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 snapshotObject->backTrackBeforeStep(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;
177 /** @return The currently executing Thread. */
178 Thread * ModelChecker::get_current_thread() const
180 return scheduler->get_current_thread();
183 /** @return a sequence number for a new ModelAction */
184 modelclock_t ModelChecker::get_next_seq_num()
186 return ++priv->used_sequence_numbers;
189 Node * ModelChecker::get_curr_node() const
191 return node_stack->get_head();
195 * @brief Choose the next thread to execute.
197 * This function chooses the next thread that should execute. It can force the
198 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
199 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
200 * The model-checker may have no preference regarding the next thread (i.e.,
201 * when exploring a new execution ordering), in which case this will return
203 * @param curr The current ModelAction. This action might guide the choice of
205 * @return The next thread to run. If the model-checker has no preference, NULL.
207 Thread * ModelChecker::get_next_thread(ModelAction *curr)
212 /* Do not split atomic actions. */
214 return thread_current();
215 /* The THREAD_CREATE action points to the created Thread */
216 else if (curr->get_type() == THREAD_CREATE)
217 return (Thread *)curr->get_location();
220 /* Have we completed exploring the preselected path? */
224 /* Else, we are trying to replay an execution */
225 ModelAction *next = node_stack->get_next()->get_action();
227 if (next == diverge) {
228 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
229 earliest_diverge = diverge;
231 Node *nextnode = next->get_node();
232 Node *prevnode = nextnode->get_parent();
233 scheduler->update_sleep_set(prevnode);
235 /* Reached divergence point */
236 if (nextnode->increment_misc()) {
237 /* The next node will try to satisfy a different misc_index values. */
238 tid = next->get_tid();
239 node_stack->pop_restofstack(2);
240 } else if (nextnode->increment_promise()) {
241 /* The next node will try to satisfy a different set of promises. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_read_from()) {
245 /* The next node will read from a different value. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_future_value()) {
249 /* The next node will try to read from a different future value. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_relseq_break()) {
253 /* The next node will try to resolve a release sequence differently */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
258 /* Make a different thread execute for next step */
259 scheduler->add_sleep(get_thread(next->get_tid()));
260 tid = prevnode->get_next_backtrack();
261 /* Make sure the backtracked thread isn't sleeping. */
262 node_stack->pop_restofstack(1);
263 if (diverge == earliest_diverge) {
264 earliest_diverge = prevnode->get_action();
267 /* The correct sleep set is in the parent node. */
270 DEBUG("*** Divergence point ***\n");
274 tid = next->get_tid();
276 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
277 ASSERT(tid != THREAD_ID_T_NONE);
278 return thread_map->get(id_to_int(tid));
282 * We need to know what the next actions of all threads in the sleep
283 * set will be. This method computes them and stores the actions at
284 * the corresponding thread object's pending action.
287 void ModelChecker::execute_sleep_set()
289 for (unsigned int i = 0; i < get_num_threads(); i++) {
290 thread_id_t tid = int_to_id(i);
291 Thread *thr = get_thread(tid);
292 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
293 thr->set_state(THREAD_RUNNING);
294 scheduler->next_thread(thr);
295 Thread::swap(&system_context, thr);
296 priv->current_action->set_sleep_flag();
297 thr->set_pending(priv->current_action);
302 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
304 for (unsigned int i = 0; i < get_num_threads(); i++) {
305 Thread *thr = get_thread(int_to_id(i));
306 if (scheduler->is_sleep_set(thr)) {
307 ModelAction *pending_act = thr->get_pending();
308 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
309 //Remove this thread from sleep set
310 scheduler->remove_sleep(thr);
315 /** @brief Alert the model-checker that an incorrectly-ordered
316 * synchronization was made */
317 void ModelChecker::set_bad_synchronization()
319 priv->bad_synchronization = true;
322 bool ModelChecker::has_asserted() const
324 return priv->asserted;
327 void ModelChecker::set_assert()
329 priv->asserted = true;
333 * Check if we are in a deadlock. Should only be called at the end of an
334 * execution, although it should not give false positives in the middle of an
335 * execution (there should be some ENABLED thread).
337 * @return True if program is in a deadlock; false otherwise
339 bool ModelChecker::is_deadlocked() const
341 bool blocking_threads = false;
342 for (unsigned int i = 0; i < get_num_threads(); i++) {
343 thread_id_t tid = int_to_id(i);
346 Thread *t = get_thread(tid);
347 if (!t->is_model_thread() && t->get_pending())
348 blocking_threads = true;
350 return blocking_threads;
354 * Check if this is a complete execution. That is, have all thread completed
355 * execution (rather than exiting because sleep sets have forced a redundant
358 * @return True if the execution is complete.
360 bool ModelChecker::is_complete_execution() const
362 for (unsigned int i = 0; i < get_num_threads(); i++)
363 if (is_enabled(int_to_id(i)))
369 * @brief Assert a bug in the executing program.
371 * Use this function to assert any sort of bug in the user program. If the
372 * current trace is feasible (actually, a prefix of some feasible execution),
373 * then this execution will be aborted, printing the appropriate message. If
374 * the current trace is not yet feasible, the error message will be stashed and
375 * printed if the execution ever becomes feasible.
377 * @param msg Descriptive message for the bug (do not include newline char)
378 * @return True if bug is immediately-feasible
380 bool ModelChecker::assert_bug(const char *msg)
382 priv->bugs.push_back(new bug_message(msg));
384 if (isfeasibleprefix()) {
392 * @brief Assert a bug in the executing program, asserted by a user thread
393 * @see ModelChecker::assert_bug
394 * @param msg Descriptive message for the bug (do not include newline char)
396 void ModelChecker::assert_user_bug(const char *msg)
398 /* If feasible bug, bail out now */
400 switch_to_master(NULL);
403 /** @return True, if any bugs have been reported for this execution */
404 bool ModelChecker::have_bug_reports() const
406 return priv->bugs.size() != 0;
409 /** @brief Print bug report listing for this execution (if any bugs exist) */
410 void ModelChecker::print_bugs() const
412 if (have_bug_reports()) {
413 model_print("Bug report: %zu bug%s detected\n",
415 priv->bugs.size() > 1 ? "s" : "");
416 for (unsigned int i = 0; i < priv->bugs.size(); i++)
417 priv->bugs[i]->print();
422 * @brief Record end-of-execution stats
424 * Must be run when exiting an execution. Records various stats.
425 * @see struct execution_stats
427 void ModelChecker::record_stats()
430 if (!isfeasibleprefix())
431 stats.num_infeasible++;
432 else if (have_bug_reports())
433 stats.num_buggy_executions++;
434 else if (is_complete_execution())
435 stats.num_complete++;
437 stats.num_redundant++;
440 /** @brief Print execution stats */
441 void ModelChecker::print_stats() const
443 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
444 model_print("Number of redundant executions: %d\n", stats.num_redundant);
445 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
446 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
447 model_print("Total executions: %d\n", stats.num_total);
448 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
452 * @brief End-of-exeuction print
453 * @param printbugs Should any existing bugs be printed?
455 void ModelChecker::print_execution(bool printbugs) const
457 print_program_output();
459 if (DBG_ENABLED() || params.verbose) {
460 model_print("Earliest divergence point since last feasible execution:\n");
461 if (earliest_diverge)
462 earliest_diverge->print();
464 model_print("(Not set)\n");
470 /* Don't print invalid bugs */
479 * Queries the model-checker for more executions to explore and, if one
480 * exists, resets the model-checker state to execute a new execution.
482 * @return If there are more executions to explore, return true. Otherwise,
485 bool ModelChecker::next_execution()
488 /* Is this execution a feasible execution that's worth bug-checking? */
489 bool complete = isfeasibleprefix() && (is_complete_execution() ||
492 /* End-of-execution bug checks */
495 assert_bug("Deadlock detected");
503 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
504 print_execution(complete);
506 clear_program_output();
509 earliest_diverge = NULL;
511 if ((diverge = get_next_backtrack()) == NULL)
515 model_print("Next execution will diverge at:\n");
519 reset_to_initial_state();
523 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
525 switch (act->get_type()) {
530 /* Optimization: relaxed operations don't need backtracking */
531 if (act->is_relaxed())
533 /* linear search: from most recent to oldest */
534 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
535 action_list_t::reverse_iterator rit;
536 for (rit = list->rbegin(); rit != list->rend(); rit++) {
537 ModelAction *prev = *rit;
538 if (prev->could_synchronize_with(act))
544 case ATOMIC_TRYLOCK: {
545 /* linear search: from most recent to oldest */
546 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
547 action_list_t::reverse_iterator rit;
548 for (rit = list->rbegin(); rit != list->rend(); rit++) {
549 ModelAction *prev = *rit;
550 if (act->is_conflicting_lock(prev))
555 case ATOMIC_UNLOCK: {
556 /* linear search: from most recent to oldest */
557 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
558 action_list_t::reverse_iterator rit;
559 for (rit = list->rbegin(); rit != list->rend(); rit++) {
560 ModelAction *prev = *rit;
561 if (!act->same_thread(prev) && prev->is_failed_trylock())
567 /* linear search: from most recent to oldest */
568 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
569 action_list_t::reverse_iterator rit;
570 for (rit = list->rbegin(); rit != list->rend(); rit++) {
571 ModelAction *prev = *rit;
572 if (!act->same_thread(prev) && prev->is_failed_trylock())
574 if (!act->same_thread(prev) && prev->is_notify())
580 case ATOMIC_NOTIFY_ALL:
581 case ATOMIC_NOTIFY_ONE: {
582 /* linear search: from most recent to oldest */
583 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
584 action_list_t::reverse_iterator rit;
585 for (rit = list->rbegin(); rit != list->rend(); rit++) {
586 ModelAction *prev = *rit;
587 if (!act->same_thread(prev) && prev->is_wait())
598 /** This method finds backtracking points where we should try to
599 * reorder the parameter ModelAction against.
601 * @param the ModelAction to find backtracking points for.
603 void ModelChecker::set_backtracking(ModelAction *act)
605 Thread *t = get_thread(act);
606 ModelAction *prev = get_last_conflict(act);
610 Node *node = prev->get_node()->get_parent();
612 int low_tid, high_tid;
613 if (node->is_enabled(t)) {
614 low_tid = id_to_int(act->get_tid());
615 high_tid = low_tid + 1;
618 high_tid = get_num_threads();
621 for (int i = low_tid; i < high_tid; i++) {
622 thread_id_t tid = int_to_id(i);
624 /* Make sure this thread can be enabled here. */
625 if (i >= node->get_num_threads())
628 /* Don't backtrack into a point where the thread is disabled or sleeping. */
629 if (node->enabled_status(tid) != THREAD_ENABLED)
632 /* Check if this has been explored already */
633 if (node->has_been_explored(tid))
636 /* See if fairness allows */
637 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
639 for (int t = 0; t < node->get_num_threads(); t++) {
640 thread_id_t tother = int_to_id(t);
641 if (node->is_enabled(tother) && node->has_priority(tother)) {
649 /* Cache the latest backtracking point */
650 set_latest_backtrack(prev);
652 /* If this is a new backtracking point, mark the tree */
653 if (!node->set_backtrack(tid))
655 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
656 id_to_int(prev->get_tid()),
657 id_to_int(t->get_id()));
666 * @brief Cache the a backtracking point as the "most recent", if eligible
668 * Note that this does not prepare the NodeStack for this backtracking
669 * operation, it only caches the action on a per-execution basis
671 * @param act The operation at which we should explore a different next action
672 * (i.e., backtracking point)
673 * @return True, if this action is now the most recent backtracking point;
676 bool ModelChecker::set_latest_backtrack(ModelAction *act)
678 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
679 priv->next_backtrack = act;
686 * Returns last backtracking point. The model checker will explore a different
687 * path for this point in the next execution.
688 * @return The ModelAction at which the next execution should diverge.
690 ModelAction * ModelChecker::get_next_backtrack()
692 ModelAction *next = priv->next_backtrack;
693 priv->next_backtrack = NULL;
698 * Processes a read or rmw model action.
699 * @param curr is the read model action to process.
700 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
701 * @return True if processing this read updates the mo_graph.
703 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
705 uint64_t value = VALUE_NONE;
706 bool updated = false;
708 const ModelAction *reads_from = curr->get_node()->get_read_from();
709 if (reads_from != NULL) {
710 mo_graph->startChanges();
712 value = reads_from->get_value();
713 bool r_status = false;
715 if (!second_part_of_rmw) {
716 check_recency(curr, reads_from);
717 r_status = r_modification_order(curr, reads_from);
721 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
722 mo_graph->rollbackChanges();
723 priv->too_many_reads = false;
727 read_from(curr, reads_from);
728 mo_graph->commitChanges();
729 mo_check_promises(curr->get_tid(), reads_from);
732 } else if (!second_part_of_rmw) {
733 /* Read from future value */
734 value = curr->get_node()->get_future_value();
735 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
736 curr->set_read_from(NULL);
737 Promise *valuepromise = new Promise(curr, value, expiration);
738 promises->push_back(valuepromise);
740 get_thread(curr)->set_return_value(value);
746 * Processes a lock, trylock, or unlock model action. @param curr is
747 * the read model action to process.
749 * The try lock operation checks whether the lock is taken. If not,
750 * it falls to the normal lock operation case. If so, it returns
753 * The lock operation has already been checked that it is enabled, so
754 * it just grabs the lock and synchronizes with the previous unlock.
756 * The unlock operation has to re-enable all of the threads that are
757 * waiting on the lock.
759 * @return True if synchronization was updated; false otherwise
761 bool ModelChecker::process_mutex(ModelAction *curr)
763 std::mutex *mutex = NULL;
764 struct std::mutex_state *state = NULL;
766 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
767 mutex = (std::mutex *)curr->get_location();
768 state = mutex->get_state();
769 } else if (curr->is_wait()) {
770 mutex = (std::mutex *)curr->get_value();
771 state = mutex->get_state();
774 switch (curr->get_type()) {
775 case ATOMIC_TRYLOCK: {
776 bool success = !state->islocked;
777 curr->set_try_lock(success);
779 get_thread(curr)->set_return_value(0);
782 get_thread(curr)->set_return_value(1);
784 //otherwise fall into the lock case
786 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
787 assert_bug("Lock access before initialization");
788 state->islocked = true;
789 ModelAction *unlock = get_last_unlock(curr);
790 //synchronize with the previous unlock statement
791 if (unlock != NULL) {
792 curr->synchronize_with(unlock);
797 case ATOMIC_UNLOCK: {
799 state->islocked = false;
800 //wake up the other threads
801 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
802 //activate all the waiting threads
803 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
804 scheduler->wake(get_thread(*rit));
811 state->islocked = false;
812 //wake up the other threads
813 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
814 //activate all the waiting threads
815 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
816 scheduler->wake(get_thread(*rit));
819 //check whether we should go to sleep or not...simulate spurious failures
820 if (curr->get_node()->get_misc() == 0) {
821 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
823 scheduler->sleep(get_current_thread());
827 case ATOMIC_NOTIFY_ALL: {
828 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
829 //activate all the waiting threads
830 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
831 scheduler->wake(get_thread(*rit));
836 case ATOMIC_NOTIFY_ONE: {
837 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
838 int wakeupthread = curr->get_node()->get_misc();
839 action_list_t::iterator it = waiters->begin();
840 advance(it, wakeupthread);
841 scheduler->wake(get_thread(*it));
853 * Process a write ModelAction
854 * @param curr The ModelAction to process
855 * @return True if the mo_graph was updated or promises were resolved
857 bool ModelChecker::process_write(ModelAction *curr)
859 bool updated_mod_order = w_modification_order(curr);
860 bool updated_promises = resolve_promises(curr);
862 if (promises->size() == 0) {
863 for (unsigned int i = 0; i < futurevalues->size(); i++) {
864 struct PendingFutureValue pfv = (*futurevalues)[i];
865 //Do more ambitious checks now that mo is more complete
866 if (mo_may_allow(pfv.writer, pfv.act) &&
867 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number() + params.maxfuturedelay))
868 set_latest_backtrack(pfv.act);
870 futurevalues->resize(0);
873 mo_graph->commitChanges();
874 mo_check_promises(curr->get_tid(), curr);
876 get_thread(curr)->set_return_value(VALUE_NONE);
877 return updated_mod_order || updated_promises;
881 * Process a fence ModelAction
882 * @param curr The ModelAction to process
883 * @return True if synchronization was updated
885 bool ModelChecker::process_fence(ModelAction *curr)
888 * fence-relaxed: no-op
889 * fence-release: only log the occurence (not in this function), for
890 * use in later synchronization
891 * fence-acquire (this function): search for hypothetical release
894 bool updated = false;
895 if (curr->is_acquire()) {
896 action_list_t *list = action_trace;
897 action_list_t::reverse_iterator rit;
898 /* Find X : is_read(X) && X --sb-> curr */
899 for (rit = list->rbegin(); rit != list->rend(); rit++) {
900 ModelAction *act = *rit;
903 if (act->get_tid() != curr->get_tid())
905 /* Stop at the beginning of the thread */
906 if (act->is_thread_start())
908 /* Stop once we reach a prior fence-acquire */
909 if (act->is_fence() && act->is_acquire())
913 /* read-acquire will find its own release sequences */
914 if (act->is_acquire())
917 /* Establish hypothetical release sequences */
918 rel_heads_list_t release_heads;
919 get_release_seq_heads(curr, act, &release_heads);
920 for (unsigned int i = 0; i < release_heads.size(); i++)
921 if (!curr->synchronize_with(release_heads[i]))
922 set_bad_synchronization();
923 if (release_heads.size() != 0)
931 * @brief Process the current action for thread-related activity
933 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
934 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
935 * synchronization, etc. This function is a no-op for non-THREAD actions
936 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
938 * @param curr The current action
939 * @return True if synchronization was updated or a thread completed
941 bool ModelChecker::process_thread_action(ModelAction *curr)
943 bool updated = false;
945 switch (curr->get_type()) {
946 case THREAD_CREATE: {
947 Thread *th = (Thread *)curr->get_location();
948 th->set_creation(curr);
952 Thread *blocking = (Thread *)curr->get_location();
953 ModelAction *act = get_last_action(blocking->get_id());
954 curr->synchronize_with(act);
955 updated = true; /* trigger rel-seq checks */
958 case THREAD_FINISH: {
959 Thread *th = get_thread(curr);
960 while (!th->wait_list_empty()) {
961 ModelAction *act = th->pop_wait_list();
962 scheduler->wake(get_thread(act));
965 updated = true; /* trigger rel-seq checks */
969 check_promises(curr->get_tid(), NULL, curr->get_cv());
980 * @brief Process the current action for release sequence fixup activity
982 * Performs model-checker release sequence fixups for the current action,
983 * forcing a single pending release sequence to break (with a given, potential
984 * "loose" write) or to complete (i.e., synchronize). If a pending release
985 * sequence forms a complete release sequence, then we must perform the fixup
986 * synchronization, mo_graph additions, etc.
988 * @param curr The current action; must be a release sequence fixup action
989 * @param work_queue The work queue to which to add work items as they are
992 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
994 const ModelAction *write = curr->get_node()->get_relseq_break();
995 struct release_seq *sequence = pending_rel_seqs->back();
996 pending_rel_seqs->pop_back();
998 ModelAction *acquire = sequence->acquire;
999 const ModelAction *rf = sequence->rf;
1000 const ModelAction *release = sequence->release;
1004 ASSERT(release->same_thread(rf));
1006 if (write == NULL) {
1008 * @todo Forcing a synchronization requires that we set
1009 * modification order constraints. For instance, we can't allow
1010 * a fixup sequence in which two separate read-acquire
1011 * operations read from the same sequence, where the first one
1012 * synchronizes and the other doesn't. Essentially, we can't
1013 * allow any writes to insert themselves between 'release' and
1017 /* Must synchronize */
1018 if (!acquire->synchronize_with(release)) {
1019 set_bad_synchronization();
1022 /* Re-check all pending release sequences */
1023 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1024 /* Re-check act for mo_graph edges */
1025 work_queue->push_back(MOEdgeWorkEntry(acquire));
1027 /* propagate synchronization to later actions */
1028 action_list_t::reverse_iterator rit = action_trace->rbegin();
1029 for (; (*rit) != acquire; rit++) {
1030 ModelAction *propagate = *rit;
1031 if (acquire->happens_before(propagate)) {
1032 propagate->synchronize_with(acquire);
1033 /* Re-check 'propagate' for mo_graph edges */
1034 work_queue->push_back(MOEdgeWorkEntry(propagate));
1038 /* Break release sequence with new edges:
1039 * release --mo--> write --mo--> rf */
1040 mo_graph->addEdge(release, write);
1041 mo_graph->addEdge(write, rf);
1044 /* See if we have realized a data race */
1049 * Initialize the current action by performing one or more of the following
1050 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1051 * in the NodeStack, manipulating backtracking sets, allocating and
1052 * initializing clock vectors, and computing the promises to fulfill.
1054 * @param curr The current action, as passed from the user context; may be
1055 * freed/invalidated after the execution of this function, with a different
1056 * action "returned" its place (pass-by-reference)
1057 * @return True if curr is a newly-explored action; false otherwise
1059 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1061 ModelAction *newcurr;
1063 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1064 newcurr = process_rmw(*curr);
1067 if (newcurr->is_rmw())
1068 compute_promises(newcurr);
1074 (*curr)->set_seq_number(get_next_seq_num());
1076 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1078 /* First restore type and order in case of RMW operation */
1079 if ((*curr)->is_rmwr())
1080 newcurr->copy_typeandorder(*curr);
1082 ASSERT((*curr)->get_location() == newcurr->get_location());
1083 newcurr->copy_from_new(*curr);
1085 /* Discard duplicate ModelAction; use action from NodeStack */
1088 /* Always compute new clock vector */
1089 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1092 return false; /* Action was explored previously */
1096 /* Always compute new clock vector */
1097 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1099 /* Assign most recent release fence */
1100 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1103 * Perform one-time actions when pushing new ModelAction onto
1106 if (newcurr->is_write())
1107 compute_promises(newcurr);
1108 else if (newcurr->is_relseq_fixup())
1109 compute_relseq_breakwrites(newcurr);
1110 else if (newcurr->is_wait())
1111 newcurr->get_node()->set_misc_max(2);
1112 else if (newcurr->is_notify_one()) {
1113 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1115 return true; /* This was a new ModelAction */
1120 * @brief Establish reads-from relation between two actions
1122 * Perform basic operations involved with establishing a concrete rf relation,
1123 * including setting the ModelAction data and checking for release sequences.
1125 * @param act The action that is reading (must be a read)
1126 * @param rf The action from which we are reading (must be a write)
1128 * @return True if this read established synchronization
1130 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1132 act->set_read_from(rf);
1133 if (rf != NULL && act->is_acquire()) {
1134 rel_heads_list_t release_heads;
1135 get_release_seq_heads(act, act, &release_heads);
1136 int num_heads = release_heads.size();
1137 for (unsigned int i = 0; i < release_heads.size(); i++)
1138 if (!act->synchronize_with(release_heads[i])) {
1139 set_bad_synchronization();
1142 return num_heads > 0;
1148 * @brief Check whether a model action is enabled.
1150 * Checks whether a lock or join operation would be successful (i.e., is the
1151 * lock already locked, or is the joined thread already complete). If not, put
1152 * the action in a waiter list.
1154 * @param curr is the ModelAction to check whether it is enabled.
1155 * @return a bool that indicates whether the action is enabled.
1157 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1158 if (curr->is_lock()) {
1159 std::mutex *lock = (std::mutex *)curr->get_location();
1160 struct std::mutex_state *state = lock->get_state();
1161 if (state->islocked) {
1162 //Stick the action in the appropriate waiting queue
1163 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1166 } else if (curr->get_type() == THREAD_JOIN) {
1167 Thread *blocking = (Thread *)curr->get_location();
1168 if (!blocking->is_complete()) {
1169 blocking->push_wait_list(curr);
1178 * Stores the ModelAction for the current thread action. Call this
1179 * immediately before switching from user- to system-context to pass
1180 * data between them.
1181 * @param act The ModelAction created by the user-thread action
1183 void ModelChecker::set_current_action(ModelAction *act) {
1184 priv->current_action = act;
1188 * This is the heart of the model checker routine. It performs model-checking
1189 * actions corresponding to a given "current action." Among other processes, it
1190 * calculates reads-from relationships, updates synchronization clock vectors,
1191 * forms a memory_order constraints graph, and handles replay/backtrack
1192 * execution when running permutations of previously-observed executions.
1194 * @param curr The current action to process
1195 * @return The ModelAction that is actually executed; may be different than
1196 * curr; may be NULL, if the current action is not enabled to run
1198 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1201 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1203 if (!check_action_enabled(curr)) {
1204 /* Make the execution look like we chose to run this action
1205 * much later, when a lock/join can succeed */
1206 get_current_thread()->set_pending(curr);
1207 scheduler->sleep(get_current_thread());
1211 bool newly_explored = initialize_curr_action(&curr);
1217 wake_up_sleeping_actions(curr);
1219 /* Add the action to lists before any other model-checking tasks */
1220 if (!second_part_of_rmw)
1221 add_action_to_lists(curr);
1223 /* Build may_read_from set for newly-created actions */
1224 if (newly_explored && curr->is_read())
1225 build_reads_from_past(curr);
1227 /* Initialize work_queue with the "current action" work */
1228 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1229 while (!work_queue.empty() && !has_asserted()) {
1230 WorkQueueEntry work = work_queue.front();
1231 work_queue.pop_front();
1233 switch (work.type) {
1234 case WORK_CHECK_CURR_ACTION: {
1235 ModelAction *act = work.action;
1236 bool update = false; /* update this location's release seq's */
1237 bool update_all = false; /* update all release seq's */
1239 if (process_thread_action(curr))
1242 if (act->is_read() && process_read(act, second_part_of_rmw))
1245 if (act->is_write() && process_write(act))
1248 if (act->is_fence() && process_fence(act))
1251 if (act->is_mutex_op() && process_mutex(act))
1254 if (act->is_relseq_fixup())
1255 process_relseq_fixup(curr, &work_queue);
1258 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1260 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1263 case WORK_CHECK_RELEASE_SEQ:
1264 resolve_release_sequences(work.location, &work_queue);
1266 case WORK_CHECK_MO_EDGES: {
1267 /** @todo Complete verification of work_queue */
1268 ModelAction *act = work.action;
1269 bool updated = false;
1271 if (act->is_read()) {
1272 const ModelAction *rf = act->get_reads_from();
1273 if (rf != NULL && r_modification_order(act, rf))
1276 if (act->is_write()) {
1277 if (w_modification_order(act))
1280 mo_graph->commitChanges();
1283 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1292 check_curr_backtracking(curr);
1293 set_backtracking(curr);
1297 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1299 Node *currnode = curr->get_node();
1300 Node *parnode = currnode->get_parent();
1302 if ((parnode && !parnode->backtrack_empty()) ||
1303 !currnode->misc_empty() ||
1304 !currnode->read_from_empty() ||
1305 !currnode->future_value_empty() ||
1306 !currnode->promise_empty() ||
1307 !currnode->relseq_break_empty()) {
1308 set_latest_backtrack(curr);
1312 bool ModelChecker::promises_expired() const
1314 for (unsigned int i = 0; i < promises->size(); i++) {
1315 Promise *promise = (*promises)[i];
1316 if (promise->get_expiration() < priv->used_sequence_numbers)
1323 * This is the strongest feasibility check available.
1324 * @return whether the current trace (partial or complete) must be a prefix of
1327 bool ModelChecker::isfeasibleprefix() const
1329 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1333 * Returns whether the current completed trace is feasible, except for pending
1334 * release sequences.
1336 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1338 if (DBG_ENABLED() && promises->size() != 0)
1339 DEBUG("Infeasible: unrevolved promises\n");
1341 return !is_infeasible() && promises->size() == 0;
1345 * Check if the current partial trace is infeasible. Does not check any
1346 * end-of-execution flags, which might rule out the execution. Thus, this is
1347 * useful only for ruling an execution as infeasible.
1348 * @return whether the current partial trace is infeasible.
1350 bool ModelChecker::is_infeasible() const
1352 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1353 DEBUG("Infeasible: RMW violation\n");
1355 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1359 * Check If the current partial trace is infeasible, while ignoring
1360 * infeasibility related to 2 RMW's reading from the same store. It does not
1361 * check end-of-execution feasibility.
1362 * @see ModelChecker::is_infeasible
1363 * @return whether the current partial trace is infeasible, ignoring multiple
1364 * RMWs reading from the same store.
1366 bool ModelChecker::is_infeasible_ignoreRMW() const
1368 if (DBG_ENABLED()) {
1369 if (mo_graph->checkForCycles())
1370 DEBUG("Infeasible: modification order cycles\n");
1371 if (priv->failed_promise)
1372 DEBUG("Infeasible: failed promise\n");
1373 if (priv->too_many_reads)
1374 DEBUG("Infeasible: too many reads\n");
1375 if (priv->bad_synchronization)
1376 DEBUG("Infeasible: bad synchronization ordering\n");
1377 if (promises_expired())
1378 DEBUG("Infeasible: promises expired\n");
1380 return mo_graph->checkForCycles() || priv->failed_promise ||
1381 priv->too_many_reads || priv->bad_synchronization ||
1385 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1386 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1387 ModelAction *lastread = get_last_action(act->get_tid());
1388 lastread->process_rmw(act);
1389 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1390 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1391 mo_graph->commitChanges();
1397 * Checks whether a thread has read from the same write for too many times
1398 * without seeing the effects of a later write.
1401 * 1) there must a different write that we could read from that would satisfy the modification order,
1402 * 2) we must have read from the same value in excess of maxreads times, and
1403 * 3) that other write must have been in the reads_from set for maxreads times.
1405 * If so, we decide that the execution is no longer feasible.
1407 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1409 if (params.maxreads != 0) {
1410 if (curr->get_node()->get_read_from_size() <= 1)
1412 //Must make sure that execution is currently feasible... We could
1413 //accidentally clear by rolling back
1414 if (is_infeasible())
1416 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1417 int tid = id_to_int(curr->get_tid());
1420 if ((int)thrd_lists->size() <= tid)
1422 action_list_t *list = &(*thrd_lists)[tid];
1424 action_list_t::reverse_iterator rit = list->rbegin();
1425 /* Skip past curr */
1426 for (; (*rit) != curr; rit++)
1428 /* go past curr now */
1431 action_list_t::reverse_iterator ritcopy = rit;
1432 //See if we have enough reads from the same value
1434 for (; count < params.maxreads; rit++, count++) {
1435 if (rit == list->rend())
1437 ModelAction *act = *rit;
1438 if (!act->is_read())
1441 if (act->get_reads_from() != rf)
1443 if (act->get_node()->get_read_from_size() <= 1)
1446 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1448 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1450 /* Need a different write */
1454 /* Test to see whether this is a feasible write to read from */
1455 mo_graph->startChanges();
1456 r_modification_order(curr, write);
1457 bool feasiblereadfrom = !is_infeasible();
1458 mo_graph->rollbackChanges();
1460 if (!feasiblereadfrom)
1464 bool feasiblewrite = true;
1465 //new we need to see if this write works for everyone
1467 for (int loop = count; loop > 0; loop--, rit++) {
1468 ModelAction *act = *rit;
1469 bool foundvalue = false;
1470 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1471 if (act->get_node()->get_read_from_at(j) == write) {
1477 feasiblewrite = false;
1481 if (feasiblewrite) {
1482 priv->too_many_reads = true;
1490 * Updates the mo_graph with the constraints imposed from the current
1493 * Basic idea is the following: Go through each other thread and find
1494 * the lastest action that happened before our read. Two cases:
1496 * (1) The action is a write => that write must either occur before
1497 * the write we read from or be the write we read from.
1499 * (2) The action is a read => the write that that action read from
1500 * must occur before the write we read from or be the same write.
1502 * @param curr The current action. Must be a read.
1503 * @param rf The action that curr reads from. Must be a write.
1504 * @return True if modification order edges were added; false otherwise
1506 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1508 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1511 ASSERT(curr->is_read());
1513 /* Last SC fence in the current thread */
1514 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1516 /* Iterate over all threads */
1517 for (i = 0; i < thrd_lists->size(); i++) {
1518 /* Last SC fence in thread i */
1519 ModelAction *last_sc_fence_thread_local = NULL;
1520 if (int_to_id((int)i) != curr->get_tid())
1521 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1523 /* Last SC fence in thread i, before last SC fence in current thread */
1524 ModelAction *last_sc_fence_thread_before = NULL;
1525 if (last_sc_fence_local)
1526 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1528 /* Iterate over actions in thread, starting from most recent */
1529 action_list_t *list = &(*thrd_lists)[i];
1530 action_list_t::reverse_iterator rit;
1531 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1532 ModelAction *act = *rit;
1534 if (act->is_write() && act != rf && act != curr) {
1535 /* C++, Section 29.3 statement 5 */
1536 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1537 *act < *last_sc_fence_thread_local) {
1538 mo_graph->addEdge(act, rf);
1542 /* C++, Section 29.3 statement 4 */
1543 else if (act->is_seqcst() && last_sc_fence_local &&
1544 *act < *last_sc_fence_local) {
1545 mo_graph->addEdge(act, rf);
1549 /* C++, Section 29.3 statement 6 */
1550 else if (last_sc_fence_thread_before &&
1551 *act < *last_sc_fence_thread_before) {
1552 mo_graph->addEdge(act, rf);
1559 * Include at most one act per-thread that "happens
1560 * before" curr. Don't consider reflexively.
1562 if (act->happens_before(curr) && act != curr) {
1563 if (act->is_write()) {
1565 mo_graph->addEdge(act, rf);
1569 const ModelAction *prevreadfrom = act->get_reads_from();
1570 //if the previous read is unresolved, keep going...
1571 if (prevreadfrom == NULL)
1574 if (rf != prevreadfrom) {
1575 mo_graph->addEdge(prevreadfrom, rf);
1587 /** This method fixes up the modification order when we resolve a
1588 * promises. The basic problem is that actions that occur after the
1589 * read curr could not property add items to the modification order
1592 * So for each thread, we find the earliest item that happens after
1593 * the read curr. This is the item we have to fix up with additional
1594 * constraints. If that action is write, we add a MO edge between
1595 * the Action rf and that action. If the action is a read, we add a
1596 * MO edge between the Action rf, and whatever the read accessed.
1598 * @param curr is the read ModelAction that we are fixing up MO edges for.
1599 * @param rf is the write ModelAction that curr reads from.
1602 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1604 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1606 ASSERT(curr->is_read());
1608 /* Iterate over all threads */
1609 for (i = 0; i < thrd_lists->size(); i++) {
1610 /* Iterate over actions in thread, starting from most recent */
1611 action_list_t *list = &(*thrd_lists)[i];
1612 action_list_t::reverse_iterator rit;
1613 ModelAction *lastact = NULL;
1615 /* Find last action that happens after curr that is either not curr or a rmw */
1616 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1617 ModelAction *act = *rit;
1618 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1624 /* Include at most one act per-thread that "happens before" curr */
1625 if (lastact != NULL) {
1626 if (lastact == curr) {
1627 //Case 1: The resolved read is a RMW, and we need to make sure
1628 //that the write portion of the RMW mod order after rf
1630 mo_graph->addEdge(rf, lastact);
1631 } else if (lastact->is_read()) {
1632 //Case 2: The resolved read is a normal read and the next
1633 //operation is a read, and we need to make sure the value read
1634 //is mod ordered after rf
1636 const ModelAction *postreadfrom = lastact->get_reads_from();
1637 if (postreadfrom != NULL && rf != postreadfrom)
1638 mo_graph->addEdge(rf, postreadfrom);
1640 //Case 3: The resolved read is a normal read and the next
1641 //operation is a write, and we need to make sure that the
1642 //write is mod ordered after rf
1644 mo_graph->addEdge(rf, lastact);
1652 * Updates the mo_graph with the constraints imposed from the current write.
1654 * Basic idea is the following: Go through each other thread and find
1655 * the lastest action that happened before our write. Two cases:
1657 * (1) The action is a write => that write must occur before
1660 * (2) The action is a read => the write that that action read from
1661 * must occur before the current write.
1663 * This method also handles two other issues:
1665 * (I) Sequential Consistency: Making sure that if the current write is
1666 * seq_cst, that it occurs after the previous seq_cst write.
1668 * (II) Sending the write back to non-synchronizing reads.
1670 * @param curr The current action. Must be a write.
1671 * @return True if modification order edges were added; false otherwise
1673 bool ModelChecker::w_modification_order(ModelAction *curr)
1675 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1678 ASSERT(curr->is_write());
1680 if (curr->is_seqcst()) {
1681 /* We have to at least see the last sequentially consistent write,
1682 so we are initialized. */
1683 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1684 if (last_seq_cst != NULL) {
1685 mo_graph->addEdge(last_seq_cst, curr);
1690 /* Last SC fence in the current thread */
1691 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1693 /* Iterate over all threads */
1694 for (i = 0; i < thrd_lists->size(); i++) {
1695 /* Last SC fence in thread i, before last SC fence in current thread */
1696 ModelAction *last_sc_fence_thread_before = NULL;
1697 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1698 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1700 /* Iterate over actions in thread, starting from most recent */
1701 action_list_t *list = &(*thrd_lists)[i];
1702 action_list_t::reverse_iterator rit;
1703 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1704 ModelAction *act = *rit;
1707 * 1) If RMW and it actually read from something, then we
1708 * already have all relevant edges, so just skip to next
1711 * 2) If RMW and it didn't read from anything, we should
1712 * whatever edge we can get to speed up convergence.
1714 * 3) If normal write, we need to look at earlier actions, so
1715 * continue processing list.
1717 if (curr->is_rmw()) {
1718 if (curr->get_reads_from() != NULL)
1726 /* C++, Section 29.3 statement 7 */
1727 if (last_sc_fence_thread_before && act->is_write() &&
1728 *act < *last_sc_fence_thread_before) {
1729 mo_graph->addEdge(act, curr);
1735 * Include at most one act per-thread that "happens
1738 if (act->happens_before(curr)) {
1740 * Note: if act is RMW, just add edge:
1742 * The following edge should be handled elsewhere:
1743 * readfrom(act) --mo--> act
1745 if (act->is_write())
1746 mo_graph->addEdge(act, curr);
1747 else if (act->is_read()) {
1748 //if previous read accessed a null, just keep going
1749 if (act->get_reads_from() == NULL)
1751 mo_graph->addEdge(act->get_reads_from(), curr);
1755 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1756 !act->same_thread(curr)) {
1757 /* We have an action that:
1758 (1) did not happen before us
1759 (2) is a read and we are a write
1760 (3) cannot synchronize with us
1761 (4) is in a different thread
1763 that read could potentially read from our write. Note that
1764 these checks are overly conservative at this point, we'll
1765 do more checks before actually removing the
1769 if (thin_air_constraint_may_allow(curr, act)) {
1770 if (!is_infeasible() ||
1771 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1772 struct PendingFutureValue pfv = {curr, act};
1773 futurevalues->push_back(pfv);
1783 /** Arbitrary reads from the future are not allowed. Section 29.3
1784 * part 9 places some constraints. This method checks one result of constraint
1785 * constraint. Others require compiler support. */
1786 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1788 if (!writer->is_rmw())
1791 if (!reader->is_rmw())
1794 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1795 if (search == reader)
1797 if (search->get_tid() == reader->get_tid() &&
1798 search->happens_before(reader))
1806 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1807 * some constraints. This method checks one the following constraint (others
1808 * require compiler support):
1810 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1812 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1814 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1816 /* Iterate over all threads */
1817 for (i = 0; i < thrd_lists->size(); i++) {
1818 const ModelAction *write_after_read = NULL;
1820 /* Iterate over actions in thread, starting from most recent */
1821 action_list_t *list = &(*thrd_lists)[i];
1822 action_list_t::reverse_iterator rit;
1823 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1824 ModelAction *act = *rit;
1826 /* Don't disallow due to act == reader */
1827 if (!reader->happens_before(act) || reader == act)
1829 else if (act->is_write())
1830 write_after_read = act;
1831 else if (act->is_read() && act->get_reads_from() != NULL)
1832 write_after_read = act->get_reads_from();
1835 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1842 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1843 * The ModelAction under consideration is expected to be taking part in
1844 * release/acquire synchronization as an object of the "reads from" relation.
1845 * Note that this can only provide release sequence support for RMW chains
1846 * which do not read from the future, as those actions cannot be traced until
1847 * their "promise" is fulfilled. Similarly, we may not even establish the
1848 * presence of a release sequence with certainty, as some modification order
1849 * constraints may be decided further in the future. Thus, this function
1850 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1851 * and a boolean representing certainty.
1853 * @param rf The action that might be part of a release sequence. Must be a
1855 * @param release_heads A pass-by-reference style return parameter. After
1856 * execution of this function, release_heads will contain the heads of all the
1857 * relevant release sequences, if any exists with certainty
1858 * @param pending A pass-by-reference style return parameter which is only used
1859 * when returning false (i.e., uncertain). Returns most information regarding
1860 * an uncertain release sequence, including any write operations that might
1861 * break the sequence.
1862 * @return true, if the ModelChecker is certain that release_heads is complete;
1865 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1866 rel_heads_list_t *release_heads,
1867 struct release_seq *pending) const
1869 /* Only check for release sequences if there are no cycles */
1870 if (mo_graph->checkForCycles())
1874 ASSERT(rf->is_write());
1876 if (rf->is_release())
1877 release_heads->push_back(rf);
1878 else if (rf->get_last_fence_release())
1879 release_heads->push_back(rf->get_last_fence_release());
1881 break; /* End of RMW chain */
1883 /** @todo Need to be smarter here... In the linux lock
1884 * example, this will run to the beginning of the program for
1886 /** @todo The way to be smarter here is to keep going until 1
1887 * thread has a release preceded by an acquire and you've seen
1890 /* acq_rel RMW is a sufficient stopping condition */
1891 if (rf->is_acquire() && rf->is_release())
1892 return true; /* complete */
1894 rf = rf->get_reads_from();
1897 /* read from future: need to settle this later */
1899 return false; /* incomplete */
1902 if (rf->is_release())
1903 return true; /* complete */
1905 /* else relaxed write
1906 * - check for fence-release in the same thread (29.8, stmt. 3)
1907 * - check modification order for contiguous subsequence
1908 * -> rf must be same thread as release */
1910 const ModelAction *fence_release = rf->get_last_fence_release();
1911 /* Synchronize with a fence-release unconditionally; we don't need to
1912 * find any more "contiguous subsequence..." for it */
1914 release_heads->push_back(fence_release);
1916 int tid = id_to_int(rf->get_tid());
1917 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1918 action_list_t *list = &(*thrd_lists)[tid];
1919 action_list_t::const_reverse_iterator rit;
1921 /* Find rf in the thread list */
1922 rit = std::find(list->rbegin(), list->rend(), rf);
1923 ASSERT(rit != list->rend());
1925 /* Find the last {write,fence}-release */
1926 for (; rit != list->rend(); rit++) {
1927 if (fence_release && *(*rit) < *fence_release)
1929 if ((*rit)->is_release())
1932 if (rit == list->rend()) {
1933 /* No write-release in this thread */
1934 return true; /* complete */
1935 } else if (fence_release && *(*rit) < *fence_release) {
1936 /* The fence-release is more recent (and so, "stronger") than
1937 * the most recent write-release */
1938 return true; /* complete */
1939 } /* else, need to establish contiguous release sequence */
1940 ModelAction *release = *rit;
1942 ASSERT(rf->same_thread(release));
1944 pending->writes.clear();
1946 bool certain = true;
1947 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1948 if (id_to_int(rf->get_tid()) == (int)i)
1950 list = &(*thrd_lists)[i];
1952 /* Can we ensure no future writes from this thread may break
1953 * the release seq? */
1954 bool future_ordered = false;
1956 ModelAction *last = get_last_action(int_to_id(i));
1957 Thread *th = get_thread(int_to_id(i));
1958 if ((last && rf->happens_before(last)) ||
1961 future_ordered = true;
1963 ASSERT(!th->is_model_thread() || future_ordered);
1965 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1966 const ModelAction *act = *rit;
1967 /* Reach synchronization -> this thread is complete */
1968 if (act->happens_before(release))
1970 if (rf->happens_before(act)) {
1971 future_ordered = true;
1975 /* Only non-RMW writes can break release sequences */
1976 if (!act->is_write() || act->is_rmw())
1979 /* Check modification order */
1980 if (mo_graph->checkReachable(rf, act)) {
1981 /* rf --mo--> act */
1982 future_ordered = true;
1985 if (mo_graph->checkReachable(act, release))
1986 /* act --mo--> release */
1988 if (mo_graph->checkReachable(release, act) &&
1989 mo_graph->checkReachable(act, rf)) {
1990 /* release --mo-> act --mo--> rf */
1991 return true; /* complete */
1993 /* act may break release sequence */
1994 pending->writes.push_back(act);
1997 if (!future_ordered)
1998 certain = false; /* This thread is uncertain */
2002 release_heads->push_back(release);
2003 pending->writes.clear();
2005 pending->release = release;
2012 * An interface for getting the release sequence head(s) with which a
2013 * given ModelAction must synchronize. This function only returns a non-empty
2014 * result when it can locate a release sequence head with certainty. Otherwise,
2015 * it may mark the internal state of the ModelChecker so that it will handle
2016 * the release sequence at a later time, causing @a acquire to update its
2017 * synchronization at some later point in execution.
2019 * @param acquire The 'acquire' action that may synchronize with a release
2021 * @param read The read action that may read from a release sequence; this may
2022 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2023 * when 'acquire' is a fence-acquire)
2024 * @param release_heads A pass-by-reference return parameter. Will be filled
2025 * with the head(s) of the release sequence(s), if they exists with certainty.
2026 * @see ModelChecker::release_seq_heads
2028 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2029 ModelAction *read, rel_heads_list_t *release_heads)
2031 const ModelAction *rf = read->get_reads_from();
2032 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2033 sequence->acquire = acquire;
2034 sequence->read = read;
2036 if (!release_seq_heads(rf, release_heads, sequence)) {
2037 /* add act to 'lazy checking' list */
2038 pending_rel_seqs->push_back(sequence);
2040 snapshot_free(sequence);
2045 * Attempt to resolve all stashed operations that might synchronize with a
2046 * release sequence for a given location. This implements the "lazy" portion of
2047 * determining whether or not a release sequence was contiguous, since not all
2048 * modification order information is present at the time an action occurs.
2050 * @param location The location/object that should be checked for release
2051 * sequence resolutions. A NULL value means to check all locations.
2052 * @param work_queue The work queue to which to add work items as they are
2054 * @return True if any updates occurred (new synchronization, new mo_graph
2057 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2059 bool updated = false;
2060 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2061 while (it != pending_rel_seqs->end()) {
2062 struct release_seq *pending = *it;
2063 ModelAction *acquire = pending->acquire;
2064 const ModelAction *read = pending->read;
2066 /* Only resolve sequences on the given location, if provided */
2067 if (location && read->get_location() != location) {
2072 const ModelAction *rf = read->get_reads_from();
2073 rel_heads_list_t release_heads;
2075 complete = release_seq_heads(rf, &release_heads, pending);
2076 for (unsigned int i = 0; i < release_heads.size(); i++) {
2077 if (!acquire->has_synchronized_with(release_heads[i])) {
2078 if (acquire->synchronize_with(release_heads[i]))
2081 set_bad_synchronization();
2086 /* Re-check all pending release sequences */
2087 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2088 /* Re-check read-acquire for mo_graph edges */
2089 if (acquire->is_read())
2090 work_queue->push_back(MOEdgeWorkEntry(acquire));
2092 /* propagate synchronization to later actions */
2093 action_list_t::reverse_iterator rit = action_trace->rbegin();
2094 for (; (*rit) != acquire; rit++) {
2095 ModelAction *propagate = *rit;
2096 if (acquire->happens_before(propagate)) {
2097 propagate->synchronize_with(acquire);
2098 /* Re-check 'propagate' for mo_graph edges */
2099 work_queue->push_back(MOEdgeWorkEntry(propagate));
2104 it = pending_rel_seqs->erase(it);
2105 snapshot_free(pending);
2111 // If we resolved promises or data races, see if we have realized a data race.
2118 * Performs various bookkeeping operations for the current ModelAction. For
2119 * instance, adds action to the per-object, per-thread action vector and to the
2120 * action trace list of all thread actions.
2122 * @param act is the ModelAction to add.
2124 void ModelChecker::add_action_to_lists(ModelAction *act)
2126 int tid = id_to_int(act->get_tid());
2127 ModelAction *uninit = NULL;
2129 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2130 if (list->empty() && act->is_atomic_var()) {
2131 uninit = new_uninitialized_action(act->get_location());
2132 uninit_id = id_to_int(uninit->get_tid());
2133 list->push_back(uninit);
2135 list->push_back(act);
2137 action_trace->push_back(act);
2139 action_trace->push_front(uninit);
2141 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2142 if (tid >= (int)vec->size())
2143 vec->resize(priv->next_thread_id);
2144 (*vec)[tid].push_back(act);
2146 (*vec)[uninit_id].push_front(uninit);
2148 if ((int)thrd_last_action->size() <= tid)
2149 thrd_last_action->resize(get_num_threads());
2150 (*thrd_last_action)[tid] = act;
2152 (*thrd_last_action)[uninit_id] = uninit;
2154 if (act->is_fence() && act->is_release()) {
2155 if ((int)thrd_last_fence_release->size() <= tid)
2156 thrd_last_fence_release->resize(get_num_threads());
2157 (*thrd_last_fence_release)[tid] = act;
2160 if (act->is_wait()) {
2161 void *mutex_loc = (void *) act->get_value();
2162 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2164 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2165 if (tid >= (int)vec->size())
2166 vec->resize(priv->next_thread_id);
2167 (*vec)[tid].push_back(act);
2172 * @brief Get the last action performed by a particular Thread
2173 * @param tid The thread ID of the Thread in question
2174 * @return The last action in the thread
2176 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2178 int threadid = id_to_int(tid);
2179 if (threadid < (int)thrd_last_action->size())
2180 return (*thrd_last_action)[id_to_int(tid)];
2186 * @brief Get the last fence release performed by a particular Thread
2187 * @param tid The thread ID of the Thread in question
2188 * @return The last fence release in the thread, if one exists; NULL otherwise
2190 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2192 int threadid = id_to_int(tid);
2193 if (threadid < (int)thrd_last_fence_release->size())
2194 return (*thrd_last_fence_release)[id_to_int(tid)];
2200 * Gets the last memory_order_seq_cst write (in the total global sequence)
2201 * performed on a particular object (i.e., memory location), not including the
2203 * @param curr The current ModelAction; also denotes the object location to
2205 * @return The last seq_cst write
2207 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2209 void *location = curr->get_location();
2210 action_list_t *list = get_safe_ptr_action(obj_map, location);
2211 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2212 action_list_t::reverse_iterator rit;
2213 for (rit = list->rbegin(); rit != list->rend(); rit++)
2214 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2220 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2221 * performed in a particular thread, prior to a particular fence.
2222 * @param tid The ID of the thread to check
2223 * @param before_fence The fence from which to begin the search; if NULL, then
2224 * search for the most recent fence in the thread.
2225 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2227 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2229 /* All fences should have NULL location */
2230 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2231 action_list_t::reverse_iterator rit = list->rbegin();
2234 for (; rit != list->rend(); rit++)
2235 if (*rit == before_fence)
2238 ASSERT(*rit == before_fence);
2242 for (; rit != list->rend(); rit++)
2243 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2249 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2250 * location). This function identifies the mutex according to the current
2251 * action, which is presumed to perform on the same mutex.
2252 * @param curr The current ModelAction; also denotes the object location to
2254 * @return The last unlock operation
2256 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2258 void *location = curr->get_location();
2259 action_list_t *list = get_safe_ptr_action(obj_map, location);
2260 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2261 action_list_t::reverse_iterator rit;
2262 for (rit = list->rbegin(); rit != list->rend(); rit++)
2263 if ((*rit)->is_unlock() || (*rit)->is_wait())
2268 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2270 ModelAction *parent = get_last_action(tid);
2272 parent = get_thread(tid)->get_creation();
2277 * Returns the clock vector for a given thread.
2278 * @param tid The thread whose clock vector we want
2279 * @return Desired clock vector
2281 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2283 return get_parent_action(tid)->get_cv();
2287 * Resolve a set of Promises with a current write. The set is provided in the
2288 * Node corresponding to @a write.
2289 * @param write The ModelAction that is fulfilling Promises
2290 * @return True if promises were resolved; false otherwise
2292 bool ModelChecker::resolve_promises(ModelAction *write)
2294 bool resolved = false;
2295 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2297 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2298 Promise *promise = (*promises)[promise_index];
2299 if (write->get_node()->get_promise(i)) {
2300 ModelAction *read = promise->get_action();
2301 if (read->is_rmw()) {
2302 mo_graph->addRMWEdge(write, read);
2304 read_from(read, write);
2305 //First fix up the modification order for actions that happened
2307 r_modification_order(read, write);
2308 //Next fix up the modification order for actions that happened
2310 post_r_modification_order(read, write);
2311 //Make sure the promise's value matches the write's value
2312 ASSERT(promise->get_value() == write->get_value());
2315 promises->erase(promises->begin() + promise_index);
2316 threads_to_check.push_back(read->get_tid());
2323 //Check whether reading these writes has made threads unable to
2326 for (unsigned int i = 0; i < threads_to_check.size(); i++)
2327 mo_check_promises(threads_to_check[i], write);
2333 * Compute the set of promises that could potentially be satisfied by this
2334 * action. Note that the set computation actually appears in the Node, not in
2336 * @param curr The ModelAction that may satisfy promises
2338 void ModelChecker::compute_promises(ModelAction *curr)
2340 for (unsigned int i = 0; i < promises->size(); i++) {
2341 Promise *promise = (*promises)[i];
2342 const ModelAction *act = promise->get_action();
2343 if (!act->happens_before(curr) &&
2345 !act->could_synchronize_with(curr) &&
2346 !act->same_thread(curr) &&
2347 act->get_location() == curr->get_location() &&
2348 promise->get_value() == curr->get_value()) {
2349 curr->get_node()->set_promise(i, act->is_rmw());
2354 /** Checks promises in response to change in ClockVector Threads. */
2355 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2357 for (unsigned int i = 0; i < promises->size(); i++) {
2358 Promise *promise = (*promises)[i];
2359 const ModelAction *act = promise->get_action();
2360 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2361 merge_cv->synchronized_since(act)) {
2362 if (promise->increment_threads(tid)) {
2363 //Promise has failed
2364 priv->failed_promise = true;
2371 void ModelChecker::check_promises_thread_disabled() {
2372 for (unsigned int i = 0; i < promises->size(); i++) {
2373 Promise *promise = (*promises)[i];
2374 if (promise->check_promise()) {
2375 priv->failed_promise = true;
2381 /** Checks promises in response to addition to modification order for threads.
2383 * pthread is the thread that performed the read that created the promise
2385 * pread is the read that created the promise
2387 * pwrite is either the first write to same location as pread by
2388 * pthread that is sequenced after pread or the value read by the
2389 * first read to the same lcoation as pread by pthread that is
2390 * sequenced after pread..
2392 * 1. If tid=pthread, then we check what other threads are reachable
2393 * through the mode order starting with pwrite. Those threads cannot
2394 * perform a write that will resolve the promise due to modification
2395 * order constraints.
2397 * 2. If the tid is not pthread, we check whether pwrite can reach the
2398 * action write through the modification order. If so, that thread
2399 * cannot perform a future write that will resolve the promise due to
2400 * modificatin order constraints.
2402 * @param tid The thread that either read from the model action
2403 * write, or actually did the model action write.
2405 * @param write The ModelAction representing the relevant write.
2407 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write)
2409 void *location = write->get_location();
2410 for (unsigned int i = 0; i < promises->size(); i++) {
2411 Promise *promise = (*promises)[i];
2412 const ModelAction *act = promise->get_action();
2414 //Is this promise on the same location?
2415 if (act->get_location() != location)
2418 //same thread as the promise
2419 if (act->get_tid() == tid) {
2421 //do we have a pwrite for the promise, if not, set it
2422 if (promise->get_write() == NULL) {
2423 promise->set_write(write);
2424 //The pwrite cannot happen before the promise
2425 if (write->happens_before(act) && (write != act)) {
2426 priv->failed_promise = true;
2430 if (mo_graph->checkPromise(write, promise)) {
2431 priv->failed_promise = true;
2436 //Don't do any lookups twice for the same thread
2437 if (promise->has_sync_thread(tid))
2440 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2441 if (promise->increment_threads(tid)) {
2442 priv->failed_promise = true;
2450 * Compute the set of writes that may break the current pending release
2451 * sequence. This information is extracted from previou release sequence
2454 * @param curr The current ModelAction. Must be a release sequence fixup
2457 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2459 if (pending_rel_seqs->empty())
2462 struct release_seq *pending = pending_rel_seqs->back();
2463 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2464 const ModelAction *write = pending->writes[i];
2465 curr->get_node()->add_relseq_break(write);
2468 /* NULL means don't break the sequence; just synchronize */
2469 curr->get_node()->add_relseq_break(NULL);
2473 * Build up an initial set of all past writes that this 'read' action may read
2474 * from. This set is determined by the clock vector's "happens before"
2476 * @param curr is the current ModelAction that we are exploring; it must be a
2479 void ModelChecker::build_reads_from_past(ModelAction *curr)
2481 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2483 ASSERT(curr->is_read());
2485 ModelAction *last_sc_write = NULL;
2487 if (curr->is_seqcst())
2488 last_sc_write = get_last_seq_cst_write(curr);
2490 /* Iterate over all threads */
2491 for (i = 0; i < thrd_lists->size(); i++) {
2492 /* Iterate over actions in thread, starting from most recent */
2493 action_list_t *list = &(*thrd_lists)[i];
2494 action_list_t::reverse_iterator rit;
2495 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2496 ModelAction *act = *rit;
2498 /* Only consider 'write' actions */
2499 if (!act->is_write() || act == curr)
2502 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2503 bool allow_read = true;
2505 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2507 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2511 curr->get_node()->add_read_from(act);
2513 /* Include at most one act per-thread that "happens before" curr */
2514 if (act->happens_before(curr))
2519 if (DBG_ENABLED()) {
2520 model_print("Reached read action:\n");
2522 model_print("Printing may_read_from\n");
2523 curr->get_node()->print_may_read_from();
2524 model_print("End printing may_read_from\n");
2528 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2531 /* UNINIT actions don't have a Node, and they never sleep */
2532 if (write->is_uninitialized())
2534 Node *prevnode = write->get_node()->get_parent();
2536 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2537 if (write->is_release() && thread_sleep)
2539 if (!write->is_rmw()) {
2542 if (write->get_reads_from() == NULL)
2544 write = write->get_reads_from();
2549 * @brief Create a new action representing an uninitialized atomic
2550 * @param location The memory location of the atomic object
2551 * @return A pointer to a new ModelAction
2553 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2555 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2556 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2557 act->create_cv(NULL);
2561 static void print_list(action_list_t *list, int exec_num = -1)
2563 action_list_t::iterator it;
2565 model_print("---------------------------------------------------------------------\n");
2567 model_print("Execution %d:\n", exec_num);
2569 unsigned int hash = 0;
2571 for (it = list->begin(); it != list->end(); it++) {
2573 hash = hash^(hash<<3)^((*it)->hash());
2575 model_print("HASH %u\n", hash);
2576 model_print("---------------------------------------------------------------------\n");
2579 #if SUPPORT_MOD_ORDER_DUMP
2580 void ModelChecker::dumpGraph(char *filename) const
2583 sprintf(buffer, "%s.dot", filename);
2584 FILE *file = fopen(buffer, "w");
2585 fprintf(file, "digraph %s {\n", filename);
2586 mo_graph->dumpNodes(file);
2587 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2589 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2590 ModelAction *action = *it;
2591 if (action->is_read()) {
2592 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2593 if (action->get_reads_from() != NULL)
2594 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2596 if (thread_array[action->get_tid()] != NULL) {
2597 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2600 thread_array[action->get_tid()] = action;
2602 fprintf(file, "}\n");
2603 model_free(thread_array);
2608 /** @brief Prints an execution trace summary. */
2609 void ModelChecker::print_summary() const
2611 #if SUPPORT_MOD_ORDER_DUMP
2613 char buffername[100];
2614 sprintf(buffername, "exec%04u", stats.num_total);
2615 mo_graph->dumpGraphToFile(buffername);
2616 sprintf(buffername, "graph%04u", stats.num_total);
2617 dumpGraph(buffername);
2620 if (!isfeasibleprefix())
2621 model_print("INFEASIBLE EXECUTION!\n");
2622 print_list(action_trace, stats.num_total);
2627 * Add a Thread to the system for the first time. Should only be called once
2629 * @param t The Thread to add
2631 void ModelChecker::add_thread(Thread *t)
2633 thread_map->put(id_to_int(t->get_id()), t);
2634 scheduler->add_thread(t);
2638 * Removes a thread from the scheduler.
2639 * @param the thread to remove.
2641 void ModelChecker::remove_thread(Thread *t)
2643 scheduler->remove_thread(t);
2647 * @brief Get a Thread reference by its ID
2648 * @param tid The Thread's ID
2649 * @return A Thread reference
2651 Thread * ModelChecker::get_thread(thread_id_t tid) const
2653 return thread_map->get(id_to_int(tid));
2657 * @brief Get a reference to the Thread in which a ModelAction was executed
2658 * @param act The ModelAction
2659 * @return A Thread reference
2661 Thread * ModelChecker::get_thread(ModelAction *act) const
2663 return get_thread(act->get_tid());
2667 * @brief Check if a Thread is currently enabled
2668 * @param t The Thread to check
2669 * @return True if the Thread is currently enabled
2671 bool ModelChecker::is_enabled(Thread *t) const
2673 return scheduler->is_enabled(t);
2677 * @brief Check if a Thread is currently enabled
2678 * @param tid The ID of the Thread to check
2679 * @return True if the Thread is currently enabled
2681 bool ModelChecker::is_enabled(thread_id_t tid) const
2683 return scheduler->is_enabled(tid);
2687 * Switch from a user-context to the "master thread" context (a.k.a. system
2688 * context). This switch is made with the intention of exploring a particular
2689 * model-checking action (described by a ModelAction object). Must be called
2690 * from a user-thread context.
2692 * @param act The current action that will be explored. May be NULL only if
2693 * trace is exiting via an assertion (see ModelChecker::set_assert and
2694 * ModelChecker::has_asserted).
2695 * @return Return the value returned by the current action
2697 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2700 Thread *old = thread_current();
2701 set_current_action(act);
2702 old->set_state(THREAD_READY);
2703 if (Thread::swap(old, &system_context) < 0) {
2704 perror("swap threads");
2707 return old->get_return_value();
2711 * Takes the next step in the execution, if possible.
2712 * @param curr The current step to take
2713 * @return Returns true (success) if a step was taken and false otherwise.
2715 bool ModelChecker::take_step(ModelAction *curr)
2720 Thread *curr_thrd = get_thread(curr);
2721 ASSERT(curr_thrd->get_state() == THREAD_READY);
2723 curr = check_current_action(curr);
2725 /* Infeasible -> don't take any more steps */
2726 if (is_infeasible())
2728 else if (isfeasibleprefix() && have_bug_reports()) {
2733 if (params.bound != 0)
2734 if (priv->used_sequence_numbers > params.bound)
2737 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2738 scheduler->remove_thread(curr_thrd);
2740 Thread *next_thrd = get_next_thread(curr);
2741 next_thrd = scheduler->next_thread(next_thrd);
2743 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2744 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2747 * Launch end-of-execution release sequence fixups only when there are:
2749 * (1) no more user threads to run (or when execution replay chooses
2750 * the 'model_thread')
2751 * (2) pending release sequences
2752 * (3) pending assertions (i.e., data races)
2753 * (4) no pending promises
2755 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2756 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2757 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2758 pending_rel_seqs->size());
2759 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2760 std::memory_order_seq_cst, NULL, VALUE_NONE,
2762 set_current_action(fixup);
2766 /* next_thrd == NULL -> don't take any more steps */
2770 next_thrd->set_state(THREAD_RUNNING);
2772 if (next_thrd->get_pending() != NULL) {
2773 /* restart a pending action */
2774 set_current_action(next_thrd->get_pending());
2775 next_thrd->set_pending(NULL);
2776 next_thrd->set_state(THREAD_READY);
2780 /* Return false only if swap fails with an error */
2781 return (Thread::swap(&system_context, next_thrd) == 0);
2784 /** Wrapper to run the user's main function, with appropriate arguments */
2785 void user_main_wrapper(void *)
2787 user_main(model->params.argc, model->params.argv);
2790 /** @brief Run ModelChecker for the user program */
2791 void ModelChecker::run()
2795 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2799 /* Run user thread up to its first action */
2800 scheduler->next_thread(t);
2801 Thread::swap(&system_context, t);
2803 /* Wait for all threads to complete */
2804 while (take_step(priv->current_action));
2805 } while (next_execution());