9 #include "snapshot-interface.h"
11 #include "clockvector.h"
12 #include "cyclegraph.h"
15 #include "threads-model.h"
18 #define INITIAL_THREAD_ID 0
23 bug_message(const char *str) {
24 const char *fmt = " [BUG] %s\n";
25 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
26 sprintf(msg, fmt, str);
28 ~bug_message() { if (msg) snapshot_free(msg); }
31 void print() { model_print("%s", msg); }
37 * Structure for holding small ModelChecker members that should be snapshotted
39 struct model_snapshot_members {
40 model_snapshot_members() :
42 /* First thread created will have id INITIAL_THREAD_ID */
43 next_thread_id(INITIAL_THREAD_ID),
44 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;
65 ModelAction *next_backtrack;
66 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
67 struct execution_stats stats;
70 /** @brief Incorrectly-ordered synchronization was made */
71 bool bad_synchronization;
77 /** @brief Constructor */
78 ModelChecker::ModelChecker(struct model_params params) :
79 /* Initialize default scheduler */
81 scheduler(new Scheduler()),
83 earliest_diverge(NULL),
84 action_trace(new action_list_t()),
85 thread_map(new HashTable<int, Thread *, int>()),
86 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
89 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
90 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
91 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
92 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
93 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
94 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
95 node_stack(new NodeStack()),
96 priv(new struct model_snapshot_members()),
97 mo_graph(new CycleGraph())
99 /* Initialize a model-checker thread, for special ModelActions */
100 model_thread = new Thread(get_next_id());
101 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
104 /** @brief Destructor */
105 ModelChecker::~ModelChecker()
107 for (unsigned int i = 0; i < get_num_threads(); i++)
108 delete thread_map->get(i);
113 delete lock_waiters_map;
114 delete condvar_waiters_map;
117 for (unsigned int i = 0; i < promises->size(); i++)
118 delete (*promises)[i];
121 delete pending_rel_seqs;
123 delete thrd_last_action;
124 delete thrd_last_fence_release;
131 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) {
141 std::vector<action_list_t> * tmp=hash->get(ptr);
143 tmp=new std::vector<action_list_t>();
150 * Restores user program to initial state and resets all model-checker data
153 void ModelChecker::reset_to_initial_state()
155 DEBUG("+++ Resetting to initial state +++\n");
156 node_stack->reset_execution();
158 /* Print all model-checker output before rollback */
161 snapshotObject->backTrackBeforeStep(0);
164 /** @return a thread ID for a new Thread */
165 thread_id_t ModelChecker::get_next_id()
167 return priv->next_thread_id++;
170 /** @return the number of user threads created during this execution */
171 unsigned int ModelChecker::get_num_threads() const
173 return priv->next_thread_id;
176 /** @return The currently executing Thread. */
177 Thread * ModelChecker::get_current_thread() const
179 return scheduler->get_current_thread();
182 /** @return a sequence number for a new ModelAction */
183 modelclock_t ModelChecker::get_next_seq_num()
185 return ++priv->used_sequence_numbers;
188 Node * ModelChecker::get_curr_node() const
190 return node_stack->get_head();
194 * @brief Choose the next thread to execute.
196 * This function chooses the next thread that should execute. It can force the
197 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
198 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
199 * The model-checker may have no preference regarding the next thread (i.e.,
200 * when exploring a new execution ordering), in which case this will return
202 * @param curr The current ModelAction. This action might guide the choice of
204 * @return The next thread to run. If the model-checker has no preference, NULL.
206 Thread * ModelChecker::get_next_thread(ModelAction *curr)
211 /* Do not split atomic actions. */
213 return thread_current();
214 /* The THREAD_CREATE action points to the created Thread */
215 else if (curr->get_type() == THREAD_CREATE)
216 return (Thread *)curr->get_location();
219 /* Have we completed exploring the preselected path? */
223 /* Else, we are trying to replay an execution */
224 ModelAction *next = node_stack->get_next()->get_action();
226 if (next == diverge) {
227 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
228 earliest_diverge=diverge;
230 Node *nextnode = next->get_node();
231 Node *prevnode = nextnode->get_parent();
232 scheduler->update_sleep_set(prevnode);
234 /* Reached divergence point */
235 if (nextnode->increment_misc()) {
236 /* The next node will try to satisfy a different misc_index values. */
237 tid = next->get_tid();
238 node_stack->pop_restofstack(2);
239 } else if (nextnode->increment_promise()) {
240 /* The next node will try to satisfy a different set of promises. */
241 tid = next->get_tid();
242 node_stack->pop_restofstack(2);
243 } else if (nextnode->increment_read_from()) {
244 /* The next node will read from a different value. */
245 tid = next->get_tid();
246 node_stack->pop_restofstack(2);
247 } else if (nextnode->increment_future_value()) {
248 /* The next node will try to read from a different future value. */
249 tid = next->get_tid();
250 node_stack->pop_restofstack(2);
251 } else if (nextnode->increment_relseq_break()) {
252 /* The next node will try to resolve a release sequence differently */
253 tid = next->get_tid();
254 node_stack->pop_restofstack(2);
256 /* Make a different thread execute for next step */
257 scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid())));
258 tid = prevnode->get_next_backtrack();
259 /* Make sure the backtracked thread isn't sleeping. */
260 node_stack->pop_restofstack(1);
261 if (diverge==earliest_diverge) {
262 earliest_diverge=prevnode->get_action();
265 /* The correct sleep set is in the parent node. */
268 DEBUG("*** Divergence point ***\n");
272 tid = next->get_tid();
274 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
275 ASSERT(tid != THREAD_ID_T_NONE);
276 return thread_map->get(id_to_int(tid));
280 * We need to know what the next actions of all threads in the sleep
281 * set will be. This method computes them and stores the actions at
282 * the corresponding thread object's pending action.
285 void ModelChecker::execute_sleep_set() {
286 for(unsigned int i=0;i<get_num_threads();i++) {
287 thread_id_t tid=int_to_id(i);
288 Thread *thr=get_thread(tid);
289 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
290 thr->set_state(THREAD_RUNNING);
291 scheduler->next_thread(thr);
292 Thread::swap(&system_context, thr);
293 priv->current_action->set_sleep_flag();
294 thr->set_pending(priv->current_action);
297 priv->current_action = NULL;
300 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
302 for (unsigned int i = 0; i < get_num_threads(); i++) {
303 Thread *thr = get_thread(int_to_id(i));
304 if (scheduler->is_sleep_set(thr)) {
305 ModelAction *pending_act = thr->get_pending();
306 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
307 //Remove this thread from sleep set
308 scheduler->remove_sleep(thr);
313 /** @brief Alert the model-checker that an incorrectly-ordered
314 * synchronization was made */
315 void ModelChecker::set_bad_synchronization()
317 priv->bad_synchronization = true;
320 bool ModelChecker::has_asserted() const
322 return priv->asserted;
325 void ModelChecker::set_assert()
327 priv->asserted = true;
331 * Check if we are in a deadlock. Should only be called at the end of an
332 * execution, although it should not give false positives in the middle of an
333 * execution (there should be some ENABLED thread).
335 * @return True if program is in a deadlock; false otherwise
337 bool ModelChecker::is_deadlocked() const
339 bool blocking_threads = false;
340 for (unsigned int i = 0; i < get_num_threads(); i++) {
341 thread_id_t tid = int_to_id(i);
344 Thread *t = get_thread(tid);
345 if (!t->is_model_thread() && t->get_pending())
346 blocking_threads = true;
348 return blocking_threads;
352 * Check if this is a complete execution. That is, have all thread completed
353 * execution (rather than exiting because sleep sets have forced a redundant
356 * @return True if the execution is complete.
358 bool ModelChecker::is_complete_execution() const
360 for (unsigned int i = 0; i < get_num_threads(); i++)
361 if (is_enabled(int_to_id(i)))
367 * @brief Assert a bug in the executing program.
369 * Use this function to assert any sort of bug in the user program. If the
370 * current trace is feasible (actually, a prefix of some feasible execution),
371 * then this execution will be aborted, printing the appropriate message. If
372 * the current trace is not yet feasible, the error message will be stashed and
373 * printed if the execution ever becomes feasible.
375 * @param msg Descriptive message for the bug (do not include newline char)
376 * @return True if bug is immediately-feasible
378 bool ModelChecker::assert_bug(const char *msg)
380 priv->bugs.push_back(new bug_message(msg));
382 if (isfeasibleprefix()) {
390 * @brief Assert a bug in the executing program, asserted by a user thread
391 * @see ModelChecker::assert_bug
392 * @param msg Descriptive message for the bug (do not include newline char)
394 void ModelChecker::assert_user_bug(const char *msg)
396 /* If feasible bug, bail out now */
398 switch_to_master(NULL);
401 /** @return True, if any bugs have been reported for this execution */
402 bool ModelChecker::have_bug_reports() const
404 return priv->bugs.size() != 0;
407 /** @brief Print bug report listing for this execution (if any bugs exist) */
408 void ModelChecker::print_bugs() const
410 if (have_bug_reports()) {
411 model_print("Bug report: %zu bug%s detected\n",
413 priv->bugs.size() > 1 ? "s" : "");
414 for (unsigned int i = 0; i < priv->bugs.size(); i++)
415 priv->bugs[i]->print();
420 * @brief Record end-of-execution stats
422 * Must be run when exiting an execution. Records various stats.
423 * @see struct execution_stats
425 void ModelChecker::record_stats()
428 if (!isfeasibleprefix())
429 stats.num_infeasible++;
430 else if (have_bug_reports())
431 stats.num_buggy_executions++;
432 else if (is_complete_execution())
433 stats.num_complete++;
435 stats.num_redundant++;
438 /** @brief Print execution stats */
439 void ModelChecker::print_stats() const
441 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
442 model_print("Number of redundant executions: %d\n", stats.num_redundant);
443 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
444 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
445 model_print("Total executions: %d\n", stats.num_total);
446 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
450 * @brief End-of-exeuction print
451 * @param printbugs Should any existing bugs be printed?
453 void ModelChecker::print_execution(bool printbugs) const
455 print_program_output();
457 if (DBG_ENABLED() || params.verbose) {
458 model_print("Earliest divergence point since last feasible execution:\n");
459 if (earliest_diverge)
460 earliest_diverge->print();
462 model_print("(Not set)\n");
468 /* Don't print invalid bugs */
477 * Queries the model-checker for more executions to explore and, if one
478 * exists, resets the model-checker state to execute a new execution.
480 * @return If there are more executions to explore, return true. Otherwise,
483 bool ModelChecker::next_execution()
486 /* Is this execution a feasible execution that's worth bug-checking? */
487 bool complete = isfeasibleprefix() && (is_complete_execution() ||
490 /* End-of-execution bug checks */
493 assert_bug("Deadlock detected");
501 if (DBG_ENABLED() || params.verbose || have_bug_reports())
502 print_execution(complete);
504 clear_program_output();
507 earliest_diverge = NULL;
509 if ((diverge = get_next_backtrack()) == NULL)
513 model_print("Next execution will diverge at:\n");
517 reset_to_initial_state();
521 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
523 switch (act->get_type()) {
528 /* Optimization: relaxed operations don't need backtracking */
529 if (act->is_relaxed())
531 /* linear search: from most recent to oldest */
532 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
533 action_list_t::reverse_iterator rit;
534 for (rit = list->rbegin(); rit != list->rend(); rit++) {
535 ModelAction *prev = *rit;
536 if (prev->could_synchronize_with(act))
542 case ATOMIC_TRYLOCK: {
543 /* linear search: from most recent to oldest */
544 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
545 action_list_t::reverse_iterator rit;
546 for (rit = list->rbegin(); rit != list->rend(); rit++) {
547 ModelAction *prev = *rit;
548 if (act->is_conflicting_lock(prev))
553 case ATOMIC_UNLOCK: {
554 /* linear search: from most recent to oldest */
555 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
556 action_list_t::reverse_iterator rit;
557 for (rit = list->rbegin(); rit != list->rend(); rit++) {
558 ModelAction *prev = *rit;
559 if (!act->same_thread(prev)&&prev->is_failed_trylock())
565 /* linear search: from most recent to oldest */
566 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
567 action_list_t::reverse_iterator rit;
568 for (rit = list->rbegin(); rit != list->rend(); rit++) {
569 ModelAction *prev = *rit;
570 if (!act->same_thread(prev)&&prev->is_failed_trylock())
572 if (!act->same_thread(prev)&&prev->is_notify())
578 case ATOMIC_NOTIFY_ALL:
579 case ATOMIC_NOTIFY_ONE: {
580 /* linear search: from most recent to oldest */
581 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
582 action_list_t::reverse_iterator rit;
583 for (rit = list->rbegin(); rit != list->rend(); rit++) {
584 ModelAction *prev = *rit;
585 if (!act->same_thread(prev)&&prev->is_wait())
596 /** This method finds backtracking points where we should try to
597 * reorder the parameter ModelAction against.
599 * @param the ModelAction to find backtracking points for.
601 void ModelChecker::set_backtracking(ModelAction *act)
603 Thread *t = get_thread(act);
604 ModelAction * prev = get_last_conflict(act);
608 Node * node = prev->get_node()->get_parent();
610 int low_tid, high_tid;
611 if (node->is_enabled(t)) {
612 low_tid = id_to_int(act->get_tid());
613 high_tid = low_tid+1;
616 high_tid = get_num_threads();
619 for(int i = low_tid; i < high_tid; i++) {
620 thread_id_t tid = int_to_id(i);
622 /* Make sure this thread can be enabled here. */
623 if (i >= node->get_num_threads())
626 /* Don't backtrack into a point where the thread is disabled or sleeping. */
627 if (node->enabled_status(tid)!=THREAD_ENABLED)
630 /* Check if this has been explored already */
631 if (node->has_been_explored(tid))
634 /* See if fairness allows */
635 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
637 for(int t=0;t<node->get_num_threads();t++) {
638 thread_id_t tother=int_to_id(t);
639 if (node->is_enabled(tother) && node->has_priority(tother)) {
647 /* Cache the latest backtracking point */
648 if (!priv->next_backtrack || *prev > *priv->next_backtrack)
649 priv->next_backtrack = prev;
651 /* If this is a new backtracking point, mark the tree */
652 if (!node->set_backtrack(tid))
654 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
655 id_to_int(prev->get_tid()),
656 id_to_int(t->get_id()));
665 * Returns last backtracking point. The model checker will explore a different
666 * path for this point in the next execution.
667 * @return The ModelAction at which the next execution should diverge.
669 ModelAction * ModelChecker::get_next_backtrack()
671 ModelAction *next = priv->next_backtrack;
672 priv->next_backtrack = NULL;
677 * Processes a read or rmw model action.
678 * @param curr is the read model action to process.
679 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
680 * @return True if processing this read updates the mo_graph.
682 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
684 uint64_t value = VALUE_NONE;
685 bool updated = false;
687 const ModelAction *reads_from = curr->get_node()->get_read_from();
688 if (reads_from != NULL) {
689 mo_graph->startChanges();
691 value = reads_from->get_value();
692 bool r_status = false;
694 if (!second_part_of_rmw) {
695 check_recency(curr, reads_from);
696 r_status = r_modification_order(curr, reads_from);
700 if (!second_part_of_rmw&&is_infeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
701 mo_graph->rollbackChanges();
702 priv->too_many_reads = false;
706 read_from(curr, reads_from);
707 mo_graph->commitChanges();
708 mo_check_promises(curr->get_tid(), reads_from);
711 } else if (!second_part_of_rmw) {
712 /* Read from future value */
713 value = curr->get_node()->get_future_value();
714 modelclock_t expiration = curr->get_node()->get_future_value_expiration();
715 read_from(curr, NULL);
716 Promise *valuepromise = new Promise(curr, value, expiration);
717 promises->push_back(valuepromise);
719 get_thread(curr)->set_return_value(value);
725 * Processes a lock, trylock, or unlock model action. @param curr is
726 * the read model action to process.
728 * The try lock operation checks whether the lock is taken. If not,
729 * it falls to the normal lock operation case. If so, it returns
732 * The lock operation has already been checked that it is enabled, so
733 * it just grabs the lock and synchronizes with the previous unlock.
735 * The unlock operation has to re-enable all of the threads that are
736 * waiting on the lock.
738 * @return True if synchronization was updated; false otherwise
740 bool ModelChecker::process_mutex(ModelAction *curr) {
741 std::mutex *mutex=NULL;
742 struct std::mutex_state *state=NULL;
744 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
745 mutex = (std::mutex *)curr->get_location();
746 state = mutex->get_state();
747 } else if(curr->is_wait()) {
748 mutex = (std::mutex *)curr->get_value();
749 state = mutex->get_state();
752 switch (curr->get_type()) {
753 case ATOMIC_TRYLOCK: {
754 bool success = !state->islocked;
755 curr->set_try_lock(success);
757 get_thread(curr)->set_return_value(0);
760 get_thread(curr)->set_return_value(1);
762 //otherwise fall into the lock case
764 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
765 assert_bug("Lock access before initialization");
766 state->islocked = true;
767 ModelAction *unlock = get_last_unlock(curr);
768 //synchronize with the previous unlock statement
769 if (unlock != NULL) {
770 curr->synchronize_with(unlock);
775 case ATOMIC_UNLOCK: {
777 state->islocked = false;
778 //wake up the other threads
779 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
780 //activate all the waiting threads
781 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
782 scheduler->wake(get_thread(*rit));
789 state->islocked = false;
790 //wake up the other threads
791 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
792 //activate all the waiting threads
793 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
794 scheduler->wake(get_thread(*rit));
797 //check whether we should go to sleep or not...simulate spurious failures
798 if (curr->get_node()->get_misc()==0) {
799 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
801 scheduler->sleep(get_current_thread());
805 case ATOMIC_NOTIFY_ALL: {
806 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
807 //activate all the waiting threads
808 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
809 scheduler->wake(get_thread(*rit));
814 case ATOMIC_NOTIFY_ONE: {
815 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
816 int wakeupthread=curr->get_node()->get_misc();
817 action_list_t::iterator it = waiters->begin();
818 advance(it, wakeupthread);
819 scheduler->wake(get_thread(*it));
831 * Process a write ModelAction
832 * @param curr The ModelAction to process
833 * @return True if the mo_graph was updated or promises were resolved
835 bool ModelChecker::process_write(ModelAction *curr)
837 bool updated_mod_order = w_modification_order(curr);
838 bool updated_promises = resolve_promises(curr);
840 if (promises->size() == 0) {
841 for (unsigned int i = 0; i < futurevalues->size(); i++) {
842 struct PendingFutureValue pfv = (*futurevalues)[i];
843 //Do more ambitious checks now that mo is more complete
844 if (mo_may_allow(pfv.writer, pfv.act)&&
845 pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number()+params.maxfuturedelay) &&
846 (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
847 priv->next_backtrack = pfv.act;
849 futurevalues->resize(0);
852 mo_graph->commitChanges();
853 mo_check_promises(curr->get_tid(), curr);
855 get_thread(curr)->set_return_value(VALUE_NONE);
856 return updated_mod_order || updated_promises;
860 * Process a fence ModelAction
861 * @param curr The ModelAction to process
862 * @return True if synchronization was updated
864 bool ModelChecker::process_fence(ModelAction *curr)
867 * fence-relaxed: no-op
868 * fence-release: only log the occurence (not in this function), for
869 * use in later synchronization
870 * fence-acquire (this function): search for hypothetical release
873 bool updated = false;
874 if (curr->is_acquire()) {
875 action_list_t *list = action_trace;
876 action_list_t::reverse_iterator rit;
877 /* Find X : is_read(X) && X --sb-> curr */
878 for (rit = list->rbegin(); rit != list->rend(); rit++) {
879 ModelAction *act = *rit;
882 if (act->get_tid() != curr->get_tid())
884 /* Stop at the beginning of the thread */
885 if (act->is_thread_start())
887 /* Stop once we reach a prior fence-acquire */
888 if (act->is_fence() && act->is_acquire())
892 /* read-acquire will find its own release sequences */
893 if (act->is_acquire())
896 /* Establish hypothetical release sequences */
897 rel_heads_list_t release_heads;
898 get_release_seq_heads(curr, act, &release_heads);
899 for (unsigned int i = 0; i < release_heads.size(); i++)
900 if (!curr->synchronize_with(release_heads[i]))
901 set_bad_synchronization();
902 if (release_heads.size() != 0)
910 * @brief Process the current action for thread-related activity
912 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
913 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
914 * synchronization, etc. This function is a no-op for non-THREAD actions
915 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
917 * @param curr The current action
918 * @return True if synchronization was updated or a thread completed
920 bool ModelChecker::process_thread_action(ModelAction *curr)
922 bool updated = false;
924 switch (curr->get_type()) {
925 case THREAD_CREATE: {
926 Thread *th = (Thread *)curr->get_location();
927 th->set_creation(curr);
931 Thread *blocking = (Thread *)curr->get_location();
932 ModelAction *act = get_last_action(blocking->get_id());
933 curr->synchronize_with(act);
934 updated = true; /* trigger rel-seq checks */
937 case THREAD_FINISH: {
938 Thread *th = get_thread(curr);
939 while (!th->wait_list_empty()) {
940 ModelAction *act = th->pop_wait_list();
941 scheduler->wake(get_thread(act));
944 updated = true; /* trigger rel-seq checks */
948 check_promises(curr->get_tid(), NULL, curr->get_cv());
959 * @brief Process the current action for release sequence fixup activity
961 * Performs model-checker release sequence fixups for the current action,
962 * forcing a single pending release sequence to break (with a given, potential
963 * "loose" write) or to complete (i.e., synchronize). If a pending release
964 * sequence forms a complete release sequence, then we must perform the fixup
965 * synchronization, mo_graph additions, etc.
967 * @param curr The current action; must be a release sequence fixup action
968 * @param work_queue The work queue to which to add work items as they are
971 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
973 const ModelAction *write = curr->get_node()->get_relseq_break();
974 struct release_seq *sequence = pending_rel_seqs->back();
975 pending_rel_seqs->pop_back();
977 ModelAction *acquire = sequence->acquire;
978 const ModelAction *rf = sequence->rf;
979 const ModelAction *release = sequence->release;
983 ASSERT(release->same_thread(rf));
987 * @todo Forcing a synchronization requires that we set
988 * modification order constraints. For instance, we can't allow
989 * a fixup sequence in which two separate read-acquire
990 * operations read from the same sequence, where the first one
991 * synchronizes and the other doesn't. Essentially, we can't
992 * allow any writes to insert themselves between 'release' and
996 /* Must synchronize */
997 if (!acquire->synchronize_with(release)) {
998 set_bad_synchronization();
1001 /* Re-check all pending release sequences */
1002 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1003 /* Re-check act for mo_graph edges */
1004 work_queue->push_back(MOEdgeWorkEntry(acquire));
1006 /* propagate synchronization to later actions */
1007 action_list_t::reverse_iterator rit = action_trace->rbegin();
1008 for (; (*rit) != acquire; rit++) {
1009 ModelAction *propagate = *rit;
1010 if (acquire->happens_before(propagate)) {
1011 propagate->synchronize_with(acquire);
1012 /* Re-check 'propagate' for mo_graph edges */
1013 work_queue->push_back(MOEdgeWorkEntry(propagate));
1017 /* Break release sequence with new edges:
1018 * release --mo--> write --mo--> rf */
1019 mo_graph->addEdge(release, write);
1020 mo_graph->addEdge(write, rf);
1023 /* See if we have realized a data race */
1028 * Initialize the current action by performing one or more of the following
1029 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1030 * in the NodeStack, manipulating backtracking sets, allocating and
1031 * initializing clock vectors, and computing the promises to fulfill.
1033 * @param curr The current action, as passed from the user context; may be
1034 * freed/invalidated after the execution of this function, with a different
1035 * action "returned" its place (pass-by-reference)
1036 * @return True if curr is a newly-explored action; false otherwise
1038 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1040 ModelAction *newcurr;
1042 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1043 newcurr = process_rmw(*curr);
1046 if (newcurr->is_rmw())
1047 compute_promises(newcurr);
1053 (*curr)->set_seq_number(get_next_seq_num());
1055 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1057 /* First restore type and order in case of RMW operation */
1058 if ((*curr)->is_rmwr())
1059 newcurr->copy_typeandorder(*curr);
1061 ASSERT((*curr)->get_location() == newcurr->get_location());
1062 newcurr->copy_from_new(*curr);
1064 /* Discard duplicate ModelAction; use action from NodeStack */
1067 /* Always compute new clock vector */
1068 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1071 return false; /* Action was explored previously */
1075 /* Always compute new clock vector */
1076 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1078 /* Assign most recent release fence */
1079 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1082 * Perform one-time actions when pushing new ModelAction onto
1085 if (newcurr->is_write())
1086 compute_promises(newcurr);
1087 else if (newcurr->is_relseq_fixup())
1088 compute_relseq_breakwrites(newcurr);
1089 else if (newcurr->is_wait())
1090 newcurr->get_node()->set_misc_max(2);
1091 else if (newcurr->is_notify_one()) {
1092 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1094 return true; /* This was a new ModelAction */
1099 * @brief Establish reads-from relation between two actions
1101 * Perform basic operations involved with establishing a concrete rf relation,
1102 * including setting the ModelAction data and checking for release sequences.
1104 * @param act The action that is reading (must be a read)
1105 * @param rf The action from which we are reading (must be a write)
1107 * @return True if this read established synchronization
1109 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1111 act->set_read_from(rf);
1112 if (rf != NULL && act->is_acquire()) {
1113 rel_heads_list_t release_heads;
1114 get_release_seq_heads(act, act, &release_heads);
1115 int num_heads = release_heads.size();
1116 for (unsigned int i = 0; i < release_heads.size(); i++)
1117 if (!act->synchronize_with(release_heads[i])) {
1118 set_bad_synchronization();
1121 return num_heads > 0;
1127 * @brief Check whether a model action is enabled.
1129 * Checks whether a lock or join operation would be successful (i.e., is the
1130 * lock already locked, or is the joined thread already complete). If not, put
1131 * the action in a waiter list.
1133 * @param curr is the ModelAction to check whether it is enabled.
1134 * @return a bool that indicates whether the action is enabled.
1136 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1137 if (curr->is_lock()) {
1138 std::mutex * lock = (std::mutex *)curr->get_location();
1139 struct std::mutex_state * state = lock->get_state();
1140 if (state->islocked) {
1141 //Stick the action in the appropriate waiting queue
1142 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1145 } else if (curr->get_type() == THREAD_JOIN) {
1146 Thread *blocking = (Thread *)curr->get_location();
1147 if (!blocking->is_complete()) {
1148 blocking->push_wait_list(curr);
1157 * Stores the ModelAction for the current thread action. Call this
1158 * immediately before switching from user- to system-context to pass
1159 * data between them.
1160 * @param act The ModelAction created by the user-thread action
1162 void ModelChecker::set_current_action(ModelAction *act) {
1163 priv->current_action = act;
1167 * This is the heart of the model checker routine. It performs model-checking
1168 * actions corresponding to a given "current action." Among other processes, it
1169 * calculates reads-from relationships, updates synchronization clock vectors,
1170 * forms a memory_order constraints graph, and handles replay/backtrack
1171 * execution when running permutations of previously-observed executions.
1173 * @param curr The current action to process
1174 * @return The next Thread that must be executed. May be NULL if ModelChecker
1175 * makes no choice (e.g., according to replay execution, combining RMW actions,
1178 Thread * ModelChecker::check_current_action(ModelAction *curr)
1181 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1183 if (!check_action_enabled(curr)) {
1184 /* Make the execution look like we chose to run this action
1185 * much later, when a lock/join can succeed */
1186 get_current_thread()->set_pending(curr);
1187 scheduler->sleep(get_current_thread());
1188 return get_next_thread(NULL);
1191 bool newly_explored = initialize_curr_action(&curr);
1193 wake_up_sleeping_actions(curr);
1195 /* Add the action to lists before any other model-checking tasks */
1196 if (!second_part_of_rmw)
1197 add_action_to_lists(curr);
1199 /* Build may_read_from set for newly-created actions */
1200 if (newly_explored && curr->is_read())
1201 build_reads_from_past(curr);
1203 /* Initialize work_queue with the "current action" work */
1204 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1205 while (!work_queue.empty() && !has_asserted()) {
1206 WorkQueueEntry work = work_queue.front();
1207 work_queue.pop_front();
1209 switch (work.type) {
1210 case WORK_CHECK_CURR_ACTION: {
1211 ModelAction *act = work.action;
1212 bool update = false; /* update this location's release seq's */
1213 bool update_all = false; /* update all release seq's */
1215 if (process_thread_action(curr))
1218 if (act->is_read() && process_read(act, second_part_of_rmw))
1221 if (act->is_write() && process_write(act))
1224 if (act->is_fence() && process_fence(act))
1227 if (act->is_mutex_op() && process_mutex(act))
1230 if (act->is_relseq_fixup())
1231 process_relseq_fixup(curr, &work_queue);
1234 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1236 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1239 case WORK_CHECK_RELEASE_SEQ:
1240 resolve_release_sequences(work.location, &work_queue);
1242 case WORK_CHECK_MO_EDGES: {
1243 /** @todo Complete verification of work_queue */
1244 ModelAction *act = work.action;
1245 bool updated = false;
1247 if (act->is_read()) {
1248 const ModelAction *rf = act->get_reads_from();
1249 if (rf != NULL && r_modification_order(act, rf))
1252 if (act->is_write()) {
1253 if (w_modification_order(act))
1256 mo_graph->commitChanges();
1259 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1268 check_curr_backtracking(curr);
1269 set_backtracking(curr);
1270 return get_next_thread(curr);
1273 void ModelChecker::check_curr_backtracking(ModelAction * curr) {
1274 Node *currnode = curr->get_node();
1275 Node *parnode = currnode->get_parent();
1277 if ((!parnode->backtrack_empty() ||
1278 !currnode->misc_empty() ||
1279 !currnode->read_from_empty() ||
1280 !currnode->future_value_empty() ||
1281 !currnode->promise_empty() ||
1282 !currnode->relseq_break_empty())
1283 && (!priv->next_backtrack ||
1284 *curr > *priv->next_backtrack)) {
1285 priv->next_backtrack = curr;
1289 bool ModelChecker::promises_expired() const
1291 for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
1292 Promise *promise = (*promises)[promise_index];
1293 if (promise->get_expiration()<priv->used_sequence_numbers) {
1301 * This is the strongest feasibility check available.
1302 * @return whether the current trace (partial or complete) must be a prefix of
1305 bool ModelChecker::isfeasibleprefix() const
1307 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1311 * Returns whether the current completed trace is feasible, except for pending
1312 * release sequences.
1314 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1316 if (DBG_ENABLED() && promises->size() != 0)
1317 DEBUG("Infeasible: unrevolved promises\n");
1319 return !is_infeasible() && promises->size() == 0;
1323 * Check if the current partial trace is infeasible. Does not check any
1324 * end-of-execution flags, which might rule out the execution. Thus, this is
1325 * useful only for ruling an execution as infeasible.
1326 * @return whether the current partial trace is infeasible.
1328 bool ModelChecker::is_infeasible() const
1330 if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
1331 DEBUG("Infeasible: RMW violation\n");
1333 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1337 * Check If the current partial trace is infeasible, while ignoring
1338 * infeasibility related to 2 RMW's reading from the same store. It does not
1339 * check end-of-execution feasibility.
1340 * @see ModelChecker::is_infeasible
1341 * @return whether the current partial trace is infeasible, ignoring multiple
1342 * RMWs reading from the same store.
1344 bool ModelChecker::is_infeasible_ignoreRMW() const
1346 if (DBG_ENABLED()) {
1347 if (mo_graph->checkForCycles())
1348 DEBUG("Infeasible: modification order cycles\n");
1349 if (priv->failed_promise)
1350 DEBUG("Infeasible: failed promise\n");
1351 if (priv->too_many_reads)
1352 DEBUG("Infeasible: too many reads\n");
1353 if (priv->bad_synchronization)
1354 DEBUG("Infeasible: bad synchronization ordering\n");
1355 if (promises_expired())
1356 DEBUG("Infeasible: promises expired\n");
1358 return mo_graph->checkForCycles() || priv->failed_promise ||
1359 priv->too_many_reads || priv->bad_synchronization ||
1363 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1364 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1365 ModelAction *lastread = get_last_action(act->get_tid());
1366 lastread->process_rmw(act);
1367 if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
1368 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1369 mo_graph->commitChanges();
1375 * Checks whether a thread has read from the same write for too many times
1376 * without seeing the effects of a later write.
1379 * 1) there must a different write that we could read from that would satisfy the modification order,
1380 * 2) we must have read from the same value in excess of maxreads times, and
1381 * 3) that other write must have been in the reads_from set for maxreads times.
1383 * If so, we decide that the execution is no longer feasible.
1385 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) {
1386 if (params.maxreads != 0) {
1388 if (curr->get_node()->get_read_from_size() <= 1)
1390 //Must make sure that execution is currently feasible... We could
1391 //accidentally clear by rolling back
1392 if (is_infeasible())
1394 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1395 int tid = id_to_int(curr->get_tid());
1398 if ((int)thrd_lists->size() <= tid)
1400 action_list_t *list = &(*thrd_lists)[tid];
1402 action_list_t::reverse_iterator rit = list->rbegin();
1403 /* Skip past curr */
1404 for (; (*rit) != curr; rit++)
1406 /* go past curr now */
1409 action_list_t::reverse_iterator ritcopy = rit;
1410 //See if we have enough reads from the same value
1412 for (; count < params.maxreads; rit++,count++) {
1413 if (rit==list->rend())
1415 ModelAction *act = *rit;
1416 if (!act->is_read())
1419 if (act->get_reads_from() != rf)
1421 if (act->get_node()->get_read_from_size() <= 1)
1424 for (int i = 0; i<curr->get_node()->get_read_from_size(); i++) {
1426 const ModelAction * write = curr->get_node()->get_read_from_at(i);
1428 //Need a different write
1432 /* Test to see whether this is a feasible write to read from*/
1433 mo_graph->startChanges();
1434 r_modification_order(curr, write);
1435 bool feasiblereadfrom = !is_infeasible();
1436 mo_graph->rollbackChanges();
1438 if (!feasiblereadfrom)
1442 bool feasiblewrite = true;
1443 //new we need to see if this write works for everyone
1445 for (int loop = count; loop>0; loop--,rit++) {
1446 ModelAction *act=*rit;
1447 bool foundvalue = false;
1448 for (int j = 0; j<act->get_node()->get_read_from_size(); j++) {
1449 if (act->get_node()->get_read_from_at(j)==write) {
1455 feasiblewrite = false;
1459 if (feasiblewrite) {
1460 priv->too_many_reads = true;
1468 * Updates the mo_graph with the constraints imposed from the current
1471 * Basic idea is the following: Go through each other thread and find
1472 * the lastest action that happened before our read. Two cases:
1474 * (1) The action is a write => that write must either occur before
1475 * the write we read from or be the write we read from.
1477 * (2) The action is a read => the write that that action read from
1478 * must occur before the write we read from or be the same write.
1480 * @param curr The current action. Must be a read.
1481 * @param rf The action that curr reads from. Must be a write.
1482 * @return True if modification order edges were added; false otherwise
1484 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1486 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1489 ASSERT(curr->is_read());
1491 /* Last SC fence in the current thread */
1492 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1494 /* Iterate over all threads */
1495 for (i = 0; i < thrd_lists->size(); i++) {
1496 /* Last SC fence in thread i */
1497 ModelAction *last_sc_fence_thread_local = NULL;
1498 if (int_to_id((int)i) != curr->get_tid())
1499 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1501 /* Last SC fence in thread i, before last SC fence in current thread */
1502 ModelAction *last_sc_fence_thread_before = NULL;
1503 if (last_sc_fence_local)
1504 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1506 /* Iterate over actions in thread, starting from most recent */
1507 action_list_t *list = &(*thrd_lists)[i];
1508 action_list_t::reverse_iterator rit;
1509 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1510 ModelAction *act = *rit;
1512 if (act->is_write() && act != rf && act != curr) {
1513 /* C++, Section 29.3 statement 5 */
1514 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1515 *act < *last_sc_fence_thread_local) {
1516 mo_graph->addEdge(act, rf);
1520 /* C++, Section 29.3 statement 4 */
1521 else if (act->is_seqcst() && last_sc_fence_local &&
1522 *act < *last_sc_fence_local) {
1523 mo_graph->addEdge(act, rf);
1527 /* C++, Section 29.3 statement 6 */
1528 else if (last_sc_fence_thread_before &&
1529 *act < *last_sc_fence_thread_before) {
1530 mo_graph->addEdge(act, rf);
1537 * Include at most one act per-thread that "happens
1538 * before" curr. Don't consider reflexively.
1540 if (act->happens_before(curr) && act != curr) {
1541 if (act->is_write()) {
1543 mo_graph->addEdge(act, rf);
1547 const ModelAction *prevreadfrom = act->get_reads_from();
1548 //if the previous read is unresolved, keep going...
1549 if (prevreadfrom == NULL)
1552 if (rf != prevreadfrom) {
1553 mo_graph->addEdge(prevreadfrom, rf);
1565 /** This method fixes up the modification order when we resolve a
1566 * promises. The basic problem is that actions that occur after the
1567 * read curr could not property add items to the modification order
1570 * So for each thread, we find the earliest item that happens after
1571 * the read curr. This is the item we have to fix up with additional
1572 * constraints. If that action is write, we add a MO edge between
1573 * the Action rf and that action. If the action is a read, we add a
1574 * MO edge between the Action rf, and whatever the read accessed.
1576 * @param curr is the read ModelAction that we are fixing up MO edges for.
1577 * @param rf is the write ModelAction that curr reads from.
1580 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1582 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1584 ASSERT(curr->is_read());
1586 /* Iterate over all threads */
1587 for (i = 0; i < thrd_lists->size(); i++) {
1588 /* Iterate over actions in thread, starting from most recent */
1589 action_list_t *list = &(*thrd_lists)[i];
1590 action_list_t::reverse_iterator rit;
1591 ModelAction *lastact = NULL;
1593 /* Find last action that happens after curr that is either not curr or a rmw */
1594 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1595 ModelAction *act = *rit;
1596 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1602 /* Include at most one act per-thread that "happens before" curr */
1603 if (lastact != NULL) {
1604 if (lastact==curr) {
1605 //Case 1: The resolved read is a RMW, and we need to make sure
1606 //that the write portion of the RMW mod order after rf
1608 mo_graph->addEdge(rf, lastact);
1609 } else if (lastact->is_read()) {
1610 //Case 2: The resolved read is a normal read and the next
1611 //operation is a read, and we need to make sure the value read
1612 //is mod ordered after rf
1614 const ModelAction *postreadfrom = lastact->get_reads_from();
1615 if (postreadfrom != NULL&&rf != postreadfrom)
1616 mo_graph->addEdge(rf, postreadfrom);
1618 //Case 3: The resolved read is a normal read and the next
1619 //operation is a write, and we need to make sure that the
1620 //write is mod ordered after rf
1622 mo_graph->addEdge(rf, lastact);
1630 * Updates the mo_graph with the constraints imposed from the current write.
1632 * Basic idea is the following: Go through each other thread and find
1633 * the lastest action that happened before our write. Two cases:
1635 * (1) The action is a write => that write must occur before
1638 * (2) The action is a read => the write that that action read from
1639 * must occur before the current write.
1641 * This method also handles two other issues:
1643 * (I) Sequential Consistency: Making sure that if the current write is
1644 * seq_cst, that it occurs after the previous seq_cst write.
1646 * (II) Sending the write back to non-synchronizing reads.
1648 * @param curr The current action. Must be a write.
1649 * @return True if modification order edges were added; false otherwise
1651 bool ModelChecker::w_modification_order(ModelAction *curr)
1653 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1656 ASSERT(curr->is_write());
1658 if (curr->is_seqcst()) {
1659 /* We have to at least see the last sequentially consistent write,
1660 so we are initialized. */
1661 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1662 if (last_seq_cst != NULL) {
1663 mo_graph->addEdge(last_seq_cst, curr);
1668 /* Last SC fence in the current thread */
1669 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1671 /* Iterate over all threads */
1672 for (i = 0; i < thrd_lists->size(); i++) {
1673 /* Last SC fence in thread i, before last SC fence in current thread */
1674 ModelAction *last_sc_fence_thread_before = NULL;
1675 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1676 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1678 /* Iterate over actions in thread, starting from most recent */
1679 action_list_t *list = &(*thrd_lists)[i];
1680 action_list_t::reverse_iterator rit;
1681 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1682 ModelAction *act = *rit;
1685 * 1) If RMW and it actually read from something, then we
1686 * already have all relevant edges, so just skip to next
1689 * 2) If RMW and it didn't read from anything, we should
1690 * whatever edge we can get to speed up convergence.
1692 * 3) If normal write, we need to look at earlier actions, so
1693 * continue processing list.
1695 if (curr->is_rmw()) {
1696 if (curr->get_reads_from()!=NULL)
1704 /* C++, Section 29.3 statement 7 */
1705 if (last_sc_fence_thread_before && act->is_write() &&
1706 *act < *last_sc_fence_thread_before) {
1707 mo_graph->addEdge(act, curr);
1713 * Include at most one act per-thread that "happens
1716 if (act->happens_before(curr)) {
1718 * Note: if act is RMW, just add edge:
1720 * The following edge should be handled elsewhere:
1721 * readfrom(act) --mo--> act
1723 if (act->is_write())
1724 mo_graph->addEdge(act, curr);
1725 else if (act->is_read()) {
1726 //if previous read accessed a null, just keep going
1727 if (act->get_reads_from() == NULL)
1729 mo_graph->addEdge(act->get_reads_from(), curr);
1733 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1734 !act->same_thread(curr)) {
1735 /* We have an action that:
1736 (1) did not happen before us
1737 (2) is a read and we are a write
1738 (3) cannot synchronize with us
1739 (4) is in a different thread
1741 that read could potentially read from our write. Note that
1742 these checks are overly conservative at this point, we'll
1743 do more checks before actually removing the
1747 if (thin_air_constraint_may_allow(curr, act)) {
1748 if (!is_infeasible() ||
1749 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1750 struct PendingFutureValue pfv = {curr,act};
1751 futurevalues->push_back(pfv);
1761 /** Arbitrary reads from the future are not allowed. Section 29.3
1762 * part 9 places some constraints. This method checks one result of constraint
1763 * constraint. Others require compiler support. */
1764 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
1765 if (!writer->is_rmw())
1768 if (!reader->is_rmw())
1771 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1772 if (search == reader)
1774 if (search->get_tid() == reader->get_tid() &&
1775 search->happens_before(reader))
1783 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1784 * some constraints. This method checks one the following constraint (others
1785 * require compiler support):
1787 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1789 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1791 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1793 /* Iterate over all threads */
1794 for (i = 0; i < thrd_lists->size(); i++) {
1795 const ModelAction *write_after_read = NULL;
1797 /* Iterate over actions in thread, starting from most recent */
1798 action_list_t *list = &(*thrd_lists)[i];
1799 action_list_t::reverse_iterator rit;
1800 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1801 ModelAction *act = *rit;
1803 if (!reader->happens_before(act))
1805 else if (act->is_write())
1806 write_after_read = act;
1807 else if (act->is_read() && act->get_reads_from() != NULL && act != reader) {
1808 write_after_read = act->get_reads_from();
1812 if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
1819 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1820 * The ModelAction under consideration is expected to be taking part in
1821 * release/acquire synchronization as an object of the "reads from" relation.
1822 * Note that this can only provide release sequence support for RMW chains
1823 * which do not read from the future, as those actions cannot be traced until
1824 * their "promise" is fulfilled. Similarly, we may not even establish the
1825 * presence of a release sequence with certainty, as some modification order
1826 * constraints may be decided further in the future. Thus, this function
1827 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1828 * and a boolean representing certainty.
1830 * @param rf The action that might be part of a release sequence. Must be a
1832 * @param release_heads A pass-by-reference style return parameter. After
1833 * execution of this function, release_heads will contain the heads of all the
1834 * relevant release sequences, if any exists with certainty
1835 * @param pending A pass-by-reference style return parameter which is only used
1836 * when returning false (i.e., uncertain). Returns most information regarding
1837 * an uncertain release sequence, including any write operations that might
1838 * break the sequence.
1839 * @return true, if the ModelChecker is certain that release_heads is complete;
1842 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1843 rel_heads_list_t *release_heads,
1844 struct release_seq *pending) const
1846 /* Only check for release sequences if there are no cycles */
1847 if (mo_graph->checkForCycles())
1851 ASSERT(rf->is_write());
1853 if (rf->is_release())
1854 release_heads->push_back(rf);
1855 else if (rf->get_last_fence_release())
1856 release_heads->push_back(rf->get_last_fence_release());
1858 break; /* End of RMW chain */
1860 /** @todo Need to be smarter here... In the linux lock
1861 * example, this will run to the beginning of the program for
1863 /** @todo The way to be smarter here is to keep going until 1
1864 * thread has a release preceded by an acquire and you've seen
1867 /* acq_rel RMW is a sufficient stopping condition */
1868 if (rf->is_acquire() && rf->is_release())
1869 return true; /* complete */
1871 rf = rf->get_reads_from();
1874 /* read from future: need to settle this later */
1876 return false; /* incomplete */
1879 if (rf->is_release())
1880 return true; /* complete */
1882 /* else relaxed write
1883 * - check for fence-release in the same thread (29.8, stmt. 3)
1884 * - check modification order for contiguous subsequence
1885 * -> rf must be same thread as release */
1887 const ModelAction *fence_release = rf->get_last_fence_release();
1888 /* Synchronize with a fence-release unconditionally; we don't need to
1889 * find any more "contiguous subsequence..." for it */
1891 release_heads->push_back(fence_release);
1893 int tid = id_to_int(rf->get_tid());
1894 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1895 action_list_t *list = &(*thrd_lists)[tid];
1896 action_list_t::const_reverse_iterator rit;
1898 /* Find rf in the thread list */
1899 rit = std::find(list->rbegin(), list->rend(), rf);
1900 ASSERT(rit != list->rend());
1902 /* Find the last {write,fence}-release */
1903 for (; rit != list->rend(); rit++) {
1904 if (fence_release && *(*rit) < *fence_release)
1906 if ((*rit)->is_release())
1909 if (rit == list->rend()) {
1910 /* No write-release in this thread */
1911 return true; /* complete */
1912 } else if (fence_release && *(*rit) < *fence_release) {
1913 /* The fence-release is more recent (and so, "stronger") than
1914 * the most recent write-release */
1915 return true; /* complete */
1916 } /* else, need to establish contiguous release sequence */
1917 ModelAction *release = *rit;
1919 ASSERT(rf->same_thread(release));
1921 pending->writes.clear();
1923 bool certain = true;
1924 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1925 if (id_to_int(rf->get_tid()) == (int)i)
1927 list = &(*thrd_lists)[i];
1929 /* Can we ensure no future writes from this thread may break
1930 * the release seq? */
1931 bool future_ordered = false;
1933 ModelAction *last = get_last_action(int_to_id(i));
1934 Thread *th = get_thread(int_to_id(i));
1935 if ((last && rf->happens_before(last)) ||
1938 future_ordered = true;
1940 ASSERT(!th->is_model_thread() || future_ordered);
1942 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1943 const ModelAction *act = *rit;
1944 /* Reach synchronization -> this thread is complete */
1945 if (act->happens_before(release))
1947 if (rf->happens_before(act)) {
1948 future_ordered = true;
1952 /* Only non-RMW writes can break release sequences */
1953 if (!act->is_write() || act->is_rmw())
1956 /* Check modification order */
1957 if (mo_graph->checkReachable(rf, act)) {
1958 /* rf --mo--> act */
1959 future_ordered = true;
1962 if (mo_graph->checkReachable(act, release))
1963 /* act --mo--> release */
1965 if (mo_graph->checkReachable(release, act) &&
1966 mo_graph->checkReachable(act, rf)) {
1967 /* release --mo-> act --mo--> rf */
1968 return true; /* complete */
1970 /* act may break release sequence */
1971 pending->writes.push_back(act);
1974 if (!future_ordered)
1975 certain = false; /* This thread is uncertain */
1979 release_heads->push_back(release);
1980 pending->writes.clear();
1982 pending->release = release;
1989 * An interface for getting the release sequence head(s) with which a
1990 * given ModelAction must synchronize. This function only returns a non-empty
1991 * result when it can locate a release sequence head with certainty. Otherwise,
1992 * it may mark the internal state of the ModelChecker so that it will handle
1993 * the release sequence at a later time, causing @a acquire to update its
1994 * synchronization at some later point in execution.
1996 * @param acquire The 'acquire' action that may synchronize with a release
1998 * @param read The read action that may read from a release sequence; this may
1999 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2000 * when 'acquire' is a fence-acquire)
2001 * @param release_heads A pass-by-reference return parameter. Will be filled
2002 * with the head(s) of the release sequence(s), if they exists with certainty.
2003 * @see ModelChecker::release_seq_heads
2005 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2006 ModelAction *read, rel_heads_list_t *release_heads)
2008 const ModelAction *rf = read->get_reads_from();
2009 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2010 sequence->acquire = acquire;
2011 sequence->read = read;
2013 if (!release_seq_heads(rf, release_heads, sequence)) {
2014 /* add act to 'lazy checking' list */
2015 pending_rel_seqs->push_back(sequence);
2017 snapshot_free(sequence);
2022 * Attempt to resolve all stashed operations that might synchronize with a
2023 * release sequence for a given location. This implements the "lazy" portion of
2024 * determining whether or not a release sequence was contiguous, since not all
2025 * modification order information is present at the time an action occurs.
2027 * @param location The location/object that should be checked for release
2028 * sequence resolutions. A NULL value means to check all locations.
2029 * @param work_queue The work queue to which to add work items as they are
2031 * @return True if any updates occurred (new synchronization, new mo_graph
2034 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2036 bool updated = false;
2037 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2038 while (it != pending_rel_seqs->end()) {
2039 struct release_seq *pending = *it;
2040 ModelAction *acquire = pending->acquire;
2041 const ModelAction *read = pending->read;
2043 /* Only resolve sequences on the given location, if provided */
2044 if (location && read->get_location() != location) {
2049 const ModelAction *rf = read->get_reads_from();
2050 rel_heads_list_t release_heads;
2052 complete = release_seq_heads(rf, &release_heads, pending);
2053 for (unsigned int i = 0; i < release_heads.size(); i++) {
2054 if (!acquire->has_synchronized_with(release_heads[i])) {
2055 if (acquire->synchronize_with(release_heads[i]))
2058 set_bad_synchronization();
2063 /* Re-check all pending release sequences */
2064 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2065 /* Re-check read-acquire for mo_graph edges */
2066 if (acquire->is_read())
2067 work_queue->push_back(MOEdgeWorkEntry(acquire));
2069 /* propagate synchronization to later actions */
2070 action_list_t::reverse_iterator rit = action_trace->rbegin();
2071 for (; (*rit) != acquire; rit++) {
2072 ModelAction *propagate = *rit;
2073 if (acquire->happens_before(propagate)) {
2074 propagate->synchronize_with(acquire);
2075 /* Re-check 'propagate' for mo_graph edges */
2076 work_queue->push_back(MOEdgeWorkEntry(propagate));
2081 it = pending_rel_seqs->erase(it);
2082 snapshot_free(pending);
2088 // If we resolved promises or data races, see if we have realized a data race.
2095 * Performs various bookkeeping operations for the current ModelAction. For
2096 * instance, adds action to the per-object, per-thread action vector and to the
2097 * action trace list of all thread actions.
2099 * @param act is the ModelAction to add.
2101 void ModelChecker::add_action_to_lists(ModelAction *act)
2103 int tid = id_to_int(act->get_tid());
2104 action_trace->push_back(act);
2106 get_safe_ptr_action(obj_map, act->get_location())->push_back(act);
2108 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2109 if (tid >= (int)vec->size())
2110 vec->resize(priv->next_thread_id);
2111 (*vec)[tid].push_back(act);
2113 if ((int)thrd_last_action->size() <= tid)
2114 thrd_last_action->resize(get_num_threads());
2115 (*thrd_last_action)[tid] = act;
2117 if (act->is_fence() && act->is_release()) {
2118 if ((int)thrd_last_fence_release->size() <= tid)
2119 thrd_last_fence_release->resize(get_num_threads());
2120 (*thrd_last_fence_release)[tid] = act;
2123 if (act->is_wait()) {
2124 void *mutex_loc=(void *) act->get_value();
2125 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2127 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2128 if (tid >= (int)vec->size())
2129 vec->resize(priv->next_thread_id);
2130 (*vec)[tid].push_back(act);
2135 * @brief Get the last action performed by a particular Thread
2136 * @param tid The thread ID of the Thread in question
2137 * @return The last action in the thread
2139 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2141 int threadid = id_to_int(tid);
2142 if (threadid < (int)thrd_last_action->size())
2143 return (*thrd_last_action)[id_to_int(tid)];
2149 * @brief Get the last fence release performed by a particular Thread
2150 * @param tid The thread ID of the Thread in question
2151 * @return The last fence release in the thread, if one exists; NULL otherwise
2153 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2155 int threadid = id_to_int(tid);
2156 if (threadid < (int)thrd_last_fence_release->size())
2157 return (*thrd_last_fence_release)[id_to_int(tid)];
2163 * Gets the last memory_order_seq_cst write (in the total global sequence)
2164 * performed on a particular object (i.e., memory location), not including the
2166 * @param curr The current ModelAction; also denotes the object location to
2168 * @return The last seq_cst write
2170 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2172 void *location = curr->get_location();
2173 action_list_t *list = get_safe_ptr_action(obj_map, location);
2174 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2175 action_list_t::reverse_iterator rit;
2176 for (rit = list->rbegin(); rit != list->rend(); rit++)
2177 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2183 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2184 * performed in a particular thread, prior to a particular fence.
2185 * @param tid The ID of the thread to check
2186 * @param before_fence The fence from which to begin the search; if NULL, then
2187 * search for the most recent fence in the thread.
2188 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2190 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2192 /* All fences should have NULL location */
2193 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2194 action_list_t::reverse_iterator rit = list->rbegin();
2197 for (; rit != list->rend(); rit++)
2198 if (*rit == before_fence)
2201 ASSERT(*rit == before_fence);
2205 for (; rit != list->rend(); rit++)
2206 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2212 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2213 * location). This function identifies the mutex according to the current
2214 * action, which is presumed to perform on the same mutex.
2215 * @param curr The current ModelAction; also denotes the object location to
2217 * @return The last unlock operation
2219 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2221 void *location = curr->get_location();
2222 action_list_t *list = get_safe_ptr_action(obj_map, location);
2223 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2224 action_list_t::reverse_iterator rit;
2225 for (rit = list->rbegin(); rit != list->rend(); rit++)
2226 if ((*rit)->is_unlock() || (*rit)->is_wait())
2231 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2233 ModelAction *parent = get_last_action(tid);
2235 parent = get_thread(tid)->get_creation();
2240 * Returns the clock vector for a given thread.
2241 * @param tid The thread whose clock vector we want
2242 * @return Desired clock vector
2244 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2246 return get_parent_action(tid)->get_cv();
2250 * Resolve a set of Promises with a current write. The set is provided in the
2251 * Node corresponding to @a write.
2252 * @param write The ModelAction that is fulfilling Promises
2253 * @return True if promises were resolved; false otherwise
2255 bool ModelChecker::resolve_promises(ModelAction *write)
2257 bool resolved = false;
2258 std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
2260 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2261 Promise *promise = (*promises)[promise_index];
2262 if (write->get_node()->get_promise(i)) {
2263 ModelAction *read = promise->get_action();
2264 if (read->is_rmw()) {
2265 mo_graph->addRMWEdge(write, read);
2267 read_from(read, write);
2268 //First fix up the modification order for actions that happened
2270 r_modification_order(read, write);
2271 //Next fix up the modification order for actions that happened
2273 post_r_modification_order(read, write);
2274 //Make sure the promise's value matches the write's value
2275 ASSERT(promise->get_value() == write->get_value());
2278 promises->erase(promises->begin() + promise_index);
2279 threads_to_check.push_back(read->get_tid());
2286 //Check whether reading these writes has made threads unable to
2289 for(unsigned int i=0;i<threads_to_check.size();i++)
2290 mo_check_promises(threads_to_check[i], write);
2296 * Compute the set of promises that could potentially be satisfied by this
2297 * action. Note that the set computation actually appears in the Node, not in
2299 * @param curr The ModelAction that may satisfy promises
2301 void ModelChecker::compute_promises(ModelAction *curr)
2303 for (unsigned int i = 0; i < promises->size(); i++) {
2304 Promise *promise = (*promises)[i];
2305 const ModelAction *act = promise->get_action();
2306 if (!act->happens_before(curr) &&
2308 !act->could_synchronize_with(curr) &&
2309 !act->same_thread(curr) &&
2310 act->get_location() == curr->get_location() &&
2311 promise->get_value() == curr->get_value()) {
2312 curr->get_node()->set_promise(i, act->is_rmw());
2317 /** Checks promises in response to change in ClockVector Threads. */
2318 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2320 for (unsigned int i = 0; i < promises->size(); i++) {
2321 Promise *promise = (*promises)[i];
2322 const ModelAction *act = promise->get_action();
2323 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2324 merge_cv->synchronized_since(act)) {
2325 if (promise->increment_threads(tid)) {
2326 //Promise has failed
2327 priv->failed_promise = true;
2334 void ModelChecker::check_promises_thread_disabled() {
2335 for (unsigned int i = 0; i < promises->size(); i++) {
2336 Promise *promise = (*promises)[i];
2337 if (promise->check_promise()) {
2338 priv->failed_promise = true;
2344 /** Checks promises in response to addition to modification order for threads.
2346 * pthread is the thread that performed the read that created the promise
2348 * pread is the read that created the promise
2350 * pwrite is either the first write to same location as pread by
2351 * pthread that is sequenced after pread or the value read by the
2352 * first read to the same lcoation as pread by pthread that is
2353 * sequenced after pread..
2355 * 1. If tid=pthread, then we check what other threads are reachable
2356 * through the mode order starting with pwrite. Those threads cannot
2357 * perform a write that will resolve the promise due to modification
2358 * order constraints.
2360 * 2. If the tid is not pthread, we check whether pwrite can reach the
2361 * action write through the modification order. If so, that thread
2362 * cannot perform a future write that will resolve the promise due to
2363 * modificatin order constraints.
2365 * @parem tid The thread that either read from the model action
2366 * write, or actually did the model action write.
2368 * @parem write The ModelAction representing the relevant write.
2371 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
2372 void * location = write->get_location();
2373 for (unsigned int i = 0; i < promises->size(); i++) {
2374 Promise *promise = (*promises)[i];
2375 const ModelAction *act = promise->get_action();
2377 //Is this promise on the same location?
2378 if ( act->get_location() != location )
2381 //same thread as the promise
2382 if ( act->get_tid()==tid ) {
2384 //do we have a pwrite for the promise, if not, set it
2385 if (promise->get_write() == NULL ) {
2386 promise->set_write(write);
2387 //The pwrite cannot happen before the promise
2388 if (write->happens_before(act) && (write != act)) {
2389 priv->failed_promise = true;
2393 if (mo_graph->checkPromise(write, promise)) {
2394 priv->failed_promise = true;
2399 //Don't do any lookups twice for the same thread
2400 if (promise->has_sync_thread(tid))
2403 if (promise->get_write()&&mo_graph->checkReachable(promise->get_write(), write)) {
2404 if (promise->increment_threads(tid)) {
2405 priv->failed_promise = true;
2413 * Compute the set of writes that may break the current pending release
2414 * sequence. This information is extracted from previou release sequence
2417 * @param curr The current ModelAction. Must be a release sequence fixup
2420 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2422 if (pending_rel_seqs->empty())
2425 struct release_seq *pending = pending_rel_seqs->back();
2426 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2427 const ModelAction *write = pending->writes[i];
2428 curr->get_node()->add_relseq_break(write);
2431 /* NULL means don't break the sequence; just synchronize */
2432 curr->get_node()->add_relseq_break(NULL);
2436 * Build up an initial set of all past writes that this 'read' action may read
2437 * from. This set is determined by the clock vector's "happens before"
2439 * @param curr is the current ModelAction that we are exploring; it must be a
2442 void ModelChecker::build_reads_from_past(ModelAction *curr)
2444 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2446 ASSERT(curr->is_read());
2448 ModelAction *last_sc_write = NULL;
2450 /* Track whether this object has been initialized */
2451 bool initialized = false;
2453 if (curr->is_seqcst()) {
2454 last_sc_write = get_last_seq_cst_write(curr);
2455 /* We have to at least see the last sequentially consistent write,
2456 so we are initialized. */
2457 if (last_sc_write != NULL)
2461 /* Iterate over all threads */
2462 for (i = 0; i < thrd_lists->size(); i++) {
2463 /* Iterate over actions in thread, starting from most recent */
2464 action_list_t *list = &(*thrd_lists)[i];
2465 action_list_t::reverse_iterator rit;
2466 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2467 ModelAction *act = *rit;
2469 /* Only consider 'write' actions */
2470 if (!act->is_write() || act == curr)
2473 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2474 bool allow_read = true;
2476 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2478 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2482 DEBUG("Adding action to may_read_from:\n");
2483 if (DBG_ENABLED()) {
2487 curr->get_node()->add_read_from(act);
2490 /* Include at most one act per-thread that "happens before" curr */
2491 if (act->happens_before(curr)) {
2499 assert_bug("May read from uninitialized atomic");
2501 if (DBG_ENABLED() || !initialized) {
2502 model_print("Reached read action:\n");
2504 model_print("Printing may_read_from\n");
2505 curr->get_node()->print_may_read_from();
2506 model_print("End printing may_read_from\n");
2510 bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
2512 Node *prevnode=write->get_node()->get_parent();
2514 bool thread_sleep=prevnode->enabled_status(curr->get_tid())==THREAD_SLEEP_SET;
2515 if (write->is_release()&&thread_sleep)
2517 if (!write->is_rmw()) {
2520 if (write->get_reads_from()==NULL)
2522 write=write->get_reads_from();
2526 static void print_list(action_list_t *list, int exec_num = -1)
2528 action_list_t::iterator it;
2530 model_print("---------------------------------------------------------------------\n");
2532 model_print("Execution %d:\n", exec_num);
2534 unsigned int hash=0;
2536 for (it = list->begin(); it != list->end(); it++) {
2538 hash=hash^(hash<<3)^((*it)->hash());
2540 model_print("HASH %u\n", hash);
2541 model_print("---------------------------------------------------------------------\n");
2544 #if SUPPORT_MOD_ORDER_DUMP
2545 void ModelChecker::dumpGraph(char *filename) {
2547 sprintf(buffer, "%s.dot",filename);
2548 FILE *file=fopen(buffer, "w");
2549 fprintf(file, "digraph %s {\n",filename);
2550 mo_graph->dumpNodes(file);
2551 ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
2553 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2554 ModelAction *action=*it;
2555 if (action->is_read()) {
2556 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
2557 if (action->get_reads_from()!=NULL)
2558 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2560 if (thread_array[action->get_tid()] != NULL) {
2561 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2564 thread_array[action->get_tid()]=action;
2566 fprintf(file,"}\n");
2567 model_free(thread_array);
2572 /** @brief Prints an execution trace summary. */
2573 void ModelChecker::print_summary() const
2575 #if SUPPORT_MOD_ORDER_DUMP
2577 char buffername[100];
2578 sprintf(buffername, "exec%04u", stats.num_total);
2579 mo_graph->dumpGraphToFile(buffername);
2580 sprintf(buffername, "graph%04u", stats.num_total);
2581 dumpGraph(buffername);
2584 if (!isfeasibleprefix())
2585 model_print("INFEASIBLE EXECUTION!\n");
2586 print_list(action_trace, stats.num_total);
2591 * Add a Thread to the system for the first time. Should only be called once
2593 * @param t The Thread to add
2595 void ModelChecker::add_thread(Thread *t)
2597 thread_map->put(id_to_int(t->get_id()), t);
2598 scheduler->add_thread(t);
2602 * Removes a thread from the scheduler.
2603 * @param the thread to remove.
2605 void ModelChecker::remove_thread(Thread *t)
2607 scheduler->remove_thread(t);
2611 * @brief Get a Thread reference by its ID
2612 * @param tid The Thread's ID
2613 * @return A Thread reference
2615 Thread * ModelChecker::get_thread(thread_id_t tid) const
2617 return thread_map->get(id_to_int(tid));
2621 * @brief Get a reference to the Thread in which a ModelAction was executed
2622 * @param act The ModelAction
2623 * @return A Thread reference
2625 Thread * ModelChecker::get_thread(ModelAction *act) const
2627 return get_thread(act->get_tid());
2631 * @brief Check if a Thread is currently enabled
2632 * @param t The Thread to check
2633 * @return True if the Thread is currently enabled
2635 bool ModelChecker::is_enabled(Thread *t) const
2637 return scheduler->is_enabled(t);
2641 * @brief Check if a Thread is currently enabled
2642 * @param tid The ID of the Thread to check
2643 * @return True if the Thread is currently enabled
2645 bool ModelChecker::is_enabled(thread_id_t tid) const
2647 return scheduler->is_enabled(tid);
2651 * Switch from a user-context to the "master thread" context (a.k.a. system
2652 * context). This switch is made with the intention of exploring a particular
2653 * model-checking action (described by a ModelAction object). Must be called
2654 * from a user-thread context.
2656 * @param act The current action that will be explored. May be NULL only if
2657 * trace is exiting via an assertion (see ModelChecker::set_assert and
2658 * ModelChecker::has_asserted).
2659 * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
2661 int ModelChecker::switch_to_master(ModelAction *act)
2664 Thread *old = thread_current();
2665 set_current_action(act);
2666 old->set_state(THREAD_READY);
2667 return Thread::swap(old, &system_context);
2671 * Takes the next step in the execution, if possible.
2672 * @return Returns true (success) if a step was taken and false otherwise.
2674 bool ModelChecker::take_step() {
2678 Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL;
2680 if (curr->get_state() == THREAD_READY) {
2681 ASSERT(priv->current_action);
2683 priv->nextThread = check_current_action(priv->current_action);
2684 priv->current_action = NULL;
2686 if (curr->is_blocked() || curr->is_complete())
2687 scheduler->remove_thread(curr);
2692 Thread *next = scheduler->next_thread(priv->nextThread);
2694 /* Infeasible -> don't take any more steps */
2695 if (is_infeasible())
2697 else if (isfeasibleprefix() && have_bug_reports()) {
2702 if (params.bound != 0) {
2703 if (priv->used_sequence_numbers > params.bound) {
2708 DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
2709 next ? id_to_int(next->get_id()) : -1);
2712 * Launch end-of-execution release sequence fixups only when there are:
2714 * (1) no more user threads to run (or when execution replay chooses
2715 * the 'model_thread')
2716 * (2) pending release sequences
2717 * (3) pending assertions (i.e., data races)
2718 * (4) no pending promises
2720 if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
2721 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2722 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2723 pending_rel_seqs->size());
2724 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2725 std::memory_order_seq_cst, NULL, VALUE_NONE,
2727 set_current_action(fixup);
2731 /* next == NULL -> don't take any more steps */
2735 next->set_state(THREAD_RUNNING);
2737 if (next->get_pending() != NULL) {
2738 /* restart a pending action */
2739 set_current_action(next->get_pending());
2740 next->set_pending(NULL);
2741 next->set_state(THREAD_READY);
2745 /* Return false only if swap fails with an error */
2746 return (Thread::swap(&system_context, next) == 0);
2749 /** Wrapper to run the user's main function, with appropriate arguments */
2750 void user_main_wrapper(void *)
2752 user_main(model->params.argc, model->params.argv);
2755 /** @brief Run ModelChecker for the user program */
2756 void ModelChecker::run()
2761 /* Start user program */
2762 add_thread(new Thread(&user_thread, &user_main_wrapper, NULL));
2764 /* Wait for all threads to complete */
2765 while (take_step());
2766 } while (next_execution());