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->enabled_status(t->get_id()) == THREAD_ENABLED) {
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);
724 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
725 mo_graph->rollbackChanges();
726 priv->too_many_reads = false;
730 read_from(curr, reads_from);
731 mo_graph->commitChanges();
732 mo_check_promises(curr->get_tid(), reads_from, NULL);
735 } else if (!second_part_of_rmw) {
736 /* Read from future value */
737 struct future_value fv = curr->get_node()->get_future_value();
738 Promise *promise = new Promise(curr, fv);
740 curr->set_read_from_promise(promise);
741 promises->push_back(promise);
742 mo_graph->startChanges();
743 updated = r_modification_order(curr, promise);
744 mo_graph->commitChanges();
746 get_thread(curr)->set_return_value(value);
752 * Processes a lock, trylock, or unlock model action. @param curr is
753 * the read model action to process.
755 * The try lock operation checks whether the lock is taken. If not,
756 * it falls to the normal lock operation case. If so, it returns
759 * The lock operation has already been checked that it is enabled, so
760 * it just grabs the lock and synchronizes with the previous unlock.
762 * The unlock operation has to re-enable all of the threads that are
763 * waiting on the lock.
765 * @return True if synchronization was updated; false otherwise
767 bool ModelChecker::process_mutex(ModelAction *curr)
769 std::mutex *mutex = NULL;
770 struct std::mutex_state *state = NULL;
772 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
773 mutex = (std::mutex *)curr->get_location();
774 state = mutex->get_state();
775 } else if (curr->is_wait()) {
776 mutex = (std::mutex *)curr->get_value();
777 state = mutex->get_state();
780 switch (curr->get_type()) {
781 case ATOMIC_TRYLOCK: {
782 bool success = !state->islocked;
783 curr->set_try_lock(success);
785 get_thread(curr)->set_return_value(0);
788 get_thread(curr)->set_return_value(1);
790 //otherwise fall into the lock case
792 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
793 assert_bug("Lock access before initialization");
794 state->islocked = true;
795 ModelAction *unlock = get_last_unlock(curr);
796 //synchronize with the previous unlock statement
797 if (unlock != NULL) {
798 curr->synchronize_with(unlock);
803 case ATOMIC_UNLOCK: {
805 state->islocked = false;
806 //wake up the other threads
807 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
808 //activate all the waiting threads
809 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
810 scheduler->wake(get_thread(*rit));
817 state->islocked = false;
818 //wake up the other threads
819 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
820 //activate all the waiting threads
821 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
822 scheduler->wake(get_thread(*rit));
825 //check whether we should go to sleep or not...simulate spurious failures
826 if (curr->get_node()->get_misc() == 0) {
827 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
829 scheduler->sleep(get_thread(curr));
833 case ATOMIC_NOTIFY_ALL: {
834 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
835 //activate all the waiting threads
836 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
837 scheduler->wake(get_thread(*rit));
842 case ATOMIC_NOTIFY_ONE: {
843 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
844 int wakeupthread = curr->get_node()->get_misc();
845 action_list_t::iterator it = waiters->begin();
846 advance(it, wakeupthread);
847 scheduler->wake(get_thread(*it));
858 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
860 /* Do more ambitious checks now that mo is more complete */
861 if (mo_may_allow(writer, reader)) {
862 Node *node = reader->get_node();
864 /* Find an ancestor thread which exists at the time of the reader */
865 Thread *write_thread = get_thread(writer);
866 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
867 write_thread = write_thread->get_parent();
869 struct future_value fv = {
871 writer->get_seq_number() + params.maxfuturedelay,
872 write_thread->get_id(),
874 if (node->add_future_value(fv))
875 set_latest_backtrack(reader);
880 * Process a write ModelAction
881 * @param curr The ModelAction to process
882 * @return True if the mo_graph was updated or promises were resolved
884 bool ModelChecker::process_write(ModelAction *curr)
886 bool updated_mod_order = w_modification_order(curr);
887 bool updated_promises = resolve_promises(curr);
889 if (promises->size() == 0) {
890 for (unsigned int i = 0; i < futurevalues->size(); i++) {
891 struct PendingFutureValue pfv = (*futurevalues)[i];
892 add_future_value(pfv.writer, pfv.act);
894 futurevalues->clear();
897 mo_graph->commitChanges();
898 mo_check_promises(curr->get_tid(), curr, NULL);
900 get_thread(curr)->set_return_value(VALUE_NONE);
901 return updated_mod_order || updated_promises;
905 * Process a fence ModelAction
906 * @param curr The ModelAction to process
907 * @return True if synchronization was updated
909 bool ModelChecker::process_fence(ModelAction *curr)
912 * fence-relaxed: no-op
913 * fence-release: only log the occurence (not in this function), for
914 * use in later synchronization
915 * fence-acquire (this function): search for hypothetical release
918 bool updated = false;
919 if (curr->is_acquire()) {
920 action_list_t *list = action_trace;
921 action_list_t::reverse_iterator rit;
922 /* Find X : is_read(X) && X --sb-> curr */
923 for (rit = list->rbegin(); rit != list->rend(); rit++) {
924 ModelAction *act = *rit;
927 if (act->get_tid() != curr->get_tid())
929 /* Stop at the beginning of the thread */
930 if (act->is_thread_start())
932 /* Stop once we reach a prior fence-acquire */
933 if (act->is_fence() && act->is_acquire())
937 /* read-acquire will find its own release sequences */
938 if (act->is_acquire())
941 /* Establish hypothetical release sequences */
942 rel_heads_list_t release_heads;
943 get_release_seq_heads(curr, act, &release_heads);
944 for (unsigned int i = 0; i < release_heads.size(); i++)
945 if (!curr->synchronize_with(release_heads[i]))
946 set_bad_synchronization();
947 if (release_heads.size() != 0)
955 * @brief Process the current action for thread-related activity
957 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
958 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
959 * synchronization, etc. This function is a no-op for non-THREAD actions
960 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
962 * @param curr The current action
963 * @return True if synchronization was updated or a thread completed
965 bool ModelChecker::process_thread_action(ModelAction *curr)
967 bool updated = false;
969 switch (curr->get_type()) {
970 case THREAD_CREATE: {
971 Thread *th = curr->get_thread_operand();
972 th->set_creation(curr);
973 /* Promises can be satisfied by children */
974 for (unsigned int i = 0; i < promises->size(); i++) {
975 Promise *promise = (*promises)[i];
976 if (promise->thread_is_available(curr->get_tid()))
977 promise->add_thread(th->get_id());
982 Thread *blocking = curr->get_thread_operand();
983 ModelAction *act = get_last_action(blocking->get_id());
984 curr->synchronize_with(act);
985 updated = true; /* trigger rel-seq checks */
988 case THREAD_FINISH: {
989 Thread *th = get_thread(curr);
990 while (!th->wait_list_empty()) {
991 ModelAction *act = th->pop_wait_list();
992 scheduler->wake(get_thread(act));
995 /* Completed thread can't satisfy promises */
996 for (unsigned int i = 0; i < promises->size(); i++) {
997 Promise *promise = (*promises)[i];
998 if (promise->thread_is_available(th->get_id()))
999 if (promise->eliminate_thread(th->get_id()))
1000 priv->failed_promise = true;
1002 updated = true; /* trigger rel-seq checks */
1005 case THREAD_START: {
1006 check_promises(curr->get_tid(), NULL, curr->get_cv());
1017 * @brief Process the current action for release sequence fixup activity
1019 * Performs model-checker release sequence fixups for the current action,
1020 * forcing a single pending release sequence to break (with a given, potential
1021 * "loose" write) or to complete (i.e., synchronize). If a pending release
1022 * sequence forms a complete release sequence, then we must perform the fixup
1023 * synchronization, mo_graph additions, etc.
1025 * @param curr The current action; must be a release sequence fixup action
1026 * @param work_queue The work queue to which to add work items as they are
1029 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1031 const ModelAction *write = curr->get_node()->get_relseq_break();
1032 struct release_seq *sequence = pending_rel_seqs->back();
1033 pending_rel_seqs->pop_back();
1035 ModelAction *acquire = sequence->acquire;
1036 const ModelAction *rf = sequence->rf;
1037 const ModelAction *release = sequence->release;
1041 ASSERT(release->same_thread(rf));
1043 if (write == NULL) {
1045 * @todo Forcing a synchronization requires that we set
1046 * modification order constraints. For instance, we can't allow
1047 * a fixup sequence in which two separate read-acquire
1048 * operations read from the same sequence, where the first one
1049 * synchronizes and the other doesn't. Essentially, we can't
1050 * allow any writes to insert themselves between 'release' and
1054 /* Must synchronize */
1055 if (!acquire->synchronize_with(release)) {
1056 set_bad_synchronization();
1059 /* Re-check all pending release sequences */
1060 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1061 /* Re-check act for mo_graph edges */
1062 work_queue->push_back(MOEdgeWorkEntry(acquire));
1064 /* propagate synchronization to later actions */
1065 action_list_t::reverse_iterator rit = action_trace->rbegin();
1066 for (; (*rit) != acquire; rit++) {
1067 ModelAction *propagate = *rit;
1068 if (acquire->happens_before(propagate)) {
1069 propagate->synchronize_with(acquire);
1070 /* Re-check 'propagate' for mo_graph edges */
1071 work_queue->push_back(MOEdgeWorkEntry(propagate));
1075 /* Break release sequence with new edges:
1076 * release --mo--> write --mo--> rf */
1077 mo_graph->addEdge(release, write);
1078 mo_graph->addEdge(write, rf);
1081 /* See if we have realized a data race */
1086 * Initialize the current action by performing one or more of the following
1087 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1088 * in the NodeStack, manipulating backtracking sets, allocating and
1089 * initializing clock vectors, and computing the promises to fulfill.
1091 * @param curr The current action, as passed from the user context; may be
1092 * freed/invalidated after the execution of this function, with a different
1093 * action "returned" its place (pass-by-reference)
1094 * @return True if curr is a newly-explored action; false otherwise
1096 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1098 ModelAction *newcurr;
1100 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1101 newcurr = process_rmw(*curr);
1104 if (newcurr->is_rmw())
1105 compute_promises(newcurr);
1111 (*curr)->set_seq_number(get_next_seq_num());
1113 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1115 /* First restore type and order in case of RMW operation */
1116 if ((*curr)->is_rmwr())
1117 newcurr->copy_typeandorder(*curr);
1119 ASSERT((*curr)->get_location() == newcurr->get_location());
1120 newcurr->copy_from_new(*curr);
1122 /* Discard duplicate ModelAction; use action from NodeStack */
1125 /* Always compute new clock vector */
1126 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1129 return false; /* Action was explored previously */
1133 /* Always compute new clock vector */
1134 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1136 /* Assign most recent release fence */
1137 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1140 * Perform one-time actions when pushing new ModelAction onto
1143 if (newcurr->is_write())
1144 compute_promises(newcurr);
1145 else if (newcurr->is_relseq_fixup())
1146 compute_relseq_breakwrites(newcurr);
1147 else if (newcurr->is_wait())
1148 newcurr->get_node()->set_misc_max(2);
1149 else if (newcurr->is_notify_one()) {
1150 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1152 return true; /* This was a new ModelAction */
1157 * @brief Establish reads-from relation between two actions
1159 * Perform basic operations involved with establishing a concrete rf relation,
1160 * including setting the ModelAction data and checking for release sequences.
1162 * @param act The action that is reading (must be a read)
1163 * @param rf The action from which we are reading (must be a write)
1165 * @return True if this read established synchronization
1167 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1169 act->set_read_from(rf);
1170 if (rf != NULL && act->is_acquire()) {
1171 rel_heads_list_t release_heads;
1172 get_release_seq_heads(act, act, &release_heads);
1173 int num_heads = release_heads.size();
1174 for (unsigned int i = 0; i < release_heads.size(); i++)
1175 if (!act->synchronize_with(release_heads[i])) {
1176 set_bad_synchronization();
1179 return num_heads > 0;
1185 * @brief Check whether a model action is enabled.
1187 * Checks whether a lock or join operation would be successful (i.e., is the
1188 * lock already locked, or is the joined thread already complete). If not, put
1189 * the action in a waiter list.
1191 * @param curr is the ModelAction to check whether it is enabled.
1192 * @return a bool that indicates whether the action is enabled.
1194 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1195 if (curr->is_lock()) {
1196 std::mutex *lock = (std::mutex *)curr->get_location();
1197 struct std::mutex_state *state = lock->get_state();
1198 if (state->islocked) {
1199 //Stick the action in the appropriate waiting queue
1200 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1203 } else if (curr->get_type() == THREAD_JOIN) {
1204 Thread *blocking = (Thread *)curr->get_location();
1205 if (!blocking->is_complete()) {
1206 blocking->push_wait_list(curr);
1215 * Stores the ModelAction for the current thread action. Call this
1216 * immediately before switching from user- to system-context to pass
1217 * data between them.
1218 * @param act The ModelAction created by the user-thread action
1220 void ModelChecker::set_current_action(ModelAction *act) {
1221 priv->current_action = act;
1225 * This is the heart of the model checker routine. It performs model-checking
1226 * actions corresponding to a given "current action." Among other processes, it
1227 * calculates reads-from relationships, updates synchronization clock vectors,
1228 * forms a memory_order constraints graph, and handles replay/backtrack
1229 * execution when running permutations of previously-observed executions.
1231 * @param curr The current action to process
1232 * @return The ModelAction that is actually executed; may be different than
1233 * curr; may be NULL, if the current action is not enabled to run
1235 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1238 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1240 if (!check_action_enabled(curr)) {
1241 /* Make the execution look like we chose to run this action
1242 * much later, when a lock/join can succeed */
1243 get_thread(curr)->set_pending(curr);
1244 scheduler->sleep(get_thread(curr));
1248 bool newly_explored = initialize_curr_action(&curr);
1254 wake_up_sleeping_actions(curr);
1256 /* Add the action to lists before any other model-checking tasks */
1257 if (!second_part_of_rmw)
1258 add_action_to_lists(curr);
1260 /* Build may_read_from set for newly-created actions */
1261 if (newly_explored && curr->is_read())
1262 build_reads_from_past(curr);
1264 /* Initialize work_queue with the "current action" work */
1265 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1266 while (!work_queue.empty() && !has_asserted()) {
1267 WorkQueueEntry work = work_queue.front();
1268 work_queue.pop_front();
1270 switch (work.type) {
1271 case WORK_CHECK_CURR_ACTION: {
1272 ModelAction *act = work.action;
1273 bool update = false; /* update this location's release seq's */
1274 bool update_all = false; /* update all release seq's */
1276 if (process_thread_action(curr))
1279 if (act->is_read() && process_read(act, second_part_of_rmw))
1282 if (act->is_write() && process_write(act))
1285 if (act->is_fence() && process_fence(act))
1288 if (act->is_mutex_op() && process_mutex(act))
1291 if (act->is_relseq_fixup())
1292 process_relseq_fixup(curr, &work_queue);
1295 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1297 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1300 case WORK_CHECK_RELEASE_SEQ:
1301 resolve_release_sequences(work.location, &work_queue);
1303 case WORK_CHECK_MO_EDGES: {
1304 /** @todo Complete verification of work_queue */
1305 ModelAction *act = work.action;
1306 bool updated = false;
1308 if (act->is_read()) {
1309 const ModelAction *rf = act->get_reads_from();
1310 const Promise *promise = act->get_reads_from_promise();
1312 if (r_modification_order(act, rf))
1314 } else if (promise) {
1315 if (r_modification_order(act, promise))
1319 if (act->is_write()) {
1320 if (w_modification_order(act))
1323 mo_graph->commitChanges();
1326 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1335 check_curr_backtracking(curr);
1336 set_backtracking(curr);
1340 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1342 Node *currnode = curr->get_node();
1343 Node *parnode = currnode->get_parent();
1345 if ((parnode && !parnode->backtrack_empty()) ||
1346 !currnode->misc_empty() ||
1347 !currnode->read_from_empty() ||
1348 !currnode->future_value_empty() ||
1349 !currnode->promise_empty() ||
1350 !currnode->relseq_break_empty()) {
1351 set_latest_backtrack(curr);
1355 bool ModelChecker::promises_expired() const
1357 for (unsigned int i = 0; i < promises->size(); i++) {
1358 Promise *promise = (*promises)[i];
1359 if (promise->get_expiration() < priv->used_sequence_numbers)
1366 * This is the strongest feasibility check available.
1367 * @return whether the current trace (partial or complete) must be a prefix of
1370 bool ModelChecker::isfeasibleprefix() const
1372 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1376 * Print disagnostic information about an infeasible execution
1377 * @param prefix A string to prefix the output with; if NULL, then a default
1378 * message prefix will be provided
1380 void ModelChecker::print_infeasibility(const char *prefix) const
1384 if (mo_graph->checkForCycles())
1385 ptr += sprintf(ptr, "[mo cycle]");
1386 if (priv->failed_promise)
1387 ptr += sprintf(ptr, "[failed promise]");
1388 if (priv->too_many_reads)
1389 ptr += sprintf(ptr, "[too many reads]");
1390 if (priv->bad_synchronization)
1391 ptr += sprintf(ptr, "[bad sw ordering]");
1392 if (promises_expired())
1393 ptr += sprintf(ptr, "[promise expired]");
1394 if (promises->size() != 0)
1395 ptr += sprintf(ptr, "[unresolved promise]");
1397 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1401 * Returns whether the current completed trace is feasible, except for pending
1402 * release sequences.
1404 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1406 return !is_infeasible() && promises->size() == 0;
1410 * Check if the current partial trace is infeasible. Does not check any
1411 * end-of-execution flags, which might rule out the execution. Thus, this is
1412 * useful only for ruling an execution as infeasible.
1413 * @return whether the current partial trace is infeasible.
1415 bool ModelChecker::is_infeasible() const
1417 return mo_graph->checkForCycles() ||
1418 priv->failed_promise ||
1419 priv->too_many_reads ||
1420 priv->bad_synchronization ||
1424 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1425 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1426 ModelAction *lastread = get_last_action(act->get_tid());
1427 lastread->process_rmw(act);
1428 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1429 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1430 mo_graph->commitChanges();
1436 * Checks whether a thread has read from the same write for too many times
1437 * without seeing the effects of a later write.
1440 * 1) there must a different write that we could read from that would satisfy the modification order,
1441 * 2) we must have read from the same value in excess of maxreads times, and
1442 * 3) that other write must have been in the reads_from set for maxreads times.
1444 * If so, we decide that the execution is no longer feasible.
1446 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1448 if (params.maxreads != 0) {
1449 if (curr->get_node()->get_read_from_size() <= 1)
1451 //Must make sure that execution is currently feasible... We could
1452 //accidentally clear by rolling back
1453 if (is_infeasible())
1455 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1456 int tid = id_to_int(curr->get_tid());
1459 if ((int)thrd_lists->size() <= tid)
1461 action_list_t *list = &(*thrd_lists)[tid];
1463 action_list_t::reverse_iterator rit = list->rbegin();
1464 /* Skip past curr */
1465 for (; (*rit) != curr; rit++)
1467 /* go past curr now */
1470 action_list_t::reverse_iterator ritcopy = rit;
1471 //See if we have enough reads from the same value
1473 for (; count < params.maxreads; rit++, count++) {
1474 if (rit == list->rend())
1476 ModelAction *act = *rit;
1477 if (!act->is_read())
1480 if (act->get_reads_from() != rf)
1482 if (act->get_node()->get_read_from_size() <= 1)
1485 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1487 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1489 /* Need a different write */
1493 /* Test to see whether this is a feasible write to read from */
1494 mo_graph->startChanges();
1495 r_modification_order(curr, write);
1496 bool feasiblereadfrom = !is_infeasible();
1497 mo_graph->rollbackChanges();
1499 if (!feasiblereadfrom)
1503 bool feasiblewrite = true;
1504 //new we need to see if this write works for everyone
1506 for (int loop = count; loop > 0; loop--, rit++) {
1507 ModelAction *act = *rit;
1508 bool foundvalue = false;
1509 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1510 if (act->get_node()->get_read_from_at(j) == write) {
1516 feasiblewrite = false;
1520 if (feasiblewrite) {
1521 priv->too_many_reads = true;
1529 * Updates the mo_graph with the constraints imposed from the current
1532 * Basic idea is the following: Go through each other thread and find
1533 * the last action that happened before our read. Two cases:
1535 * (1) The action is a write => that write must either occur before
1536 * the write we read from or be the write we read from.
1538 * (2) The action is a read => the write that that action read from
1539 * must occur before the write we read from or be the same write.
1541 * @param curr The current action. Must be a read.
1542 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1543 * @return True if modification order edges were added; false otherwise
1545 template <typename rf_type>
1546 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1548 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1551 ASSERT(curr->is_read());
1553 /* Last SC fence in the current thread */
1554 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1556 /* Iterate over all threads */
1557 for (i = 0; i < thrd_lists->size(); i++) {
1558 /* Last SC fence in thread i */
1559 ModelAction *last_sc_fence_thread_local = NULL;
1560 if (int_to_id((int)i) != curr->get_tid())
1561 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1563 /* Last SC fence in thread i, before last SC fence in current thread */
1564 ModelAction *last_sc_fence_thread_before = NULL;
1565 if (last_sc_fence_local)
1566 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1568 /* Iterate over actions in thread, starting from most recent */
1569 action_list_t *list = &(*thrd_lists)[i];
1570 action_list_t::reverse_iterator rit;
1571 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1572 ModelAction *act = *rit;
1574 if (act->is_write() && !act->equals(rf) && act != curr) {
1575 /* C++, Section 29.3 statement 5 */
1576 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1577 *act < *last_sc_fence_thread_local) {
1578 added = mo_graph->addEdge(act, rf) || added;
1581 /* C++, Section 29.3 statement 4 */
1582 else if (act->is_seqcst() && last_sc_fence_local &&
1583 *act < *last_sc_fence_local) {
1584 added = mo_graph->addEdge(act, rf) || added;
1587 /* C++, Section 29.3 statement 6 */
1588 else if (last_sc_fence_thread_before &&
1589 *act < *last_sc_fence_thread_before) {
1590 added = mo_graph->addEdge(act, rf) || added;
1596 * Include at most one act per-thread that "happens
1597 * before" curr. Don't consider reflexively.
1599 if (act->happens_before(curr) && act != curr) {
1600 if (act->is_write()) {
1601 if (!act->equals(rf)) {
1602 added = mo_graph->addEdge(act, rf) || added;
1605 const ModelAction *prevreadfrom = act->get_reads_from();
1606 //if the previous read is unresolved, keep going...
1607 if (prevreadfrom == NULL)
1610 if (!prevreadfrom->equals(rf)) {
1611 added = mo_graph->addEdge(prevreadfrom, rf) || added;
1622 /** This method fixes up the modification order when we resolve a
1623 * promises. The basic problem is that actions that occur after the
1624 * read curr could not property add items to the modification order
1627 * So for each thread, we find the earliest item that happens after
1628 * the read curr. This is the item we have to fix up with additional
1629 * constraints. If that action is write, we add a MO edge between
1630 * the Action rf and that action. If the action is a read, we add a
1631 * MO edge between the Action rf, and whatever the read accessed.
1633 * @param curr is the read ModelAction that we are fixing up MO edges for.
1634 * @param rf is the write ModelAction that curr reads from.
1637 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1639 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1641 ASSERT(curr->is_read());
1643 /* Iterate over all threads */
1644 for (i = 0; i < thrd_lists->size(); i++) {
1645 /* Iterate over actions in thread, starting from most recent */
1646 action_list_t *list = &(*thrd_lists)[i];
1647 action_list_t::reverse_iterator rit;
1648 ModelAction *lastact = NULL;
1650 /* Find last action that happens after curr that is either not curr or a rmw */
1651 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1652 ModelAction *act = *rit;
1653 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1659 /* Include at most one act per-thread that "happens before" curr */
1660 if (lastact != NULL) {
1661 if (lastact == curr) {
1662 //Case 1: The resolved read is a RMW, and we need to make sure
1663 //that the write portion of the RMW mod order after rf
1665 mo_graph->addEdge(rf, lastact);
1666 } else if (lastact->is_read()) {
1667 //Case 2: The resolved read is a normal read and the next
1668 //operation is a read, and we need to make sure the value read
1669 //is mod ordered after rf
1671 const ModelAction *postreadfrom = lastact->get_reads_from();
1672 if (postreadfrom != NULL && rf != postreadfrom)
1673 mo_graph->addEdge(rf, postreadfrom);
1675 //Case 3: The resolved read is a normal read and the next
1676 //operation is a write, and we need to make sure that the
1677 //write is mod ordered after rf
1679 mo_graph->addEdge(rf, lastact);
1687 * Updates the mo_graph with the constraints imposed from the current write.
1689 * Basic idea is the following: Go through each other thread and find
1690 * the lastest action that happened before our write. Two cases:
1692 * (1) The action is a write => that write must occur before
1695 * (2) The action is a read => the write that that action read from
1696 * must occur before the current write.
1698 * This method also handles two other issues:
1700 * (I) Sequential Consistency: Making sure that if the current write is
1701 * seq_cst, that it occurs after the previous seq_cst write.
1703 * (II) Sending the write back to non-synchronizing reads.
1705 * @param curr The current action. Must be a write.
1706 * @return True if modification order edges were added; false otherwise
1708 bool ModelChecker::w_modification_order(ModelAction *curr)
1710 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1713 ASSERT(curr->is_write());
1715 if (curr->is_seqcst()) {
1716 /* We have to at least see the last sequentially consistent write,
1717 so we are initialized. */
1718 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1719 if (last_seq_cst != NULL) {
1720 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1724 /* Last SC fence in the current thread */
1725 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1727 /* Iterate over all threads */
1728 for (i = 0; i < thrd_lists->size(); i++) {
1729 /* Last SC fence in thread i, before last SC fence in current thread */
1730 ModelAction *last_sc_fence_thread_before = NULL;
1731 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1732 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1734 /* Iterate over actions in thread, starting from most recent */
1735 action_list_t *list = &(*thrd_lists)[i];
1736 action_list_t::reverse_iterator rit;
1737 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1738 ModelAction *act = *rit;
1741 * 1) If RMW and it actually read from something, then we
1742 * already have all relevant edges, so just skip to next
1745 * 2) If RMW and it didn't read from anything, we should
1746 * whatever edge we can get to speed up convergence.
1748 * 3) If normal write, we need to look at earlier actions, so
1749 * continue processing list.
1751 if (curr->is_rmw()) {
1752 if (curr->get_reads_from() != NULL)
1760 /* C++, Section 29.3 statement 7 */
1761 if (last_sc_fence_thread_before && act->is_write() &&
1762 *act < *last_sc_fence_thread_before) {
1763 added = mo_graph->addEdge(act, curr) || added;
1768 * Include at most one act per-thread that "happens
1771 if (act->happens_before(curr)) {
1773 * Note: if act is RMW, just add edge:
1775 * The following edge should be handled elsewhere:
1776 * readfrom(act) --mo--> act
1778 if (act->is_write())
1779 added = mo_graph->addEdge(act, curr) || added;
1780 else if (act->is_read()) {
1781 //if previous read accessed a null, just keep going
1782 if (act->get_reads_from() == NULL)
1784 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1787 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1788 !act->same_thread(curr)) {
1789 /* We have an action that:
1790 (1) did not happen before us
1791 (2) is a read and we are a write
1792 (3) cannot synchronize with us
1793 (4) is in a different thread
1795 that read could potentially read from our write. Note that
1796 these checks are overly conservative at this point, we'll
1797 do more checks before actually removing the
1801 if (thin_air_constraint_may_allow(curr, act)) {
1802 if (!is_infeasible())
1803 futurevalues->push_back(PendingFutureValue(curr, act));
1804 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1805 add_future_value(curr, act);
1812 * All compatible, thread-exclusive promises must be ordered after any
1813 * concrete stores to the same thread, or else they can be merged with
1816 for (unsigned int i = 0; i < promises->size(); i++)
1817 if ((*promises)[i]->is_compatible_exclusive(curr))
1818 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1823 /** Arbitrary reads from the future are not allowed. Section 29.3
1824 * part 9 places some constraints. This method checks one result of constraint
1825 * constraint. Others require compiler support. */
1826 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1828 if (!writer->is_rmw())
1831 if (!reader->is_rmw())
1834 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1835 if (search == reader)
1837 if (search->get_tid() == reader->get_tid() &&
1838 search->happens_before(reader))
1846 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1847 * some constraints. This method checks one the following constraint (others
1848 * require compiler support):
1850 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1852 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1854 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1856 /* Iterate over all threads */
1857 for (i = 0; i < thrd_lists->size(); i++) {
1858 const ModelAction *write_after_read = NULL;
1860 /* Iterate over actions in thread, starting from most recent */
1861 action_list_t *list = &(*thrd_lists)[i];
1862 action_list_t::reverse_iterator rit;
1863 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1864 ModelAction *act = *rit;
1866 /* Don't disallow due to act == reader */
1867 if (!reader->happens_before(act) || reader == act)
1869 else if (act->is_write())
1870 write_after_read = act;
1871 else if (act->is_read() && act->get_reads_from() != NULL)
1872 write_after_read = act->get_reads_from();
1875 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1882 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1883 * The ModelAction under consideration is expected to be taking part in
1884 * release/acquire synchronization as an object of the "reads from" relation.
1885 * Note that this can only provide release sequence support for RMW chains
1886 * which do not read from the future, as those actions cannot be traced until
1887 * their "promise" is fulfilled. Similarly, we may not even establish the
1888 * presence of a release sequence with certainty, as some modification order
1889 * constraints may be decided further in the future. Thus, this function
1890 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1891 * and a boolean representing certainty.
1893 * @param rf The action that might be part of a release sequence. Must be a
1895 * @param release_heads A pass-by-reference style return parameter. After
1896 * execution of this function, release_heads will contain the heads of all the
1897 * relevant release sequences, if any exists with certainty
1898 * @param pending A pass-by-reference style return parameter which is only used
1899 * when returning false (i.e., uncertain). Returns most information regarding
1900 * an uncertain release sequence, including any write operations that might
1901 * break the sequence.
1902 * @return true, if the ModelChecker is certain that release_heads is complete;
1905 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1906 rel_heads_list_t *release_heads,
1907 struct release_seq *pending) const
1909 /* Only check for release sequences if there are no cycles */
1910 if (mo_graph->checkForCycles())
1914 ASSERT(rf->is_write());
1916 if (rf->is_release())
1917 release_heads->push_back(rf);
1918 else if (rf->get_last_fence_release())
1919 release_heads->push_back(rf->get_last_fence_release());
1921 break; /* End of RMW chain */
1923 /** @todo Need to be smarter here... In the linux lock
1924 * example, this will run to the beginning of the program for
1926 /** @todo The way to be smarter here is to keep going until 1
1927 * thread has a release preceded by an acquire and you've seen
1930 /* acq_rel RMW is a sufficient stopping condition */
1931 if (rf->is_acquire() && rf->is_release())
1932 return true; /* complete */
1934 rf = rf->get_reads_from();
1937 /* read from future: need to settle this later */
1939 return false; /* incomplete */
1942 if (rf->is_release())
1943 return true; /* complete */
1945 /* else relaxed write
1946 * - check for fence-release in the same thread (29.8, stmt. 3)
1947 * - check modification order for contiguous subsequence
1948 * -> rf must be same thread as release */
1950 const ModelAction *fence_release = rf->get_last_fence_release();
1951 /* Synchronize with a fence-release unconditionally; we don't need to
1952 * find any more "contiguous subsequence..." for it */
1954 release_heads->push_back(fence_release);
1956 int tid = id_to_int(rf->get_tid());
1957 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1958 action_list_t *list = &(*thrd_lists)[tid];
1959 action_list_t::const_reverse_iterator rit;
1961 /* Find rf in the thread list */
1962 rit = std::find(list->rbegin(), list->rend(), rf);
1963 ASSERT(rit != list->rend());
1965 /* Find the last {write,fence}-release */
1966 for (; rit != list->rend(); rit++) {
1967 if (fence_release && *(*rit) < *fence_release)
1969 if ((*rit)->is_release())
1972 if (rit == list->rend()) {
1973 /* No write-release in this thread */
1974 return true; /* complete */
1975 } else if (fence_release && *(*rit) < *fence_release) {
1976 /* The fence-release is more recent (and so, "stronger") than
1977 * the most recent write-release */
1978 return true; /* complete */
1979 } /* else, need to establish contiguous release sequence */
1980 ModelAction *release = *rit;
1982 ASSERT(rf->same_thread(release));
1984 pending->writes.clear();
1986 bool certain = true;
1987 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1988 if (id_to_int(rf->get_tid()) == (int)i)
1990 list = &(*thrd_lists)[i];
1992 /* Can we ensure no future writes from this thread may break
1993 * the release seq? */
1994 bool future_ordered = false;
1996 ModelAction *last = get_last_action(int_to_id(i));
1997 Thread *th = get_thread(int_to_id(i));
1998 if ((last && rf->happens_before(last)) ||
2001 future_ordered = true;
2003 ASSERT(!th->is_model_thread() || future_ordered);
2005 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2006 const ModelAction *act = *rit;
2007 /* Reach synchronization -> this thread is complete */
2008 if (act->happens_before(release))
2010 if (rf->happens_before(act)) {
2011 future_ordered = true;
2015 /* Only non-RMW writes can break release sequences */
2016 if (!act->is_write() || act->is_rmw())
2019 /* Check modification order */
2020 if (mo_graph->checkReachable(rf, act)) {
2021 /* rf --mo--> act */
2022 future_ordered = true;
2025 if (mo_graph->checkReachable(act, release))
2026 /* act --mo--> release */
2028 if (mo_graph->checkReachable(release, act) &&
2029 mo_graph->checkReachable(act, rf)) {
2030 /* release --mo-> act --mo--> rf */
2031 return true; /* complete */
2033 /* act may break release sequence */
2034 pending->writes.push_back(act);
2037 if (!future_ordered)
2038 certain = false; /* This thread is uncertain */
2042 release_heads->push_back(release);
2043 pending->writes.clear();
2045 pending->release = release;
2052 * An interface for getting the release sequence head(s) with which a
2053 * given ModelAction must synchronize. This function only returns a non-empty
2054 * result when it can locate a release sequence head with certainty. Otherwise,
2055 * it may mark the internal state of the ModelChecker so that it will handle
2056 * the release sequence at a later time, causing @a acquire to update its
2057 * synchronization at some later point in execution.
2059 * @param acquire The 'acquire' action that may synchronize with a release
2061 * @param read The read action that may read from a release sequence; this may
2062 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2063 * when 'acquire' is a fence-acquire)
2064 * @param release_heads A pass-by-reference return parameter. Will be filled
2065 * with the head(s) of the release sequence(s), if they exists with certainty.
2066 * @see ModelChecker::release_seq_heads
2068 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2069 ModelAction *read, rel_heads_list_t *release_heads)
2071 const ModelAction *rf = read->get_reads_from();
2072 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2073 sequence->acquire = acquire;
2074 sequence->read = read;
2076 if (!release_seq_heads(rf, release_heads, sequence)) {
2077 /* add act to 'lazy checking' list */
2078 pending_rel_seqs->push_back(sequence);
2080 snapshot_free(sequence);
2085 * Attempt to resolve all stashed operations that might synchronize with a
2086 * release sequence for a given location. This implements the "lazy" portion of
2087 * determining whether or not a release sequence was contiguous, since not all
2088 * modification order information is present at the time an action occurs.
2090 * @param location The location/object that should be checked for release
2091 * sequence resolutions. A NULL value means to check all locations.
2092 * @param work_queue The work queue to which to add work items as they are
2094 * @return True if any updates occurred (new synchronization, new mo_graph
2097 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2099 bool updated = false;
2100 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2101 while (it != pending_rel_seqs->end()) {
2102 struct release_seq *pending = *it;
2103 ModelAction *acquire = pending->acquire;
2104 const ModelAction *read = pending->read;
2106 /* Only resolve sequences on the given location, if provided */
2107 if (location && read->get_location() != location) {
2112 const ModelAction *rf = read->get_reads_from();
2113 rel_heads_list_t release_heads;
2115 complete = release_seq_heads(rf, &release_heads, pending);
2116 for (unsigned int i = 0; i < release_heads.size(); i++) {
2117 if (!acquire->has_synchronized_with(release_heads[i])) {
2118 if (acquire->synchronize_with(release_heads[i]))
2121 set_bad_synchronization();
2126 /* Re-check all pending release sequences */
2127 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2128 /* Re-check read-acquire for mo_graph edges */
2129 if (acquire->is_read())
2130 work_queue->push_back(MOEdgeWorkEntry(acquire));
2132 /* propagate synchronization to later actions */
2133 action_list_t::reverse_iterator rit = action_trace->rbegin();
2134 for (; (*rit) != acquire; rit++) {
2135 ModelAction *propagate = *rit;
2136 if (acquire->happens_before(propagate)) {
2137 propagate->synchronize_with(acquire);
2138 /* Re-check 'propagate' for mo_graph edges */
2139 work_queue->push_back(MOEdgeWorkEntry(propagate));
2144 it = pending_rel_seqs->erase(it);
2145 snapshot_free(pending);
2151 // If we resolved promises or data races, see if we have realized a data race.
2158 * Performs various bookkeeping operations for the current ModelAction. For
2159 * instance, adds action to the per-object, per-thread action vector and to the
2160 * action trace list of all thread actions.
2162 * @param act is the ModelAction to add.
2164 void ModelChecker::add_action_to_lists(ModelAction *act)
2166 int tid = id_to_int(act->get_tid());
2167 ModelAction *uninit = NULL;
2169 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2170 if (list->empty() && act->is_atomic_var()) {
2171 uninit = new_uninitialized_action(act->get_location());
2172 uninit_id = id_to_int(uninit->get_tid());
2173 list->push_back(uninit);
2175 list->push_back(act);
2177 action_trace->push_back(act);
2179 action_trace->push_front(uninit);
2181 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2182 if (tid >= (int)vec->size())
2183 vec->resize(priv->next_thread_id);
2184 (*vec)[tid].push_back(act);
2186 (*vec)[uninit_id].push_front(uninit);
2188 if ((int)thrd_last_action->size() <= tid)
2189 thrd_last_action->resize(get_num_threads());
2190 (*thrd_last_action)[tid] = act;
2192 (*thrd_last_action)[uninit_id] = uninit;
2194 if (act->is_fence() && act->is_release()) {
2195 if ((int)thrd_last_fence_release->size() <= tid)
2196 thrd_last_fence_release->resize(get_num_threads());
2197 (*thrd_last_fence_release)[tid] = act;
2200 if (act->is_wait()) {
2201 void *mutex_loc = (void *) act->get_value();
2202 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2204 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2205 if (tid >= (int)vec->size())
2206 vec->resize(priv->next_thread_id);
2207 (*vec)[tid].push_back(act);
2212 * @brief Get the last action performed by a particular Thread
2213 * @param tid The thread ID of the Thread in question
2214 * @return The last action in the thread
2216 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2218 int threadid = id_to_int(tid);
2219 if (threadid < (int)thrd_last_action->size())
2220 return (*thrd_last_action)[id_to_int(tid)];
2226 * @brief Get the last fence release performed by a particular Thread
2227 * @param tid The thread ID of the Thread in question
2228 * @return The last fence release in the thread, if one exists; NULL otherwise
2230 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2232 int threadid = id_to_int(tid);
2233 if (threadid < (int)thrd_last_fence_release->size())
2234 return (*thrd_last_fence_release)[id_to_int(tid)];
2240 * Gets the last memory_order_seq_cst write (in the total global sequence)
2241 * performed on a particular object (i.e., memory location), not including the
2243 * @param curr The current ModelAction; also denotes the object location to
2245 * @return The last seq_cst write
2247 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2249 void *location = curr->get_location();
2250 action_list_t *list = get_safe_ptr_action(obj_map, location);
2251 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2252 action_list_t::reverse_iterator rit;
2253 for (rit = list->rbegin(); rit != list->rend(); rit++)
2254 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2260 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2261 * performed in a particular thread, prior to a particular fence.
2262 * @param tid The ID of the thread to check
2263 * @param before_fence The fence from which to begin the search; if NULL, then
2264 * search for the most recent fence in the thread.
2265 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2267 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2269 /* All fences should have NULL location */
2270 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2271 action_list_t::reverse_iterator rit = list->rbegin();
2274 for (; rit != list->rend(); rit++)
2275 if (*rit == before_fence)
2278 ASSERT(*rit == before_fence);
2282 for (; rit != list->rend(); rit++)
2283 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2289 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2290 * location). This function identifies the mutex according to the current
2291 * action, which is presumed to perform on the same mutex.
2292 * @param curr The current ModelAction; also denotes the object location to
2294 * @return The last unlock operation
2296 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2298 void *location = curr->get_location();
2299 action_list_t *list = get_safe_ptr_action(obj_map, location);
2300 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2301 action_list_t::reverse_iterator rit;
2302 for (rit = list->rbegin(); rit != list->rend(); rit++)
2303 if ((*rit)->is_unlock() || (*rit)->is_wait())
2308 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2310 ModelAction *parent = get_last_action(tid);
2312 parent = get_thread(tid)->get_creation();
2317 * Returns the clock vector for a given thread.
2318 * @param tid The thread whose clock vector we want
2319 * @return Desired clock vector
2321 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2323 return get_parent_action(tid)->get_cv();
2327 * Resolve a set of Promises with a current write. The set is provided in the
2328 * Node corresponding to @a write.
2329 * @param write The ModelAction that is fulfilling Promises
2330 * @return True if promises were resolved; false otherwise
2332 bool ModelChecker::resolve_promises(ModelAction *write)
2334 bool haveResolved = false;
2335 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2337 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2338 Promise *promise = (*promises)[promise_index];
2339 if (write->get_node()->get_promise(i)) {
2340 ModelAction *read = promise->get_action();
2341 if (read->is_rmw()) {
2342 mo_graph->addRMWEdge(write, read);
2344 read_from(read, write);
2345 //First fix up the modification order for actions that happened
2347 r_modification_order(read, write);
2348 //Next fix up the modification order for actions that happened
2350 post_r_modification_order(read, write);
2351 //Make sure the promise's value matches the write's value
2352 ASSERT(promise->is_compatible(write));
2355 promises->erase(promises->begin() + promise_index);
2356 actions_to_check.push_back(read);
2358 haveResolved = true;
2363 //Check whether reading these writes has made threads unable to
2366 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2367 ModelAction *read = actions_to_check[i];
2368 mo_check_promises(read->get_tid(), write, read);
2371 return haveResolved;
2375 * Compute the set of promises that could potentially be satisfied by this
2376 * action. Note that the set computation actually appears in the Node, not in
2378 * @param curr The ModelAction that may satisfy promises
2380 void ModelChecker::compute_promises(ModelAction *curr)
2382 for (unsigned int i = 0; i < promises->size(); i++) {
2383 Promise *promise = (*promises)[i];
2384 const ModelAction *act = promise->get_action();
2385 if (!act->happens_before(curr) &&
2387 !act->could_synchronize_with(curr) &&
2388 !act->same_thread(curr) &&
2389 act->get_location() == curr->get_location() &&
2390 promise->get_value() == curr->get_value()) {
2391 curr->get_node()->set_promise(i, act->is_rmw());
2396 /** Checks promises in response to change in ClockVector Threads. */
2397 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2399 for (unsigned int i = 0; i < promises->size(); i++) {
2400 Promise *promise = (*promises)[i];
2401 const ModelAction *act = promise->get_action();
2402 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2403 merge_cv->synchronized_since(act)) {
2404 if (promise->eliminate_thread(tid)) {
2405 //Promise has failed
2406 priv->failed_promise = true;
2413 void ModelChecker::check_promises_thread_disabled()
2415 for (unsigned int i = 0; i < promises->size(); i++) {
2416 Promise *promise = (*promises)[i];
2417 if (promise->has_failed()) {
2418 priv->failed_promise = true;
2425 * @brief Checks promises in response to addition to modification order for
2430 * pthread is the thread that performed the read that created the promise
2432 * pread is the read that created the promise
2434 * pwrite is either the first write to same location as pread by
2435 * pthread that is sequenced after pread or the write read by the
2436 * first read to the same location as pread by pthread that is
2437 * sequenced after pread.
2439 * 1. If tid=pthread, then we check what other threads are reachable
2440 * through the mod order starting with pwrite. Those threads cannot
2441 * perform a write that will resolve the promise due to modification
2442 * order constraints.
2444 * 2. If the tid is not pthread, we check whether pwrite can reach the
2445 * action write through the modification order. If so, that thread
2446 * cannot perform a future write that will resolve the promise due to
2447 * modificatin order constraints.
2449 * @param tid The thread that either read from the model action write, or
2450 * actually did the model action write.
2452 * @param write The ModelAction representing the relevant write.
2453 * @param read The ModelAction that reads a promised write, or NULL otherwise.
2455 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write, const ModelAction *read)
2457 void *location = write->get_location();
2458 for (unsigned int i = 0; i < promises->size(); i++) {
2459 Promise *promise = (*promises)[i];
2460 const ModelAction *act = promise->get_action();
2462 // Is this promise on the same location?
2463 if (act->get_location() != location)
2466 // same thread as the promise
2467 if (act->get_tid() == tid) {
2468 // make sure that the reader of this write happens after the promise
2469 if ((read == NULL) || (promise->get_action()->happens_before(read))) {
2470 // do we have a pwrite for the promise, if not, set it
2471 if (promise->get_write() == NULL) {
2472 promise->set_write(write);
2473 // The pwrite cannot happen before the promise
2474 if (write->happens_before(act) && (write != act)) {
2475 priv->failed_promise = true;
2480 if (mo_graph->checkPromise(write, promise)) {
2481 priv->failed_promise = true;
2487 // Don't do any lookups twice for the same thread
2488 if (!promise->thread_is_available(tid))
2491 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2492 if (promise->eliminate_thread(tid)) {
2493 priv->failed_promise = true;
2501 * Compute the set of writes that may break the current pending release
2502 * sequence. This information is extracted from previou release sequence
2505 * @param curr The current ModelAction. Must be a release sequence fixup
2508 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2510 if (pending_rel_seqs->empty())
2513 struct release_seq *pending = pending_rel_seqs->back();
2514 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2515 const ModelAction *write = pending->writes[i];
2516 curr->get_node()->add_relseq_break(write);
2519 /* NULL means don't break the sequence; just synchronize */
2520 curr->get_node()->add_relseq_break(NULL);
2524 * Build up an initial set of all past writes that this 'read' action may read
2525 * from. This set is determined by the clock vector's "happens before"
2527 * @param curr is the current ModelAction that we are exploring; it must be a
2530 void ModelChecker::build_reads_from_past(ModelAction *curr)
2532 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2534 ASSERT(curr->is_read());
2536 ModelAction *last_sc_write = NULL;
2538 if (curr->is_seqcst())
2539 last_sc_write = get_last_seq_cst_write(curr);
2541 /* Iterate over all threads */
2542 for (i = 0; i < thrd_lists->size(); i++) {
2543 /* Iterate over actions in thread, starting from most recent */
2544 action_list_t *list = &(*thrd_lists)[i];
2545 action_list_t::reverse_iterator rit;
2546 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2547 ModelAction *act = *rit;
2549 /* Only consider 'write' actions */
2550 if (!act->is_write() || act == curr)
2553 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2554 bool allow_read = true;
2556 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2558 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2562 curr->get_node()->add_read_from(act);
2564 /* Include at most one act per-thread that "happens before" curr */
2565 if (act->happens_before(curr))
2570 if (DBG_ENABLED()) {
2571 model_print("Reached read action:\n");
2573 model_print("Printing may_read_from\n");
2574 curr->get_node()->print_may_read_from();
2575 model_print("End printing may_read_from\n");
2579 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2582 /* UNINIT actions don't have a Node, and they never sleep */
2583 if (write->is_uninitialized())
2585 Node *prevnode = write->get_node()->get_parent();
2587 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2588 if (write->is_release() && thread_sleep)
2590 if (!write->is_rmw()) {
2593 if (write->get_reads_from() == NULL)
2595 write = write->get_reads_from();
2600 * @brief Create a new action representing an uninitialized atomic
2601 * @param location The memory location of the atomic object
2602 * @return A pointer to a new ModelAction
2604 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2606 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2607 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2608 act->create_cv(NULL);
2612 static void print_list(action_list_t *list)
2614 action_list_t::iterator it;
2616 model_print("---------------------------------------------------------------------\n");
2618 unsigned int hash = 0;
2620 for (it = list->begin(); it != list->end(); it++) {
2622 hash = hash^(hash<<3)^((*it)->hash());
2624 model_print("HASH %u\n", hash);
2625 model_print("---------------------------------------------------------------------\n");
2628 #if SUPPORT_MOD_ORDER_DUMP
2629 void ModelChecker::dumpGraph(char *filename) const
2632 sprintf(buffer, "%s.dot", filename);
2633 FILE *file = fopen(buffer, "w");
2634 fprintf(file, "digraph %s {\n", filename);
2635 mo_graph->dumpNodes(file);
2636 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2638 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2639 ModelAction *action = *it;
2640 if (action->is_read()) {
2641 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2642 if (action->get_reads_from() != NULL)
2643 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2645 if (thread_array[action->get_tid()] != NULL) {
2646 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2649 thread_array[action->get_tid()] = action;
2651 fprintf(file, "}\n");
2652 model_free(thread_array);
2657 /** @brief Prints an execution trace summary. */
2658 void ModelChecker::print_summary() const
2660 #if SUPPORT_MOD_ORDER_DUMP
2661 char buffername[100];
2662 sprintf(buffername, "exec%04u", stats.num_total);
2663 mo_graph->dumpGraphToFile(buffername);
2664 sprintf(buffername, "graph%04u", stats.num_total);
2665 dumpGraph(buffername);
2668 model_print("Execution %d:", stats.num_total);
2669 if (isfeasibleprefix())
2672 print_infeasibility(" INFEASIBLE");
2673 print_list(action_trace);
2678 * Add a Thread to the system for the first time. Should only be called once
2680 * @param t The Thread to add
2682 void ModelChecker::add_thread(Thread *t)
2684 thread_map->put(id_to_int(t->get_id()), t);
2685 scheduler->add_thread(t);
2689 * Removes a thread from the scheduler.
2690 * @param the thread to remove.
2692 void ModelChecker::remove_thread(Thread *t)
2694 scheduler->remove_thread(t);
2698 * @brief Get a Thread reference by its ID
2699 * @param tid The Thread's ID
2700 * @return A Thread reference
2702 Thread * ModelChecker::get_thread(thread_id_t tid) const
2704 return thread_map->get(id_to_int(tid));
2708 * @brief Get a reference to the Thread in which a ModelAction was executed
2709 * @param act The ModelAction
2710 * @return A Thread reference
2712 Thread * ModelChecker::get_thread(const ModelAction *act) const
2714 return get_thread(act->get_tid());
2718 * @brief Check if a Thread is currently enabled
2719 * @param t The Thread to check
2720 * @return True if the Thread is currently enabled
2722 bool ModelChecker::is_enabled(Thread *t) const
2724 return scheduler->is_enabled(t);
2728 * @brief Check if a Thread is currently enabled
2729 * @param tid The ID of the Thread to check
2730 * @return True if the Thread is currently enabled
2732 bool ModelChecker::is_enabled(thread_id_t tid) const
2734 return scheduler->is_enabled(tid);
2738 * Switch from a user-context to the "master thread" context (a.k.a. system
2739 * context). This switch is made with the intention of exploring a particular
2740 * model-checking action (described by a ModelAction object). Must be called
2741 * from a user-thread context.
2743 * @param act The current action that will be explored. May be NULL only if
2744 * trace is exiting via an assertion (see ModelChecker::set_assert and
2745 * ModelChecker::has_asserted).
2746 * @return Return the value returned by the current action
2748 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2751 Thread *old = thread_current();
2752 set_current_action(act);
2753 old->set_state(THREAD_READY);
2754 if (Thread::swap(old, &system_context) < 0) {
2755 perror("swap threads");
2758 return old->get_return_value();
2762 * Takes the next step in the execution, if possible.
2763 * @param curr The current step to take
2764 * @return Returns true (success) if a step was taken and false otherwise.
2766 bool ModelChecker::take_step(ModelAction *curr)
2771 Thread *curr_thrd = get_thread(curr);
2772 ASSERT(curr_thrd->get_state() == THREAD_READY);
2774 curr = check_current_action(curr);
2776 /* Infeasible -> don't take any more steps */
2777 if (is_infeasible())
2779 else if (isfeasibleprefix() && have_bug_reports()) {
2784 if (params.bound != 0)
2785 if (priv->used_sequence_numbers > params.bound)
2788 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2789 scheduler->remove_thread(curr_thrd);
2791 Thread *next_thrd = get_next_thread(curr);
2792 next_thrd = scheduler->next_thread(next_thrd);
2794 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2795 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2798 * Launch end-of-execution release sequence fixups only when there are:
2800 * (1) no more user threads to run (or when execution replay chooses
2801 * the 'model_thread')
2802 * (2) pending release sequences
2803 * (3) pending assertions (i.e., data races)
2804 * (4) no pending promises
2806 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2807 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2808 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2809 pending_rel_seqs->size());
2810 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2811 std::memory_order_seq_cst, NULL, VALUE_NONE,
2813 set_current_action(fixup);
2817 /* next_thrd == NULL -> don't take any more steps */
2821 next_thrd->set_state(THREAD_RUNNING);
2823 if (next_thrd->get_pending() != NULL) {
2824 /* restart a pending action */
2825 set_current_action(next_thrd->get_pending());
2826 next_thrd->set_pending(NULL);
2827 next_thrd->set_state(THREAD_READY);
2831 /* Return false only if swap fails with an error */
2832 return (Thread::swap(&system_context, next_thrd) == 0);
2835 /** Wrapper to run the user's main function, with appropriate arguments */
2836 void user_main_wrapper(void *)
2838 user_main(model->params.argc, model->params.argv);
2841 /** @brief Run ModelChecker for the user program */
2842 void ModelChecker::run()
2846 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2850 /* Run user thread up to its first action */
2851 scheduler->next_thread(t);
2852 Thread::swap(&system_context, t);
2854 /* Wait for all threads to complete */
2855 while (take_step(priv->current_action));
2856 } while (next_execution());