10 #include "snapshot-interface.h"
12 #include "clockvector.h"
13 #include "cyclegraph.h"
16 #include "threads-model.h"
19 #define INITIAL_THREAD_ID 0
24 bug_message(const char *str) {
25 const char *fmt = " [BUG] %s\n";
26 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
27 sprintf(msg, fmt, str);
29 ~bug_message() { if (msg) snapshot_free(msg); }
32 void print() { model_print("%s", msg); }
38 * Structure for holding small ModelChecker members that should be snapshotted
40 struct model_snapshot_members {
41 model_snapshot_members() :
43 /* First thread created will have id INITIAL_THREAD_ID */
44 next_thread_id(INITIAL_THREAD_ID),
45 used_sequence_numbers(0),
49 failed_promise(false),
50 too_many_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 ModelAction *current_action;
62 unsigned int next_thread_id;
63 modelclock_t used_sequence_numbers;
64 ModelAction *next_backtrack;
65 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
66 struct execution_stats stats;
69 /** @brief Incorrectly-ordered synchronization was made */
70 bool bad_synchronization;
76 /** @brief Constructor */
77 ModelChecker::ModelChecker(struct model_params params) :
78 /* Initialize default scheduler */
80 scheduler(new Scheduler()),
82 earliest_diverge(NULL),
83 action_trace(new action_list_t()),
84 thread_map(new HashTable<int, Thread *, int>()),
85 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
86 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
89 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
90 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
91 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
92 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
93 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
123 delete thrd_last_fence_release;
130 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
132 action_list_t *tmp = hash->get(ptr);
134 tmp = new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
142 std::vector<action_list_t> *tmp = hash->get(ptr);
144 tmp = new std::vector<action_list_t>();
151 * Restores user program to initial state and resets all model-checker data
154 void ModelChecker::reset_to_initial_state()
156 DEBUG("+++ Resetting to initial state +++\n");
157 node_stack->reset_execution();
159 /* Print all model-checker output before rollback */
162 snapshot_backtrack_before(0);
165 /** @return a thread ID for a new Thread */
166 thread_id_t ModelChecker::get_next_id()
168 return priv->next_thread_id++;
171 /** @return the number of user threads created during this execution */
172 unsigned int ModelChecker::get_num_threads() const
174 return priv->next_thread_id;
178 * Must be called from user-thread context (e.g., through the global
179 * thread_current() interface)
181 * @return The currently executing Thread.
183 Thread * ModelChecker::get_current_thread() const
185 return scheduler->get_current_thread();
188 /** @return a sequence number for a new ModelAction */
189 modelclock_t ModelChecker::get_next_seq_num()
191 return ++priv->used_sequence_numbers;
194 Node * ModelChecker::get_curr_node() const
196 return node_stack->get_head();
200 * @brief Choose the next thread to execute.
202 * This function chooses the next thread that should execute. It can force the
203 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
204 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
205 * The model-checker may have no preference regarding the next thread (i.e.,
206 * when exploring a new execution ordering), in which case this will return
208 * @param curr The current ModelAction. This action might guide the choice of
210 * @return The next thread to run. If the model-checker has no preference, NULL.
212 Thread * ModelChecker::get_next_thread(ModelAction *curr)
217 /* Do not split atomic actions. */
219 return thread_current();
220 else if (curr->get_type() == THREAD_CREATE)
221 return curr->get_thread_operand();
224 /* Have we completed exploring the preselected path? */
228 /* Else, we are trying to replay an execution */
229 ModelAction *next = node_stack->get_next()->get_action();
231 if (next == diverge) {
232 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
233 earliest_diverge = diverge;
235 Node *nextnode = next->get_node();
236 Node *prevnode = nextnode->get_parent();
237 scheduler->update_sleep_set(prevnode);
239 /* Reached divergence point */
240 if (nextnode->increment_misc()) {
241 /* The next node will try to satisfy a different misc_index values. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_promise()) {
245 /* The next node will try to satisfy a different set of promises. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_read_from()) {
249 /* The next node will read from a different value. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_future_value()) {
253 /* The next node will try to read from a different future value. */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
256 } else if (nextnode->increment_relseq_break()) {
257 /* The next node will try to resolve a release sequence differently */
258 tid = next->get_tid();
259 node_stack->pop_restofstack(2);
262 /* Make a different thread execute for next step */
263 scheduler->add_sleep(get_thread(next->get_tid()));
264 tid = prevnode->get_next_backtrack();
265 /* Make sure the backtracked thread isn't sleeping. */
266 node_stack->pop_restofstack(1);
267 if (diverge == earliest_diverge) {
268 earliest_diverge = prevnode->get_action();
271 /* The correct sleep set is in the parent node. */
274 DEBUG("*** Divergence point ***\n");
278 tid = next->get_tid();
280 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
281 ASSERT(tid != THREAD_ID_T_NONE);
282 return thread_map->get(id_to_int(tid));
286 * We need to know what the next actions of all threads in the sleep
287 * set will be. This method computes them and stores the actions at
288 * the corresponding thread object's pending action.
291 void ModelChecker::execute_sleep_set()
293 for (unsigned int i = 0; i < get_num_threads(); i++) {
294 thread_id_t tid = int_to_id(i);
295 Thread *thr = get_thread(tid);
296 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
297 thr->set_state(THREAD_RUNNING);
298 scheduler->next_thread(thr);
299 Thread::swap(&system_context, thr);
300 priv->current_action->set_sleep_flag();
301 thr->set_pending(priv->current_action);
306 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
308 for (unsigned int i = 0; i < get_num_threads(); i++) {
309 Thread *thr = get_thread(int_to_id(i));
310 if (scheduler->is_sleep_set(thr)) {
311 ModelAction *pending_act = thr->get_pending();
312 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
313 //Remove this thread from sleep set
314 scheduler->remove_sleep(thr);
319 /** @brief Alert the model-checker that an incorrectly-ordered
320 * synchronization was made */
321 void ModelChecker::set_bad_synchronization()
323 priv->bad_synchronization = true;
326 bool ModelChecker::has_asserted() const
328 return priv->asserted;
331 void ModelChecker::set_assert()
333 priv->asserted = true;
337 * Check if we are in a deadlock. Should only be called at the end of an
338 * execution, although it should not give false positives in the middle of an
339 * execution (there should be some ENABLED thread).
341 * @return True if program is in a deadlock; false otherwise
343 bool ModelChecker::is_deadlocked() const
345 bool blocking_threads = false;
346 for (unsigned int i = 0; i < get_num_threads(); i++) {
347 thread_id_t tid = int_to_id(i);
350 Thread *t = get_thread(tid);
351 if (!t->is_model_thread() && t->get_pending())
352 blocking_threads = true;
354 return blocking_threads;
358 * Check if this is a complete execution. That is, have all thread completed
359 * execution (rather than exiting because sleep sets have forced a redundant
362 * @return True if the execution is complete.
364 bool ModelChecker::is_complete_execution() const
366 for (unsigned int i = 0; i < get_num_threads(); i++)
367 if (is_enabled(int_to_id(i)))
373 * @brief Assert a bug in the executing program.
375 * Use this function to assert any sort of bug in the user program. If the
376 * current trace is feasible (actually, a prefix of some feasible execution),
377 * then this execution will be aborted, printing the appropriate message. If
378 * the current trace is not yet feasible, the error message will be stashed and
379 * printed if the execution ever becomes feasible.
381 * @param msg Descriptive message for the bug (do not include newline char)
382 * @return True if bug is immediately-feasible
384 bool ModelChecker::assert_bug(const char *msg)
386 priv->bugs.push_back(new bug_message(msg));
388 if (isfeasibleprefix()) {
396 * @brief Assert a bug in the executing program, asserted by a user thread
397 * @see ModelChecker::assert_bug
398 * @param msg Descriptive message for the bug (do not include newline char)
400 void ModelChecker::assert_user_bug(const char *msg)
402 /* If feasible bug, bail out now */
404 switch_to_master(NULL);
407 /** @return True, if any bugs have been reported for this execution */
408 bool ModelChecker::have_bug_reports() const
410 return priv->bugs.size() != 0;
413 /** @brief Print bug report listing for this execution (if any bugs exist) */
414 void ModelChecker::print_bugs() const
416 if (have_bug_reports()) {
417 model_print("Bug report: %zu bug%s detected\n",
419 priv->bugs.size() > 1 ? "s" : "");
420 for (unsigned int i = 0; i < priv->bugs.size(); i++)
421 priv->bugs[i]->print();
426 * @brief Record end-of-execution stats
428 * Must be run when exiting an execution. Records various stats.
429 * @see struct execution_stats
431 void ModelChecker::record_stats()
434 if (!isfeasibleprefix())
435 stats.num_infeasible++;
436 else if (have_bug_reports())
437 stats.num_buggy_executions++;
438 else if (is_complete_execution())
439 stats.num_complete++;
441 stats.num_redundant++;
444 /** @brief Print execution stats */
445 void ModelChecker::print_stats() const
447 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
448 model_print("Number of redundant executions: %d\n", stats.num_redundant);
449 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
450 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
451 model_print("Total executions: %d\n", stats.num_total);
452 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
456 * @brief End-of-exeuction print
457 * @param printbugs Should any existing bugs be printed?
459 void ModelChecker::print_execution(bool printbugs) const
461 print_program_output();
463 if (DBG_ENABLED() || params.verbose) {
464 model_print("Earliest divergence point since last feasible execution:\n");
465 if (earliest_diverge)
466 earliest_diverge->print();
468 model_print("(Not set)\n");
474 /* Don't print invalid bugs */
483 * Queries the model-checker for more executions to explore and, if one
484 * exists, resets the model-checker state to execute a new execution.
486 * @return If there are more executions to explore, return true. Otherwise,
489 bool ModelChecker::next_execution()
492 /* Is this execution a feasible execution that's worth bug-checking? */
493 bool complete = isfeasibleprefix() && (is_complete_execution() ||
496 /* End-of-execution bug checks */
499 assert_bug("Deadlock detected");
507 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
508 print_execution(complete);
510 clear_program_output();
513 earliest_diverge = NULL;
515 if ((diverge = get_next_backtrack()) == NULL)
519 model_print("Next execution will diverge at:\n");
523 reset_to_initial_state();
527 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
529 switch (act->get_type()) {
534 /* Optimization: relaxed operations don't need backtracking */
535 if (act->is_relaxed())
537 /* linear search: from most recent to oldest */
538 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
539 action_list_t::reverse_iterator rit;
540 for (rit = list->rbegin(); rit != list->rend(); rit++) {
541 ModelAction *prev = *rit;
542 if (prev->could_synchronize_with(act))
548 case ATOMIC_TRYLOCK: {
549 /* linear search: from most recent to oldest */
550 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
551 action_list_t::reverse_iterator rit;
552 for (rit = list->rbegin(); rit != list->rend(); rit++) {
553 ModelAction *prev = *rit;
554 if (act->is_conflicting_lock(prev))
559 case ATOMIC_UNLOCK: {
560 /* linear search: from most recent to oldest */
561 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
562 action_list_t::reverse_iterator rit;
563 for (rit = list->rbegin(); rit != list->rend(); rit++) {
564 ModelAction *prev = *rit;
565 if (!act->same_thread(prev) && prev->is_failed_trylock())
571 /* linear search: from most recent to oldest */
572 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
573 action_list_t::reverse_iterator rit;
574 for (rit = list->rbegin(); rit != list->rend(); rit++) {
575 ModelAction *prev = *rit;
576 if (!act->same_thread(prev) && prev->is_failed_trylock())
578 if (!act->same_thread(prev) && prev->is_notify())
584 case ATOMIC_NOTIFY_ALL:
585 case ATOMIC_NOTIFY_ONE: {
586 /* linear search: from most recent to oldest */
587 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
588 action_list_t::reverse_iterator rit;
589 for (rit = list->rbegin(); rit != list->rend(); rit++) {
590 ModelAction *prev = *rit;
591 if (!act->same_thread(prev) && prev->is_wait())
602 /** This method finds backtracking points where we should try to
603 * reorder the parameter ModelAction against.
605 * @param the ModelAction to find backtracking points for.
607 void ModelChecker::set_backtracking(ModelAction *act)
609 Thread *t = get_thread(act);
610 ModelAction *prev = get_last_conflict(act);
614 Node *node = prev->get_node()->get_parent();
616 int low_tid, high_tid;
617 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
618 low_tid = id_to_int(act->get_tid());
619 high_tid = low_tid + 1;
622 high_tid = get_num_threads();
625 for (int i = low_tid; i < high_tid; i++) {
626 thread_id_t tid = int_to_id(i);
628 /* Make sure this thread can be enabled here. */
629 if (i >= node->get_num_threads())
632 /* Don't backtrack into a point where the thread is disabled or sleeping. */
633 if (node->enabled_status(tid) != THREAD_ENABLED)
636 /* Check if this has been explored already */
637 if (node->has_been_explored(tid))
640 /* See if fairness allows */
641 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
643 for (int t = 0; t < node->get_num_threads(); t++) {
644 thread_id_t tother = int_to_id(t);
645 if (node->is_enabled(tother) && node->has_priority(tother)) {
653 /* Cache the latest backtracking point */
654 set_latest_backtrack(prev);
656 /* If this is a new backtracking point, mark the tree */
657 if (!node->set_backtrack(tid))
659 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
660 id_to_int(prev->get_tid()),
661 id_to_int(t->get_id()));
670 * @brief Cache the a backtracking point as the "most recent", if eligible
672 * Note that this does not prepare the NodeStack for this backtracking
673 * operation, it only caches the action on a per-execution basis
675 * @param act The operation at which we should explore a different next action
676 * (i.e., backtracking point)
677 * @return True, if this action is now the most recent backtracking point;
680 bool ModelChecker::set_latest_backtrack(ModelAction *act)
682 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
683 priv->next_backtrack = act;
690 * Returns last backtracking point. The model checker will explore a different
691 * path for this point in the next execution.
692 * @return The ModelAction at which the next execution should diverge.
694 ModelAction * ModelChecker::get_next_backtrack()
696 ModelAction *next = priv->next_backtrack;
697 priv->next_backtrack = NULL;
702 * Processes a read or rmw model action.
703 * @param curr is the read model action to process.
704 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
705 * @return True if processing this read updates the mo_graph.
707 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
709 uint64_t value = VALUE_NONE;
710 bool updated = false;
712 const ModelAction *reads_from = curr->get_node()->get_read_from();
713 if (reads_from != NULL) {
714 mo_graph->startChanges();
716 value = reads_from->get_value();
717 bool r_status = false;
719 if (!second_part_of_rmw) {
720 check_recency(curr, reads_from);
721 r_status = r_modification_order(curr, reads_from);
724 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
725 mo_graph->rollbackChanges();
726 priv->too_many_reads = false;
730 read_from(curr, reads_from);
731 mo_graph->commitChanges();
732 mo_check_promises(curr->get_tid(), reads_from, NULL);
735 } else if (!second_part_of_rmw) {
736 /* Read from future value */
737 struct future_value fv = curr->get_node()->get_future_value();
738 Promise *promise = new Promise(curr, fv);
740 curr->set_read_from_promise(promise);
741 promises->push_back(promise);
743 get_thread(curr)->set_return_value(value);
749 * Processes a lock, trylock, or unlock model action. @param curr is
750 * the read model action to process.
752 * The try lock operation checks whether the lock is taken. If not,
753 * it falls to the normal lock operation case. If so, it returns
756 * The lock operation has already been checked that it is enabled, so
757 * it just grabs the lock and synchronizes with the previous unlock.
759 * The unlock operation has to re-enable all of the threads that are
760 * waiting on the lock.
762 * @return True if synchronization was updated; false otherwise
764 bool ModelChecker::process_mutex(ModelAction *curr)
766 std::mutex *mutex = NULL;
767 struct std::mutex_state *state = NULL;
769 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
770 mutex = (std::mutex *)curr->get_location();
771 state = mutex->get_state();
772 } else if (curr->is_wait()) {
773 mutex = (std::mutex *)curr->get_value();
774 state = mutex->get_state();
777 switch (curr->get_type()) {
778 case ATOMIC_TRYLOCK: {
779 bool success = !state->islocked;
780 curr->set_try_lock(success);
782 get_thread(curr)->set_return_value(0);
785 get_thread(curr)->set_return_value(1);
787 //otherwise fall into the lock case
789 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
790 assert_bug("Lock access before initialization");
791 state->islocked = true;
792 ModelAction *unlock = get_last_unlock(curr);
793 //synchronize with the previous unlock statement
794 if (unlock != NULL) {
795 curr->synchronize_with(unlock);
800 case ATOMIC_UNLOCK: {
802 state->islocked = false;
803 //wake up the other threads
804 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
805 //activate all the waiting threads
806 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
807 scheduler->wake(get_thread(*rit));
814 state->islocked = false;
815 //wake up the other threads
816 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
817 //activate all the waiting threads
818 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
819 scheduler->wake(get_thread(*rit));
822 //check whether we should go to sleep or not...simulate spurious failures
823 if (curr->get_node()->get_misc() == 0) {
824 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
826 scheduler->sleep(get_thread(curr));
830 case ATOMIC_NOTIFY_ALL: {
831 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
832 //activate all the waiting threads
833 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
834 scheduler->wake(get_thread(*rit));
839 case ATOMIC_NOTIFY_ONE: {
840 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
841 int wakeupthread = curr->get_node()->get_misc();
842 action_list_t::iterator it = waiters->begin();
843 advance(it, wakeupthread);
844 scheduler->wake(get_thread(*it));
855 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
857 /* Do more ambitious checks now that mo is more complete */
858 if (mo_may_allow(writer, reader)) {
859 Node *node = reader->get_node();
861 /* Find an ancestor thread which exists at the time of the reader */
862 Thread *write_thread = get_thread(writer);
863 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
864 write_thread = write_thread->get_parent();
866 struct future_value fv = {
868 writer->get_seq_number() + params.maxfuturedelay,
869 write_thread->get_id(),
871 if (node->add_future_value(fv))
872 set_latest_backtrack(reader);
877 * Process a write ModelAction
878 * @param curr The ModelAction to process
879 * @return True if the mo_graph was updated or promises were resolved
881 bool ModelChecker::process_write(ModelAction *curr)
883 bool updated_mod_order = w_modification_order(curr);
884 bool updated_promises = resolve_promises(curr);
886 if (promises->size() == 0) {
887 for (unsigned int i = 0; i < futurevalues->size(); i++) {
888 struct PendingFutureValue pfv = (*futurevalues)[i];
889 add_future_value(pfv.writer, pfv.act);
891 futurevalues->clear();
894 mo_graph->commitChanges();
895 mo_check_promises(curr->get_tid(), curr, NULL);
897 get_thread(curr)->set_return_value(VALUE_NONE);
898 return updated_mod_order || updated_promises;
902 * Process a fence ModelAction
903 * @param curr The ModelAction to process
904 * @return True if synchronization was updated
906 bool ModelChecker::process_fence(ModelAction *curr)
909 * fence-relaxed: no-op
910 * fence-release: only log the occurence (not in this function), for
911 * use in later synchronization
912 * fence-acquire (this function): search for hypothetical release
915 bool updated = false;
916 if (curr->is_acquire()) {
917 action_list_t *list = action_trace;
918 action_list_t::reverse_iterator rit;
919 /* Find X : is_read(X) && X --sb-> curr */
920 for (rit = list->rbegin(); rit != list->rend(); rit++) {
921 ModelAction *act = *rit;
924 if (act->get_tid() != curr->get_tid())
926 /* Stop at the beginning of the thread */
927 if (act->is_thread_start())
929 /* Stop once we reach a prior fence-acquire */
930 if (act->is_fence() && act->is_acquire())
934 /* read-acquire will find its own release sequences */
935 if (act->is_acquire())
938 /* Establish hypothetical release sequences */
939 rel_heads_list_t release_heads;
940 get_release_seq_heads(curr, act, &release_heads);
941 for (unsigned int i = 0; i < release_heads.size(); i++)
942 if (!curr->synchronize_with(release_heads[i]))
943 set_bad_synchronization();
944 if (release_heads.size() != 0)
952 * @brief Process the current action for thread-related activity
954 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
955 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
956 * synchronization, etc. This function is a no-op for non-THREAD actions
957 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
959 * @param curr The current action
960 * @return True if synchronization was updated or a thread completed
962 bool ModelChecker::process_thread_action(ModelAction *curr)
964 bool updated = false;
966 switch (curr->get_type()) {
967 case THREAD_CREATE: {
968 Thread *th = curr->get_thread_operand();
969 th->set_creation(curr);
970 /* Promises can be satisfied by children */
971 for (unsigned int i = 0; i < promises->size(); i++) {
972 Promise *promise = (*promises)[i];
973 if (promise->thread_is_available(curr->get_tid()))
974 promise->add_thread(th->get_id());
979 Thread *blocking = curr->get_thread_operand();
980 ModelAction *act = get_last_action(blocking->get_id());
981 curr->synchronize_with(act);
982 updated = true; /* trigger rel-seq checks */
985 case THREAD_FINISH: {
986 Thread *th = get_thread(curr);
987 while (!th->wait_list_empty()) {
988 ModelAction *act = th->pop_wait_list();
989 scheduler->wake(get_thread(act));
992 /* Completed thread can't satisfy promises */
993 for (unsigned int i = 0; i < promises->size(); i++) {
994 Promise *promise = (*promises)[i];
995 if (promise->thread_is_available(th->get_id()))
996 if (promise->eliminate_thread(th->get_id()))
997 priv->failed_promise = true;
999 updated = true; /* trigger rel-seq checks */
1002 case THREAD_START: {
1003 check_promises(curr->get_tid(), NULL, curr->get_cv());
1014 * @brief Process the current action for release sequence fixup activity
1016 * Performs model-checker release sequence fixups for the current action,
1017 * forcing a single pending release sequence to break (with a given, potential
1018 * "loose" write) or to complete (i.e., synchronize). If a pending release
1019 * sequence forms a complete release sequence, then we must perform the fixup
1020 * synchronization, mo_graph additions, etc.
1022 * @param curr The current action; must be a release sequence fixup action
1023 * @param work_queue The work queue to which to add work items as they are
1026 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1028 const ModelAction *write = curr->get_node()->get_relseq_break();
1029 struct release_seq *sequence = pending_rel_seqs->back();
1030 pending_rel_seqs->pop_back();
1032 ModelAction *acquire = sequence->acquire;
1033 const ModelAction *rf = sequence->rf;
1034 const ModelAction *release = sequence->release;
1038 ASSERT(release->same_thread(rf));
1040 if (write == NULL) {
1042 * @todo Forcing a synchronization requires that we set
1043 * modification order constraints. For instance, we can't allow
1044 * a fixup sequence in which two separate read-acquire
1045 * operations read from the same sequence, where the first one
1046 * synchronizes and the other doesn't. Essentially, we can't
1047 * allow any writes to insert themselves between 'release' and
1051 /* Must synchronize */
1052 if (!acquire->synchronize_with(release)) {
1053 set_bad_synchronization();
1056 /* Re-check all pending release sequences */
1057 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1058 /* Re-check act for mo_graph edges */
1059 work_queue->push_back(MOEdgeWorkEntry(acquire));
1061 /* propagate synchronization to later actions */
1062 action_list_t::reverse_iterator rit = action_trace->rbegin();
1063 for (; (*rit) != acquire; rit++) {
1064 ModelAction *propagate = *rit;
1065 if (acquire->happens_before(propagate)) {
1066 propagate->synchronize_with(acquire);
1067 /* Re-check 'propagate' for mo_graph edges */
1068 work_queue->push_back(MOEdgeWorkEntry(propagate));
1072 /* Break release sequence with new edges:
1073 * release --mo--> write --mo--> rf */
1074 mo_graph->addEdge(release, write);
1075 mo_graph->addEdge(write, rf);
1078 /* See if we have realized a data race */
1083 * Initialize the current action by performing one or more of the following
1084 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1085 * in the NodeStack, manipulating backtracking sets, allocating and
1086 * initializing clock vectors, and computing the promises to fulfill.
1088 * @param curr The current action, as passed from the user context; may be
1089 * freed/invalidated after the execution of this function, with a different
1090 * action "returned" its place (pass-by-reference)
1091 * @return True if curr is a newly-explored action; false otherwise
1093 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1095 ModelAction *newcurr;
1097 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1098 newcurr = process_rmw(*curr);
1101 if (newcurr->is_rmw())
1102 compute_promises(newcurr);
1108 (*curr)->set_seq_number(get_next_seq_num());
1110 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1112 /* First restore type and order in case of RMW operation */
1113 if ((*curr)->is_rmwr())
1114 newcurr->copy_typeandorder(*curr);
1116 ASSERT((*curr)->get_location() == newcurr->get_location());
1117 newcurr->copy_from_new(*curr);
1119 /* Discard duplicate ModelAction; use action from NodeStack */
1122 /* Always compute new clock vector */
1123 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1126 return false; /* Action was explored previously */
1130 /* Always compute new clock vector */
1131 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1133 /* Assign most recent release fence */
1134 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1137 * Perform one-time actions when pushing new ModelAction onto
1140 if (newcurr->is_write())
1141 compute_promises(newcurr);
1142 else if (newcurr->is_relseq_fixup())
1143 compute_relseq_breakwrites(newcurr);
1144 else if (newcurr->is_wait())
1145 newcurr->get_node()->set_misc_max(2);
1146 else if (newcurr->is_notify_one()) {
1147 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1149 return true; /* This was a new ModelAction */
1154 * @brief Establish reads-from relation between two actions
1156 * Perform basic operations involved with establishing a concrete rf relation,
1157 * including setting the ModelAction data and checking for release sequences.
1159 * @param act The action that is reading (must be a read)
1160 * @param rf The action from which we are reading (must be a write)
1162 * @return True if this read established synchronization
1164 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1166 act->set_read_from(rf);
1167 if (rf != NULL && act->is_acquire()) {
1168 rel_heads_list_t release_heads;
1169 get_release_seq_heads(act, act, &release_heads);
1170 int num_heads = release_heads.size();
1171 for (unsigned int i = 0; i < release_heads.size(); i++)
1172 if (!act->synchronize_with(release_heads[i])) {
1173 set_bad_synchronization();
1176 return num_heads > 0;
1182 * @brief Check whether a model action is enabled.
1184 * Checks whether a lock or join operation would be successful (i.e., is the
1185 * lock already locked, or is the joined thread already complete). If not, put
1186 * the action in a waiter list.
1188 * @param curr is the ModelAction to check whether it is enabled.
1189 * @return a bool that indicates whether the action is enabled.
1191 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1192 if (curr->is_lock()) {
1193 std::mutex *lock = (std::mutex *)curr->get_location();
1194 struct std::mutex_state *state = lock->get_state();
1195 if (state->islocked) {
1196 //Stick the action in the appropriate waiting queue
1197 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1200 } else if (curr->get_type() == THREAD_JOIN) {
1201 Thread *blocking = (Thread *)curr->get_location();
1202 if (!blocking->is_complete()) {
1203 blocking->push_wait_list(curr);
1212 * Stores the ModelAction for the current thread action. Call this
1213 * immediately before switching from user- to system-context to pass
1214 * data between them.
1215 * @param act The ModelAction created by the user-thread action
1217 void ModelChecker::set_current_action(ModelAction *act) {
1218 priv->current_action = act;
1222 * This is the heart of the model checker routine. It performs model-checking
1223 * actions corresponding to a given "current action." Among other processes, it
1224 * calculates reads-from relationships, updates synchronization clock vectors,
1225 * forms a memory_order constraints graph, and handles replay/backtrack
1226 * execution when running permutations of previously-observed executions.
1228 * @param curr The current action to process
1229 * @return The ModelAction that is actually executed; may be different than
1230 * curr; may be NULL, if the current action is not enabled to run
1232 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1235 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1237 if (!check_action_enabled(curr)) {
1238 /* Make the execution look like we chose to run this action
1239 * much later, when a lock/join can succeed */
1240 get_thread(curr)->set_pending(curr);
1241 scheduler->sleep(get_thread(curr));
1245 bool newly_explored = initialize_curr_action(&curr);
1251 wake_up_sleeping_actions(curr);
1253 /* Add the action to lists before any other model-checking tasks */
1254 if (!second_part_of_rmw)
1255 add_action_to_lists(curr);
1257 /* Build may_read_from set for newly-created actions */
1258 if (newly_explored && curr->is_read())
1259 build_reads_from_past(curr);
1261 /* Initialize work_queue with the "current action" work */
1262 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1263 while (!work_queue.empty() && !has_asserted()) {
1264 WorkQueueEntry work = work_queue.front();
1265 work_queue.pop_front();
1267 switch (work.type) {
1268 case WORK_CHECK_CURR_ACTION: {
1269 ModelAction *act = work.action;
1270 bool update = false; /* update this location's release seq's */
1271 bool update_all = false; /* update all release seq's */
1273 if (process_thread_action(curr))
1276 if (act->is_read() && process_read(act, second_part_of_rmw))
1279 if (act->is_write() && process_write(act))
1282 if (act->is_fence() && process_fence(act))
1285 if (act->is_mutex_op() && process_mutex(act))
1288 if (act->is_relseq_fixup())
1289 process_relseq_fixup(curr, &work_queue);
1292 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1294 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1297 case WORK_CHECK_RELEASE_SEQ:
1298 resolve_release_sequences(work.location, &work_queue);
1300 case WORK_CHECK_MO_EDGES: {
1301 /** @todo Complete verification of work_queue */
1302 ModelAction *act = work.action;
1303 bool updated = false;
1305 if (act->is_read()) {
1306 const ModelAction *rf = act->get_reads_from();
1307 if (rf != NULL && r_modification_order(act, rf))
1310 if (act->is_write()) {
1311 if (w_modification_order(act))
1314 mo_graph->commitChanges();
1317 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1326 check_curr_backtracking(curr);
1327 set_backtracking(curr);
1331 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1333 Node *currnode = curr->get_node();
1334 Node *parnode = currnode->get_parent();
1336 if ((parnode && !parnode->backtrack_empty()) ||
1337 !currnode->misc_empty() ||
1338 !currnode->read_from_empty() ||
1339 !currnode->future_value_empty() ||
1340 !currnode->promise_empty() ||
1341 !currnode->relseq_break_empty()) {
1342 set_latest_backtrack(curr);
1346 bool ModelChecker::promises_expired() const
1348 for (unsigned int i = 0; i < promises->size(); i++) {
1349 Promise *promise = (*promises)[i];
1350 if (promise->get_expiration() < priv->used_sequence_numbers)
1357 * This is the strongest feasibility check available.
1358 * @return whether the current trace (partial or complete) must be a prefix of
1361 bool ModelChecker::isfeasibleprefix() const
1363 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1367 * Print disagnostic information about an infeasible execution
1368 * @param prefix A string to prefix the output with; if NULL, then a default
1369 * message prefix will be provided
1371 void ModelChecker::print_infeasibility(const char *prefix) const
1375 if (mo_graph->checkForCycles())
1376 ptr += sprintf(ptr, "[mo cycle]");
1377 if (priv->failed_promise)
1378 ptr += sprintf(ptr, "[failed promise]");
1379 if (priv->too_many_reads)
1380 ptr += sprintf(ptr, "[too many reads]");
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->failed_promise ||
1410 priv->too_many_reads ||
1411 priv->bad_synchronization ||
1415 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1416 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1417 ModelAction *lastread = get_last_action(act->get_tid());
1418 lastread->process_rmw(act);
1419 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1420 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1421 mo_graph->commitChanges();
1427 * Checks whether a thread has read from the same write for too many times
1428 * without seeing the effects of a later write.
1431 * 1) there must a different write that we could read from that would satisfy the modification order,
1432 * 2) we must have read from the same value in excess of maxreads times, and
1433 * 3) that other write must have been in the reads_from set for maxreads times.
1435 * If so, we decide that the execution is no longer feasible.
1437 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1439 if (params.maxreads != 0) {
1440 if (curr->get_node()->get_read_from_size() <= 1)
1442 //Must make sure that execution is currently feasible... We could
1443 //accidentally clear by rolling back
1444 if (is_infeasible())
1446 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1447 int tid = id_to_int(curr->get_tid());
1450 if ((int)thrd_lists->size() <= tid)
1452 action_list_t *list = &(*thrd_lists)[tid];
1454 action_list_t::reverse_iterator rit = list->rbegin();
1455 /* Skip past curr */
1456 for (; (*rit) != curr; rit++)
1458 /* go past curr now */
1461 action_list_t::reverse_iterator ritcopy = rit;
1462 //See if we have enough reads from the same value
1464 for (; count < params.maxreads; rit++, count++) {
1465 if (rit == list->rend())
1467 ModelAction *act = *rit;
1468 if (!act->is_read())
1471 if (act->get_reads_from() != rf)
1473 if (act->get_node()->get_read_from_size() <= 1)
1476 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1478 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1480 /* Need a different write */
1484 /* Test to see whether this is a feasible write to read from */
1485 mo_graph->startChanges();
1486 r_modification_order(curr, write);
1487 bool feasiblereadfrom = !is_infeasible();
1488 mo_graph->rollbackChanges();
1490 if (!feasiblereadfrom)
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 mo_graph->addEdge(act, rf);
1573 /* C++, Section 29.3 statement 4 */
1574 else if (act->is_seqcst() && last_sc_fence_local &&
1575 *act < *last_sc_fence_local) {
1576 mo_graph->addEdge(act, rf);
1580 /* C++, Section 29.3 statement 6 */
1581 else if (last_sc_fence_thread_before &&
1582 *act < *last_sc_fence_thread_before) {
1583 mo_graph->addEdge(act, rf);
1590 * Include at most one act per-thread that "happens
1591 * before" curr. Don't consider reflexively.
1593 if (act->happens_before(curr) && act != curr) {
1594 if (act->is_write()) {
1595 if (!act->equals(rf)) {
1596 mo_graph->addEdge(act, rf);
1600 const ModelAction *prevreadfrom = act->get_reads_from();
1601 //if the previous read is unresolved, keep going...
1602 if (prevreadfrom == NULL)
1605 if (!prevreadfrom->equals(rf)) {
1606 mo_graph->addEdge(prevreadfrom, rf);
1618 /** This method fixes up the modification order when we resolve a
1619 * promises. The basic problem is that actions that occur after the
1620 * read curr could not property add items to the modification order
1623 * So for each thread, we find the earliest item that happens after
1624 * the read curr. This is the item we have to fix up with additional
1625 * constraints. If that action is write, we add a MO edge between
1626 * the Action rf and that action. If the action is a read, we add a
1627 * MO edge between the Action rf, and whatever the read accessed.
1629 * @param curr is the read ModelAction that we are fixing up MO edges for.
1630 * @param rf is the write ModelAction that curr reads from.
1633 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1635 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1637 ASSERT(curr->is_read());
1639 /* Iterate over all threads */
1640 for (i = 0; i < thrd_lists->size(); i++) {
1641 /* Iterate over actions in thread, starting from most recent */
1642 action_list_t *list = &(*thrd_lists)[i];
1643 action_list_t::reverse_iterator rit;
1644 ModelAction *lastact = NULL;
1646 /* Find last action that happens after curr that is either not curr or a rmw */
1647 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1648 ModelAction *act = *rit;
1649 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1655 /* Include at most one act per-thread that "happens before" curr */
1656 if (lastact != NULL) {
1657 if (lastact == curr) {
1658 //Case 1: The resolved read is a RMW, and we need to make sure
1659 //that the write portion of the RMW mod order after rf
1661 mo_graph->addEdge(rf, lastact);
1662 } else if (lastact->is_read()) {
1663 //Case 2: The resolved read is a normal read and the next
1664 //operation is a read, and we need to make sure the value read
1665 //is mod ordered after rf
1667 const ModelAction *postreadfrom = lastact->get_reads_from();
1668 if (postreadfrom != NULL && rf != postreadfrom)
1669 mo_graph->addEdge(rf, postreadfrom);
1671 //Case 3: The resolved read is a normal read and the next
1672 //operation is a write, and we need to make sure that the
1673 //write is mod ordered after rf
1675 mo_graph->addEdge(rf, lastact);
1683 * Updates the mo_graph with the constraints imposed from the current write.
1685 * Basic idea is the following: Go through each other thread and find
1686 * the lastest action that happened before our write. Two cases:
1688 * (1) The action is a write => that write must occur before
1691 * (2) The action is a read => the write that that action read from
1692 * must occur before the current write.
1694 * This method also handles two other issues:
1696 * (I) Sequential Consistency: Making sure that if the current write is
1697 * seq_cst, that it occurs after the previous seq_cst write.
1699 * (II) Sending the write back to non-synchronizing reads.
1701 * @param curr The current action. Must be a write.
1702 * @return True if modification order edges were added; false otherwise
1704 bool ModelChecker::w_modification_order(ModelAction *curr)
1706 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1709 ASSERT(curr->is_write());
1711 if (curr->is_seqcst()) {
1712 /* We have to at least see the last sequentially consistent write,
1713 so we are initialized. */
1714 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1715 if (last_seq_cst != NULL) {
1716 mo_graph->addEdge(last_seq_cst, curr);
1721 /* Last SC fence in the current thread */
1722 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1724 /* Iterate over all threads */
1725 for (i = 0; i < thrd_lists->size(); i++) {
1726 /* Last SC fence in thread i, before last SC fence in current thread */
1727 ModelAction *last_sc_fence_thread_before = NULL;
1728 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1729 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1731 /* Iterate over actions in thread, starting from most recent */
1732 action_list_t *list = &(*thrd_lists)[i];
1733 action_list_t::reverse_iterator rit;
1734 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1735 ModelAction *act = *rit;
1738 * 1) If RMW and it actually read from something, then we
1739 * already have all relevant edges, so just skip to next
1742 * 2) If RMW and it didn't read from anything, we should
1743 * whatever edge we can get to speed up convergence.
1745 * 3) If normal write, we need to look at earlier actions, so
1746 * continue processing list.
1748 if (curr->is_rmw()) {
1749 if (curr->get_reads_from() != NULL)
1757 /* C++, Section 29.3 statement 7 */
1758 if (last_sc_fence_thread_before && act->is_write() &&
1759 *act < *last_sc_fence_thread_before) {
1760 mo_graph->addEdge(act, curr);
1766 * Include at most one act per-thread that "happens
1769 if (act->happens_before(curr)) {
1771 * Note: if act is RMW, just add edge:
1773 * The following edge should be handled elsewhere:
1774 * readfrom(act) --mo--> act
1776 if (act->is_write())
1777 mo_graph->addEdge(act, curr);
1778 else if (act->is_read()) {
1779 //if previous read accessed a null, just keep going
1780 if (act->get_reads_from() == NULL)
1782 mo_graph->addEdge(act->get_reads_from(), curr);
1786 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1787 !act->same_thread(curr)) {
1788 /* We have an action that:
1789 (1) did not happen before us
1790 (2) is a read and we are a write
1791 (3) cannot synchronize with us
1792 (4) is in a different thread
1794 that read could potentially read from our write. Note that
1795 these checks are overly conservative at this point, we'll
1796 do more checks before actually removing the
1800 if (thin_air_constraint_may_allow(curr, act)) {
1801 if (!is_infeasible())
1802 futurevalues->push_back(PendingFutureValue(curr, act));
1803 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1804 add_future_value(curr, act);
1813 /** Arbitrary reads from the future are not allowed. Section 29.3
1814 * part 9 places some constraints. This method checks one result of constraint
1815 * constraint. Others require compiler support. */
1816 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1818 if (!writer->is_rmw())
1821 if (!reader->is_rmw())
1824 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1825 if (search == reader)
1827 if (search->get_tid() == reader->get_tid() &&
1828 search->happens_before(reader))
1836 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1837 * some constraints. This method checks one the following constraint (others
1838 * require compiler support):
1840 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1842 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1844 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1846 /* Iterate over all threads */
1847 for (i = 0; i < thrd_lists->size(); i++) {
1848 const ModelAction *write_after_read = NULL;
1850 /* Iterate over actions in thread, starting from most recent */
1851 action_list_t *list = &(*thrd_lists)[i];
1852 action_list_t::reverse_iterator rit;
1853 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1854 ModelAction *act = *rit;
1856 /* Don't disallow due to act == reader */
1857 if (!reader->happens_before(act) || reader == act)
1859 else if (act->is_write())
1860 write_after_read = act;
1861 else if (act->is_read() && act->get_reads_from() != NULL)
1862 write_after_read = act->get_reads_from();
1865 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1872 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1873 * The ModelAction under consideration is expected to be taking part in
1874 * release/acquire synchronization as an object of the "reads from" relation.
1875 * Note that this can only provide release sequence support for RMW chains
1876 * which do not read from the future, as those actions cannot be traced until
1877 * their "promise" is fulfilled. Similarly, we may not even establish the
1878 * presence of a release sequence with certainty, as some modification order
1879 * constraints may be decided further in the future. Thus, this function
1880 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1881 * and a boolean representing certainty.
1883 * @param rf The action that might be part of a release sequence. Must be a
1885 * @param release_heads A pass-by-reference style return parameter. After
1886 * execution of this function, release_heads will contain the heads of all the
1887 * relevant release sequences, if any exists with certainty
1888 * @param pending A pass-by-reference style return parameter which is only used
1889 * when returning false (i.e., uncertain). Returns most information regarding
1890 * an uncertain release sequence, including any write operations that might
1891 * break the sequence.
1892 * @return true, if the ModelChecker is certain that release_heads is complete;
1895 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1896 rel_heads_list_t *release_heads,
1897 struct release_seq *pending) const
1899 /* Only check for release sequences if there are no cycles */
1900 if (mo_graph->checkForCycles())
1904 ASSERT(rf->is_write());
1906 if (rf->is_release())
1907 release_heads->push_back(rf);
1908 else if (rf->get_last_fence_release())
1909 release_heads->push_back(rf->get_last_fence_release());
1911 break; /* End of RMW chain */
1913 /** @todo Need to be smarter here... In the linux lock
1914 * example, this will run to the beginning of the program for
1916 /** @todo The way to be smarter here is to keep going until 1
1917 * thread has a release preceded by an acquire and you've seen
1920 /* acq_rel RMW is a sufficient stopping condition */
1921 if (rf->is_acquire() && rf->is_release())
1922 return true; /* complete */
1924 rf = rf->get_reads_from();
1927 /* read from future: need to settle this later */
1929 return false; /* incomplete */
1932 if (rf->is_release())
1933 return true; /* complete */
1935 /* else relaxed write
1936 * - check for fence-release in the same thread (29.8, stmt. 3)
1937 * - check modification order for contiguous subsequence
1938 * -> rf must be same thread as release */
1940 const ModelAction *fence_release = rf->get_last_fence_release();
1941 /* Synchronize with a fence-release unconditionally; we don't need to
1942 * find any more "contiguous subsequence..." for it */
1944 release_heads->push_back(fence_release);
1946 int tid = id_to_int(rf->get_tid());
1947 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1948 action_list_t *list = &(*thrd_lists)[tid];
1949 action_list_t::const_reverse_iterator rit;
1951 /* Find rf in the thread list */
1952 rit = std::find(list->rbegin(), list->rend(), rf);
1953 ASSERT(rit != list->rend());
1955 /* Find the last {write,fence}-release */
1956 for (; rit != list->rend(); rit++) {
1957 if (fence_release && *(*rit) < *fence_release)
1959 if ((*rit)->is_release())
1962 if (rit == list->rend()) {
1963 /* No write-release in this thread */
1964 return true; /* complete */
1965 } else if (fence_release && *(*rit) < *fence_release) {
1966 /* The fence-release is more recent (and so, "stronger") than
1967 * the most recent write-release */
1968 return true; /* complete */
1969 } /* else, need to establish contiguous release sequence */
1970 ModelAction *release = *rit;
1972 ASSERT(rf->same_thread(release));
1974 pending->writes.clear();
1976 bool certain = true;
1977 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1978 if (id_to_int(rf->get_tid()) == (int)i)
1980 list = &(*thrd_lists)[i];
1982 /* Can we ensure no future writes from this thread may break
1983 * the release seq? */
1984 bool future_ordered = false;
1986 ModelAction *last = get_last_action(int_to_id(i));
1987 Thread *th = get_thread(int_to_id(i));
1988 if ((last && rf->happens_before(last)) ||
1991 future_ordered = true;
1993 ASSERT(!th->is_model_thread() || future_ordered);
1995 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1996 const ModelAction *act = *rit;
1997 /* Reach synchronization -> this thread is complete */
1998 if (act->happens_before(release))
2000 if (rf->happens_before(act)) {
2001 future_ordered = true;
2005 /* Only non-RMW writes can break release sequences */
2006 if (!act->is_write() || act->is_rmw())
2009 /* Check modification order */
2010 if (mo_graph->checkReachable(rf, act)) {
2011 /* rf --mo--> act */
2012 future_ordered = true;
2015 if (mo_graph->checkReachable(act, release))
2016 /* act --mo--> release */
2018 if (mo_graph->checkReachable(release, act) &&
2019 mo_graph->checkReachable(act, rf)) {
2020 /* release --mo-> act --mo--> rf */
2021 return true; /* complete */
2023 /* act may break release sequence */
2024 pending->writes.push_back(act);
2027 if (!future_ordered)
2028 certain = false; /* This thread is uncertain */
2032 release_heads->push_back(release);
2033 pending->writes.clear();
2035 pending->release = release;
2042 * An interface for getting the release sequence head(s) with which a
2043 * given ModelAction must synchronize. This function only returns a non-empty
2044 * result when it can locate a release sequence head with certainty. Otherwise,
2045 * it may mark the internal state of the ModelChecker so that it will handle
2046 * the release sequence at a later time, causing @a acquire to update its
2047 * synchronization at some later point in execution.
2049 * @param acquire The 'acquire' action that may synchronize with a release
2051 * @param read The read action that may read from a release sequence; this may
2052 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2053 * when 'acquire' is a fence-acquire)
2054 * @param release_heads A pass-by-reference return parameter. Will be filled
2055 * with the head(s) of the release sequence(s), if they exists with certainty.
2056 * @see ModelChecker::release_seq_heads
2058 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2059 ModelAction *read, rel_heads_list_t *release_heads)
2061 const ModelAction *rf = read->get_reads_from();
2062 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2063 sequence->acquire = acquire;
2064 sequence->read = read;
2066 if (!release_seq_heads(rf, release_heads, sequence)) {
2067 /* add act to 'lazy checking' list */
2068 pending_rel_seqs->push_back(sequence);
2070 snapshot_free(sequence);
2075 * Attempt to resolve all stashed operations that might synchronize with a
2076 * release sequence for a given location. This implements the "lazy" portion of
2077 * determining whether or not a release sequence was contiguous, since not all
2078 * modification order information is present at the time an action occurs.
2080 * @param location The location/object that should be checked for release
2081 * sequence resolutions. A NULL value means to check all locations.
2082 * @param work_queue The work queue to which to add work items as they are
2084 * @return True if any updates occurred (new synchronization, new mo_graph
2087 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2089 bool updated = false;
2090 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2091 while (it != pending_rel_seqs->end()) {
2092 struct release_seq *pending = *it;
2093 ModelAction *acquire = pending->acquire;
2094 const ModelAction *read = pending->read;
2096 /* Only resolve sequences on the given location, if provided */
2097 if (location && read->get_location() != location) {
2102 const ModelAction *rf = read->get_reads_from();
2103 rel_heads_list_t release_heads;
2105 complete = release_seq_heads(rf, &release_heads, pending);
2106 for (unsigned int i = 0; i < release_heads.size(); i++) {
2107 if (!acquire->has_synchronized_with(release_heads[i])) {
2108 if (acquire->synchronize_with(release_heads[i]))
2111 set_bad_synchronization();
2116 /* Re-check all pending release sequences */
2117 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2118 /* Re-check read-acquire for mo_graph edges */
2119 if (acquire->is_read())
2120 work_queue->push_back(MOEdgeWorkEntry(acquire));
2122 /* propagate synchronization to later actions */
2123 action_list_t::reverse_iterator rit = action_trace->rbegin();
2124 for (; (*rit) != acquire; rit++) {
2125 ModelAction *propagate = *rit;
2126 if (acquire->happens_before(propagate)) {
2127 propagate->synchronize_with(acquire);
2128 /* Re-check 'propagate' for mo_graph edges */
2129 work_queue->push_back(MOEdgeWorkEntry(propagate));
2134 it = pending_rel_seqs->erase(it);
2135 snapshot_free(pending);
2141 // If we resolved promises or data races, see if we have realized a data race.
2148 * Performs various bookkeeping operations for the current ModelAction. For
2149 * instance, adds action to the per-object, per-thread action vector and to the
2150 * action trace list of all thread actions.
2152 * @param act is the ModelAction to add.
2154 void ModelChecker::add_action_to_lists(ModelAction *act)
2156 int tid = id_to_int(act->get_tid());
2157 ModelAction *uninit = NULL;
2159 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2160 if (list->empty() && act->is_atomic_var()) {
2161 uninit = new_uninitialized_action(act->get_location());
2162 uninit_id = id_to_int(uninit->get_tid());
2163 list->push_back(uninit);
2165 list->push_back(act);
2167 action_trace->push_back(act);
2169 action_trace->push_front(uninit);
2171 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2172 if (tid >= (int)vec->size())
2173 vec->resize(priv->next_thread_id);
2174 (*vec)[tid].push_back(act);
2176 (*vec)[uninit_id].push_front(uninit);
2178 if ((int)thrd_last_action->size() <= tid)
2179 thrd_last_action->resize(get_num_threads());
2180 (*thrd_last_action)[tid] = act;
2182 (*thrd_last_action)[uninit_id] = uninit;
2184 if (act->is_fence() && act->is_release()) {
2185 if ((int)thrd_last_fence_release->size() <= tid)
2186 thrd_last_fence_release->resize(get_num_threads());
2187 (*thrd_last_fence_release)[tid] = act;
2190 if (act->is_wait()) {
2191 void *mutex_loc = (void *) act->get_value();
2192 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2194 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2195 if (tid >= (int)vec->size())
2196 vec->resize(priv->next_thread_id);
2197 (*vec)[tid].push_back(act);
2202 * @brief Get the last action performed by a particular Thread
2203 * @param tid The thread ID of the Thread in question
2204 * @return The last action in the thread
2206 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2208 int threadid = id_to_int(tid);
2209 if (threadid < (int)thrd_last_action->size())
2210 return (*thrd_last_action)[id_to_int(tid)];
2216 * @brief Get the last fence release performed by a particular Thread
2217 * @param tid The thread ID of the Thread in question
2218 * @return The last fence release in the thread, if one exists; NULL otherwise
2220 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2222 int threadid = id_to_int(tid);
2223 if (threadid < (int)thrd_last_fence_release->size())
2224 return (*thrd_last_fence_release)[id_to_int(tid)];
2230 * Gets the last memory_order_seq_cst write (in the total global sequence)
2231 * performed on a particular object (i.e., memory location), not including the
2233 * @param curr The current ModelAction; also denotes the object location to
2235 * @return The last seq_cst write
2237 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2239 void *location = curr->get_location();
2240 action_list_t *list = get_safe_ptr_action(obj_map, location);
2241 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2242 action_list_t::reverse_iterator rit;
2243 for (rit = list->rbegin(); rit != list->rend(); rit++)
2244 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2250 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2251 * performed in a particular thread, prior to a particular fence.
2252 * @param tid The ID of the thread to check
2253 * @param before_fence The fence from which to begin the search; if NULL, then
2254 * search for the most recent fence in the thread.
2255 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2257 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2259 /* All fences should have NULL location */
2260 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2261 action_list_t::reverse_iterator rit = list->rbegin();
2264 for (; rit != list->rend(); rit++)
2265 if (*rit == before_fence)
2268 ASSERT(*rit == before_fence);
2272 for (; rit != list->rend(); rit++)
2273 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2279 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2280 * location). This function identifies the mutex according to the current
2281 * action, which is presumed to perform on the same mutex.
2282 * @param curr The current ModelAction; also denotes the object location to
2284 * @return The last unlock operation
2286 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2288 void *location = curr->get_location();
2289 action_list_t *list = get_safe_ptr_action(obj_map, location);
2290 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2291 action_list_t::reverse_iterator rit;
2292 for (rit = list->rbegin(); rit != list->rend(); rit++)
2293 if ((*rit)->is_unlock() || (*rit)->is_wait())
2298 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2300 ModelAction *parent = get_last_action(tid);
2302 parent = get_thread(tid)->get_creation();
2307 * Returns the clock vector for a given thread.
2308 * @param tid The thread whose clock vector we want
2309 * @return Desired clock vector
2311 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2313 return get_parent_action(tid)->get_cv();
2317 * Resolve a set of Promises with a current write. The set is provided in the
2318 * Node corresponding to @a write.
2319 * @param write The ModelAction that is fulfilling Promises
2320 * @return True if promises were resolved; false otherwise
2322 bool ModelChecker::resolve_promises(ModelAction *write)
2324 bool resolved = false;
2325 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2327 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2328 Promise *promise = (*promises)[promise_index];
2329 if (write->get_node()->get_promise(i)) {
2330 ModelAction *read = promise->get_action();
2331 if (read->is_rmw()) {
2332 mo_graph->addRMWEdge(write, read);
2334 read_from(read, write);
2335 //First fix up the modification order for actions that happened
2337 r_modification_order(read, write);
2338 //Next fix up the modification order for actions that happened
2340 post_r_modification_order(read, write);
2341 //Make sure the promise's value matches the write's value
2342 ASSERT(promise->get_value() == write->get_value());
2345 promises->erase(promises->begin() + promise_index);
2346 actions_to_check.push_back(read);
2353 //Check whether reading these writes has made threads unable to
2356 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2357 ModelAction *read=actions_to_check[i];
2358 mo_check_promises(read->get_tid(), write, read);
2365 * Compute the set of promises that could potentially be satisfied by this
2366 * action. Note that the set computation actually appears in the Node, not in
2368 * @param curr The ModelAction that may satisfy promises
2370 void ModelChecker::compute_promises(ModelAction *curr)
2372 for (unsigned int i = 0; i < promises->size(); i++) {
2373 Promise *promise = (*promises)[i];
2374 const ModelAction *act = promise->get_action();
2375 if (!act->happens_before(curr) &&
2377 !act->could_synchronize_with(curr) &&
2378 !act->same_thread(curr) &&
2379 act->get_location() == curr->get_location() &&
2380 promise->get_value() == curr->get_value()) {
2381 curr->get_node()->set_promise(i, act->is_rmw());
2386 /** Checks promises in response to change in ClockVector Threads. */
2387 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2389 for (unsigned int i = 0; i < promises->size(); i++) {
2390 Promise *promise = (*promises)[i];
2391 const ModelAction *act = promise->get_action();
2392 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2393 merge_cv->synchronized_since(act)) {
2394 if (promise->eliminate_thread(tid)) {
2395 //Promise has failed
2396 priv->failed_promise = true;
2403 void ModelChecker::check_promises_thread_disabled()
2405 for (unsigned int i = 0; i < promises->size(); i++) {
2406 Promise *promise = (*promises)[i];
2407 if (promise->has_failed()) {
2408 priv->failed_promise = true;
2415 * @brief Checks promises in response to addition to modification order for
2420 * pthread is the thread that performed the read that created the promise
2422 * pread is the read that created the promise
2424 * pwrite is either the first write to same location as pread by
2425 * pthread that is sequenced after pread or the write read by the
2426 * first read to the same location as pread by pthread that is
2427 * sequenced after pread.
2429 * 1. If tid=pthread, then we check what other threads are reachable
2430 * through the mod order starting with pwrite. Those threads cannot
2431 * perform a write that will resolve the promise due to modification
2432 * order constraints.
2434 * 2. If the tid is not pthread, we check whether pwrite can reach the
2435 * action write through the modification order. If so, that thread
2436 * cannot perform a future write that will resolve the promise due to
2437 * modificatin order constraints.
2439 * @param tid The thread that either read from the model action write, or
2440 * actually did the model action write.
2442 * @param write The ModelAction representing the relevant write.
2443 * @param read The ModelAction that reads a promised write, or NULL otherwise.
2445 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write, const ModelAction *read)
2447 void *location = write->get_location();
2448 for (unsigned int i = 0; i < promises->size(); i++) {
2449 Promise *promise = (*promises)[i];
2450 const ModelAction *act = promise->get_action();
2452 // Is this promise on the same location?
2453 if (act->get_location() != location)
2456 // same thread as the promise
2457 if (act->get_tid() == tid) {
2458 // make sure that the reader of this write happens after the promise
2459 if ((read == NULL) || (promise->get_action()->happens_before(read))) {
2460 // do we have a pwrite for the promise, if not, set it
2461 if (promise->get_write() == NULL) {
2462 promise->set_write(write);
2463 // The pwrite cannot happen before the promise
2464 if (write->happens_before(act) && (write != act)) {
2465 priv->failed_promise = true;
2470 if (mo_graph->checkPromise(write, promise)) {
2471 priv->failed_promise = true;
2477 // Don't do any lookups twice for the same thread
2478 if (!promise->thread_is_available(tid))
2481 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2482 if (promise->eliminate_thread(tid)) {
2483 priv->failed_promise = true;
2491 * Compute the set of writes that may break the current pending release
2492 * sequence. This information is extracted from previou release sequence
2495 * @param curr The current ModelAction. Must be a release sequence fixup
2498 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2500 if (pending_rel_seqs->empty())
2503 struct release_seq *pending = pending_rel_seqs->back();
2504 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2505 const ModelAction *write = pending->writes[i];
2506 curr->get_node()->add_relseq_break(write);
2509 /* NULL means don't break the sequence; just synchronize */
2510 curr->get_node()->add_relseq_break(NULL);
2514 * Build up an initial set of all past writes that this 'read' action may read
2515 * from. This set is determined by the clock vector's "happens before"
2517 * @param curr is the current ModelAction that we are exploring; it must be a
2520 void ModelChecker::build_reads_from_past(ModelAction *curr)
2522 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2524 ASSERT(curr->is_read());
2526 ModelAction *last_sc_write = NULL;
2528 if (curr->is_seqcst())
2529 last_sc_write = get_last_seq_cst_write(curr);
2531 /* Iterate over all threads */
2532 for (i = 0; i < thrd_lists->size(); i++) {
2533 /* Iterate over actions in thread, starting from most recent */
2534 action_list_t *list = &(*thrd_lists)[i];
2535 action_list_t::reverse_iterator rit;
2536 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2537 ModelAction *act = *rit;
2539 /* Only consider 'write' actions */
2540 if (!act->is_write() || act == curr)
2543 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2544 bool allow_read = true;
2546 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2548 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2552 curr->get_node()->add_read_from(act);
2554 /* Include at most one act per-thread that "happens before" curr */
2555 if (act->happens_before(curr))
2560 if (DBG_ENABLED()) {
2561 model_print("Reached read action:\n");
2563 model_print("Printing may_read_from\n");
2564 curr->get_node()->print_may_read_from();
2565 model_print("End printing may_read_from\n");
2569 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2572 /* UNINIT actions don't have a Node, and they never sleep */
2573 if (write->is_uninitialized())
2575 Node *prevnode = write->get_node()->get_parent();
2577 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2578 if (write->is_release() && thread_sleep)
2580 if (!write->is_rmw()) {
2583 if (write->get_reads_from() == NULL)
2585 write = write->get_reads_from();
2590 * @brief Create a new action representing an uninitialized atomic
2591 * @param location The memory location of the atomic object
2592 * @return A pointer to a new ModelAction
2594 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2596 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2597 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2598 act->create_cv(NULL);
2602 static void print_list(action_list_t *list)
2604 action_list_t::iterator it;
2606 model_print("---------------------------------------------------------------------\n");
2608 unsigned int hash = 0;
2610 for (it = list->begin(); it != list->end(); it++) {
2612 hash = hash^(hash<<3)^((*it)->hash());
2614 model_print("HASH %u\n", hash);
2615 model_print("---------------------------------------------------------------------\n");
2618 #if SUPPORT_MOD_ORDER_DUMP
2619 void ModelChecker::dumpGraph(char *filename) const
2622 sprintf(buffer, "%s.dot", filename);
2623 FILE *file = fopen(buffer, "w");
2624 fprintf(file, "digraph %s {\n", filename);
2625 mo_graph->dumpNodes(file);
2626 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2628 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2629 ModelAction *action = *it;
2630 if (action->is_read()) {
2631 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2632 if (action->get_reads_from() != NULL)
2633 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2635 if (thread_array[action->get_tid()] != NULL) {
2636 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2639 thread_array[action->get_tid()] = action;
2641 fprintf(file, "}\n");
2642 model_free(thread_array);
2647 /** @brief Prints an execution trace summary. */
2648 void ModelChecker::print_summary() const
2650 #if SUPPORT_MOD_ORDER_DUMP
2651 char buffername[100];
2652 sprintf(buffername, "exec%04u", stats.num_total);
2653 mo_graph->dumpGraphToFile(buffername);
2654 sprintf(buffername, "graph%04u", stats.num_total);
2655 dumpGraph(buffername);
2658 model_print("Execution %d:", stats.num_total);
2659 if (isfeasibleprefix())
2662 print_infeasibility(" INFEASIBLE");
2663 print_list(action_trace);
2668 * Add a Thread to the system for the first time. Should only be called once
2670 * @param t The Thread to add
2672 void ModelChecker::add_thread(Thread *t)
2674 thread_map->put(id_to_int(t->get_id()), t);
2675 scheduler->add_thread(t);
2679 * Removes a thread from the scheduler.
2680 * @param the thread to remove.
2682 void ModelChecker::remove_thread(Thread *t)
2684 scheduler->remove_thread(t);
2688 * @brief Get a Thread reference by its ID
2689 * @param tid The Thread's ID
2690 * @return A Thread reference
2692 Thread * ModelChecker::get_thread(thread_id_t tid) const
2694 return thread_map->get(id_to_int(tid));
2698 * @brief Get a reference to the Thread in which a ModelAction was executed
2699 * @param act The ModelAction
2700 * @return A Thread reference
2702 Thread * ModelChecker::get_thread(const ModelAction *act) const
2704 return get_thread(act->get_tid());
2708 * @brief Check if a Thread is currently enabled
2709 * @param t The Thread to check
2710 * @return True if the Thread is currently enabled
2712 bool ModelChecker::is_enabled(Thread *t) const
2714 return scheduler->is_enabled(t);
2718 * @brief Check if a Thread is currently enabled
2719 * @param tid The ID of the Thread to check
2720 * @return True if the Thread is currently enabled
2722 bool ModelChecker::is_enabled(thread_id_t tid) const
2724 return scheduler->is_enabled(tid);
2728 * Switch from a user-context to the "master thread" context (a.k.a. system
2729 * context). This switch is made with the intention of exploring a particular
2730 * model-checking action (described by a ModelAction object). Must be called
2731 * from a user-thread context.
2733 * @param act The current action that will be explored. May be NULL only if
2734 * trace is exiting via an assertion (see ModelChecker::set_assert and
2735 * ModelChecker::has_asserted).
2736 * @return Return the value returned by the current action
2738 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2741 Thread *old = thread_current();
2742 set_current_action(act);
2743 old->set_state(THREAD_READY);
2744 if (Thread::swap(old, &system_context) < 0) {
2745 perror("swap threads");
2748 return old->get_return_value();
2752 * Takes the next step in the execution, if possible.
2753 * @param curr The current step to take
2754 * @return Returns true (success) if a step was taken and false otherwise.
2756 bool ModelChecker::take_step(ModelAction *curr)
2761 Thread *curr_thrd = get_thread(curr);
2762 ASSERT(curr_thrd->get_state() == THREAD_READY);
2764 curr = check_current_action(curr);
2766 /* Infeasible -> don't take any more steps */
2767 if (is_infeasible())
2769 else if (isfeasibleprefix() && have_bug_reports()) {
2774 if (params.bound != 0)
2775 if (priv->used_sequence_numbers > params.bound)
2778 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2779 scheduler->remove_thread(curr_thrd);
2781 Thread *next_thrd = get_next_thread(curr);
2782 next_thrd = scheduler->next_thread(next_thrd);
2784 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2785 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2788 * Launch end-of-execution release sequence fixups only when there are:
2790 * (1) no more user threads to run (or when execution replay chooses
2791 * the 'model_thread')
2792 * (2) pending release sequences
2793 * (3) pending assertions (i.e., data races)
2794 * (4) no pending promises
2796 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2797 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2798 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2799 pending_rel_seqs->size());
2800 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2801 std::memory_order_seq_cst, NULL, VALUE_NONE,
2803 set_current_action(fixup);
2807 /* next_thrd == NULL -> don't take any more steps */
2811 next_thrd->set_state(THREAD_RUNNING);
2813 if (next_thrd->get_pending() != NULL) {
2814 /* restart a pending action */
2815 set_current_action(next_thrd->get_pending());
2816 next_thrd->set_pending(NULL);
2817 next_thrd->set_state(THREAD_READY);
2821 /* Return false only if swap fails with an error */
2822 return (Thread::swap(&system_context, next_thrd) == 0);
2825 /** Wrapper to run the user's main function, with appropriate arguments */
2826 void user_main_wrapper(void *)
2828 user_main(model->params.argc, model->params.argv);
2831 /** @brief Run ModelChecker for the user program */
2832 void ModelChecker::run()
2836 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2840 /* Run user thread up to its first action */
2841 scheduler->next_thread(t);
2842 Thread::swap(&system_context, t);
2844 /* Wait for all threads to complete */
2845 while (take_step(priv->current_action));
2846 } while (next_execution());