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() ||
1411 mo_graph->checkForCycles() ||
1412 priv->failed_promise ||
1413 priv->too_many_reads ||
1414 priv->bad_synchronization ||
1418 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1419 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1420 ModelAction *lastread = get_last_action(act->get_tid());
1421 lastread->process_rmw(act);
1422 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1423 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1424 mo_graph->commitChanges();
1430 * Checks whether a thread has read from the same write for too many times
1431 * without seeing the effects of a later write.
1434 * 1) there must a different write that we could read from that would satisfy the modification order,
1435 * 2) we must have read from the same value in excess of maxreads times, and
1436 * 3) that other write must have been in the reads_from set for maxreads times.
1438 * If so, we decide that the execution is no longer feasible.
1440 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1442 if (params.maxreads != 0) {
1443 if (curr->get_node()->get_read_from_size() <= 1)
1445 //Must make sure that execution is currently feasible... We could
1446 //accidentally clear by rolling back
1447 if (is_infeasible())
1449 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1450 int tid = id_to_int(curr->get_tid());
1453 if ((int)thrd_lists->size() <= tid)
1455 action_list_t *list = &(*thrd_lists)[tid];
1457 action_list_t::reverse_iterator rit = list->rbegin();
1458 /* Skip past curr */
1459 for (; (*rit) != curr; rit++)
1461 /* go past curr now */
1464 action_list_t::reverse_iterator ritcopy = rit;
1465 //See if we have enough reads from the same value
1467 for (; count < params.maxreads; rit++, count++) {
1468 if (rit == list->rend())
1470 ModelAction *act = *rit;
1471 if (!act->is_read())
1474 if (act->get_reads_from() != rf)
1476 if (act->get_node()->get_read_from_size() <= 1)
1479 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1481 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1483 /* Need a different write */
1487 /* Test to see whether this is a feasible write to read from */
1488 mo_graph->startChanges();
1489 r_modification_order(curr, write);
1490 bool feasiblereadfrom = !is_infeasible();
1491 mo_graph->rollbackChanges();
1493 if (!feasiblereadfrom)
1497 bool feasiblewrite = true;
1498 //new we need to see if this write works for everyone
1500 for (int loop = count; loop > 0; loop--, rit++) {
1501 ModelAction *act = *rit;
1502 bool foundvalue = false;
1503 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1504 if (act->get_node()->get_read_from_at(j) == write) {
1510 feasiblewrite = false;
1514 if (feasiblewrite) {
1515 priv->too_many_reads = true;
1523 * Updates the mo_graph with the constraints imposed from the current
1526 * Basic idea is the following: Go through each other thread and find
1527 * the lastest action that happened before our read. Two cases:
1529 * (1) The action is a write => that write must either occur before
1530 * the write we read from or be the write we read from.
1532 * (2) The action is a read => the write that that action read from
1533 * must occur before the write we read from or be the same write.
1535 * @param curr The current action. Must be a read.
1536 * @param rf The action that curr reads from. Must be a write.
1537 * @return True if modification order edges were added; false otherwise
1539 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1541 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1544 ASSERT(curr->is_read());
1546 /* Last SC fence in the current thread */
1547 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1549 /* Iterate over all threads */
1550 for (i = 0; i < thrd_lists->size(); i++) {
1551 /* Last SC fence in thread i */
1552 ModelAction *last_sc_fence_thread_local = NULL;
1553 if (int_to_id((int)i) != curr->get_tid())
1554 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1556 /* Last SC fence in thread i, before last SC fence in current thread */
1557 ModelAction *last_sc_fence_thread_before = NULL;
1558 if (last_sc_fence_local)
1559 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1561 /* Iterate over actions in thread, starting from most recent */
1562 action_list_t *list = &(*thrd_lists)[i];
1563 action_list_t::reverse_iterator rit;
1564 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1565 ModelAction *act = *rit;
1567 if (act->is_write() && act != rf && act != curr) {
1568 /* C++, Section 29.3 statement 5 */
1569 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1570 *act < *last_sc_fence_thread_local) {
1571 mo_graph->addEdge(act, rf);
1575 /* C++, Section 29.3 statement 4 */
1576 else if (act->is_seqcst() && last_sc_fence_local &&
1577 *act < *last_sc_fence_local) {
1578 mo_graph->addEdge(act, rf);
1582 /* C++, Section 29.3 statement 6 */
1583 else if (last_sc_fence_thread_before &&
1584 *act < *last_sc_fence_thread_before) {
1585 mo_graph->addEdge(act, rf);
1592 * Include at most one act per-thread that "happens
1593 * before" curr. Don't consider reflexively.
1595 if (act->happens_before(curr) && act != curr) {
1596 if (act->is_write()) {
1598 mo_graph->addEdge(act, rf);
1602 const ModelAction *prevreadfrom = act->get_reads_from();
1603 //if the previous read is unresolved, keep going...
1604 if (prevreadfrom == NULL)
1607 if (rf != prevreadfrom) {
1608 mo_graph->addEdge(prevreadfrom, rf);
1620 /** This method fixes up the modification order when we resolve a
1621 * promises. The basic problem is that actions that occur after the
1622 * read curr could not property add items to the modification order
1625 * So for each thread, we find the earliest item that happens after
1626 * the read curr. This is the item we have to fix up with additional
1627 * constraints. If that action is write, we add a MO edge between
1628 * the Action rf and that action. If the action is a read, we add a
1629 * MO edge between the Action rf, and whatever the read accessed.
1631 * @param curr is the read ModelAction that we are fixing up MO edges for.
1632 * @param rf is the write ModelAction that curr reads from.
1635 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1637 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1639 ASSERT(curr->is_read());
1641 /* Iterate over all threads */
1642 for (i = 0; i < thrd_lists->size(); i++) {
1643 /* Iterate over actions in thread, starting from most recent */
1644 action_list_t *list = &(*thrd_lists)[i];
1645 action_list_t::reverse_iterator rit;
1646 ModelAction *lastact = NULL;
1648 /* Find last action that happens after curr that is either not curr or a rmw */
1649 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1650 ModelAction *act = *rit;
1651 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1657 /* Include at most one act per-thread that "happens before" curr */
1658 if (lastact != NULL) {
1659 if (lastact == curr) {
1660 //Case 1: The resolved read is a RMW, and we need to make sure
1661 //that the write portion of the RMW mod order after rf
1663 mo_graph->addEdge(rf, lastact);
1664 } else if (lastact->is_read()) {
1665 //Case 2: The resolved read is a normal read and the next
1666 //operation is a read, and we need to make sure the value read
1667 //is mod ordered after rf
1669 const ModelAction *postreadfrom = lastact->get_reads_from();
1670 if (postreadfrom != NULL && rf != postreadfrom)
1671 mo_graph->addEdge(rf, postreadfrom);
1673 //Case 3: The resolved read is a normal read and the next
1674 //operation is a write, and we need to make sure that the
1675 //write is mod ordered after rf
1677 mo_graph->addEdge(rf, lastact);
1685 * Updates the mo_graph with the constraints imposed from the current write.
1687 * Basic idea is the following: Go through each other thread and find
1688 * the lastest action that happened before our write. Two cases:
1690 * (1) The action is a write => that write must occur before
1693 * (2) The action is a read => the write that that action read from
1694 * must occur before the current write.
1696 * This method also handles two other issues:
1698 * (I) Sequential Consistency: Making sure that if the current write is
1699 * seq_cst, that it occurs after the previous seq_cst write.
1701 * (II) Sending the write back to non-synchronizing reads.
1703 * @param curr The current action. Must be a write.
1704 * @return True if modification order edges were added; false otherwise
1706 bool ModelChecker::w_modification_order(ModelAction *curr)
1708 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1711 ASSERT(curr->is_write());
1713 if (curr->is_seqcst()) {
1714 /* We have to at least see the last sequentially consistent write,
1715 so we are initialized. */
1716 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1717 if (last_seq_cst != NULL) {
1718 mo_graph->addEdge(last_seq_cst, curr);
1723 /* Last SC fence in the current thread */
1724 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1726 /* Iterate over all threads */
1727 for (i = 0; i < thrd_lists->size(); i++) {
1728 /* Last SC fence in thread i, before last SC fence in current thread */
1729 ModelAction *last_sc_fence_thread_before = NULL;
1730 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1731 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1733 /* Iterate over actions in thread, starting from most recent */
1734 action_list_t *list = &(*thrd_lists)[i];
1735 action_list_t::reverse_iterator rit;
1736 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1737 ModelAction *act = *rit;
1740 * 1) If RMW and it actually read from something, then we
1741 * already have all relevant edges, so just skip to next
1744 * 2) If RMW and it didn't read from anything, we should
1745 * whatever edge we can get to speed up convergence.
1747 * 3) If normal write, we need to look at earlier actions, so
1748 * continue processing list.
1750 if (curr->is_rmw()) {
1751 if (curr->get_reads_from() != NULL)
1759 /* C++, Section 29.3 statement 7 */
1760 if (last_sc_fence_thread_before && act->is_write() &&
1761 *act < *last_sc_fence_thread_before) {
1762 mo_graph->addEdge(act, curr);
1768 * Include at most one act per-thread that "happens
1771 if (act->happens_before(curr)) {
1773 * Note: if act is RMW, just add edge:
1775 * The following edge should be handled elsewhere:
1776 * readfrom(act) --mo--> act
1778 if (act->is_write())
1779 mo_graph->addEdge(act, curr);
1780 else if (act->is_read()) {
1781 //if previous read accessed a null, just keep going
1782 if (act->get_reads_from() == NULL)
1784 mo_graph->addEdge(act->get_reads_from(), curr);
1788 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1789 !act->same_thread(curr)) {
1790 /* We have an action that:
1791 (1) did not happen before us
1792 (2) is a read and we are a write
1793 (3) cannot synchronize with us
1794 (4) is in a different thread
1796 that read could potentially read from our write. Note that
1797 these checks are overly conservative at this point, we'll
1798 do more checks before actually removing the
1802 if (thin_air_constraint_may_allow(curr, act)) {
1803 if (!is_infeasible())
1804 futurevalues->push_back(PendingFutureValue(curr, act));
1805 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1806 add_future_value(curr, act);
1815 /** Arbitrary reads from the future are not allowed. Section 29.3
1816 * part 9 places some constraints. This method checks one result of constraint
1817 * constraint. Others require compiler support. */
1818 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1820 if (!writer->is_rmw())
1823 if (!reader->is_rmw())
1826 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1827 if (search == reader)
1829 if (search->get_tid() == reader->get_tid() &&
1830 search->happens_before(reader))
1838 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1839 * some constraints. This method checks one the following constraint (others
1840 * require compiler support):
1842 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1844 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1846 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1848 /* Iterate over all threads */
1849 for (i = 0; i < thrd_lists->size(); i++) {
1850 const ModelAction *write_after_read = NULL;
1852 /* Iterate over actions in thread, starting from most recent */
1853 action_list_t *list = &(*thrd_lists)[i];
1854 action_list_t::reverse_iterator rit;
1855 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1856 ModelAction *act = *rit;
1858 /* Don't disallow due to act == reader */
1859 if (!reader->happens_before(act) || reader == act)
1861 else if (act->is_write())
1862 write_after_read = act;
1863 else if (act->is_read() && act->get_reads_from() != NULL)
1864 write_after_read = act->get_reads_from();
1867 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1874 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1875 * The ModelAction under consideration is expected to be taking part in
1876 * release/acquire synchronization as an object of the "reads from" relation.
1877 * Note that this can only provide release sequence support for RMW chains
1878 * which do not read from the future, as those actions cannot be traced until
1879 * their "promise" is fulfilled. Similarly, we may not even establish the
1880 * presence of a release sequence with certainty, as some modification order
1881 * constraints may be decided further in the future. Thus, this function
1882 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1883 * and a boolean representing certainty.
1885 * @param rf The action that might be part of a release sequence. Must be a
1887 * @param release_heads A pass-by-reference style return parameter. After
1888 * execution of this function, release_heads will contain the heads of all the
1889 * relevant release sequences, if any exists with certainty
1890 * @param pending A pass-by-reference style return parameter which is only used
1891 * when returning false (i.e., uncertain). Returns most information regarding
1892 * an uncertain release sequence, including any write operations that might
1893 * break the sequence.
1894 * @return true, if the ModelChecker is certain that release_heads is complete;
1897 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1898 rel_heads_list_t *release_heads,
1899 struct release_seq *pending) const
1901 /* Only check for release sequences if there are no cycles */
1902 if (mo_graph->checkForCycles())
1906 ASSERT(rf->is_write());
1908 if (rf->is_release())
1909 release_heads->push_back(rf);
1910 else if (rf->get_last_fence_release())
1911 release_heads->push_back(rf->get_last_fence_release());
1913 break; /* End of RMW chain */
1915 /** @todo Need to be smarter here... In the linux lock
1916 * example, this will run to the beginning of the program for
1918 /** @todo The way to be smarter here is to keep going until 1
1919 * thread has a release preceded by an acquire and you've seen
1922 /* acq_rel RMW is a sufficient stopping condition */
1923 if (rf->is_acquire() && rf->is_release())
1924 return true; /* complete */
1926 rf = rf->get_reads_from();
1929 /* read from future: need to settle this later */
1931 return false; /* incomplete */
1934 if (rf->is_release())
1935 return true; /* complete */
1937 /* else relaxed write
1938 * - check for fence-release in the same thread (29.8, stmt. 3)
1939 * - check modification order for contiguous subsequence
1940 * -> rf must be same thread as release */
1942 const ModelAction *fence_release = rf->get_last_fence_release();
1943 /* Synchronize with a fence-release unconditionally; we don't need to
1944 * find any more "contiguous subsequence..." for it */
1946 release_heads->push_back(fence_release);
1948 int tid = id_to_int(rf->get_tid());
1949 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1950 action_list_t *list = &(*thrd_lists)[tid];
1951 action_list_t::const_reverse_iterator rit;
1953 /* Find rf in the thread list */
1954 rit = std::find(list->rbegin(), list->rend(), rf);
1955 ASSERT(rit != list->rend());
1957 /* Find the last {write,fence}-release */
1958 for (; rit != list->rend(); rit++) {
1959 if (fence_release && *(*rit) < *fence_release)
1961 if ((*rit)->is_release())
1964 if (rit == list->rend()) {
1965 /* No write-release in this thread */
1966 return true; /* complete */
1967 } else if (fence_release && *(*rit) < *fence_release) {
1968 /* The fence-release is more recent (and so, "stronger") than
1969 * the most recent write-release */
1970 return true; /* complete */
1971 } /* else, need to establish contiguous release sequence */
1972 ModelAction *release = *rit;
1974 ASSERT(rf->same_thread(release));
1976 pending->writes.clear();
1978 bool certain = true;
1979 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1980 if (id_to_int(rf->get_tid()) == (int)i)
1982 list = &(*thrd_lists)[i];
1984 /* Can we ensure no future writes from this thread may break
1985 * the release seq? */
1986 bool future_ordered = false;
1988 ModelAction *last = get_last_action(int_to_id(i));
1989 Thread *th = get_thread(int_to_id(i));
1990 if ((last && rf->happens_before(last)) ||
1993 future_ordered = true;
1995 ASSERT(!th->is_model_thread() || future_ordered);
1997 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1998 const ModelAction *act = *rit;
1999 /* Reach synchronization -> this thread is complete */
2000 if (act->happens_before(release))
2002 if (rf->happens_before(act)) {
2003 future_ordered = true;
2007 /* Only non-RMW writes can break release sequences */
2008 if (!act->is_write() || act->is_rmw())
2011 /* Check modification order */
2012 if (mo_graph->checkReachable(rf, act)) {
2013 /* rf --mo--> act */
2014 future_ordered = true;
2017 if (mo_graph->checkReachable(act, release))
2018 /* act --mo--> release */
2020 if (mo_graph->checkReachable(release, act) &&
2021 mo_graph->checkReachable(act, rf)) {
2022 /* release --mo-> act --mo--> rf */
2023 return true; /* complete */
2025 /* act may break release sequence */
2026 pending->writes.push_back(act);
2029 if (!future_ordered)
2030 certain = false; /* This thread is uncertain */
2034 release_heads->push_back(release);
2035 pending->writes.clear();
2037 pending->release = release;
2044 * An interface for getting the release sequence head(s) with which a
2045 * given ModelAction must synchronize. This function only returns a non-empty
2046 * result when it can locate a release sequence head with certainty. Otherwise,
2047 * it may mark the internal state of the ModelChecker so that it will handle
2048 * the release sequence at a later time, causing @a acquire to update its
2049 * synchronization at some later point in execution.
2051 * @param acquire The 'acquire' action that may synchronize with a release
2053 * @param read The read action that may read from a release sequence; this may
2054 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2055 * when 'acquire' is a fence-acquire)
2056 * @param release_heads A pass-by-reference return parameter. Will be filled
2057 * with the head(s) of the release sequence(s), if they exists with certainty.
2058 * @see ModelChecker::release_seq_heads
2060 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2061 ModelAction *read, rel_heads_list_t *release_heads)
2063 const ModelAction *rf = read->get_reads_from();
2064 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2065 sequence->acquire = acquire;
2066 sequence->read = read;
2068 if (!release_seq_heads(rf, release_heads, sequence)) {
2069 /* add act to 'lazy checking' list */
2070 pending_rel_seqs->push_back(sequence);
2072 snapshot_free(sequence);
2077 * Attempt to resolve all stashed operations that might synchronize with a
2078 * release sequence for a given location. This implements the "lazy" portion of
2079 * determining whether or not a release sequence was contiguous, since not all
2080 * modification order information is present at the time an action occurs.
2082 * @param location The location/object that should be checked for release
2083 * sequence resolutions. A NULL value means to check all locations.
2084 * @param work_queue The work queue to which to add work items as they are
2086 * @return True if any updates occurred (new synchronization, new mo_graph
2089 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2091 bool updated = false;
2092 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2093 while (it != pending_rel_seqs->end()) {
2094 struct release_seq *pending = *it;
2095 ModelAction *acquire = pending->acquire;
2096 const ModelAction *read = pending->read;
2098 /* Only resolve sequences on the given location, if provided */
2099 if (location && read->get_location() != location) {
2104 const ModelAction *rf = read->get_reads_from();
2105 rel_heads_list_t release_heads;
2107 complete = release_seq_heads(rf, &release_heads, pending);
2108 for (unsigned int i = 0; i < release_heads.size(); i++) {
2109 if (!acquire->has_synchronized_with(release_heads[i])) {
2110 if (acquire->synchronize_with(release_heads[i]))
2113 set_bad_synchronization();
2118 /* Re-check all pending release sequences */
2119 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2120 /* Re-check read-acquire for mo_graph edges */
2121 if (acquire->is_read())
2122 work_queue->push_back(MOEdgeWorkEntry(acquire));
2124 /* propagate synchronization to later actions */
2125 action_list_t::reverse_iterator rit = action_trace->rbegin();
2126 for (; (*rit) != acquire; rit++) {
2127 ModelAction *propagate = *rit;
2128 if (acquire->happens_before(propagate)) {
2129 propagate->synchronize_with(acquire);
2130 /* Re-check 'propagate' for mo_graph edges */
2131 work_queue->push_back(MOEdgeWorkEntry(propagate));
2136 it = pending_rel_seqs->erase(it);
2137 snapshot_free(pending);
2143 // If we resolved promises or data races, see if we have realized a data race.
2150 * Performs various bookkeeping operations for the current ModelAction. For
2151 * instance, adds action to the per-object, per-thread action vector and to the
2152 * action trace list of all thread actions.
2154 * @param act is the ModelAction to add.
2156 void ModelChecker::add_action_to_lists(ModelAction *act)
2158 int tid = id_to_int(act->get_tid());
2159 ModelAction *uninit = NULL;
2161 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2162 if (list->empty() && act->is_atomic_var()) {
2163 uninit = new_uninitialized_action(act->get_location());
2164 uninit_id = id_to_int(uninit->get_tid());
2165 list->push_back(uninit);
2167 list->push_back(act);
2169 action_trace->push_back(act);
2171 action_trace->push_front(uninit);
2173 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2174 if (tid >= (int)vec->size())
2175 vec->resize(priv->next_thread_id);
2176 (*vec)[tid].push_back(act);
2178 (*vec)[uninit_id].push_front(uninit);
2180 if ((int)thrd_last_action->size() <= tid)
2181 thrd_last_action->resize(get_num_threads());
2182 (*thrd_last_action)[tid] = act;
2184 (*thrd_last_action)[uninit_id] = uninit;
2186 if (act->is_fence() && act->is_release()) {
2187 if ((int)thrd_last_fence_release->size() <= tid)
2188 thrd_last_fence_release->resize(get_num_threads());
2189 (*thrd_last_fence_release)[tid] = act;
2192 if (act->is_wait()) {
2193 void *mutex_loc = (void *) act->get_value();
2194 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2196 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2197 if (tid >= (int)vec->size())
2198 vec->resize(priv->next_thread_id);
2199 (*vec)[tid].push_back(act);
2204 * @brief Get the last action performed by a particular Thread
2205 * @param tid The thread ID of the Thread in question
2206 * @return The last action in the thread
2208 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2210 int threadid = id_to_int(tid);
2211 if (threadid < (int)thrd_last_action->size())
2212 return (*thrd_last_action)[id_to_int(tid)];
2218 * @brief Get the last fence release performed by a particular Thread
2219 * @param tid The thread ID of the Thread in question
2220 * @return The last fence release in the thread, if one exists; NULL otherwise
2222 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2224 int threadid = id_to_int(tid);
2225 if (threadid < (int)thrd_last_fence_release->size())
2226 return (*thrd_last_fence_release)[id_to_int(tid)];
2232 * Gets the last memory_order_seq_cst write (in the total global sequence)
2233 * performed on a particular object (i.e., memory location), not including the
2235 * @param curr The current ModelAction; also denotes the object location to
2237 * @return The last seq_cst write
2239 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2241 void *location = curr->get_location();
2242 action_list_t *list = get_safe_ptr_action(obj_map, location);
2243 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2244 action_list_t::reverse_iterator rit;
2245 for (rit = list->rbegin(); rit != list->rend(); rit++)
2246 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2252 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2253 * performed in a particular thread, prior to a particular fence.
2254 * @param tid The ID of the thread to check
2255 * @param before_fence The fence from which to begin the search; if NULL, then
2256 * search for the most recent fence in the thread.
2257 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2259 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2261 /* All fences should have NULL location */
2262 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2263 action_list_t::reverse_iterator rit = list->rbegin();
2266 for (; rit != list->rend(); rit++)
2267 if (*rit == before_fence)
2270 ASSERT(*rit == before_fence);
2274 for (; rit != list->rend(); rit++)
2275 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2281 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2282 * location). This function identifies the mutex according to the current
2283 * action, which is presumed to perform on the same mutex.
2284 * @param curr The current ModelAction; also denotes the object location to
2286 * @return The last unlock operation
2288 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2290 void *location = curr->get_location();
2291 action_list_t *list = get_safe_ptr_action(obj_map, location);
2292 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2293 action_list_t::reverse_iterator rit;
2294 for (rit = list->rbegin(); rit != list->rend(); rit++)
2295 if ((*rit)->is_unlock() || (*rit)->is_wait())
2300 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2302 ModelAction *parent = get_last_action(tid);
2304 parent = get_thread(tid)->get_creation();
2309 * Returns the clock vector for a given thread.
2310 * @param tid The thread whose clock vector we want
2311 * @return Desired clock vector
2313 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2315 return get_parent_action(tid)->get_cv();
2319 * Resolve a set of Promises with a current write. The set is provided in the
2320 * Node corresponding to @a write.
2321 * @param write The ModelAction that is fulfilling Promises
2322 * @return True if promises were resolved; false otherwise
2324 bool ModelChecker::resolve_promises(ModelAction *write)
2326 bool resolved = false;
2327 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2329 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2330 Promise *promise = (*promises)[promise_index];
2331 if (write->get_node()->get_promise(i)) {
2332 ModelAction *read = promise->get_action();
2333 if (read->is_rmw()) {
2334 mo_graph->addRMWEdge(write, read);
2336 read_from(read, write);
2337 //First fix up the modification order for actions that happened
2339 r_modification_order(read, write);
2340 //Next fix up the modification order for actions that happened
2342 post_r_modification_order(read, write);
2343 //Make sure the promise's value matches the write's value
2344 ASSERT(promise->get_value() == write->get_value());
2347 promises->erase(promises->begin() + promise_index);
2348 actions_to_check.push_back(read);
2355 //Check whether reading these writes has made threads unable to
2358 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2359 ModelAction *read=actions_to_check[i];
2360 mo_check_promises(read->get_tid(), write, read);
2367 * Compute the set of promises that could potentially be satisfied by this
2368 * action. Note that the set computation actually appears in the Node, not in
2370 * @param curr The ModelAction that may satisfy promises
2372 void ModelChecker::compute_promises(ModelAction *curr)
2374 for (unsigned int i = 0; i < promises->size(); i++) {
2375 Promise *promise = (*promises)[i];
2376 const ModelAction *act = promise->get_action();
2377 if (!act->happens_before(curr) &&
2379 !act->could_synchronize_with(curr) &&
2380 !act->same_thread(curr) &&
2381 act->get_location() == curr->get_location() &&
2382 promise->get_value() == curr->get_value()) {
2383 curr->get_node()->set_promise(i, act->is_rmw());
2388 /** Checks promises in response to change in ClockVector Threads. */
2389 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2391 for (unsigned int i = 0; i < promises->size(); i++) {
2392 Promise *promise = (*promises)[i];
2393 const ModelAction *act = promise->get_action();
2394 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2395 merge_cv->synchronized_since(act)) {
2396 if (promise->eliminate_thread(tid)) {
2397 //Promise has failed
2398 priv->failed_promise = true;
2405 void ModelChecker::check_promises_thread_disabled()
2407 for (unsigned int i = 0; i < promises->size(); i++) {
2408 Promise *promise = (*promises)[i];
2409 if (promise->has_failed()) {
2410 priv->failed_promise = true;
2417 * @brief Checks promises in response to addition to modification order for
2422 * pthread is the thread that performed the read that created the promise
2424 * pread is the read that created the promise
2426 * pwrite is either the first write to same location as pread by
2427 * pthread that is sequenced after pread or the write read by the
2428 * first read to the same location as pread by pthread that is
2429 * sequenced after pread.
2431 * 1. If tid=pthread, then we check what other threads are reachable
2432 * through the mod order starting with pwrite. Those threads cannot
2433 * perform a write that will resolve the promise due to modification
2434 * order constraints.
2436 * 2. If the tid is not pthread, we check whether pwrite can reach the
2437 * action write through the modification order. If so, that thread
2438 * cannot perform a future write that will resolve the promise due to
2439 * modificatin order constraints.
2441 * @param tid The thread that either read from the model action write, or
2442 * actually did the model action write.
2444 * @param write The ModelAction representing the relevant write.
2445 * @param read The ModelAction that reads a promised write, or NULL otherwise.
2447 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write, const ModelAction *read)
2449 void *location = write->get_location();
2450 for (unsigned int i = 0; i < promises->size(); i++) {
2451 Promise *promise = (*promises)[i];
2452 const ModelAction *act = promise->get_action();
2454 // Is this promise on the same location?
2455 if (act->get_location() != location)
2458 // same thread as the promise
2459 if (act->get_tid() == tid) {
2460 // make sure that the reader of this write happens after the promise
2461 if ((read == NULL) || (promise->get_action()->happens_before(read))) {
2462 // do we have a pwrite for the promise, if not, set it
2463 if (promise->get_write() == NULL) {
2464 promise->set_write(write);
2465 // The pwrite cannot happen before the promise
2466 if (write->happens_before(act) && (write != act)) {
2467 priv->failed_promise = true;
2472 if (mo_graph->checkPromise(write, promise)) {
2473 priv->failed_promise = true;
2479 // Don't do any lookups twice for the same thread
2480 if (!promise->thread_is_available(tid))
2483 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2484 if (promise->eliminate_thread(tid)) {
2485 priv->failed_promise = true;
2493 * Compute the set of writes that may break the current pending release
2494 * sequence. This information is extracted from previou release sequence
2497 * @param curr The current ModelAction. Must be a release sequence fixup
2500 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2502 if (pending_rel_seqs->empty())
2505 struct release_seq *pending = pending_rel_seqs->back();
2506 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2507 const ModelAction *write = pending->writes[i];
2508 curr->get_node()->add_relseq_break(write);
2511 /* NULL means don't break the sequence; just synchronize */
2512 curr->get_node()->add_relseq_break(NULL);
2516 * Build up an initial set of all past writes that this 'read' action may read
2517 * from. This set is determined by the clock vector's "happens before"
2519 * @param curr is the current ModelAction that we are exploring; it must be a
2522 void ModelChecker::build_reads_from_past(ModelAction *curr)
2524 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2526 ASSERT(curr->is_read());
2528 ModelAction *last_sc_write = NULL;
2530 if (curr->is_seqcst())
2531 last_sc_write = get_last_seq_cst_write(curr);
2533 /* Iterate over all threads */
2534 for (i = 0; i < thrd_lists->size(); i++) {
2535 /* Iterate over actions in thread, starting from most recent */
2536 action_list_t *list = &(*thrd_lists)[i];
2537 action_list_t::reverse_iterator rit;
2538 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2539 ModelAction *act = *rit;
2541 /* Only consider 'write' actions */
2542 if (!act->is_write() || act == curr)
2545 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2546 bool allow_read = true;
2548 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2550 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2554 curr->get_node()->add_read_from(act);
2556 /* Include at most one act per-thread that "happens before" curr */
2557 if (act->happens_before(curr))
2562 if (DBG_ENABLED()) {
2563 model_print("Reached read action:\n");
2565 model_print("Printing may_read_from\n");
2566 curr->get_node()->print_may_read_from();
2567 model_print("End printing may_read_from\n");
2571 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2574 /* UNINIT actions don't have a Node, and they never sleep */
2575 if (write->is_uninitialized())
2577 Node *prevnode = write->get_node()->get_parent();
2579 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2580 if (write->is_release() && thread_sleep)
2582 if (!write->is_rmw()) {
2585 if (write->get_reads_from() == NULL)
2587 write = write->get_reads_from();
2592 * @brief Create a new action representing an uninitialized atomic
2593 * @param location The memory location of the atomic object
2594 * @return A pointer to a new ModelAction
2596 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2598 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2599 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2600 act->create_cv(NULL);
2604 static void print_list(action_list_t *list)
2606 action_list_t::iterator it;
2608 model_print("---------------------------------------------------------------------\n");
2610 unsigned int hash = 0;
2612 for (it = list->begin(); it != list->end(); it++) {
2614 hash = hash^(hash<<3)^((*it)->hash());
2616 model_print("HASH %u\n", hash);
2617 model_print("---------------------------------------------------------------------\n");
2620 #if SUPPORT_MOD_ORDER_DUMP
2621 void ModelChecker::dumpGraph(char *filename) const
2624 sprintf(buffer, "%s.dot", filename);
2625 FILE *file = fopen(buffer, "w");
2626 fprintf(file, "digraph %s {\n", filename);
2627 mo_graph->dumpNodes(file);
2628 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2630 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2631 ModelAction *action = *it;
2632 if (action->is_read()) {
2633 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2634 if (action->get_reads_from() != NULL)
2635 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2637 if (thread_array[action->get_tid()] != NULL) {
2638 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2641 thread_array[action->get_tid()] = action;
2643 fprintf(file, "}\n");
2644 model_free(thread_array);
2649 /** @brief Prints an execution trace summary. */
2650 void ModelChecker::print_summary() const
2652 #if SUPPORT_MOD_ORDER_DUMP
2654 char buffername[100];
2655 sprintf(buffername, "exec%04u", stats.num_total);
2656 mo_graph->dumpGraphToFile(buffername);
2657 sprintf(buffername, "graph%04u", stats.num_total);
2658 dumpGraph(buffername);
2661 model_print("Execution %d:", stats.num_total);
2662 if (isfeasibleprefix())
2665 print_infeasibility(" INFEASIBLE");
2666 print_list(action_trace);
2671 * Add a Thread to the system for the first time. Should only be called once
2673 * @param t The Thread to add
2675 void ModelChecker::add_thread(Thread *t)
2677 thread_map->put(id_to_int(t->get_id()), t);
2678 scheduler->add_thread(t);
2682 * Removes a thread from the scheduler.
2683 * @param the thread to remove.
2685 void ModelChecker::remove_thread(Thread *t)
2687 scheduler->remove_thread(t);
2691 * @brief Get a Thread reference by its ID
2692 * @param tid The Thread's ID
2693 * @return A Thread reference
2695 Thread * ModelChecker::get_thread(thread_id_t tid) const
2697 return thread_map->get(id_to_int(tid));
2701 * @brief Get a reference to the Thread in which a ModelAction was executed
2702 * @param act The ModelAction
2703 * @return A Thread reference
2705 Thread * ModelChecker::get_thread(const ModelAction *act) const
2707 return get_thread(act->get_tid());
2711 * @brief Check if a Thread is currently enabled
2712 * @param t The Thread to check
2713 * @return True if the Thread is currently enabled
2715 bool ModelChecker::is_enabled(Thread *t) const
2717 return scheduler->is_enabled(t);
2721 * @brief Check if a Thread is currently enabled
2722 * @param tid The ID of the Thread to check
2723 * @return True if the Thread is currently enabled
2725 bool ModelChecker::is_enabled(thread_id_t tid) const
2727 return scheduler->is_enabled(tid);
2731 * Switch from a user-context to the "master thread" context (a.k.a. system
2732 * context). This switch is made with the intention of exploring a particular
2733 * model-checking action (described by a ModelAction object). Must be called
2734 * from a user-thread context.
2736 * @param act The current action that will be explored. May be NULL only if
2737 * trace is exiting via an assertion (see ModelChecker::set_assert and
2738 * ModelChecker::has_asserted).
2739 * @return Return the value returned by the current action
2741 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2744 Thread *old = thread_current();
2745 set_current_action(act);
2746 old->set_state(THREAD_READY);
2747 if (Thread::swap(old, &system_context) < 0) {
2748 perror("swap threads");
2751 return old->get_return_value();
2755 * Takes the next step in the execution, if possible.
2756 * @param curr The current step to take
2757 * @return Returns true (success) if a step was taken and false otherwise.
2759 bool ModelChecker::take_step(ModelAction *curr)
2764 Thread *curr_thrd = get_thread(curr);
2765 ASSERT(curr_thrd->get_state() == THREAD_READY);
2767 curr = check_current_action(curr);
2769 /* Infeasible -> don't take any more steps */
2770 if (is_infeasible())
2772 else if (isfeasibleprefix() && have_bug_reports()) {
2777 if (params.bound != 0)
2778 if (priv->used_sequence_numbers > params.bound)
2781 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2782 scheduler->remove_thread(curr_thrd);
2784 Thread *next_thrd = get_next_thread(curr);
2785 next_thrd = scheduler->next_thread(next_thrd);
2787 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2788 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2791 * Launch end-of-execution release sequence fixups only when there are:
2793 * (1) no more user threads to run (or when execution replay chooses
2794 * the 'model_thread')
2795 * (2) pending release sequences
2796 * (3) pending assertions (i.e., data races)
2797 * (4) no pending promises
2799 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2800 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2801 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2802 pending_rel_seqs->size());
2803 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2804 std::memory_order_seq_cst, NULL, VALUE_NONE,
2806 set_current_action(fixup);
2810 /* next_thrd == NULL -> don't take any more steps */
2814 next_thrd->set_state(THREAD_RUNNING);
2816 if (next_thrd->get_pending() != NULL) {
2817 /* restart a pending action */
2818 set_current_action(next_thrd->get_pending());
2819 next_thrd->set_pending(NULL);
2820 next_thrd->set_state(THREAD_READY);
2824 /* Return false only if swap fails with an error */
2825 return (Thread::swap(&system_context, next_thrd) == 0);
2828 /** Wrapper to run the user's main function, with appropriate arguments */
2829 void user_main_wrapper(void *)
2831 user_main(model->params.argc, model->params.argv);
2834 /** @brief Run ModelChecker for the user program */
2835 void ModelChecker::run()
2839 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2843 /* Run user thread up to its first action */
2844 scheduler->next_thread(t);
2845 Thread::swap(&system_context, t);
2847 /* Wait for all threads to complete */
2848 while (take_step(priv->current_action));
2849 } while (next_execution());