10 #include "snapshot-interface.h"
12 #include "clockvector.h"
13 #include "cyclegraph.h"
16 #include "threads-model.h"
19 #define INITIAL_THREAD_ID 0
24 bug_message(const char *str) {
25 const char *fmt = " [BUG] %s\n";
26 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
27 sprintf(msg, fmt, str);
29 ~bug_message() { if (msg) snapshot_free(msg); }
32 void print() { model_print("%s", msg); }
38 * Structure for holding small ModelChecker members that should be snapshotted
40 struct model_snapshot_members {
41 model_snapshot_members() :
43 /* First thread created will have id INITIAL_THREAD_ID */
44 next_thread_id(INITIAL_THREAD_ID),
45 used_sequence_numbers(0),
49 failed_promise(false),
50 too_many_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 ModelAction *current_action;
62 unsigned int next_thread_id;
63 modelclock_t used_sequence_numbers;
64 ModelAction *next_backtrack;
65 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
66 struct execution_stats stats;
69 /** @brief Incorrectly-ordered synchronization was made */
70 bool bad_synchronization;
76 /** @brief Constructor */
77 ModelChecker::ModelChecker(struct model_params params) :
78 /* Initialize default scheduler */
80 scheduler(new Scheduler()),
82 earliest_diverge(NULL),
83 action_trace(new action_list_t()),
84 thread_map(new HashTable<int, Thread *, int>()),
85 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
86 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
89 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
90 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
91 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
92 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
93 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
123 delete thrd_last_fence_release;
130 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
132 action_list_t *tmp = hash->get(ptr);
134 tmp = new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
142 std::vector<action_list_t> *tmp = hash->get(ptr);
144 tmp = new std::vector<action_list_t>();
151 * Restores user program to initial state and resets all model-checker data
154 void ModelChecker::reset_to_initial_state()
156 DEBUG("+++ Resetting to initial state +++\n");
157 node_stack->reset_execution();
159 /* Print all model-checker output before rollback */
162 snapshot_backtrack_before(0);
165 /** @return a thread ID for a new Thread */
166 thread_id_t ModelChecker::get_next_id()
168 return priv->next_thread_id++;
171 /** @return the number of user threads created during this execution */
172 unsigned int ModelChecker::get_num_threads() const
174 return priv->next_thread_id;
178 * Must be called from user-thread context (e.g., through the global
179 * thread_current() interface)
181 * @return The currently executing Thread.
183 Thread * ModelChecker::get_current_thread() const
185 return scheduler->get_current_thread();
188 /** @return a sequence number for a new ModelAction */
189 modelclock_t ModelChecker::get_next_seq_num()
191 return ++priv->used_sequence_numbers;
194 Node * ModelChecker::get_curr_node() const
196 return node_stack->get_head();
200 * @brief Choose the next thread to execute.
202 * This function chooses the next thread that should execute. It can force the
203 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
204 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
205 * The model-checker may have no preference regarding the next thread (i.e.,
206 * when exploring a new execution ordering), in which case this will return
208 * @param curr The current ModelAction. This action might guide the choice of
210 * @return The next thread to run. If the model-checker has no preference, NULL.
212 Thread * ModelChecker::get_next_thread(ModelAction *curr)
217 /* Do not split atomic actions. */
219 return thread_current();
220 else if (curr->get_type() == THREAD_CREATE)
221 return curr->get_thread_operand();
224 /* Have we completed exploring the preselected path? */
228 /* Else, we are trying to replay an execution */
229 ModelAction *next = node_stack->get_next()->get_action();
231 if (next == diverge) {
232 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
233 earliest_diverge = diverge;
235 Node *nextnode = next->get_node();
236 Node *prevnode = nextnode->get_parent();
237 scheduler->update_sleep_set(prevnode);
239 /* Reached divergence point */
240 if (nextnode->increment_misc()) {
241 /* The next node will try to satisfy a different misc_index values. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_promise()) {
245 /* The next node will try to satisfy a different set of promises. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_read_from()) {
249 /* The next node will read from a different value. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_future_value()) {
253 /* The next node will try to read from a different future value. */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
256 } else if (nextnode->increment_relseq_break()) {
257 /* The next node will try to resolve a release sequence differently */
258 tid = next->get_tid();
259 node_stack->pop_restofstack(2);
262 /* Make a different thread execute for next step */
263 scheduler->add_sleep(get_thread(next->get_tid()));
264 tid = prevnode->get_next_backtrack();
265 /* Make sure the backtracked thread isn't sleeping. */
266 node_stack->pop_restofstack(1);
267 if (diverge == earliest_diverge) {
268 earliest_diverge = prevnode->get_action();
271 /* The correct sleep set is in the parent node. */
274 DEBUG("*** Divergence point ***\n");
278 tid = next->get_tid();
280 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
281 ASSERT(tid != THREAD_ID_T_NONE);
282 return thread_map->get(id_to_int(tid));
286 * We need to know what the next actions of all threads in the sleep
287 * set will be. This method computes them and stores the actions at
288 * the corresponding thread object's pending action.
291 void ModelChecker::execute_sleep_set()
293 for (unsigned int i = 0; i < get_num_threads(); i++) {
294 thread_id_t tid = int_to_id(i);
295 Thread *thr = get_thread(tid);
296 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
297 thr->set_state(THREAD_RUNNING);
298 scheduler->next_thread(thr);
299 Thread::swap(&system_context, thr);
300 priv->current_action->set_sleep_flag();
301 thr->set_pending(priv->current_action);
306 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
308 for (unsigned int i = 0; i < get_num_threads(); i++) {
309 Thread *thr = get_thread(int_to_id(i));
310 if (scheduler->is_sleep_set(thr)) {
311 ModelAction *pending_act = thr->get_pending();
312 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
313 //Remove this thread from sleep set
314 scheduler->remove_sleep(thr);
319 /** @brief Alert the model-checker that an incorrectly-ordered
320 * synchronization was made */
321 void ModelChecker::set_bad_synchronization()
323 priv->bad_synchronization = true;
326 bool ModelChecker::has_asserted() const
328 return priv->asserted;
331 void ModelChecker::set_assert()
333 priv->asserted = true;
337 * Check if we are in a deadlock. Should only be called at the end of an
338 * execution, although it should not give false positives in the middle of an
339 * execution (there should be some ENABLED thread).
341 * @return True if program is in a deadlock; false otherwise
343 bool ModelChecker::is_deadlocked() const
345 bool blocking_threads = false;
346 for (unsigned int i = 0; i < get_num_threads(); i++) {
347 thread_id_t tid = int_to_id(i);
350 Thread *t = get_thread(tid);
351 if (!t->is_model_thread() && t->get_pending())
352 blocking_threads = true;
354 return blocking_threads;
358 * Check if this is a complete execution. That is, have all thread completed
359 * execution (rather than exiting because sleep sets have forced a redundant
362 * @return True if the execution is complete.
364 bool ModelChecker::is_complete_execution() const
366 for (unsigned int i = 0; i < get_num_threads(); i++)
367 if (is_enabled(int_to_id(i)))
373 * @brief Assert a bug in the executing program.
375 * Use this function to assert any sort of bug in the user program. If the
376 * current trace is feasible (actually, a prefix of some feasible execution),
377 * then this execution will be aborted, printing the appropriate message. If
378 * the current trace is not yet feasible, the error message will be stashed and
379 * printed if the execution ever becomes feasible.
381 * @param msg Descriptive message for the bug (do not include newline char)
382 * @return True if bug is immediately-feasible
384 bool ModelChecker::assert_bug(const char *msg)
386 priv->bugs.push_back(new bug_message(msg));
388 if (isfeasibleprefix()) {
396 * @brief Assert a bug in the executing program, asserted by a user thread
397 * @see ModelChecker::assert_bug
398 * @param msg Descriptive message for the bug (do not include newline char)
400 void ModelChecker::assert_user_bug(const char *msg)
402 /* If feasible bug, bail out now */
404 switch_to_master(NULL);
407 /** @return True, if any bugs have been reported for this execution */
408 bool ModelChecker::have_bug_reports() const
410 return priv->bugs.size() != 0;
413 /** @brief Print bug report listing for this execution (if any bugs exist) */
414 void ModelChecker::print_bugs() const
416 if (have_bug_reports()) {
417 model_print("Bug report: %zu bug%s detected\n",
419 priv->bugs.size() > 1 ? "s" : "");
420 for (unsigned int i = 0; i < priv->bugs.size(); i++)
421 priv->bugs[i]->print();
426 * @brief Record end-of-execution stats
428 * Must be run when exiting an execution. Records various stats.
429 * @see struct execution_stats
431 void ModelChecker::record_stats()
434 if (!isfeasibleprefix())
435 stats.num_infeasible++;
436 else if (have_bug_reports())
437 stats.num_buggy_executions++;
438 else if (is_complete_execution())
439 stats.num_complete++;
441 stats.num_redundant++;
444 /** @brief Print execution stats */
445 void ModelChecker::print_stats() const
447 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
448 model_print("Number of redundant executions: %d\n", stats.num_redundant);
449 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
450 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
451 model_print("Total executions: %d\n", stats.num_total);
452 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
456 * @brief End-of-exeuction print
457 * @param printbugs Should any existing bugs be printed?
459 void ModelChecker::print_execution(bool printbugs) const
461 print_program_output();
463 if (DBG_ENABLED() || params.verbose) {
464 model_print("Earliest divergence point since last feasible execution:\n");
465 if (earliest_diverge)
466 earliest_diverge->print();
468 model_print("(Not set)\n");
474 /* Don't print invalid bugs */
483 * Queries the model-checker for more executions to explore and, if one
484 * exists, resets the model-checker state to execute a new execution.
486 * @return If there are more executions to explore, return true. Otherwise,
489 bool ModelChecker::next_execution()
492 /* Is this execution a feasible execution that's worth bug-checking? */
493 bool complete = isfeasibleprefix() && (is_complete_execution() ||
496 /* End-of-execution bug checks */
499 assert_bug("Deadlock detected");
507 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
508 print_execution(complete);
510 clear_program_output();
513 earliest_diverge = NULL;
515 if ((diverge = get_next_backtrack()) == NULL)
519 model_print("Next execution will diverge at:\n");
523 reset_to_initial_state();
527 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
529 switch (act->get_type()) {
534 /* Optimization: relaxed operations don't need backtracking */
535 if (act->is_relaxed())
537 /* linear search: from most recent to oldest */
538 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
539 action_list_t::reverse_iterator rit;
540 for (rit = list->rbegin(); rit != list->rend(); rit++) {
541 ModelAction *prev = *rit;
542 if (prev->could_synchronize_with(act))
548 case ATOMIC_TRYLOCK: {
549 /* linear search: from most recent to oldest */
550 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
551 action_list_t::reverse_iterator rit;
552 for (rit = list->rbegin(); rit != list->rend(); rit++) {
553 ModelAction *prev = *rit;
554 if (act->is_conflicting_lock(prev))
559 case ATOMIC_UNLOCK: {
560 /* linear search: from most recent to oldest */
561 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
562 action_list_t::reverse_iterator rit;
563 for (rit = list->rbegin(); rit != list->rend(); rit++) {
564 ModelAction *prev = *rit;
565 if (!act->same_thread(prev) && prev->is_failed_trylock())
571 /* linear search: from most recent to oldest */
572 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
573 action_list_t::reverse_iterator rit;
574 for (rit = list->rbegin(); rit != list->rend(); rit++) {
575 ModelAction *prev = *rit;
576 if (!act->same_thread(prev) && prev->is_failed_trylock())
578 if (!act->same_thread(prev) && prev->is_notify())
584 case ATOMIC_NOTIFY_ALL:
585 case ATOMIC_NOTIFY_ONE: {
586 /* linear search: from most recent to oldest */
587 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
588 action_list_t::reverse_iterator rit;
589 for (rit = list->rbegin(); rit != list->rend(); rit++) {
590 ModelAction *prev = *rit;
591 if (!act->same_thread(prev) && prev->is_wait())
602 /** This method finds backtracking points where we should try to
603 * reorder the parameter ModelAction against.
605 * @param the ModelAction to find backtracking points for.
607 void ModelChecker::set_backtracking(ModelAction *act)
609 Thread *t = get_thread(act);
610 ModelAction *prev = get_last_conflict(act);
614 Node *node = prev->get_node()->get_parent();
616 int low_tid, high_tid;
617 if (node->is_enabled(t)) {
618 low_tid = id_to_int(act->get_tid());
619 high_tid = low_tid + 1;
622 high_tid = get_num_threads();
625 for (int i = low_tid; i < high_tid; i++) {
626 thread_id_t tid = int_to_id(i);
628 /* Make sure this thread can be enabled here. */
629 if (i >= node->get_num_threads())
632 /* Don't backtrack into a point where the thread is disabled or sleeping. */
633 if (node->enabled_status(tid) != THREAD_ENABLED)
636 /* Check if this has been explored already */
637 if (node->has_been_explored(tid))
640 /* See if fairness allows */
641 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
643 for (int t = 0; t < node->get_num_threads(); t++) {
644 thread_id_t tother = int_to_id(t);
645 if (node->is_enabled(tother) && node->has_priority(tother)) {
653 /* Cache the latest backtracking point */
654 set_latest_backtrack(prev);
656 /* If this is a new backtracking point, mark the tree */
657 if (!node->set_backtrack(tid))
659 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
660 id_to_int(prev->get_tid()),
661 id_to_int(t->get_id()));
670 * @brief Cache the a backtracking point as the "most recent", if eligible
672 * Note that this does not prepare the NodeStack for this backtracking
673 * operation, it only caches the action on a per-execution basis
675 * @param act The operation at which we should explore a different next action
676 * (i.e., backtracking point)
677 * @return True, if this action is now the most recent backtracking point;
680 bool ModelChecker::set_latest_backtrack(ModelAction *act)
682 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
683 priv->next_backtrack = act;
690 * Returns last backtracking point. The model checker will explore a different
691 * path for this point in the next execution.
692 * @return The ModelAction at which the next execution should diverge.
694 ModelAction * ModelChecker::get_next_backtrack()
696 ModelAction *next = priv->next_backtrack;
697 priv->next_backtrack = NULL;
702 * Processes a read or rmw model action.
703 * @param curr is the read model action to process.
704 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
705 * @return True if processing this read updates the mo_graph.
707 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
709 uint64_t value = VALUE_NONE;
710 bool updated = false;
712 const ModelAction *reads_from = curr->get_node()->get_read_from();
713 if (reads_from != NULL) {
714 mo_graph->startChanges();
716 value = reads_from->get_value();
717 bool r_status = false;
719 if (!second_part_of_rmw) {
720 check_recency(curr, reads_from);
721 r_status = r_modification_order(curr, reads_from);
725 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
726 mo_graph->rollbackChanges();
727 priv->too_many_reads = false;
731 read_from(curr, reads_from);
732 mo_graph->commitChanges();
733 mo_check_promises(curr->get_tid(), reads_from);
736 } else if (!second_part_of_rmw) {
737 /* Read from future value */
738 value = curr->get_node()->get_future_value();
739 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
740 curr->set_read_from(NULL);
741 Promise *valuepromise = new Promise(curr, value, expiration);
742 promises->push_back(valuepromise);
744 get_thread(curr)->set_return_value(value);
750 * Processes a lock, trylock, or unlock model action. @param curr is
751 * the read model action to process.
753 * The try lock operation checks whether the lock is taken. If not,
754 * it falls to the normal lock operation case. If so, it returns
757 * The lock operation has already been checked that it is enabled, so
758 * it just grabs the lock and synchronizes with the previous unlock.
760 * The unlock operation has to re-enable all of the threads that are
761 * waiting on the lock.
763 * @return True if synchronization was updated; false otherwise
765 bool ModelChecker::process_mutex(ModelAction *curr)
767 std::mutex *mutex = NULL;
768 struct std::mutex_state *state = NULL;
770 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
771 mutex = (std::mutex *)curr->get_location();
772 state = mutex->get_state();
773 } else if (curr->is_wait()) {
774 mutex = (std::mutex *)curr->get_value();
775 state = mutex->get_state();
778 switch (curr->get_type()) {
779 case ATOMIC_TRYLOCK: {
780 bool success = !state->islocked;
781 curr->set_try_lock(success);
783 get_thread(curr)->set_return_value(0);
786 get_thread(curr)->set_return_value(1);
788 //otherwise fall into the lock case
790 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
791 assert_bug("Lock access before initialization");
792 state->islocked = true;
793 ModelAction *unlock = get_last_unlock(curr);
794 //synchronize with the previous unlock statement
795 if (unlock != NULL) {
796 curr->synchronize_with(unlock);
801 case ATOMIC_UNLOCK: {
803 state->islocked = false;
804 //wake up the other threads
805 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
806 //activate all the waiting threads
807 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
808 scheduler->wake(get_thread(*rit));
815 state->islocked = false;
816 //wake up the other threads
817 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
818 //activate all the waiting threads
819 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
820 scheduler->wake(get_thread(*rit));
823 //check whether we should go to sleep or not...simulate spurious failures
824 if (curr->get_node()->get_misc() == 0) {
825 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
827 scheduler->sleep(get_thread(curr));
831 case ATOMIC_NOTIFY_ALL: {
832 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
833 //activate all the waiting threads
834 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
835 scheduler->wake(get_thread(*rit));
840 case ATOMIC_NOTIFY_ONE: {
841 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
842 int wakeupthread = curr->get_node()->get_misc();
843 action_list_t::iterator it = waiters->begin();
844 advance(it, wakeupthread);
845 scheduler->wake(get_thread(*it));
856 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
858 /* Do more ambitious checks now that mo is more complete */
859 if (mo_may_allow(writer, reader) &&
860 reader->get_node()->add_future_value(writer->get_value(),
861 writer->get_seq_number() + params.maxfuturedelay))
862 set_latest_backtrack(reader);
866 * Process a write ModelAction
867 * @param curr The ModelAction to process
868 * @return True if the mo_graph was updated or promises were resolved
870 bool ModelChecker::process_write(ModelAction *curr)
872 bool updated_mod_order = w_modification_order(curr);
873 bool updated_promises = resolve_promises(curr);
875 if (promises->size() == 0) {
876 for (unsigned int i = 0; i < futurevalues->size(); i++) {
877 struct PendingFutureValue pfv = (*futurevalues)[i];
878 add_future_value(pfv.writer, pfv.act);
880 futurevalues->clear();
883 mo_graph->commitChanges();
884 mo_check_promises(curr->get_tid(), curr);
886 get_thread(curr)->set_return_value(VALUE_NONE);
887 return updated_mod_order || updated_promises;
891 * Process a fence ModelAction
892 * @param curr The ModelAction to process
893 * @return True if synchronization was updated
895 bool ModelChecker::process_fence(ModelAction *curr)
898 * fence-relaxed: no-op
899 * fence-release: only log the occurence (not in this function), for
900 * use in later synchronization
901 * fence-acquire (this function): search for hypothetical release
904 bool updated = false;
905 if (curr->is_acquire()) {
906 action_list_t *list = action_trace;
907 action_list_t::reverse_iterator rit;
908 /* Find X : is_read(X) && X --sb-> curr */
909 for (rit = list->rbegin(); rit != list->rend(); rit++) {
910 ModelAction *act = *rit;
913 if (act->get_tid() != curr->get_tid())
915 /* Stop at the beginning of the thread */
916 if (act->is_thread_start())
918 /* Stop once we reach a prior fence-acquire */
919 if (act->is_fence() && act->is_acquire())
923 /* read-acquire will find its own release sequences */
924 if (act->is_acquire())
927 /* Establish hypothetical release sequences */
928 rel_heads_list_t release_heads;
929 get_release_seq_heads(curr, act, &release_heads);
930 for (unsigned int i = 0; i < release_heads.size(); i++)
931 if (!curr->synchronize_with(release_heads[i]))
932 set_bad_synchronization();
933 if (release_heads.size() != 0)
941 * @brief Process the current action for thread-related activity
943 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
944 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
945 * synchronization, etc. This function is a no-op for non-THREAD actions
946 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
948 * @param curr The current action
949 * @return True if synchronization was updated or a thread completed
951 bool ModelChecker::process_thread_action(ModelAction *curr)
953 bool updated = false;
955 switch (curr->get_type()) {
956 case THREAD_CREATE: {
957 Thread *th = curr->get_thread_operand();
958 th->set_creation(curr);
962 Thread *blocking = curr->get_thread_operand();
963 ModelAction *act = get_last_action(blocking->get_id());
964 curr->synchronize_with(act);
965 updated = true; /* trigger rel-seq checks */
968 case THREAD_FINISH: {
969 Thread *th = get_thread(curr);
970 while (!th->wait_list_empty()) {
971 ModelAction *act = th->pop_wait_list();
972 scheduler->wake(get_thread(act));
975 updated = true; /* trigger rel-seq checks */
979 check_promises(curr->get_tid(), NULL, curr->get_cv());
990 * @brief Process the current action for release sequence fixup activity
992 * Performs model-checker release sequence fixups for the current action,
993 * forcing a single pending release sequence to break (with a given, potential
994 * "loose" write) or to complete (i.e., synchronize). If a pending release
995 * sequence forms a complete release sequence, then we must perform the fixup
996 * synchronization, mo_graph additions, etc.
998 * @param curr The current action; must be a release sequence fixup action
999 * @param work_queue The work queue to which to add work items as they are
1002 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1004 const ModelAction *write = curr->get_node()->get_relseq_break();
1005 struct release_seq *sequence = pending_rel_seqs->back();
1006 pending_rel_seqs->pop_back();
1008 ModelAction *acquire = sequence->acquire;
1009 const ModelAction *rf = sequence->rf;
1010 const ModelAction *release = sequence->release;
1014 ASSERT(release->same_thread(rf));
1016 if (write == NULL) {
1018 * @todo Forcing a synchronization requires that we set
1019 * modification order constraints. For instance, we can't allow
1020 * a fixup sequence in which two separate read-acquire
1021 * operations read from the same sequence, where the first one
1022 * synchronizes and the other doesn't. Essentially, we can't
1023 * allow any writes to insert themselves between 'release' and
1027 /* Must synchronize */
1028 if (!acquire->synchronize_with(release)) {
1029 set_bad_synchronization();
1032 /* Re-check all pending release sequences */
1033 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1034 /* Re-check act for mo_graph edges */
1035 work_queue->push_back(MOEdgeWorkEntry(acquire));
1037 /* propagate synchronization to later actions */
1038 action_list_t::reverse_iterator rit = action_trace->rbegin();
1039 for (; (*rit) != acquire; rit++) {
1040 ModelAction *propagate = *rit;
1041 if (acquire->happens_before(propagate)) {
1042 propagate->synchronize_with(acquire);
1043 /* Re-check 'propagate' for mo_graph edges */
1044 work_queue->push_back(MOEdgeWorkEntry(propagate));
1048 /* Break release sequence with new edges:
1049 * release --mo--> write --mo--> rf */
1050 mo_graph->addEdge(release, write);
1051 mo_graph->addEdge(write, rf);
1054 /* See if we have realized a data race */
1059 * Initialize the current action by performing one or more of the following
1060 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1061 * in the NodeStack, manipulating backtracking sets, allocating and
1062 * initializing clock vectors, and computing the promises to fulfill.
1064 * @param curr The current action, as passed from the user context; may be
1065 * freed/invalidated after the execution of this function, with a different
1066 * action "returned" its place (pass-by-reference)
1067 * @return True if curr is a newly-explored action; false otherwise
1069 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1071 ModelAction *newcurr;
1073 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1074 newcurr = process_rmw(*curr);
1077 if (newcurr->is_rmw())
1078 compute_promises(newcurr);
1084 (*curr)->set_seq_number(get_next_seq_num());
1086 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1088 /* First restore type and order in case of RMW operation */
1089 if ((*curr)->is_rmwr())
1090 newcurr->copy_typeandorder(*curr);
1092 ASSERT((*curr)->get_location() == newcurr->get_location());
1093 newcurr->copy_from_new(*curr);
1095 /* Discard duplicate ModelAction; use action from NodeStack */
1098 /* Always compute new clock vector */
1099 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1102 return false; /* Action was explored previously */
1106 /* Always compute new clock vector */
1107 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1109 /* Assign most recent release fence */
1110 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1113 * Perform one-time actions when pushing new ModelAction onto
1116 if (newcurr->is_write())
1117 compute_promises(newcurr);
1118 else if (newcurr->is_relseq_fixup())
1119 compute_relseq_breakwrites(newcurr);
1120 else if (newcurr->is_wait())
1121 newcurr->get_node()->set_misc_max(2);
1122 else if (newcurr->is_notify_one()) {
1123 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1125 return true; /* This was a new ModelAction */
1130 * @brief Establish reads-from relation between two actions
1132 * Perform basic operations involved with establishing a concrete rf relation,
1133 * including setting the ModelAction data and checking for release sequences.
1135 * @param act The action that is reading (must be a read)
1136 * @param rf The action from which we are reading (must be a write)
1138 * @return True if this read established synchronization
1140 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1142 act->set_read_from(rf);
1143 if (rf != NULL && act->is_acquire()) {
1144 rel_heads_list_t release_heads;
1145 get_release_seq_heads(act, act, &release_heads);
1146 int num_heads = release_heads.size();
1147 for (unsigned int i = 0; i < release_heads.size(); i++)
1148 if (!act->synchronize_with(release_heads[i])) {
1149 set_bad_synchronization();
1152 return num_heads > 0;
1158 * @brief Check whether a model action is enabled.
1160 * Checks whether a lock or join operation would be successful (i.e., is the
1161 * lock already locked, or is the joined thread already complete). If not, put
1162 * the action in a waiter list.
1164 * @param curr is the ModelAction to check whether it is enabled.
1165 * @return a bool that indicates whether the action is enabled.
1167 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1168 if (curr->is_lock()) {
1169 std::mutex *lock = (std::mutex *)curr->get_location();
1170 struct std::mutex_state *state = lock->get_state();
1171 if (state->islocked) {
1172 //Stick the action in the appropriate waiting queue
1173 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1176 } else if (curr->get_type() == THREAD_JOIN) {
1177 Thread *blocking = (Thread *)curr->get_location();
1178 if (!blocking->is_complete()) {
1179 blocking->push_wait_list(curr);
1188 * Stores the ModelAction for the current thread action. Call this
1189 * immediately before switching from user- to system-context to pass
1190 * data between them.
1191 * @param act The ModelAction created by the user-thread action
1193 void ModelChecker::set_current_action(ModelAction *act) {
1194 priv->current_action = act;
1198 * This is the heart of the model checker routine. It performs model-checking
1199 * actions corresponding to a given "current action." Among other processes, it
1200 * calculates reads-from relationships, updates synchronization clock vectors,
1201 * forms a memory_order constraints graph, and handles replay/backtrack
1202 * execution when running permutations of previously-observed executions.
1204 * @param curr The current action to process
1205 * @return The ModelAction that is actually executed; may be different than
1206 * curr; may be NULL, if the current action is not enabled to run
1208 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1211 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1213 if (!check_action_enabled(curr)) {
1214 /* Make the execution look like we chose to run this action
1215 * much later, when a lock/join can succeed */
1216 get_thread(curr)->set_pending(curr);
1217 scheduler->sleep(get_thread(curr));
1221 bool newly_explored = initialize_curr_action(&curr);
1227 wake_up_sleeping_actions(curr);
1229 /* Add the action to lists before any other model-checking tasks */
1230 if (!second_part_of_rmw)
1231 add_action_to_lists(curr);
1233 /* Build may_read_from set for newly-created actions */
1234 if (newly_explored && curr->is_read())
1235 build_reads_from_past(curr);
1237 /* Initialize work_queue with the "current action" work */
1238 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1239 while (!work_queue.empty() && !has_asserted()) {
1240 WorkQueueEntry work = work_queue.front();
1241 work_queue.pop_front();
1243 switch (work.type) {
1244 case WORK_CHECK_CURR_ACTION: {
1245 ModelAction *act = work.action;
1246 bool update = false; /* update this location's release seq's */
1247 bool update_all = false; /* update all release seq's */
1249 if (process_thread_action(curr))
1252 if (act->is_read() && process_read(act, second_part_of_rmw))
1255 if (act->is_write() && process_write(act))
1258 if (act->is_fence() && process_fence(act))
1261 if (act->is_mutex_op() && process_mutex(act))
1264 if (act->is_relseq_fixup())
1265 process_relseq_fixup(curr, &work_queue);
1268 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1270 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1273 case WORK_CHECK_RELEASE_SEQ:
1274 resolve_release_sequences(work.location, &work_queue);
1276 case WORK_CHECK_MO_EDGES: {
1277 /** @todo Complete verification of work_queue */
1278 ModelAction *act = work.action;
1279 bool updated = false;
1281 if (act->is_read()) {
1282 const ModelAction *rf = act->get_reads_from();
1283 if (rf != NULL && r_modification_order(act, rf))
1286 if (act->is_write()) {
1287 if (w_modification_order(act))
1290 mo_graph->commitChanges();
1293 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1302 check_curr_backtracking(curr);
1303 set_backtracking(curr);
1307 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1309 Node *currnode = curr->get_node();
1310 Node *parnode = currnode->get_parent();
1312 if ((parnode && !parnode->backtrack_empty()) ||
1313 !currnode->misc_empty() ||
1314 !currnode->read_from_empty() ||
1315 !currnode->future_value_empty() ||
1316 !currnode->promise_empty() ||
1317 !currnode->relseq_break_empty()) {
1318 set_latest_backtrack(curr);
1322 bool ModelChecker::promises_expired() const
1324 for (unsigned int i = 0; i < promises->size(); i++) {
1325 Promise *promise = (*promises)[i];
1326 if (promise->get_expiration() < priv->used_sequence_numbers)
1333 * This is the strongest feasibility check available.
1334 * @return whether the current trace (partial or complete) must be a prefix of
1337 bool ModelChecker::isfeasibleprefix() const
1339 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1343 * Returns whether the current completed trace is feasible, except for pending
1344 * release sequences.
1346 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1348 if (DBG_ENABLED() && promises->size() != 0)
1349 DEBUG("Infeasible: unrevolved promises\n");
1351 return !is_infeasible() && promises->size() == 0;
1355 * Check if the current partial trace is infeasible. Does not check any
1356 * end-of-execution flags, which might rule out the execution. Thus, this is
1357 * useful only for ruling an execution as infeasible.
1358 * @return whether the current partial trace is infeasible.
1360 bool ModelChecker::is_infeasible() const
1362 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1363 DEBUG("Infeasible: RMW violation\n");
1365 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1369 * Check If the current partial trace is infeasible, while ignoring
1370 * infeasibility related to 2 RMW's reading from the same store. It does not
1371 * check end-of-execution feasibility.
1372 * @see ModelChecker::is_infeasible
1373 * @return whether the current partial trace is infeasible, ignoring multiple
1374 * RMWs reading from the same store.
1376 bool ModelChecker::is_infeasible_ignoreRMW() const
1378 if (DBG_ENABLED()) {
1379 if (mo_graph->checkForCycles())
1380 DEBUG("Infeasible: modification order cycles\n");
1381 if (priv->failed_promise)
1382 DEBUG("Infeasible: failed promise\n");
1383 if (priv->too_many_reads)
1384 DEBUG("Infeasible: too many reads\n");
1385 if (priv->bad_synchronization)
1386 DEBUG("Infeasible: bad synchronization ordering\n");
1387 if (promises_expired())
1388 DEBUG("Infeasible: promises expired\n");
1390 return mo_graph->checkForCycles() || priv->failed_promise ||
1391 priv->too_many_reads || priv->bad_synchronization ||
1395 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1396 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1397 ModelAction *lastread = get_last_action(act->get_tid());
1398 lastread->process_rmw(act);
1399 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1400 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1401 mo_graph->commitChanges();
1407 * Checks whether a thread has read from the same write for too many times
1408 * without seeing the effects of a later write.
1411 * 1) there must a different write that we could read from that would satisfy the modification order,
1412 * 2) we must have read from the same value in excess of maxreads times, and
1413 * 3) that other write must have been in the reads_from set for maxreads times.
1415 * If so, we decide that the execution is no longer feasible.
1417 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1419 if (params.maxreads != 0) {
1420 if (curr->get_node()->get_read_from_size() <= 1)
1422 //Must make sure that execution is currently feasible... We could
1423 //accidentally clear by rolling back
1424 if (is_infeasible())
1426 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1427 int tid = id_to_int(curr->get_tid());
1430 if ((int)thrd_lists->size() <= tid)
1432 action_list_t *list = &(*thrd_lists)[tid];
1434 action_list_t::reverse_iterator rit = list->rbegin();
1435 /* Skip past curr */
1436 for (; (*rit) != curr; rit++)
1438 /* go past curr now */
1441 action_list_t::reverse_iterator ritcopy = rit;
1442 //See if we have enough reads from the same value
1444 for (; count < params.maxreads; rit++, count++) {
1445 if (rit == list->rend())
1447 ModelAction *act = *rit;
1448 if (!act->is_read())
1451 if (act->get_reads_from() != rf)
1453 if (act->get_node()->get_read_from_size() <= 1)
1456 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1458 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1460 /* Need a different write */
1464 /* Test to see whether this is a feasible write to read from */
1465 mo_graph->startChanges();
1466 r_modification_order(curr, write);
1467 bool feasiblereadfrom = !is_infeasible();
1468 mo_graph->rollbackChanges();
1470 if (!feasiblereadfrom)
1474 bool feasiblewrite = true;
1475 //new we need to see if this write works for everyone
1477 for (int loop = count; loop > 0; loop--, rit++) {
1478 ModelAction *act = *rit;
1479 bool foundvalue = false;
1480 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1481 if (act->get_node()->get_read_from_at(j) == write) {
1487 feasiblewrite = false;
1491 if (feasiblewrite) {
1492 priv->too_many_reads = true;
1500 * Updates the mo_graph with the constraints imposed from the current
1503 * Basic idea is the following: Go through each other thread and find
1504 * the lastest action that happened before our read. Two cases:
1506 * (1) The action is a write => that write must either occur before
1507 * the write we read from or be the write we read from.
1509 * (2) The action is a read => the write that that action read from
1510 * must occur before the write we read from or be the same write.
1512 * @param curr The current action. Must be a read.
1513 * @param rf The action that curr reads from. Must be a write.
1514 * @return True if modification order edges were added; false otherwise
1516 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1518 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1521 ASSERT(curr->is_read());
1523 /* Last SC fence in the current thread */
1524 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1526 /* Iterate over all threads */
1527 for (i = 0; i < thrd_lists->size(); i++) {
1528 /* Last SC fence in thread i */
1529 ModelAction *last_sc_fence_thread_local = NULL;
1530 if (int_to_id((int)i) != curr->get_tid())
1531 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1533 /* Last SC fence in thread i, before last SC fence in current thread */
1534 ModelAction *last_sc_fence_thread_before = NULL;
1535 if (last_sc_fence_local)
1536 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1538 /* Iterate over actions in thread, starting from most recent */
1539 action_list_t *list = &(*thrd_lists)[i];
1540 action_list_t::reverse_iterator rit;
1541 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1542 ModelAction *act = *rit;
1544 if (act->is_write() && act != rf && act != curr) {
1545 /* C++, Section 29.3 statement 5 */
1546 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1547 *act < *last_sc_fence_thread_local) {
1548 mo_graph->addEdge(act, rf);
1552 /* C++, Section 29.3 statement 4 */
1553 else if (act->is_seqcst() && last_sc_fence_local &&
1554 *act < *last_sc_fence_local) {
1555 mo_graph->addEdge(act, rf);
1559 /* C++, Section 29.3 statement 6 */
1560 else if (last_sc_fence_thread_before &&
1561 *act < *last_sc_fence_thread_before) {
1562 mo_graph->addEdge(act, rf);
1569 * Include at most one act per-thread that "happens
1570 * before" curr. Don't consider reflexively.
1572 if (act->happens_before(curr) && act != curr) {
1573 if (act->is_write()) {
1575 mo_graph->addEdge(act, rf);
1579 const ModelAction *prevreadfrom = act->get_reads_from();
1580 //if the previous read is unresolved, keep going...
1581 if (prevreadfrom == NULL)
1584 if (rf != prevreadfrom) {
1585 mo_graph->addEdge(prevreadfrom, rf);
1597 /** This method fixes up the modification order when we resolve a
1598 * promises. The basic problem is that actions that occur after the
1599 * read curr could not property add items to the modification order
1602 * So for each thread, we find the earliest item that happens after
1603 * the read curr. This is the item we have to fix up with additional
1604 * constraints. If that action is write, we add a MO edge between
1605 * the Action rf and that action. If the action is a read, we add a
1606 * MO edge between the Action rf, and whatever the read accessed.
1608 * @param curr is the read ModelAction that we are fixing up MO edges for.
1609 * @param rf is the write ModelAction that curr reads from.
1612 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1614 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1616 ASSERT(curr->is_read());
1618 /* Iterate over all threads */
1619 for (i = 0; i < thrd_lists->size(); i++) {
1620 /* Iterate over actions in thread, starting from most recent */
1621 action_list_t *list = &(*thrd_lists)[i];
1622 action_list_t::reverse_iterator rit;
1623 ModelAction *lastact = NULL;
1625 /* Find last action that happens after curr that is either not curr or a rmw */
1626 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1627 ModelAction *act = *rit;
1628 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1634 /* Include at most one act per-thread that "happens before" curr */
1635 if (lastact != NULL) {
1636 if (lastact == curr) {
1637 //Case 1: The resolved read is a RMW, and we need to make sure
1638 //that the write portion of the RMW mod order after rf
1640 mo_graph->addEdge(rf, lastact);
1641 } else if (lastact->is_read()) {
1642 //Case 2: The resolved read is a normal read and the next
1643 //operation is a read, and we need to make sure the value read
1644 //is mod ordered after rf
1646 const ModelAction *postreadfrom = lastact->get_reads_from();
1647 if (postreadfrom != NULL && rf != postreadfrom)
1648 mo_graph->addEdge(rf, postreadfrom);
1650 //Case 3: The resolved read is a normal read and the next
1651 //operation is a write, and we need to make sure that the
1652 //write is mod ordered after rf
1654 mo_graph->addEdge(rf, lastact);
1662 * Updates the mo_graph with the constraints imposed from the current write.
1664 * Basic idea is the following: Go through each other thread and find
1665 * the lastest action that happened before our write. Two cases:
1667 * (1) The action is a write => that write must occur before
1670 * (2) The action is a read => the write that that action read from
1671 * must occur before the current write.
1673 * This method also handles two other issues:
1675 * (I) Sequential Consistency: Making sure that if the current write is
1676 * seq_cst, that it occurs after the previous seq_cst write.
1678 * (II) Sending the write back to non-synchronizing reads.
1680 * @param curr The current action. Must be a write.
1681 * @return True if modification order edges were added; false otherwise
1683 bool ModelChecker::w_modification_order(ModelAction *curr)
1685 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1688 ASSERT(curr->is_write());
1690 if (curr->is_seqcst()) {
1691 /* We have to at least see the last sequentially consistent write,
1692 so we are initialized. */
1693 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1694 if (last_seq_cst != NULL) {
1695 mo_graph->addEdge(last_seq_cst, curr);
1700 /* Last SC fence in the current thread */
1701 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1703 /* Iterate over all threads */
1704 for (i = 0; i < thrd_lists->size(); i++) {
1705 /* Last SC fence in thread i, before last SC fence in current thread */
1706 ModelAction *last_sc_fence_thread_before = NULL;
1707 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1708 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1710 /* Iterate over actions in thread, starting from most recent */
1711 action_list_t *list = &(*thrd_lists)[i];
1712 action_list_t::reverse_iterator rit;
1713 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1714 ModelAction *act = *rit;
1717 * 1) If RMW and it actually read from something, then we
1718 * already have all relevant edges, so just skip to next
1721 * 2) If RMW and it didn't read from anything, we should
1722 * whatever edge we can get to speed up convergence.
1724 * 3) If normal write, we need to look at earlier actions, so
1725 * continue processing list.
1727 if (curr->is_rmw()) {
1728 if (curr->get_reads_from() != NULL)
1736 /* C++, Section 29.3 statement 7 */
1737 if (last_sc_fence_thread_before && act->is_write() &&
1738 *act < *last_sc_fence_thread_before) {
1739 mo_graph->addEdge(act, curr);
1745 * Include at most one act per-thread that "happens
1748 if (act->happens_before(curr)) {
1750 * Note: if act is RMW, just add edge:
1752 * The following edge should be handled elsewhere:
1753 * readfrom(act) --mo--> act
1755 if (act->is_write())
1756 mo_graph->addEdge(act, curr);
1757 else if (act->is_read()) {
1758 //if previous read accessed a null, just keep going
1759 if (act->get_reads_from() == NULL)
1761 mo_graph->addEdge(act->get_reads_from(), curr);
1765 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1766 !act->same_thread(curr)) {
1767 /* We have an action that:
1768 (1) did not happen before us
1769 (2) is a read and we are a write
1770 (3) cannot synchronize with us
1771 (4) is in a different thread
1773 that read could potentially read from our write. Note that
1774 these checks are overly conservative at this point, we'll
1775 do more checks before actually removing the
1779 if (thin_air_constraint_may_allow(curr, act)) {
1780 if (!is_infeasible() ||
1781 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1782 futurevalues->push_back(PendingFutureValue(curr, act));
1792 /** Arbitrary reads from the future are not allowed. Section 29.3
1793 * part 9 places some constraints. This method checks one result of constraint
1794 * constraint. Others require compiler support. */
1795 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1797 if (!writer->is_rmw())
1800 if (!reader->is_rmw())
1803 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1804 if (search == reader)
1806 if (search->get_tid() == reader->get_tid() &&
1807 search->happens_before(reader))
1815 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1816 * some constraints. This method checks one the following constraint (others
1817 * require compiler support):
1819 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1821 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1823 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1825 /* Iterate over all threads */
1826 for (i = 0; i < thrd_lists->size(); i++) {
1827 const ModelAction *write_after_read = NULL;
1829 /* Iterate over actions in thread, starting from most recent */
1830 action_list_t *list = &(*thrd_lists)[i];
1831 action_list_t::reverse_iterator rit;
1832 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1833 ModelAction *act = *rit;
1835 /* Don't disallow due to act == reader */
1836 if (!reader->happens_before(act) || reader == act)
1838 else if (act->is_write())
1839 write_after_read = act;
1840 else if (act->is_read() && act->get_reads_from() != NULL)
1841 write_after_read = act->get_reads_from();
1844 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1851 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1852 * The ModelAction under consideration is expected to be taking part in
1853 * release/acquire synchronization as an object of the "reads from" relation.
1854 * Note that this can only provide release sequence support for RMW chains
1855 * which do not read from the future, as those actions cannot be traced until
1856 * their "promise" is fulfilled. Similarly, we may not even establish the
1857 * presence of a release sequence with certainty, as some modification order
1858 * constraints may be decided further in the future. Thus, this function
1859 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1860 * and a boolean representing certainty.
1862 * @param rf The action that might be part of a release sequence. Must be a
1864 * @param release_heads A pass-by-reference style return parameter. After
1865 * execution of this function, release_heads will contain the heads of all the
1866 * relevant release sequences, if any exists with certainty
1867 * @param pending A pass-by-reference style return parameter which is only used
1868 * when returning false (i.e., uncertain). Returns most information regarding
1869 * an uncertain release sequence, including any write operations that might
1870 * break the sequence.
1871 * @return true, if the ModelChecker is certain that release_heads is complete;
1874 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1875 rel_heads_list_t *release_heads,
1876 struct release_seq *pending) const
1878 /* Only check for release sequences if there are no cycles */
1879 if (mo_graph->checkForCycles())
1883 ASSERT(rf->is_write());
1885 if (rf->is_release())
1886 release_heads->push_back(rf);
1887 else if (rf->get_last_fence_release())
1888 release_heads->push_back(rf->get_last_fence_release());
1890 break; /* End of RMW chain */
1892 /** @todo Need to be smarter here... In the linux lock
1893 * example, this will run to the beginning of the program for
1895 /** @todo The way to be smarter here is to keep going until 1
1896 * thread has a release preceded by an acquire and you've seen
1899 /* acq_rel RMW is a sufficient stopping condition */
1900 if (rf->is_acquire() && rf->is_release())
1901 return true; /* complete */
1903 rf = rf->get_reads_from();
1906 /* read from future: need to settle this later */
1908 return false; /* incomplete */
1911 if (rf->is_release())
1912 return true; /* complete */
1914 /* else relaxed write
1915 * - check for fence-release in the same thread (29.8, stmt. 3)
1916 * - check modification order for contiguous subsequence
1917 * -> rf must be same thread as release */
1919 const ModelAction *fence_release = rf->get_last_fence_release();
1920 /* Synchronize with a fence-release unconditionally; we don't need to
1921 * find any more "contiguous subsequence..." for it */
1923 release_heads->push_back(fence_release);
1925 int tid = id_to_int(rf->get_tid());
1926 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1927 action_list_t *list = &(*thrd_lists)[tid];
1928 action_list_t::const_reverse_iterator rit;
1930 /* Find rf in the thread list */
1931 rit = std::find(list->rbegin(), list->rend(), rf);
1932 ASSERT(rit != list->rend());
1934 /* Find the last {write,fence}-release */
1935 for (; rit != list->rend(); rit++) {
1936 if (fence_release && *(*rit) < *fence_release)
1938 if ((*rit)->is_release())
1941 if (rit == list->rend()) {
1942 /* No write-release in this thread */
1943 return true; /* complete */
1944 } else if (fence_release && *(*rit) < *fence_release) {
1945 /* The fence-release is more recent (and so, "stronger") than
1946 * the most recent write-release */
1947 return true; /* complete */
1948 } /* else, need to establish contiguous release sequence */
1949 ModelAction *release = *rit;
1951 ASSERT(rf->same_thread(release));
1953 pending->writes.clear();
1955 bool certain = true;
1956 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1957 if (id_to_int(rf->get_tid()) == (int)i)
1959 list = &(*thrd_lists)[i];
1961 /* Can we ensure no future writes from this thread may break
1962 * the release seq? */
1963 bool future_ordered = false;
1965 ModelAction *last = get_last_action(int_to_id(i));
1966 Thread *th = get_thread(int_to_id(i));
1967 if ((last && rf->happens_before(last)) ||
1970 future_ordered = true;
1972 ASSERT(!th->is_model_thread() || future_ordered);
1974 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1975 const ModelAction *act = *rit;
1976 /* Reach synchronization -> this thread is complete */
1977 if (act->happens_before(release))
1979 if (rf->happens_before(act)) {
1980 future_ordered = true;
1984 /* Only non-RMW writes can break release sequences */
1985 if (!act->is_write() || act->is_rmw())
1988 /* Check modification order */
1989 if (mo_graph->checkReachable(rf, act)) {
1990 /* rf --mo--> act */
1991 future_ordered = true;
1994 if (mo_graph->checkReachable(act, release))
1995 /* act --mo--> release */
1997 if (mo_graph->checkReachable(release, act) &&
1998 mo_graph->checkReachable(act, rf)) {
1999 /* release --mo-> act --mo--> rf */
2000 return true; /* complete */
2002 /* act may break release sequence */
2003 pending->writes.push_back(act);
2006 if (!future_ordered)
2007 certain = false; /* This thread is uncertain */
2011 release_heads->push_back(release);
2012 pending->writes.clear();
2014 pending->release = release;
2021 * An interface for getting the release sequence head(s) with which a
2022 * given ModelAction must synchronize. This function only returns a non-empty
2023 * result when it can locate a release sequence head with certainty. Otherwise,
2024 * it may mark the internal state of the ModelChecker so that it will handle
2025 * the release sequence at a later time, causing @a acquire to update its
2026 * synchronization at some later point in execution.
2028 * @param acquire The 'acquire' action that may synchronize with a release
2030 * @param read The read action that may read from a release sequence; this may
2031 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2032 * when 'acquire' is a fence-acquire)
2033 * @param release_heads A pass-by-reference return parameter. Will be filled
2034 * with the head(s) of the release sequence(s), if they exists with certainty.
2035 * @see ModelChecker::release_seq_heads
2037 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2038 ModelAction *read, rel_heads_list_t *release_heads)
2040 const ModelAction *rf = read->get_reads_from();
2041 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2042 sequence->acquire = acquire;
2043 sequence->read = read;
2045 if (!release_seq_heads(rf, release_heads, sequence)) {
2046 /* add act to 'lazy checking' list */
2047 pending_rel_seqs->push_back(sequence);
2049 snapshot_free(sequence);
2054 * Attempt to resolve all stashed operations that might synchronize with a
2055 * release sequence for a given location. This implements the "lazy" portion of
2056 * determining whether or not a release sequence was contiguous, since not all
2057 * modification order information is present at the time an action occurs.
2059 * @param location The location/object that should be checked for release
2060 * sequence resolutions. A NULL value means to check all locations.
2061 * @param work_queue The work queue to which to add work items as they are
2063 * @return True if any updates occurred (new synchronization, new mo_graph
2066 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2068 bool updated = false;
2069 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2070 while (it != pending_rel_seqs->end()) {
2071 struct release_seq *pending = *it;
2072 ModelAction *acquire = pending->acquire;
2073 const ModelAction *read = pending->read;
2075 /* Only resolve sequences on the given location, if provided */
2076 if (location && read->get_location() != location) {
2081 const ModelAction *rf = read->get_reads_from();
2082 rel_heads_list_t release_heads;
2084 complete = release_seq_heads(rf, &release_heads, pending);
2085 for (unsigned int i = 0; i < release_heads.size(); i++) {
2086 if (!acquire->has_synchronized_with(release_heads[i])) {
2087 if (acquire->synchronize_with(release_heads[i]))
2090 set_bad_synchronization();
2095 /* Re-check all pending release sequences */
2096 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2097 /* Re-check read-acquire for mo_graph edges */
2098 if (acquire->is_read())
2099 work_queue->push_back(MOEdgeWorkEntry(acquire));
2101 /* propagate synchronization to later actions */
2102 action_list_t::reverse_iterator rit = action_trace->rbegin();
2103 for (; (*rit) != acquire; rit++) {
2104 ModelAction *propagate = *rit;
2105 if (acquire->happens_before(propagate)) {
2106 propagate->synchronize_with(acquire);
2107 /* Re-check 'propagate' for mo_graph edges */
2108 work_queue->push_back(MOEdgeWorkEntry(propagate));
2113 it = pending_rel_seqs->erase(it);
2114 snapshot_free(pending);
2120 // If we resolved promises or data races, see if we have realized a data race.
2127 * Performs various bookkeeping operations for the current ModelAction. For
2128 * instance, adds action to the per-object, per-thread action vector and to the
2129 * action trace list of all thread actions.
2131 * @param act is the ModelAction to add.
2133 void ModelChecker::add_action_to_lists(ModelAction *act)
2135 int tid = id_to_int(act->get_tid());
2136 ModelAction *uninit = NULL;
2138 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2139 if (list->empty() && act->is_atomic_var()) {
2140 uninit = new_uninitialized_action(act->get_location());
2141 uninit_id = id_to_int(uninit->get_tid());
2142 list->push_back(uninit);
2144 list->push_back(act);
2146 action_trace->push_back(act);
2148 action_trace->push_front(uninit);
2150 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2151 if (tid >= (int)vec->size())
2152 vec->resize(priv->next_thread_id);
2153 (*vec)[tid].push_back(act);
2155 (*vec)[uninit_id].push_front(uninit);
2157 if ((int)thrd_last_action->size() <= tid)
2158 thrd_last_action->resize(get_num_threads());
2159 (*thrd_last_action)[tid] = act;
2161 (*thrd_last_action)[uninit_id] = uninit;
2163 if (act->is_fence() && act->is_release()) {
2164 if ((int)thrd_last_fence_release->size() <= tid)
2165 thrd_last_fence_release->resize(get_num_threads());
2166 (*thrd_last_fence_release)[tid] = act;
2169 if (act->is_wait()) {
2170 void *mutex_loc = (void *) act->get_value();
2171 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2173 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2174 if (tid >= (int)vec->size())
2175 vec->resize(priv->next_thread_id);
2176 (*vec)[tid].push_back(act);
2181 * @brief Get the last action performed by a particular Thread
2182 * @param tid The thread ID of the Thread in question
2183 * @return The last action in the thread
2185 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2187 int threadid = id_to_int(tid);
2188 if (threadid < (int)thrd_last_action->size())
2189 return (*thrd_last_action)[id_to_int(tid)];
2195 * @brief Get the last fence release performed by a particular Thread
2196 * @param tid The thread ID of the Thread in question
2197 * @return The last fence release in the thread, if one exists; NULL otherwise
2199 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2201 int threadid = id_to_int(tid);
2202 if (threadid < (int)thrd_last_fence_release->size())
2203 return (*thrd_last_fence_release)[id_to_int(tid)];
2209 * Gets the last memory_order_seq_cst write (in the total global sequence)
2210 * performed on a particular object (i.e., memory location), not including the
2212 * @param curr The current ModelAction; also denotes the object location to
2214 * @return The last seq_cst write
2216 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2218 void *location = curr->get_location();
2219 action_list_t *list = get_safe_ptr_action(obj_map, location);
2220 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2221 action_list_t::reverse_iterator rit;
2222 for (rit = list->rbegin(); rit != list->rend(); rit++)
2223 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2229 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2230 * performed in a particular thread, prior to a particular fence.
2231 * @param tid The ID of the thread to check
2232 * @param before_fence The fence from which to begin the search; if NULL, then
2233 * search for the most recent fence in the thread.
2234 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2236 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2238 /* All fences should have NULL location */
2239 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2240 action_list_t::reverse_iterator rit = list->rbegin();
2243 for (; rit != list->rend(); rit++)
2244 if (*rit == before_fence)
2247 ASSERT(*rit == before_fence);
2251 for (; rit != list->rend(); rit++)
2252 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2258 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2259 * location). This function identifies the mutex according to the current
2260 * action, which is presumed to perform on the same mutex.
2261 * @param curr The current ModelAction; also denotes the object location to
2263 * @return The last unlock operation
2265 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2267 void *location = curr->get_location();
2268 action_list_t *list = get_safe_ptr_action(obj_map, location);
2269 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2270 action_list_t::reverse_iterator rit;
2271 for (rit = list->rbegin(); rit != list->rend(); rit++)
2272 if ((*rit)->is_unlock() || (*rit)->is_wait())
2277 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2279 ModelAction *parent = get_last_action(tid);
2281 parent = get_thread(tid)->get_creation();
2286 * Returns the clock vector for a given thread.
2287 * @param tid The thread whose clock vector we want
2288 * @return Desired clock vector
2290 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2292 return get_parent_action(tid)->get_cv();
2296 * Resolve a set of Promises with a current write. The set is provided in the
2297 * Node corresponding to @a write.
2298 * @param write The ModelAction that is fulfilling Promises
2299 * @return True if promises were resolved; false otherwise
2301 bool ModelChecker::resolve_promises(ModelAction *write)
2303 bool resolved = false;
2304 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2306 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2307 Promise *promise = (*promises)[promise_index];
2308 if (write->get_node()->get_promise(i)) {
2309 ModelAction *read = promise->get_action();
2310 if (read->is_rmw()) {
2311 mo_graph->addRMWEdge(write, read);
2313 read_from(read, write);
2314 //First fix up the modification order for actions that happened
2316 r_modification_order(read, write);
2317 //Next fix up the modification order for actions that happened
2319 post_r_modification_order(read, write);
2320 //Make sure the promise's value matches the write's value
2321 ASSERT(promise->get_value() == write->get_value());
2324 promises->erase(promises->begin() + promise_index);
2325 threads_to_check.push_back(read->get_tid());
2332 //Check whether reading these writes has made threads unable to
2335 for (unsigned int i = 0; i < threads_to_check.size(); i++)
2336 mo_check_promises(threads_to_check[i], write);
2342 * Compute the set of promises that could potentially be satisfied by this
2343 * action. Note that the set computation actually appears in the Node, not in
2345 * @param curr The ModelAction that may satisfy promises
2347 void ModelChecker::compute_promises(ModelAction *curr)
2349 for (unsigned int i = 0; i < promises->size(); i++) {
2350 Promise *promise = (*promises)[i];
2351 const ModelAction *act = promise->get_action();
2352 if (!act->happens_before(curr) &&
2354 !act->could_synchronize_with(curr) &&
2355 !act->same_thread(curr) &&
2356 act->get_location() == curr->get_location() &&
2357 promise->get_value() == curr->get_value()) {
2358 curr->get_node()->set_promise(i, act->is_rmw());
2363 /** Checks promises in response to change in ClockVector Threads. */
2364 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2366 for (unsigned int i = 0; i < promises->size(); i++) {
2367 Promise *promise = (*promises)[i];
2368 const ModelAction *act = promise->get_action();
2369 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2370 merge_cv->synchronized_since(act)) {
2371 if (promise->increment_threads(tid)) {
2372 //Promise has failed
2373 priv->failed_promise = true;
2380 void ModelChecker::check_promises_thread_disabled() {
2381 for (unsigned int i = 0; i < promises->size(); i++) {
2382 Promise *promise = (*promises)[i];
2383 if (promise->check_promise()) {
2384 priv->failed_promise = true;
2390 /** Checks promises in response to addition to modification order for threads.
2392 * pthread is the thread that performed the read that created the promise
2394 * pread is the read that created the promise
2396 * pwrite is either the first write to same location as pread by
2397 * pthread that is sequenced after pread or the value read by the
2398 * first read to the same lcoation as pread by pthread that is
2399 * sequenced after pread..
2401 * 1. If tid=pthread, then we check what other threads are reachable
2402 * through the mode order starting with pwrite. Those threads cannot
2403 * perform a write that will resolve the promise due to modification
2404 * order constraints.
2406 * 2. If the tid is not pthread, we check whether pwrite can reach the
2407 * action write through the modification order. If so, that thread
2408 * cannot perform a future write that will resolve the promise due to
2409 * modificatin order constraints.
2411 * @param tid The thread that either read from the model action
2412 * write, or actually did the model action write.
2414 * @param write The ModelAction representing the relevant write.
2416 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write)
2418 void *location = write->get_location();
2419 for (unsigned int i = 0; i < promises->size(); i++) {
2420 Promise *promise = (*promises)[i];
2421 const ModelAction *act = promise->get_action();
2423 //Is this promise on the same location?
2424 if (act->get_location() != location)
2427 //same thread as the promise
2428 if (act->get_tid() == tid) {
2430 //do we have a pwrite for the promise, if not, set it
2431 if (promise->get_write() == NULL) {
2432 promise->set_write(write);
2433 //The pwrite cannot happen before the promise
2434 if (write->happens_before(act) && (write != act)) {
2435 priv->failed_promise = true;
2439 if (mo_graph->checkPromise(write, promise)) {
2440 priv->failed_promise = true;
2445 //Don't do any lookups twice for the same thread
2446 if (promise->has_sync_thread(tid))
2449 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2450 if (promise->increment_threads(tid)) {
2451 priv->failed_promise = true;
2459 * Compute the set of writes that may break the current pending release
2460 * sequence. This information is extracted from previou release sequence
2463 * @param curr The current ModelAction. Must be a release sequence fixup
2466 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2468 if (pending_rel_seqs->empty())
2471 struct release_seq *pending = pending_rel_seqs->back();
2472 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2473 const ModelAction *write = pending->writes[i];
2474 curr->get_node()->add_relseq_break(write);
2477 /* NULL means don't break the sequence; just synchronize */
2478 curr->get_node()->add_relseq_break(NULL);
2482 * Build up an initial set of all past writes that this 'read' action may read
2483 * from. This set is determined by the clock vector's "happens before"
2485 * @param curr is the current ModelAction that we are exploring; it must be a
2488 void ModelChecker::build_reads_from_past(ModelAction *curr)
2490 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2492 ASSERT(curr->is_read());
2494 ModelAction *last_sc_write = NULL;
2496 if (curr->is_seqcst())
2497 last_sc_write = get_last_seq_cst_write(curr);
2499 /* Iterate over all threads */
2500 for (i = 0; i < thrd_lists->size(); i++) {
2501 /* Iterate over actions in thread, starting from most recent */
2502 action_list_t *list = &(*thrd_lists)[i];
2503 action_list_t::reverse_iterator rit;
2504 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2505 ModelAction *act = *rit;
2507 /* Only consider 'write' actions */
2508 if (!act->is_write() || act == curr)
2511 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2512 bool allow_read = true;
2514 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2516 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2520 curr->get_node()->add_read_from(act);
2522 /* Include at most one act per-thread that "happens before" curr */
2523 if (act->happens_before(curr))
2528 if (DBG_ENABLED()) {
2529 model_print("Reached read action:\n");
2531 model_print("Printing may_read_from\n");
2532 curr->get_node()->print_may_read_from();
2533 model_print("End printing may_read_from\n");
2537 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2540 /* UNINIT actions don't have a Node, and they never sleep */
2541 if (write->is_uninitialized())
2543 Node *prevnode = write->get_node()->get_parent();
2545 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2546 if (write->is_release() && thread_sleep)
2548 if (!write->is_rmw()) {
2551 if (write->get_reads_from() == NULL)
2553 write = write->get_reads_from();
2558 * @brief Create a new action representing an uninitialized atomic
2559 * @param location The memory location of the atomic object
2560 * @return A pointer to a new ModelAction
2562 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2564 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2565 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2566 act->create_cv(NULL);
2570 static void print_list(action_list_t *list, int exec_num = -1)
2572 action_list_t::iterator it;
2574 model_print("---------------------------------------------------------------------\n");
2576 model_print("Execution %d:\n", exec_num);
2578 unsigned int hash = 0;
2580 for (it = list->begin(); it != list->end(); it++) {
2582 hash = hash^(hash<<3)^((*it)->hash());
2584 model_print("HASH %u\n", hash);
2585 model_print("---------------------------------------------------------------------\n");
2588 #if SUPPORT_MOD_ORDER_DUMP
2589 void ModelChecker::dumpGraph(char *filename) const
2592 sprintf(buffer, "%s.dot", filename);
2593 FILE *file = fopen(buffer, "w");
2594 fprintf(file, "digraph %s {\n", filename);
2595 mo_graph->dumpNodes(file);
2596 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2598 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2599 ModelAction *action = *it;
2600 if (action->is_read()) {
2601 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2602 if (action->get_reads_from() != NULL)
2603 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2605 if (thread_array[action->get_tid()] != NULL) {
2606 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2609 thread_array[action->get_tid()] = action;
2611 fprintf(file, "}\n");
2612 model_free(thread_array);
2617 /** @brief Prints an execution trace summary. */
2618 void ModelChecker::print_summary() const
2620 #if SUPPORT_MOD_ORDER_DUMP
2622 char buffername[100];
2623 sprintf(buffername, "exec%04u", stats.num_total);
2624 mo_graph->dumpGraphToFile(buffername);
2625 sprintf(buffername, "graph%04u", stats.num_total);
2626 dumpGraph(buffername);
2629 if (!isfeasibleprefix())
2630 model_print("INFEASIBLE EXECUTION!\n");
2631 print_list(action_trace, stats.num_total);
2636 * Add a Thread to the system for the first time. Should only be called once
2638 * @param t The Thread to add
2640 void ModelChecker::add_thread(Thread *t)
2642 thread_map->put(id_to_int(t->get_id()), t);
2643 scheduler->add_thread(t);
2647 * Removes a thread from the scheduler.
2648 * @param the thread to remove.
2650 void ModelChecker::remove_thread(Thread *t)
2652 scheduler->remove_thread(t);
2656 * @brief Get a Thread reference by its ID
2657 * @param tid The Thread's ID
2658 * @return A Thread reference
2660 Thread * ModelChecker::get_thread(thread_id_t tid) const
2662 return thread_map->get(id_to_int(tid));
2666 * @brief Get a reference to the Thread in which a ModelAction was executed
2667 * @param act The ModelAction
2668 * @return A Thread reference
2670 Thread * ModelChecker::get_thread(ModelAction *act) const
2672 return get_thread(act->get_tid());
2676 * @brief Check if a Thread is currently enabled
2677 * @param t The Thread to check
2678 * @return True if the Thread is currently enabled
2680 bool ModelChecker::is_enabled(Thread *t) const
2682 return scheduler->is_enabled(t);
2686 * @brief Check if a Thread is currently enabled
2687 * @param tid The ID of the Thread to check
2688 * @return True if the Thread is currently enabled
2690 bool ModelChecker::is_enabled(thread_id_t tid) const
2692 return scheduler->is_enabled(tid);
2696 * Switch from a user-context to the "master thread" context (a.k.a. system
2697 * context). This switch is made with the intention of exploring a particular
2698 * model-checking action (described by a ModelAction object). Must be called
2699 * from a user-thread context.
2701 * @param act The current action that will be explored. May be NULL only if
2702 * trace is exiting via an assertion (see ModelChecker::set_assert and
2703 * ModelChecker::has_asserted).
2704 * @return Return the value returned by the current action
2706 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2709 Thread *old = thread_current();
2710 set_current_action(act);
2711 old->set_state(THREAD_READY);
2712 if (Thread::swap(old, &system_context) < 0) {
2713 perror("swap threads");
2716 return old->get_return_value();
2720 * Takes the next step in the execution, if possible.
2721 * @param curr The current step to take
2722 * @return Returns true (success) if a step was taken and false otherwise.
2724 bool ModelChecker::take_step(ModelAction *curr)
2729 Thread *curr_thrd = get_thread(curr);
2730 ASSERT(curr_thrd->get_state() == THREAD_READY);
2732 curr = check_current_action(curr);
2734 /* Infeasible -> don't take any more steps */
2735 if (is_infeasible())
2737 else if (isfeasibleprefix() && have_bug_reports()) {
2742 if (params.bound != 0)
2743 if (priv->used_sequence_numbers > params.bound)
2746 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2747 scheduler->remove_thread(curr_thrd);
2749 Thread *next_thrd = get_next_thread(curr);
2750 next_thrd = scheduler->next_thread(next_thrd);
2752 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2753 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2756 * Launch end-of-execution release sequence fixups only when there are:
2758 * (1) no more user threads to run (or when execution replay chooses
2759 * the 'model_thread')
2760 * (2) pending release sequences
2761 * (3) pending assertions (i.e., data races)
2762 * (4) no pending promises
2764 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2765 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2766 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2767 pending_rel_seqs->size());
2768 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2769 std::memory_order_seq_cst, NULL, VALUE_NONE,
2771 set_current_action(fixup);
2775 /* next_thrd == NULL -> don't take any more steps */
2779 next_thrd->set_state(THREAD_RUNNING);
2781 if (next_thrd->get_pending() != NULL) {
2782 /* restart a pending action */
2783 set_current_action(next_thrd->get_pending());
2784 next_thrd->set_pending(NULL);
2785 next_thrd->set_state(THREAD_READY);
2789 /* Return false only if swap fails with an error */
2790 return (Thread::swap(&system_context, next_thrd) == 0);
2793 /** Wrapper to run the user's main function, with appropriate arguments */
2794 void user_main_wrapper(void *)
2796 user_main(model->params.argc, model->params.argv);
2799 /** @brief Run ModelChecker for the user program */
2800 void ModelChecker::run()
2804 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2808 /* Run user thread up to its first action */
2809 scheduler->next_thread(t);
2810 Thread::swap(&system_context, t);
2812 /* Wait for all threads to complete */
2813 while (take_step(priv->current_action));
2814 } while (next_execution());