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 int tid = curr->get_tid();
784 ModelAction *prev_same_thread = NULL;
785 /* Iterate over all threads */
786 for (i = 0;i < thrd_lists->size();i++, tid = (((unsigned int)(tid+1)) == thrd_lists->size()) ? 0 : tid + 1) {
787 /* Last SC fence in thread tid */
788 ModelAction *last_sc_fence_thread_local = NULL;
790 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(tid), NULL);
792 /* Last SC fence in thread tid, before last SC fence in current thread */
793 ModelAction *last_sc_fence_thread_before = NULL;
794 if (last_sc_fence_local)
795 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(tid), last_sc_fence_local);
797 //Only need to iterate if either hb has changed for thread in question or SC fence after last operation...
798 if (prev_same_thread != NULL &&
799 (prev_same_thread->get_cv()->getClock(tid) == curr->get_cv()->getClock(tid)) &&
800 (last_sc_fence_thread_local == NULL || *last_sc_fence_thread_local < *prev_same_thread)) {
804 /* Iterate over actions in thread, starting from most recent */
805 action_list_t *list = &(*thrd_lists)[tid];
806 action_list_t::reverse_iterator rit;
807 for (rit = list->rbegin();rit != list->rend();rit++) {
808 ModelAction *act = *rit;
813 /* Don't want to add reflexive edges on 'rf' */
814 if (act->equals(rf)) {
815 if (act->happens_before(curr))
821 if (act->is_write()) {
822 /* C++, Section 29.3 statement 5 */
823 if (curr->is_seqcst() && last_sc_fence_thread_local &&
824 *act < *last_sc_fence_thread_local) {
825 if (mo_graph->checkReachable(rf, act))
827 priorset->push_back(act);
830 /* C++, Section 29.3 statement 4 */
831 else if (act->is_seqcst() && last_sc_fence_local &&
832 *act < *last_sc_fence_local) {
833 if (mo_graph->checkReachable(rf, act))
835 priorset->push_back(act);
838 /* C++, Section 29.3 statement 6 */
839 else if (last_sc_fence_thread_before &&
840 *act < *last_sc_fence_thread_before) {
841 if (mo_graph->checkReachable(rf, act))
843 priorset->push_back(act);
849 * Include at most one act per-thread that "happens
852 if (act->happens_before(curr)) {
854 if (last_sc_fence_local == NULL ||
855 (*last_sc_fence_local < *prev_same_thread)) {
856 prev_same_thread = act;
859 if (act->is_write()) {
860 if (mo_graph->checkReachable(rf, act))
862 priorset->push_back(act);
864 const ModelAction *prevrf = act->get_reads_from();
865 if (!prevrf->equals(rf)) {
866 if (mo_graph->checkReachable(rf, prevrf))
868 priorset->push_back(prevrf);
870 if (act->get_tid() == curr->get_tid()) {
871 //Can prune curr from obj list
884 * Updates the mo_graph with the constraints imposed from the current write.
886 * Basic idea is the following: Go through each other thread and find
887 * the lastest action that happened before our write. Two cases:
889 * (1) The action is a write => that write must occur before
892 * (2) The action is a read => the write that that action read from
893 * must occur before the current write.
895 * This method also handles two other issues:
897 * (I) Sequential Consistency: Making sure that if the current write is
898 * seq_cst, that it occurs after the previous seq_cst write.
900 * (II) Sending the write back to non-synchronizing reads.
902 * @param curr The current action. Must be a write.
903 * @param send_fv A vector for stashing reads to which we may pass our future
904 * value. If NULL, then don't record any future values.
905 * @return True if modification order edges were added; false otherwise
907 void ModelExecution::w_modification_order(ModelAction *curr)
909 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
911 ASSERT(curr->is_write());
913 if (curr->is_seqcst()) {
914 /* We have to at least see the last sequentially consistent write,
915 so we are initialized. */
916 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
917 if (last_seq_cst != NULL) {
918 mo_graph->addEdge(last_seq_cst, curr);
922 /* Last SC fence in the current thread */
923 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
925 /* Iterate over all threads */
926 for (i = 0;i < thrd_lists->size();i++) {
927 /* Last SC fence in thread i, before last SC fence in current thread */
928 ModelAction *last_sc_fence_thread_before = NULL;
929 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
930 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
932 /* Iterate over actions in thread, starting from most recent */
933 action_list_t *list = &(*thrd_lists)[i];
934 action_list_t::reverse_iterator rit;
935 bool force_edge = false;
936 for (rit = list->rbegin();rit != list->rend();rit++) {
937 ModelAction *act = *rit;
940 * 1) If RMW and it actually read from something, then we
941 * already have all relevant edges, so just skip to next
944 * 2) If RMW and it didn't read from anything, we should
945 * whatever edge we can get to speed up convergence.
947 * 3) If normal write, we need to look at earlier actions, so
948 * continue processing list.
951 if (curr->is_rmw()) {
952 if (curr->get_reads_from() != NULL)
960 /* C++, Section 29.3 statement 7 */
961 if (last_sc_fence_thread_before && act->is_write() &&
962 *act < *last_sc_fence_thread_before) {
963 mo_graph->addEdge(act, curr, force_edge);
968 * Include at most one act per-thread that "happens
971 if (act->happens_before(curr)) {
973 * Note: if act is RMW, just add edge:
975 * The following edge should be handled elsewhere:
976 * readfrom(act) --mo--> act
979 mo_graph->addEdge(act, curr, force_edge);
980 else if (act->is_read()) {
981 //if previous read accessed a null, just keep going
982 mo_graph->addEdge(act->get_reads_from(), curr, force_edge);
985 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
986 !act->same_thread(curr)) {
987 /* We have an action that:
988 (1) did not happen before us
989 (2) is a read and we are a write
990 (3) cannot synchronize with us
991 (4) is in a different thread
993 that read could potentially read from our write. Note that
994 these checks are overly conservative at this point, we'll
995 do more checks before actually removing the
1006 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1007 * some constraints. This method checks one the following constraint (others
1008 * require compiler support):
1010 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1011 * If X --hb-> Y, A --rf-> Y, and A --mo-> Z, then X should not read from Z.
1013 bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1015 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
1017 /* Iterate over all threads */
1018 for (i = 0;i < thrd_lists->size();i++) {
1019 const ModelAction *write_after_read = NULL;
1021 /* Iterate over actions in thread, starting from most recent */
1022 action_list_t *list = &(*thrd_lists)[i];
1023 action_list_t::reverse_iterator rit;
1024 for (rit = list->rbegin();rit != list->rend();rit++) {
1025 ModelAction *act = *rit;
1027 /* Don't disallow due to act == reader */
1028 if (!reader->happens_before(act) || reader == act)
1030 else if (act->is_write())
1031 write_after_read = act;
1032 else if (act->is_read() && act->get_reads_from() != NULL)
1033 write_after_read = act->get_reads_from();
1036 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1043 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1044 * The ModelAction under consideration is expected to be taking part in
1045 * release/acquire synchronization as an object of the "reads from" relation.
1046 * Note that this can only provide release sequence support for RMW chains
1047 * which do not read from the future, as those actions cannot be traced until
1048 * their "promise" is fulfilled. Similarly, we may not even establish the
1049 * presence of a release sequence with certainty, as some modification order
1050 * constraints may be decided further in the future. Thus, this function
1051 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1052 * and a boolean representing certainty.
1054 * @param rf The action that might be part of a release sequence. Must be a
1056 * @param release_heads A pass-by-reference style return parameter. After
1057 * execution of this function, release_heads will contain the heads of all the
1058 * relevant release sequences, if any exists with certainty
1059 * @return true, if the ModelExecution is certain that release_heads is complete;
1062 bool ModelExecution::release_seq_heads(const ModelAction *rf, rel_heads_list_t *release_heads) const
1065 for ( ;rf != NULL;rf = rf->get_reads_from()) {
1066 ASSERT(rf->is_write());
1068 if (rf->is_release())
1069 release_heads->push_back(rf);
1070 else if (rf->get_last_fence_release())
1071 release_heads->push_back(rf->get_last_fence_release());
1073 break;/* End of RMW chain */
1075 /** @todo Need to be smarter here... In the linux lock
1076 * example, this will run to the beginning of the program for
1078 /** @todo The way to be smarter here is to keep going until 1
1079 * thread has a release preceded by an acquire and you've seen
1082 /* acq_rel RMW is a sufficient stopping condition */
1083 if (rf->is_acquire() && rf->is_release())
1084 return true;/* complete */
1086 ASSERT(rf); // Needs to be real write
1088 if (rf->is_release())
1089 return true;/* complete */
1091 /* else relaxed write
1092 * - check for fence-release in the same thread (29.8, stmt. 3)
1093 * - check modification order for contiguous subsequence
1094 * -> rf must be same thread as release */
1096 const ModelAction *fence_release = rf->get_last_fence_release();
1097 /* Synchronize with a fence-release unconditionally; we don't need to
1098 * find any more "contiguous subsequence..." for it */
1100 release_heads->push_back(fence_release);
1102 return true; /* complete */
1106 * An interface for getting the release sequence head(s) with which a
1107 * given ModelAction must synchronize. This function only returns a non-empty
1108 * result when it can locate a release sequence head with certainty. Otherwise,
1109 * it may mark the internal state of the ModelExecution so that it will handle
1110 * the release sequence at a later time, causing @a acquire to update its
1111 * synchronization at some later point in execution.
1113 * @param acquire The 'acquire' action that may synchronize with a release
1115 * @param read The read action that may read from a release sequence; this may
1116 * be the same as acquire, or else an earlier action in the same thread (i.e.,
1117 * when 'acquire' is a fence-acquire)
1118 * @param release_heads A pass-by-reference return parameter. Will be filled
1119 * with the head(s) of the release sequence(s), if they exists with certainty.
1120 * @see ModelExecution::release_seq_heads
1122 void ModelExecution::get_release_seq_heads(ModelAction *acquire,
1123 ModelAction *read, rel_heads_list_t *release_heads)
1125 const ModelAction *rf = read->get_reads_from();
1127 release_seq_heads(rf, release_heads);
1131 * Performs various bookkeeping operations for the current ModelAction. For
1132 * instance, adds action to the per-object, per-thread action vector and to the
1133 * action trace list of all thread actions.
1135 * @param act is the ModelAction to add.
1137 void ModelExecution::add_action_to_lists(ModelAction *act)
1139 int tid = id_to_int(act->get_tid());
1140 ModelAction *uninit = NULL;
1142 action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
1143 if (list->empty() && act->is_atomic_var()) {
1144 uninit = get_uninitialized_action(act);
1145 uninit_id = id_to_int(uninit->get_tid());
1146 list->push_front(uninit);
1148 list->push_back(act);
1150 action_trace.push_back(act);
1152 action_trace.push_front(uninit);
1154 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
1155 if (tid >= (int)vec->size())
1156 vec->resize(priv->next_thread_id);
1157 (*vec)[tid].push_back(act);
1159 (*vec)[uninit_id].push_front(uninit);
1161 if ((int)thrd_last_action.size() <= tid)
1162 thrd_last_action.resize(get_num_threads());
1163 thrd_last_action[tid] = act;
1165 thrd_last_action[uninit_id] = uninit;
1167 if (act->is_fence() && act->is_release()) {
1168 if ((int)thrd_last_fence_release.size() <= tid)
1169 thrd_last_fence_release.resize(get_num_threads());
1170 thrd_last_fence_release[tid] = act;
1173 if (act->is_wait()) {
1174 void *mutex_loc = (void *) act->get_value();
1175 get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
1177 SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
1178 if (tid >= (int)vec->size())
1179 vec->resize(priv->next_thread_id);
1180 (*vec)[tid].push_back(act);
1185 * @brief Get the last action performed by a particular Thread
1186 * @param tid The thread ID of the Thread in question
1187 * @return The last action in the thread
1189 ModelAction * ModelExecution::get_last_action(thread_id_t tid) const
1191 int threadid = id_to_int(tid);
1192 if (threadid < (int)thrd_last_action.size())
1193 return thrd_last_action[id_to_int(tid)];
1199 * @brief Get the last fence release performed by a particular Thread
1200 * @param tid The thread ID of the Thread in question
1201 * @return The last fence release in the thread, if one exists; NULL otherwise
1203 ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
1205 int threadid = id_to_int(tid);
1206 if (threadid < (int)thrd_last_fence_release.size())
1207 return thrd_last_fence_release[id_to_int(tid)];
1213 * Gets the last memory_order_seq_cst write (in the total global sequence)
1214 * performed on a particular object (i.e., memory location), not including the
1216 * @param curr The current ModelAction; also denotes the object location to
1218 * @return The last seq_cst write
1220 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
1222 void *location = curr->get_location();
1223 action_list_t *list = obj_map.get(location);
1224 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
1225 action_list_t::reverse_iterator rit;
1226 for (rit = list->rbegin();(*rit) != curr;rit++)
1228 rit++; /* Skip past curr */
1229 for ( ;rit != list->rend();rit++)
1230 if ((*rit)->is_write() && (*rit)->is_seqcst())
1236 * Gets the last memory_order_seq_cst fence (in the total global sequence)
1237 * performed in a particular thread, prior to a particular fence.
1238 * @param tid The ID of the thread to check
1239 * @param before_fence The fence from which to begin the search; if NULL, then
1240 * search for the most recent fence in the thread.
1241 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
1243 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
1245 /* All fences should have location FENCE_LOCATION */
1246 action_list_t *list = obj_map.get(FENCE_LOCATION);
1251 action_list_t::reverse_iterator rit = list->rbegin();
1254 for (;rit != list->rend();rit++)
1255 if (*rit == before_fence)
1258 ASSERT(*rit == before_fence);
1262 for (;rit != list->rend();rit++)
1263 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
1269 * Gets the last unlock operation performed on a particular mutex (i.e., memory
1270 * location). This function identifies the mutex according to the current
1271 * action, which is presumed to perform on the same mutex.
1272 * @param curr The current ModelAction; also denotes the object location to
1274 * @return The last unlock operation
1276 ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
1278 void *location = curr->get_location();
1280 action_list_t *list = obj_map.get(location);
1281 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
1282 action_list_t::reverse_iterator rit;
1283 for (rit = list->rbegin();rit != list->rend();rit++)
1284 if ((*rit)->is_unlock() || (*rit)->is_wait())
1289 ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
1291 ModelAction *parent = get_last_action(tid);
1293 parent = get_thread(tid)->get_creation();
1298 * Returns the clock vector for a given thread.
1299 * @param tid The thread whose clock vector we want
1300 * @return Desired clock vector
1302 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
1304 return get_parent_action(tid)->get_cv();
1307 bool valequals(uint64_t val1, uint64_t val2, int size) {
1310 return ((uint8_t)val1) == ((uint8_t)val2);
1312 return ((uint16_t)val1) == ((uint16_t)val2);
1314 return ((uint32_t)val1) == ((uint32_t)val2);
1324 * Build up an initial set of all past writes that this 'read' action may read
1325 * from, as well as any previously-observed future values that must still be valid.
1327 * @param curr is the current ModelAction that we are exploring; it must be a
1330 SnapVector<const ModelAction *> * ModelExecution::build_may_read_from(ModelAction *curr)
1332 SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
1334 ASSERT(curr->is_read());
1336 ModelAction *last_sc_write = NULL;
1338 if (curr->is_seqcst())
1339 last_sc_write = get_last_seq_cst_write(curr);
1341 SnapVector<const ModelAction *> * rf_set = new SnapVector<const ModelAction *>();
1343 /* Iterate over all threads */
1344 for (i = 0;i < thrd_lists->size();i++) {
1345 /* Iterate over actions in thread, starting from most recent */
1346 action_list_t *list = &(*thrd_lists)[i];
1347 action_list_t::reverse_iterator rit;
1348 for (rit = list->rbegin();rit != list->rend();rit++) {
1349 const ModelAction *act = *rit;
1351 /* Only consider 'write' actions */
1352 if (!act->is_write()) {
1353 if (act != curr && act->is_read() && act->happens_before(curr)) {
1354 const ModelAction *tmp = act->get_reads_from();
1355 if (((unsigned int) id_to_int(tmp->get_tid()))==i)
1366 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
1367 bool allow_read = true;
1369 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
1372 /* Need to check whether we will have two RMW reading from the same value */
1373 if (curr->is_rmwr()) {
1374 /* It is okay if we have a failing CAS */
1375 if (!curr->is_rmwrcas() ||
1376 valequals(curr->get_value(), act->get_value(), curr->getSize())) {
1377 //Need to make sure we aren't the second RMW
1378 CycleNode * node = mo_graph->getNode_noCreate(act);
1379 if (node != NULL && node->getRMW() != NULL) {
1380 //we are the second RMW
1387 /* Only add feasible reads */
1388 rf_set->push_back(act);
1391 /* Include at most one act per-thread that "happens before" curr */
1392 if (act->happens_before(curr))
1397 if (DBG_ENABLED()) {
1398 model_print("Reached read action:\n");
1400 model_print("End printing read_from_past\n");
1406 * @brief Get an action representing an uninitialized atomic
1408 * This function may create a new one or try to retrieve one from the NodeStack
1410 * @param curr The current action, which prompts the creation of an UNINIT action
1411 * @return A pointer to the UNINIT ModelAction
1413 ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
1415 Node *node = curr->get_node();
1416 ModelAction *act = node->get_uninit_action();
1418 act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
1419 node->set_uninit_action(act);
1421 act->create_cv(NULL);
1425 static void print_list(const action_list_t *list)
1427 action_list_t::const_iterator it;
1429 model_print("------------------------------------------------------------------------------------\n");
1430 model_print("# t Action type MO Location Value Rf CV\n");
1431 model_print("------------------------------------------------------------------------------------\n");
1433 unsigned int hash = 0;
1435 for (it = list->begin();it != list->end();it++) {
1436 const ModelAction *act = *it;
1437 if (act->get_seq_number() > 0)
1439 hash = hash^(hash<<3)^((*it)->hash());
1441 model_print("HASH %u\n", hash);
1442 model_print("------------------------------------------------------------------------------------\n");
1445 #if SUPPORT_MOD_ORDER_DUMP
1446 void ModelExecution::dumpGraph(char *filename) const
1449 sprintf(buffer, "%s.dot", filename);
1450 FILE *file = fopen(buffer, "w");
1451 fprintf(file, "digraph %s {\n", filename);
1452 mo_graph->dumpNodes(file);
1453 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
1455 for (action_list_t::const_iterator it = action_trace.begin();it != action_trace.end();it++) {
1456 ModelAction *act = *it;
1457 if (act->is_read()) {
1458 mo_graph->dot_print_node(file, act);
1459 mo_graph->dot_print_edge(file,
1460 act->get_reads_from(),
1462 "label=\"rf\", color=red, weight=2");
1464 if (thread_array[act->get_tid()]) {
1465 mo_graph->dot_print_edge(file,
1466 thread_array[id_to_int(act->get_tid())],
1468 "label=\"sb\", color=blue, weight=400");
1471 thread_array[act->get_tid()] = act;
1473 fprintf(file, "}\n");
1474 model_free(thread_array);
1479 /** @brief Prints an execution trace summary. */
1480 void ModelExecution::print_summary() const
1482 #if SUPPORT_MOD_ORDER_DUMP
1483 char buffername[100];
1484 sprintf(buffername, "exec%04u", get_execution_number());
1485 mo_graph->dumpGraphToFile(buffername);
1486 sprintf(buffername, "graph%04u", get_execution_number());
1487 dumpGraph(buffername);
1490 model_print("Execution trace %d:", get_execution_number());
1491 if (isfeasibleprefix()) {
1492 if (scheduler->all_threads_sleeping())
1493 model_print(" SLEEP-SET REDUNDANT");
1494 if (have_bug_reports())
1495 model_print(" DETECTED BUG(S)");
1497 print_infeasibility(" INFEASIBLE");
1500 print_list(&action_trace);
1506 * Add a Thread to the system for the first time. Should only be called once
1508 * @param t The Thread to add
1510 void ModelExecution::add_thread(Thread *t)
1512 unsigned int i = id_to_int(t->get_id());
1513 if (i >= thread_map.size())
1514 thread_map.resize(i + 1);
1516 if (!t->is_model_thread())
1517 scheduler->add_thread(t);
1521 * @brief Get a Thread reference by its ID
1522 * @param tid The Thread's ID
1523 * @return A Thread reference
1525 Thread * ModelExecution::get_thread(thread_id_t tid) const
1527 unsigned int i = id_to_int(tid);
1528 if (i < thread_map.size())
1529 return thread_map[i];
1534 * @brief Get a reference to the Thread in which a ModelAction was executed
1535 * @param act The ModelAction
1536 * @return A Thread reference
1538 Thread * ModelExecution::get_thread(const ModelAction *act) const
1540 return get_thread(act->get_tid());
1544 * @brief Get a Thread reference by its pthread ID
1545 * @param index The pthread's ID
1546 * @return A Thread reference
1548 Thread * ModelExecution::get_pthread(pthread_t pid) {
1554 uint32_t thread_id = x.v;
1555 if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
1560 * @brief Check if a Thread is currently enabled
1561 * @param t The Thread to check
1562 * @return True if the Thread is currently enabled
1564 bool ModelExecution::is_enabled(Thread *t) const
1566 return scheduler->is_enabled(t);
1570 * @brief Check if a Thread is currently enabled
1571 * @param tid The ID of the Thread to check
1572 * @return True if the Thread is currently enabled
1574 bool ModelExecution::is_enabled(thread_id_t tid) const
1576 return scheduler->is_enabled(tid);
1580 * @brief Select the next thread to execute based on the curren action
1582 * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
1583 * actions should be followed by the execution of their child thread. In either
1584 * case, the current action should determine the next thread schedule.
1586 * @param curr The current action
1587 * @return The next thread to run, if the current action will determine this
1588 * selection; otherwise NULL
1590 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
1592 /* Do not split atomic RMW */
1593 if (curr->is_rmwr())
1594 return get_thread(curr);
1595 if (curr->is_write()) {
1596 std::memory_order order = curr->get_mo();
1598 case std::memory_order_relaxed:
1599 return get_thread(curr);
1600 case std::memory_order_release:
1601 return get_thread(curr);
1607 /* Follow CREATE with the created thread */
1608 /* which is not needed, because model.cc takes care of this */
1609 if (curr->get_type() == THREAD_CREATE)
1610 return curr->get_thread_operand();
1611 if (curr->get_type() == PTHREAD_CREATE) {
1612 return curr->get_thread_operand();
1618 * Takes the next step in the execution, if possible.
1619 * @param curr The current step to take
1620 * @return Returns the next Thread to run, if any; NULL if this execution
1623 Thread * ModelExecution::take_step(ModelAction *curr)
1625 Thread *curr_thrd = get_thread(curr);
1626 ASSERT(curr_thrd->get_state() == THREAD_READY);
1628 ASSERT(check_action_enabled(curr)); /* May have side effects? */
1629 curr = check_current_action(curr);
1632 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
1633 scheduler->remove_thread(curr_thrd);
1635 return action_select_next_thread(curr);
1638 Fuzzer * ModelExecution::getFuzzer() {