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];
273 bool canprune = false;
274 if (r_modification_order(curr, rf, priorset, &canprune)) {
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());
281 if (canprune && curr->get_type() == ATOMIC_READ) {
282 int tid = id_to_int(curr->get_tid());
283 (*obj_thrd_map.get(curr->get_location()))[tid].pop_back();
288 (*rf_set)[index] = rf_set->back();
294 * Processes a lock, trylock, or unlock model action. @param curr is
295 * the read model action to process.
297 * The try lock operation checks whether the lock is taken. If not,
298 * it falls to the normal lock operation case. If so, it returns
301 * The lock operation has already been checked that it is enabled, so
302 * it just grabs the lock and synchronizes with the previous unlock.
304 * The unlock operation has to re-enable all of the threads that are
305 * waiting on the lock.
307 * @return True if synchronization was updated; false otherwise
309 bool ModelExecution::process_mutex(ModelAction *curr)
311 cdsc::mutex *mutex = curr->get_mutex();
312 struct cdsc::mutex_state *state = NULL;
315 state = mutex->get_state();
317 switch (curr->get_type()) {
318 case ATOMIC_TRYLOCK: {
319 bool success = !state->locked;
320 curr->set_try_lock(success);
322 get_thread(curr)->set_return_value(0);
325 get_thread(curr)->set_return_value(1);
327 //otherwise fall into the lock case
329 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
330 assert_bug("Lock access before initialization");
331 state->locked = get_thread(curr);
332 ModelAction *unlock = get_last_unlock(curr);
333 //synchronize with the previous unlock statement
334 if (unlock != NULL) {
335 synchronize(unlock, curr);
341 case ATOMIC_UNLOCK: {
342 /* wake up the other threads */
343 for (unsigned int i = 0;i < get_num_threads();i++) {
344 Thread *t = get_thread(int_to_id(i));
345 Thread *curr_thrd = get_thread(curr);
346 if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
350 /* unlock the lock - after checking who was waiting on it */
351 state->locked = NULL;
353 if (!curr->is_wait())
354 break;/* The rest is only for ATOMIC_WAIT */
358 case ATOMIC_NOTIFY_ALL: {
359 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
360 //activate all the waiting threads
361 for (action_list_t::iterator rit = waiters->begin();rit != waiters->end();rit++) {
362 scheduler->wake(get_thread(*rit));
367 case ATOMIC_NOTIFY_ONE: {
368 action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
369 if (waiters->size() != 0) {
370 Thread * thread = fuzzer->selectNotify(waiters);
371 scheduler->wake(thread);
383 * Process a write ModelAction
384 * @param curr The ModelAction to process
385 * @return True if the mo_graph was updated or promises were resolved
387 void ModelExecution::process_write(ModelAction *curr)
390 w_modification_order(curr);
393 get_thread(curr)->set_return_value(VALUE_NONE);
397 * Process a fence ModelAction
398 * @param curr The ModelAction to process
399 * @return True if synchronization was updated
401 bool ModelExecution::process_fence(ModelAction *curr)
404 * fence-relaxed: no-op
405 * fence-release: only log the occurence (not in this function), for
406 * use in later synchronization
407 * fence-acquire (this function): search for hypothetical release
409 * fence-seq-cst: MO constraints formed in {r,w}_modification_order
411 bool updated = false;
412 if (curr->is_acquire()) {
413 action_list_t *list = &action_trace;
414 action_list_t::reverse_iterator rit;
415 /* Find X : is_read(X) && X --sb-> curr */
416 for (rit = list->rbegin();rit != list->rend();rit++) {
417 ModelAction *act = *rit;
420 if (act->get_tid() != curr->get_tid())
422 /* Stop at the beginning of the thread */
423 if (act->is_thread_start())
425 /* Stop once we reach a prior fence-acquire */
426 if (act->is_fence() && act->is_acquire())
430 /* read-acquire will find its own release sequences */
431 if (act->is_acquire())
434 /* Establish hypothetical release sequences */
435 rel_heads_list_t release_heads;
436 get_release_seq_heads(curr, act, &release_heads);
437 for (unsigned int i = 0;i < release_heads.size();i++)
438 synchronize(release_heads[i], curr);
439 if (release_heads.size() != 0)
447 * @brief Process the current action for thread-related activity
449 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
450 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
451 * synchronization, etc. This function is a no-op for non-THREAD actions
452 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
454 * @param curr The current action
455 * @return True if synchronization was updated or a thread completed
457 bool ModelExecution::process_thread_action(ModelAction *curr)
459 bool updated = false;
461 switch (curr->get_type()) {
462 case THREAD_CREATE: {
463 thrd_t *thrd = (thrd_t *)curr->get_location();
464 struct thread_params *params = (struct thread_params *)curr->get_value();
465 Thread *th = new Thread(get_next_id(), thrd, params->func, params->arg, get_thread(curr));
466 curr->set_thread_operand(th);
468 th->set_creation(curr);
471 case PTHREAD_CREATE: {
472 (*(uint32_t *)curr->get_location()) = pthread_counter++;
474 struct pthread_params *params = (struct pthread_params *)curr->get_value();
475 Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
476 curr->set_thread_operand(th);
478 th->set_creation(curr);
480 if ( pthread_map.size() < pthread_counter )
481 pthread_map.resize( pthread_counter );
482 pthread_map[ pthread_counter-1 ] = th;
487 Thread *blocking = curr->get_thread_operand();
488 ModelAction *act = get_last_action(blocking->get_id());
489 synchronize(act, curr);
490 updated = true; /* trigger rel-seq checks */
494 Thread *blocking = curr->get_thread_operand();
495 ModelAction *act = get_last_action(blocking->get_id());
496 synchronize(act, curr);
497 updated = true; /* trigger rel-seq checks */
498 break; // WL: to be add (modified)
501 case THREAD_FINISH: {
502 Thread *th = get_thread(curr);
503 /* Wake up any joining threads */
504 for (unsigned int i = 0;i < get_num_threads();i++) {
505 Thread *waiting = get_thread(int_to_id(i));
506 if (waiting->waiting_on() == th &&
507 waiting->get_pending()->is_thread_join())
508 scheduler->wake(waiting);
511 updated = true; /* trigger rel-seq checks */
525 * Initialize the current action by performing one or more of the following
526 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
527 * in the NodeStack, manipulating backtracking sets, allocating and
528 * initializing clock vectors, and computing the promises to fulfill.
530 * @param curr The current action, as passed from the user context; may be
531 * freed/invalidated after the execution of this function, with a different
532 * action "returned" its place (pass-by-reference)
533 * @return True if curr is a newly-explored action; false otherwise
535 bool ModelExecution::initialize_curr_action(ModelAction **curr)
537 ModelAction *newcurr;
539 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
540 newcurr = process_rmw(*curr);
547 (*curr)->set_seq_number(get_next_seq_num());
549 newcurr = node_stack->explore_action(*curr);
551 /* First restore type and order in case of RMW operation */
552 if ((*curr)->is_rmwr())
553 newcurr->copy_typeandorder(*curr);
555 ASSERT((*curr)->get_location() == newcurr->get_location());
556 newcurr->copy_from_new(*curr);
558 /* Discard duplicate ModelAction; use action from NodeStack */
561 /* Always compute new clock vector */
562 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
565 return false; /* Action was explored previously */
569 /* Always compute new clock vector */
570 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
572 /* Assign most recent release fence */
573 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
575 return true; /* This was a new ModelAction */
580 * @brief Establish reads-from relation between two actions
582 * Perform basic operations involved with establishing a concrete rf relation,
583 * including setting the ModelAction data and checking for release sequences.
585 * @param act The action that is reading (must be a read)
586 * @param rf The action from which we are reading (must be a write)
588 * @return True if this read established synchronization
591 bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
594 ASSERT(rf->is_write());
596 act->set_read_from(rf);
597 if (act->is_acquire()) {
598 rel_heads_list_t release_heads;
599 get_release_seq_heads(act, act, &release_heads);
600 int num_heads = release_heads.size();
601 for (unsigned int i = 0;i < release_heads.size();i++)
602 if (!synchronize(release_heads[i], act))
604 return num_heads > 0;
610 * @brief Synchronizes two actions
612 * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
613 * This function performs the synchronization as well as providing other hooks
614 * for other checks along with synchronization.
616 * @param first The left-hand side of the synchronizes-with relation
617 * @param second The right-hand side of the synchronizes-with relation
618 * @return True if the synchronization was successful (i.e., was consistent
619 * with the execution order); false otherwise
621 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
623 if (*second < *first) {
624 set_bad_synchronization();
627 return second->synchronize_with(first);
631 * @brief Check whether a model action is enabled.
633 * Checks whether an operation would be successful (i.e., is a lock already
634 * locked, or is the joined thread already complete).
636 * For yield-blocking, yields are never enabled.
638 * @param curr is the ModelAction to check whether it is enabled.
639 * @return a bool that indicates whether the action is enabled.
641 bool ModelExecution::check_action_enabled(ModelAction *curr) {
642 if (curr->is_lock()) {
643 cdsc::mutex *lock = curr->get_mutex();
644 struct cdsc::mutex_state *state = lock->get_state();
647 } else if (curr->is_thread_join()) {
648 Thread *blocking = curr->get_thread_operand();
649 if (!blocking->is_complete()) {
658 * This is the heart of the model checker routine. It performs model-checking
659 * actions corresponding to a given "current action." Among other processes, it
660 * calculates reads-from relationships, updates synchronization clock vectors,
661 * forms a memory_order constraints graph, and handles replay/backtrack
662 * execution when running permutations of previously-observed executions.
664 * @param curr The current action to process
665 * @return The ModelAction that is actually executed; may be different than
668 ModelAction * ModelExecution::check_current_action(ModelAction *curr)
671 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
672 bool newly_explored = initialize_curr_action(&curr);
676 wake_up_sleeping_actions(curr);
678 /* Add the action to lists before any other model-checking tasks */
679 if (!second_part_of_rmw && curr->get_type() != NOOP)
680 add_action_to_lists(curr);
682 SnapVector<const ModelAction *> * rf_set = NULL;
683 /* Build may_read_from set for newly-created actions */
684 if (newly_explored && curr->is_read())
685 rf_set = build_may_read_from(curr);
687 process_thread_action(curr);
689 if (curr->is_read() && !second_part_of_rmw) {
690 process_read(curr, rf_set);
693 ASSERT(rf_set == NULL);
696 if (curr->is_write())
699 if (curr->is_fence())
702 if (curr->is_mutex_op())
709 * This is the strongest feasibility check available.
710 * @return whether the current trace (partial or complete) must be a prefix of
713 bool ModelExecution::isfeasibleprefix() const
715 return !is_infeasible();
719 * Print disagnostic information about an infeasible execution
720 * @param prefix A string to prefix the output with; if NULL, then a default
721 * message prefix will be provided
723 void ModelExecution::print_infeasibility(const char *prefix) const
727 if (priv->bad_synchronization)
728 ptr += sprintf(ptr, "[bad sw ordering]");
730 model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
734 * Check if the current partial trace is infeasible. Does not check any
735 * end-of-execution flags, which might rule out the execution. Thus, this is
736 * useful only for ruling an execution as infeasible.
737 * @return whether the current partial trace is infeasible.
739 bool ModelExecution::is_infeasible() const
741 return priv->bad_synchronization;
744 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
745 ModelAction * ModelExecution::process_rmw(ModelAction *act) {
746 ModelAction *lastread = get_last_action(act->get_tid());
747 lastread->process_rmw(act);
749 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
755 * @brief Updates the mo_graph with the constraints imposed from the current
758 * Basic idea is the following: Go through each other thread and find
759 * the last action that happened before our read. Two cases:
761 * -# The action is a write: that write must either occur before
762 * the write we read from or be the write we read from.
763 * -# The action is a read: the write that that action read from
764 * must occur before the write we read from or be the same write.
766 * @param curr The current action. Must be a read.
767 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
768 * @return True if modification order edges were added; false otherwise
771 bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf, SnapVector<const ModelAction *> * priorset, bool * canprune)
773 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
775 ASSERT(curr->is_read());
777 /* Last SC fence in the current thread */
778 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
779 ModelAction *last_sc_write = NULL;
780 if (curr->is_seqcst())
781 last_sc_write = get_last_seq_cst_write(curr);
783 /* Iterate over all threads */
784 for (i = 0;i < thrd_lists->size();i++) {
785 /* Last SC fence in thread i */
786 ModelAction *last_sc_fence_thread_local = NULL;
787 if (int_to_id((int)i) != curr->get_tid())
788 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
790 /* Last SC fence in thread i, before last SC fence in current thread */
791 ModelAction *last_sc_fence_thread_before = NULL;
792 if (last_sc_fence_local)
793 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
795 /* Iterate over actions in thread, starting from most recent */
796 action_list_t *list = &(*thrd_lists)[i];
797 action_list_t::reverse_iterator rit;
798 for (rit = list->rbegin();rit != list->rend();rit++) {
799 ModelAction *act = *rit;
804 /* Don't want to add reflexive edges on 'rf' */
805 if (act->equals(rf)) {
806 if (act->happens_before(curr))
812 if (act->is_write()) {
813 /* C++, Section 29.3 statement 5 */
814 if (curr->is_seqcst() && last_sc_fence_thread_local &&
815 *act < *last_sc_fence_thread_local) {
816 if (mo_graph->checkReachable(rf, act))
818 priorset->push_back(act);
821 /* C++, Section 29.3 statement 4 */
822 else if (act->is_seqcst() && last_sc_fence_local &&
823 *act < *last_sc_fence_local) {
824 if (mo_graph->checkReachable(rf, act))
826 priorset->push_back(act);
829 /* C++, Section 29.3 statement 6 */
830 else if (last_sc_fence_thread_before &&
831 *act < *last_sc_fence_thread_before) {
832 if (mo_graph->checkReachable(rf, act))
834 priorset->push_back(act);
840 * Include at most one act per-thread that "happens
843 if (act->happens_before(curr)) {
844 if (act->is_write()) {
845 if (mo_graph->checkReachable(rf, act))
847 priorset->push_back(act);
849 const ModelAction *prevrf = act->get_reads_from();
850 if (!prevrf->equals(rf)) {
851 if (mo_graph->checkReachable(rf, prevrf))
853 priorset->push_back(prevrf);
855 if (act->get_tid() == curr->get_tid()) {
856 //Can prune curr from obj list
869 * Updates the mo_graph with the constraints imposed from the current write.
871 * Basic idea is the following: Go through each other thread and find
872 * the lastest action that happened before our write. Two cases:
874 * (1) The action is a write => that write must occur before
877 * (2) The action is a read => the write that that action read from
878 * must occur before the current write.
880 * This method also handles two other issues:
882 * (I) Sequential Consistency: Making sure that if the current write is
883 * seq_cst, that it occurs after the previous seq_cst write.
885 * (II) Sending the write back to non-synchronizing reads.
887 * @param curr The current action. Must be a write.
888 * @param send_fv A vector for stashing reads to which we may pass our future
889 * value. If NULL, then don't record any future values.
890 * @return True if modification order edges were added; false otherwise
892 void ModelExecution::w_modification_order(ModelAction *curr)
894 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
896 ASSERT(curr->is_write());
898 if (curr->is_seqcst()) {
899 /* We have to at least see the last sequentially consistent write,
900 so we are initialized. */
901 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
902 if (last_seq_cst != NULL) {
903 mo_graph->addEdge(last_seq_cst, curr);
907 /* Last SC fence in the current thread */
908 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
910 /* Iterate over all threads */
911 for (i = 0;i < thrd_lists->size();i++) {
912 /* Last SC fence in thread i, before last SC fence in current thread */
913 ModelAction *last_sc_fence_thread_before = NULL;
914 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
915 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
917 /* Iterate over actions in thread, starting from most recent */
918 action_list_t *list = &(*thrd_lists)[i];
919 action_list_t::reverse_iterator rit;
920 bool force_edge = false;
921 for (rit = list->rbegin();rit != list->rend();rit++) {
922 ModelAction *act = *rit;
925 * 1) If RMW and it actually read from something, then we
926 * already have all relevant edges, so just skip to next
929 * 2) If RMW and it didn't read from anything, we should
930 * whatever edge we can get to speed up convergence.
932 * 3) If normal write, we need to look at earlier actions, so
933 * continue processing list.
936 if (curr->is_rmw()) {
937 if (curr->get_reads_from() != NULL)
945 /* C++, Section 29.3 statement 7 */
946 if (last_sc_fence_thread_before && act->is_write() &&
947 *act < *last_sc_fence_thread_before) {
948 mo_graph->addEdge(act, curr, force_edge);
953 * Include at most one act per-thread that "happens
956 if (act->happens_before(curr)) {
958 * Note: if act is RMW, just add edge:
960 * The following edge should be handled elsewhere:
961 * readfrom(act) --mo--> act
964 mo_graph->addEdge(act, curr, force_edge);
965 else if (act->is_read()) {
966 //if previous read accessed a null, just keep going
967 mo_graph->addEdge(act->get_reads_from(), curr, force_edge);
970 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
971 !act->same_thread(curr)) {
972 /* We have an action that:
973 (1) did not happen before us
974 (2) is a read and we are a write
975 (3) cannot synchronize with us
976 (4) is in a different thread
978 that read could potentially read from our write. Note that
979 these checks are overly conservative at this point, we'll
980 do more checks before actually removing the
991 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
992 * some constraints. This method checks one the following constraint (others
993 * require compiler support):
995 * If X --hb-> Y --mo-> Z, then X should not read from Z.
996 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
998 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1000 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1002 /* Iterate over all threads */
1003 for (i = 0;i < thrd_lists->size();i++) {
1004 const ModelAction *write_after_read = NULL;
1006 /* Iterate over actions in thread, starting from most recent */
1007 action_list_t *list = &(*thrd_lists)[i];
1008 action_list_t::reverse_iterator rit;
1009 for (rit = list->rbegin();rit != list->rend();rit++) {
1010 ModelAction *act = *rit;
1012 /* Don't disallow due to act == reader */
1013 if (!reader->happens_before(act) || reader == act)
1015 else if (act->is_write())
1016 write_after_read = act;
1017 else if (act->is_read() && act->get_reads_from() != NULL)
1018 write_after_read = act->get_reads_from();
1021 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1028 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1029 * The ModelAction under consideration is expected to be taking part in
1030 * release/acquire synchronization as an object of the "reads from" relation.
1031 * Note that this can only provide release sequence support for RMW chains
1032 * which do not read from the future, as those actions cannot be traced until
1033 * their "promise" is fulfilled. Similarly, we may not even establish the
1034 * presence of a release sequence with certainty, as some modification order
1035 * constraints may be decided further in the future. Thus, this function
1036 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1037 * and a boolean representing certainty.
1039 * @param rf The action that might be part of a release sequence. Must be a
1041 * @param release_heads A pass-by-reference style return parameter. After
1042 * execution of this function, release_heads will contain the heads of all the
1043 * relevant release sequences, if any exists with certainty
1044 * @return true, if the ModelExecution is certain that release_heads is complete;
1047 bool ModelExecution::release_seq_heads(const ModelAction *rf, rel_heads_list_t *release_heads) const
1050 for ( ;rf != NULL;rf = rf->get_reads_from()) {
1051 ASSERT(rf->is_write());
1053 if (rf->is_release())
1054 release_heads->push_back(rf);
1055 else if (rf->get_last_fence_release())
1056 release_heads->push_back(rf->get_last_fence_release());
1058 break;/* End of RMW chain */
1060 /** @todo Need to be smarter here... In the linux lock
1061 * example, this will run to the beginning of the program for
1063 /** @todo The way to be smarter here is to keep going until 1
1064 * thread has a release preceded by an acquire and you've seen
1067 /* acq_rel RMW is a sufficient stopping condition */
1068 if (rf->is_acquire() && rf->is_release())
1069 return true;/* complete */
1071 ASSERT(rf); // Needs to be real write
1073 if (rf->is_release())
1074 return true;/* complete */
1076 /* else relaxed write
1077 * - check for fence-release in the same thread (29.8, stmt. 3)
1078 * - check modification order for contiguous subsequence
1079 * -> rf must be same thread as release */
1081 const ModelAction *fence_release = rf->get_last_fence_release();
1082 /* Synchronize with a fence-release unconditionally; we don't need to
1083 * find any more "contiguous subsequence..." for it */
1085 release_heads->push_back(fence_release);
1087 return true; /* complete */
1091 * An interface for getting the release sequence head(s) with which a
1092 * given ModelAction must synchronize. This function only returns a non-empty
1093 * result when it can locate a release sequence head with certainty. Otherwise,
1094 * it may mark the internal state of the ModelExecution so that it will handle
1095 * the release sequence at a later time, causing @a acquire to update its
1096 * synchronization at some later point in execution.
1098 * @param acquire The 'acquire' action that may synchronize with a release
1100 * @param read The read action that may read from a release sequence; this may
1101 * be the same as acquire, or else an earlier action in the same thread (i.e.,
1102 * when 'acquire' is a fence-acquire)
1103 * @param release_heads A pass-by-reference return parameter. Will be filled
1104 * with the head(s) of the release sequence(s), if they exists with certainty.
1105 * @see ModelExecution::release_seq_heads
1107 void ModelExecution::get_release_seq_heads(ModelAction *acquire,
1108 ModelAction *read, rel_heads_list_t *release_heads)
1110 const ModelAction *rf = read->get_reads_from();
1112 release_seq_heads(rf, release_heads);
1116 * Performs various bookkeeping operations for the current ModelAction. For
1117 * instance, adds action to the per-object, per-thread action vector and to the
1118 * action trace list of all thread actions.
1120 * @param act is the ModelAction to add.
1122 void ModelExecution::add_action_to_lists(ModelAction *act)
1124 int tid = id_to_int(act->get_tid());
1125 ModelAction *uninit = NULL;
1127 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1128 if (list->empty() && act->is_atomic_var()) {
1129 uninit = get_uninitialized_action(act);
1130 uninit_id = id_to_int(uninit->get_tid());
1131 list->push_front(uninit);
1133 list->push_back(act);
1135 action_trace.push_back(act);
1137 action_trace.push_front(uninit);
1139 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1140 if (tid >= (int)vec->size())
1141 vec->resize(priv->next_thread_id);
1142 (*vec)[tid].push_back(act);
1144 (*vec)[uninit_id].push_front(uninit);
1146 if ((int)thrd_last_action.size() <= tid)
1147 thrd_last_action.resize(get_num_threads());
1148 thrd_last_action[tid] = act;
1150 thrd_last_action[uninit_id] = uninit;
1152 if (act->is_fence() && act->is_release()) {
1153 if ((int)thrd_last_fence_release.size() <= tid)
1154 thrd_last_fence_release.resize(get_num_threads());
1155 thrd_last_fence_release[tid] = act;
1158 if (act->is_wait()) {
1159 void *mutex_loc = (void *) act->get_value();
1160 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
1162 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
1163 if (tid >= (int)vec->size())
1164 vec->resize(priv->next_thread_id);
1165 (*vec)[tid].push_back(act);
1170 * @brief Get the last action performed by a particular Thread
1171 * @param tid The thread ID of the Thread in question
1172 * @return The last action in the thread
1174 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
1176 int threadid = id_to_int(tid);
1177 if (threadid < (int)thrd_last_action.size())
1178 return thrd_last_action[id_to_int(tid)];
1184 * @brief Get the last fence release performed by a particular Thread
1185 * @param tid The thread ID of the Thread in question
1186 * @return The last fence release in the thread, if one exists; NULL otherwise
1188 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
1190 int threadid = id_to_int(tid);
1191 if (threadid < (int)thrd_last_fence_release.size())
1192 return thrd_last_fence_release[id_to_int(tid)];
1198 * Gets the last memory_order_seq_cst write (in the total global sequence)
1199 * performed on a particular object (i.e., memory location), not including the
1201 * @param curr The current ModelAction; also denotes the object location to
1203 * @return The last seq_cst write
1205 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
1207 void *location = curr->get_location();
1208 action_list_t *list = obj_map.get(location);
1209 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1210 action_list_t::reverse_iterator rit;
1211 for (rit = list->rbegin();(*rit) != curr;rit++)
1213 rit++; /* Skip past curr */
1214 for ( ;rit != list->rend();rit++)
1215 if ((*rit)->is_write() && (*rit)->is_seqcst())
1221 * Gets the last memory_order_seq_cst fence (in the total global sequence)
1222 * performed in a particular thread, prior to a particular fence.
1223 * @param tid The ID of the thread to check
1224 * @param before_fence The fence from which to begin the search; if NULL, then
1225 * search for the most recent fence in the thread.
1226 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
1228 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
1230 /* All fences should have location FENCE_LOCATION */
1231 action_list_t *list = obj_map.get(FENCE_LOCATION);
1236 action_list_t::reverse_iterator rit = list->rbegin();
1239 for (;rit != list->rend();rit++)
1240 if (*rit == before_fence)
1243 ASSERT(*rit == before_fence);
1247 for (;rit != list->rend();rit++)
1248 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
1254 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1255 * location). This function identifies the mutex according to the current
1256 * action, which is presumed to perform on the same mutex.
1257 * @param curr The current ModelAction; also denotes the object location to
1259 * @return The last unlock operation
1261 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
1263 void *location = curr->get_location();
1265 action_list_t *list = obj_map.get(location);
1266 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1267 action_list_t::reverse_iterator rit;
1268 for (rit = list->rbegin();rit != list->rend();rit++)
1269 if ((*rit)->is_unlock() || (*rit)->is_wait())
1274 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
1276 ModelAction *parent = get_last_action(tid);
1278 parent = get_thread(tid)->get_creation();
1283 * Returns the clock vector for a given thread.
1284 * @param tid The thread whose clock vector we want
1285 * @return Desired clock vector
1287 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
1289 return get_parent_action(tid)->get_cv();
1292 bool valequals(uint64_t val1, uint64_t val2, int size) {
1295 return ((uint8_t)val1) == ((uint8_t)val2);
1297 return ((uint16_t)val1) == ((uint16_t)val2);
1299 return ((uint32_t)val1) == ((uint32_t)val2);
1309 * Build up an initial set of all past writes that this 'read' action may read
1310 * from, as well as any previously-observed future values that must still be valid.
1312 * @param curr is the current ModelAction that we are exploring; it must be a
1315 SnapVector<const ModelAction *> * ModelExecution::build_may_read_from(ModelAction *curr)
1317 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1319 ASSERT(curr->is_read());
1321 ModelAction *last_sc_write = NULL;
1323 if (curr->is_seqcst())
1324 last_sc_write = get_last_seq_cst_write(curr);
1326 SnapVector<const ModelAction *> * rf_set = new SnapVector<const ModelAction *>();
1328 /* Iterate over all threads */
1329 for (i = 0;i < thrd_lists->size();i++) {
1330 /* Iterate over actions in thread, starting from most recent */
1331 action_list_t *list = &(*thrd_lists)[i];
1332 action_list_t::reverse_iterator rit;
1333 for (rit = list->rbegin();rit != list->rend();rit++) {
1334 const ModelAction *act = *rit;
1336 /* Only consider 'write' actions */
1337 if (!act->is_write()) {
1338 if (act != curr && act->is_read() && act->happens_before(curr)) {
1339 const ModelAction *tmp = act->get_reads_from();
1340 if (((unsigned int) id_to_int(tmp->get_tid()))==i)
1351 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1352 bool allow_read = true;
1354 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
1357 /* Need to check whether we will have two RMW reading from the same value */
1358 if (curr->is_rmwr()) {
1359 /* It is okay if we have a failing CAS */
1360 if (!curr->is_rmwrcas() ||
1361 valequals(curr->get_value(), act->get_value(), curr->getSize())) {
1362 //Need to make sure we aren't the second RMW
1363 CycleNode * node = mo_graph->getNode_noCreate(act);
1364 if (node != NULL && node->getRMW() != NULL) {
1365 //we are the second RMW
1372 /* Only add feasible reads */
1373 rf_set->push_back(act);
1376 /* Include at most one act per-thread that "happens before" curr */
1377 if (act->happens_before(curr))
1382 if (DBG_ENABLED()) {
1383 model_print("Reached read action:\n");
1385 model_print("End printing read_from_past\n");
1391 * @brief Get an action representing an uninitialized atomic
1393 * This function may create a new one or try to retrieve one from the NodeStack
1395 * @param curr The current action, which prompts the creation of an UNINIT action
1396 * @return A pointer to the UNINIT ModelAction
1398 ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
1400 Node *node = curr->get_node();
1401 ModelAction *act = node->get_uninit_action();
1403 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
1404 node->set_uninit_action(act);
1406 act->create_cv(NULL);
1410 static void print_list(const action_list_t *list)
1412 action_list_t::const_iterator it;
1414 model_print("------------------------------------------------------------------------------------\n");
1415 model_print("# t Action type MO Location Value Rf CV\n");
1416 model_print("------------------------------------------------------------------------------------\n");
1418 unsigned int hash = 0;
1420 for (it = list->begin();it != list->end();it++) {
1421 const ModelAction *act = *it;
1422 if (act->get_seq_number() > 0)
1424 hash = hash^(hash<<3)^((*it)->hash());
1426 model_print("HASH %u\n", hash);
1427 model_print("------------------------------------------------------------------------------------\n");
1430 #if SUPPORT_MOD_ORDER_DUMP
1431 void ModelExecution::dumpGraph(char *filename) const
1434 sprintf(buffer, "%s.dot", filename);
1435 FILE *file = fopen(buffer, "w");
1436 fprintf(file, "digraph %s {\n", filename);
1437 mo_graph->dumpNodes(file);
1438 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
1440 for (action_list_t::const_iterator it = action_trace.begin();it != action_trace.end();it++) {
1441 ModelAction *act = *it;
1442 if (act->is_read()) {
1443 mo_graph->dot_print_node(file, act);
1444 mo_graph->dot_print_edge(file,
1445 act->get_reads_from(),
1447 "label=\"rf\", color=red, weight=2");
1449 if (thread_array[act->get_tid()]) {
1450 mo_graph->dot_print_edge(file,
1451 thread_array[id_to_int(act->get_tid())],
1453 "label=\"sb\", color=blue, weight=400");
1456 thread_array[act->get_tid()] = act;
1458 fprintf(file, "}\n");
1459 model_free(thread_array);
1464 /** @brief Prints an execution trace summary. */
1465 void ModelExecution::print_summary() const
1467 #if SUPPORT_MOD_ORDER_DUMP
1468 char buffername[100];
1469 sprintf(buffername, "exec%04u", get_execution_number());
1470 mo_graph->dumpGraphToFile(buffername);
1471 sprintf(buffername, "graph%04u", get_execution_number());
1472 dumpGraph(buffername);
1475 model_print("Execution trace %d:", get_execution_number());
1476 if (isfeasibleprefix()) {
1477 if (scheduler->all_threads_sleeping())
1478 model_print(" SLEEP-SET REDUNDANT");
1479 if (have_bug_reports())
1480 model_print(" DETECTED BUG(S)");
1482 print_infeasibility(" INFEASIBLE");
1485 print_list(&action_trace);
1491 * Add a Thread to the system for the first time. Should only be called once
1493 * @param t The Thread to add
1495 void ModelExecution::add_thread(Thread *t)
1497 unsigned int i = id_to_int(t->get_id());
1498 if (i >= thread_map.size())
1499 thread_map.resize(i + 1);
1501 if (!t->is_model_thread())
1502 scheduler->add_thread(t);
1506 * @brief Get a Thread reference by its ID
1507 * @param tid The Thread's ID
1508 * @return A Thread reference
1510 Thread * ModelExecution::get_thread(thread_id_t tid) const
1512 unsigned int i = id_to_int(tid);
1513 if (i < thread_map.size())
1514 return thread_map[i];
1519 * @brief Get a reference to the Thread in which a ModelAction was executed
1520 * @param act The ModelAction
1521 * @return A Thread reference
1523 Thread * ModelExecution::get_thread(const ModelAction *act) const
1525 return get_thread(act->get_tid());
1529 * @brief Get a Thread reference by its pthread ID
1530 * @param index The pthread's ID
1531 * @return A Thread reference
1533 Thread * ModelExecution::get_pthread(pthread_t pid) {
1539 uint32_t thread_id = x.v;
1540 if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
1545 * @brief Check if a Thread is currently enabled
1546 * @param t The Thread to check
1547 * @return True if the Thread is currently enabled
1549 bool ModelExecution::is_enabled(Thread *t) const
1551 return scheduler->is_enabled(t);
1555 * @brief Check if a Thread is currently enabled
1556 * @param tid The ID of the Thread to check
1557 * @return True if the Thread is currently enabled
1559 bool ModelExecution::is_enabled(thread_id_t tid) const
1561 return scheduler->is_enabled(tid);
1565 * @brief Select the next thread to execute based on the curren action
1567 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
1568 * actions should be followed by the execution of their child thread. In either
1569 * case, the current action should determine the next thread schedule.
1571 * @param curr The current action
1572 * @return The next thread to run, if the current action will determine this
1573 * selection; otherwise NULL
1575 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
1577 /* Do not split atomic RMW */
1578 if (curr->is_rmwr())
1579 return get_thread(curr);
1580 if (curr->is_write()) {
1581 std::memory_order order = curr->get_mo();
1583 case std::memory_order_relaxed:
1584 return get_thread(curr);
1585 case std::memory_order_release:
1586 return get_thread(curr);
1592 /* Follow CREATE with the created thread */
1593 /* which is not needed, because model.cc takes care of this */
1594 if (curr->get_type() == THREAD_CREATE)
1595 return curr->get_thread_operand();
1596 if (curr->get_type() == PTHREAD_CREATE) {
1597 return curr->get_thread_operand();
1603 * Takes the next step in the execution, if possible.
1604 * @param curr The current step to take
1605 * @return Returns the next Thread to run, if any; NULL if this execution
1608 Thread * ModelExecution::take_step(ModelAction *curr)
1610 Thread *curr_thrd = get_thread(curr);
1611 ASSERT(curr_thrd->get_state() == THREAD_READY);
1613 ASSERT(check_action_enabled(curr)); /* May have side effects? */
1614 curr = check_current_action(curr);
1617 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
1618 scheduler->remove_thread(curr_thrd);
1620 return action_select_next_thread(curr);
1623 Fuzzer * ModelExecution::getFuzzer() {