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 next Thread that must be executed. May be NULL if ModelChecker
1196 * makes no choice (e.g., according to replay execution, combining RMW actions,
1199 Thread * ModelChecker::check_current_action(ModelAction *curr)
1202 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1204 if (!check_action_enabled(curr)) {
1205 /* Make the execution look like we chose to run this action
1206 * much later, when a lock/join can succeed */
1207 get_current_thread()->set_pending(curr);
1208 scheduler->sleep(get_current_thread());
1209 return get_next_thread(NULL);
1212 bool newly_explored = initialize_curr_action(&curr);
1214 wake_up_sleeping_actions(curr);
1216 /* Add the action to lists before any other model-checking tasks */
1217 if (!second_part_of_rmw)
1218 add_action_to_lists(curr);
1220 /* Build may_read_from set for newly-created actions */
1221 if (newly_explored && curr->is_read())
1222 build_reads_from_past(curr);
1224 /* Initialize work_queue with the "current action" work */
1225 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1226 while (!work_queue.empty() && !has_asserted()) {
1227 WorkQueueEntry work = work_queue.front();
1228 work_queue.pop_front();
1230 switch (work.type) {
1231 case WORK_CHECK_CURR_ACTION: {
1232 ModelAction *act = work.action;
1233 bool update = false; /* update this location's release seq's */
1234 bool update_all = false; /* update all release seq's */
1236 if (process_thread_action(curr))
1239 if (act->is_read() && process_read(act, second_part_of_rmw))
1242 if (act->is_write() && process_write(act))
1245 if (act->is_fence() && process_fence(act))
1248 if (act->is_mutex_op() && process_mutex(act))
1251 if (act->is_relseq_fixup())
1252 process_relseq_fixup(curr, &work_queue);
1255 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1257 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1260 case WORK_CHECK_RELEASE_SEQ:
1261 resolve_release_sequences(work.location, &work_queue);
1263 case WORK_CHECK_MO_EDGES: {
1264 /** @todo Complete verification of work_queue */
1265 ModelAction *act = work.action;
1266 bool updated = false;
1268 if (act->is_read()) {
1269 const ModelAction *rf = act->get_reads_from();
1270 if (rf != NULL && r_modification_order(act, rf))
1273 if (act->is_write()) {
1274 if (w_modification_order(act))
1277 mo_graph->commitChanges();
1280 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1289 check_curr_backtracking(curr);
1290 set_backtracking(curr);
1291 return get_next_thread(curr);
1294 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1296 Node *currnode = curr->get_node();
1297 Node *parnode = currnode->get_parent();
1299 if ((parnode && !parnode->backtrack_empty()) ||
1300 !currnode->misc_empty() ||
1301 !currnode->read_from_empty() ||
1302 !currnode->future_value_empty() ||
1303 !currnode->promise_empty() ||
1304 !currnode->relseq_break_empty()) {
1305 set_latest_backtrack(curr);
1309 bool ModelChecker::promises_expired() const
1311 for (unsigned int i = 0; i < promises->size(); i++) {
1312 Promise *promise = (*promises)[i];
1313 if (promise->get_expiration() < priv->used_sequence_numbers)
1320 * This is the strongest feasibility check available.
1321 * @return whether the current trace (partial or complete) must be a prefix of
1324 bool ModelChecker::isfeasibleprefix() const
1326 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1330 * Returns whether the current completed trace is feasible, except for pending
1331 * release sequences.
1333 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1335 if (DBG_ENABLED() && promises->size() != 0)
1336 DEBUG("Infeasible: unrevolved promises\n");
1338 return !is_infeasible() && promises->size() == 0;
1342 * Check if the current partial trace is infeasible. Does not check any
1343 * end-of-execution flags, which might rule out the execution. Thus, this is
1344 * useful only for ruling an execution as infeasible.
1345 * @return whether the current partial trace is infeasible.
1347 bool ModelChecker::is_infeasible() const
1349 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1350 DEBUG("Infeasible: RMW violation\n");
1352 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1356 * Check If the current partial trace is infeasible, while ignoring
1357 * infeasibility related to 2 RMW's reading from the same store. It does not
1358 * check end-of-execution feasibility.
1359 * @see ModelChecker::is_infeasible
1360 * @return whether the current partial trace is infeasible, ignoring multiple
1361 * RMWs reading from the same store.
1363 bool ModelChecker::is_infeasible_ignoreRMW() const
1365 if (DBG_ENABLED()) {
1366 if (mo_graph->checkForCycles())
1367 DEBUG("Infeasible: modification order cycles\n");
1368 if (priv->failed_promise)
1369 DEBUG("Infeasible: failed promise\n");
1370 if (priv->too_many_reads)
1371 DEBUG("Infeasible: too many reads\n");
1372 if (priv->bad_synchronization)
1373 DEBUG("Infeasible: bad synchronization ordering\n");
1374 if (promises_expired())
1375 DEBUG("Infeasible: promises expired\n");
1377 return mo_graph->checkForCycles() || priv->failed_promise ||
1378 priv->too_many_reads || priv->bad_synchronization ||
1382 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1383 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1384 ModelAction *lastread = get_last_action(act->get_tid());
1385 lastread->process_rmw(act);
1386 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1387 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1388 mo_graph->commitChanges();
1394 * Checks whether a thread has read from the same write for too many times
1395 * without seeing the effects of a later write.
1398 * 1) there must a different write that we could read from that would satisfy the modification order,
1399 * 2) we must have read from the same value in excess of maxreads times, and
1400 * 3) that other write must have been in the reads_from set for maxreads times.
1402 * If so, we decide that the execution is no longer feasible.
1404 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1406 if (params.maxreads != 0) {
1407 if (curr->get_node()->get_read_from_size() <= 1)
1409 //Must make sure that execution is currently feasible... We could
1410 //accidentally clear by rolling back
1411 if (is_infeasible())
1413 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1414 int tid = id_to_int(curr->get_tid());
1417 if ((int)thrd_lists->size() <= tid)
1419 action_list_t *list = &(*thrd_lists)[tid];
1421 action_list_t::reverse_iterator rit = list->rbegin();
1422 /* Skip past curr */
1423 for (; (*rit) != curr; rit++)
1425 /* go past curr now */
1428 action_list_t::reverse_iterator ritcopy = rit;
1429 //See if we have enough reads from the same value
1431 for (; count < params.maxreads; rit++, count++) {
1432 if (rit == list->rend())
1434 ModelAction *act = *rit;
1435 if (!act->is_read())
1438 if (act->get_reads_from() != rf)
1440 if (act->get_node()->get_read_from_size() <= 1)
1443 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1445 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1447 /* Need a different write */
1451 /* Test to see whether this is a feasible write to read from */
1452 mo_graph->startChanges();
1453 r_modification_order(curr, write);
1454 bool feasiblereadfrom = !is_infeasible();
1455 mo_graph->rollbackChanges();
1457 if (!feasiblereadfrom)
1461 bool feasiblewrite = true;
1462 //new we need to see if this write works for everyone
1464 for (int loop = count; loop > 0; loop--, rit++) {
1465 ModelAction *act = *rit;
1466 bool foundvalue = false;
1467 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1468 if (act->get_node()->get_read_from_at(j) == write) {
1474 feasiblewrite = false;
1478 if (feasiblewrite) {
1479 priv->too_many_reads = true;
1487 * Updates the mo_graph with the constraints imposed from the current
1490 * Basic idea is the following: Go through each other thread and find
1491 * the lastest action that happened before our read. Two cases:
1493 * (1) The action is a write => that write must either occur before
1494 * the write we read from or be the write we read from.
1496 * (2) The action is a read => the write that that action read from
1497 * must occur before the write we read from or be the same write.
1499 * @param curr The current action. Must be a read.
1500 * @param rf The action that curr reads from. Must be a write.
1501 * @return True if modification order edges were added; false otherwise
1503 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1505 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1508 ASSERT(curr->is_read());
1510 /* Last SC fence in the current thread */
1511 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1513 /* Iterate over all threads */
1514 for (i = 0; i < thrd_lists->size(); i++) {
1515 /* Last SC fence in thread i */
1516 ModelAction *last_sc_fence_thread_local = NULL;
1517 if (int_to_id((int)i) != curr->get_tid())
1518 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1520 /* Last SC fence in thread i, before last SC fence in current thread */
1521 ModelAction *last_sc_fence_thread_before = NULL;
1522 if (last_sc_fence_local)
1523 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1525 /* Iterate over actions in thread, starting from most recent */
1526 action_list_t *list = &(*thrd_lists)[i];
1527 action_list_t::reverse_iterator rit;
1528 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1529 ModelAction *act = *rit;
1531 if (act->is_write() && act != rf && act != curr) {
1532 /* C++, Section 29.3 statement 5 */
1533 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1534 *act < *last_sc_fence_thread_local) {
1535 mo_graph->addEdge(act, rf);
1539 /* C++, Section 29.3 statement 4 */
1540 else if (act->is_seqcst() && last_sc_fence_local &&
1541 *act < *last_sc_fence_local) {
1542 mo_graph->addEdge(act, rf);
1546 /* C++, Section 29.3 statement 6 */
1547 else if (last_sc_fence_thread_before &&
1548 *act < *last_sc_fence_thread_before) {
1549 mo_graph->addEdge(act, rf);
1556 * Include at most one act per-thread that "happens
1557 * before" curr. Don't consider reflexively.
1559 if (act->happens_before(curr) && act != curr) {
1560 if (act->is_write()) {
1562 mo_graph->addEdge(act, rf);
1566 const ModelAction *prevreadfrom = act->get_reads_from();
1567 //if the previous read is unresolved, keep going...
1568 if (prevreadfrom == NULL)
1571 if (rf != prevreadfrom) {
1572 mo_graph->addEdge(prevreadfrom, rf);
1584 /** This method fixes up the modification order when we resolve a
1585 * promises. The basic problem is that actions that occur after the
1586 * read curr could not property add items to the modification order
1589 * So for each thread, we find the earliest item that happens after
1590 * the read curr. This is the item we have to fix up with additional
1591 * constraints. If that action is write, we add a MO edge between
1592 * the Action rf and that action. If the action is a read, we add a
1593 * MO edge between the Action rf, and whatever the read accessed.
1595 * @param curr is the read ModelAction that we are fixing up MO edges for.
1596 * @param rf is the write ModelAction that curr reads from.
1599 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1601 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1603 ASSERT(curr->is_read());
1605 /* Iterate over all threads */
1606 for (i = 0; i < thrd_lists->size(); i++) {
1607 /* Iterate over actions in thread, starting from most recent */
1608 action_list_t *list = &(*thrd_lists)[i];
1609 action_list_t::reverse_iterator rit;
1610 ModelAction *lastact = NULL;
1612 /* Find last action that happens after curr that is either not curr or a rmw */
1613 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1614 ModelAction *act = *rit;
1615 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1621 /* Include at most one act per-thread that "happens before" curr */
1622 if (lastact != NULL) {
1623 if (lastact == curr) {
1624 //Case 1: The resolved read is a RMW, and we need to make sure
1625 //that the write portion of the RMW mod order after rf
1627 mo_graph->addEdge(rf, lastact);
1628 } else if (lastact->is_read()) {
1629 //Case 2: The resolved read is a normal read and the next
1630 //operation is a read, and we need to make sure the value read
1631 //is mod ordered after rf
1633 const ModelAction *postreadfrom = lastact->get_reads_from();
1634 if (postreadfrom != NULL && rf != postreadfrom)
1635 mo_graph->addEdge(rf, postreadfrom);
1637 //Case 3: The resolved read is a normal read and the next
1638 //operation is a write, and we need to make sure that the
1639 //write is mod ordered after rf
1641 mo_graph->addEdge(rf, lastact);
1649 * Updates the mo_graph with the constraints imposed from the current write.
1651 * Basic idea is the following: Go through each other thread and find
1652 * the lastest action that happened before our write. Two cases:
1654 * (1) The action is a write => that write must occur before
1657 * (2) The action is a read => the write that that action read from
1658 * must occur before the current write.
1660 * This method also handles two other issues:
1662 * (I) Sequential Consistency: Making sure that if the current write is
1663 * seq_cst, that it occurs after the previous seq_cst write.
1665 * (II) Sending the write back to non-synchronizing reads.
1667 * @param curr The current action. Must be a write.
1668 * @return True if modification order edges were added; false otherwise
1670 bool ModelChecker::w_modification_order(ModelAction *curr)
1672 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1675 ASSERT(curr->is_write());
1677 if (curr->is_seqcst()) {
1678 /* We have to at least see the last sequentially consistent write,
1679 so we are initialized. */
1680 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1681 if (last_seq_cst != NULL) {
1682 mo_graph->addEdge(last_seq_cst, curr);
1687 /* Last SC fence in the current thread */
1688 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1690 /* Iterate over all threads */
1691 for (i = 0; i < thrd_lists->size(); i++) {
1692 /* Last SC fence in thread i, before last SC fence in current thread */
1693 ModelAction *last_sc_fence_thread_before = NULL;
1694 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1695 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1697 /* Iterate over actions in thread, starting from most recent */
1698 action_list_t *list = &(*thrd_lists)[i];
1699 action_list_t::reverse_iterator rit;
1700 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1701 ModelAction *act = *rit;
1704 * 1) If RMW and it actually read from something, then we
1705 * already have all relevant edges, so just skip to next
1708 * 2) If RMW and it didn't read from anything, we should
1709 * whatever edge we can get to speed up convergence.
1711 * 3) If normal write, we need to look at earlier actions, so
1712 * continue processing list.
1714 if (curr->is_rmw()) {
1715 if (curr->get_reads_from() != NULL)
1723 /* C++, Section 29.3 statement 7 */
1724 if (last_sc_fence_thread_before && act->is_write() &&
1725 *act < *last_sc_fence_thread_before) {
1726 mo_graph->addEdge(act, curr);
1732 * Include at most one act per-thread that "happens
1735 if (act->happens_before(curr)) {
1737 * Note: if act is RMW, just add edge:
1739 * The following edge should be handled elsewhere:
1740 * readfrom(act) --mo--> act
1742 if (act->is_write())
1743 mo_graph->addEdge(act, curr);
1744 else if (act->is_read()) {
1745 //if previous read accessed a null, just keep going
1746 if (act->get_reads_from() == NULL)
1748 mo_graph->addEdge(act->get_reads_from(), curr);
1752 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1753 !act->same_thread(curr)) {
1754 /* We have an action that:
1755 (1) did not happen before us
1756 (2) is a read and we are a write
1757 (3) cannot synchronize with us
1758 (4) is in a different thread
1760 that read could potentially read from our write. Note that
1761 these checks are overly conservative at this point, we'll
1762 do more checks before actually removing the
1766 if (thin_air_constraint_may_allow(curr, act)) {
1767 if (!is_infeasible() ||
1768 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1769 struct PendingFutureValue pfv = {curr, act};
1770 futurevalues->push_back(pfv);
1780 /** Arbitrary reads from the future are not allowed. Section 29.3
1781 * part 9 places some constraints. This method checks one result of constraint
1782 * constraint. Others require compiler support. */
1783 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1785 if (!writer->is_rmw())
1788 if (!reader->is_rmw())
1791 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1792 if (search == reader)
1794 if (search->get_tid() == reader->get_tid() &&
1795 search->happens_before(reader))
1803 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1804 * some constraints. This method checks one the following constraint (others
1805 * require compiler support):
1807 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1809 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1811 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1813 /* Iterate over all threads */
1814 for (i = 0; i < thrd_lists->size(); i++) {
1815 const ModelAction *write_after_read = NULL;
1817 /* Iterate over actions in thread, starting from most recent */
1818 action_list_t *list = &(*thrd_lists)[i];
1819 action_list_t::reverse_iterator rit;
1820 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1821 ModelAction *act = *rit;
1823 /* Don't disallow due to act == reader */
1824 if (!reader->happens_before(act) || reader == act)
1826 else if (act->is_write())
1827 write_after_read = act;
1828 else if (act->is_read() && act->get_reads_from() != NULL)
1829 write_after_read = act->get_reads_from();
1832 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1839 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1840 * The ModelAction under consideration is expected to be taking part in
1841 * release/acquire synchronization as an object of the "reads from" relation.
1842 * Note that this can only provide release sequence support for RMW chains
1843 * which do not read from the future, as those actions cannot be traced until
1844 * their "promise" is fulfilled. Similarly, we may not even establish the
1845 * presence of a release sequence with certainty, as some modification order
1846 * constraints may be decided further in the future. Thus, this function
1847 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1848 * and a boolean representing certainty.
1850 * @param rf The action that might be part of a release sequence. Must be a
1852 * @param release_heads A pass-by-reference style return parameter. After
1853 * execution of this function, release_heads will contain the heads of all the
1854 * relevant release sequences, if any exists with certainty
1855 * @param pending A pass-by-reference style return parameter which is only used
1856 * when returning false (i.e., uncertain). Returns most information regarding
1857 * an uncertain release sequence, including any write operations that might
1858 * break the sequence.
1859 * @return true, if the ModelChecker is certain that release_heads is complete;
1862 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1863 rel_heads_list_t *release_heads,
1864 struct release_seq *pending) const
1866 /* Only check for release sequences if there are no cycles */
1867 if (mo_graph->checkForCycles())
1871 ASSERT(rf->is_write());
1873 if (rf->is_release())
1874 release_heads->push_back(rf);
1875 else if (rf->get_last_fence_release())
1876 release_heads->push_back(rf->get_last_fence_release());
1878 break; /* End of RMW chain */
1880 /** @todo Need to be smarter here... In the linux lock
1881 * example, this will run to the beginning of the program for
1883 /** @todo The way to be smarter here is to keep going until 1
1884 * thread has a release preceded by an acquire and you've seen
1887 /* acq_rel RMW is a sufficient stopping condition */
1888 if (rf->is_acquire() && rf->is_release())
1889 return true; /* complete */
1891 rf = rf->get_reads_from();
1894 /* read from future: need to settle this later */
1896 return false; /* incomplete */
1899 if (rf->is_release())
1900 return true; /* complete */
1902 /* else relaxed write
1903 * - check for fence-release in the same thread (29.8, stmt. 3)
1904 * - check modification order for contiguous subsequence
1905 * -> rf must be same thread as release */
1907 const ModelAction *fence_release = rf->get_last_fence_release();
1908 /* Synchronize with a fence-release unconditionally; we don't need to
1909 * find any more "contiguous subsequence..." for it */
1911 release_heads->push_back(fence_release);
1913 int tid = id_to_int(rf->get_tid());
1914 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1915 action_list_t *list = &(*thrd_lists)[tid];
1916 action_list_t::const_reverse_iterator rit;
1918 /* Find rf in the thread list */
1919 rit = std::find(list->rbegin(), list->rend(), rf);
1920 ASSERT(rit != list->rend());
1922 /* Find the last {write,fence}-release */
1923 for (; rit != list->rend(); rit++) {
1924 if (fence_release && *(*rit) < *fence_release)
1926 if ((*rit)->is_release())
1929 if (rit == list->rend()) {
1930 /* No write-release in this thread */
1931 return true; /* complete */
1932 } else if (fence_release && *(*rit) < *fence_release) {
1933 /* The fence-release is more recent (and so, "stronger") than
1934 * the most recent write-release */
1935 return true; /* complete */
1936 } /* else, need to establish contiguous release sequence */
1937 ModelAction *release = *rit;
1939 ASSERT(rf->same_thread(release));
1941 pending->writes.clear();
1943 bool certain = true;
1944 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1945 if (id_to_int(rf->get_tid()) == (int)i)
1947 list = &(*thrd_lists)[i];
1949 /* Can we ensure no future writes from this thread may break
1950 * the release seq? */
1951 bool future_ordered = false;
1953 ModelAction *last = get_last_action(int_to_id(i));
1954 Thread *th = get_thread(int_to_id(i));
1955 if ((last && rf->happens_before(last)) ||
1958 future_ordered = true;
1960 ASSERT(!th->is_model_thread() || future_ordered);
1962 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1963 const ModelAction *act = *rit;
1964 /* Reach synchronization -> this thread is complete */
1965 if (act->happens_before(release))
1967 if (rf->happens_before(act)) {
1968 future_ordered = true;
1972 /* Only non-RMW writes can break release sequences */
1973 if (!act->is_write() || act->is_rmw())
1976 /* Check modification order */
1977 if (mo_graph->checkReachable(rf, act)) {
1978 /* rf --mo--> act */
1979 future_ordered = true;
1982 if (mo_graph->checkReachable(act, release))
1983 /* act --mo--> release */
1985 if (mo_graph->checkReachable(release, act) &&
1986 mo_graph->checkReachable(act, rf)) {
1987 /* release --mo-> act --mo--> rf */
1988 return true; /* complete */
1990 /* act may break release sequence */
1991 pending->writes.push_back(act);
1994 if (!future_ordered)
1995 certain = false; /* This thread is uncertain */
1999 release_heads->push_back(release);
2000 pending->writes.clear();
2002 pending->release = release;
2009 * An interface for getting the release sequence head(s) with which a
2010 * given ModelAction must synchronize. This function only returns a non-empty
2011 * result when it can locate a release sequence head with certainty. Otherwise,
2012 * it may mark the internal state of the ModelChecker so that it will handle
2013 * the release sequence at a later time, causing @a acquire to update its
2014 * synchronization at some later point in execution.
2016 * @param acquire The 'acquire' action that may synchronize with a release
2018 * @param read The read action that may read from a release sequence; this may
2019 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2020 * when 'acquire' is a fence-acquire)
2021 * @param release_heads A pass-by-reference return parameter. Will be filled
2022 * with the head(s) of the release sequence(s), if they exists with certainty.
2023 * @see ModelChecker::release_seq_heads
2025 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2026 ModelAction *read, rel_heads_list_t *release_heads)
2028 const ModelAction *rf = read->get_reads_from();
2029 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2030 sequence->acquire = acquire;
2031 sequence->read = read;
2033 if (!release_seq_heads(rf, release_heads, sequence)) {
2034 /* add act to 'lazy checking' list */
2035 pending_rel_seqs->push_back(sequence);
2037 snapshot_free(sequence);
2042 * Attempt to resolve all stashed operations that might synchronize with a
2043 * release sequence for a given location. This implements the "lazy" portion of
2044 * determining whether or not a release sequence was contiguous, since not all
2045 * modification order information is present at the time an action occurs.
2047 * @param location The location/object that should be checked for release
2048 * sequence resolutions. A NULL value means to check all locations.
2049 * @param work_queue The work queue to which to add work items as they are
2051 * @return True if any updates occurred (new synchronization, new mo_graph
2054 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2056 bool updated = false;
2057 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2058 while (it != pending_rel_seqs->end()) {
2059 struct release_seq *pending = *it;
2060 ModelAction *acquire = pending->acquire;
2061 const ModelAction *read = pending->read;
2063 /* Only resolve sequences on the given location, if provided */
2064 if (location && read->get_location() != location) {
2069 const ModelAction *rf = read->get_reads_from();
2070 rel_heads_list_t release_heads;
2072 complete = release_seq_heads(rf, &release_heads, pending);
2073 for (unsigned int i = 0; i < release_heads.size(); i++) {
2074 if (!acquire->has_synchronized_with(release_heads[i])) {
2075 if (acquire->synchronize_with(release_heads[i]))
2078 set_bad_synchronization();
2083 /* Re-check all pending release sequences */
2084 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2085 /* Re-check read-acquire for mo_graph edges */
2086 if (acquire->is_read())
2087 work_queue->push_back(MOEdgeWorkEntry(acquire));
2089 /* propagate synchronization to later actions */
2090 action_list_t::reverse_iterator rit = action_trace->rbegin();
2091 for (; (*rit) != acquire; rit++) {
2092 ModelAction *propagate = *rit;
2093 if (acquire->happens_before(propagate)) {
2094 propagate->synchronize_with(acquire);
2095 /* Re-check 'propagate' for mo_graph edges */
2096 work_queue->push_back(MOEdgeWorkEntry(propagate));
2101 it = pending_rel_seqs->erase(it);
2102 snapshot_free(pending);
2108 // If we resolved promises or data races, see if we have realized a data race.
2115 * Performs various bookkeeping operations for the current ModelAction. For
2116 * instance, adds action to the per-object, per-thread action vector and to the
2117 * action trace list of all thread actions.
2119 * @param act is the ModelAction to add.
2121 void ModelChecker::add_action_to_lists(ModelAction *act)
2123 int tid = id_to_int(act->get_tid());
2124 ModelAction *uninit = NULL;
2126 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2127 if (list->empty() && act->is_atomic_var()) {
2128 uninit = new_uninitialized_action(act->get_location());
2129 uninit_id = id_to_int(uninit->get_tid());
2130 list->push_back(uninit);
2132 list->push_back(act);
2134 action_trace->push_back(act);
2136 action_trace->push_front(uninit);
2138 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2139 if (tid >= (int)vec->size())
2140 vec->resize(priv->next_thread_id);
2141 (*vec)[tid].push_back(act);
2143 (*vec)[uninit_id].push_front(uninit);
2145 if ((int)thrd_last_action->size() <= tid)
2146 thrd_last_action->resize(get_num_threads());
2147 (*thrd_last_action)[tid] = act;
2149 (*thrd_last_action)[uninit_id] = uninit;
2151 if (act->is_fence() && act->is_release()) {
2152 if ((int)thrd_last_fence_release->size() <= tid)
2153 thrd_last_fence_release->resize(get_num_threads());
2154 (*thrd_last_fence_release)[tid] = act;
2157 if (act->is_wait()) {
2158 void *mutex_loc = (void *) act->get_value();
2159 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2161 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2162 if (tid >= (int)vec->size())
2163 vec->resize(priv->next_thread_id);
2164 (*vec)[tid].push_back(act);
2169 * @brief Get the last action performed by a particular Thread
2170 * @param tid The thread ID of the Thread in question
2171 * @return The last action in the thread
2173 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2175 int threadid = id_to_int(tid);
2176 if (threadid < (int)thrd_last_action->size())
2177 return (*thrd_last_action)[id_to_int(tid)];
2183 * @brief Get the last fence release performed by a particular Thread
2184 * @param tid The thread ID of the Thread in question
2185 * @return The last fence release in the thread, if one exists; NULL otherwise
2187 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2189 int threadid = id_to_int(tid);
2190 if (threadid < (int)thrd_last_fence_release->size())
2191 return (*thrd_last_fence_release)[id_to_int(tid)];
2197 * Gets the last memory_order_seq_cst write (in the total global sequence)
2198 * performed on a particular object (i.e., memory location), not including the
2200 * @param curr The current ModelAction; also denotes the object location to
2202 * @return The last seq_cst write
2204 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2206 void *location = curr->get_location();
2207 action_list_t *list = get_safe_ptr_action(obj_map, location);
2208 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2209 action_list_t::reverse_iterator rit;
2210 for (rit = list->rbegin(); rit != list->rend(); rit++)
2211 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2217 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2218 * performed in a particular thread, prior to a particular fence.
2219 * @param tid The ID of the thread to check
2220 * @param before_fence The fence from which to begin the search; if NULL, then
2221 * search for the most recent fence in the thread.
2222 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2224 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2226 /* All fences should have NULL location */
2227 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2228 action_list_t::reverse_iterator rit = list->rbegin();
2231 for (; rit != list->rend(); rit++)
2232 if (*rit == before_fence)
2235 ASSERT(*rit == before_fence);
2239 for (; rit != list->rend(); rit++)
2240 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2246 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2247 * location). This function identifies the mutex according to the current
2248 * action, which is presumed to perform on the same mutex.
2249 * @param curr The current ModelAction; also denotes the object location to
2251 * @return The last unlock operation
2253 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2255 void *location = curr->get_location();
2256 action_list_t *list = get_safe_ptr_action(obj_map, location);
2257 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2258 action_list_t::reverse_iterator rit;
2259 for (rit = list->rbegin(); rit != list->rend(); rit++)
2260 if ((*rit)->is_unlock() || (*rit)->is_wait())
2265 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2267 ModelAction *parent = get_last_action(tid);
2269 parent = get_thread(tid)->get_creation();
2274 * Returns the clock vector for a given thread.
2275 * @param tid The thread whose clock vector we want
2276 * @return Desired clock vector
2278 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2280 return get_parent_action(tid)->get_cv();
2284 * Resolve a set of Promises with a current write. The set is provided in the
2285 * Node corresponding to @a write.
2286 * @param write The ModelAction that is fulfilling Promises
2287 * @return True if promises were resolved; false otherwise
2289 bool ModelChecker::resolve_promises(ModelAction *write)
2291 bool resolved = false;
2292 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2294 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2295 Promise *promise = (*promises)[promise_index];
2296 if (write->get_node()->get_promise(i)) {
2297 ModelAction *read = promise->get_action();
2298 if (read->is_rmw()) {
2299 mo_graph->addRMWEdge(write, read);
2301 read_from(read, write);
2302 //First fix up the modification order for actions that happened
2304 r_modification_order(read, write);
2305 //Next fix up the modification order for actions that happened
2307 post_r_modification_order(read, write);
2308 //Make sure the promise's value matches the write's value
2309 ASSERT(promise->get_value() == write->get_value());
2312 promises->erase(promises->begin() + promise_index);
2313 threads_to_check.push_back(read->get_tid());
2320 //Check whether reading these writes has made threads unable to
2323 for (unsigned int i = 0; i < threads_to_check.size(); i++)
2324 mo_check_promises(threads_to_check[i], write);
2330 * Compute the set of promises that could potentially be satisfied by this
2331 * action. Note that the set computation actually appears in the Node, not in
2333 * @param curr The ModelAction that may satisfy promises
2335 void ModelChecker::compute_promises(ModelAction *curr)
2337 for (unsigned int i = 0; i < promises->size(); i++) {
2338 Promise *promise = (*promises)[i];
2339 const ModelAction *act = promise->get_action();
2340 if (!act->happens_before(curr) &&
2342 !act->could_synchronize_with(curr) &&
2343 !act->same_thread(curr) &&
2344 act->get_location() == curr->get_location() &&
2345 promise->get_value() == curr->get_value()) {
2346 curr->get_node()->set_promise(i, act->is_rmw());
2351 /** Checks promises in response to change in ClockVector Threads. */
2352 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2354 for (unsigned int i = 0; i < promises->size(); i++) {
2355 Promise *promise = (*promises)[i];
2356 const ModelAction *act = promise->get_action();
2357 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2358 merge_cv->synchronized_since(act)) {
2359 if (promise->increment_threads(tid)) {
2360 //Promise has failed
2361 priv->failed_promise = true;
2368 void ModelChecker::check_promises_thread_disabled() {
2369 for (unsigned int i = 0; i < promises->size(); i++) {
2370 Promise *promise = (*promises)[i];
2371 if (promise->check_promise()) {
2372 priv->failed_promise = true;
2378 /** Checks promises in response to addition to modification order for threads.
2380 * pthread is the thread that performed the read that created the promise
2382 * pread is the read that created the promise
2384 * pwrite is either the first write to same location as pread by
2385 * pthread that is sequenced after pread or the value read by the
2386 * first read to the same lcoation as pread by pthread that is
2387 * sequenced after pread..
2389 * 1. If tid=pthread, then we check what other threads are reachable
2390 * through the mode order starting with pwrite. Those threads cannot
2391 * perform a write that will resolve the promise due to modification
2392 * order constraints.
2394 * 2. If the tid is not pthread, we check whether pwrite can reach the
2395 * action write through the modification order. If so, that thread
2396 * cannot perform a future write that will resolve the promise due to
2397 * modificatin order constraints.
2399 * @param tid The thread that either read from the model action
2400 * write, or actually did the model action write.
2402 * @param write The ModelAction representing the relevant write.
2404 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write)
2406 void *location = write->get_location();
2407 for (unsigned int i = 0; i < promises->size(); i++) {
2408 Promise *promise = (*promises)[i];
2409 const ModelAction *act = promise->get_action();
2411 //Is this promise on the same location?
2412 if (act->get_location() != location)
2415 //same thread as the promise
2416 if (act->get_tid() == tid) {
2418 //do we have a pwrite for the promise, if not, set it
2419 if (promise->get_write() == NULL) {
2420 promise->set_write(write);
2421 //The pwrite cannot happen before the promise
2422 if (write->happens_before(act) && (write != act)) {
2423 priv->failed_promise = true;
2427 if (mo_graph->checkPromise(write, promise)) {
2428 priv->failed_promise = true;
2433 //Don't do any lookups twice for the same thread
2434 if (promise->has_sync_thread(tid))
2437 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2438 if (promise->increment_threads(tid)) {
2439 priv->failed_promise = true;
2447 * Compute the set of writes that may break the current pending release
2448 * sequence. This information is extracted from previou release sequence
2451 * @param curr The current ModelAction. Must be a release sequence fixup
2454 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2456 if (pending_rel_seqs->empty())
2459 struct release_seq *pending = pending_rel_seqs->back();
2460 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2461 const ModelAction *write = pending->writes[i];
2462 curr->get_node()->add_relseq_break(write);
2465 /* NULL means don't break the sequence; just synchronize */
2466 curr->get_node()->add_relseq_break(NULL);
2470 * Build up an initial set of all past writes that this 'read' action may read
2471 * from. This set is determined by the clock vector's "happens before"
2473 * @param curr is the current ModelAction that we are exploring; it must be a
2476 void ModelChecker::build_reads_from_past(ModelAction *curr)
2478 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2480 ASSERT(curr->is_read());
2482 ModelAction *last_sc_write = NULL;
2484 if (curr->is_seqcst())
2485 last_sc_write = get_last_seq_cst_write(curr);
2487 /* Iterate over all threads */
2488 for (i = 0; i < thrd_lists->size(); i++) {
2489 /* Iterate over actions in thread, starting from most recent */
2490 action_list_t *list = &(*thrd_lists)[i];
2491 action_list_t::reverse_iterator rit;
2492 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2493 ModelAction *act = *rit;
2495 /* Only consider 'write' actions */
2496 if (!act->is_write() || act == curr)
2499 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2500 bool allow_read = true;
2502 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2504 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2508 DEBUG("Adding action to may_read_from:\n");
2509 if (DBG_ENABLED()) {
2513 curr->get_node()->add_read_from(act);
2516 /* Include at most one act per-thread that "happens before" curr */
2517 if (act->happens_before(curr))
2522 if (DBG_ENABLED()) {
2523 model_print("Reached read action:\n");
2525 model_print("Printing may_read_from\n");
2526 curr->get_node()->print_may_read_from();
2527 model_print("End printing may_read_from\n");
2531 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2534 /* UNINIT actions don't have a Node, and they never sleep */
2535 if (write->is_uninitialized())
2537 Node *prevnode = write->get_node()->get_parent();
2539 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2540 if (write->is_release() && thread_sleep)
2542 if (!write->is_rmw()) {
2545 if (write->get_reads_from() == NULL)
2547 write = write->get_reads_from();
2552 * @brief Create a new action representing an uninitialized atomic
2553 * @param location The memory location of the atomic object
2554 * @return A pointer to a new ModelAction
2556 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2558 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2559 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2560 act->create_cv(NULL);
2564 static void print_list(action_list_t *list, int exec_num = -1)
2566 action_list_t::iterator it;
2568 model_print("---------------------------------------------------------------------\n");
2570 model_print("Execution %d:\n", exec_num);
2572 unsigned int hash = 0;
2574 for (it = list->begin(); it != list->end(); it++) {
2576 hash = hash^(hash<<3)^((*it)->hash());
2578 model_print("HASH %u\n", hash);
2579 model_print("---------------------------------------------------------------------\n");
2582 #if SUPPORT_MOD_ORDER_DUMP
2583 void ModelChecker::dumpGraph(char *filename) const
2586 sprintf(buffer, "%s.dot", filename);
2587 FILE *file = fopen(buffer, "w");
2588 fprintf(file, "digraph %s {\n", filename);
2589 mo_graph->dumpNodes(file);
2590 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2592 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2593 ModelAction *action = *it;
2594 if (action->is_read()) {
2595 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2596 if (action->get_reads_from() != NULL)
2597 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2599 if (thread_array[action->get_tid()] != NULL) {
2600 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2603 thread_array[action->get_tid()] = action;
2605 fprintf(file, "}\n");
2606 model_free(thread_array);
2611 /** @brief Prints an execution trace summary. */
2612 void ModelChecker::print_summary() const
2614 #if SUPPORT_MOD_ORDER_DUMP
2616 char buffername[100];
2617 sprintf(buffername, "exec%04u", stats.num_total);
2618 mo_graph->dumpGraphToFile(buffername);
2619 sprintf(buffername, "graph%04u", stats.num_total);
2620 dumpGraph(buffername);
2623 if (!isfeasibleprefix())
2624 model_print("INFEASIBLE EXECUTION!\n");
2625 print_list(action_trace, stats.num_total);
2630 * Add a Thread to the system for the first time. Should only be called once
2632 * @param t The Thread to add
2634 void ModelChecker::add_thread(Thread *t)
2636 thread_map->put(id_to_int(t->get_id()), t);
2637 scheduler->add_thread(t);
2641 * Removes a thread from the scheduler.
2642 * @param the thread to remove.
2644 void ModelChecker::remove_thread(Thread *t)
2646 scheduler->remove_thread(t);
2650 * @brief Get a Thread reference by its ID
2651 * @param tid The Thread's ID
2652 * @return A Thread reference
2654 Thread * ModelChecker::get_thread(thread_id_t tid) const
2656 return thread_map->get(id_to_int(tid));
2660 * @brief Get a reference to the Thread in which a ModelAction was executed
2661 * @param act The ModelAction
2662 * @return A Thread reference
2664 Thread * ModelChecker::get_thread(ModelAction *act) const
2666 return get_thread(act->get_tid());
2670 * @brief Check if a Thread is currently enabled
2671 * @param t The Thread to check
2672 * @return True if the Thread is currently enabled
2674 bool ModelChecker::is_enabled(Thread *t) const
2676 return scheduler->is_enabled(t);
2680 * @brief Check if a Thread is currently enabled
2681 * @param tid The ID of the Thread to check
2682 * @return True if the Thread is currently enabled
2684 bool ModelChecker::is_enabled(thread_id_t tid) const
2686 return scheduler->is_enabled(tid);
2690 * Switch from a user-context to the "master thread" context (a.k.a. system
2691 * context). This switch is made with the intention of exploring a particular
2692 * model-checking action (described by a ModelAction object). Must be called
2693 * from a user-thread context.
2695 * @param act The current action that will be explored. May be NULL only if
2696 * trace is exiting via an assertion (see ModelChecker::set_assert and
2697 * ModelChecker::has_asserted).
2698 * @return Return the value returned by the current action
2700 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2703 Thread *old = thread_current();
2704 set_current_action(act);
2705 old->set_state(THREAD_READY);
2706 if (Thread::swap(old, &system_context) < 0) {
2707 perror("swap threads");
2710 return old->get_return_value();
2714 * Takes the next step in the execution, if possible.
2715 * @param curr The current step to take
2716 * @return Returns true (success) if a step was taken and false otherwise.
2718 bool ModelChecker::take_step(ModelAction *curr)
2723 Thread *curr_thrd = get_thread(curr);
2724 ASSERT(curr_thrd->get_state() == THREAD_READY);
2726 Thread *next_thrd = check_current_action(curr);
2728 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2729 scheduler->remove_thread(curr_thrd);
2731 next_thrd = scheduler->next_thread(next_thrd);
2733 /* Infeasible -> don't take any more steps */
2734 if (is_infeasible())
2736 else if (isfeasibleprefix() && have_bug_reports()) {
2741 if (params.bound != 0) {
2742 if (priv->used_sequence_numbers > params.bound) {
2747 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2748 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2751 * Launch end-of-execution release sequence fixups only when there are:
2753 * (1) no more user threads to run (or when execution replay chooses
2754 * the 'model_thread')
2755 * (2) pending release sequences
2756 * (3) pending assertions (i.e., data races)
2757 * (4) no pending promises
2759 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2760 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2761 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2762 pending_rel_seqs->size());
2763 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2764 std::memory_order_seq_cst, NULL, VALUE_NONE,
2766 set_current_action(fixup);
2770 /* next_thrd == NULL -> don't take any more steps */
2774 next_thrd->set_state(THREAD_RUNNING);
2776 if (next_thrd->get_pending() != NULL) {
2777 /* restart a pending action */
2778 set_current_action(next_thrd->get_pending());
2779 next_thrd->set_pending(NULL);
2780 next_thrd->set_state(THREAD_READY);
2784 /* Return false only if swap fails with an error */
2785 return (Thread::swap(&system_context, next_thrd) == 0);
2788 /** Wrapper to run the user's main function, with appropriate arguments */
2789 void user_main_wrapper(void *)
2791 user_main(model->params.argc, model->params.argv);
2794 /** @brief Run ModelChecker for the user program */
2795 void ModelChecker::run()
2799 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2803 /* Run user thread up to its first action */
2804 scheduler->next_thread(t);
2805 Thread::swap(&system_context, t);
2807 /* Wait for all threads to complete */
2808 while (take_step(priv->current_action));
2809 } while (next_execution());