ:
1343 resolve_release_sequences(work.location, &work_queue);
1345 case WORK_CHECK_MO_EDGES: {
1346 /** @todo Complete verification of work_queue */
1347 ModelAction *act = work.action;
1348 bool updated = false;
1350 if (act->is_read()) {
1351 const ModelAction *rf = act->get_reads_from();
1352 const Promise *promise = act->get_reads_from_promise();
1354 if (r_modification_order(act, rf))
1356 if (act->is_seqcst()) {
1357 ModelAction *last_sc_write = get_last_seq_cst_write(act);
1358 if (last_sc_write != NULL && rf->happens_before(last_sc_write)) {
1362 } else if (promise) {
1363 if (r_modification_order(act, promise))
1367 if (act->is_write()) {
1368 if (w_modification_order(act, NULL))
1371 mo_graph->commitChanges();
1374 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1383 check_curr_backtracking(curr);
1384 set_backtracking(curr);
1388 void ModelExecution::check_curr_backtracking(ModelAction *curr)
1390 Node *currnode = curr->get_node();
1391 Node *parnode = currnode->get_parent();
1393 if ((parnode && !parnode->backtrack_empty()) ||
1394 !currnode->misc_empty() ||
1395 !currnode->read_from_empty() ||
1396 !currnode->promise_empty() ||
1397 !currnode->relseq_break_empty()) {
1398 set_latest_backtrack(curr);
1402 bool ModelExecution::promises_expired() const
1404 for (unsigned int i = 0; i < promises.size(); i++) {
1405 Promise *promise = promises[i];
1406 if (promise->get_expiration() < priv->used_sequence_numbers)
1413 * This is the strongest feasibility check available.
1414 * @return whether the current trace (partial or complete) must be a prefix of
1417 bool ModelExecution::isfeasibleprefix() const
1419 return pending_rel_seqs.size() == 0 && is_feasible_prefix_ignore_relseq();
1423 * Print disagnostic information about an infeasible execution
1424 * @param prefix A string to prefix the output with; if NULL, then a default
1425 * message prefix will be provided
1427 void ModelExecution::print_infeasibility(const char *prefix) const
1431 if (mo_graph->checkForCycles())
1432 ptr += sprintf(ptr, "[mo cycle]");
1433 if (priv->failed_promise || priv->hard_failed_promise)
1434 ptr += sprintf(ptr, "[failed promise]");
1435 if (priv->too_many_reads)
1436 ptr += sprintf(ptr, "[too many reads]");
1437 if (priv->no_valid_reads)
1438 ptr += sprintf(ptr, "[no valid reads-from]");
1439 if (priv->bad_synchronization)
1440 ptr += sprintf(ptr, "[bad sw ordering]");
1441 if (priv->bad_sc_read)
1442 ptr += sprintf(ptr, "[bad sc read]");
1443 if (promises_expired())
1444 ptr += sprintf(ptr, "[promise expired]");
1445 if (promises.size() != 0)
1446 ptr += sprintf(ptr, "[unresolved promise]");
1448 model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
1452 * Returns whether the current completed trace is feasible, except for pending
1453 * release sequences.
1455 bool ModelExecution::is_feasible_prefix_ignore_relseq() const
1457 return !is_infeasible() && promises.size() == 0 && ! priv->failed_promise;
1462 * Check if the current partial trace is infeasible. Does not check any
1463 * end-of-execution flags, which might rule out the execution. Thus, this is
1464 * useful only for ruling an execution as infeasible.
1465 * @return whether the current partial trace is infeasible.
1467 bool ModelExecution::is_infeasible() const
1469 return mo_graph->checkForCycles() ||
1470 priv->no_valid_reads ||
1471 priv->too_many_reads ||
1472 priv->bad_synchronization ||
1473 priv->bad_sc_read ||
1474 priv->hard_failed_promise ||
1478 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1479 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
1480 ModelAction *lastread = get_last_action(act->get_tid());
1481 lastread->process_rmw(act);
1482 if (act->is_rmw()) {
1483 if (lastread->get_reads_from())
1484 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1486 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1487 mo_graph->commitChanges();
1493 * A helper function for ModelExecution::check_recency, to check if the current
1494 * thread is able to read from a different write/promise for 'params.maxreads'
1495 * number of steps and if that write/promise should become visible (i.e., is
1496 * ordered later in the modification order). This helps model memory liveness.
1498 * @param curr The current action. Must be a read.
1499 * @param rf The write/promise from which we plan to read
1500 * @param other_rf The write/promise from which we may read
1501 * @return True if we were able to read from other_rf for params.maxreads steps
1503 template <typename T, typename U>
1504 bool ModelExecution::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
1506 /* Need a different write/promise */
1507 if (other_rf->equals(rf))
1510 /* Only look for "newer" writes/promises */
1511 if (!mo_graph->checkReachable(rf, other_rf))
1514 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1515 action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
1516 action_list_t::reverse_iterator rit = list->rbegin();
1517 ASSERT((*rit) == curr);
1518 /* Skip past curr */
1521 /* Does this write/promise work for everyone? */
1522 for (int i = 0; i < params->maxreads; i++, rit++) {
1523 ModelAction *act = *rit;
1524 if (!act->may_read_from(other_rf))
1531 * Checks whether a thread has read from the same write or Promise for too many
1532 * times without seeing the effects of a later write/Promise.
1535 * 1) there must a different write/promise that we could read from,
1536 * 2) we must have read from the same write/promise in excess of maxreads times,
1537 * 3) that other write/promise must have been in the reads_from set for maxreads times, and
1538 * 4) that other write/promise must be mod-ordered after the write/promise we are reading.
1540 * If so, we decide that the execution is no longer feasible.
1542 * @param curr The current action. Must be a read.
1543 * @param rf The ModelAction/Promise from which we might read.
1544 * @return True if the read should succeed; false otherwise
1546 template <typename T>
1547 bool ModelExecution::check_recency(ModelAction *curr, const T *rf) const
1549 if (!params->maxreads)
1552 //NOTE: Next check is just optimization, not really necessary....
1553 if (curr->get_node()->get_read_from_past_size() +
1554 curr->get_node()->get_read_from_promise_size() <= 1)
1557 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1558 int tid = id_to_int(curr->get_tid());
1559 ASSERT(tid < (int)thrd_lists->size());
1560 action_list_t *list = &(*thrd_lists)[tid];
1561 action_list_t::reverse_iterator rit = list->rbegin();
1562 ASSERT((*rit) == curr);
1563 /* Skip past curr */
1566 action_list_t::reverse_iterator ritcopy = rit;
1567 /* See if we have enough reads from the same value */
1568 for (int count = 0; count < params->maxreads; ritcopy++, count++) {
1569 if (ritcopy == list->rend())
1571 ModelAction *act = *ritcopy;
1572 if (!act->is_read())
1574 if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
1576 if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
1578 if (act->get_node()->get_read_from_past_size() +
1579 act->get_node()->get_read_from_promise_size() <= 1)
1582 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1583 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1584 if (should_read_instead(curr, rf, write))
1585 return false; /* liveness failure */
1587 for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
1588 const Promise *promise = curr->get_node()->get_read_from_promise(i);
1589 if (should_read_instead(curr, rf, promise))
1590 return false; /* liveness failure */
1596 * @brief Updates the mo_graph with the constraints imposed from the current
1599 * Basic idea is the following: Go through each other thread and find
1600 * the last action that happened before our read. Two cases:
1602 * -# The action is a write: that write must either occur before
1603 * the write we read from or be the write we read from.
1604 * -# The action is a read: the write that that action read from
1605 * must occur before the write we read from or be the same write.
1607 * @param curr The current action. Must be a read.
1608 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1609 * @return True if modification order edges were added; false otherwise
1611 template <typename rf_type>
1612 bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
1614 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1617 ASSERT(curr->is_read());
1619 /* Last SC fence in the current thread */
1620 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1621 ModelAction *last_sc_write = NULL;
1622 if (curr->is_seqcst())
1623 last_sc_write = get_last_seq_cst_write(curr);
1625 /* Iterate over all threads */
1626 for (i = 0; i < thrd_lists->size(); i++) {
1627 /* Last SC fence in thread i */
1628 ModelAction *last_sc_fence_thread_local = NULL;
1629 if (int_to_id((int)i) != curr->get_tid())
1630 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1632 /* Last SC fence in thread i, before last SC fence in current thread */
1633 ModelAction *last_sc_fence_thread_before = NULL;
1634 if (last_sc_fence_local)
1635 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1637 /* Iterate over actions in thread, starting from most recent */
1638 action_list_t *list = &(*thrd_lists)[i];
1639 action_list_t::reverse_iterator rit;
1640 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1641 ModelAction *act = *rit;
1646 /* Don't want to add reflexive edges on 'rf' */
1647 if (act->equals(rf)) {
1648 if (act->happens_before(curr))
1654 if (act->is_write()) {
1655 /* C++, Section 29.3 statement 5 */
1656 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1657 *act < *last_sc_fence_thread_local) {
1658 added = mo_graph->addEdge(act, rf) || added;
1661 /* C++, Section 29.3 statement 4 */
1662 else if (act->is_seqcst() && last_sc_fence_local &&
1663 *act < *last_sc_fence_local) {
1664 added = mo_graph->addEdge(act, rf) || added;
1667 /* C++, Section 29.3 statement 6 */
1668 else if (last_sc_fence_thread_before &&
1669 *act < *last_sc_fence_thread_before) {
1670 added = mo_graph->addEdge(act, rf) || added;
1676 * Include at most one act per-thread that "happens
1679 if (act->happens_before(curr)) {
1680 if (act->is_write()) {
1681 added = mo_graph->addEdge(act, rf) || added;
1683 const ModelAction *prevrf = act->get_reads_from();
1684 const Promise *prevrf_promise = act->get_reads_from_promise();
1686 if (!prevrf->equals(rf))
1687 added = mo_graph->addEdge(prevrf, rf) || added;
1688 } else if (!prevrf_promise->equals(rf)) {
1689 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1698 * All compatible, thread-exclusive promises must be ordered after any
1699 * concrete loads from the same thread
1701 for (unsigned int i = 0; i < promises.size(); i++)
1702 if (promises[i]->is_compatible_exclusive(curr))
1703 added = mo_graph->addEdge(rf, promises[i]) || added;
1709 * Updates the mo_graph with the constraints imposed from the current write.
1711 * Basic idea is the following: Go through each other thread and find
1712 * the lastest action that happened before our write. Two cases:
1714 * (1) The action is a write => that write must occur before
1717 * (2) The action is a read => the write that that action read from
1718 * must occur before the current write.
1720 * This method also handles two other issues:
1722 * (I) Sequential Consistency: Making sure that if the current write is
1723 * seq_cst, that it occurs after the previous seq_cst write.
1725 * (II) Sending the write back to non-synchronizing reads.
1727 * @param curr The current action. Must be a write.
1728 * @param send_fv A vector for stashing reads to which we may pass our future
1729 * value. If NULL, then don't record any future values.
1730 * @return True if modification order edges were added; false otherwise
1732 bool ModelExecution::w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv)
1734 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1737 ASSERT(curr->is_write());
1739 if (curr->is_seqcst()) {
1740 /* We have to at least see the last sequentially consistent write,
1741 so we are initialized. */
1742 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1743 if (last_seq_cst != NULL) {
1744 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1748 /* Last SC fence in the current thread */
1749 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1751 /* Iterate over all threads */
1752 for (i = 0; i < thrd_lists->size(); i++) {
1753 /* Last SC fence in thread i, before last SC fence in current thread */
1754 ModelAction *last_sc_fence_thread_before = NULL;
1755 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1756 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1758 /* Iterate over actions in thread, starting from most recent */
1759 action_list_t *list = &(*thrd_lists)[i];
1760 action_list_t::reverse_iterator rit;
1761 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1762 ModelAction *act = *rit;
1765 * 1) If RMW and it actually read from something, then we
1766 * already have all relevant edges, so just skip to next
1769 * 2) If RMW and it didn't read from anything, we should
1770 * whatever edge we can get to speed up convergence.
1772 * 3) If normal write, we need to look at earlier actions, so
1773 * continue processing list.
1775 if (curr->is_rmw()) {
1776 if (curr->get_reads_from() != NULL)
1784 /* C++, Section 29.3 statement 7 */
1785 if (last_sc_fence_thread_before && act->is_write() &&
1786 *act < *last_sc_fence_thread_before) {
1787 added = mo_graph->addEdge(act, curr) || added;
1792 * Include at most one act per-thread that "happens
1795 if (act->happens_before(curr)) {
1797 * Note: if act is RMW, just add edge:
1799 * The following edge should be handled elsewhere:
1800 * readfrom(act) --mo--> act
1802 if (act->is_write())
1803 added = mo_graph->addEdge(act, curr) || added;
1804 else if (act->is_read()) {
1805 //if previous read accessed a null, just keep going
1806 if (act->get_reads_from() == NULL) {
1807 added = mo_graph->addEdge(act->get_reads_from_promise(), curr) || added;
1809 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1812 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1813 !act->same_thread(curr)) {
1814 /* We have an action that:
1815 (1) did not happen before us
1816 (2) is a read and we are a write
1817 (3) cannot synchronize with us
1818 (4) is in a different thread
1820 that read could potentially read from our write. Note that
1821 these checks are overly conservative at this point, we'll
1822 do more checks before actually removing the
1827 if (send_fv && thin_air_constraint_may_allow(curr, act) && check_coherence_promise(curr, act)) {
1828 if (!is_infeasible())
1829 send_fv->push_back(act);
1830 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1831 add_future_value(curr, act);
1838 * All compatible, thread-exclusive promises must be ordered after any
1839 * concrete stores to the same thread, or else they can be merged with
1842 for (unsigned int i = 0; i < promises.size(); i++)
1843 if (promises[i]->is_compatible_exclusive(curr))
1844 added = mo_graph->addEdge(curr, promises[i]) || added;
1849 //This procedure uses cohere to prune future values that are
1850 //guaranteed to generate a coherence violation.
1852 //need to see if there is (1) a promise for thread write, (2)
1853 //the promise is sb before write, (3) the promise can only be
1854 //resolved by the thread read, and (4) the promise has same
1855 //location as read/write
1857 bool ModelExecution::check_coherence_promise(const ModelAction * write, const ModelAction *read) {
1858 thread_id_t write_tid=write->get_tid();
1859 for(unsigned int i = promises.size(); i>0; i--) {
1860 Promise *pr=promises[i-1];
1861 if (!pr->same_location(write))
1863 //the reading thread is the only thread that can resolve the promise
1864 if (pr->get_num_was_available_threads()==1 && pr->thread_was_available(read->get_tid())) {
1865 for(unsigned int j=0;j<pr->get_num_readers();j++) {
1866 ModelAction *prreader=pr->get_reader(j);
1867 //the writing thread reads from the promise before the write
1868 if (prreader->get_tid()==write_tid &&
1869 (*prreader)<(*write)) {
1870 if ((*read)>(*prreader)) {
1871 //check that we don't have a read between the read and promise
1872 //from the same thread as read
1874 for(const ModelAction *tmp=read;tmp!=prreader;) {
1875 tmp=tmp->get_node()->get_parent()->get_action();
1876 if (tmp->is_read() && tmp->same_thread(read)) {
1893 /** Arbitrary reads from the future are not allowed. Section 29.3
1894 * part 9 places some constraints. This method checks one result of constraint
1895 * constraint. Others require compiler support. */
1896 bool ModelExecution::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader) const
1898 if (!writer->is_rmw())
1901 if (!reader->is_rmw())
1904 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1905 if (search == reader)
1907 if (search->get_tid() == reader->get_tid() &&
1908 search->happens_before(reader))
1916 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1917 * some constraints. This method checks one the following constraint (others
1918 * require compiler support):
1920 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1921 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
1923 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1925 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1927 /* Iterate over all threads */
1928 for (i = 0; i < thrd_lists->size(); i++) {
1929 const ModelAction *write_after_read = NULL;
1931 /* Iterate over actions in thread, starting from most recent */
1932 action_list_t *list = &(*thrd_lists)[i];
1933 action_list_t::reverse_iterator rit;
1934 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1935 ModelAction *act = *rit;
1937 /* Don't disallow due to act == reader */
1938 if (!reader->happens_before(act) || reader == act)
1940 else if (act->is_write())
1941 write_after_read = act;
1942 else if (act->is_read() && act->get_reads_from() != NULL)
1943 write_after_read = act->get_reads_from();
1946 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1953 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1954 * The ModelAction under consideration is expected to be taking part in
1955 * release/acquire synchronization as an object of the "reads from" relation.
1956 * Note that this can only provide release sequence support for RMW chains
1957 * which do not read from the future, as those actions cannot be traced until
1958 * their "promise" is fulfilled. Similarly, we may not even establish the
1959 * presence of a release sequence with certainty, as some modification order
1960 * constraints may be decided further in the future. Thus, this function
1961 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1962 * and a boolean representing certainty.
1964 * @param rf The action that might be part of a release sequence. Must be a
1966 * @param release_heads A pass-by-reference style return parameter. After
1967 * execution of this function, release_heads will contain the heads of all the
1968 * relevant release sequences, if any exists with certainty
1969 * @param pending A pass-by-reference style return parameter which is only used
1970 * when returning false (i.e., uncertain). Returns most information regarding
1971 * an uncertain release sequence, including any write operations that might
1972 * break the sequence.
1973 * @return true, if the ModelExecution is certain that release_heads is complete;
1976 bool ModelExecution::release_seq_heads(const ModelAction *rf,
1977 rel_heads_list_t *release_heads,
1978 struct release_seq *pending) const
1980 /* Only check for release sequences if there are no cycles */
1981 if (mo_graph->checkForCycles())
1984 for ( ; rf != NULL; rf = rf->get_reads_from()) {
1985 ASSERT(rf->is_write());
1987 if (rf->is_release())
1988 release_heads->push_back(rf);
1989 else if (rf->get_last_fence_release())
1990 release_heads->push_back(rf->get_last_fence_release());
1992 break; /* End of RMW chain */
1994 /** @todo Need to be smarter here... In the linux lock
1995 * example, this will run to the beginning of the program for
1997 /** @todo The way to be smarter here is to keep going until 1
1998 * thread has a release preceded by an acquire and you've seen
2001 /* acq_rel RMW is a sufficient stopping condition */
2002 if (rf->is_acquire() && rf->is_release())
2003 return true; /* complete */
2006 /* read from future: need to settle this later */
2008 return false; /* incomplete */
2011 if (rf->is_release())
2012 return true; /* complete */
2014 /* else relaxed write
2015 * - check for fence-release in the same thread (29.8, stmt. 3)
2016 * - check modification order for contiguous subsequence
2017 * -> rf must be same thread as release */
2019 const ModelAction *fence_release = rf->get_last_fence_release();
2020 /* Synchronize with a fence-release unconditionally; we don't need to
2021 * find any more "contiguous subsequence..." for it */
2023 release_heads->push_back(fence_release);
2025 int tid = id_to_int(rf->get_tid());
2026 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(rf->get_location());
2027 action_list_t *list = &(*thrd_lists)[tid];
2028 action_list_t::const_reverse_iterator rit;
2030 /* Find rf in the thread list */
2031 rit = std::find(list->rbegin(), list->rend(), rf);
2032 ASSERT(rit != list->rend());
2034 /* Find the last {write,fence}-release */
2035 for (; rit != list->rend(); rit++) {
2036 if (fence_release && *(*rit) < *fence_release)
2038 if ((*rit)->is_release())
2041 if (rit == list->rend()) {
2042 /* No write-release in this thread */
2043 return true; /* complete */
2044 } else if (fence_release && *(*rit) < *fence_release) {
2045 /* The fence-release is more recent (and so, "stronger") than
2046 * the most recent write-release */
2047 return true; /* complete */
2048 } /* else, need to establish contiguous release sequence */
2049 ModelAction *release = *rit;
2051 ASSERT(rf->same_thread(release));
2053 pending->writes.clear();
2055 bool certain = true;
2056 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2057 if (id_to_int(rf->get_tid()) == (int)i)
2059 list = &(*thrd_lists)[i];
2061 /* Can we ensure no future writes from this thread may break
2062 * the release seq? */
2063 bool future_ordered = false;
2065 ModelAction *last = get_last_action(int_to_id(i));
2066 Thread *th = get_thread(int_to_id(i));
2067 if ((last && rf->happens_before(last)) ||
2070 future_ordered = true;
2072 ASSERT(!th->is_model_thread() || future_ordered);
2074 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2075 const ModelAction *act = *rit;
2076 /* Reach synchronization -> this thread is complete */
2077 if (act->happens_before(release))
2079 if (rf->happens_before(act)) {
2080 future_ordered = true;
2084 /* Only non-RMW writes can break release sequences */
2085 if (!act->is_write() || act->is_rmw())
2088 /* Check modification order */
2089 if (mo_graph->checkReachable(rf, act)) {
2090 /* rf --mo--> act */
2091 future_ordered = true;
2094 if (mo_graph->checkReachable(act, release))
2095 /* act --mo--> release */
2097 if (mo_graph->checkReachable(release, act) &&
2098 mo_graph->checkReachable(act, rf)) {
2099 /* release --mo-> act --mo--> rf */
2100 return true; /* complete */
2102 /* act may break release sequence */
2103 pending->writes.push_back(act);
2106 if (!future_ordered)
2107 certain = false; /* This thread is uncertain */
2111 release_heads->push_back(release);
2112 pending->writes.clear();
2114 pending->release = release;
2121 * An interface for getting the release sequence head(s) with which a
2122 * given ModelAction must synchronize. This function only returns a non-empty
2123 * result when it can locate a release sequence head with certainty. Otherwise,
2124 * it may mark the internal state of the ModelExecution so that it will handle
2125 * the release sequence at a later time, causing @a acquire to update its
2126 * synchronization at some later point in execution.
2128 * @param acquire The 'acquire' action that may synchronize with a release
2130 * @param read The read action that may read from a release sequence; this may
2131 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2132 * when 'acquire' is a fence-acquire)
2133 * @param release_heads A pass-by-reference return parameter. Will be filled
2134 * with the head(s) of the release sequence(s), if they exists with certainty.
2135 * @see ModelExecution::release_seq_heads
2137 void ModelExecution::get_release_seq_heads(ModelAction *acquire,
2138 ModelAction *read, rel_heads_list_t *release_heads)
2140 const ModelAction *rf = read->get_reads_from();
2141 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2142 sequence->acquire = acquire;
2143 sequence->read = read;
2145 if (!release_seq_heads(rf, release_heads, sequence)) {
2146 /* add act to 'lazy checking' list */
2147 pending_rel_seqs.push_back(sequence);
2149 snapshot_free(sequence);
2154 * @brief Propagate a modified clock vector to actions later in the execution
2157 * After an acquire operation lazily completes a release-sequence
2158 * synchronization, we must update all clock vectors for operations later than
2159 * the acquire in the execution order.
2161 * @param acquire The ModelAction whose clock vector must be propagated
2162 * @param work The work queue to which we can add work items, if this
2163 * propagation triggers more updates (e.g., to the modification order)
2165 void ModelExecution::propagate_clockvector(ModelAction *acquire, work_queue_t *work)
2167 /* Re-check all pending release sequences */
2168 work->push_back(CheckRelSeqWorkEntry(NULL));
2169 /* Re-check read-acquire for mo_graph edges */
2170 work->push_back(MOEdgeWorkEntry(acquire));
2172 /* propagate synchronization to later actions */
2173 action_list_t::reverse_iterator rit = action_trace.rbegin();
2174 for (; (*rit) != acquire; rit++) {
2175 ModelAction *propagate = *rit;
2176 if (acquire->happens_before(propagate)) {
2177 synchronize(acquire, propagate);
2178 /* Re-check 'propagate' for mo_graph edges */
2179 work->push_back(MOEdgeWorkEntry(propagate));
2185 * Attempt to resolve all stashed operations that might synchronize with a
2186 * release sequence for a given location. This implements the "lazy" portion of
2187 * determining whether or not a release sequence was contiguous, since not all
2188 * modification order information is present at the time an action occurs.
2190 * @param location The location/object that should be checked for release
2191 * sequence resolutions. A NULL value means to check all locations.
2192 * @param work_queue The work queue to which to add work items as they are
2194 * @return True if any updates occurred (new synchronization, new mo_graph
2197 bool ModelExecution::resolve_release_sequences(void *location, work_queue_t *work_queue)
2199 bool updated = false;
2200 SnapVector<struct release_seq *>::iterator it = pending_rel_seqs.begin();
2201 while (it != pending_rel_seqs.end()) {
2202 struct release_seq *pending = *it;
2203 ModelAction *acquire = pending->acquire;
2204 const ModelAction *read = pending->read;
2206 /* Only resolve sequences on the given location, if provided */
2207 if (location && read->get_location() != location) {
2212 const ModelAction *rf = read->get_reads_from();
2213 rel_heads_list_t release_heads;
2215 complete = release_seq_heads(rf, &release_heads, pending);
2216 for (unsigned int i = 0; i < release_heads.size(); i++)
2217 if (!acquire->has_synchronized_with(release_heads[i]))
2218 if (synchronize(release_heads[i], acquire))
2222 /* Propagate the changed clock vector */
2223 propagate_clockvector(acquire, work_queue);
2226 it = pending_rel_seqs.erase(it);
2227 snapshot_free(pending);
2233 // If we resolved promises or data races, see if we have realized a data race.
2240 * Performs various bookkeeping operations for the current ModelAction. For
2241 * instance, adds action to the per-object, per-thread action vector and to the
2242 * action trace list of all thread actions.
2244 * @param act is the ModelAction to add.
2246 void ModelExecution::add_action_to_lists(ModelAction *act)
2248 int tid = id_to_int(act->get_tid());
2249 ModelAction *uninit = NULL;
2251 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
2252 if (list->empty() && act->is_atomic_var()) {
2253 uninit = get_uninitialized_action(act);
2254 uninit_id = id_to_int(uninit->get_tid());
2255 list->push_front(uninit);
2257 list->push_back(act);
2259 action_trace.push_back(act);
2261 action_trace.push_front(uninit);
2263 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
2264 if (tid >= (int)vec->size())
2265 vec->resize(priv->next_thread_id);
2266 (*vec)[tid].push_back(act);
2268 (*vec)[uninit_id].push_front(uninit);
2270 if ((int)thrd_last_action.size() <= tid)
2271 thrd_last_action.resize(get_num_threads());
2272 thrd_last_action[tid] = act;
2274 thrd_last_action[uninit_id] = uninit;
2276 if (act->is_fence() && act->is_release()) {
2277 if ((int)thrd_last_fence_release.size() <= tid)
2278 thrd_last_fence_release.resize(get_num_threads());
2279 thrd_last_fence_release[tid] = act;
2282 if (act->is_wait()) {
2283 void *mutex_loc = (void *) act->get_value();
2284 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
2286 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
2287 if (tid >= (int)vec->size())
2288 vec->resize(priv->next_thread_id);
2289 (*vec)[tid].push_back(act);
2294 * @brief Get the last action performed by a particular Thread
2295 * @param tid The thread ID of the Thread in question
2296 * @return The last action in the thread
2298 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
2300 int threadid = id_to_int(tid);
2301 if (threadid < (int)thrd_last_action.size())
2302 return thrd_last_action[id_to_int(tid)];
2308 * @brief Get the last fence release performed by a particular Thread
2309 * @param tid The thread ID of the Thread in question
2310 * @return The last fence release in the thread, if one exists; NULL otherwise
2312 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
2314 int threadid = id_to_int(tid);
2315 if (threadid < (int)thrd_last_fence_release.size())
2316 return thrd_last_fence_release[id_to_int(tid)];
2322 * Gets the last memory_order_seq_cst write (in the total global sequence)
2323 * performed on a particular object (i.e., memory location), not including the
2325 * @param curr The current ModelAction; also denotes the object location to
2327 * @return The last seq_cst write
2329 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
2331 void *location = curr->get_location();
2332 action_list_t *list = obj_map.get(location);
2333 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2334 action_list_t::reverse_iterator rit;
2335 for (rit = list->rbegin(); (*rit) != curr; rit++)
2337 rit++; /* Skip past curr */
2338 for ( ; rit != list->rend(); rit++)
2339 if ((*rit)->is_write() && (*rit)->is_seqcst())
2345 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2346 * performed in a particular thread, prior to a particular fence.
2347 * @param tid The ID of the thread to check
2348 * @param before_fence The fence from which to begin the search; if NULL, then
2349 * search for the most recent fence in the thread.
2350 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2352 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2354 /* All fences should have location FENCE_LOCATION */
2355 action_list_t *list = obj_map.get(FENCE_LOCATION);
2360 action_list_t::reverse_iterator rit = list->rbegin();
2363 for (; rit != list->rend(); rit++)
2364 if (*rit == before_fence)
2367 ASSERT(*rit == before_fence);
2371 for (; rit != list->rend(); rit++)
2372 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2378 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2379 * location). This function identifies the mutex according to the current
2380 * action, which is presumed to perform on the same mutex.
2381 * @param curr The current ModelAction; also denotes the object location to
2383 * @return The last unlock operation
2385 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
2387 void *location = curr->get_location();
2389 action_list_t *list = obj_map.get(location);
2390 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2391 action_list_t::reverse_iterator rit;
2392 for (rit = list->rbegin(); rit != list->rend(); rit++)
2393 if ((*rit)->is_unlock() || (*rit)->is_wait())
2398 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
2400 ModelAction *parent = get_last_action(tid);
2402 parent = get_thread(tid)->get_creation();
2407 * Returns the clock vector for a given thread.
2408 * @param tid The thread whose clock vector we want
2409 * @return Desired clock vector
2411 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
2413 return get_parent_action(tid)->get_cv();
2417 * @brief Find the promise (if any) to resolve for the current action and
2418 * remove it from the pending promise vector
2419 * @param curr The current ModelAction. Should be a write.
2420 * @return The Promise to resolve, if any; otherwise NULL
2422 Promise * ModelExecution::pop_promise_to_resolve(const ModelAction *curr)
2424 for (unsigned int i = 0; i < promises.size(); i++)
2425 if (curr->get_node()->get_promise(i)) {
2426 Promise *ret = promises[i];
2427 promises.erase(promises.begin() + i);
2434 * Resolve a Promise with a current write.
2435 * @param write The ModelAction that is fulfilling Promises
2436 * @param promise The Promise to resolve
2437 * @param work The work queue, for adding new fixup work
2438 * @return True if the Promise was successfully resolved; false otherwise
2440 bool ModelExecution::resolve_promise(ModelAction *write, Promise *promise,
2443 ModelVector<ModelAction *> actions_to_check;
2445 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2446 ModelAction *read = promise->get_reader(i);
2447 if (read_from(read, write)) {
2448 /* Propagate the changed clock vector */
2449 propagate_clockvector(read, work);
2451 actions_to_check.push_back(read);
2453 /* Make sure the promise's value matches the write's value */
2454 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2455 if (!mo_graph->resolvePromise(promise, write))
2456 priv->hard_failed_promise = true;
2459 * @todo It is possible to end up in an inconsistent state, where a
2460 * "resolved" promise may still be referenced if
2461 * CycleGraph::resolvePromise() failed, so don't delete 'promise'.
2463 * Note that the inconsistency only matters when dumping mo_graph to
2469 //Check whether reading these writes has made threads unable to
2471 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2472 ModelAction *read = actions_to_check[i];
2473 mo_check_promises(read, true);
2480 * Compute the set of promises that could potentially be satisfied by this
2481 * action. Note that the set computation actually appears in the Node, not in
2483 * @param curr The ModelAction that may satisfy promises
2485 void ModelExecution::compute_promises(ModelAction *curr)
2487 for (unsigned int i = 0; i < promises.size(); i++) {
2488 Promise *promise = promises[i];
2489 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2492 bool satisfy = true;
2493 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2494 const ModelAction *act = promise->get_reader(j);
2495 if (act->happens_before(curr) ||
2496 act->could_synchronize_with(curr)) {
2502 curr->get_node()->set_promise(i);
2506 /** Checks promises in response to change in ClockVector Threads. */
2507 void ModelExecution::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2509 for (unsigned int i = 0; i < promises.size(); i++) {
2510 Promise *promise = promises[i];
2511 if (!promise->thread_is_available(tid))
2513 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2514 const ModelAction *act = promise->get_reader(j);
2515 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2516 merge_cv->synchronized_since(act)) {
2517 if (promise->eliminate_thread(tid)) {
2518 /* Promise has failed */
2519 priv->failed_promise = true;
2527 void ModelExecution::check_promises_thread_disabled()
2529 for (unsigned int i = 0; i < promises.size(); i++) {
2530 Promise *promise = promises[i];
2531 if (promise->has_failed()) {
2532 priv->failed_promise = true;
2539 * @brief Checks promises in response to addition to modification order for
2542 * We test whether threads are still available for satisfying promises after an
2543 * addition to our modification order constraints. Those that are unavailable
2544 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2545 * that promise has failed.
2547 * @param act The ModelAction which updated the modification order
2548 * @param is_read_check Should be true if act is a read and we must check for
2549 * updates to the store from which it read (there is a distinction here for
2550 * RMW's, which are both a load and a store)
2552 void ModelExecution::mo_check_promises(const ModelAction *act, bool is_read_check)
2554 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2556 for (unsigned int i = 0; i < promises.size(); i++) {
2557 Promise *promise = promises[i];
2559 // Is this promise on the same location?
2560 if (!promise->same_location(write))
2563 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2564 const ModelAction *pread = promise->get_reader(j);
2565 if (!pread->happens_before(act))
2567 if (mo_graph->checkPromise(write, promise)) {
2568 priv->hard_failed_promise = true;
2574 // Don't do any lookups twice for the same thread
2575 if (!promise->thread_is_available(act->get_tid()))
2578 if (mo_graph->checkReachable(promise, write)) {
2579 if (mo_graph->checkPromise(write, promise)) {
2580 priv->hard_failed_promise = true;
2588 * Compute the set of writes that may break the current pending release
2589 * sequence. This information is extracted from previou release sequence
2592 * @param curr The current ModelAction. Must be a release sequence fixup
2595 void ModelExecution::compute_relseq_breakwrites(ModelAction *curr)
2597 if (pending_rel_seqs.empty())
2600 struct release_seq *pending = pending_rel_seqs.back();
2601 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2602 const ModelAction *write = pending->writes[i];
2603 curr->get_node()->add_relseq_break(write);
2606 /* NULL means don't break the sequence; just synchronize */
2607 curr->get_node()->add_relseq_break(NULL);
2611 * Build up an initial set of all past writes that this 'read' action may read
2612 * from, as well as any previously-observed future values that must still be valid.
2614 * @param curr is the current ModelAction that we are exploring; it must be a
2617 void ModelExecution::build_may_read_from(ModelAction *curr)
2619 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
2621 ASSERT(curr->is_read());
2623 ModelAction *last_sc_write = NULL;
2625 if (curr->is_seqcst())
2626 last_sc_write = get_last_seq_cst_write(curr);
2628 /* Iterate over all threads */
2629 for (i = 0; i < thrd_lists->size(); i++) {
2630 /* Iterate over actions in thread, starting from most recent */
2631 action_list_t *list = &(*thrd_lists)[i];
2632 action_list_t::reverse_iterator rit;
2633 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2634 ModelAction *act = *rit;
2636 /* Only consider 'write' actions */
2637 if (!act->is_write() || act == curr)
2640 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2641 bool allow_read = true;
2643 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2645 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2649 /* Only add feasible reads */
2650 mo_graph->startChanges();
2651 r_modification_order(curr, act);
2652 if (!is_infeasible())
2653 curr->get_node()->add_read_from_past(act);
2654 mo_graph->rollbackChanges();
2657 /* Include at most one act per-thread that "happens before" curr */
2658 if (act->happens_before(curr))
2663 /* Inherit existing, promised future values */
2664 for (i = 0; i < promises.size(); i++) {
2665 const Promise *promise = promises[i];
2666 const ModelAction *promise_read = promise->get_reader(0);
2667 if (promise_read->same_var(curr)) {
2668 /* Only add feasible future-values */
2669 mo_graph->startChanges();
2670 r_modification_order(curr, promise);
2671 if (!is_infeasible())
2672 curr->get_node()->add_read_from_promise(promise_read);
2673 mo_graph->rollbackChanges();
2677 /* We may find no valid may-read-from only if the execution is doomed */
2678 if (!curr->get_node()->read_from_size()) {
2679 priv->no_valid_reads = true;
2683 if (DBG_ENABLED()) {
2684 model_print("Reached read action:\n");
2686 model_print("Printing read_from_past\n");
2687 curr->get_node()->print_read_from_past();
2688 model_print("End printing read_from_past\n");
2692 bool ModelExecution::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2694 for ( ; write != NULL; write = write->get_reads_from()) {
2695 /* UNINIT actions don't have a Node, and they never sleep */
2696 if (write->is_uninitialized())
2698 Node *prevnode = write->get_node()->get_parent();
2700 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2701 if (write->is_release() && thread_sleep)
2703 if (!write->is_rmw())
2710 * @brief Get an action representing an uninitialized atomic
2712 * This function may create a new one or try to retrieve one from the NodeStack
2714 * @param curr The current action, which prompts the creation of an UNINIT action
2715 * @return A pointer to the UNINIT ModelAction
2717 ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
2719 Node *node = curr->get_node();
2720 ModelAction *act = node->get_uninit_action();
2722 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
2723 node->set_uninit_action(act);
2725 act->create_cv(NULL);
2729 static void print_list(const action_list_t *list)
2731 action_list_t::const_iterator it;
2733 model_print("------------------------------------------------------------------------------------\n");
2734 model_print("# t Action type MO Location Value Rf CV\n");
2735 model_print("------------------------------------------------------------------------------------\n");
2737 unsigned int hash = 0;
2739 for (it = list->begin(); it != list->end(); it++) {
2740 const ModelAction *act = *it;
2741 if (act->get_seq_number() > 0)
2743 hash = hash^(hash<<3)^((*it)->hash());
2745 model_print("HASH %u\n", hash);
2746 model_print("------------------------------------------------------------------------------------\n");
2749 #if SUPPORT_MOD_ORDER_DUMP
2750 void ModelExecution::dumpGraph(char *filename) const
2753 sprintf(buffer, "%s.dot", filename);
2754 FILE *file = fopen(buffer, "w");
2755 fprintf(file, "digraph %s {\n", filename);
2756 mo_graph->dumpNodes(file);
2757 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2759 for (action_list_t::const_iterator it = action_trace.begin(); it != action_trace.end(); it++) {
2760 ModelAction *act = *it;
2761 if (act->is_read()) {
2762 mo_graph->dot_print_node(file, act);
2763 if (act->get_reads_from())
2764 mo_graph->dot_print_edge(file,
2765 act->get_reads_from(),
2767 "label=\"rf\", color=red, weight=2");
2769 mo_graph->dot_print_edge(file,
2770 act->get_reads_from_promise(),
2772 "label=\"rf\", color=red");
2774 if (thread_array[act->get_tid()]) {
2775 mo_graph->dot_print_edge(file,
2776 thread_array[id_to_int(act->get_tid())],
2778 "label=\"sb\", color=blue, weight=400");
2781 thread_array[act->get_tid()] = act;
2783 fprintf(file, "}\n");
2784 model_free(thread_array);
2789 /** @brief Prints an execution trace summary. */
2790 void ModelExecution::print_summary() const
2792 #if SUPPORT_MOD_ORDER_DUMP
2793 char buffername[100];
2794 sprintf(buffername, "exec%04u", get_execution_number());
2795 mo_graph->dumpGraphToFile(buffername);
2796 sprintf(buffername, "graph%04u", get_execution_number());
2797 dumpGraph(buffername);
2800 model_print("Execution trace %d:", get_execution_number());
2801 if (isfeasibleprefix()) {
2802 if (is_yieldblocked())
2803 model_print(" YIELD BLOCKED");
2804 if (scheduler->all_threads_sleeping())
2805 model_print(" SLEEP-SET REDUNDANT");
2806 if (have_bug_reports())
2807 model_print(" DETECTED BUG(S)");
2809 print_infeasibility(" INFEASIBLE");
2812 print_list(&action_trace);
2815 if (!promises.empty()) {
2816 model_print("Pending promises:\n");
2817 for (unsigned int i = 0; i < promises.size(); i++) {
2818 model_print(" [P%u] ", i);
2819 promises[i]->print();
2826 * Add a Thread to the system for the first time. Should only be called once
2828 * @param t The Thread to add
2830 void ModelExecution::add_thread(Thread *t)
2832 unsigned int i = id_to_int(t->get_id());
2833 if (i >= thread_map.size())
2834 thread_map.resize(i + 1);
2836 if (!t->is_model_thread())
2837 scheduler->add_thread(t);
2841 * @brief Get a Thread reference by its ID
2842 * @param tid The Thread's ID
2843 * @return A Thread reference
2845 Thread * ModelExecution::get_thread(thread_id_t tid) const
2847 unsigned int i = id_to_int(tid);
2848 if (i < thread_map.size())
2849 return thread_map[i];
2854 * @brief Get a reference to the Thread in which a ModelAction was executed
2855 * @param act The ModelAction
2856 * @return A Thread reference
2858 Thread * ModelExecution::get_thread(const ModelAction *act) const
2860 return get_thread(act->get_tid());
2864 * @brief Get a Thread reference by its pthread ID
2865 * @param index The pthread's ID
2866 * @return A Thread reference
2868 Thread * ModelExecution::get_pthread(pthread_t pid) {
2869 if (pid < pthread_counter + 1) return pthread_map[pid];
2874 * @brief Get a Promise's "promise number"
2876 * A "promise number" is an index number that is unique to a promise, valid
2877 * only for a specific snapshot of an execution trace. Promises may come and go
2878 * as they are generated an resolved, so an index only retains meaning for the
2881 * @param promise The Promise to check
2882 * @return The promise index, if the promise still is valid; otherwise -1
2884 int ModelExecution::get_promise_number(const Promise *promise) const
2886 for (unsigned int i = 0; i < promises.size(); i++)
2887 if (promises[i] == promise)
2894 * @brief Check if a Thread is currently enabled
2895 * @param t The Thread to check
2896 * @return True if the Thread is currently enabled
2898 bool ModelExecution::is_enabled(Thread *t) const
2900 return scheduler->is_enabled(t);
2904 * @brief Check if a Thread is currently enabled
2905 * @param tid The ID of the Thread to check
2906 * @return True if the Thread is currently enabled
2908 bool ModelExecution::is_enabled(thread_id_t tid) const
2910 return scheduler->is_enabled(tid);
2914 * @brief Select the next thread to execute based on the curren action
2916 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
2917 * actions should be followed by the execution of their child thread. In either
2918 * case, the current action should determine the next thread schedule.
2920 * @param curr The current action
2921 * @return The next thread to run, if the current action will determine this
2922 * selection; otherwise NULL
2924 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
2926 /* Do not split atomic RMW */
2927 if (curr->is_rmwr())
2928 return get_thread(curr);
2929 if (curr->is_write()) {
2930 // std::memory_order order = curr->get_mo();
2932 // case std::memory_order_relaxed:
2933 // return get_thread(curr);
2934 // case std::memory_order_release:
2935 // return get_thread(curr);
2942 /* Follow CREATE with the created thread */
2943 /* which is not needed, because model.cc takes care of this */
2944 if (curr->get_type() == THREAD_CREATE)
2945 return curr->get_thread_operand();
2946 if (curr->get_type() == PTHREAD_CREATE) {
2947 return curr->get_thread_operand();
2952 /** @return True if the execution has taken too many steps */
2953 bool ModelExecution::too_many_steps() const
2955 return params->bound != 0 && priv->used_sequence_numbers > params->bound;
2959 * Takes the next step in the execution, if possible.
2960 * @param curr The current step to take
2961 * @return Returns the next Thread to run, if any; NULL if this execution
2964 Thread * ModelExecution::take_step(ModelAction *curr)
2966 Thread *curr_thrd = get_thread(curr);
2967 ASSERT(curr_thrd->get_state() == THREAD_READY);
2969 ASSERT(check_action_enabled(curr)); /* May have side effects? */
2970 curr = check_current_action(curr);
2973 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2974 scheduler->remove_thread(curr_thrd);
2976 return action_select_next_thread(curr);
2980 * Launch end-of-execution release sequence fixups only when
2981 * the execution is otherwise feasible AND there are:
2983 * (1) pending release sequences
2984 * (2) pending assertions that could be invalidated by a change
2985 * in clock vectors (i.e., data races)
2986 * (3) no pending promises
2988 void ModelExecution::fixup_release_sequences()
2990 while (!pending_rel_seqs.empty() &&
2991 is_feasible_prefix_ignore_relseq() &&
2992 haveUnrealizedRaces()) {
2993 model_print("*** WARNING: release sequence fixup action "
2994 "(%zu pending release seuqence(s)) ***\n",
2995 pending_rel_seqs.size());
2996 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2997 std::memory_order_seq_cst, NULL, VALUE_NONE,