12 #include "clockvector.h"
13 #include "cyclegraph.h"
15 #include "threads-model.h"
16 #include "bugmessage.h"
19 #define INITIAL_THREAD_ID 0
22 * Structure for holding small ModelChecker members that should be snapshotted
24 struct model_snapshot_members {
25 model_snapshot_members() :
26 /* First thread created will have id INITIAL_THREAD_ID */
27 next_thread_id(INITIAL_THREAD_ID),
28 used_sequence_numbers(0),
30 bad_synchronization(false),
34 ~model_snapshot_members() {
35 for (unsigned int i = 0;i < bugs.size();i++)
40 unsigned int next_thread_id;
41 modelclock_t used_sequence_numbers;
42 SnapVector<bug_message *> bugs;
43 /** @brief Incorrectly-ordered synchronization was made */
44 bool bad_synchronization;
50 /** @brief Constructor */
51 ModelExecution::ModelExecution(ModelChecker *m, Scheduler *scheduler, NodeStack *node_stack) :
56 thread_map(2), /* We'll always need at least 2 threads */
60 condvar_waiters_map(),
64 thrd_last_fence_release(),
65 node_stack(node_stack),
66 priv(new struct model_snapshot_members ()),
67 mo_graph(new CycleGraph()),
70 /* Initialize a model-checker thread, for special ModelActions */
71 model_thread = new Thread(get_next_id());
72 add_thread(model_thread);
73 scheduler->register_engine(this);
74 node_stack->register_engine(this);
77 /** @brief Destructor */
78 ModelExecution::~ModelExecution()
80 for (unsigned int i = 0;i < get_num_threads();i++)
81 delete get_thread(int_to_id(i));
87 int ModelExecution::get_execution_number() const
89 return model->get_execution_number();
92 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
94 action_list_t *tmp = hash->get(ptr);
96 tmp = new action_list_t();
102 static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
104 SnapVector<action_list_t> *tmp = hash->get(ptr);
106 tmp = new SnapVector<action_list_t>();
112 /** @return a thread ID for a new Thread */
113 thread_id_t ModelExecution::get_next_id()
115 return priv->next_thread_id++;
118 /** @return the number of user threads created during this execution */
119 unsigned int ModelExecution::get_num_threads() const
121 return priv->next_thread_id;
124 /** @return a sequence number for a new ModelAction */
125 modelclock_t ModelExecution::get_next_seq_num()
127 return ++priv->used_sequence_numbers;
131 * @brief Should the current action wake up a given thread?
133 * @param curr The current action
134 * @param thread The thread that we might wake up
135 * @return True, if we should wake up the sleeping thread; false otherwise
137 bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
139 const ModelAction *asleep = thread->get_pending();
140 /* Don't allow partial RMW to wake anyone up */
143 /* Synchronizing actions may have been backtracked */
144 if (asleep->could_synchronize_with(curr))
146 /* All acquire/release fences and fence-acquire/store-release */
147 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
149 /* Fence-release + store can awake load-acquire on the same location */
150 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
151 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
152 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
158 void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
160 for (unsigned int i = 0;i < get_num_threads();i++) {
161 Thread *thr = get_thread(int_to_id(i));
162 if (scheduler->is_sleep_set(thr)) {
163 if (should_wake_up(curr, thr))
164 /* Remove this thread from sleep set */
165 scheduler->remove_sleep(thr);
170 /** @brief Alert the model-checker that an incorrectly-ordered
171 * synchronization was made */
172 void ModelExecution::set_bad_synchronization()
174 priv->bad_synchronization = true;
177 bool ModelExecution::assert_bug(const char *msg)
179 priv->bugs.push_back(new bug_message(msg));
181 if (isfeasibleprefix()) {
188 /** @return True, if any bugs have been reported for this execution */
189 bool ModelExecution::have_bug_reports() const
191 return priv->bugs.size() != 0;
194 SnapVector<bug_message *> * ModelExecution::get_bugs() const
200 * Check whether the current trace has triggered an assertion which should halt
203 * @return True, if the execution should be aborted; false otherwise
205 bool ModelExecution::has_asserted() const
207 return priv->asserted;
211 * Trigger a trace assertion which should cause this execution to be halted.
212 * This can be due to a detected bug or due to an infeasibility that should
215 void ModelExecution::set_assert()
217 priv->asserted = true;
221 * Check if we are in a deadlock. Should only be called at the end of an
222 * execution, although it should not give false positives in the middle of an
223 * execution (there should be some ENABLED thread).
225 * @return True if program is in a deadlock; false otherwise
227 bool ModelExecution::is_deadlocked() const
229 bool blocking_threads = false;
230 for (unsigned int i = 0;i < get_num_threads();i++) {
231 thread_id_t tid = int_to_id(i);
234 Thread *t = get_thread(tid);
235 if (!t->is_model_thread() && t->get_pending())
236 blocking_threads = true;
238 return blocking_threads;
242 * Check if this is a complete execution. That is, have all thread completed
243 * execution (rather than exiting because sleep sets have forced a redundant
246 * @return True if the execution is complete.
248 bool ModelExecution::is_complete_execution() const
250 for (unsigned int i = 0;i < get_num_threads();i++)
251 if (is_enabled(int_to_id(i)))
258 * Processes a read model action.
259 * @param curr is the read model action to process.
260 * @param rf_set is the set of model actions we can possibly read from
261 * @return True if processing this read updates the mo_graph.
263 void ModelExecution::process_read(ModelAction *curr, SnapVector<const ModelAction *> * rf_set)
265 SnapVector<const ModelAction *> * priorset = new SnapVector<const ModelAction *>();
268 int index = fuzzer->selectWrite(curr, rf_set);
269 const ModelAction *rf = (*rf_set)[index];
274 if (r_modification_order(curr, rf, priorset)) {
275 for(unsigned int i=0;i<priorset->size();i++) {
276 mo_graph->addEdge((*priorset)[i], rf);
279 get_thread(curr)->set_return_value(curr->get_return_value());
284 (*rf_set)[index] = rf_set->back();
290 * Processes a lock, trylock, or unlock model action. @param curr is
291 * the read model action to process.
293 * The try lock operation checks whether the lock is taken. If not,
294 * it falls to the normal lock operation case. If so, it returns
297 * The lock operation has already been checked that it is enabled, so
298 * it just grabs the lock and synchronizes with the previous unlock.
300 * The unlock operation has to re-enable all of the threads that are
301 * waiting on the lock.
303 * @return True if synchronization was updated; false otherwise
305 bool ModelExecution::process_mutex(ModelAction *curr)
307 cdsc::mutex *mutex = curr->get_mutex();
308 struct cdsc::mutex_state *state = NULL;
311 state = mutex->get_state();
313 switch (curr->get_type()) {
314 case ATOMIC_TRYLOCK: {
315 bool success = !state->locked;
316 curr->set_try_lock(success);
318 get_thread(curr)->set_return_value(0);
321 get_thread(curr)->set_return_value(1);
323 //otherwise fall into the lock case
325 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
326 assert_bug("Lock access before initialization");
327 state->locked = get_thread(curr);
328 ModelAction *unlock = get_last_unlock(curr);
329 //synchronize with the previous unlock statement
330 if (unlock != NULL) {
331 synchronize(unlock, curr);
337 case ATOMIC_UNLOCK: {
338 /* wake up the other threads */
339 for (unsigned int i = 0;i < get_num_threads();i++) {
340 Thread *t = get_thread(int_to_id(i));
341 Thread *curr_thrd = get_thread(curr);
342 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
346 /* unlock the lock - after checking who was waiting on it */
347 state->locked = NULL;
349 if (!curr->is_wait())
350 break;/* The rest is only for ATOMIC_WAIT */
354 case ATOMIC_NOTIFY_ALL: {
355 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
356 //activate all the waiting threads
357 for (action_list_t::iterator rit = waiters->begin();rit != waiters->end();rit++) {
358 scheduler->wake(get_thread(*rit));
363 case ATOMIC_NOTIFY_ONE: {
364 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
365 if (waiters->size() != 0) {
366 Thread * thread = fuzzer->selectNotify(waiters);
367 scheduler->wake(thread);
379 * Process a write ModelAction
380 * @param curr The ModelAction to process
381 * @return True if the mo_graph was updated or promises were resolved
383 void ModelExecution::process_write(ModelAction *curr)
386 w_modification_order(curr);
389 get_thread(curr)->set_return_value(VALUE_NONE);
393 * Process a fence ModelAction
394 * @param curr The ModelAction to process
395 * @return True if synchronization was updated
397 bool ModelExecution::process_fence(ModelAction *curr)
400 * fence-relaxed: no-op
401 * fence-release: only log the occurence (not in this function), for
402 * use in later synchronization
403 * fence-acquire (this function): search for hypothetical release
405 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
407 bool updated = false;
408 if (curr->is_acquire()) {
409 action_list_t *list = &action_trace;
410 action_list_t::reverse_iterator rit;
411 /* Find X : is_read(X) && X --sb-> curr */
412 for (rit = list->rbegin();rit != list->rend();rit++) {
413 ModelAction *act = *rit;
416 if (act->get_tid() != curr->get_tid())
418 /* Stop at the beginning of the thread */
419 if (act->is_thread_start())
421 /* Stop once we reach a prior fence-acquire */
422 if (act->is_fence() && act->is_acquire())
426 /* read-acquire will find its own release sequences */
427 if (act->is_acquire())
430 /* Establish hypothetical release sequences */
431 rel_heads_list_t release_heads;
432 get_release_seq_heads(curr, act, &release_heads);
433 for (unsigned int i = 0;i < release_heads.size();i++)
434 synchronize(release_heads[i], curr);
435 if (release_heads.size() != 0)
443 * @brief Process the current action for thread-related activity
445 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
446 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
447 * synchronization, etc. This function is a no-op for non-THREAD actions
448 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
450 * @param curr The current action
451 * @return True if synchronization was updated or a thread completed
453 bool ModelExecution::process_thread_action(ModelAction *curr)
455 bool updated = false;
457 switch (curr->get_type()) {
458 case THREAD_CREATE: {
459 thrd_t *thrd = (thrd_t *)curr->get_location();
460 struct thread_params *params = (struct thread_params *)curr->get_value();
461 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
462 curr->set_thread_operand(th);
464 th->set_creation(curr);
467 case PTHREAD_CREATE: {
468 (*(uint32_t *)curr->get_location()) = pthread_counter++;
470 struct pthread_params *params = (struct pthread_params *)curr->get_value();
471 Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
472 curr->set_thread_operand(th);
474 th->set_creation(curr);
476 if ( pthread_map.size() < pthread_counter )
477 pthread_map.resize( pthread_counter );
478 pthread_map[ pthread_counter-1 ] = th;
483 Thread *blocking = curr->get_thread_operand();
484 ModelAction *act = get_last_action(blocking->get_id());
485 synchronize(act, curr);
486 updated = true; /* trigger rel-seq checks */
490 Thread *blocking = curr->get_thread_operand();
491 ModelAction *act = get_last_action(blocking->get_id());
492 synchronize(act, curr);
493 updated = true; /* trigger rel-seq checks */
494 break; // WL: to be add (modified)
497 case THREAD_FINISH: {
498 Thread *th = get_thread(curr);
499 /* Wake up any joining threads */
500 for (unsigned int i = 0;i < get_num_threads();i++) {
501 Thread *waiting = get_thread(int_to_id(i));
502 if (waiting->waiting_on() == th &&
503 waiting->get_pending()->is_thread_join())
504 scheduler->wake(waiting);
507 updated = true; /* trigger rel-seq checks */
521 * Initialize the current action by performing one or more of the following
522 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
523 * in the NodeStack, manipulating backtracking sets, allocating and
524 * initializing clock vectors, and computing the promises to fulfill.
526 * @param curr The current action, as passed from the user context; may be
527 * freed/invalidated after the execution of this function, with a different
528 * action "returned" its place (pass-by-reference)
529 * @return True if curr is a newly-explored action; false otherwise
531 bool ModelExecution::initialize_curr_action(ModelAction **curr)
533 ModelAction *newcurr;
535 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
536 newcurr = process_rmw(*curr);
543 (*curr)->set_seq_number(get_next_seq_num());
545 newcurr = node_stack->explore_action(*curr);
547 /* First restore type and order in case of RMW operation */
548 if ((*curr)->is_rmwr())
549 newcurr->copy_typeandorder(*curr);
551 ASSERT((*curr)->get_location() == newcurr->get_location());
552 newcurr->copy_from_new(*curr);
554 /* Discard duplicate ModelAction; use action from NodeStack */
557 /* Always compute new clock vector */
558 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
561 return false; /* Action was explored previously */
565 /* Always compute new clock vector */
566 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
568 /* Assign most recent release fence */
569 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
571 return true; /* This was a new ModelAction */
576 * @brief Establish reads-from relation between two actions
578 * Perform basic operations involved with establishing a concrete rf relation,
579 * including setting the ModelAction data and checking for release sequences.
581 * @param act The action that is reading (must be a read)
582 * @param rf The action from which we are reading (must be a write)
584 * @return True if this read established synchronization
587 bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
590 ASSERT(rf->is_write());
592 act->set_read_from(rf);
593 if (act->is_acquire()) {
594 rel_heads_list_t release_heads;
595 get_release_seq_heads(act, act, &release_heads);
596 int num_heads = release_heads.size();
597 for (unsigned int i = 0;i < release_heads.size();i++)
598 if (!synchronize(release_heads[i], act))
600 return num_heads > 0;
606 * @brief Synchronizes two actions
608 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
609 * This function performs the synchronization as well as providing other hooks
610 * for other checks along with synchronization.
612 * @param first The left-hand side of the synchronizes-with relation
613 * @param second The right-hand side of the synchronizes-with relation
614 * @return True if the synchronization was successful (i.e., was consistent
615 * with the execution order); false otherwise
617 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
619 if (*second < *first) {
620 set_bad_synchronization();
623 return second->synchronize_with(first);
627 * @brief Check whether a model action is enabled.
629 * Checks whether an operation would be successful (i.e., is a lock already
630 * locked, or is the joined thread already complete).
632 * For yield-blocking, yields are never enabled.
634 * @param curr is the ModelAction to check whether it is enabled.
635 * @return a bool that indicates whether the action is enabled.
637 bool ModelExecution::check_action_enabled(ModelAction *curr) {
638 if (curr->is_lock()) {
639 cdsc::mutex *lock = curr->get_mutex();
640 struct cdsc::mutex_state *state = lock->get_state();
643 } else if (curr->is_thread_join()) {
644 Thread *blocking = curr->get_thread_operand();
645 if (!blocking->is_complete()) {
654 * This is the heart of the model checker routine. It performs model-checking
655 * actions corresponding to a given "current action." Among other processes, it
656 * calculates reads-from relationships, updates synchronization clock vectors,
657 * forms a memory_order constraints graph, and handles replay/backtrack
658 * execution when running permutations of previously-observed executions.
660 * @param curr The current action to process
661 * @return The ModelAction that is actually executed; may be different than
664 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
667 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
668 bool newly_explored = initialize_curr_action(&curr);
672 wake_up_sleeping_actions(curr);
674 /* Add the action to lists before any other model-checking tasks */
675 if (!second_part_of_rmw && curr->get_type() != NOOP)
676 add_action_to_lists(curr);
678 SnapVector<const ModelAction *> * rf_set = NULL;
679 /* Build may_read_from set for newly-created actions */
680 if (newly_explored && curr->is_read())
681 rf_set = build_may_read_from(curr);
683 process_thread_action(curr);
685 if (curr->is_read() && !second_part_of_rmw) {
686 process_read(curr, rf_set);
689 ASSERT(rf_set == NULL);
692 if (curr->is_write())
695 if (curr->is_fence())
698 if (curr->is_mutex_op())
705 * This is the strongest feasibility check available.
706 * @return whether the current trace (partial or complete) must be a prefix of
709 bool ModelExecution::isfeasibleprefix() const
711 return !is_infeasible();
715 * Print disagnostic information about an infeasible execution
716 * @param prefix A string to prefix the output with; if NULL, then a default
717 * message prefix will be provided
719 void ModelExecution::print_infeasibility(const char *prefix) const
723 if (priv->bad_synchronization)
724 ptr += sprintf(ptr, "[bad sw ordering]");
726 model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
730 * Check if the current partial trace is infeasible. Does not check any
731 * end-of-execution flags, which might rule out the execution. Thus, this is
732 * useful only for ruling an execution as infeasible.
733 * @return whether the current partial trace is infeasible.
735 bool ModelExecution::is_infeasible() const
737 return priv->bad_synchronization;
740 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
741 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
742 ModelAction *lastread = get_last_action(act->get_tid());
743 lastread->process_rmw(act);
745 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
751 * @brief Updates the mo_graph with the constraints imposed from the current
754 * Basic idea is the following: Go through each other thread and find
755 * the last action that happened before our read. Two cases:
757 * -# The action is a write: that write must either occur before
758 * the write we read from or be the write we read from.
759 * -# The action is a read: the write that that action read from
760 * must occur before the write we read from or be the same write.
762 * @param curr The current action. Must be a read.
763 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
764 * @return True if modification order edges were added; false otherwise
767 bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf, SnapVector<const ModelAction *> * priorset)
769 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
771 ASSERT(curr->is_read());
773 /* Last SC fence in the current thread */
774 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
775 ModelAction *last_sc_write = NULL;
776 if (curr->is_seqcst())
777 last_sc_write = get_last_seq_cst_write(curr);
779 /* Iterate over all threads */
780 for (i = 0;i < thrd_lists->size();i++) {
781 /* Last SC fence in thread i */
782 ModelAction *last_sc_fence_thread_local = NULL;
783 if (int_to_id((int)i) != curr->get_tid())
784 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
786 /* Last SC fence in thread i, before last SC fence in current thread */
787 ModelAction *last_sc_fence_thread_before = NULL;
788 if (last_sc_fence_local)
789 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
791 /* Iterate over actions in thread, starting from most recent */
792 action_list_t *list = &(*thrd_lists)[i];
793 action_list_t::reverse_iterator rit;
794 for (rit = list->rbegin();rit != list->rend();rit++) {
795 ModelAction *act = *rit;
800 /* Don't want to add reflexive edges on 'rf' */
801 if (act->equals(rf)) {
802 if (act->happens_before(curr))
808 if (act->is_write()) {
809 /* C++, Section 29.3 statement 5 */
810 if (curr->is_seqcst() && last_sc_fence_thread_local &&
811 *act < *last_sc_fence_thread_local) {
812 if (mo_graph->checkReachable(rf, act))
814 priorset->push_back(act);
817 /* C++, Section 29.3 statement 4 */
818 else if (act->is_seqcst() && last_sc_fence_local &&
819 *act < *last_sc_fence_local) {
820 if (mo_graph->checkReachable(rf, act))
822 priorset->push_back(act);
825 /* C++, Section 29.3 statement 6 */
826 else if (last_sc_fence_thread_before &&
827 *act < *last_sc_fence_thread_before) {
828 if (mo_graph->checkReachable(rf, act))
830 priorset->push_back(act);
836 * Include at most one act per-thread that "happens
839 if (act->happens_before(curr)) {
840 if (act->is_write()) {
841 if (mo_graph->checkReachable(rf, act))
843 priorset->push_back(act);
845 const ModelAction *prevrf = act->get_reads_from();
846 if (!prevrf->equals(rf)) {
847 if (mo_graph->checkReachable(rf, prevrf))
849 priorset->push_back(prevrf);
860 * Updates the mo_graph with the constraints imposed from the current write.
862 * Basic idea is the following: Go through each other thread and find
863 * the lastest action that happened before our write. Two cases:
865 * (1) The action is a write => that write must occur before
868 * (2) The action is a read => the write that that action read from
869 * must occur before the current write.
871 * This method also handles two other issues:
873 * (I) Sequential Consistency: Making sure that if the current write is
874 * seq_cst, that it occurs after the previous seq_cst write.
876 * (II) Sending the write back to non-synchronizing reads.
878 * @param curr The current action. Must be a write.
879 * @param send_fv A vector for stashing reads to which we may pass our future
880 * value. If NULL, then don't record any future values.
881 * @return True if modification order edges were added; false otherwise
883 void ModelExecution::w_modification_order(ModelAction *curr)
885 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
887 ASSERT(curr->is_write());
889 if (curr->is_seqcst()) {
890 /* We have to at least see the last sequentially consistent write,
891 so we are initialized. */
892 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
893 if (last_seq_cst != NULL) {
894 mo_graph->addEdge(last_seq_cst, curr);
898 /* Last SC fence in the current thread */
899 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
901 /* Iterate over all threads */
902 for (i = 0;i < thrd_lists->size();i++) {
903 /* Last SC fence in thread i, before last SC fence in current thread */
904 ModelAction *last_sc_fence_thread_before = NULL;
905 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
906 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
908 /* Iterate over actions in thread, starting from most recent */
909 action_list_t *list = &(*thrd_lists)[i];
910 action_list_t::reverse_iterator rit;
911 bool force_edge = false;
912 for (rit = list->rbegin();rit != list->rend();rit++) {
913 ModelAction *act = *rit;
916 * 1) If RMW and it actually read from something, then we
917 * already have all relevant edges, so just skip to next
920 * 2) If RMW and it didn't read from anything, we should
921 * whatever edge we can get to speed up convergence.
923 * 3) If normal write, we need to look at earlier actions, so
924 * continue processing list.
927 if (curr->is_rmw()) {
928 if (curr->get_reads_from() != NULL)
936 /* C++, Section 29.3 statement 7 */
937 if (last_sc_fence_thread_before && act->is_write() &&
938 *act < *last_sc_fence_thread_before) {
939 mo_graph->addEdge(act, curr, force_edge);
944 * Include at most one act per-thread that "happens
947 if (act->happens_before(curr)) {
949 * Note: if act is RMW, just add edge:
951 * The following edge should be handled elsewhere:
952 * readfrom(act) --mo--> act
955 mo_graph->addEdge(act, curr, force_edge);
956 else if (act->is_read()) {
957 //if previous read accessed a null, just keep going
958 mo_graph->addEdge(act->get_reads_from(), curr, force_edge);
961 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
962 !act->same_thread(curr)) {
963 /* We have an action that:
964 (1) did not happen before us
965 (2) is a read and we are a write
966 (3) cannot synchronize with us
967 (4) is in a different thread
969 that read could potentially read from our write. Note that
970 these checks are overly conservative at this point, we'll
971 do more checks before actually removing the
982 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
983 * some constraints. This method checks one the following constraint (others
984 * require compiler support):
986 * If X --hb-> Y --mo-> Z, then X should not read from Z.
987 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
989 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
991 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
993 /* Iterate over all threads */
994 for (i = 0;i < thrd_lists->size();i++) {
995 const ModelAction *write_after_read = NULL;
997 /* Iterate over actions in thread, starting from most recent */
998 action_list_t *list = &(*thrd_lists)[i];
999 action_list_t::reverse_iterator rit;
1000 for (rit = list->rbegin();rit != list->rend();rit++) {
1001 ModelAction *act = *rit;
1003 /* Don't disallow due to act == reader */
1004 if (!reader->happens_before(act) || reader == act)
1006 else if (act->is_write())
1007 write_after_read = act;
1008 else if (act->is_read() && act->get_reads_from() != NULL)
1009 write_after_read = act->get_reads_from();
1012 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1019 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1020 * The ModelAction under consideration is expected to be taking part in
1021 * release/acquire synchronization as an object of the "reads from" relation.
1022 * Note that this can only provide release sequence support for RMW chains
1023 * which do not read from the future, as those actions cannot be traced until
1024 * their "promise" is fulfilled. Similarly, we may not even establish the
1025 * presence of a release sequence with certainty, as some modification order
1026 * constraints may be decided further in the future. Thus, this function
1027 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1028 * and a boolean representing certainty.
1030 * @param rf The action that might be part of a release sequence. Must be a
1032 * @param release_heads A pass-by-reference style return parameter. After
1033 * execution of this function, release_heads will contain the heads of all the
1034 * relevant release sequences, if any exists with certainty
1035 * @return true, if the ModelExecution is certain that release_heads is complete;
1038 bool ModelExecution::release_seq_heads(const ModelAction *rf, rel_heads_list_t *release_heads) const
1041 for ( ;rf != NULL;rf = rf->get_reads_from()) {
1042 ASSERT(rf->is_write());
1044 if (rf->is_release())
1045 release_heads->push_back(rf);
1046 else if (rf->get_last_fence_release())
1047 release_heads->push_back(rf->get_last_fence_release());
1049 break;/* End of RMW chain */
1051 /** @todo Need to be smarter here... In the linux lock
1052 * example, this will run to the beginning of the program for
1054 /** @todo The way to be smarter here is to keep going until 1
1055 * thread has a release preceded by an acquire and you've seen
1058 /* acq_rel RMW is a sufficient stopping condition */
1059 if (rf->is_acquire() && rf->is_release())
1060 return true;/* complete */
1062 ASSERT(rf); // Needs to be real write
1064 if (rf->is_release())
1065 return true;/* complete */
1067 /* else relaxed write
1068 * - check for fence-release in the same thread (29.8, stmt. 3)
1069 * - check modification order for contiguous subsequence
1070 * -> rf must be same thread as release */
1072 const ModelAction *fence_release = rf->get_last_fence_release();
1073 /* Synchronize with a fence-release unconditionally; we don't need to
1074 * find any more "contiguous subsequence..." for it */
1076 release_heads->push_back(fence_release);
1078 return true; /* complete */
1082 * An interface for getting the release sequence head(s) with which a
1083 * given ModelAction must synchronize. This function only returns a non-empty
1084 * result when it can locate a release sequence head with certainty. Otherwise,
1085 * it may mark the internal state of the ModelExecution so that it will handle
1086 * the release sequence at a later time, causing @a acquire to update its
1087 * synchronization at some later point in execution.
1089 * @param acquire The 'acquire' action that may synchronize with a release
1091 * @param read The read action that may read from a release sequence; this may
1092 * be the same as acquire, or else an earlier action in the same thread (i.e.,
1093 * when 'acquire' is a fence-acquire)
1094 * @param release_heads A pass-by-reference return parameter. Will be filled
1095 * with the head(s) of the release sequence(s), if they exists with certainty.
1096 * @see ModelExecution::release_seq_heads
1098 void ModelExecution::get_release_seq_heads(ModelAction *acquire,
1099 ModelAction *read, rel_heads_list_t *release_heads)
1101 const ModelAction *rf = read->get_reads_from();
1103 release_seq_heads(rf, release_heads);
1107 * Performs various bookkeeping operations for the current ModelAction. For
1108 * instance, adds action to the per-object, per-thread action vector and to the
1109 * action trace list of all thread actions.
1111 * @param act is the ModelAction to add.
1113 void ModelExecution::add_action_to_lists(ModelAction *act)
1115 int tid = id_to_int(act->get_tid());
1116 ModelAction *uninit = NULL;
1118 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1119 if (list->empty() && act->is_atomic_var()) {
1120 uninit = get_uninitialized_action(act);
1121 uninit_id = id_to_int(uninit->get_tid());
1122 list->push_front(uninit);
1124 list->push_back(act);
1126 action_trace.push_back(act);
1128 action_trace.push_front(uninit);
1130 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1131 if (tid >= (int)vec->size())
1132 vec->resize(priv->next_thread_id);
1133 (*vec)[tid].push_back(act);
1135 (*vec)[uninit_id].push_front(uninit);
1137 if ((int)thrd_last_action.size() <= tid)
1138 thrd_last_action.resize(get_num_threads());
1139 thrd_last_action[tid] = act;
1141 thrd_last_action[uninit_id] = uninit;
1143 if (act->is_fence() && act->is_release()) {
1144 if ((int)thrd_last_fence_release.size() <= tid)
1145 thrd_last_fence_release.resize(get_num_threads());
1146 thrd_last_fence_release[tid] = act;
1149 if (act->is_wait()) {
1150 void *mutex_loc = (void *) act->get_value();
1151 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
1153 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
1154 if (tid >= (int)vec->size())
1155 vec->resize(priv->next_thread_id);
1156 (*vec)[tid].push_back(act);
1161 * @brief Get the last action performed by a particular Thread
1162 * @param tid The thread ID of the Thread in question
1163 * @return The last action in the thread
1165 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
1167 int threadid = id_to_int(tid);
1168 if (threadid < (int)thrd_last_action.size())
1169 return thrd_last_action[id_to_int(tid)];
1175 * @brief Get the last fence release performed by a particular Thread
1176 * @param tid The thread ID of the Thread in question
1177 * @return The last fence release in the thread, if one exists; NULL otherwise
1179 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
1181 int threadid = id_to_int(tid);
1182 if (threadid < (int)thrd_last_fence_release.size())
1183 return thrd_last_fence_release[id_to_int(tid)];
1189 * Gets the last memory_order_seq_cst write (in the total global sequence)
1190 * performed on a particular object (i.e., memory location), not including the
1192 * @param curr The current ModelAction; also denotes the object location to
1194 * @return The last seq_cst write
1196 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
1198 void *location = curr->get_location();
1199 action_list_t *list = obj_map.get(location);
1200 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1201 action_list_t::reverse_iterator rit;
1202 for (rit = list->rbegin();(*rit) != curr;rit++)
1204 rit++; /* Skip past curr */
1205 for ( ;rit != list->rend();rit++)
1206 if ((*rit)->is_write() && (*rit)->is_seqcst())
1212 * Gets the last memory_order_seq_cst fence (in the total global sequence)
1213 * performed in a particular thread, prior to a particular fence.
1214 * @param tid The ID of the thread to check
1215 * @param before_fence The fence from which to begin the search; if NULL, then
1216 * search for the most recent fence in the thread.
1217 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
1219 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
1221 /* All fences should have location FENCE_LOCATION */
1222 action_list_t *list = obj_map.get(FENCE_LOCATION);
1227 action_list_t::reverse_iterator rit = list->rbegin();
1230 for (;rit != list->rend();rit++)
1231 if (*rit == before_fence)
1234 ASSERT(*rit == before_fence);
1238 for (;rit != list->rend();rit++)
1239 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
1245 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1246 * location). This function identifies the mutex according to the current
1247 * action, which is presumed to perform on the same mutex.
1248 * @param curr The current ModelAction; also denotes the object location to
1250 * @return The last unlock operation
1252 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
1254 void *location = curr->get_location();
1256 action_list_t *list = obj_map.get(location);
1257 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1258 action_list_t::reverse_iterator rit;
1259 for (rit = list->rbegin();rit != list->rend();rit++)
1260 if ((*rit)->is_unlock() || (*rit)->is_wait())
1265 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
1267 ModelAction *parent = get_last_action(tid);
1269 parent = get_thread(tid)->get_creation();
1274 * Returns the clock vector for a given thread.
1275 * @param tid The thread whose clock vector we want
1276 * @return Desired clock vector
1278 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
1280 return get_parent_action(tid)->get_cv();
1283 bool valequals(uint64_t val1, uint64_t val2, int size) {
1286 return ((uint8_t)val1) == ((uint8_t)val2);
1288 return ((uint16_t)val1) == ((uint16_t)val2);
1290 return ((uint32_t)val1) == ((uint32_t)val2);
1300 * Build up an initial set of all past writes that this 'read' action may read
1301 * from, as well as any previously-observed future values that must still be valid.
1303 * @param curr is the current ModelAction that we are exploring; it must be a
1306 SnapVector<const ModelAction *> * ModelExecution::build_may_read_from(ModelAction *curr)
1308 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1310 ASSERT(curr->is_read());
1312 ModelAction *last_sc_write = NULL;
1314 if (curr->is_seqcst())
1315 last_sc_write = get_last_seq_cst_write(curr);
1317 SnapVector<const ModelAction *> * rf_set = new SnapVector<const ModelAction *>();
1319 /* Iterate over all threads */
1320 for (i = 0;i < thrd_lists->size();i++) {
1321 /* Iterate over actions in thread, starting from most recent */
1322 action_list_t *list = &(*thrd_lists)[i];
1323 action_list_t::reverse_iterator rit;
1324 for (rit = list->rbegin();rit != list->rend();rit++) {
1325 const ModelAction *act = *rit;
1327 /* Only consider 'write' actions */
1328 if (!act->is_write()) {
1329 if (act != curr && act->is_read() && act->happens_before(curr)) {
1330 const ModelAction *tmp = act->get_reads_from();
1331 if (((unsigned int) id_to_int(tmp->get_tid()))==i)
1342 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1343 bool allow_read = true;
1345 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
1348 /* Need to check whether we will have two RMW reading from the same value */
1349 if (curr->is_rmwr()) {
1350 /* It is okay if we have a failing CAS */
1351 if (!curr->is_rmwrcas() ||
1352 valequals(curr->get_value(), act->get_value(), curr->getSize())) {
1353 //Need to make sure we aren't the second RMW
1354 CycleNode * node = mo_graph->getNode_noCreate(act);
1355 if (node != NULL && node->getRMW() != NULL) {
1356 //we are the second RMW
1363 /* Only add feasible reads */
1364 rf_set->push_back(act);
1367 /* Include at most one act per-thread that "happens before" curr */
1368 if (act->happens_before(curr))
1373 if (DBG_ENABLED()) {
1374 model_print("Reached read action:\n");
1376 model_print("End printing read_from_past\n");
1382 * @brief Get an action representing an uninitialized atomic
1384 * This function may create a new one or try to retrieve one from the NodeStack
1386 * @param curr The current action, which prompts the creation of an UNINIT action
1387 * @return A pointer to the UNINIT ModelAction
1389 ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
1391 Node *node = curr->get_node();
1392 ModelAction *act = node->get_uninit_action();
1394 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
1395 node->set_uninit_action(act);
1397 act->create_cv(NULL);
1401 static void print_list(const action_list_t *list)
1403 action_list_t::const_iterator it;
1405 model_print("------------------------------------------------------------------------------------\n");
1406 model_print("# t Action type MO Location Value Rf CV\n");
1407 model_print("------------------------------------------------------------------------------------\n");
1409 unsigned int hash = 0;
1411 for (it = list->begin();it != list->end();it++) {
1412 const ModelAction *act = *it;
1413 if (act->get_seq_number() > 0)
1415 hash = hash^(hash<<3)^((*it)->hash());
1417 model_print("HASH %u\n", hash);
1418 model_print("------------------------------------------------------------------------------------\n");
1421 #if SUPPORT_MOD_ORDER_DUMP
1422 void ModelExecution::dumpGraph(char *filename) const
1425 sprintf(buffer, "%s.dot", filename);
1426 FILE *file = fopen(buffer, "w");
1427 fprintf(file, "digraph %s {\n", filename);
1428 mo_graph->dumpNodes(file);
1429 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
1431 for (action_list_t::const_iterator it = action_trace.begin();it != action_trace.end();it++) {
1432 ModelAction *act = *it;
1433 if (act->is_read()) {
1434 mo_graph->dot_print_node(file, act);
1435 mo_graph->dot_print_edge(file,
1436 act->get_reads_from(),
1438 "label=\"rf\", color=red, weight=2");
1440 if (thread_array[act->get_tid()]) {
1441 mo_graph->dot_print_edge(file,
1442 thread_array[id_to_int(act->get_tid())],
1444 "label=\"sb\", color=blue, weight=400");
1447 thread_array[act->get_tid()] = act;
1449 fprintf(file, "}\n");
1450 model_free(thread_array);
1455 /** @brief Prints an execution trace summary. */
1456 void ModelExecution::print_summary() const
1458 #if SUPPORT_MOD_ORDER_DUMP
1459 char buffername[100];
1460 sprintf(buffername, "exec%04u", get_execution_number());
1461 mo_graph->dumpGraphToFile(buffername);
1462 sprintf(buffername, "graph%04u", get_execution_number());
1463 dumpGraph(buffername);
1466 model_print("Execution trace %d:", get_execution_number());
1467 if (isfeasibleprefix()) {
1468 if (scheduler->all_threads_sleeping())
1469 model_print(" SLEEP-SET REDUNDANT");
1470 if (have_bug_reports())
1471 model_print(" DETECTED BUG(S)");
1473 print_infeasibility(" INFEASIBLE");
1476 print_list(&action_trace);
1482 * Add a Thread to the system for the first time. Should only be called once
1484 * @param t The Thread to add
1486 void ModelExecution::add_thread(Thread *t)
1488 unsigned int i = id_to_int(t->get_id());
1489 if (i >= thread_map.size())
1490 thread_map.resize(i + 1);
1492 if (!t->is_model_thread())
1493 scheduler->add_thread(t);
1497 * @brief Get a Thread reference by its ID
1498 * @param tid The Thread's ID
1499 * @return A Thread reference
1501 Thread * ModelExecution::get_thread(thread_id_t tid) const
1503 unsigned int i = id_to_int(tid);
1504 if (i < thread_map.size())
1505 return thread_map[i];
1510 * @brief Get a reference to the Thread in which a ModelAction was executed
1511 * @param act The ModelAction
1512 * @return A Thread reference
1514 Thread * ModelExecution::get_thread(const ModelAction *act) const
1516 return get_thread(act->get_tid());
1520 * @brief Get a Thread reference by its pthread ID
1521 * @param index The pthread's ID
1522 * @return A Thread reference
1524 Thread * ModelExecution::get_pthread(pthread_t pid) {
1530 uint32_t thread_id = x.v;
1531 if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
1536 * @brief Check if a Thread is currently enabled
1537 * @param t The Thread to check
1538 * @return True if the Thread is currently enabled
1540 bool ModelExecution::is_enabled(Thread *t) const
1542 return scheduler->is_enabled(t);
1546 * @brief Check if a Thread is currently enabled
1547 * @param tid The ID of the Thread to check
1548 * @return True if the Thread is currently enabled
1550 bool ModelExecution::is_enabled(thread_id_t tid) const
1552 return scheduler->is_enabled(tid);
1556 * @brief Select the next thread to execute based on the curren action
1558 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
1559 * actions should be followed by the execution of their child thread. In either
1560 * case, the current action should determine the next thread schedule.
1562 * @param curr The current action
1563 * @return The next thread to run, if the current action will determine this
1564 * selection; otherwise NULL
1566 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
1568 /* Do not split atomic RMW */
1569 if (curr->is_rmwr())
1570 return get_thread(curr);
1571 if (curr->is_write()) {
1572 std::memory_order order = curr->get_mo();
1574 case std::memory_order_relaxed:
1575 return get_thread(curr);
1576 case std::memory_order_release:
1577 return get_thread(curr);
1583 /* Follow CREATE with the created thread */
1584 /* which is not needed, because model.cc takes care of this */
1585 if (curr->get_type() == THREAD_CREATE)
1586 return curr->get_thread_operand();
1587 if (curr->get_type() == PTHREAD_CREATE) {
1588 return curr->get_thread_operand();
1594 * Takes the next step in the execution, if possible.
1595 * @param curr The current step to take
1596 * @return Returns the next Thread to run, if any; NULL if this execution
1599 Thread * ModelExecution::take_step(ModelAction *curr)
1601 Thread *curr_thrd = get_thread(curr);
1602 ASSERT(curr_thrd->get_state() == THREAD_READY);
1604 ASSERT(check_action_enabled(curr)); /* May have side effects? */
1605 curr = check_current_action(curr);
1608 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
1609 scheduler->remove_thread(curr_thrd);
1611 return action_select_next_thread(curr);
1614 Fuzzer * ModelExecution::getFuzzer() {