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 no_valid_reads(false),
52 bad_synchronization(false),
56 ~model_snapshot_members() {
57 for (unsigned int i = 0; i < bugs.size(); i++)
62 ModelAction *current_action;
63 unsigned int next_thread_id;
64 modelclock_t used_sequence_numbers;
65 ModelAction *next_backtrack;
66 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
67 struct execution_stats stats;
71 /** @brief Incorrectly-ordered synchronization was made */
72 bool bad_synchronization;
78 /** @brief Constructor */
79 ModelChecker::ModelChecker(struct model_params params) :
80 /* Initialize default scheduler */
82 scheduler(new Scheduler()),
84 earliest_diverge(NULL),
85 action_trace(new action_list_t()),
86 thread_map(new HashTable<int, Thread *, int>()),
87 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
89 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
90 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
91 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
92 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
93 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
94 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
95 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
96 node_stack(new NodeStack()),
97 priv(new struct model_snapshot_members()),
98 mo_graph(new CycleGraph())
100 /* Initialize a model-checker thread, for special ModelActions */
101 model_thread = new Thread(get_next_id());
102 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
105 /** @brief Destructor */
106 ModelChecker::~ModelChecker()
108 for (unsigned int i = 0; i < get_num_threads(); i++)
109 delete thread_map->get(i);
114 delete lock_waiters_map;
115 delete condvar_waiters_map;
118 for (unsigned int i = 0; i < promises->size(); i++)
119 delete (*promises)[i];
122 delete pending_rel_seqs;
124 delete thrd_last_action;
125 delete thrd_last_fence_release;
132 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
134 action_list_t *tmp = hash->get(ptr);
136 tmp = new action_list_t();
142 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
144 std::vector<action_list_t> *tmp = hash->get(ptr);
146 tmp = new std::vector<action_list_t>();
153 * Restores user program to initial state and resets all model-checker data
156 void ModelChecker::reset_to_initial_state()
158 DEBUG("+++ Resetting to initial state +++\n");
159 node_stack->reset_execution();
161 /* Print all model-checker output before rollback */
164 snapshot_backtrack_before(0);
167 /** @return a thread ID for a new Thread */
168 thread_id_t ModelChecker::get_next_id()
170 return priv->next_thread_id++;
173 /** @return the number of user threads created during this execution */
174 unsigned int ModelChecker::get_num_threads() const
176 return priv->next_thread_id;
180 * Must be called from user-thread context (e.g., through the global
181 * thread_current() interface)
183 * @return The currently executing Thread.
185 Thread * ModelChecker::get_current_thread() const
187 return scheduler->get_current_thread();
190 /** @return a sequence number for a new ModelAction */
191 modelclock_t ModelChecker::get_next_seq_num()
193 return ++priv->used_sequence_numbers;
196 Node * ModelChecker::get_curr_node() const
198 return node_stack->get_head();
202 * @brief Choose the next thread to execute.
204 * This function chooses the next thread that should execute. It can force the
205 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
206 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
207 * The model-checker may have no preference regarding the next thread (i.e.,
208 * when exploring a new execution ordering), in which case this will return
210 * @param curr The current ModelAction. This action might guide the choice of
212 * @return The next thread to run. If the model-checker has no preference, NULL.
214 Thread * ModelChecker::get_next_thread(ModelAction *curr)
219 /* Do not split atomic actions. */
221 return thread_current();
222 else if (curr->get_type() == THREAD_CREATE)
223 return curr->get_thread_operand();
226 /* Have we completed exploring the preselected path? */
230 /* Else, we are trying to replay an execution */
231 ModelAction *next = node_stack->get_next()->get_action();
233 if (next == diverge) {
234 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
235 earliest_diverge = diverge;
237 Node *nextnode = next->get_node();
238 Node *prevnode = nextnode->get_parent();
239 scheduler->update_sleep_set(prevnode);
241 /* Reached divergence point */
242 if (nextnode->increment_misc()) {
243 /* The next node will try to satisfy a different misc_index values. */
244 tid = next->get_tid();
245 node_stack->pop_restofstack(2);
246 } else if (nextnode->increment_promise()) {
247 /* The next node will try to satisfy a different set of promises. */
248 tid = next->get_tid();
249 node_stack->pop_restofstack(2);
250 } else if (nextnode->increment_read_from()) {
251 /* The next node will read from a different value. */
252 tid = next->get_tid();
253 node_stack->pop_restofstack(2);
254 } else if (nextnode->increment_future_value()) {
255 /* The next node will try to read from a different future value. */
256 tid = next->get_tid();
257 node_stack->pop_restofstack(2);
258 } else if (nextnode->increment_relseq_break()) {
259 /* The next node will try to resolve a release sequence differently */
260 tid = next->get_tid();
261 node_stack->pop_restofstack(2);
264 /* Make a different thread execute for next step */
265 scheduler->add_sleep(get_thread(next->get_tid()));
266 tid = prevnode->get_next_backtrack();
267 /* Make sure the backtracked thread isn't sleeping. */
268 node_stack->pop_restofstack(1);
269 if (diverge == earliest_diverge) {
270 earliest_diverge = prevnode->get_action();
273 /* The correct sleep set is in the parent node. */
276 DEBUG("*** Divergence point ***\n");
280 tid = next->get_tid();
282 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
283 ASSERT(tid != THREAD_ID_T_NONE);
284 return thread_map->get(id_to_int(tid));
288 * We need to know what the next actions of all threads in the sleep
289 * set will be. This method computes them and stores the actions at
290 * the corresponding thread object's pending action.
293 void ModelChecker::execute_sleep_set()
295 for (unsigned int i = 0; i < get_num_threads(); i++) {
296 thread_id_t tid = int_to_id(i);
297 Thread *thr = get_thread(tid);
298 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
299 scheduler->next_thread(thr);
300 Thread::swap(&system_context, thr);
301 priv->current_action->set_sleep_flag();
302 thr->set_pending(priv->current_action);
307 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
309 for (unsigned int i = 0; i < get_num_threads(); i++) {
310 Thread *thr = get_thread(int_to_id(i));
311 if (scheduler->is_sleep_set(thr)) {
312 ModelAction *pending_act = thr->get_pending();
313 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
314 //Remove this thread from sleep set
315 scheduler->remove_sleep(thr);
320 /** @brief Alert the model-checker that an incorrectly-ordered
321 * synchronization was made */
322 void ModelChecker::set_bad_synchronization()
324 priv->bad_synchronization = true;
327 bool ModelChecker::has_asserted() const
329 return priv->asserted;
332 void ModelChecker::set_assert()
334 priv->asserted = true;
338 * Check if we are in a deadlock. Should only be called at the end of an
339 * execution, although it should not give false positives in the middle of an
340 * execution (there should be some ENABLED thread).
342 * @return True if program is in a deadlock; false otherwise
344 bool ModelChecker::is_deadlocked() const
346 bool blocking_threads = false;
347 for (unsigned int i = 0; i < get_num_threads(); i++) {
348 thread_id_t tid = int_to_id(i);
351 Thread *t = get_thread(tid);
352 if (!t->is_model_thread() && t->get_pending())
353 blocking_threads = true;
355 return blocking_threads;
359 * Check if this is a complete execution. That is, have all thread completed
360 * execution (rather than exiting because sleep sets have forced a redundant
363 * @return True if the execution is complete.
365 bool ModelChecker::is_complete_execution() const
367 for (unsigned int i = 0; i < get_num_threads(); i++)
368 if (is_enabled(int_to_id(i)))
374 * @brief Assert a bug in the executing program.
376 * Use this function to assert any sort of bug in the user program. If the
377 * current trace is feasible (actually, a prefix of some feasible execution),
378 * then this execution will be aborted, printing the appropriate message. If
379 * the current trace is not yet feasible, the error message will be stashed and
380 * printed if the execution ever becomes feasible.
382 * @param msg Descriptive message for the bug (do not include newline char)
383 * @return True if bug is immediately-feasible
385 bool ModelChecker::assert_bug(const char *msg)
387 priv->bugs.push_back(new bug_message(msg));
389 if (isfeasibleprefix()) {
397 * @brief Assert a bug in the executing program, asserted by a user thread
398 * @see ModelChecker::assert_bug
399 * @param msg Descriptive message for the bug (do not include newline char)
401 void ModelChecker::assert_user_bug(const char *msg)
403 /* If feasible bug, bail out now */
405 switch_to_master(NULL);
408 /** @return True, if any bugs have been reported for this execution */
409 bool ModelChecker::have_bug_reports() const
411 return priv->bugs.size() != 0;
414 /** @brief Print bug report listing for this execution (if any bugs exist) */
415 void ModelChecker::print_bugs() const
417 if (have_bug_reports()) {
418 model_print("Bug report: %zu bug%s detected\n",
420 priv->bugs.size() > 1 ? "s" : "");
421 for (unsigned int i = 0; i < priv->bugs.size(); i++)
422 priv->bugs[i]->print();
427 * @brief Record end-of-execution stats
429 * Must be run when exiting an execution. Records various stats.
430 * @see struct execution_stats
432 void ModelChecker::record_stats()
435 if (!isfeasibleprefix())
436 stats.num_infeasible++;
437 else if (have_bug_reports())
438 stats.num_buggy_executions++;
439 else if (is_complete_execution())
440 stats.num_complete++;
442 stats.num_redundant++;
445 /** @brief Print execution stats */
446 void ModelChecker::print_stats() const
448 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
449 model_print("Number of redundant executions: %d\n", stats.num_redundant);
450 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
451 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
452 model_print("Total executions: %d\n", stats.num_total);
453 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
457 * @brief End-of-exeuction print
458 * @param printbugs Should any existing bugs be printed?
460 void ModelChecker::print_execution(bool printbugs) const
462 print_program_output();
464 if (DBG_ENABLED() || params.verbose) {
465 model_print("Earliest divergence point since last feasible execution:\n");
466 if (earliest_diverge)
467 earliest_diverge->print();
469 model_print("(Not set)\n");
475 /* Don't print invalid bugs */
484 * Queries the model-checker for more executions to explore and, if one
485 * exists, resets the model-checker state to execute a new execution.
487 * @return If there are more executions to explore, return true. Otherwise,
490 bool ModelChecker::next_execution()
493 /* Is this execution a feasible execution that's worth bug-checking? */
494 bool complete = isfeasibleprefix() && (is_complete_execution() ||
497 /* End-of-execution bug checks */
500 assert_bug("Deadlock detected");
508 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
509 print_execution(complete);
511 clear_program_output();
514 earliest_diverge = NULL;
516 if ((diverge = get_next_backtrack()) == NULL)
520 model_print("Next execution will diverge at:\n");
524 reset_to_initial_state();
528 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
530 switch (act->get_type()) {
535 /* Optimization: relaxed operations don't need backtracking */
536 if (act->is_relaxed())
538 /* linear search: from most recent to oldest */
539 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
540 action_list_t::reverse_iterator rit;
541 for (rit = list->rbegin(); rit != list->rend(); rit++) {
542 ModelAction *prev = *rit;
543 if (prev->could_synchronize_with(act))
549 case ATOMIC_TRYLOCK: {
550 /* linear search: from most recent to oldest */
551 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
552 action_list_t::reverse_iterator rit;
553 for (rit = list->rbegin(); rit != list->rend(); rit++) {
554 ModelAction *prev = *rit;
555 if (act->is_conflicting_lock(prev))
560 case ATOMIC_UNLOCK: {
561 /* linear search: from most recent to oldest */
562 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
563 action_list_t::reverse_iterator rit;
564 for (rit = list->rbegin(); rit != list->rend(); rit++) {
565 ModelAction *prev = *rit;
566 if (!act->same_thread(prev) && prev->is_failed_trylock())
572 /* linear search: from most recent to oldest */
573 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
574 action_list_t::reverse_iterator rit;
575 for (rit = list->rbegin(); rit != list->rend(); rit++) {
576 ModelAction *prev = *rit;
577 if (!act->same_thread(prev) && prev->is_failed_trylock())
579 if (!act->same_thread(prev) && prev->is_notify())
585 case ATOMIC_NOTIFY_ALL:
586 case ATOMIC_NOTIFY_ONE: {
587 /* linear search: from most recent to oldest */
588 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
589 action_list_t::reverse_iterator rit;
590 for (rit = list->rbegin(); rit != list->rend(); rit++) {
591 ModelAction *prev = *rit;
592 if (!act->same_thread(prev) && prev->is_wait())
603 /** This method finds backtracking points where we should try to
604 * reorder the parameter ModelAction against.
606 * @param the ModelAction to find backtracking points for.
608 void ModelChecker::set_backtracking(ModelAction *act)
610 Thread *t = get_thread(act);
611 ModelAction *prev = get_last_conflict(act);
615 Node *node = prev->get_node()->get_parent();
617 int low_tid, high_tid;
618 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
619 low_tid = id_to_int(act->get_tid());
620 high_tid = low_tid + 1;
623 high_tid = get_num_threads();
626 for (int i = low_tid; i < high_tid; i++) {
627 thread_id_t tid = int_to_id(i);
629 /* Make sure this thread can be enabled here. */
630 if (i >= node->get_num_threads())
633 /* Don't backtrack into a point where the thread is disabled or sleeping. */
634 if (node->enabled_status(tid) != THREAD_ENABLED)
637 /* Check if this has been explored already */
638 if (node->has_been_explored(tid))
641 /* See if fairness allows */
642 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
644 for (int t = 0; t < node->get_num_threads(); t++) {
645 thread_id_t tother = int_to_id(t);
646 if (node->is_enabled(tother) && node->has_priority(tother)) {
654 /* Cache the latest backtracking point */
655 set_latest_backtrack(prev);
657 /* If this is a new backtracking point, mark the tree */
658 if (!node->set_backtrack(tid))
660 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
661 id_to_int(prev->get_tid()),
662 id_to_int(t->get_id()));
671 * @brief Cache the a backtracking point as the "most recent", if eligible
673 * Note that this does not prepare the NodeStack for this backtracking
674 * operation, it only caches the action on a per-execution basis
676 * @param act The operation at which we should explore a different next action
677 * (i.e., backtracking point)
678 * @return True, if this action is now the most recent backtracking point;
681 bool ModelChecker::set_latest_backtrack(ModelAction *act)
683 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
684 priv->next_backtrack = act;
691 * Returns last backtracking point. The model checker will explore a different
692 * path for this point in the next execution.
693 * @return The ModelAction at which the next execution should diverge.
695 ModelAction * ModelChecker::get_next_backtrack()
697 ModelAction *next = priv->next_backtrack;
698 priv->next_backtrack = NULL;
703 * Processes a read or rmw model action.
704 * @param curr is the read model action to process.
705 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
706 * @return True if processing this read updates the mo_graph.
708 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
710 uint64_t value = VALUE_NONE;
711 bool updated = false;
713 const ModelAction *reads_from = curr->get_node()->get_read_from();
714 if (reads_from != NULL) {
715 mo_graph->startChanges();
717 value = reads_from->get_value();
718 bool r_status = false;
720 if (!second_part_of_rmw) {
721 check_recency(curr, reads_from);
722 r_status = r_modification_order(curr, reads_from);
725 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
726 mo_graph->rollbackChanges();
727 priv->too_many_reads = false;
731 read_from(curr, reads_from);
732 mo_graph->commitChanges();
733 mo_check_promises(curr, true);
736 } else if (!second_part_of_rmw) {
737 /* Read from future value */
738 struct future_value fv = curr->get_node()->get_future_value();
739 Promise *promise = new Promise(curr, fv);
741 curr->set_read_from_promise(promise);
742 promises->push_back(promise);
743 mo_graph->startChanges();
744 updated = r_modification_order(curr, promise);
745 mo_graph->commitChanges();
747 get_thread(curr)->set_return_value(value);
753 * Processes a lock, trylock, or unlock model action. @param curr is
754 * the read model action to process.
756 * The try lock operation checks whether the lock is taken. If not,
757 * it falls to the normal lock operation case. If so, it returns
760 * The lock operation has already been checked that it is enabled, so
761 * it just grabs the lock and synchronizes with the previous unlock.
763 * The unlock operation has to re-enable all of the threads that are
764 * waiting on the lock.
766 * @return True if synchronization was updated; false otherwise
768 bool ModelChecker::process_mutex(ModelAction *curr)
770 std::mutex *mutex = NULL;
771 struct std::mutex_state *state = NULL;
773 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
774 mutex = (std::mutex *)curr->get_location();
775 state = mutex->get_state();
776 } else if (curr->is_wait()) {
777 mutex = (std::mutex *)curr->get_value();
778 state = mutex->get_state();
781 switch (curr->get_type()) {
782 case ATOMIC_TRYLOCK: {
783 bool success = !state->islocked;
784 curr->set_try_lock(success);
786 get_thread(curr)->set_return_value(0);
789 get_thread(curr)->set_return_value(1);
791 //otherwise fall into the lock case
793 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
794 assert_bug("Lock access before initialization");
795 state->islocked = true;
796 ModelAction *unlock = get_last_unlock(curr);
797 //synchronize with the previous unlock statement
798 if (unlock != NULL) {
799 curr->synchronize_with(unlock);
804 case ATOMIC_UNLOCK: {
806 state->islocked = false;
807 //wake up the other threads
808 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
809 //activate all the waiting threads
810 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
811 scheduler->wake(get_thread(*rit));
818 state->islocked = false;
819 //wake up the other threads
820 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
821 //activate all the waiting threads
822 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
823 scheduler->wake(get_thread(*rit));
826 //check whether we should go to sleep or not...simulate spurious failures
827 if (curr->get_node()->get_misc() == 0) {
828 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
830 scheduler->sleep(get_thread(curr));
834 case ATOMIC_NOTIFY_ALL: {
835 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
836 //activate all the waiting threads
837 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
838 scheduler->wake(get_thread(*rit));
843 case ATOMIC_NOTIFY_ONE: {
844 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
845 int wakeupthread = curr->get_node()->get_misc();
846 action_list_t::iterator it = waiters->begin();
847 advance(it, wakeupthread);
848 scheduler->wake(get_thread(*it));
859 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
861 /* Do more ambitious checks now that mo is more complete */
862 if (mo_may_allow(writer, reader)) {
863 Node *node = reader->get_node();
865 /* Find an ancestor thread which exists at the time of the reader */
866 Thread *write_thread = get_thread(writer);
867 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
868 write_thread = write_thread->get_parent();
870 struct future_value fv = {
872 writer->get_seq_number() + params.maxfuturedelay,
873 write_thread->get_id(),
875 if (node->add_future_value(fv))
876 set_latest_backtrack(reader);
881 * Process a write ModelAction
882 * @param curr The ModelAction to process
883 * @return True if the mo_graph was updated or promises were resolved
885 bool ModelChecker::process_write(ModelAction *curr)
887 bool updated_mod_order = w_modification_order(curr);
888 bool updated_promises = resolve_promises(curr);
890 if (promises->size() == 0) {
891 for (unsigned int i = 0; i < futurevalues->size(); i++) {
892 struct PendingFutureValue pfv = (*futurevalues)[i];
893 add_future_value(pfv.writer, pfv.act);
895 futurevalues->clear();
898 mo_graph->commitChanges();
899 mo_check_promises(curr, false);
901 get_thread(curr)->set_return_value(VALUE_NONE);
902 return updated_mod_order || updated_promises;
906 * Process a fence ModelAction
907 * @param curr The ModelAction to process
908 * @return True if synchronization was updated
910 bool ModelChecker::process_fence(ModelAction *curr)
913 * fence-relaxed: no-op
914 * fence-release: only log the occurence (not in this function), for
915 * use in later synchronization
916 * fence-acquire (this function): search for hypothetical release
919 bool updated = false;
920 if (curr->is_acquire()) {
921 action_list_t *list = action_trace;
922 action_list_t::reverse_iterator rit;
923 /* Find X : is_read(X) && X --sb-> curr */
924 for (rit = list->rbegin(); rit != list->rend(); rit++) {
925 ModelAction *act = *rit;
928 if (act->get_tid() != curr->get_tid())
930 /* Stop at the beginning of the thread */
931 if (act->is_thread_start())
933 /* Stop once we reach a prior fence-acquire */
934 if (act->is_fence() && act->is_acquire())
938 /* read-acquire will find its own release sequences */
939 if (act->is_acquire())
942 /* Establish hypothetical release sequences */
943 rel_heads_list_t release_heads;
944 get_release_seq_heads(curr, act, &release_heads);
945 for (unsigned int i = 0; i < release_heads.size(); i++)
946 if (!curr->synchronize_with(release_heads[i]))
947 set_bad_synchronization();
948 if (release_heads.size() != 0)
956 * @brief Process the current action for thread-related activity
958 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
959 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
960 * synchronization, etc. This function is a no-op for non-THREAD actions
961 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
963 * @param curr The current action
964 * @return True if synchronization was updated or a thread completed
966 bool ModelChecker::process_thread_action(ModelAction *curr)
968 bool updated = false;
970 switch (curr->get_type()) {
971 case THREAD_CREATE: {
972 Thread *th = curr->get_thread_operand();
973 th->set_creation(curr);
974 /* Promises can be satisfied by children */
975 for (unsigned int i = 0; i < promises->size(); i++) {
976 Promise *promise = (*promises)[i];
977 if (promise->thread_is_available(curr->get_tid()))
978 promise->add_thread(th->get_id());
983 Thread *blocking = curr->get_thread_operand();
984 ModelAction *act = get_last_action(blocking->get_id());
985 curr->synchronize_with(act);
986 updated = true; /* trigger rel-seq checks */
989 case THREAD_FINISH: {
990 Thread *th = get_thread(curr);
991 while (!th->wait_list_empty()) {
992 ModelAction *act = th->pop_wait_list();
993 scheduler->wake(get_thread(act));
996 /* Completed thread can't satisfy promises */
997 for (unsigned int i = 0; i < promises->size(); i++) {
998 Promise *promise = (*promises)[i];
999 if (promise->thread_is_available(th->get_id()))
1000 if (promise->eliminate_thread(th->get_id()))
1001 priv->failed_promise = true;
1003 updated = true; /* trigger rel-seq checks */
1006 case THREAD_START: {
1007 check_promises(curr->get_tid(), NULL, curr->get_cv());
1018 * @brief Process the current action for release sequence fixup activity
1020 * Performs model-checker release sequence fixups for the current action,
1021 * forcing a single pending release sequence to break (with a given, potential
1022 * "loose" write) or to complete (i.e., synchronize). If a pending release
1023 * sequence forms a complete release sequence, then we must perform the fixup
1024 * synchronization, mo_graph additions, etc.
1026 * @param curr The current action; must be a release sequence fixup action
1027 * @param work_queue The work queue to which to add work items as they are
1030 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1032 const ModelAction *write = curr->get_node()->get_relseq_break();
1033 struct release_seq *sequence = pending_rel_seqs->back();
1034 pending_rel_seqs->pop_back();
1036 ModelAction *acquire = sequence->acquire;
1037 const ModelAction *rf = sequence->rf;
1038 const ModelAction *release = sequence->release;
1042 ASSERT(release->same_thread(rf));
1044 if (write == NULL) {
1046 * @todo Forcing a synchronization requires that we set
1047 * modification order constraints. For instance, we can't allow
1048 * a fixup sequence in which two separate read-acquire
1049 * operations read from the same sequence, where the first one
1050 * synchronizes and the other doesn't. Essentially, we can't
1051 * allow any writes to insert themselves between 'release' and
1055 /* Must synchronize */
1056 if (!acquire->synchronize_with(release)) {
1057 set_bad_synchronization();
1060 /* Re-check all pending release sequences */
1061 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1062 /* Re-check act for mo_graph edges */
1063 work_queue->push_back(MOEdgeWorkEntry(acquire));
1065 /* propagate synchronization to later actions */
1066 action_list_t::reverse_iterator rit = action_trace->rbegin();
1067 for (; (*rit) != acquire; rit++) {
1068 ModelAction *propagate = *rit;
1069 if (acquire->happens_before(propagate)) {
1070 propagate->synchronize_with(acquire);
1071 /* Re-check 'propagate' for mo_graph edges */
1072 work_queue->push_back(MOEdgeWorkEntry(propagate));
1076 /* Break release sequence with new edges:
1077 * release --mo--> write --mo--> rf */
1078 mo_graph->addEdge(release, write);
1079 mo_graph->addEdge(write, rf);
1082 /* See if we have realized a data race */
1087 * Initialize the current action by performing one or more of the following
1088 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1089 * in the NodeStack, manipulating backtracking sets, allocating and
1090 * initializing clock vectors, and computing the promises to fulfill.
1092 * @param curr The current action, as passed from the user context; may be
1093 * freed/invalidated after the execution of this function, with a different
1094 * action "returned" its place (pass-by-reference)
1095 * @return True if curr is a newly-explored action; false otherwise
1097 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1099 ModelAction *newcurr;
1101 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1102 newcurr = process_rmw(*curr);
1105 if (newcurr->is_rmw())
1106 compute_promises(newcurr);
1112 (*curr)->set_seq_number(get_next_seq_num());
1114 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1116 /* First restore type and order in case of RMW operation */
1117 if ((*curr)->is_rmwr())
1118 newcurr->copy_typeandorder(*curr);
1120 ASSERT((*curr)->get_location() == newcurr->get_location());
1121 newcurr->copy_from_new(*curr);
1123 /* Discard duplicate ModelAction; use action from NodeStack */
1126 /* Always compute new clock vector */
1127 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1130 return false; /* Action was explored previously */
1134 /* Always compute new clock vector */
1135 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1137 /* Assign most recent release fence */
1138 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1141 * Perform one-time actions when pushing new ModelAction onto
1144 if (newcurr->is_write())
1145 compute_promises(newcurr);
1146 else if (newcurr->is_relseq_fixup())
1147 compute_relseq_breakwrites(newcurr);
1148 else if (newcurr->is_wait())
1149 newcurr->get_node()->set_misc_max(2);
1150 else if (newcurr->is_notify_one()) {
1151 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1153 return true; /* This was a new ModelAction */
1158 * @brief Establish reads-from relation between two actions
1160 * Perform basic operations involved with establishing a concrete rf relation,
1161 * including setting the ModelAction data and checking for release sequences.
1163 * @param act The action that is reading (must be a read)
1164 * @param rf The action from which we are reading (must be a write)
1166 * @return True if this read established synchronization
1168 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1170 act->set_read_from(rf);
1171 if (rf != NULL && act->is_acquire()) {
1172 rel_heads_list_t release_heads;
1173 get_release_seq_heads(act, act, &release_heads);
1174 int num_heads = release_heads.size();
1175 for (unsigned int i = 0; i < release_heads.size(); i++)
1176 if (!act->synchronize_with(release_heads[i])) {
1177 set_bad_synchronization();
1180 return num_heads > 0;
1186 * @brief Check whether a model action is enabled.
1188 * Checks whether a lock or join operation would be successful (i.e., is the
1189 * lock already locked, or is the joined thread already complete). If not, put
1190 * the action in a waiter list.
1192 * @param curr is the ModelAction to check whether it is enabled.
1193 * @return a bool that indicates whether the action is enabled.
1195 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1196 if (curr->is_lock()) {
1197 std::mutex *lock = (std::mutex *)curr->get_location();
1198 struct std::mutex_state *state = lock->get_state();
1199 if (state->islocked) {
1200 //Stick the action in the appropriate waiting queue
1201 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1204 } else if (curr->get_type() == THREAD_JOIN) {
1205 Thread *blocking = (Thread *)curr->get_location();
1206 if (!blocking->is_complete()) {
1207 blocking->push_wait_list(curr);
1216 * Stores the ModelAction for the current thread action. Call this
1217 * immediately before switching from user- to system-context to pass
1218 * data between them.
1219 * @param act The ModelAction created by the user-thread action
1221 void ModelChecker::set_current_action(ModelAction *act) {
1222 priv->current_action = act;
1226 * This is the heart of the model checker routine. It performs model-checking
1227 * actions corresponding to a given "current action." Among other processes, it
1228 * calculates reads-from relationships, updates synchronization clock vectors,
1229 * forms a memory_order constraints graph, and handles replay/backtrack
1230 * execution when running permutations of previously-observed executions.
1232 * @param curr The current action to process
1233 * @return The ModelAction that is actually executed; may be different than
1234 * curr; may be NULL, if the current action is not enabled to run
1236 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1239 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1241 if (!check_action_enabled(curr)) {
1242 /* Make the execution look like we chose to run this action
1243 * much later, when a lock/join can succeed */
1244 get_thread(curr)->set_pending(curr);
1245 scheduler->sleep(get_thread(curr));
1249 bool newly_explored = initialize_curr_action(&curr);
1255 wake_up_sleeping_actions(curr);
1257 /* Add the action to lists before any other model-checking tasks */
1258 if (!second_part_of_rmw)
1259 add_action_to_lists(curr);
1261 /* Build may_read_from set for newly-created actions */
1262 if (newly_explored && curr->is_read())
1263 build_reads_from_past(curr);
1265 /* Initialize work_queue with the "current action" work */
1266 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1267 while (!work_queue.empty() && !has_asserted()) {
1268 WorkQueueEntry work = work_queue.front();
1269 work_queue.pop_front();
1271 switch (work.type) {
1272 case WORK_CHECK_CURR_ACTION: {
1273 ModelAction *act = work.action;
1274 bool update = false; /* update this location's release seq's */
1275 bool update_all = false; /* update all release seq's */
1277 if (process_thread_action(curr))
1280 if (act->is_read() && process_read(act, second_part_of_rmw))
1283 if (act->is_write() && process_write(act))
1286 if (act->is_fence() && process_fence(act))
1289 if (act->is_mutex_op() && process_mutex(act))
1292 if (act->is_relseq_fixup())
1293 process_relseq_fixup(curr, &work_queue);
1296 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1298 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1301 case WORK_CHECK_RELEASE_SEQ:
1302 resolve_release_sequences(work.location, &work_queue);
1304 case WORK_CHECK_MO_EDGES: {
1305 /** @todo Complete verification of work_queue */
1306 ModelAction *act = work.action;
1307 bool updated = false;
1309 if (act->is_read()) {
1310 const ModelAction *rf = act->get_reads_from();
1311 const Promise *promise = act->get_reads_from_promise();
1313 if (r_modification_order(act, rf))
1315 } else if (promise) {
1316 if (r_modification_order(act, promise))
1320 if (act->is_write()) {
1321 if (w_modification_order(act))
1324 mo_graph->commitChanges();
1327 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1336 check_curr_backtracking(curr);
1337 set_backtracking(curr);
1341 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1343 Node *currnode = curr->get_node();
1344 Node *parnode = currnode->get_parent();
1346 if ((parnode && !parnode->backtrack_empty()) ||
1347 !currnode->misc_empty() ||
1348 !currnode->read_from_empty() ||
1349 !currnode->future_value_empty() ||
1350 !currnode->promise_empty() ||
1351 !currnode->relseq_break_empty()) {
1352 set_latest_backtrack(curr);
1356 bool ModelChecker::promises_expired() const
1358 for (unsigned int i = 0; i < promises->size(); i++) {
1359 Promise *promise = (*promises)[i];
1360 if (promise->get_expiration() < priv->used_sequence_numbers)
1367 * This is the strongest feasibility check available.
1368 * @return whether the current trace (partial or complete) must be a prefix of
1371 bool ModelChecker::isfeasibleprefix() const
1373 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1377 * Print disagnostic information about an infeasible execution
1378 * @param prefix A string to prefix the output with; if NULL, then a default
1379 * message prefix will be provided
1381 void ModelChecker::print_infeasibility(const char *prefix) const
1385 if (mo_graph->checkForCycles())
1386 ptr += sprintf(ptr, "[mo cycle]");
1387 if (priv->failed_promise)
1388 ptr += sprintf(ptr, "[failed promise]");
1389 if (priv->too_many_reads)
1390 ptr += sprintf(ptr, "[too many reads]");
1391 if (priv->no_valid_reads)
1392 ptr += sprintf(ptr, "[no valid reads-from]");
1393 if (priv->bad_synchronization)
1394 ptr += sprintf(ptr, "[bad sw ordering]");
1395 if (promises_expired())
1396 ptr += sprintf(ptr, "[promise expired]");
1397 if (promises->size() != 0)
1398 ptr += sprintf(ptr, "[unresolved promise]");
1400 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1404 * Returns whether the current completed trace is feasible, except for pending
1405 * release sequences.
1407 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1409 return !is_infeasible() && promises->size() == 0;
1413 * Check if the current partial trace is infeasible. Does not check any
1414 * end-of-execution flags, which might rule out the execution. Thus, this is
1415 * useful only for ruling an execution as infeasible.
1416 * @return whether the current partial trace is infeasible.
1418 bool ModelChecker::is_infeasible() const
1420 return mo_graph->checkForCycles() ||
1421 priv->no_valid_reads ||
1422 priv->failed_promise ||
1423 priv->too_many_reads ||
1424 priv->bad_synchronization ||
1428 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1429 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1430 ModelAction *lastread = get_last_action(act->get_tid());
1431 lastread->process_rmw(act);
1432 if (act->is_rmw()) {
1433 if (lastread->get_reads_from())
1434 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1436 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1437 mo_graph->commitChanges();
1443 * Checks whether a thread has read from the same write for too many times
1444 * without seeing the effects of a later write.
1447 * 1) there must a different write that we could read from that would satisfy the modification order,
1448 * 2) we must have read from the same value in excess of maxreads times, and
1449 * 3) that other write must have been in the reads_from set for maxreads times.
1451 * If so, we decide that the execution is no longer feasible.
1453 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1455 if (params.maxreads != 0) {
1456 if (curr->get_node()->get_read_from_size() <= 1)
1458 //Must make sure that execution is currently feasible... We could
1459 //accidentally clear by rolling back
1460 if (is_infeasible())
1462 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1463 int tid = id_to_int(curr->get_tid());
1466 if ((int)thrd_lists->size() <= tid)
1468 action_list_t *list = &(*thrd_lists)[tid];
1470 action_list_t::reverse_iterator rit = list->rbegin();
1471 /* Skip past curr */
1472 for (; (*rit) != curr; rit++)
1474 /* go past curr now */
1477 action_list_t::reverse_iterator ritcopy = rit;
1478 //See if we have enough reads from the same value
1480 for (; count < params.maxreads; rit++, count++) {
1481 if (rit == list->rend())
1483 ModelAction *act = *rit;
1484 if (!act->is_read())
1487 if (act->get_reads_from() != rf)
1489 if (act->get_node()->get_read_from_size() <= 1)
1492 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1494 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1496 /* Need a different write */
1500 /* Test to see whether this is a feasible write to read from */
1501 /** NOTE: all members of read-from set should be
1502 * feasible, so we no longer check it here **/
1506 bool feasiblewrite = true;
1507 //new we need to see if this write works for everyone
1509 for (int loop = count; loop > 0; loop--, rit++) {
1510 ModelAction *act = *rit;
1511 bool foundvalue = false;
1512 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1513 if (act->get_node()->get_read_from_at(j) == write) {
1519 feasiblewrite = false;
1523 if (feasiblewrite) {
1524 priv->too_many_reads = true;
1532 * Updates the mo_graph with the constraints imposed from the current
1535 * Basic idea is the following: Go through each other thread and find
1536 * the last action that happened before our read. Two cases:
1538 * (1) The action is a write => that write must either occur before
1539 * the write we read from or be the write we read from.
1541 * (2) The action is a read => the write that that action read from
1542 * must occur before the write we read from or be the same write.
1544 * @param curr The current action. Must be a read.
1545 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1546 * @return True if modification order edges were added; false otherwise
1548 template <typename rf_type>
1549 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1551 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1554 ASSERT(curr->is_read());
1556 /* Last SC fence in the current thread */
1557 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1559 /* Iterate over all threads */
1560 for (i = 0; i < thrd_lists->size(); i++) {
1561 /* Last SC fence in thread i */
1562 ModelAction *last_sc_fence_thread_local = NULL;
1563 if (int_to_id((int)i) != curr->get_tid())
1564 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1566 /* Last SC fence in thread i, before last SC fence in current thread */
1567 ModelAction *last_sc_fence_thread_before = NULL;
1568 if (last_sc_fence_local)
1569 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1571 /* Iterate over actions in thread, starting from most recent */
1572 action_list_t *list = &(*thrd_lists)[i];
1573 action_list_t::reverse_iterator rit;
1574 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1575 ModelAction *act = *rit;
1577 if (act->is_write() && !act->equals(rf) && act != curr) {
1578 /* C++, Section 29.3 statement 5 */
1579 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1580 *act < *last_sc_fence_thread_local) {
1581 added = mo_graph->addEdge(act, rf) || added;
1584 /* C++, Section 29.3 statement 4 */
1585 else if (act->is_seqcst() && last_sc_fence_local &&
1586 *act < *last_sc_fence_local) {
1587 added = mo_graph->addEdge(act, rf) || added;
1590 /* C++, Section 29.3 statement 6 */
1591 else if (last_sc_fence_thread_before &&
1592 *act < *last_sc_fence_thread_before) {
1593 added = mo_graph->addEdge(act, rf) || added;
1599 * Include at most one act per-thread that "happens
1600 * before" curr. Don't consider reflexively.
1602 if (act->happens_before(curr) && act != curr) {
1603 if (act->is_write()) {
1604 if (!act->equals(rf)) {
1605 added = mo_graph->addEdge(act, rf) || added;
1608 const ModelAction *prevreadfrom = act->get_reads_from();
1609 //if the previous read is unresolved, keep going...
1610 if (prevreadfrom == NULL)
1613 if (!prevreadfrom->equals(rf)) {
1614 added = mo_graph->addEdge(prevreadfrom, rf) || added;
1623 * All compatible, thread-exclusive promises must be ordered after any
1624 * concrete loads from the same thread
1626 for (unsigned int i = 0; i < promises->size(); i++)
1627 if ((*promises)[i]->is_compatible_exclusive(curr))
1628 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1634 * Updates the mo_graph with the constraints imposed from the current write.
1636 * Basic idea is the following: Go through each other thread and find
1637 * the lastest action that happened before our write. Two cases:
1639 * (1) The action is a write => that write must occur before
1642 * (2) The action is a read => the write that that action read from
1643 * must occur before the current write.
1645 * This method also handles two other issues:
1647 * (I) Sequential Consistency: Making sure that if the current write is
1648 * seq_cst, that it occurs after the previous seq_cst write.
1650 * (II) Sending the write back to non-synchronizing reads.
1652 * @param curr The current action. Must be a write.
1653 * @return True if modification order edges were added; false otherwise
1655 bool ModelChecker::w_modification_order(ModelAction *curr)
1657 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1660 ASSERT(curr->is_write());
1662 if (curr->is_seqcst()) {
1663 /* We have to at least see the last sequentially consistent write,
1664 so we are initialized. */
1665 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1666 if (last_seq_cst != NULL) {
1667 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1671 /* Last SC fence in the current thread */
1672 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1674 /* Iterate over all threads */
1675 for (i = 0; i < thrd_lists->size(); i++) {
1676 /* Last SC fence in thread i, before last SC fence in current thread */
1677 ModelAction *last_sc_fence_thread_before = NULL;
1678 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1679 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1681 /* Iterate over actions in thread, starting from most recent */
1682 action_list_t *list = &(*thrd_lists)[i];
1683 action_list_t::reverse_iterator rit;
1684 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1685 ModelAction *act = *rit;
1688 * 1) If RMW and it actually read from something, then we
1689 * already have all relevant edges, so just skip to next
1692 * 2) If RMW and it didn't read from anything, we should
1693 * whatever edge we can get to speed up convergence.
1695 * 3) If normal write, we need to look at earlier actions, so
1696 * continue processing list.
1698 if (curr->is_rmw()) {
1699 if (curr->get_reads_from() != NULL)
1707 /* C++, Section 29.3 statement 7 */
1708 if (last_sc_fence_thread_before && act->is_write() &&
1709 *act < *last_sc_fence_thread_before) {
1710 added = mo_graph->addEdge(act, curr) || added;
1715 * Include at most one act per-thread that "happens
1718 if (act->happens_before(curr)) {
1720 * Note: if act is RMW, just add edge:
1722 * The following edge should be handled elsewhere:
1723 * readfrom(act) --mo--> act
1725 if (act->is_write())
1726 added = mo_graph->addEdge(act, curr) || added;
1727 else if (act->is_read()) {
1728 //if previous read accessed a null, just keep going
1729 if (act->get_reads_from() == NULL)
1731 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1734 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1735 !act->same_thread(curr)) {
1736 /* We have an action that:
1737 (1) did not happen before us
1738 (2) is a read and we are a write
1739 (3) cannot synchronize with us
1740 (4) is in a different thread
1742 that read could potentially read from our write. Note that
1743 these checks are overly conservative at this point, we'll
1744 do more checks before actually removing the
1748 if (thin_air_constraint_may_allow(curr, act)) {
1749 if (!is_infeasible())
1750 futurevalues->push_back(PendingFutureValue(curr, act));
1751 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1752 add_future_value(curr, act);
1759 * All compatible, thread-exclusive promises must be ordered after any
1760 * concrete stores to the same thread, or else they can be merged with
1763 for (unsigned int i = 0; i < promises->size(); i++)
1764 if ((*promises)[i]->is_compatible_exclusive(curr))
1765 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1770 /** Arbitrary reads from the future are not allowed. Section 29.3
1771 * part 9 places some constraints. This method checks one result of constraint
1772 * constraint. Others require compiler support. */
1773 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1775 if (!writer->is_rmw())
1778 if (!reader->is_rmw())
1781 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1782 if (search == reader)
1784 if (search->get_tid() == reader->get_tid() &&
1785 search->happens_before(reader))
1793 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1794 * some constraints. This method checks one the following constraint (others
1795 * require compiler support):
1797 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1799 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1801 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1803 /* Iterate over all threads */
1804 for (i = 0; i < thrd_lists->size(); i++) {
1805 const ModelAction *write_after_read = NULL;
1807 /* Iterate over actions in thread, starting from most recent */
1808 action_list_t *list = &(*thrd_lists)[i];
1809 action_list_t::reverse_iterator rit;
1810 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1811 ModelAction *act = *rit;
1813 /* Don't disallow due to act == reader */
1814 if (!reader->happens_before(act) || reader == act)
1816 else if (act->is_write())
1817 write_after_read = act;
1818 else if (act->is_read() && act->get_reads_from() != NULL)
1819 write_after_read = act->get_reads_from();
1822 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1829 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1830 * The ModelAction under consideration is expected to be taking part in
1831 * release/acquire synchronization as an object of the "reads from" relation.
1832 * Note that this can only provide release sequence support for RMW chains
1833 * which do not read from the future, as those actions cannot be traced until
1834 * their "promise" is fulfilled. Similarly, we may not even establish the
1835 * presence of a release sequence with certainty, as some modification order
1836 * constraints may be decided further in the future. Thus, this function
1837 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1838 * and a boolean representing certainty.
1840 * @param rf The action that might be part of a release sequence. Must be a
1842 * @param release_heads A pass-by-reference style return parameter. After
1843 * execution of this function, release_heads will contain the heads of all the
1844 * relevant release sequences, if any exists with certainty
1845 * @param pending A pass-by-reference style return parameter which is only used
1846 * when returning false (i.e., uncertain). Returns most information regarding
1847 * an uncertain release sequence, including any write operations that might
1848 * break the sequence.
1849 * @return true, if the ModelChecker is certain that release_heads is complete;
1852 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1853 rel_heads_list_t *release_heads,
1854 struct release_seq *pending) const
1856 /* Only check for release sequences if there are no cycles */
1857 if (mo_graph->checkForCycles())
1861 ASSERT(rf->is_write());
1863 if (rf->is_release())
1864 release_heads->push_back(rf);
1865 else if (rf->get_last_fence_release())
1866 release_heads->push_back(rf->get_last_fence_release());
1868 break; /* End of RMW chain */
1870 /** @todo Need to be smarter here... In the linux lock
1871 * example, this will run to the beginning of the program for
1873 /** @todo The way to be smarter here is to keep going until 1
1874 * thread has a release preceded by an acquire and you've seen
1877 /* acq_rel RMW is a sufficient stopping condition */
1878 if (rf->is_acquire() && rf->is_release())
1879 return true; /* complete */
1881 rf = rf->get_reads_from();
1884 /* read from future: need to settle this later */
1886 return false; /* incomplete */
1889 if (rf->is_release())
1890 return true; /* complete */
1892 /* else relaxed write
1893 * - check for fence-release in the same thread (29.8, stmt. 3)
1894 * - check modification order for contiguous subsequence
1895 * -> rf must be same thread as release */
1897 const ModelAction *fence_release = rf->get_last_fence_release();
1898 /* Synchronize with a fence-release unconditionally; we don't need to
1899 * find any more "contiguous subsequence..." for it */
1901 release_heads->push_back(fence_release);
1903 int tid = id_to_int(rf->get_tid());
1904 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1905 action_list_t *list = &(*thrd_lists)[tid];
1906 action_list_t::const_reverse_iterator rit;
1908 /* Find rf in the thread list */
1909 rit = std::find(list->rbegin(), list->rend(), rf);
1910 ASSERT(rit != list->rend());
1912 /* Find the last {write,fence}-release */
1913 for (; rit != list->rend(); rit++) {
1914 if (fence_release && *(*rit) < *fence_release)
1916 if ((*rit)->is_release())
1919 if (rit == list->rend()) {
1920 /* No write-release in this thread */
1921 return true; /* complete */
1922 } else if (fence_release && *(*rit) < *fence_release) {
1923 /* The fence-release is more recent (and so, "stronger") than
1924 * the most recent write-release */
1925 return true; /* complete */
1926 } /* else, need to establish contiguous release sequence */
1927 ModelAction *release = *rit;
1929 ASSERT(rf->same_thread(release));
1931 pending->writes.clear();
1933 bool certain = true;
1934 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1935 if (id_to_int(rf->get_tid()) == (int)i)
1937 list = &(*thrd_lists)[i];
1939 /* Can we ensure no future writes from this thread may break
1940 * the release seq? */
1941 bool future_ordered = false;
1943 ModelAction *last = get_last_action(int_to_id(i));
1944 Thread *th = get_thread(int_to_id(i));
1945 if ((last && rf->happens_before(last)) ||
1948 future_ordered = true;
1950 ASSERT(!th->is_model_thread() || future_ordered);
1952 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1953 const ModelAction *act = *rit;
1954 /* Reach synchronization -> this thread is complete */
1955 if (act->happens_before(release))
1957 if (rf->happens_before(act)) {
1958 future_ordered = true;
1962 /* Only non-RMW writes can break release sequences */
1963 if (!act->is_write() || act->is_rmw())
1966 /* Check modification order */
1967 if (mo_graph->checkReachable(rf, act)) {
1968 /* rf --mo--> act */
1969 future_ordered = true;
1972 if (mo_graph->checkReachable(act, release))
1973 /* act --mo--> release */
1975 if (mo_graph->checkReachable(release, act) &&
1976 mo_graph->checkReachable(act, rf)) {
1977 /* release --mo-> act --mo--> rf */
1978 return true; /* complete */
1980 /* act may break release sequence */
1981 pending->writes.push_back(act);
1984 if (!future_ordered)
1985 certain = false; /* This thread is uncertain */
1989 release_heads->push_back(release);
1990 pending->writes.clear();
1992 pending->release = release;
1999 * An interface for getting the release sequence head(s) with which a
2000 * given ModelAction must synchronize. This function only returns a non-empty
2001 * result when it can locate a release sequence head with certainty. Otherwise,
2002 * it may mark the internal state of the ModelChecker so that it will handle
2003 * the release sequence at a later time, causing @a acquire to update its
2004 * synchronization at some later point in execution.
2006 * @param acquire The 'acquire' action that may synchronize with a release
2008 * @param read The read action that may read from a release sequence; this may
2009 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2010 * when 'acquire' is a fence-acquire)
2011 * @param release_heads A pass-by-reference return parameter. Will be filled
2012 * with the head(s) of the release sequence(s), if they exists with certainty.
2013 * @see ModelChecker::release_seq_heads
2015 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2016 ModelAction *read, rel_heads_list_t *release_heads)
2018 const ModelAction *rf = read->get_reads_from();
2019 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2020 sequence->acquire = acquire;
2021 sequence->read = read;
2023 if (!release_seq_heads(rf, release_heads, sequence)) {
2024 /* add act to 'lazy checking' list */
2025 pending_rel_seqs->push_back(sequence);
2027 snapshot_free(sequence);
2032 * Attempt to resolve all stashed operations that might synchronize with a
2033 * release sequence for a given location. This implements the "lazy" portion of
2034 * determining whether or not a release sequence was contiguous, since not all
2035 * modification order information is present at the time an action occurs.
2037 * @param location The location/object that should be checked for release
2038 * sequence resolutions. A NULL value means to check all locations.
2039 * @param work_queue The work queue to which to add work items as they are
2041 * @return True if any updates occurred (new synchronization, new mo_graph
2044 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2046 bool updated = false;
2047 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2048 while (it != pending_rel_seqs->end()) {
2049 struct release_seq *pending = *it;
2050 ModelAction *acquire = pending->acquire;
2051 const ModelAction *read = pending->read;
2053 /* Only resolve sequences on the given location, if provided */
2054 if (location && read->get_location() != location) {
2059 const ModelAction *rf = read->get_reads_from();
2060 rel_heads_list_t release_heads;
2062 complete = release_seq_heads(rf, &release_heads, pending);
2063 for (unsigned int i = 0; i < release_heads.size(); i++) {
2064 if (!acquire->has_synchronized_with(release_heads[i])) {
2065 if (acquire->synchronize_with(release_heads[i]))
2068 set_bad_synchronization();
2073 /* Re-check all pending release sequences */
2074 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2075 /* Re-check read-acquire for mo_graph edges */
2076 if (acquire->is_read())
2077 work_queue->push_back(MOEdgeWorkEntry(acquire));
2079 /* propagate synchronization to later actions */
2080 action_list_t::reverse_iterator rit = action_trace->rbegin();
2081 for (; (*rit) != acquire; rit++) {
2082 ModelAction *propagate = *rit;
2083 if (acquire->happens_before(propagate)) {
2084 propagate->synchronize_with(acquire);
2085 /* Re-check 'propagate' for mo_graph edges */
2086 work_queue->push_back(MOEdgeWorkEntry(propagate));
2091 it = pending_rel_seqs->erase(it);
2092 snapshot_free(pending);
2098 // If we resolved promises or data races, see if we have realized a data race.
2105 * Performs various bookkeeping operations for the current ModelAction. For
2106 * instance, adds action to the per-object, per-thread action vector and to the
2107 * action trace list of all thread actions.
2109 * @param act is the ModelAction to add.
2111 void ModelChecker::add_action_to_lists(ModelAction *act)
2113 int tid = id_to_int(act->get_tid());
2114 ModelAction *uninit = NULL;
2116 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2117 if (list->empty() && act->is_atomic_var()) {
2118 uninit = new_uninitialized_action(act->get_location());
2119 uninit_id = id_to_int(uninit->get_tid());
2120 list->push_back(uninit);
2122 list->push_back(act);
2124 action_trace->push_back(act);
2126 action_trace->push_front(uninit);
2128 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2129 if (tid >= (int)vec->size())
2130 vec->resize(priv->next_thread_id);
2131 (*vec)[tid].push_back(act);
2133 (*vec)[uninit_id].push_front(uninit);
2135 if ((int)thrd_last_action->size() <= tid)
2136 thrd_last_action->resize(get_num_threads());
2137 (*thrd_last_action)[tid] = act;
2139 (*thrd_last_action)[uninit_id] = uninit;
2141 if (act->is_fence() && act->is_release()) {
2142 if ((int)thrd_last_fence_release->size() <= tid)
2143 thrd_last_fence_release->resize(get_num_threads());
2144 (*thrd_last_fence_release)[tid] = act;
2147 if (act->is_wait()) {
2148 void *mutex_loc = (void *) act->get_value();
2149 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2151 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2152 if (tid >= (int)vec->size())
2153 vec->resize(priv->next_thread_id);
2154 (*vec)[tid].push_back(act);
2159 * @brief Get the last action performed by a particular Thread
2160 * @param tid The thread ID of the Thread in question
2161 * @return The last action in the thread
2163 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2165 int threadid = id_to_int(tid);
2166 if (threadid < (int)thrd_last_action->size())
2167 return (*thrd_last_action)[id_to_int(tid)];
2173 * @brief Get the last fence release performed by a particular Thread
2174 * @param tid The thread ID of the Thread in question
2175 * @return The last fence release in the thread, if one exists; NULL otherwise
2177 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2179 int threadid = id_to_int(tid);
2180 if (threadid < (int)thrd_last_fence_release->size())
2181 return (*thrd_last_fence_release)[id_to_int(tid)];
2187 * Gets the last memory_order_seq_cst write (in the total global sequence)
2188 * performed on a particular object (i.e., memory location), not including the
2190 * @param curr The current ModelAction; also denotes the object location to
2192 * @return The last seq_cst write
2194 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2196 void *location = curr->get_location();
2197 action_list_t *list = get_safe_ptr_action(obj_map, location);
2198 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2199 action_list_t::reverse_iterator rit;
2200 for (rit = list->rbegin(); rit != list->rend(); rit++)
2201 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2207 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2208 * performed in a particular thread, prior to a particular fence.
2209 * @param tid The ID of the thread to check
2210 * @param before_fence The fence from which to begin the search; if NULL, then
2211 * search for the most recent fence in the thread.
2212 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2214 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2216 /* All fences should have NULL location */
2217 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2218 action_list_t::reverse_iterator rit = list->rbegin();
2221 for (; rit != list->rend(); rit++)
2222 if (*rit == before_fence)
2225 ASSERT(*rit == before_fence);
2229 for (; rit != list->rend(); rit++)
2230 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2236 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2237 * location). This function identifies the mutex according to the current
2238 * action, which is presumed to perform on the same mutex.
2239 * @param curr The current ModelAction; also denotes the object location to
2241 * @return The last unlock operation
2243 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2245 void *location = curr->get_location();
2246 action_list_t *list = get_safe_ptr_action(obj_map, location);
2247 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2248 action_list_t::reverse_iterator rit;
2249 for (rit = list->rbegin(); rit != list->rend(); rit++)
2250 if ((*rit)->is_unlock() || (*rit)->is_wait())
2255 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2257 ModelAction *parent = get_last_action(tid);
2259 parent = get_thread(tid)->get_creation();
2264 * Returns the clock vector for a given thread.
2265 * @param tid The thread whose clock vector we want
2266 * @return Desired clock vector
2268 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2270 return get_parent_action(tid)->get_cv();
2274 * Resolve a set of Promises with a current write. The set is provided in the
2275 * Node corresponding to @a write.
2276 * @param write The ModelAction that is fulfilling Promises
2277 * @return True if promises were resolved; false otherwise
2279 bool ModelChecker::resolve_promises(ModelAction *write)
2281 bool haveResolved = false;
2282 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2283 promise_list_t mustResolve, resolved;
2285 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2286 Promise *promise = (*promises)[promise_index];
2287 if (write->get_node()->get_promise(i)) {
2288 ModelAction *read = promise->get_action();
2289 read_from(read, write);
2290 //Make sure the promise's value matches the write's value
2291 ASSERT(promise->is_compatible(write));
2292 mo_graph->resolvePromise(read, write, &mustResolve);
2294 resolved.push_back(promise);
2295 promises->erase(promises->begin() + promise_index);
2296 actions_to_check.push_back(read);
2298 haveResolved = true;
2303 for (unsigned int i = 0; i < mustResolve.size(); i++) {
2304 if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
2306 priv->failed_promise = true;
2308 for (unsigned int i = 0; i < resolved.size(); i++)
2310 //Check whether reading these writes has made threads unable to
2313 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2314 ModelAction *read = actions_to_check[i];
2315 mo_check_promises(read, true);
2318 return haveResolved;
2322 * Compute the set of promises that could potentially be satisfied by this
2323 * action. Note that the set computation actually appears in the Node, not in
2325 * @param curr The ModelAction that may satisfy promises
2327 void ModelChecker::compute_promises(ModelAction *curr)
2329 for (unsigned int i = 0; i < promises->size(); i++) {
2330 Promise *promise = (*promises)[i];
2331 const ModelAction *act = promise->get_action();
2332 if (!act->happens_before(curr) &&
2334 !act->could_synchronize_with(curr) &&
2335 !act->same_thread(curr) &&
2336 act->get_location() == curr->get_location() &&
2337 promise->get_value() == curr->get_value()) {
2338 curr->get_node()->set_promise(i, act->is_rmw());
2343 /** Checks promises in response to change in ClockVector Threads. */
2344 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2346 for (unsigned int i = 0; i < promises->size(); i++) {
2347 Promise *promise = (*promises)[i];
2348 const ModelAction *act = promise->get_action();
2349 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2350 merge_cv->synchronized_since(act)) {
2351 if (promise->eliminate_thread(tid)) {
2352 //Promise has failed
2353 priv->failed_promise = true;
2360 void ModelChecker::check_promises_thread_disabled()
2362 for (unsigned int i = 0; i < promises->size(); i++) {
2363 Promise *promise = (*promises)[i];
2364 if (promise->has_failed()) {
2365 priv->failed_promise = true;
2372 * @brief Checks promises in response to addition to modification order for
2375 * We test whether threads are still available for satisfying promises after an
2376 * addition to our modification order constraints. Those that are unavailable
2377 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2378 * that promise has failed.
2380 * @param act The ModelAction which updated the modification order
2381 * @param is_read_check Should be true if act is a read and we must check for
2382 * updates to the store from which it read (there is a distinction here for
2383 * RMW's, which are both a load and a store)
2385 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2387 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2389 for (unsigned int i = 0; i < promises->size(); i++) {
2390 Promise *promise = (*promises)[i];
2391 const ModelAction *pread = promise->get_action();
2393 // Is this promise on the same location?
2394 if (!pread->same_var(write))
2397 if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
2398 priv->failed_promise = true;
2402 // Don't do any lookups twice for the same thread
2403 if (!promise->thread_is_available(act->get_tid()))
2406 if (mo_graph->checkReachable(promise, write)) {
2407 if (mo_graph->checkPromise(write, promise)) {
2408 priv->failed_promise = true;
2416 * Compute the set of writes that may break the current pending release
2417 * sequence. This information is extracted from previou release sequence
2420 * @param curr The current ModelAction. Must be a release sequence fixup
2423 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2425 if (pending_rel_seqs->empty())
2428 struct release_seq *pending = pending_rel_seqs->back();
2429 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2430 const ModelAction *write = pending->writes[i];
2431 curr->get_node()->add_relseq_break(write);
2434 /* NULL means don't break the sequence; just synchronize */
2435 curr->get_node()->add_relseq_break(NULL);
2439 * Build up an initial set of all past writes that this 'read' action may read
2440 * from. This set is determined by the clock vector's "happens before"
2442 * @param curr is the current ModelAction that we are exploring; it must be a
2445 void ModelChecker::build_reads_from_past(ModelAction *curr)
2447 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2449 ASSERT(curr->is_read());
2451 ModelAction *last_sc_write = NULL;
2453 if (curr->is_seqcst())
2454 last_sc_write = get_last_seq_cst_write(curr);
2456 /* Iterate over all threads */
2457 for (i = 0; i < thrd_lists->size(); i++) {
2458 /* Iterate over actions in thread, starting from most recent */
2459 action_list_t *list = &(*thrd_lists)[i];
2460 action_list_t::reverse_iterator rit;
2461 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2462 ModelAction *act = *rit;
2464 /* Only consider 'write' actions */
2465 if (!act->is_write() || act == curr)
2468 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2469 bool allow_read = true;
2471 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2473 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2477 /* Only add feasible reads */
2478 mo_graph->startChanges();
2479 r_modification_order(curr, act);
2480 if (!is_infeasible())
2481 curr->get_node()->add_read_from(act);
2482 mo_graph->rollbackChanges();
2485 /* Include at most one act per-thread that "happens before" curr */
2486 if (act->happens_before(curr))
2490 /* We may find no valid may-read-from only if the execution is doomed */
2491 if (!curr->get_node()->get_read_from_size()) {
2492 priv->no_valid_reads = true;
2496 if (DBG_ENABLED()) {
2497 model_print("Reached read action:\n");
2499 model_print("Printing may_read_from\n");
2500 curr->get_node()->print_may_read_from();
2501 model_print("End printing may_read_from\n");
2505 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2508 /* UNINIT actions don't have a Node, and they never sleep */
2509 if (write->is_uninitialized())
2511 Node *prevnode = write->get_node()->get_parent();
2513 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2514 if (write->is_release() && thread_sleep)
2516 if (!write->is_rmw()) {
2519 if (write->get_reads_from() == NULL)
2521 write = write->get_reads_from();
2526 * @brief Create a new action representing an uninitialized atomic
2527 * @param location The memory location of the atomic object
2528 * @return A pointer to a new ModelAction
2530 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2532 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2533 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2534 act->create_cv(NULL);
2538 static void print_list(action_list_t *list)
2540 action_list_t::iterator it;
2542 model_print("---------------------------------------------------------------------\n");
2544 unsigned int hash = 0;
2546 for (it = list->begin(); it != list->end(); it++) {
2548 hash = hash^(hash<<3)^((*it)->hash());
2550 model_print("HASH %u\n", hash);
2551 model_print("---------------------------------------------------------------------\n");
2554 #if SUPPORT_MOD_ORDER_DUMP
2555 void ModelChecker::dumpGraph(char *filename) const
2558 sprintf(buffer, "%s.dot", filename);
2559 FILE *file = fopen(buffer, "w");
2560 fprintf(file, "digraph %s {\n", filename);
2561 mo_graph->dumpNodes(file);
2562 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2564 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2565 ModelAction *action = *it;
2566 if (action->is_read()) {
2567 fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2568 if (action->get_reads_from() != NULL)
2569 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2571 if (thread_array[action->get_tid()] != NULL) {
2572 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2575 thread_array[action->get_tid()] = action;
2577 fprintf(file, "}\n");
2578 model_free(thread_array);
2583 /** @brief Prints an execution trace summary. */
2584 void ModelChecker::print_summary() const
2586 #if SUPPORT_MOD_ORDER_DUMP
2587 char buffername[100];
2588 sprintf(buffername, "exec%04u", stats.num_total);
2589 mo_graph->dumpGraphToFile(buffername);
2590 sprintf(buffername, "graph%04u", stats.num_total);
2591 dumpGraph(buffername);
2594 model_print("Execution %d:", stats.num_total);
2595 if (isfeasibleprefix())
2598 print_infeasibility(" INFEASIBLE");
2599 print_list(action_trace);
2604 * Add a Thread to the system for the first time. Should only be called once
2606 * @param t The Thread to add
2608 void ModelChecker::add_thread(Thread *t)
2610 thread_map->put(id_to_int(t->get_id()), t);
2611 scheduler->add_thread(t);
2615 * Removes a thread from the scheduler.
2616 * @param the thread to remove.
2618 void ModelChecker::remove_thread(Thread *t)
2620 scheduler->remove_thread(t);
2624 * @brief Get a Thread reference by its ID
2625 * @param tid The Thread's ID
2626 * @return A Thread reference
2628 Thread * ModelChecker::get_thread(thread_id_t tid) const
2630 return thread_map->get(id_to_int(tid));
2634 * @brief Get a reference to the Thread in which a ModelAction was executed
2635 * @param act The ModelAction
2636 * @return A Thread reference
2638 Thread * ModelChecker::get_thread(const ModelAction *act) const
2640 return get_thread(act->get_tid());
2644 * @brief Check if a Thread is currently enabled
2645 * @param t The Thread to check
2646 * @return True if the Thread is currently enabled
2648 bool ModelChecker::is_enabled(Thread *t) const
2650 return scheduler->is_enabled(t);
2654 * @brief Check if a Thread is currently enabled
2655 * @param tid The ID of the Thread to check
2656 * @return True if the Thread is currently enabled
2658 bool ModelChecker::is_enabled(thread_id_t tid) const
2660 return scheduler->is_enabled(tid);
2664 * Switch from a user-context to the "master thread" context (a.k.a. system
2665 * context). This switch is made with the intention of exploring a particular
2666 * model-checking action (described by a ModelAction object). Must be called
2667 * from a user-thread context.
2669 * @param act The current action that will be explored. May be NULL only if
2670 * trace is exiting via an assertion (see ModelChecker::set_assert and
2671 * ModelChecker::has_asserted).
2672 * @return Return the value returned by the current action
2674 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2677 Thread *old = thread_current();
2678 set_current_action(act);
2679 if (Thread::swap(old, &system_context) < 0) {
2680 perror("swap threads");
2683 return old->get_return_value();
2687 * Takes the next step in the execution, if possible.
2688 * @param curr The current step to take
2689 * @return Returns true (success) if a step was taken and false otherwise.
2691 bool ModelChecker::take_step(ModelAction *curr)
2696 Thread *curr_thrd = get_thread(curr);
2697 ASSERT(curr_thrd->get_state() == THREAD_READY);
2699 curr = check_current_action(curr);
2701 /* Infeasible -> don't take any more steps */
2702 if (is_infeasible())
2704 else if (isfeasibleprefix() && have_bug_reports()) {
2709 if (params.bound != 0)
2710 if (priv->used_sequence_numbers > params.bound)
2713 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2714 scheduler->remove_thread(curr_thrd);
2716 Thread *next_thrd = get_next_thread(curr);
2717 next_thrd = scheduler->next_thread(next_thrd);
2719 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2720 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2723 * Launch end-of-execution release sequence fixups only when there are:
2725 * (1) no more user threads to run (or when execution replay chooses
2726 * the 'model_thread')
2727 * (2) pending release sequences
2728 * (3) pending assertions (i.e., data races)
2729 * (4) no pending promises
2731 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2732 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2733 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2734 pending_rel_seqs->size());
2735 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2736 std::memory_order_seq_cst, NULL, VALUE_NONE,
2738 set_current_action(fixup);
2742 /* next_thrd == NULL -> don't take any more steps */
2746 if (next_thrd->get_pending() != NULL) {
2747 /* restart a pending action */
2748 set_current_action(next_thrd->get_pending());
2749 next_thrd->set_pending(NULL);
2753 /* Return false only if swap fails with an error */
2754 return (Thread::swap(&system_context, next_thrd) == 0);
2757 /** Wrapper to run the user's main function, with appropriate arguments */
2758 void user_main_wrapper(void *)
2760 user_main(model->params.argc, model->params.argv);
2763 /** @brief Run ModelChecker for the user program */
2764 void ModelChecker::run()
2768 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2772 /* Run user thread up to its first action */
2773 scheduler->next_thread(t);
2774 Thread::swap(&system_context, t);
2776 /* Wait for all threads to complete */
2777 while (take_step(priv->current_action));
2778 } while (next_execution());