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() :
42 /* First thread created will have id INITIAL_THREAD_ID */
43 next_thread_id(INITIAL_THREAD_ID),
44 used_sequence_numbers(0),
48 failed_promise(false),
49 too_many_reads(false),
50 no_valid_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 unsigned int next_thread_id;
62 modelclock_t used_sequence_numbers;
63 ModelAction *next_backtrack;
64 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
65 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 get_thread(curr);
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()) {
297 thr->get_pending()->set_sleep_flag();
302 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
304 for (unsigned int i = 0; i < get_num_threads(); i++) {
305 Thread *thr = get_thread(int_to_id(i));
306 if (scheduler->is_sleep_set(thr)) {
307 ModelAction *pending_act = thr->get_pending();
308 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
309 //Remove this thread from sleep set
310 scheduler->remove_sleep(thr);
315 /** @brief Alert the model-checker that an incorrectly-ordered
316 * synchronization was made */
317 void ModelChecker::set_bad_synchronization()
319 priv->bad_synchronization = true;
322 bool ModelChecker::has_asserted() const
324 return priv->asserted;
327 void ModelChecker::set_assert()
329 priv->asserted = true;
333 * Check if we are in a deadlock. Should only be called at the end of an
334 * execution, although it should not give false positives in the middle of an
335 * execution (there should be some ENABLED thread).
337 * @return True if program is in a deadlock; false otherwise
339 bool ModelChecker::is_deadlocked() const
341 bool blocking_threads = false;
342 for (unsigned int i = 0; i < get_num_threads(); i++) {
343 thread_id_t tid = int_to_id(i);
346 Thread *t = get_thread(tid);
347 if (!t->is_model_thread() && t->get_pending())
348 blocking_threads = true;
350 return blocking_threads;
354 * Check if this is a complete execution. That is, have all thread completed
355 * execution (rather than exiting because sleep sets have forced a redundant
358 * @return True if the execution is complete.
360 bool ModelChecker::is_complete_execution() const
362 for (unsigned int i = 0; i < get_num_threads(); i++)
363 if (is_enabled(int_to_id(i)))
369 * @brief Assert a bug in the executing program.
371 * Use this function to assert any sort of bug in the user program. If the
372 * current trace is feasible (actually, a prefix of some feasible execution),
373 * then this execution will be aborted, printing the appropriate message. If
374 * the current trace is not yet feasible, the error message will be stashed and
375 * printed if the execution ever becomes feasible.
377 * @param msg Descriptive message for the bug (do not include newline char)
378 * @return True if bug is immediately-feasible
380 bool ModelChecker::assert_bug(const char *msg)
382 priv->bugs.push_back(new bug_message(msg));
384 if (isfeasibleprefix()) {
392 * @brief Assert a bug in the executing program, asserted by a user thread
393 * @see ModelChecker::assert_bug
394 * @param msg Descriptive message for the bug (do not include newline char)
396 void ModelChecker::assert_user_bug(const char *msg)
398 /* If feasible bug, bail out now */
400 switch_to_master(NULL);
403 /** @return True, if any bugs have been reported for this execution */
404 bool ModelChecker::have_bug_reports() const
406 return priv->bugs.size() != 0;
409 /** @brief Print bug report listing for this execution (if any bugs exist) */
410 void ModelChecker::print_bugs() const
412 if (have_bug_reports()) {
413 model_print("Bug report: %zu bug%s detected\n",
415 priv->bugs.size() > 1 ? "s" : "");
416 for (unsigned int i = 0; i < priv->bugs.size(); i++)
417 priv->bugs[i]->print();
422 * @brief Record end-of-execution stats
424 * Must be run when exiting an execution. Records various stats.
425 * @see struct execution_stats
427 void ModelChecker::record_stats()
430 if (!isfeasibleprefix())
431 stats.num_infeasible++;
432 else if (have_bug_reports())
433 stats.num_buggy_executions++;
434 else if (is_complete_execution())
435 stats.num_complete++;
437 stats.num_redundant++;
440 /** @brief Print execution stats */
441 void ModelChecker::print_stats() const
443 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
444 model_print("Number of redundant executions: %d\n", stats.num_redundant);
445 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
446 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
447 model_print("Total executions: %d\n", stats.num_total);
448 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
452 * @brief End-of-exeuction print
453 * @param printbugs Should any existing bugs be printed?
455 void ModelChecker::print_execution(bool printbugs) const
457 print_program_output();
459 if (DBG_ENABLED() || params.verbose) {
460 model_print("Earliest divergence point since last feasible execution:\n");
461 if (earliest_diverge)
462 earliest_diverge->print();
464 model_print("(Not set)\n");
470 /* Don't print invalid bugs */
479 * Queries the model-checker for more executions to explore and, if one
480 * exists, resets the model-checker state to execute a new execution.
482 * @return If there are more executions to explore, return true. Otherwise,
485 bool ModelChecker::next_execution()
488 /* Is this execution a feasible execution that's worth bug-checking? */
489 bool complete = isfeasibleprefix() && (is_complete_execution() ||
492 /* End-of-execution bug checks */
495 assert_bug("Deadlock detected");
503 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
504 print_execution(complete);
506 clear_program_output();
509 earliest_diverge = NULL;
511 if ((diverge = get_next_backtrack()) == NULL)
515 model_print("Next execution will diverge at:\n");
519 reset_to_initial_state();
523 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
525 switch (act->get_type()) {
530 /* Optimization: relaxed operations don't need backtracking */
531 if (act->is_relaxed())
533 /* linear search: from most recent to oldest */
534 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
535 action_list_t::reverse_iterator rit;
536 for (rit = list->rbegin(); rit != list->rend(); rit++) {
537 ModelAction *prev = *rit;
538 if (prev->could_synchronize_with(act))
544 case ATOMIC_TRYLOCK: {
545 /* linear search: from most recent to oldest */
546 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
547 action_list_t::reverse_iterator rit;
548 for (rit = list->rbegin(); rit != list->rend(); rit++) {
549 ModelAction *prev = *rit;
550 if (act->is_conflicting_lock(prev))
555 case ATOMIC_UNLOCK: {
556 /* linear search: from most recent to oldest */
557 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
558 action_list_t::reverse_iterator rit;
559 for (rit = list->rbegin(); rit != list->rend(); rit++) {
560 ModelAction *prev = *rit;
561 if (!act->same_thread(prev) && prev->is_failed_trylock())
567 /* linear search: from most recent to oldest */
568 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
569 action_list_t::reverse_iterator rit;
570 for (rit = list->rbegin(); rit != list->rend(); rit++) {
571 ModelAction *prev = *rit;
572 if (!act->same_thread(prev) && prev->is_failed_trylock())
574 if (!act->same_thread(prev) && prev->is_notify())
580 case ATOMIC_NOTIFY_ALL:
581 case ATOMIC_NOTIFY_ONE: {
582 /* linear search: from most recent to oldest */
583 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
584 action_list_t::reverse_iterator rit;
585 for (rit = list->rbegin(); rit != list->rend(); rit++) {
586 ModelAction *prev = *rit;
587 if (!act->same_thread(prev) && prev->is_wait())
598 /** This method finds backtracking points where we should try to
599 * reorder the parameter ModelAction against.
601 * @param the ModelAction to find backtracking points for.
603 void ModelChecker::set_backtracking(ModelAction *act)
605 Thread *t = get_thread(act);
606 ModelAction *prev = get_last_conflict(act);
610 Node *node = prev->get_node()->get_parent();
612 int low_tid, high_tid;
613 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
614 low_tid = id_to_int(act->get_tid());
615 high_tid = low_tid + 1;
618 high_tid = get_num_threads();
621 for (int i = low_tid; i < high_tid; i++) {
622 thread_id_t tid = int_to_id(i);
624 /* Make sure this thread can be enabled here. */
625 if (i >= node->get_num_threads())
628 /* Don't backtrack into a point where the thread is disabled or sleeping. */
629 if (node->enabled_status(tid) != THREAD_ENABLED)
632 /* Check if this has been explored already */
633 if (node->has_been_explored(tid))
636 /* See if fairness allows */
637 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
639 for (int t = 0; t < node->get_num_threads(); t++) {
640 thread_id_t tother = int_to_id(t);
641 if (node->is_enabled(tother) && node->has_priority(tother)) {
649 /* Cache the latest backtracking point */
650 set_latest_backtrack(prev);
652 /* If this is a new backtracking point, mark the tree */
653 if (!node->set_backtrack(tid))
655 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
656 id_to_int(prev->get_tid()),
657 id_to_int(t->get_id()));
666 * @brief Cache the a backtracking point as the "most recent", if eligible
668 * Note that this does not prepare the NodeStack for this backtracking
669 * operation, it only caches the action on a per-execution basis
671 * @param act The operation at which we should explore a different next action
672 * (i.e., backtracking point)
673 * @return True, if this action is now the most recent backtracking point;
676 bool ModelChecker::set_latest_backtrack(ModelAction *act)
678 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
679 priv->next_backtrack = act;
686 * Returns last backtracking point. The model checker will explore a different
687 * path for this point in the next execution.
688 * @return The ModelAction at which the next execution should diverge.
690 ModelAction * ModelChecker::get_next_backtrack()
692 ModelAction *next = priv->next_backtrack;
693 priv->next_backtrack = NULL;
698 * Processes a read or rmw model action.
699 * @param curr is the read model action to process.
700 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
701 * @return True if processing this read updates the mo_graph.
703 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
705 uint64_t value = VALUE_NONE;
706 bool updated = false;
708 const ModelAction *reads_from = curr->get_node()->get_read_from();
709 if (reads_from != NULL) {
710 mo_graph->startChanges();
712 value = reads_from->get_value();
713 bool r_status = false;
715 if (!second_part_of_rmw) {
716 check_recency(curr, reads_from);
717 r_status = r_modification_order(curr, reads_from);
720 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
721 mo_graph->rollbackChanges();
722 priv->too_many_reads = false;
726 read_from(curr, reads_from);
727 mo_graph->commitChanges();
728 mo_check_promises(curr, true);
731 } else if (!second_part_of_rmw) {
732 /* Read from future value */
733 struct future_value fv = curr->get_node()->get_future_value();
734 Promise *promise = new Promise(curr, fv);
736 curr->set_read_from_promise(promise);
737 promises->push_back(promise);
738 mo_graph->startChanges();
739 updated = r_modification_order(curr, promise);
740 mo_graph->commitChanges();
742 get_thread(curr)->set_return_value(value);
748 * Processes a lock, trylock, or unlock model action. @param curr is
749 * the read model action to process.
751 * The try lock operation checks whether the lock is taken. If not,
752 * it falls to the normal lock operation case. If so, it returns
755 * The lock operation has already been checked that it is enabled, so
756 * it just grabs the lock and synchronizes with the previous unlock.
758 * The unlock operation has to re-enable all of the threads that are
759 * waiting on the lock.
761 * @return True if synchronization was updated; false otherwise
763 bool ModelChecker::process_mutex(ModelAction *curr)
765 std::mutex *mutex = NULL;
766 struct std::mutex_state *state = NULL;
768 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
769 mutex = (std::mutex *)curr->get_location();
770 state = mutex->get_state();
771 } else if (curr->is_wait()) {
772 mutex = (std::mutex *)curr->get_value();
773 state = mutex->get_state();
776 switch (curr->get_type()) {
777 case ATOMIC_TRYLOCK: {
778 bool success = !state->islocked;
779 curr->set_try_lock(success);
781 get_thread(curr)->set_return_value(0);
784 get_thread(curr)->set_return_value(1);
786 //otherwise fall into the lock case
788 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
789 assert_bug("Lock access before initialization");
790 state->islocked = true;
791 ModelAction *unlock = get_last_unlock(curr);
792 //synchronize with the previous unlock statement
793 if (unlock != NULL) {
794 curr->synchronize_with(unlock);
799 case ATOMIC_UNLOCK: {
801 state->islocked = false;
802 //wake up the other threads
803 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
804 //activate all the waiting threads
805 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
806 scheduler->wake(get_thread(*rit));
813 state->islocked = false;
814 //wake up the other threads
815 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
816 //activate all the waiting threads
817 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
818 scheduler->wake(get_thread(*rit));
821 //check whether we should go to sleep or not...simulate spurious failures
822 if (curr->get_node()->get_misc() == 0) {
823 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
825 scheduler->sleep(get_thread(curr));
829 case ATOMIC_NOTIFY_ALL: {
830 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
831 //activate all the waiting threads
832 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
833 scheduler->wake(get_thread(*rit));
838 case ATOMIC_NOTIFY_ONE: {
839 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
840 int wakeupthread = curr->get_node()->get_misc();
841 action_list_t::iterator it = waiters->begin();
842 advance(it, wakeupthread);
843 scheduler->wake(get_thread(*it));
854 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
856 /* Do more ambitious checks now that mo is more complete */
857 if (mo_may_allow(writer, reader)) {
858 Node *node = reader->get_node();
860 /* Find an ancestor thread which exists at the time of the reader */
861 Thread *write_thread = get_thread(writer);
862 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
863 write_thread = write_thread->get_parent();
865 struct future_value fv = {
867 writer->get_seq_number() + params.maxfuturedelay,
868 write_thread->get_id(),
870 if (node->add_future_value(fv))
871 set_latest_backtrack(reader);
876 * Process a write ModelAction
877 * @param curr The ModelAction to process
878 * @return True if the mo_graph was updated or promises were resolved
880 bool ModelChecker::process_write(ModelAction *curr)
882 bool updated_mod_order = w_modification_order(curr);
883 bool updated_promises = resolve_promises(curr);
885 if (promises->size() == 0) {
886 for (unsigned int i = 0; i < futurevalues->size(); i++) {
887 struct PendingFutureValue pfv = (*futurevalues)[i];
888 add_future_value(pfv.writer, pfv.act);
890 futurevalues->clear();
893 mo_graph->commitChanges();
894 mo_check_promises(curr, false);
896 get_thread(curr)->set_return_value(VALUE_NONE);
897 return updated_mod_order || updated_promises;
901 * Process a fence ModelAction
902 * @param curr The ModelAction to process
903 * @return True if synchronization was updated
905 bool ModelChecker::process_fence(ModelAction *curr)
908 * fence-relaxed: no-op
909 * fence-release: only log the occurence (not in this function), for
910 * use in later synchronization
911 * fence-acquire (this function): search for hypothetical release
914 bool updated = false;
915 if (curr->is_acquire()) {
916 action_list_t *list = action_trace;
917 action_list_t::reverse_iterator rit;
918 /* Find X : is_read(X) && X --sb-> curr */
919 for (rit = list->rbegin(); rit != list->rend(); rit++) {
920 ModelAction *act = *rit;
923 if (act->get_tid() != curr->get_tid())
925 /* Stop at the beginning of the thread */
926 if (act->is_thread_start())
928 /* Stop once we reach a prior fence-acquire */
929 if (act->is_fence() && act->is_acquire())
933 /* read-acquire will find its own release sequences */
934 if (act->is_acquire())
937 /* Establish hypothetical release sequences */
938 rel_heads_list_t release_heads;
939 get_release_seq_heads(curr, act, &release_heads);
940 for (unsigned int i = 0; i < release_heads.size(); i++)
941 if (!curr->synchronize_with(release_heads[i]))
942 set_bad_synchronization();
943 if (release_heads.size() != 0)
951 * @brief Process the current action for thread-related activity
953 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
954 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
955 * synchronization, etc. This function is a no-op for non-THREAD actions
956 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
958 * @param curr The current action
959 * @return True if synchronization was updated or a thread completed
961 bool ModelChecker::process_thread_action(ModelAction *curr)
963 bool updated = false;
965 switch (curr->get_type()) {
966 case THREAD_CREATE: {
967 thrd_t *thrd = (thrd_t *)curr->get_location();
968 struct thread_params *params = (struct thread_params *)curr->get_value();
969 Thread *th = new Thread(thrd, params->func, params->arg);
971 th->set_creation(curr);
972 /* Promises can be satisfied by children */
973 for (unsigned int i = 0; i < promises->size(); i++) {
974 Promise *promise = (*promises)[i];
975 if (promise->thread_is_available(curr->get_tid()))
976 promise->add_thread(th->get_id());
981 Thread *blocking = curr->get_thread_operand();
982 ModelAction *act = get_last_action(blocking->get_id());
983 curr->synchronize_with(act);
984 updated = true; /* trigger rel-seq checks */
987 case THREAD_FINISH: {
988 Thread *th = get_thread(curr);
989 while (!th->wait_list_empty()) {
990 ModelAction *act = th->pop_wait_list();
991 scheduler->wake(get_thread(act));
994 /* Completed thread can't satisfy promises */
995 for (unsigned int i = 0; i < promises->size(); i++) {
996 Promise *promise = (*promises)[i];
997 if (promise->thread_is_available(th->get_id()))
998 if (promise->eliminate_thread(th->get_id()))
999 priv->failed_promise = true;
1001 updated = true; /* trigger rel-seq checks */
1004 case THREAD_START: {
1005 check_promises(curr->get_tid(), NULL, curr->get_cv());
1016 * @brief Process the current action for release sequence fixup activity
1018 * Performs model-checker release sequence fixups for the current action,
1019 * forcing a single pending release sequence to break (with a given, potential
1020 * "loose" write) or to complete (i.e., synchronize). If a pending release
1021 * sequence forms a complete release sequence, then we must perform the fixup
1022 * synchronization, mo_graph additions, etc.
1024 * @param curr The current action; must be a release sequence fixup action
1025 * @param work_queue The work queue to which to add work items as they are
1028 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1030 const ModelAction *write = curr->get_node()->get_relseq_break();
1031 struct release_seq *sequence = pending_rel_seqs->back();
1032 pending_rel_seqs->pop_back();
1034 ModelAction *acquire = sequence->acquire;
1035 const ModelAction *rf = sequence->rf;
1036 const ModelAction *release = sequence->release;
1040 ASSERT(release->same_thread(rf));
1042 if (write == NULL) {
1044 * @todo Forcing a synchronization requires that we set
1045 * modification order constraints. For instance, we can't allow
1046 * a fixup sequence in which two separate read-acquire
1047 * operations read from the same sequence, where the first one
1048 * synchronizes and the other doesn't. Essentially, we can't
1049 * allow any writes to insert themselves between 'release' and
1053 /* Must synchronize */
1054 if (!acquire->synchronize_with(release)) {
1055 set_bad_synchronization();
1058 /* Re-check all pending release sequences */
1059 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1060 /* Re-check act for mo_graph edges */
1061 work_queue->push_back(MOEdgeWorkEntry(acquire));
1063 /* propagate synchronization to later actions */
1064 action_list_t::reverse_iterator rit = action_trace->rbegin();
1065 for (; (*rit) != acquire; rit++) {
1066 ModelAction *propagate = *rit;
1067 if (acquire->happens_before(propagate)) {
1068 propagate->synchronize_with(acquire);
1069 /* Re-check 'propagate' for mo_graph edges */
1070 work_queue->push_back(MOEdgeWorkEntry(propagate));
1074 /* Break release sequence with new edges:
1075 * release --mo--> write --mo--> rf */
1076 mo_graph->addEdge(release, write);
1077 mo_graph->addEdge(write, rf);
1080 /* See if we have realized a data race */
1085 * Initialize the current action by performing one or more of the following
1086 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1087 * in the NodeStack, manipulating backtracking sets, allocating and
1088 * initializing clock vectors, and computing the promises to fulfill.
1090 * @param curr The current action, as passed from the user context; may be
1091 * freed/invalidated after the execution of this function, with a different
1092 * action "returned" its place (pass-by-reference)
1093 * @return True if curr is a newly-explored action; false otherwise
1095 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1097 ModelAction *newcurr;
1099 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1100 newcurr = process_rmw(*curr);
1103 if (newcurr->is_rmw())
1104 compute_promises(newcurr);
1110 (*curr)->set_seq_number(get_next_seq_num());
1112 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1114 /* First restore type and order in case of RMW operation */
1115 if ((*curr)->is_rmwr())
1116 newcurr->copy_typeandorder(*curr);
1118 ASSERT((*curr)->get_location() == newcurr->get_location());
1119 newcurr->copy_from_new(*curr);
1121 /* Discard duplicate ModelAction; use action from NodeStack */
1124 /* Always compute new clock vector */
1125 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1128 return false; /* Action was explored previously */
1132 /* Always compute new clock vector */
1133 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1135 /* Assign most recent release fence */
1136 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1139 * Perform one-time actions when pushing new ModelAction onto
1142 if (newcurr->is_write())
1143 compute_promises(newcurr);
1144 else if (newcurr->is_relseq_fixup())
1145 compute_relseq_breakwrites(newcurr);
1146 else if (newcurr->is_wait())
1147 newcurr->get_node()->set_misc_max(2);
1148 else if (newcurr->is_notify_one()) {
1149 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1151 return true; /* This was a new ModelAction */
1156 * @brief Establish reads-from relation between two actions
1158 * Perform basic operations involved with establishing a concrete rf relation,
1159 * including setting the ModelAction data and checking for release sequences.
1161 * @param act The action that is reading (must be a read)
1162 * @param rf The action from which we are reading (must be a write)
1164 * @return True if this read established synchronization
1166 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1168 act->set_read_from(rf);
1169 if (rf != NULL && act->is_acquire()) {
1170 rel_heads_list_t release_heads;
1171 get_release_seq_heads(act, act, &release_heads);
1172 int num_heads = release_heads.size();
1173 for (unsigned int i = 0; i < release_heads.size(); i++)
1174 if (!act->synchronize_with(release_heads[i])) {
1175 set_bad_synchronization();
1178 return num_heads > 0;
1184 * @brief Check whether a model action is enabled.
1186 * Checks whether a lock or join operation would be successful (i.e., is the
1187 * lock already locked, or is the joined thread already complete). If not, put
1188 * the action in a waiter list.
1190 * @param curr is the ModelAction to check whether it is enabled.
1191 * @return a bool that indicates whether the action is enabled.
1193 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1194 if (curr->is_lock()) {
1195 std::mutex *lock = (std::mutex *)curr->get_location();
1196 struct std::mutex_state *state = lock->get_state();
1197 if (state->islocked) {
1198 //Stick the action in the appropriate waiting queue
1199 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1202 } else if (curr->get_type() == THREAD_JOIN) {
1203 Thread *blocking = (Thread *)curr->get_location();
1204 if (!blocking->is_complete()) {
1205 blocking->push_wait_list(curr);
1214 * This is the heart of the model checker routine. It performs model-checking
1215 * actions corresponding to a given "current action." Among other processes, it
1216 * calculates reads-from relationships, updates synchronization clock vectors,
1217 * forms a memory_order constraints graph, and handles replay/backtrack
1218 * execution when running permutations of previously-observed executions.
1220 * @param curr The current action to process
1221 * @return The ModelAction that is actually executed; may be different than
1222 * curr; may be NULL, if the current action is not enabled to run
1224 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1227 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1229 if (!check_action_enabled(curr)) {
1230 /* Make the execution look like we chose to run this action
1231 * much later, when a lock/join can succeed */
1232 get_thread(curr)->set_pending(curr);
1233 scheduler->sleep(get_thread(curr));
1237 bool newly_explored = initialize_curr_action(&curr);
1243 wake_up_sleeping_actions(curr);
1245 /* Add the action to lists before any other model-checking tasks */
1246 if (!second_part_of_rmw)
1247 add_action_to_lists(curr);
1249 /* Build may_read_from set for newly-created actions */
1250 if (newly_explored && curr->is_read())
1251 build_reads_from_past(curr);
1253 /* Initialize work_queue with the "current action" work */
1254 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1255 while (!work_queue.empty() && !has_asserted()) {
1256 WorkQueueEntry work = work_queue.front();
1257 work_queue.pop_front();
1259 switch (work.type) {
1260 case WORK_CHECK_CURR_ACTION: {
1261 ModelAction *act = work.action;
1262 bool update = false; /* update this location's release seq's */
1263 bool update_all = false; /* update all release seq's */
1265 if (process_thread_action(curr))
1268 if (act->is_read() && process_read(act, second_part_of_rmw))
1271 if (act->is_write() && process_write(act))
1274 if (act->is_fence() && process_fence(act))
1277 if (act->is_mutex_op() && process_mutex(act))
1280 if (act->is_relseq_fixup())
1281 process_relseq_fixup(curr, &work_queue);
1284 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1286 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1289 case WORK_CHECK_RELEASE_SEQ:
1290 resolve_release_sequences(work.location, &work_queue);
1292 case WORK_CHECK_MO_EDGES: {
1293 /** @todo Complete verification of work_queue */
1294 ModelAction *act = work.action;
1295 bool updated = false;
1297 if (act->is_read()) {
1298 const ModelAction *rf = act->get_reads_from();
1299 const Promise *promise = act->get_reads_from_promise();
1301 if (r_modification_order(act, rf))
1303 } else if (promise) {
1304 if (r_modification_order(act, promise))
1308 if (act->is_write()) {
1309 if (w_modification_order(act))
1312 mo_graph->commitChanges();
1315 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1324 check_curr_backtracking(curr);
1325 set_backtracking(curr);
1329 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1331 Node *currnode = curr->get_node();
1332 Node *parnode = currnode->get_parent();
1334 if ((parnode && !parnode->backtrack_empty()) ||
1335 !currnode->misc_empty() ||
1336 !currnode->read_from_empty() ||
1337 !currnode->future_value_empty() ||
1338 !currnode->promise_empty() ||
1339 !currnode->relseq_break_empty()) {
1340 set_latest_backtrack(curr);
1344 bool ModelChecker::promises_expired() const
1346 for (unsigned int i = 0; i < promises->size(); i++) {
1347 Promise *promise = (*promises)[i];
1348 if (promise->get_expiration() < priv->used_sequence_numbers)
1355 * This is the strongest feasibility check available.
1356 * @return whether the current trace (partial or complete) must be a prefix of
1359 bool ModelChecker::isfeasibleprefix() const
1361 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1365 * Print disagnostic information about an infeasible execution
1366 * @param prefix A string to prefix the output with; if NULL, then a default
1367 * message prefix will be provided
1369 void ModelChecker::print_infeasibility(const char *prefix) const
1373 if (mo_graph->checkForCycles())
1374 ptr += sprintf(ptr, "[mo cycle]");
1375 if (priv->failed_promise)
1376 ptr += sprintf(ptr, "[failed promise]");
1377 if (priv->too_many_reads)
1378 ptr += sprintf(ptr, "[too many reads]");
1379 if (priv->no_valid_reads)
1380 ptr += sprintf(ptr, "[no valid reads-from]");
1381 if (priv->bad_synchronization)
1382 ptr += sprintf(ptr, "[bad sw ordering]");
1383 if (promises_expired())
1384 ptr += sprintf(ptr, "[promise expired]");
1385 if (promises->size() != 0)
1386 ptr += sprintf(ptr, "[unresolved promise]");
1388 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1392 * Returns whether the current completed trace is feasible, except for pending
1393 * release sequences.
1395 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1397 return !is_infeasible() && promises->size() == 0;
1401 * Check if the current partial trace is infeasible. Does not check any
1402 * end-of-execution flags, which might rule out the execution. Thus, this is
1403 * useful only for ruling an execution as infeasible.
1404 * @return whether the current partial trace is infeasible.
1406 bool ModelChecker::is_infeasible() const
1408 return mo_graph->checkForCycles() ||
1409 priv->no_valid_reads ||
1410 priv->failed_promise ||
1411 priv->too_many_reads ||
1412 priv->bad_synchronization ||
1416 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1417 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1418 ModelAction *lastread = get_last_action(act->get_tid());
1419 lastread->process_rmw(act);
1420 if (act->is_rmw()) {
1421 if (lastread->get_reads_from())
1422 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1424 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1425 mo_graph->commitChanges();
1431 * Checks whether a thread has read from the same write for too many times
1432 * without seeing the effects of a later write.
1435 * 1) there must a different write that we could read from that would satisfy the modification order,
1436 * 2) we must have read from the same value in excess of maxreads times, and
1437 * 3) that other write must have been in the reads_from set for maxreads times.
1439 * If so, we decide that the execution is no longer feasible.
1441 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1443 if (params.maxreads != 0) {
1444 if (curr->get_node()->get_read_from_size() <= 1)
1446 //Must make sure that execution is currently feasible... We could
1447 //accidentally clear by rolling back
1448 if (is_infeasible())
1450 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1451 int tid = id_to_int(curr->get_tid());
1454 if ((int)thrd_lists->size() <= tid)
1456 action_list_t *list = &(*thrd_lists)[tid];
1458 action_list_t::reverse_iterator rit = list->rbegin();
1459 /* Skip past curr */
1460 for (; (*rit) != curr; rit++)
1462 /* go past curr now */
1465 action_list_t::reverse_iterator ritcopy = rit;
1466 //See if we have enough reads from the same value
1468 for (; count < params.maxreads; rit++, count++) {
1469 if (rit == list->rend())
1471 ModelAction *act = *rit;
1472 if (!act->is_read())
1475 if (act->get_reads_from() != rf)
1477 if (act->get_node()->get_read_from_size() <= 1)
1480 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1482 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1484 /* Need a different write */
1488 /* Test to see whether this is a feasible write to read from */
1489 /** NOTE: all members of read-from set should be
1490 * feasible, so we no longer check it here **/
1494 bool feasiblewrite = true;
1495 //new we need to see if this write works for everyone
1497 for (int loop = count; loop > 0; loop--, rit++) {
1498 ModelAction *act = *rit;
1499 bool foundvalue = false;
1500 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1501 if (act->get_node()->get_read_from_at(j) == write) {
1507 feasiblewrite = false;
1511 if (feasiblewrite) {
1512 priv->too_many_reads = true;
1520 * Updates the mo_graph with the constraints imposed from the current
1523 * Basic idea is the following: Go through each other thread and find
1524 * the last action that happened before our read. Two cases:
1526 * (1) The action is a write => that write must either occur before
1527 * the write we read from or be the write we read from.
1529 * (2) The action is a read => the write that that action read from
1530 * must occur before the write we read from or be the same write.
1532 * @param curr The current action. Must be a read.
1533 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1534 * @return True if modification order edges were added; false otherwise
1536 template <typename rf_type>
1537 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1539 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1542 ASSERT(curr->is_read());
1544 /* Last SC fence in the current thread */
1545 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1547 /* Iterate over all threads */
1548 for (i = 0; i < thrd_lists->size(); i++) {
1549 /* Last SC fence in thread i */
1550 ModelAction *last_sc_fence_thread_local = NULL;
1551 if (int_to_id((int)i) != curr->get_tid())
1552 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1554 /* Last SC fence in thread i, before last SC fence in current thread */
1555 ModelAction *last_sc_fence_thread_before = NULL;
1556 if (last_sc_fence_local)
1557 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1559 /* Iterate over actions in thread, starting from most recent */
1560 action_list_t *list = &(*thrd_lists)[i];
1561 action_list_t::reverse_iterator rit;
1562 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1563 ModelAction *act = *rit;
1565 if (act->is_write() && !act->equals(rf) && act != curr) {
1566 /* C++, Section 29.3 statement 5 */
1567 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1568 *act < *last_sc_fence_thread_local) {
1569 added = mo_graph->addEdge(act, rf) || added;
1572 /* C++, Section 29.3 statement 4 */
1573 else if (act->is_seqcst() && last_sc_fence_local &&
1574 *act < *last_sc_fence_local) {
1575 added = mo_graph->addEdge(act, rf) || added;
1578 /* C++, Section 29.3 statement 6 */
1579 else if (last_sc_fence_thread_before &&
1580 *act < *last_sc_fence_thread_before) {
1581 added = mo_graph->addEdge(act, rf) || added;
1587 * Include at most one act per-thread that "happens
1588 * before" curr. Don't consider reflexively.
1590 if (act->happens_before(curr) && act != curr) {
1591 if (act->is_write()) {
1592 if (!act->equals(rf)) {
1593 added = mo_graph->addEdge(act, rf) || added;
1596 const ModelAction *prevreadfrom = act->get_reads_from();
1597 //if the previous read is unresolved, keep going...
1598 if (prevreadfrom == NULL)
1601 if (!prevreadfrom->equals(rf)) {
1602 added = mo_graph->addEdge(prevreadfrom, rf) || added;
1611 * All compatible, thread-exclusive promises must be ordered after any
1612 * concrete loads from the same thread
1614 for (unsigned int i = 0; i < promises->size(); i++)
1615 if ((*promises)[i]->is_compatible_exclusive(curr))
1616 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1622 * Updates the mo_graph with the constraints imposed from the current write.
1624 * Basic idea is the following: Go through each other thread and find
1625 * the lastest action that happened before our write. Two cases:
1627 * (1) The action is a write => that write must occur before
1630 * (2) The action is a read => the write that that action read from
1631 * must occur before the current write.
1633 * This method also handles two other issues:
1635 * (I) Sequential Consistency: Making sure that if the current write is
1636 * seq_cst, that it occurs after the previous seq_cst write.
1638 * (II) Sending the write back to non-synchronizing reads.
1640 * @param curr The current action. Must be a write.
1641 * @return True if modification order edges were added; false otherwise
1643 bool ModelChecker::w_modification_order(ModelAction *curr)
1645 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1648 ASSERT(curr->is_write());
1650 if (curr->is_seqcst()) {
1651 /* We have to at least see the last sequentially consistent write,
1652 so we are initialized. */
1653 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1654 if (last_seq_cst != NULL) {
1655 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1659 /* Last SC fence in the current thread */
1660 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1662 /* Iterate over all threads */
1663 for (i = 0; i < thrd_lists->size(); i++) {
1664 /* Last SC fence in thread i, before last SC fence in current thread */
1665 ModelAction *last_sc_fence_thread_before = NULL;
1666 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1667 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1669 /* Iterate over actions in thread, starting from most recent */
1670 action_list_t *list = &(*thrd_lists)[i];
1671 action_list_t::reverse_iterator rit;
1672 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1673 ModelAction *act = *rit;
1676 * 1) If RMW and it actually read from something, then we
1677 * already have all relevant edges, so just skip to next
1680 * 2) If RMW and it didn't read from anything, we should
1681 * whatever edge we can get to speed up convergence.
1683 * 3) If normal write, we need to look at earlier actions, so
1684 * continue processing list.
1686 if (curr->is_rmw()) {
1687 if (curr->get_reads_from() != NULL)
1695 /* C++, Section 29.3 statement 7 */
1696 if (last_sc_fence_thread_before && act->is_write() &&
1697 *act < *last_sc_fence_thread_before) {
1698 added = mo_graph->addEdge(act, curr) || added;
1703 * Include at most one act per-thread that "happens
1706 if (act->happens_before(curr)) {
1708 * Note: if act is RMW, just add edge:
1710 * The following edge should be handled elsewhere:
1711 * readfrom(act) --mo--> act
1713 if (act->is_write())
1714 added = mo_graph->addEdge(act, curr) || added;
1715 else if (act->is_read()) {
1716 //if previous read accessed a null, just keep going
1717 if (act->get_reads_from() == NULL)
1719 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1722 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1723 !act->same_thread(curr)) {
1724 /* We have an action that:
1725 (1) did not happen before us
1726 (2) is a read and we are a write
1727 (3) cannot synchronize with us
1728 (4) is in a different thread
1730 that read could potentially read from our write. Note that
1731 these checks are overly conservative at this point, we'll
1732 do more checks before actually removing the
1736 if (thin_air_constraint_may_allow(curr, act)) {
1737 if (!is_infeasible())
1738 futurevalues->push_back(PendingFutureValue(curr, act));
1739 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1740 add_future_value(curr, act);
1747 * All compatible, thread-exclusive promises must be ordered after any
1748 * concrete stores to the same thread, or else they can be merged with
1751 for (unsigned int i = 0; i < promises->size(); i++)
1752 if ((*promises)[i]->is_compatible_exclusive(curr))
1753 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1758 /** Arbitrary reads from the future are not allowed. Section 29.3
1759 * part 9 places some constraints. This method checks one result of constraint
1760 * constraint. Others require compiler support. */
1761 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1763 if (!writer->is_rmw())
1766 if (!reader->is_rmw())
1769 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1770 if (search == reader)
1772 if (search->get_tid() == reader->get_tid() &&
1773 search->happens_before(reader))
1781 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1782 * some constraints. This method checks one the following constraint (others
1783 * require compiler support):
1785 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1787 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1789 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1791 /* Iterate over all threads */
1792 for (i = 0; i < thrd_lists->size(); i++) {
1793 const ModelAction *write_after_read = NULL;
1795 /* Iterate over actions in thread, starting from most recent */
1796 action_list_t *list = &(*thrd_lists)[i];
1797 action_list_t::reverse_iterator rit;
1798 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1799 ModelAction *act = *rit;
1801 /* Don't disallow due to act == reader */
1802 if (!reader->happens_before(act) || reader == act)
1804 else if (act->is_write())
1805 write_after_read = act;
1806 else if (act->is_read() && act->get_reads_from() != NULL)
1807 write_after_read = act->get_reads_from();
1810 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1817 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1818 * The ModelAction under consideration is expected to be taking part in
1819 * release/acquire synchronization as an object of the "reads from" relation.
1820 * Note that this can only provide release sequence support for RMW chains
1821 * which do not read from the future, as those actions cannot be traced until
1822 * their "promise" is fulfilled. Similarly, we may not even establish the
1823 * presence of a release sequence with certainty, as some modification order
1824 * constraints may be decided further in the future. Thus, this function
1825 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1826 * and a boolean representing certainty.
1828 * @param rf The action that might be part of a release sequence. Must be a
1830 * @param release_heads A pass-by-reference style return parameter. After
1831 * execution of this function, release_heads will contain the heads of all the
1832 * relevant release sequences, if any exists with certainty
1833 * @param pending A pass-by-reference style return parameter which is only used
1834 * when returning false (i.e., uncertain). Returns most information regarding
1835 * an uncertain release sequence, including any write operations that might
1836 * break the sequence.
1837 * @return true, if the ModelChecker is certain that release_heads is complete;
1840 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1841 rel_heads_list_t *release_heads,
1842 struct release_seq *pending) const
1844 /* Only check for release sequences if there are no cycles */
1845 if (mo_graph->checkForCycles())
1849 ASSERT(rf->is_write());
1851 if (rf->is_release())
1852 release_heads->push_back(rf);
1853 else if (rf->get_last_fence_release())
1854 release_heads->push_back(rf->get_last_fence_release());
1856 break; /* End of RMW chain */
1858 /** @todo Need to be smarter here... In the linux lock
1859 * example, this will run to the beginning of the program for
1861 /** @todo The way to be smarter here is to keep going until 1
1862 * thread has a release preceded by an acquire and you've seen
1865 /* acq_rel RMW is a sufficient stopping condition */
1866 if (rf->is_acquire() && rf->is_release())
1867 return true; /* complete */
1869 rf = rf->get_reads_from();
1872 /* read from future: need to settle this later */
1874 return false; /* incomplete */
1877 if (rf->is_release())
1878 return true; /* complete */
1880 /* else relaxed write
1881 * - check for fence-release in the same thread (29.8, stmt. 3)
1882 * - check modification order for contiguous subsequence
1883 * -> rf must be same thread as release */
1885 const ModelAction *fence_release = rf->get_last_fence_release();
1886 /* Synchronize with a fence-release unconditionally; we don't need to
1887 * find any more "contiguous subsequence..." for it */
1889 release_heads->push_back(fence_release);
1891 int tid = id_to_int(rf->get_tid());
1892 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1893 action_list_t *list = &(*thrd_lists)[tid];
1894 action_list_t::const_reverse_iterator rit;
1896 /* Find rf in the thread list */
1897 rit = std::find(list->rbegin(), list->rend(), rf);
1898 ASSERT(rit != list->rend());
1900 /* Find the last {write,fence}-release */
1901 for (; rit != list->rend(); rit++) {
1902 if (fence_release && *(*rit) < *fence_release)
1904 if ((*rit)->is_release())
1907 if (rit == list->rend()) {
1908 /* No write-release in this thread */
1909 return true; /* complete */
1910 } else if (fence_release && *(*rit) < *fence_release) {
1911 /* The fence-release is more recent (and so, "stronger") than
1912 * the most recent write-release */
1913 return true; /* complete */
1914 } /* else, need to establish contiguous release sequence */
1915 ModelAction *release = *rit;
1917 ASSERT(rf->same_thread(release));
1919 pending->writes.clear();
1921 bool certain = true;
1922 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1923 if (id_to_int(rf->get_tid()) == (int)i)
1925 list = &(*thrd_lists)[i];
1927 /* Can we ensure no future writes from this thread may break
1928 * the release seq? */
1929 bool future_ordered = false;
1931 ModelAction *last = get_last_action(int_to_id(i));
1932 Thread *th = get_thread(int_to_id(i));
1933 if ((last && rf->happens_before(last)) ||
1936 future_ordered = true;
1938 ASSERT(!th->is_model_thread() || future_ordered);
1940 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1941 const ModelAction *act = *rit;
1942 /* Reach synchronization -> this thread is complete */
1943 if (act->happens_before(release))
1945 if (rf->happens_before(act)) {
1946 future_ordered = true;
1950 /* Only non-RMW writes can break release sequences */
1951 if (!act->is_write() || act->is_rmw())
1954 /* Check modification order */
1955 if (mo_graph->checkReachable(rf, act)) {
1956 /* rf --mo--> act */
1957 future_ordered = true;
1960 if (mo_graph->checkReachable(act, release))
1961 /* act --mo--> release */
1963 if (mo_graph->checkReachable(release, act) &&
1964 mo_graph->checkReachable(act, rf)) {
1965 /* release --mo-> act --mo--> rf */
1966 return true; /* complete */
1968 /* act may break release sequence */
1969 pending->writes.push_back(act);
1972 if (!future_ordered)
1973 certain = false; /* This thread is uncertain */
1977 release_heads->push_back(release);
1978 pending->writes.clear();
1980 pending->release = release;
1987 * An interface for getting the release sequence head(s) with which a
1988 * given ModelAction must synchronize. This function only returns a non-empty
1989 * result when it can locate a release sequence head with certainty. Otherwise,
1990 * it may mark the internal state of the ModelChecker so that it will handle
1991 * the release sequence at a later time, causing @a acquire to update its
1992 * synchronization at some later point in execution.
1994 * @param acquire The 'acquire' action that may synchronize with a release
1996 * @param read The read action that may read from a release sequence; this may
1997 * be the same as acquire, or else an earlier action in the same thread (i.e.,
1998 * when 'acquire' is a fence-acquire)
1999 * @param release_heads A pass-by-reference return parameter. Will be filled
2000 * with the head(s) of the release sequence(s), if they exists with certainty.
2001 * @see ModelChecker::release_seq_heads
2003 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2004 ModelAction *read, rel_heads_list_t *release_heads)
2006 const ModelAction *rf = read->get_reads_from();
2007 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2008 sequence->acquire = acquire;
2009 sequence->read = read;
2011 if (!release_seq_heads(rf, release_heads, sequence)) {
2012 /* add act to 'lazy checking' list */
2013 pending_rel_seqs->push_back(sequence);
2015 snapshot_free(sequence);
2020 * Attempt to resolve all stashed operations that might synchronize with a
2021 * release sequence for a given location. This implements the "lazy" portion of
2022 * determining whether or not a release sequence was contiguous, since not all
2023 * modification order information is present at the time an action occurs.
2025 * @param location The location/object that should be checked for release
2026 * sequence resolutions. A NULL value means to check all locations.
2027 * @param work_queue The work queue to which to add work items as they are
2029 * @return True if any updates occurred (new synchronization, new mo_graph
2032 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2034 bool updated = false;
2035 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2036 while (it != pending_rel_seqs->end()) {
2037 struct release_seq *pending = *it;
2038 ModelAction *acquire = pending->acquire;
2039 const ModelAction *read = pending->read;
2041 /* Only resolve sequences on the given location, if provided */
2042 if (location && read->get_location() != location) {
2047 const ModelAction *rf = read->get_reads_from();
2048 rel_heads_list_t release_heads;
2050 complete = release_seq_heads(rf, &release_heads, pending);
2051 for (unsigned int i = 0; i < release_heads.size(); i++) {
2052 if (!acquire->has_synchronized_with(release_heads[i])) {
2053 if (acquire->synchronize_with(release_heads[i]))
2056 set_bad_synchronization();
2061 /* Re-check all pending release sequences */
2062 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2063 /* Re-check read-acquire for mo_graph edges */
2064 if (acquire->is_read())
2065 work_queue->push_back(MOEdgeWorkEntry(acquire));
2067 /* propagate synchronization to later actions */
2068 action_list_t::reverse_iterator rit = action_trace->rbegin();
2069 for (; (*rit) != acquire; rit++) {
2070 ModelAction *propagate = *rit;
2071 if (acquire->happens_before(propagate)) {
2072 propagate->synchronize_with(acquire);
2073 /* Re-check 'propagate' for mo_graph edges */
2074 work_queue->push_back(MOEdgeWorkEntry(propagate));
2079 it = pending_rel_seqs->erase(it);
2080 snapshot_free(pending);
2086 // If we resolved promises or data races, see if we have realized a data race.
2093 * Performs various bookkeeping operations for the current ModelAction. For
2094 * instance, adds action to the per-object, per-thread action vector and to the
2095 * action trace list of all thread actions.
2097 * @param act is the ModelAction to add.
2099 void ModelChecker::add_action_to_lists(ModelAction *act)
2101 int tid = id_to_int(act->get_tid());
2102 ModelAction *uninit = NULL;
2104 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2105 if (list->empty() && act->is_atomic_var()) {
2106 uninit = new_uninitialized_action(act->get_location());
2107 uninit_id = id_to_int(uninit->get_tid());
2108 list->push_back(uninit);
2110 list->push_back(act);
2112 action_trace->push_back(act);
2114 action_trace->push_front(uninit);
2116 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2117 if (tid >= (int)vec->size())
2118 vec->resize(priv->next_thread_id);
2119 (*vec)[tid].push_back(act);
2121 (*vec)[uninit_id].push_front(uninit);
2123 if ((int)thrd_last_action->size() <= tid)
2124 thrd_last_action->resize(get_num_threads());
2125 (*thrd_last_action)[tid] = act;
2127 (*thrd_last_action)[uninit_id] = uninit;
2129 if (act->is_fence() && act->is_release()) {
2130 if ((int)thrd_last_fence_release->size() <= tid)
2131 thrd_last_fence_release->resize(get_num_threads());
2132 (*thrd_last_fence_release)[tid] = act;
2135 if (act->is_wait()) {
2136 void *mutex_loc = (void *) act->get_value();
2137 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2139 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2140 if (tid >= (int)vec->size())
2141 vec->resize(priv->next_thread_id);
2142 (*vec)[tid].push_back(act);
2147 * @brief Get the last action performed by a particular Thread
2148 * @param tid The thread ID of the Thread in question
2149 * @return The last action in the thread
2151 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2153 int threadid = id_to_int(tid);
2154 if (threadid < (int)thrd_last_action->size())
2155 return (*thrd_last_action)[id_to_int(tid)];
2161 * @brief Get the last fence release performed by a particular Thread
2162 * @param tid The thread ID of the Thread in question
2163 * @return The last fence release in the thread, if one exists; NULL otherwise
2165 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2167 int threadid = id_to_int(tid);
2168 if (threadid < (int)thrd_last_fence_release->size())
2169 return (*thrd_last_fence_release)[id_to_int(tid)];
2175 * Gets the last memory_order_seq_cst write (in the total global sequence)
2176 * performed on a particular object (i.e., memory location), not including the
2178 * @param curr The current ModelAction; also denotes the object location to
2180 * @return The last seq_cst write
2182 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2184 void *location = curr->get_location();
2185 action_list_t *list = get_safe_ptr_action(obj_map, location);
2186 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2187 action_list_t::reverse_iterator rit;
2188 for (rit = list->rbegin(); rit != list->rend(); rit++)
2189 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2195 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2196 * performed in a particular thread, prior to a particular fence.
2197 * @param tid The ID of the thread to check
2198 * @param before_fence The fence from which to begin the search; if NULL, then
2199 * search for the most recent fence in the thread.
2200 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2202 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2204 /* All fences should have NULL location */
2205 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2206 action_list_t::reverse_iterator rit = list->rbegin();
2209 for (; rit != list->rend(); rit++)
2210 if (*rit == before_fence)
2213 ASSERT(*rit == before_fence);
2217 for (; rit != list->rend(); rit++)
2218 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2224 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2225 * location). This function identifies the mutex according to the current
2226 * action, which is presumed to perform on the same mutex.
2227 * @param curr The current ModelAction; also denotes the object location to
2229 * @return The last unlock operation
2231 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2233 void *location = curr->get_location();
2234 action_list_t *list = get_safe_ptr_action(obj_map, location);
2235 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2236 action_list_t::reverse_iterator rit;
2237 for (rit = list->rbegin(); rit != list->rend(); rit++)
2238 if ((*rit)->is_unlock() || (*rit)->is_wait())
2243 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2245 ModelAction *parent = get_last_action(tid);
2247 parent = get_thread(tid)->get_creation();
2252 * Returns the clock vector for a given thread.
2253 * @param tid The thread whose clock vector we want
2254 * @return Desired clock vector
2256 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2258 return get_parent_action(tid)->get_cv();
2262 * Resolve a set of Promises with a current write. The set is provided in the
2263 * Node corresponding to @a write.
2264 * @param write The ModelAction that is fulfilling Promises
2265 * @return True if promises were resolved; false otherwise
2267 bool ModelChecker::resolve_promises(ModelAction *write)
2269 bool haveResolved = false;
2270 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2271 promise_list_t mustResolve, resolved;
2273 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2274 Promise *promise = (*promises)[promise_index];
2275 if (write->get_node()->get_promise(i)) {
2276 ModelAction *read = promise->get_action();
2277 read_from(read, write);
2278 //Make sure the promise's value matches the write's value
2279 ASSERT(promise->is_compatible(write));
2280 mo_graph->resolvePromise(read, write, &mustResolve);
2282 resolved.push_back(promise);
2283 promises->erase(promises->begin() + promise_index);
2284 actions_to_check.push_back(read);
2286 haveResolved = true;
2291 for (unsigned int i = 0; i < mustResolve.size(); i++) {
2292 if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
2294 priv->failed_promise = true;
2296 for (unsigned int i = 0; i < resolved.size(); i++)
2298 //Check whether reading these writes has made threads unable to
2301 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2302 ModelAction *read = actions_to_check[i];
2303 mo_check_promises(read, true);
2306 return haveResolved;
2310 * Compute the set of promises that could potentially be satisfied by this
2311 * action. Note that the set computation actually appears in the Node, not in
2313 * @param curr The ModelAction that may satisfy promises
2315 void ModelChecker::compute_promises(ModelAction *curr)
2317 for (unsigned int i = 0; i < promises->size(); i++) {
2318 Promise *promise = (*promises)[i];
2319 const ModelAction *act = promise->get_action();
2320 if (!act->happens_before(curr) &&
2322 !act->could_synchronize_with(curr) &&
2323 !act->same_thread(curr) &&
2324 act->get_location() == curr->get_location() &&
2325 promise->get_value() == curr->get_value()) {
2326 curr->get_node()->set_promise(i, act->is_rmw());
2331 /** Checks promises in response to change in ClockVector Threads. */
2332 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2334 for (unsigned int i = 0; i < promises->size(); i++) {
2335 Promise *promise = (*promises)[i];
2336 const ModelAction *act = promise->get_action();
2337 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2338 merge_cv->synchronized_since(act)) {
2339 if (promise->eliminate_thread(tid)) {
2340 //Promise has failed
2341 priv->failed_promise = true;
2348 void ModelChecker::check_promises_thread_disabled()
2350 for (unsigned int i = 0; i < promises->size(); i++) {
2351 Promise *promise = (*promises)[i];
2352 if (promise->has_failed()) {
2353 priv->failed_promise = true;
2360 * @brief Checks promises in response to addition to modification order for
2363 * We test whether threads are still available for satisfying promises after an
2364 * addition to our modification order constraints. Those that are unavailable
2365 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2366 * that promise has failed.
2368 * @param act The ModelAction which updated the modification order
2369 * @param is_read_check Should be true if act is a read and we must check for
2370 * updates to the store from which it read (there is a distinction here for
2371 * RMW's, which are both a load and a store)
2373 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2375 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2377 for (unsigned int i = 0; i < promises->size(); i++) {
2378 Promise *promise = (*promises)[i];
2379 const ModelAction *pread = promise->get_action();
2381 // Is this promise on the same location?
2382 if (!pread->same_var(write))
2385 if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
2386 priv->failed_promise = true;
2390 // Don't do any lookups twice for the same thread
2391 if (!promise->thread_is_available(act->get_tid()))
2394 if (mo_graph->checkReachable(promise, write)) {
2395 if (mo_graph->checkPromise(write, promise)) {
2396 priv->failed_promise = true;
2404 * Compute the set of writes that may break the current pending release
2405 * sequence. This information is extracted from previou release sequence
2408 * @param curr The current ModelAction. Must be a release sequence fixup
2411 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2413 if (pending_rel_seqs->empty())
2416 struct release_seq *pending = pending_rel_seqs->back();
2417 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2418 const ModelAction *write = pending->writes[i];
2419 curr->get_node()->add_relseq_break(write);
2422 /* NULL means don't break the sequence; just synchronize */
2423 curr->get_node()->add_relseq_break(NULL);
2427 * Build up an initial set of all past writes that this 'read' action may read
2428 * from. This set is determined by the clock vector's "happens before"
2430 * @param curr is the current ModelAction that we are exploring; it must be a
2433 void ModelChecker::build_reads_from_past(ModelAction *curr)
2435 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2437 ASSERT(curr->is_read());
2439 ModelAction *last_sc_write = NULL;
2441 if (curr->is_seqcst())
2442 last_sc_write = get_last_seq_cst_write(curr);
2444 /* Iterate over all threads */
2445 for (i = 0; i < thrd_lists->size(); i++) {
2446 /* Iterate over actions in thread, starting from most recent */
2447 action_list_t *list = &(*thrd_lists)[i];
2448 action_list_t::reverse_iterator rit;
2449 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2450 ModelAction *act = *rit;
2452 /* Only consider 'write' actions */
2453 if (!act->is_write() || act == curr)
2456 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2457 bool allow_read = true;
2459 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2461 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2465 /* Only add feasible reads */
2466 mo_graph->startChanges();
2467 r_modification_order(curr, act);
2468 if (!is_infeasible())
2469 curr->get_node()->add_read_from(act);
2470 mo_graph->rollbackChanges();
2473 /* Include at most one act per-thread that "happens before" curr */
2474 if (act->happens_before(curr))
2478 /* We may find no valid may-read-from only if the execution is doomed */
2479 if (!curr->get_node()->get_read_from_size()) {
2480 priv->no_valid_reads = true;
2484 if (DBG_ENABLED()) {
2485 model_print("Reached read action:\n");
2487 model_print("Printing may_read_from\n");
2488 curr->get_node()->print_may_read_from();
2489 model_print("End printing may_read_from\n");
2493 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2496 /* UNINIT actions don't have a Node, and they never sleep */
2497 if (write->is_uninitialized())
2499 Node *prevnode = write->get_node()->get_parent();
2501 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2502 if (write->is_release() && thread_sleep)
2504 if (!write->is_rmw()) {
2507 if (write->get_reads_from() == NULL)
2509 write = write->get_reads_from();
2514 * @brief Create a new action representing an uninitialized atomic
2515 * @param location The memory location of the atomic object
2516 * @return A pointer to a new ModelAction
2518 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2520 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2521 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2522 act->create_cv(NULL);
2526 static void print_list(action_list_t *list)
2528 action_list_t::iterator it;
2530 model_print("---------------------------------------------------------------------\n");
2532 unsigned int hash = 0;
2534 for (it = list->begin(); it != list->end(); it++) {
2536 hash = hash^(hash<<3)^((*it)->hash());
2538 model_print("HASH %u\n", hash);
2539 model_print("---------------------------------------------------------------------\n");
2542 #if SUPPORT_MOD_ORDER_DUMP
2543 void ModelChecker::dumpGraph(char *filename) const
2546 sprintf(buffer, "%s.dot", filename);
2547 FILE *file = fopen(buffer, "w");
2548 fprintf(file, "digraph %s {\n", filename);
2549 mo_graph->dumpNodes(file);
2550 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2552 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2553 ModelAction *action = *it;
2554 if (action->is_read()) {
2555 fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2556 if (action->get_reads_from() != NULL)
2557 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2559 if (thread_array[action->get_tid()] != NULL) {
2560 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2563 thread_array[action->get_tid()] = action;
2565 fprintf(file, "}\n");
2566 model_free(thread_array);
2571 /** @brief Prints an execution trace summary. */
2572 void ModelChecker::print_summary() const
2574 #if SUPPORT_MOD_ORDER_DUMP
2575 char buffername[100];
2576 sprintf(buffername, "exec%04u", stats.num_total);
2577 mo_graph->dumpGraphToFile(buffername);
2578 sprintf(buffername, "graph%04u", stats.num_total);
2579 dumpGraph(buffername);
2582 model_print("Execution %d:", stats.num_total);
2583 if (isfeasibleprefix())
2586 print_infeasibility(" INFEASIBLE");
2587 print_list(action_trace);
2592 * Add a Thread to the system for the first time. Should only be called once
2594 * @param t The Thread to add
2596 void ModelChecker::add_thread(Thread *t)
2598 thread_map->put(id_to_int(t->get_id()), t);
2599 scheduler->add_thread(t);
2603 * Removes a thread from the scheduler.
2604 * @param the thread to remove.
2606 void ModelChecker::remove_thread(Thread *t)
2608 scheduler->remove_thread(t);
2612 * @brief Get a Thread reference by its ID
2613 * @param tid The Thread's ID
2614 * @return A Thread reference
2616 Thread * ModelChecker::get_thread(thread_id_t tid) const
2618 return thread_map->get(id_to_int(tid));
2622 * @brief Get a reference to the Thread in which a ModelAction was executed
2623 * @param act The ModelAction
2624 * @return A Thread reference
2626 Thread * ModelChecker::get_thread(const ModelAction *act) const
2628 return get_thread(act->get_tid());
2632 * @brief Check if a Thread is currently enabled
2633 * @param t The Thread to check
2634 * @return True if the Thread is currently enabled
2636 bool ModelChecker::is_enabled(Thread *t) const
2638 return scheduler->is_enabled(t);
2642 * @brief Check if a Thread is currently enabled
2643 * @param tid The ID of the Thread to check
2644 * @return True if the Thread is currently enabled
2646 bool ModelChecker::is_enabled(thread_id_t tid) const
2648 return scheduler->is_enabled(tid);
2652 * Switch from a user-context to the "master thread" context (a.k.a. system
2653 * context). This switch is made with the intention of exploring a particular
2654 * model-checking action (described by a ModelAction object). Must be called
2655 * from a user-thread context.
2657 * @param act The current action that will be explored. May be NULL only if
2658 * trace is exiting via an assertion (see ModelChecker::set_assert and
2659 * ModelChecker::has_asserted).
2660 * @return Return the value returned by the current action
2662 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2665 Thread *old = thread_current();
2666 ASSERT(!old->get_pending());
2667 old->set_pending(act);
2668 if (Thread::swap(old, &system_context) < 0) {
2669 perror("swap threads");
2672 return old->get_return_value();
2676 * Takes the next step in the execution, if possible.
2677 * @param curr The current step to take
2678 * @return Returns the next Thread to run, if any; NULL if this execution
2681 Thread * ModelChecker::take_step(ModelAction *curr)
2683 Thread *curr_thrd = get_thread(curr);
2684 ASSERT(curr_thrd->get_state() == THREAD_READY);
2686 curr = check_current_action(curr);
2688 /* Infeasible -> don't take any more steps */
2689 if (is_infeasible())
2691 else if (isfeasibleprefix() && have_bug_reports()) {
2696 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2699 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2700 scheduler->remove_thread(curr_thrd);
2702 Thread *next_thrd = get_next_thread(curr);
2703 next_thrd = scheduler->next_thread(next_thrd);
2705 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2706 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2709 * Launch end-of-execution release sequence fixups only when there are:
2711 * (1) no more user threads to run (or when execution replay chooses
2712 * the 'model_thread')
2713 * (2) pending release sequences
2714 * (3) pending assertions (i.e., data races)
2715 * (4) no pending promises
2717 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2718 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2719 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2720 pending_rel_seqs->size());
2721 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2722 std::memory_order_seq_cst, NULL, VALUE_NONE,
2724 model_thread->set_pending(fixup);
2725 return model_thread;
2728 /* next_thrd == NULL -> don't take any more steps */
2735 /** Wrapper to run the user's main function, with appropriate arguments */
2736 void user_main_wrapper(void *)
2738 user_main(model->params.argc, model->params.argv);
2741 /** @brief Run ModelChecker for the user program */
2742 void ModelChecker::run()
2746 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2750 for (unsigned int i = 0; i < get_num_threads(); i++) {
2751 thread_id_t tid = int_to_id(i);
2752 Thread *thr = get_thread(tid);
2753 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
2754 scheduler->next_thread(thr);
2755 Thread::swap(&system_context, thr);
2759 /* Catch assertions from prior take_step or from
2760 * between-ModelAction bugs (e.g., data races) */
2764 /* Consume the next action for a Thread */
2765 ModelAction *curr = t->get_pending();
2766 t->set_pending(NULL);
2767 t = take_step(curr);
2768 } while (t && !t->is_model_thread());
2769 /** @TODO Re-write release sequence fixups here */
2770 } while (next_execution());