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();
739 curr->set_value(fv.value);
740 curr->set_read_from(NULL);
741 promises->push_back(new Promise(curr, fv));
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->checkForRMWViolation())
1376 ptr += sprintf(ptr, "[RMW atomicity]");
1377 if (mo_graph->checkForCycles())
1378 ptr += sprintf(ptr, "[mo cycle]");
1379 if (priv->failed_promise)
1380 ptr += sprintf(ptr, "[failed promise]");
1381 if (priv->too_many_reads)
1382 ptr += sprintf(ptr, "[too many reads]");
1383 if (priv->bad_synchronization)
1384 ptr += sprintf(ptr, "[bad sw ordering]");
1385 if (promises_expired())
1386 ptr += sprintf(ptr, "[promise expired]");
1387 if (promises->size() != 0)
1388 ptr += sprintf(ptr, "[unresolved promise]");
1390 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1394 * Returns whether the current completed trace is feasible, except for pending
1395 * release sequences.
1397 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1399 return !is_infeasible() && promises->size() == 0;
1403 * Check if the current partial trace is infeasible. Does not check any
1404 * end-of-execution flags, which might rule out the execution. Thus, this is
1405 * useful only for ruling an execution as infeasible.
1406 * @return whether the current partial trace is infeasible.
1408 bool ModelChecker::is_infeasible() const
1410 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1414 * Check If the current partial trace is infeasible, while ignoring
1415 * infeasibility related to 2 RMW's reading from the same store. It does not
1416 * check end-of-execution feasibility.
1417 * @see ModelChecker::is_infeasible
1418 * @return whether the current partial trace is infeasible, ignoring multiple
1419 * RMWs reading from the same store.
1421 bool ModelChecker::is_infeasible_ignoreRMW() const
1423 return mo_graph->checkForCycles() || priv->failed_promise ||
1424 priv->too_many_reads || 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() && lastread->get_reads_from() != NULL) {
1433 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1434 mo_graph->commitChanges();
1440 * Checks whether a thread has read from the same write for too many times
1441 * without seeing the effects of a later write.
1444 * 1) there must a different write that we could read from that would satisfy the modification order,
1445 * 2) we must have read from the same value in excess of maxreads times, and
1446 * 3) that other write must have been in the reads_from set for maxreads times.
1448 * If so, we decide that the execution is no longer feasible.
1450 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1452 if (params.maxreads != 0) {
1453 if (curr->get_node()->get_read_from_size() <= 1)
1455 //Must make sure that execution is currently feasible... We could
1456 //accidentally clear by rolling back
1457 if (is_infeasible())
1459 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1460 int tid = id_to_int(curr->get_tid());
1463 if ((int)thrd_lists->size() <= tid)
1465 action_list_t *list = &(*thrd_lists)[tid];
1467 action_list_t::reverse_iterator rit = list->rbegin();
1468 /* Skip past curr */
1469 for (; (*rit) != curr; rit++)
1471 /* go past curr now */
1474 action_list_t::reverse_iterator ritcopy = rit;
1475 //See if we have enough reads from the same value
1477 for (; count < params.maxreads; rit++, count++) {
1478 if (rit == list->rend())
1480 ModelAction *act = *rit;
1481 if (!act->is_read())
1484 if (act->get_reads_from() != rf)
1486 if (act->get_node()->get_read_from_size() <= 1)
1489 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1491 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1493 /* Need a different write */
1497 /* Test to see whether this is a feasible write to read from */
1498 mo_graph->startChanges();
1499 r_modification_order(curr, write);
1500 bool feasiblereadfrom = !is_infeasible();
1501 mo_graph->rollbackChanges();
1503 if (!feasiblereadfrom)
1507 bool feasiblewrite = true;
1508 //new we need to see if this write works for everyone
1510 for (int loop = count; loop > 0; loop--, rit++) {
1511 ModelAction *act = *rit;
1512 bool foundvalue = false;
1513 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1514 if (act->get_node()->get_read_from_at(j) == write) {
1520 feasiblewrite = false;
1524 if (feasiblewrite) {
1525 priv->too_many_reads = true;
1533 * Updates the mo_graph with the constraints imposed from the current
1536 * Basic idea is the following: Go through each other thread and find
1537 * the lastest action that happened before our read. Two cases:
1539 * (1) The action is a write => that write must either occur before
1540 * the write we read from or be the write we read from.
1542 * (2) The action is a read => the write that that action read from
1543 * must occur before the write we read from or be the same write.
1545 * @param curr The current action. Must be a read.
1546 * @param rf The action that curr reads from. Must be a write.
1547 * @return True if modification order edges were added; false otherwise
1549 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *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 != 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 mo_graph->addEdge(act, rf);
1585 /* C++, Section 29.3 statement 4 */
1586 else if (act->is_seqcst() && last_sc_fence_local &&
1587 *act < *last_sc_fence_local) {
1588 mo_graph->addEdge(act, rf);
1592 /* C++, Section 29.3 statement 6 */
1593 else if (last_sc_fence_thread_before &&
1594 *act < *last_sc_fence_thread_before) {
1595 mo_graph->addEdge(act, rf);
1602 * Include at most one act per-thread that "happens
1603 * before" curr. Don't consider reflexively.
1605 if (act->happens_before(curr) && act != curr) {
1606 if (act->is_write()) {
1608 mo_graph->addEdge(act, rf);
1612 const ModelAction *prevreadfrom = act->get_reads_from();
1613 //if the previous read is unresolved, keep going...
1614 if (prevreadfrom == NULL)
1617 if (rf != prevreadfrom) {
1618 mo_graph->addEdge(prevreadfrom, rf);
1630 /** This method fixes up the modification order when we resolve a
1631 * promises. The basic problem is that actions that occur after the
1632 * read curr could not property add items to the modification order
1635 * So for each thread, we find the earliest item that happens after
1636 * the read curr. This is the item we have to fix up with additional
1637 * constraints. If that action is write, we add a MO edge between
1638 * the Action rf and that action. If the action is a read, we add a
1639 * MO edge between the Action rf, and whatever the read accessed.
1641 * @param curr is the read ModelAction that we are fixing up MO edges for.
1642 * @param rf is the write ModelAction that curr reads from.
1645 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1647 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1649 ASSERT(curr->is_read());
1651 /* Iterate over all threads */
1652 for (i = 0; i < thrd_lists->size(); i++) {
1653 /* Iterate over actions in thread, starting from most recent */
1654 action_list_t *list = &(*thrd_lists)[i];
1655 action_list_t::reverse_iterator rit;
1656 ModelAction *lastact = NULL;
1658 /* Find last action that happens after curr that is either not curr or a rmw */
1659 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1660 ModelAction *act = *rit;
1661 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1667 /* Include at most one act per-thread that "happens before" curr */
1668 if (lastact != NULL) {
1669 if (lastact == curr) {
1670 //Case 1: The resolved read is a RMW, and we need to make sure
1671 //that the write portion of the RMW mod order after rf
1673 mo_graph->addEdge(rf, lastact);
1674 } else if (lastact->is_read()) {
1675 //Case 2: The resolved read is a normal read and the next
1676 //operation is a read, and we need to make sure the value read
1677 //is mod ordered after rf
1679 const ModelAction *postreadfrom = lastact->get_reads_from();
1680 if (postreadfrom != NULL && rf != postreadfrom)
1681 mo_graph->addEdge(rf, postreadfrom);
1683 //Case 3: The resolved read is a normal read and the next
1684 //operation is a write, and we need to make sure that the
1685 //write is mod ordered after rf
1687 mo_graph->addEdge(rf, lastact);
1695 * Updates the mo_graph with the constraints imposed from the current write.
1697 * Basic idea is the following: Go through each other thread and find
1698 * the lastest action that happened before our write. Two cases:
1700 * (1) The action is a write => that write must occur before
1703 * (2) The action is a read => the write that that action read from
1704 * must occur before the current write.
1706 * This method also handles two other issues:
1708 * (I) Sequential Consistency: Making sure that if the current write is
1709 * seq_cst, that it occurs after the previous seq_cst write.
1711 * (II) Sending the write back to non-synchronizing reads.
1713 * @param curr The current action. Must be a write.
1714 * @return True if modification order edges were added; false otherwise
1716 bool ModelChecker::w_modification_order(ModelAction *curr)
1718 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1721 ASSERT(curr->is_write());
1723 if (curr->is_seqcst()) {
1724 /* We have to at least see the last sequentially consistent write,
1725 so we are initialized. */
1726 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1727 if (last_seq_cst != NULL) {
1728 mo_graph->addEdge(last_seq_cst, curr);
1733 /* Last SC fence in the current thread */
1734 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1736 /* Iterate over all threads */
1737 for (i = 0; i < thrd_lists->size(); i++) {
1738 /* Last SC fence in thread i, before last SC fence in current thread */
1739 ModelAction *last_sc_fence_thread_before = NULL;
1740 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1741 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1743 /* Iterate over actions in thread, starting from most recent */
1744 action_list_t *list = &(*thrd_lists)[i];
1745 action_list_t::reverse_iterator rit;
1746 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1747 ModelAction *act = *rit;
1750 * 1) If RMW and it actually read from something, then we
1751 * already have all relevant edges, so just skip to next
1754 * 2) If RMW and it didn't read from anything, we should
1755 * whatever edge we can get to speed up convergence.
1757 * 3) If normal write, we need to look at earlier actions, so
1758 * continue processing list.
1760 if (curr->is_rmw()) {
1761 if (curr->get_reads_from() != NULL)
1769 /* C++, Section 29.3 statement 7 */
1770 if (last_sc_fence_thread_before && act->is_write() &&
1771 *act < *last_sc_fence_thread_before) {
1772 mo_graph->addEdge(act, curr);
1778 * Include at most one act per-thread that "happens
1781 if (act->happens_before(curr)) {
1783 * Note: if act is RMW, just add edge:
1785 * The following edge should be handled elsewhere:
1786 * readfrom(act) --mo--> act
1788 if (act->is_write())
1789 mo_graph->addEdge(act, curr);
1790 else if (act->is_read()) {
1791 //if previous read accessed a null, just keep going
1792 if (act->get_reads_from() == NULL)
1794 mo_graph->addEdge(act->get_reads_from(), curr);
1798 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1799 !act->same_thread(curr)) {
1800 /* We have an action that:
1801 (1) did not happen before us
1802 (2) is a read and we are a write
1803 (3) cannot synchronize with us
1804 (4) is in a different thread
1806 that read could potentially read from our write. Note that
1807 these checks are overly conservative at this point, we'll
1808 do more checks before actually removing the
1812 if (thin_air_constraint_may_allow(curr, act)) {
1813 if (!is_infeasible())
1814 futurevalues->push_back(PendingFutureValue(curr, act));
1815 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1816 add_future_value(curr, act);
1825 /** Arbitrary reads from the future are not allowed. Section 29.3
1826 * part 9 places some constraints. This method checks one result of constraint
1827 * constraint. Others require compiler support. */
1828 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1830 if (!writer->is_rmw())
1833 if (!reader->is_rmw())
1836 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1837 if (search == reader)
1839 if (search->get_tid() == reader->get_tid() &&
1840 search->happens_before(reader))
1848 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1849 * some constraints. This method checks one the following constraint (others
1850 * require compiler support):
1852 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1854 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1856 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1858 /* Iterate over all threads */
1859 for (i = 0; i < thrd_lists->size(); i++) {
1860 const ModelAction *write_after_read = NULL;
1862 /* Iterate over actions in thread, starting from most recent */
1863 action_list_t *list = &(*thrd_lists)[i];
1864 action_list_t::reverse_iterator rit;
1865 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1866 ModelAction *act = *rit;
1868 /* Don't disallow due to act == reader */
1869 if (!reader->happens_before(act) || reader == act)
1871 else if (act->is_write())
1872 write_after_read = act;
1873 else if (act->is_read() && act->get_reads_from() != NULL)
1874 write_after_read = act->get_reads_from();
1877 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1884 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1885 * The ModelAction under consideration is expected to be taking part in
1886 * release/acquire synchronization as an object of the "reads from" relation.
1887 * Note that this can only provide release sequence support for RMW chains
1888 * which do not read from the future, as those actions cannot be traced until
1889 * their "promise" is fulfilled. Similarly, we may not even establish the
1890 * presence of a release sequence with certainty, as some modification order
1891 * constraints may be decided further in the future. Thus, this function
1892 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1893 * and a boolean representing certainty.
1895 * @param rf The action that might be part of a release sequence. Must be a
1897 * @param release_heads A pass-by-reference style return parameter. After
1898 * execution of this function, release_heads will contain the heads of all the
1899 * relevant release sequences, if any exists with certainty
1900 * @param pending A pass-by-reference style return parameter which is only used
1901 * when returning false (i.e., uncertain). Returns most information regarding
1902 * an uncertain release sequence, including any write operations that might
1903 * break the sequence.
1904 * @return true, if the ModelChecker is certain that release_heads is complete;
1907 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1908 rel_heads_list_t *release_heads,
1909 struct release_seq *pending) const
1911 /* Only check for release sequences if there are no cycles */
1912 if (mo_graph->checkForCycles())
1916 ASSERT(rf->is_write());
1918 if (rf->is_release())
1919 release_heads->push_back(rf);
1920 else if (rf->get_last_fence_release())
1921 release_heads->push_back(rf->get_last_fence_release());
1923 break; /* End of RMW chain */
1925 /** @todo Need to be smarter here... In the linux lock
1926 * example, this will run to the beginning of the program for
1928 /** @todo The way to be smarter here is to keep going until 1
1929 * thread has a release preceded by an acquire and you've seen
1932 /* acq_rel RMW is a sufficient stopping condition */
1933 if (rf->is_acquire() && rf->is_release())
1934 return true; /* complete */
1936 rf = rf->get_reads_from();
1939 /* read from future: need to settle this later */
1941 return false; /* incomplete */
1944 if (rf->is_release())
1945 return true; /* complete */
1947 /* else relaxed write
1948 * - check for fence-release in the same thread (29.8, stmt. 3)
1949 * - check modification order for contiguous subsequence
1950 * -> rf must be same thread as release */
1952 const ModelAction *fence_release = rf->get_last_fence_release();
1953 /* Synchronize with a fence-release unconditionally; we don't need to
1954 * find any more "contiguous subsequence..." for it */
1956 release_heads->push_back(fence_release);
1958 int tid = id_to_int(rf->get_tid());
1959 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1960 action_list_t *list = &(*thrd_lists)[tid];
1961 action_list_t::const_reverse_iterator rit;
1963 /* Find rf in the thread list */
1964 rit = std::find(list->rbegin(), list->rend(), rf);
1965 ASSERT(rit != list->rend());
1967 /* Find the last {write,fence}-release */
1968 for (; rit != list->rend(); rit++) {
1969 if (fence_release && *(*rit) < *fence_release)
1971 if ((*rit)->is_release())
1974 if (rit == list->rend()) {
1975 /* No write-release in this thread */
1976 return true; /* complete */
1977 } else if (fence_release && *(*rit) < *fence_release) {
1978 /* The fence-release is more recent (and so, "stronger") than
1979 * the most recent write-release */
1980 return true; /* complete */
1981 } /* else, need to establish contiguous release sequence */
1982 ModelAction *release = *rit;
1984 ASSERT(rf->same_thread(release));
1986 pending->writes.clear();
1988 bool certain = true;
1989 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1990 if (id_to_int(rf->get_tid()) == (int)i)
1992 list = &(*thrd_lists)[i];
1994 /* Can we ensure no future writes from this thread may break
1995 * the release seq? */
1996 bool future_ordered = false;
1998 ModelAction *last = get_last_action(int_to_id(i));
1999 Thread *th = get_thread(int_to_id(i));
2000 if ((last && rf->happens_before(last)) ||
2003 future_ordered = true;
2005 ASSERT(!th->is_model_thread() || future_ordered);
2007 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2008 const ModelAction *act = *rit;
2009 /* Reach synchronization -> this thread is complete */
2010 if (act->happens_before(release))
2012 if (rf->happens_before(act)) {
2013 future_ordered = true;
2017 /* Only non-RMW writes can break release sequences */
2018 if (!act->is_write() || act->is_rmw())
2021 /* Check modification order */
2022 if (mo_graph->checkReachable(rf, act)) {
2023 /* rf --mo--> act */
2024 future_ordered = true;
2027 if (mo_graph->checkReachable(act, release))
2028 /* act --mo--> release */
2030 if (mo_graph->checkReachable(release, act) &&
2031 mo_graph->checkReachable(act, rf)) {
2032 /* release --mo-> act --mo--> rf */
2033 return true; /* complete */
2035 /* act may break release sequence */
2036 pending->writes.push_back(act);
2039 if (!future_ordered)
2040 certain = false; /* This thread is uncertain */
2044 release_heads->push_back(release);
2045 pending->writes.clear();
2047 pending->release = release;
2054 * An interface for getting the release sequence head(s) with which a
2055 * given ModelAction must synchronize. This function only returns a non-empty
2056 * result when it can locate a release sequence head with certainty. Otherwise,
2057 * it may mark the internal state of the ModelChecker so that it will handle
2058 * the release sequence at a later time, causing @a acquire to update its
2059 * synchronization at some later point in execution.
2061 * @param acquire The 'acquire' action that may synchronize with a release
2063 * @param read The read action that may read from a release sequence; this may
2064 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2065 * when 'acquire' is a fence-acquire)
2066 * @param release_heads A pass-by-reference return parameter. Will be filled
2067 * with the head(s) of the release sequence(s), if they exists with certainty.
2068 * @see ModelChecker::release_seq_heads
2070 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2071 ModelAction *read, rel_heads_list_t *release_heads)
2073 const ModelAction *rf = read->get_reads_from();
2074 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2075 sequence->acquire = acquire;
2076 sequence->read = read;
2078 if (!release_seq_heads(rf, release_heads, sequence)) {
2079 /* add act to 'lazy checking' list */
2080 pending_rel_seqs->push_back(sequence);
2082 snapshot_free(sequence);
2087 * Attempt to resolve all stashed operations that might synchronize with a
2088 * release sequence for a given location. This implements the "lazy" portion of
2089 * determining whether or not a release sequence was contiguous, since not all
2090 * modification order information is present at the time an action occurs.
2092 * @param location The location/object that should be checked for release
2093 * sequence resolutions. A NULL value means to check all locations.
2094 * @param work_queue The work queue to which to add work items as they are
2096 * @return True if any updates occurred (new synchronization, new mo_graph
2099 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2101 bool updated = false;
2102 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2103 while (it != pending_rel_seqs->end()) {
2104 struct release_seq *pending = *it;
2105 ModelAction *acquire = pending->acquire;
2106 const ModelAction *read = pending->read;
2108 /* Only resolve sequences on the given location, if provided */
2109 if (location && read->get_location() != location) {
2114 const ModelAction *rf = read->get_reads_from();
2115 rel_heads_list_t release_heads;
2117 complete = release_seq_heads(rf, &release_heads, pending);
2118 for (unsigned int i = 0; i < release_heads.size(); i++) {
2119 if (!acquire->has_synchronized_with(release_heads[i])) {
2120 if (acquire->synchronize_with(release_heads[i]))
2123 set_bad_synchronization();
2128 /* Re-check all pending release sequences */
2129 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2130 /* Re-check read-acquire for mo_graph edges */
2131 if (acquire->is_read())
2132 work_queue->push_back(MOEdgeWorkEntry(acquire));
2134 /* propagate synchronization to later actions */
2135 action_list_t::reverse_iterator rit = action_trace->rbegin();
2136 for (; (*rit) != acquire; rit++) {
2137 ModelAction *propagate = *rit;
2138 if (acquire->happens_before(propagate)) {
2139 propagate->synchronize_with(acquire);
2140 /* Re-check 'propagate' for mo_graph edges */
2141 work_queue->push_back(MOEdgeWorkEntry(propagate));
2146 it = pending_rel_seqs->erase(it);
2147 snapshot_free(pending);
2153 // If we resolved promises or data races, see if we have realized a data race.
2160 * Performs various bookkeeping operations for the current ModelAction. For
2161 * instance, adds action to the per-object, per-thread action vector and to the
2162 * action trace list of all thread actions.
2164 * @param act is the ModelAction to add.
2166 void ModelChecker::add_action_to_lists(ModelAction *act)
2168 int tid = id_to_int(act->get_tid());
2169 ModelAction *uninit = NULL;
2171 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2172 if (list->empty() && act->is_atomic_var()) {
2173 uninit = new_uninitialized_action(act->get_location());
2174 uninit_id = id_to_int(uninit->get_tid());
2175 list->push_back(uninit);
2177 list->push_back(act);
2179 action_trace->push_back(act);
2181 action_trace->push_front(uninit);
2183 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2184 if (tid >= (int)vec->size())
2185 vec->resize(priv->next_thread_id);
2186 (*vec)[tid].push_back(act);
2188 (*vec)[uninit_id].push_front(uninit);
2190 if ((int)thrd_last_action->size() <= tid)
2191 thrd_last_action->resize(get_num_threads());
2192 (*thrd_last_action)[tid] = act;
2194 (*thrd_last_action)[uninit_id] = uninit;
2196 if (act->is_fence() && act->is_release()) {
2197 if ((int)thrd_last_fence_release->size() <= tid)
2198 thrd_last_fence_release->resize(get_num_threads());
2199 (*thrd_last_fence_release)[tid] = act;
2202 if (act->is_wait()) {
2203 void *mutex_loc = (void *) act->get_value();
2204 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2206 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2207 if (tid >= (int)vec->size())
2208 vec->resize(priv->next_thread_id);
2209 (*vec)[tid].push_back(act);
2214 * @brief Get the last action performed by a particular Thread
2215 * @param tid The thread ID of the Thread in question
2216 * @return The last action in the thread
2218 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2220 int threadid = id_to_int(tid);
2221 if (threadid < (int)thrd_last_action->size())
2222 return (*thrd_last_action)[id_to_int(tid)];
2228 * @brief Get the last fence release performed by a particular Thread
2229 * @param tid The thread ID of the Thread in question
2230 * @return The last fence release in the thread, if one exists; NULL otherwise
2232 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2234 int threadid = id_to_int(tid);
2235 if (threadid < (int)thrd_last_fence_release->size())
2236 return (*thrd_last_fence_release)[id_to_int(tid)];
2242 * Gets the last memory_order_seq_cst write (in the total global sequence)
2243 * performed on a particular object (i.e., memory location), not including the
2245 * @param curr The current ModelAction; also denotes the object location to
2247 * @return The last seq_cst write
2249 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2251 void *location = curr->get_location();
2252 action_list_t *list = get_safe_ptr_action(obj_map, location);
2253 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2254 action_list_t::reverse_iterator rit;
2255 for (rit = list->rbegin(); rit != list->rend(); rit++)
2256 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2262 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2263 * performed in a particular thread, prior to a particular fence.
2264 * @param tid The ID of the thread to check
2265 * @param before_fence The fence from which to begin the search; if NULL, then
2266 * search for the most recent fence in the thread.
2267 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2269 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2271 /* All fences should have NULL location */
2272 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2273 action_list_t::reverse_iterator rit = list->rbegin();
2276 for (; rit != list->rend(); rit++)
2277 if (*rit == before_fence)
2280 ASSERT(*rit == before_fence);
2284 for (; rit != list->rend(); rit++)
2285 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2291 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2292 * location). This function identifies the mutex according to the current
2293 * action, which is presumed to perform on the same mutex.
2294 * @param curr The current ModelAction; also denotes the object location to
2296 * @return The last unlock operation
2298 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2300 void *location = curr->get_location();
2301 action_list_t *list = get_safe_ptr_action(obj_map, location);
2302 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2303 action_list_t::reverse_iterator rit;
2304 for (rit = list->rbegin(); rit != list->rend(); rit++)
2305 if ((*rit)->is_unlock() || (*rit)->is_wait())
2310 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2312 ModelAction *parent = get_last_action(tid);
2314 parent = get_thread(tid)->get_creation();
2319 * Returns the clock vector for a given thread.
2320 * @param tid The thread whose clock vector we want
2321 * @return Desired clock vector
2323 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2325 return get_parent_action(tid)->get_cv();
2329 * Resolve a set of Promises with a current write. The set is provided in the
2330 * Node corresponding to @a write.
2331 * @param write The ModelAction that is fulfilling Promises
2332 * @return True if promises were resolved; false otherwise
2334 bool ModelChecker::resolve_promises(ModelAction *write)
2336 bool resolved = false;
2337 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2339 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2340 Promise *promise = (*promises)[promise_index];
2341 if (write->get_node()->get_promise(i)) {
2342 ModelAction *read = promise->get_action();
2343 if (read->is_rmw()) {
2344 mo_graph->addRMWEdge(write, read);
2346 read_from(read, write);
2347 //First fix up the modification order for actions that happened
2349 r_modification_order(read, write);
2350 //Next fix up the modification order for actions that happened
2352 post_r_modification_order(read, write);
2353 //Make sure the promise's value matches the write's value
2354 ASSERT(promise->get_value() == write->get_value());
2357 promises->erase(promises->begin() + promise_index);
2358 actions_to_check.push_back(read);
2365 //Check whether reading these writes has made threads unable to
2368 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2369 ModelAction *read=actions_to_check[i];
2370 mo_check_promises(read->get_tid(), write, read);
2377 * Compute the set of promises that could potentially be satisfied by this
2378 * action. Note that the set computation actually appears in the Node, not in
2380 * @param curr The ModelAction that may satisfy promises
2382 void ModelChecker::compute_promises(ModelAction *curr)
2384 for (unsigned int i = 0; i < promises->size(); i++) {
2385 Promise *promise = (*promises)[i];
2386 const ModelAction *act = promise->get_action();
2387 if (!act->happens_before(curr) &&
2389 !act->could_synchronize_with(curr) &&
2390 !act->same_thread(curr) &&
2391 act->get_location() == curr->get_location() &&
2392 promise->get_value() == curr->get_value()) {
2393 curr->get_node()->set_promise(i, act->is_rmw());
2398 /** Checks promises in response to change in ClockVector Threads. */
2399 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2401 for (unsigned int i = 0; i < promises->size(); i++) {
2402 Promise *promise = (*promises)[i];
2403 const ModelAction *act = promise->get_action();
2404 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2405 merge_cv->synchronized_since(act)) {
2406 if (promise->eliminate_thread(tid)) {
2407 //Promise has failed
2408 priv->failed_promise = true;
2415 void ModelChecker::check_promises_thread_disabled()
2417 for (unsigned int i = 0; i < promises->size(); i++) {
2418 Promise *promise = (*promises)[i];
2419 if (promise->has_failed()) {
2420 priv->failed_promise = true;
2427 * @brief Checks promises in response to addition to modification order for
2432 * pthread is the thread that performed the read that created the promise
2434 * pread is the read that created the promise
2436 * pwrite is either the first write to same location as pread by
2437 * pthread that is sequenced after pread or the write read by the
2438 * first read to the same location as pread by pthread that is
2439 * sequenced after pread.
2441 * 1. If tid=pthread, then we check what other threads are reachable
2442 * through the mod order starting with pwrite. Those threads cannot
2443 * perform a write that will resolve the promise due to modification
2444 * order constraints.
2446 * 2. If the tid is not pthread, we check whether pwrite can reach the
2447 * action write through the modification order. If so, that thread
2448 * cannot perform a future write that will resolve the promise due to
2449 * modificatin order constraints.
2451 * @param tid The thread that either read from the model action write, or
2452 * actually did the model action write.
2454 * @param write The ModelAction representing the relevant write.
2455 * @param read The ModelAction that reads a promised write, or NULL otherwise.
2457 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write, const ModelAction *read)
2459 void *location = write->get_location();
2460 for (unsigned int i = 0; i < promises->size(); i++) {
2461 Promise *promise = (*promises)[i];
2462 const ModelAction *act = promise->get_action();
2464 // Is this promise on the same location?
2465 if (act->get_location() != location)
2468 // same thread as the promise
2469 if (act->get_tid() == tid) {
2470 // make sure that the reader of this write happens after the promise
2471 if ((read == NULL) || (promise->get_action()->happens_before(read))) {
2472 // do we have a pwrite for the promise, if not, set it
2473 if (promise->get_write() == NULL) {
2474 promise->set_write(write);
2475 // The pwrite cannot happen before the promise
2476 if (write->happens_before(act) && (write != act)) {
2477 priv->failed_promise = true;
2482 if (mo_graph->checkPromise(write, promise)) {
2483 priv->failed_promise = true;
2489 // Don't do any lookups twice for the same thread
2490 if (!promise->thread_is_available(tid))
2493 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2494 if (promise->eliminate_thread(tid)) {
2495 priv->failed_promise = true;
2503 * Compute the set of writes that may break the current pending release
2504 * sequence. This information is extracted from previou release sequence
2507 * @param curr The current ModelAction. Must be a release sequence fixup
2510 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2512 if (pending_rel_seqs->empty())
2515 struct release_seq *pending = pending_rel_seqs->back();
2516 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2517 const ModelAction *write = pending->writes[i];
2518 curr->get_node()->add_relseq_break(write);
2521 /* NULL means don't break the sequence; just synchronize */
2522 curr->get_node()->add_relseq_break(NULL);
2526 * Build up an initial set of all past writes that this 'read' action may read
2527 * from. This set is determined by the clock vector's "happens before"
2529 * @param curr is the current ModelAction that we are exploring; it must be a
2532 void ModelChecker::build_reads_from_past(ModelAction *curr)
2534 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2536 ASSERT(curr->is_read());
2538 ModelAction *last_sc_write = NULL;
2540 if (curr->is_seqcst())
2541 last_sc_write = get_last_seq_cst_write(curr);
2543 /* Iterate over all threads */
2544 for (i = 0; i < thrd_lists->size(); i++) {
2545 /* Iterate over actions in thread, starting from most recent */
2546 action_list_t *list = &(*thrd_lists)[i];
2547 action_list_t::reverse_iterator rit;
2548 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2549 ModelAction *act = *rit;
2551 /* Only consider 'write' actions */
2552 if (!act->is_write() || act == curr)
2555 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2556 bool allow_read = true;
2558 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2560 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2564 curr->get_node()->add_read_from(act);
2566 /* Include at most one act per-thread that "happens before" curr */
2567 if (act->happens_before(curr))
2572 if (DBG_ENABLED()) {
2573 model_print("Reached read action:\n");
2575 model_print("Printing may_read_from\n");
2576 curr->get_node()->print_may_read_from();
2577 model_print("End printing may_read_from\n");
2581 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2584 /* UNINIT actions don't have a Node, and they never sleep */
2585 if (write->is_uninitialized())
2587 Node *prevnode = write->get_node()->get_parent();
2589 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2590 if (write->is_release() && thread_sleep)
2592 if (!write->is_rmw()) {
2595 if (write->get_reads_from() == NULL)
2597 write = write->get_reads_from();
2602 * @brief Create a new action representing an uninitialized atomic
2603 * @param location The memory location of the atomic object
2604 * @return A pointer to a new ModelAction
2606 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2608 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2609 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2610 act->create_cv(NULL);
2614 static void print_list(action_list_t *list)
2616 action_list_t::iterator it;
2618 model_print("---------------------------------------------------------------------\n");
2620 unsigned int hash = 0;
2622 for (it = list->begin(); it != list->end(); it++) {
2624 hash = hash^(hash<<3)^((*it)->hash());
2626 model_print("HASH %u\n", hash);
2627 model_print("---------------------------------------------------------------------\n");
2630 #if SUPPORT_MOD_ORDER_DUMP
2631 void ModelChecker::dumpGraph(char *filename) const
2634 sprintf(buffer, "%s.dot", filename);
2635 FILE *file = fopen(buffer, "w");
2636 fprintf(file, "digraph %s {\n", filename);
2637 mo_graph->dumpNodes(file);
2638 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2640 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2641 ModelAction *action = *it;
2642 if (action->is_read()) {
2643 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2644 if (action->get_reads_from() != NULL)
2645 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2647 if (thread_array[action->get_tid()] != NULL) {
2648 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2651 thread_array[action->get_tid()] = action;
2653 fprintf(file, "}\n");
2654 model_free(thread_array);
2659 /** @brief Prints an execution trace summary. */
2660 void ModelChecker::print_summary() const
2662 #if SUPPORT_MOD_ORDER_DUMP
2664 char buffername[100];
2665 sprintf(buffername, "exec%04u", stats.num_total);
2666 mo_graph->dumpGraphToFile(buffername);
2667 sprintf(buffername, "graph%04u", stats.num_total);
2668 dumpGraph(buffername);
2671 model_print("Execution %d:", stats.num_total);
2672 if (isfeasibleprefix())
2675 print_infeasibility(" INFEASIBLE");
2676 print_list(action_trace);
2681 * Add a Thread to the system for the first time. Should only be called once
2683 * @param t The Thread to add
2685 void ModelChecker::add_thread(Thread *t)
2687 thread_map->put(id_to_int(t->get_id()), t);
2688 scheduler->add_thread(t);
2692 * Removes a thread from the scheduler.
2693 * @param the thread to remove.
2695 void ModelChecker::remove_thread(Thread *t)
2697 scheduler->remove_thread(t);
2701 * @brief Get a Thread reference by its ID
2702 * @param tid The Thread's ID
2703 * @return A Thread reference
2705 Thread * ModelChecker::get_thread(thread_id_t tid) const
2707 return thread_map->get(id_to_int(tid));
2711 * @brief Get a reference to the Thread in which a ModelAction was executed
2712 * @param act The ModelAction
2713 * @return A Thread reference
2715 Thread * ModelChecker::get_thread(const ModelAction *act) const
2717 return get_thread(act->get_tid());
2721 * @brief Check if a Thread is currently enabled
2722 * @param t The Thread to check
2723 * @return True if the Thread is currently enabled
2725 bool ModelChecker::is_enabled(Thread *t) const
2727 return scheduler->is_enabled(t);
2731 * @brief Check if a Thread is currently enabled
2732 * @param tid The ID of the Thread to check
2733 * @return True if the Thread is currently enabled
2735 bool ModelChecker::is_enabled(thread_id_t tid) const
2737 return scheduler->is_enabled(tid);
2741 * Switch from a user-context to the "master thread" context (a.k.a. system
2742 * context). This switch is made with the intention of exploring a particular
2743 * model-checking action (described by a ModelAction object). Must be called
2744 * from a user-thread context.
2746 * @param act The current action that will be explored. May be NULL only if
2747 * trace is exiting via an assertion (see ModelChecker::set_assert and
2748 * ModelChecker::has_asserted).
2749 * @return Return the value returned by the current action
2751 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2754 Thread *old = thread_current();
2755 set_current_action(act);
2756 old->set_state(THREAD_READY);
2757 if (Thread::swap(old, &system_context) < 0) {
2758 perror("swap threads");
2761 return old->get_return_value();
2765 * Takes the next step in the execution, if possible.
2766 * @param curr The current step to take
2767 * @return Returns true (success) if a step was taken and false otherwise.
2769 bool ModelChecker::take_step(ModelAction *curr)
2774 Thread *curr_thrd = get_thread(curr);
2775 ASSERT(curr_thrd->get_state() == THREAD_READY);
2777 curr = check_current_action(curr);
2779 /* Infeasible -> don't take any more steps */
2780 if (is_infeasible())
2782 else if (isfeasibleprefix() && have_bug_reports()) {
2787 if (params.bound != 0)
2788 if (priv->used_sequence_numbers > params.bound)
2791 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2792 scheduler->remove_thread(curr_thrd);
2794 Thread *next_thrd = get_next_thread(curr);
2795 next_thrd = scheduler->next_thread(next_thrd);
2797 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2798 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2801 * Launch end-of-execution release sequence fixups only when there are:
2803 * (1) no more user threads to run (or when execution replay chooses
2804 * the 'model_thread')
2805 * (2) pending release sequences
2806 * (3) pending assertions (i.e., data races)
2807 * (4) no pending promises
2809 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2810 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2811 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2812 pending_rel_seqs->size());
2813 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2814 std::memory_order_seq_cst, NULL, VALUE_NONE,
2816 set_current_action(fixup);
2820 /* next_thrd == NULL -> don't take any more steps */
2824 next_thrd->set_state(THREAD_RUNNING);
2826 if (next_thrd->get_pending() != NULL) {
2827 /* restart a pending action */
2828 set_current_action(next_thrd->get_pending());
2829 next_thrd->set_pending(NULL);
2830 next_thrd->set_state(THREAD_READY);
2834 /* Return false only if swap fails with an error */
2835 return (Thread::swap(&system_context, next_thrd) == 0);
2838 /** Wrapper to run the user's main function, with appropriate arguments */
2839 void user_main_wrapper(void *)
2841 user_main(model->params.argc, model->params.argv);
2844 /** @brief Run ModelChecker for the user program */
2845 void ModelChecker::run()
2849 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2853 /* Run user thread up to its first action */
2854 scheduler->next_thread(t);
2855 Thread::swap(&system_context, t);
2857 /* Wait for all threads to complete */
2858 while (take_step(priv->current_action));
2859 } while (next_execution());