10 #include "snapshot-interface.h"
12 #include "clockvector.h"
13 #include "cyclegraph.h"
16 #include "threads-model.h"
19 #define INITIAL_THREAD_ID 0
24 bug_message(const char *str) {
25 const char *fmt = " [BUG] %s\n";
26 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
27 sprintf(msg, fmt, str);
29 ~bug_message() { if (msg) snapshot_free(msg); }
32 void print() { model_print("%s", msg); }
38 * Structure for holding small ModelChecker members that should be snapshotted
40 struct model_snapshot_members {
41 model_snapshot_members() :
43 /* First thread created will have id INITIAL_THREAD_ID */
44 next_thread_id(INITIAL_THREAD_ID),
45 used_sequence_numbers(0),
49 failed_promise(false),
50 too_many_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 ModelAction *current_action;
62 unsigned int next_thread_id;
63 modelclock_t used_sequence_numbers;
64 ModelAction *next_backtrack;
65 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
66 struct execution_stats stats;
69 /** @brief Incorrectly-ordered synchronization was made */
70 bool bad_synchronization;
76 /** @brief Constructor */
77 ModelChecker::ModelChecker(struct model_params params) :
78 /* Initialize default scheduler */
80 scheduler(new Scheduler()),
82 earliest_diverge(NULL),
83 action_trace(new action_list_t()),
84 thread_map(new HashTable<int, Thread *, int>()),
85 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
86 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
89 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
90 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
91 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
92 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
93 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
123 delete thrd_last_fence_release;
130 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
132 action_list_t *tmp = hash->get(ptr);
134 tmp = new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
142 std::vector<action_list_t> *tmp = hash->get(ptr);
144 tmp = new std::vector<action_list_t>();
151 * Restores user program to initial state and resets all model-checker data
154 void ModelChecker::reset_to_initial_state()
156 DEBUG("+++ Resetting to initial state +++\n");
157 node_stack->reset_execution();
159 /* Print all model-checker output before rollback */
162 snapshot_backtrack_before(0);
165 /** @return a thread ID for a new Thread */
166 thread_id_t ModelChecker::get_next_id()
168 return priv->next_thread_id++;
171 /** @return the number of user threads created during this execution */
172 unsigned int ModelChecker::get_num_threads() const
174 return priv->next_thread_id;
178 * Must be called from user-thread context (e.g., through the global
179 * thread_current() interface)
181 * @return The currently executing Thread.
183 Thread * ModelChecker::get_current_thread() const
185 return scheduler->get_current_thread();
188 /** @return a sequence number for a new ModelAction */
189 modelclock_t ModelChecker::get_next_seq_num()
191 return ++priv->used_sequence_numbers;
194 Node * ModelChecker::get_curr_node() const
196 return node_stack->get_head();
200 * @brief Choose the next thread to execute.
202 * This function chooses the next thread that should execute. It can force the
203 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
204 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
205 * The model-checker may have no preference regarding the next thread (i.e.,
206 * when exploring a new execution ordering), in which case this will return
208 * @param curr The current ModelAction. This action might guide the choice of
210 * @return The next thread to run. If the model-checker has no preference, NULL.
212 Thread * ModelChecker::get_next_thread(ModelAction *curr)
217 /* Do not split atomic actions. */
219 return thread_current();
220 else if (curr->get_type() == THREAD_CREATE)
221 return curr->get_thread_operand();
224 /* Have we completed exploring the preselected path? */
228 /* Else, we are trying to replay an execution */
229 ModelAction *next = node_stack->get_next()->get_action();
231 if (next == diverge) {
232 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
233 earliest_diverge = diverge;
235 Node *nextnode = next->get_node();
236 Node *prevnode = nextnode->get_parent();
237 scheduler->update_sleep_set(prevnode);
239 /* Reached divergence point */
240 if (nextnode->increment_misc()) {
241 /* The next node will try to satisfy a different misc_index values. */
242 tid = next->get_tid();
243 node_stack->pop_restofstack(2);
244 } else if (nextnode->increment_promise()) {
245 /* The next node will try to satisfy a different set of promises. */
246 tid = next->get_tid();
247 node_stack->pop_restofstack(2);
248 } else if (nextnode->increment_read_from()) {
249 /* The next node will read from a different value. */
250 tid = next->get_tid();
251 node_stack->pop_restofstack(2);
252 } else if (nextnode->increment_future_value()) {
253 /* The next node will try to read from a different future value. */
254 tid = next->get_tid();
255 node_stack->pop_restofstack(2);
256 } else if (nextnode->increment_relseq_break()) {
257 /* The next node will try to resolve a release sequence differently */
258 tid = next->get_tid();
259 node_stack->pop_restofstack(2);
262 /* Make a different thread execute for next step */
263 scheduler->add_sleep(get_thread(next->get_tid()));
264 tid = prevnode->get_next_backtrack();
265 /* Make sure the backtracked thread isn't sleeping. */
266 node_stack->pop_restofstack(1);
267 if (diverge == earliest_diverge) {
268 earliest_diverge = prevnode->get_action();
271 /* The correct sleep set is in the parent node. */
274 DEBUG("*** Divergence point ***\n");
278 tid = next->get_tid();
280 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
281 ASSERT(tid != THREAD_ID_T_NONE);
282 return thread_map->get(id_to_int(tid));
286 * We need to know what the next actions of all threads in the sleep
287 * set will be. This method computes them and stores the actions at
288 * the corresponding thread object's pending action.
291 void ModelChecker::execute_sleep_set()
293 for (unsigned int i = 0; i < get_num_threads(); i++) {
294 thread_id_t tid = int_to_id(i);
295 Thread *thr = get_thread(tid);
296 if (scheduler->is_sleep_set(thr) && thr->get_pending() == NULL) {
297 thr->set_state(THREAD_RUNNING);
298 scheduler->next_thread(thr);
299 Thread::swap(&system_context, thr);
300 priv->current_action->set_sleep_flag();
301 thr->set_pending(priv->current_action);
306 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
308 for (unsigned int i = 0; i < get_num_threads(); i++) {
309 Thread *thr = get_thread(int_to_id(i));
310 if (scheduler->is_sleep_set(thr)) {
311 ModelAction *pending_act = thr->get_pending();
312 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
313 //Remove this thread from sleep set
314 scheduler->remove_sleep(thr);
319 /** @brief Alert the model-checker that an incorrectly-ordered
320 * synchronization was made */
321 void ModelChecker::set_bad_synchronization()
323 priv->bad_synchronization = true;
326 bool ModelChecker::has_asserted() const
328 return priv->asserted;
331 void ModelChecker::set_assert()
333 priv->asserted = true;
337 * Check if we are in a deadlock. Should only be called at the end of an
338 * execution, although it should not give false positives in the middle of an
339 * execution (there should be some ENABLED thread).
341 * @return True if program is in a deadlock; false otherwise
343 bool ModelChecker::is_deadlocked() const
345 bool blocking_threads = false;
346 for (unsigned int i = 0; i < get_num_threads(); i++) {
347 thread_id_t tid = int_to_id(i);
350 Thread *t = get_thread(tid);
351 if (!t->is_model_thread() && t->get_pending())
352 blocking_threads = true;
354 return blocking_threads;
358 * Check if this is a complete execution. That is, have all thread completed
359 * execution (rather than exiting because sleep sets have forced a redundant
362 * @return True if the execution is complete.
364 bool ModelChecker::is_complete_execution() const
366 for (unsigned int i = 0; i < get_num_threads(); i++)
367 if (is_enabled(int_to_id(i)))
373 * @brief Assert a bug in the executing program.
375 * Use this function to assert any sort of bug in the user program. If the
376 * current trace is feasible (actually, a prefix of some feasible execution),
377 * then this execution will be aborted, printing the appropriate message. If
378 * the current trace is not yet feasible, the error message will be stashed and
379 * printed if the execution ever becomes feasible.
381 * @param msg Descriptive message for the bug (do not include newline char)
382 * @return True if bug is immediately-feasible
384 bool ModelChecker::assert_bug(const char *msg)
386 priv->bugs.push_back(new bug_message(msg));
388 if (isfeasibleprefix()) {
396 * @brief Assert a bug in the executing program, asserted by a user thread
397 * @see ModelChecker::assert_bug
398 * @param msg Descriptive message for the bug (do not include newline char)
400 void ModelChecker::assert_user_bug(const char *msg)
402 /* If feasible bug, bail out now */
404 switch_to_master(NULL);
407 /** @return True, if any bugs have been reported for this execution */
408 bool ModelChecker::have_bug_reports() const
410 return priv->bugs.size() != 0;
413 /** @brief Print bug report listing for this execution (if any bugs exist) */
414 void ModelChecker::print_bugs() const
416 if (have_bug_reports()) {
417 model_print("Bug report: %zu bug%s detected\n",
419 priv->bugs.size() > 1 ? "s" : "");
420 for (unsigned int i = 0; i < priv->bugs.size(); i++)
421 priv->bugs[i]->print();
426 * @brief Record end-of-execution stats
428 * Must be run when exiting an execution. Records various stats.
429 * @see struct execution_stats
431 void ModelChecker::record_stats()
434 if (!isfeasibleprefix())
435 stats.num_infeasible++;
436 else if (have_bug_reports())
437 stats.num_buggy_executions++;
438 else if (is_complete_execution())
439 stats.num_complete++;
441 stats.num_redundant++;
444 /** @brief Print execution stats */
445 void ModelChecker::print_stats() const
447 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
448 model_print("Number of redundant executions: %d\n", stats.num_redundant);
449 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
450 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
451 model_print("Total executions: %d\n", stats.num_total);
452 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
456 * @brief End-of-exeuction print
457 * @param printbugs Should any existing bugs be printed?
459 void ModelChecker::print_execution(bool printbugs) const
461 print_program_output();
463 if (DBG_ENABLED() || params.verbose) {
464 model_print("Earliest divergence point since last feasible execution:\n");
465 if (earliest_diverge)
466 earliest_diverge->print();
468 model_print("(Not set)\n");
474 /* Don't print invalid bugs */
483 * Queries the model-checker for more executions to explore and, if one
484 * exists, resets the model-checker state to execute a new execution.
486 * @return If there are more executions to explore, return true. Otherwise,
489 bool ModelChecker::next_execution()
492 /* Is this execution a feasible execution that's worth bug-checking? */
493 bool complete = isfeasibleprefix() && (is_complete_execution() ||
496 /* End-of-execution bug checks */
499 assert_bug("Deadlock detected");
507 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
508 print_execution(complete);
510 clear_program_output();
513 earliest_diverge = NULL;
515 if ((diverge = get_next_backtrack()) == NULL)
519 model_print("Next execution will diverge at:\n");
523 reset_to_initial_state();
527 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
529 switch (act->get_type()) {
534 /* Optimization: relaxed operations don't need backtracking */
535 if (act->is_relaxed())
537 /* linear search: from most recent to oldest */
538 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
539 action_list_t::reverse_iterator rit;
540 for (rit = list->rbegin(); rit != list->rend(); rit++) {
541 ModelAction *prev = *rit;
542 if (prev->could_synchronize_with(act))
548 case ATOMIC_TRYLOCK: {
549 /* linear search: from most recent to oldest */
550 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
551 action_list_t::reverse_iterator rit;
552 for (rit = list->rbegin(); rit != list->rend(); rit++) {
553 ModelAction *prev = *rit;
554 if (act->is_conflicting_lock(prev))
559 case ATOMIC_UNLOCK: {
560 /* linear search: from most recent to oldest */
561 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
562 action_list_t::reverse_iterator rit;
563 for (rit = list->rbegin(); rit != list->rend(); rit++) {
564 ModelAction *prev = *rit;
565 if (!act->same_thread(prev) && prev->is_failed_trylock())
571 /* linear search: from most recent to oldest */
572 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
573 action_list_t::reverse_iterator rit;
574 for (rit = list->rbegin(); rit != list->rend(); rit++) {
575 ModelAction *prev = *rit;
576 if (!act->same_thread(prev) && prev->is_failed_trylock())
578 if (!act->same_thread(prev) && prev->is_notify())
584 case ATOMIC_NOTIFY_ALL:
585 case ATOMIC_NOTIFY_ONE: {
586 /* linear search: from most recent to oldest */
587 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
588 action_list_t::reverse_iterator rit;
589 for (rit = list->rbegin(); rit != list->rend(); rit++) {
590 ModelAction *prev = *rit;
591 if (!act->same_thread(prev) && prev->is_wait())
602 /** This method finds backtracking points where we should try to
603 * reorder the parameter ModelAction against.
605 * @param the ModelAction to find backtracking points for.
607 void ModelChecker::set_backtracking(ModelAction *act)
609 Thread *t = get_thread(act);
610 ModelAction *prev = get_last_conflict(act);
614 Node *node = prev->get_node()->get_parent();
616 int low_tid, high_tid;
617 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
618 low_tid = id_to_int(act->get_tid());
619 high_tid = low_tid + 1;
622 high_tid = get_num_threads();
625 for (int i = low_tid; i < high_tid; i++) {
626 thread_id_t tid = int_to_id(i);
628 /* Make sure this thread can be enabled here. */
629 if (i >= node->get_num_threads())
632 /* Don't backtrack into a point where the thread is disabled or sleeping. */
633 if (node->enabled_status(tid) != THREAD_ENABLED)
636 /* Check if this has been explored already */
637 if (node->has_been_explored(tid))
640 /* See if fairness allows */
641 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
643 for (int t = 0; t < node->get_num_threads(); t++) {
644 thread_id_t tother = int_to_id(t);
645 if (node->is_enabled(tother) && node->has_priority(tother)) {
653 /* Cache the latest backtracking point */
654 set_latest_backtrack(prev);
656 /* If this is a new backtracking point, mark the tree */
657 if (!node->set_backtrack(tid))
659 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
660 id_to_int(prev->get_tid()),
661 id_to_int(t->get_id()));
670 * @brief Cache the a backtracking point as the "most recent", if eligible
672 * Note that this does not prepare the NodeStack for this backtracking
673 * operation, it only caches the action on a per-execution basis
675 * @param act The operation at which we should explore a different next action
676 * (i.e., backtracking point)
677 * @return True, if this action is now the most recent backtracking point;
680 bool ModelChecker::set_latest_backtrack(ModelAction *act)
682 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
683 priv->next_backtrack = act;
690 * Returns last backtracking point. The model checker will explore a different
691 * path for this point in the next execution.
692 * @return The ModelAction at which the next execution should diverge.
694 ModelAction * ModelChecker::get_next_backtrack()
696 ModelAction *next = priv->next_backtrack;
697 priv->next_backtrack = NULL;
702 * Processes a read or rmw model action.
703 * @param curr is the read model action to process.
704 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
705 * @return True if processing this read updates the mo_graph.
707 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
709 uint64_t value = VALUE_NONE;
710 bool updated = false;
712 const ModelAction *reads_from = curr->get_node()->get_read_from();
713 if (reads_from != NULL) {
714 mo_graph->startChanges();
716 value = reads_from->get_value();
717 bool r_status = false;
719 if (!second_part_of_rmw) {
720 check_recency(curr, reads_from);
721 r_status = r_modification_order(curr, reads_from);
725 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
726 mo_graph->rollbackChanges();
727 priv->too_many_reads = false;
731 read_from(curr, reads_from);
732 mo_graph->commitChanges();
733 mo_check_promises(curr->get_tid(), reads_from, NULL);
736 } else if (!second_part_of_rmw) {
737 /* Read from future value */
738 struct future_value fv = curr->get_node()->get_future_value();
740 curr->set_read_from(NULL);
741 promises->push_back(new Promise(curr, fv));
743 get_thread(curr)->set_return_value(value);
749 * Processes a lock, trylock, or unlock model action. @param curr is
750 * the read model action to process.
752 * The try lock operation checks whether the lock is taken. If not,
753 * it falls to the normal lock operation case. If so, it returns
756 * The lock operation has already been checked that it is enabled, so
757 * it just grabs the lock and synchronizes with the previous unlock.
759 * The unlock operation has to re-enable all of the threads that are
760 * waiting on the lock.
762 * @return True if synchronization was updated; false otherwise
764 bool ModelChecker::process_mutex(ModelAction *curr)
766 std::mutex *mutex = NULL;
767 struct std::mutex_state *state = NULL;
769 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
770 mutex = (std::mutex *)curr->get_location();
771 state = mutex->get_state();
772 } else if (curr->is_wait()) {
773 mutex = (std::mutex *)curr->get_value();
774 state = mutex->get_state();
777 switch (curr->get_type()) {
778 case ATOMIC_TRYLOCK: {
779 bool success = !state->islocked;
780 curr->set_try_lock(success);
782 get_thread(curr)->set_return_value(0);
785 get_thread(curr)->set_return_value(1);
787 //otherwise fall into the lock case
789 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
790 assert_bug("Lock access before initialization");
791 state->islocked = true;
792 ModelAction *unlock = get_last_unlock(curr);
793 //synchronize with the previous unlock statement
794 if (unlock != NULL) {
795 curr->synchronize_with(unlock);
800 case ATOMIC_UNLOCK: {
802 state->islocked = false;
803 //wake up the other threads
804 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
805 //activate all the waiting threads
806 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
807 scheduler->wake(get_thread(*rit));
814 state->islocked = false;
815 //wake up the other threads
816 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
817 //activate all the waiting threads
818 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
819 scheduler->wake(get_thread(*rit));
822 //check whether we should go to sleep or not...simulate spurious failures
823 if (curr->get_node()->get_misc() == 0) {
824 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
826 scheduler->sleep(get_thread(curr));
830 case ATOMIC_NOTIFY_ALL: {
831 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
832 //activate all the waiting threads
833 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
834 scheduler->wake(get_thread(*rit));
839 case ATOMIC_NOTIFY_ONE: {
840 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
841 int wakeupthread = curr->get_node()->get_misc();
842 action_list_t::iterator it = waiters->begin();
843 advance(it, wakeupthread);
844 scheduler->wake(get_thread(*it));
855 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
857 /* Do more ambitious checks now that mo is more complete */
858 if (mo_may_allow(writer, reader)) {
859 struct future_value fv = {
861 writer->get_seq_number() + params.maxfuturedelay,
863 if (reader->get_node()->add_future_value(fv))
864 set_latest_backtrack(reader);
869 * Process a write ModelAction
870 * @param curr The ModelAction to process
871 * @return True if the mo_graph was updated or promises were resolved
873 bool ModelChecker::process_write(ModelAction *curr)
875 bool updated_mod_order = w_modification_order(curr);
876 bool updated_promises = resolve_promises(curr);
878 if (promises->size() == 0) {
879 for (unsigned int i = 0; i < futurevalues->size(); i++) {
880 struct PendingFutureValue pfv = (*futurevalues)[i];
881 add_future_value(pfv.writer, pfv.act);
883 futurevalues->clear();
886 mo_graph->commitChanges();
887 mo_check_promises(curr->get_tid(), curr, NULL);
889 get_thread(curr)->set_return_value(VALUE_NONE);
890 return updated_mod_order || updated_promises;
894 * Process a fence ModelAction
895 * @param curr The ModelAction to process
896 * @return True if synchronization was updated
898 bool ModelChecker::process_fence(ModelAction *curr)
901 * fence-relaxed: no-op
902 * fence-release: only log the occurence (not in this function), for
903 * use in later synchronization
904 * fence-acquire (this function): search for hypothetical release
907 bool updated = false;
908 if (curr->is_acquire()) {
909 action_list_t *list = action_trace;
910 action_list_t::reverse_iterator rit;
911 /* Find X : is_read(X) && X --sb-> curr */
912 for (rit = list->rbegin(); rit != list->rend(); rit++) {
913 ModelAction *act = *rit;
916 if (act->get_tid() != curr->get_tid())
918 /* Stop at the beginning of the thread */
919 if (act->is_thread_start())
921 /* Stop once we reach a prior fence-acquire */
922 if (act->is_fence() && act->is_acquire())
926 /* read-acquire will find its own release sequences */
927 if (act->is_acquire())
930 /* Establish hypothetical release sequences */
931 rel_heads_list_t release_heads;
932 get_release_seq_heads(curr, act, &release_heads);
933 for (unsigned int i = 0; i < release_heads.size(); i++)
934 if (!curr->synchronize_with(release_heads[i]))
935 set_bad_synchronization();
936 if (release_heads.size() != 0)
944 * @brief Process the current action for thread-related activity
946 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
947 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
948 * synchronization, etc. This function is a no-op for non-THREAD actions
949 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
951 * @param curr The current action
952 * @return True if synchronization was updated or a thread completed
954 bool ModelChecker::process_thread_action(ModelAction *curr)
956 bool updated = false;
958 switch (curr->get_type()) {
959 case THREAD_CREATE: {
960 Thread *th = curr->get_thread_operand();
961 th->set_creation(curr);
965 Thread *blocking = curr->get_thread_operand();
966 ModelAction *act = get_last_action(blocking->get_id());
967 curr->synchronize_with(act);
968 updated = true; /* trigger rel-seq checks */
971 case THREAD_FINISH: {
972 Thread *th = get_thread(curr);
973 while (!th->wait_list_empty()) {
974 ModelAction *act = th->pop_wait_list();
975 scheduler->wake(get_thread(act));
978 updated = true; /* trigger rel-seq checks */
982 check_promises(curr->get_tid(), NULL, curr->get_cv());
993 * @brief Process the current action for release sequence fixup activity
995 * Performs model-checker release sequence fixups for the current action,
996 * forcing a single pending release sequence to break (with a given, potential
997 * "loose" write) or to complete (i.e., synchronize). If a pending release
998 * sequence forms a complete release sequence, then we must perform the fixup
999 * synchronization, mo_graph additions, etc.
1001 * @param curr The current action; must be a release sequence fixup action
1002 * @param work_queue The work queue to which to add work items as they are
1005 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1007 const ModelAction *write = curr->get_node()->get_relseq_break();
1008 struct release_seq *sequence = pending_rel_seqs->back();
1009 pending_rel_seqs->pop_back();
1011 ModelAction *acquire = sequence->acquire;
1012 const ModelAction *rf = sequence->rf;
1013 const ModelAction *release = sequence->release;
1017 ASSERT(release->same_thread(rf));
1019 if (write == NULL) {
1021 * @todo Forcing a synchronization requires that we set
1022 * modification order constraints. For instance, we can't allow
1023 * a fixup sequence in which two separate read-acquire
1024 * operations read from the same sequence, where the first one
1025 * synchronizes and the other doesn't. Essentially, we can't
1026 * allow any writes to insert themselves between 'release' and
1030 /* Must synchronize */
1031 if (!acquire->synchronize_with(release)) {
1032 set_bad_synchronization();
1035 /* Re-check all pending release sequences */
1036 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1037 /* Re-check act for mo_graph edges */
1038 work_queue->push_back(MOEdgeWorkEntry(acquire));
1040 /* propagate synchronization to later actions */
1041 action_list_t::reverse_iterator rit = action_trace->rbegin();
1042 for (; (*rit) != acquire; rit++) {
1043 ModelAction *propagate = *rit;
1044 if (acquire->happens_before(propagate)) {
1045 propagate->synchronize_with(acquire);
1046 /* Re-check 'propagate' for mo_graph edges */
1047 work_queue->push_back(MOEdgeWorkEntry(propagate));
1051 /* Break release sequence with new edges:
1052 * release --mo--> write --mo--> rf */
1053 mo_graph->addEdge(release, write);
1054 mo_graph->addEdge(write, rf);
1057 /* See if we have realized a data race */
1062 * Initialize the current action by performing one or more of the following
1063 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1064 * in the NodeStack, manipulating backtracking sets, allocating and
1065 * initializing clock vectors, and computing the promises to fulfill.
1067 * @param curr The current action, as passed from the user context; may be
1068 * freed/invalidated after the execution of this function, with a different
1069 * action "returned" its place (pass-by-reference)
1070 * @return True if curr is a newly-explored action; false otherwise
1072 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1074 ModelAction *newcurr;
1076 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1077 newcurr = process_rmw(*curr);
1080 if (newcurr->is_rmw())
1081 compute_promises(newcurr);
1087 (*curr)->set_seq_number(get_next_seq_num());
1089 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1091 /* First restore type and order in case of RMW operation */
1092 if ((*curr)->is_rmwr())
1093 newcurr->copy_typeandorder(*curr);
1095 ASSERT((*curr)->get_location() == newcurr->get_location());
1096 newcurr->copy_from_new(*curr);
1098 /* Discard duplicate ModelAction; use action from NodeStack */
1101 /* Always compute new clock vector */
1102 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1105 return false; /* Action was explored previously */
1109 /* Always compute new clock vector */
1110 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1112 /* Assign most recent release fence */
1113 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1116 * Perform one-time actions when pushing new ModelAction onto
1119 if (newcurr->is_write())
1120 compute_promises(newcurr);
1121 else if (newcurr->is_relseq_fixup())
1122 compute_relseq_breakwrites(newcurr);
1123 else if (newcurr->is_wait())
1124 newcurr->get_node()->set_misc_max(2);
1125 else if (newcurr->is_notify_one()) {
1126 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1128 return true; /* This was a new ModelAction */
1133 * @brief Establish reads-from relation between two actions
1135 * Perform basic operations involved with establishing a concrete rf relation,
1136 * including setting the ModelAction data and checking for release sequences.
1138 * @param act The action that is reading (must be a read)
1139 * @param rf The action from which we are reading (must be a write)
1141 * @return True if this read established synchronization
1143 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1145 act->set_read_from(rf);
1146 if (rf != NULL && act->is_acquire()) {
1147 rel_heads_list_t release_heads;
1148 get_release_seq_heads(act, act, &release_heads);
1149 int num_heads = release_heads.size();
1150 for (unsigned int i = 0; i < release_heads.size(); i++)
1151 if (!act->synchronize_with(release_heads[i])) {
1152 set_bad_synchronization();
1155 return num_heads > 0;
1161 * @brief Check whether a model action is enabled.
1163 * Checks whether a lock or join operation would be successful (i.e., is the
1164 * lock already locked, or is the joined thread already complete). If not, put
1165 * the action in a waiter list.
1167 * @param curr is the ModelAction to check whether it is enabled.
1168 * @return a bool that indicates whether the action is enabled.
1170 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1171 if (curr->is_lock()) {
1172 std::mutex *lock = (std::mutex *)curr->get_location();
1173 struct std::mutex_state *state = lock->get_state();
1174 if (state->islocked) {
1175 //Stick the action in the appropriate waiting queue
1176 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1179 } else if (curr->get_type() == THREAD_JOIN) {
1180 Thread *blocking = (Thread *)curr->get_location();
1181 if (!blocking->is_complete()) {
1182 blocking->push_wait_list(curr);
1191 * Stores the ModelAction for the current thread action. Call this
1192 * immediately before switching from user- to system-context to pass
1193 * data between them.
1194 * @param act The ModelAction created by the user-thread action
1196 void ModelChecker::set_current_action(ModelAction *act) {
1197 priv->current_action = act;
1201 * This is the heart of the model checker routine. It performs model-checking
1202 * actions corresponding to a given "current action." Among other processes, it
1203 * calculates reads-from relationships, updates synchronization clock vectors,
1204 * forms a memory_order constraints graph, and handles replay/backtrack
1205 * execution when running permutations of previously-observed executions.
1207 * @param curr The current action to process
1208 * @return The ModelAction that is actually executed; may be different than
1209 * curr; may be NULL, if the current action is not enabled to run
1211 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1214 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1216 if (!check_action_enabled(curr)) {
1217 /* Make the execution look like we chose to run this action
1218 * much later, when a lock/join can succeed */
1219 get_thread(curr)->set_pending(curr);
1220 scheduler->sleep(get_thread(curr));
1224 bool newly_explored = initialize_curr_action(&curr);
1230 wake_up_sleeping_actions(curr);
1232 /* Add the action to lists before any other model-checking tasks */
1233 if (!second_part_of_rmw)
1234 add_action_to_lists(curr);
1236 /* Build may_read_from set for newly-created actions */
1237 if (newly_explored && curr->is_read())
1238 build_reads_from_past(curr);
1240 /* Initialize work_queue with the "current action" work */
1241 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1242 while (!work_queue.empty() && !has_asserted()) {
1243 WorkQueueEntry work = work_queue.front();
1244 work_queue.pop_front();
1246 switch (work.type) {
1247 case WORK_CHECK_CURR_ACTION: {
1248 ModelAction *act = work.action;
1249 bool update = false; /* update this location's release seq's */
1250 bool update_all = false; /* update all release seq's */
1252 if (process_thread_action(curr))
1255 if (act->is_read() && process_read(act, second_part_of_rmw))
1258 if (act->is_write() && process_write(act))
1261 if (act->is_fence() && process_fence(act))
1264 if (act->is_mutex_op() && process_mutex(act))
1267 if (act->is_relseq_fixup())
1268 process_relseq_fixup(curr, &work_queue);
1271 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1273 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1276 case WORK_CHECK_RELEASE_SEQ:
1277 resolve_release_sequences(work.location, &work_queue);
1279 case WORK_CHECK_MO_EDGES: {
1280 /** @todo Complete verification of work_queue */
1281 ModelAction *act = work.action;
1282 bool updated = false;
1284 if (act->is_read()) {
1285 const ModelAction *rf = act->get_reads_from();
1286 if (rf != NULL && r_modification_order(act, rf))
1289 if (act->is_write()) {
1290 if (w_modification_order(act))
1293 mo_graph->commitChanges();
1296 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1305 check_curr_backtracking(curr);
1306 set_backtracking(curr);
1310 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1312 Node *currnode = curr->get_node();
1313 Node *parnode = currnode->get_parent();
1315 if ((parnode && !parnode->backtrack_empty()) ||
1316 !currnode->misc_empty() ||
1317 !currnode->read_from_empty() ||
1318 !currnode->future_value_empty() ||
1319 !currnode->promise_empty() ||
1320 !currnode->relseq_break_empty()) {
1321 set_latest_backtrack(curr);
1325 bool ModelChecker::promises_expired() const
1327 for (unsigned int i = 0; i < promises->size(); i++) {
1328 Promise *promise = (*promises)[i];
1329 if (promise->get_expiration() < priv->used_sequence_numbers)
1336 * This is the strongest feasibility check available.
1337 * @return whether the current trace (partial or complete) must be a prefix of
1340 bool ModelChecker::isfeasibleprefix() const
1342 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1346 * Print disagnostic information about an infeasible execution
1347 * @param prefix A string to prefix the output with; if NULL, then a default
1348 * message prefix will be provided
1350 void ModelChecker::print_infeasibility(const char *prefix) const
1354 if (mo_graph->checkForRMWViolation())
1355 ptr += sprintf(ptr, "[RMW atomicity]");
1356 if (mo_graph->checkForCycles())
1357 ptr += sprintf(ptr, "[mo cycle]");
1358 if (priv->failed_promise)
1359 ptr += sprintf(ptr, "[failed promise]");
1360 if (priv->too_many_reads)
1361 ptr += sprintf(ptr, "[too many reads]");
1362 if (priv->bad_synchronization)
1363 ptr += sprintf(ptr, "[bad sw ordering]");
1364 if (promises_expired())
1365 ptr += sprintf(ptr, "[promise expired]");
1366 if (promises->size() != 0)
1367 ptr += sprintf(ptr, "[unresolved promise]");
1369 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1373 * Returns whether the current completed trace is feasible, except for pending
1374 * release sequences.
1376 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1378 return !is_infeasible() && promises->size() == 0;
1382 * Check if the current partial trace is infeasible. Does not check any
1383 * end-of-execution flags, which might rule out the execution. Thus, this is
1384 * useful only for ruling an execution as infeasible.
1385 * @return whether the current partial trace is infeasible.
1387 bool ModelChecker::is_infeasible() const
1389 return mo_graph->checkForRMWViolation() || is_infeasible_ignoreRMW();
1393 * Check If the current partial trace is infeasible, while ignoring
1394 * infeasibility related to 2 RMW's reading from the same store. It does not
1395 * check end-of-execution feasibility.
1396 * @see ModelChecker::is_infeasible
1397 * @return whether the current partial trace is infeasible, ignoring multiple
1398 * RMWs reading from the same store.
1400 bool ModelChecker::is_infeasible_ignoreRMW() const
1402 return mo_graph->checkForCycles() || priv->failed_promise ||
1403 priv->too_many_reads || priv->bad_synchronization ||
1407 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1408 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1409 ModelAction *lastread = get_last_action(act->get_tid());
1410 lastread->process_rmw(act);
1411 if (act->is_rmw() && lastread->get_reads_from() != NULL) {
1412 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1413 mo_graph->commitChanges();
1419 * Checks whether a thread has read from the same write for too many times
1420 * without seeing the effects of a later write.
1423 * 1) there must a different write that we could read from that would satisfy the modification order,
1424 * 2) we must have read from the same value in excess of maxreads times, and
1425 * 3) that other write must have been in the reads_from set for maxreads times.
1427 * If so, we decide that the execution is no longer feasible.
1429 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1431 if (params.maxreads != 0) {
1432 if (curr->get_node()->get_read_from_size() <= 1)
1434 //Must make sure that execution is currently feasible... We could
1435 //accidentally clear by rolling back
1436 if (is_infeasible())
1438 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1439 int tid = id_to_int(curr->get_tid());
1442 if ((int)thrd_lists->size() <= tid)
1444 action_list_t *list = &(*thrd_lists)[tid];
1446 action_list_t::reverse_iterator rit = list->rbegin();
1447 /* Skip past curr */
1448 for (; (*rit) != curr; rit++)
1450 /* go past curr now */
1453 action_list_t::reverse_iterator ritcopy = rit;
1454 //See if we have enough reads from the same value
1456 for (; count < params.maxreads; rit++, count++) {
1457 if (rit == list->rend())
1459 ModelAction *act = *rit;
1460 if (!act->is_read())
1463 if (act->get_reads_from() != rf)
1465 if (act->get_node()->get_read_from_size() <= 1)
1468 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1470 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1472 /* Need a different write */
1476 /* Test to see whether this is a feasible write to read from */
1477 mo_graph->startChanges();
1478 r_modification_order(curr, write);
1479 bool feasiblereadfrom = !is_infeasible();
1480 mo_graph->rollbackChanges();
1482 if (!feasiblereadfrom)
1486 bool feasiblewrite = true;
1487 //new we need to see if this write works for everyone
1489 for (int loop = count; loop > 0; loop--, rit++) {
1490 ModelAction *act = *rit;
1491 bool foundvalue = false;
1492 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1493 if (act->get_node()->get_read_from_at(j) == write) {
1499 feasiblewrite = false;
1503 if (feasiblewrite) {
1504 priv->too_many_reads = true;
1512 * Updates the mo_graph with the constraints imposed from the current
1515 * Basic idea is the following: Go through each other thread and find
1516 * the lastest action that happened before our read. Two cases:
1518 * (1) The action is a write => that write must either occur before
1519 * the write we read from or be the write we read from.
1521 * (2) The action is a read => the write that that action read from
1522 * must occur before the write we read from or be the same write.
1524 * @param curr The current action. Must be a read.
1525 * @param rf The action that curr reads from. Must be a write.
1526 * @return True if modification order edges were added; false otherwise
1528 bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
1530 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1533 ASSERT(curr->is_read());
1535 /* Last SC fence in the current thread */
1536 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1538 /* Iterate over all threads */
1539 for (i = 0; i < thrd_lists->size(); i++) {
1540 /* Last SC fence in thread i */
1541 ModelAction *last_sc_fence_thread_local = NULL;
1542 if (int_to_id((int)i) != curr->get_tid())
1543 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1545 /* Last SC fence in thread i, before last SC fence in current thread */
1546 ModelAction *last_sc_fence_thread_before = NULL;
1547 if (last_sc_fence_local)
1548 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1550 /* Iterate over actions in thread, starting from most recent */
1551 action_list_t *list = &(*thrd_lists)[i];
1552 action_list_t::reverse_iterator rit;
1553 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1554 ModelAction *act = *rit;
1556 if (act->is_write() && act != rf && act != curr) {
1557 /* C++, Section 29.3 statement 5 */
1558 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1559 *act < *last_sc_fence_thread_local) {
1560 mo_graph->addEdge(act, rf);
1564 /* C++, Section 29.3 statement 4 */
1565 else if (act->is_seqcst() && last_sc_fence_local &&
1566 *act < *last_sc_fence_local) {
1567 mo_graph->addEdge(act, rf);
1571 /* C++, Section 29.3 statement 6 */
1572 else if (last_sc_fence_thread_before &&
1573 *act < *last_sc_fence_thread_before) {
1574 mo_graph->addEdge(act, rf);
1581 * Include at most one act per-thread that "happens
1582 * before" curr. Don't consider reflexively.
1584 if (act->happens_before(curr) && act != curr) {
1585 if (act->is_write()) {
1587 mo_graph->addEdge(act, rf);
1591 const ModelAction *prevreadfrom = act->get_reads_from();
1592 //if the previous read is unresolved, keep going...
1593 if (prevreadfrom == NULL)
1596 if (rf != prevreadfrom) {
1597 mo_graph->addEdge(prevreadfrom, rf);
1609 /** This method fixes up the modification order when we resolve a
1610 * promises. The basic problem is that actions that occur after the
1611 * read curr could not property add items to the modification order
1614 * So for each thread, we find the earliest item that happens after
1615 * the read curr. This is the item we have to fix up with additional
1616 * constraints. If that action is write, we add a MO edge between
1617 * the Action rf and that action. If the action is a read, we add a
1618 * MO edge between the Action rf, and whatever the read accessed.
1620 * @param curr is the read ModelAction that we are fixing up MO edges for.
1621 * @param rf is the write ModelAction that curr reads from.
1624 void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
1626 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1628 ASSERT(curr->is_read());
1630 /* Iterate over all threads */
1631 for (i = 0; i < thrd_lists->size(); i++) {
1632 /* Iterate over actions in thread, starting from most recent */
1633 action_list_t *list = &(*thrd_lists)[i];
1634 action_list_t::reverse_iterator rit;
1635 ModelAction *lastact = NULL;
1637 /* Find last action that happens after curr that is either not curr or a rmw */
1638 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1639 ModelAction *act = *rit;
1640 if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
1646 /* Include at most one act per-thread that "happens before" curr */
1647 if (lastact != NULL) {
1648 if (lastact == curr) {
1649 //Case 1: The resolved read is a RMW, and we need to make sure
1650 //that the write portion of the RMW mod order after rf
1652 mo_graph->addEdge(rf, lastact);
1653 } else if (lastact->is_read()) {
1654 //Case 2: The resolved read is a normal read and the next
1655 //operation is a read, and we need to make sure the value read
1656 //is mod ordered after rf
1658 const ModelAction *postreadfrom = lastact->get_reads_from();
1659 if (postreadfrom != NULL && rf != postreadfrom)
1660 mo_graph->addEdge(rf, postreadfrom);
1662 //Case 3: The resolved read is a normal read and the next
1663 //operation is a write, and we need to make sure that the
1664 //write is mod ordered after rf
1666 mo_graph->addEdge(rf, lastact);
1674 * Updates the mo_graph with the constraints imposed from the current write.
1676 * Basic idea is the following: Go through each other thread and find
1677 * the lastest action that happened before our write. Two cases:
1679 * (1) The action is a write => that write must occur before
1682 * (2) The action is a read => the write that that action read from
1683 * must occur before the current write.
1685 * This method also handles two other issues:
1687 * (I) Sequential Consistency: Making sure that if the current write is
1688 * seq_cst, that it occurs after the previous seq_cst write.
1690 * (II) Sending the write back to non-synchronizing reads.
1692 * @param curr The current action. Must be a write.
1693 * @return True if modification order edges were added; false otherwise
1695 bool ModelChecker::w_modification_order(ModelAction *curr)
1697 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1700 ASSERT(curr->is_write());
1702 if (curr->is_seqcst()) {
1703 /* We have to at least see the last sequentially consistent write,
1704 so we are initialized. */
1705 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1706 if (last_seq_cst != NULL) {
1707 mo_graph->addEdge(last_seq_cst, curr);
1712 /* Last SC fence in the current thread */
1713 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1715 /* Iterate over all threads */
1716 for (i = 0; i < thrd_lists->size(); i++) {
1717 /* Last SC fence in thread i, before last SC fence in current thread */
1718 ModelAction *last_sc_fence_thread_before = NULL;
1719 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1720 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1722 /* Iterate over actions in thread, starting from most recent */
1723 action_list_t *list = &(*thrd_lists)[i];
1724 action_list_t::reverse_iterator rit;
1725 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1726 ModelAction *act = *rit;
1729 * 1) If RMW and it actually read from something, then we
1730 * already have all relevant edges, so just skip to next
1733 * 2) If RMW and it didn't read from anything, we should
1734 * whatever edge we can get to speed up convergence.
1736 * 3) If normal write, we need to look at earlier actions, so
1737 * continue processing list.
1739 if (curr->is_rmw()) {
1740 if (curr->get_reads_from() != NULL)
1748 /* C++, Section 29.3 statement 7 */
1749 if (last_sc_fence_thread_before && act->is_write() &&
1750 *act < *last_sc_fence_thread_before) {
1751 mo_graph->addEdge(act, curr);
1757 * Include at most one act per-thread that "happens
1760 if (act->happens_before(curr)) {
1762 * Note: if act is RMW, just add edge:
1764 * The following edge should be handled elsewhere:
1765 * readfrom(act) --mo--> act
1767 if (act->is_write())
1768 mo_graph->addEdge(act, curr);
1769 else if (act->is_read()) {
1770 //if previous read accessed a null, just keep going
1771 if (act->get_reads_from() == NULL)
1773 mo_graph->addEdge(act->get_reads_from(), curr);
1777 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1778 !act->same_thread(curr)) {
1779 /* We have an action that:
1780 (1) did not happen before us
1781 (2) is a read and we are a write
1782 (3) cannot synchronize with us
1783 (4) is in a different thread
1785 that read could potentially read from our write. Note that
1786 these checks are overly conservative at this point, we'll
1787 do more checks before actually removing the
1791 if (thin_air_constraint_may_allow(curr, act)) {
1792 if (!is_infeasible() ||
1793 (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && !is_infeasible_ignoreRMW())) {
1794 futurevalues->push_back(PendingFutureValue(curr, act));
1804 /** Arbitrary reads from the future are not allowed. Section 29.3
1805 * part 9 places some constraints. This method checks one result of constraint
1806 * constraint. Others require compiler support. */
1807 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1809 if (!writer->is_rmw())
1812 if (!reader->is_rmw())
1815 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1816 if (search == reader)
1818 if (search->get_tid() == reader->get_tid() &&
1819 search->happens_before(reader))
1827 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1828 * some constraints. This method checks one the following constraint (others
1829 * require compiler support):
1831 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1833 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1835 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1837 /* Iterate over all threads */
1838 for (i = 0; i < thrd_lists->size(); i++) {
1839 const ModelAction *write_after_read = NULL;
1841 /* Iterate over actions in thread, starting from most recent */
1842 action_list_t *list = &(*thrd_lists)[i];
1843 action_list_t::reverse_iterator rit;
1844 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1845 ModelAction *act = *rit;
1847 /* Don't disallow due to act == reader */
1848 if (!reader->happens_before(act) || reader == act)
1850 else if (act->is_write())
1851 write_after_read = act;
1852 else if (act->is_read() && act->get_reads_from() != NULL)
1853 write_after_read = act->get_reads_from();
1856 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1863 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1864 * The ModelAction under consideration is expected to be taking part in
1865 * release/acquire synchronization as an object of the "reads from" relation.
1866 * Note that this can only provide release sequence support for RMW chains
1867 * which do not read from the future, as those actions cannot be traced until
1868 * their "promise" is fulfilled. Similarly, we may not even establish the
1869 * presence of a release sequence with certainty, as some modification order
1870 * constraints may be decided further in the future. Thus, this function
1871 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1872 * and a boolean representing certainty.
1874 * @param rf The action that might be part of a release sequence. Must be a
1876 * @param release_heads A pass-by-reference style return parameter. After
1877 * execution of this function, release_heads will contain the heads of all the
1878 * relevant release sequences, if any exists with certainty
1879 * @param pending A pass-by-reference style return parameter which is only used
1880 * when returning false (i.e., uncertain). Returns most information regarding
1881 * an uncertain release sequence, including any write operations that might
1882 * break the sequence.
1883 * @return true, if the ModelChecker is certain that release_heads is complete;
1886 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1887 rel_heads_list_t *release_heads,
1888 struct release_seq *pending) const
1890 /* Only check for release sequences if there are no cycles */
1891 if (mo_graph->checkForCycles())
1895 ASSERT(rf->is_write());
1897 if (rf->is_release())
1898 release_heads->push_back(rf);
1899 else if (rf->get_last_fence_release())
1900 release_heads->push_back(rf->get_last_fence_release());
1902 break; /* End of RMW chain */
1904 /** @todo Need to be smarter here... In the linux lock
1905 * example, this will run to the beginning of the program for
1907 /** @todo The way to be smarter here is to keep going until 1
1908 * thread has a release preceded by an acquire and you've seen
1911 /* acq_rel RMW is a sufficient stopping condition */
1912 if (rf->is_acquire() && rf->is_release())
1913 return true; /* complete */
1915 rf = rf->get_reads_from();
1918 /* read from future: need to settle this later */
1920 return false; /* incomplete */
1923 if (rf->is_release())
1924 return true; /* complete */
1926 /* else relaxed write
1927 * - check for fence-release in the same thread (29.8, stmt. 3)
1928 * - check modification order for contiguous subsequence
1929 * -> rf must be same thread as release */
1931 const ModelAction *fence_release = rf->get_last_fence_release();
1932 /* Synchronize with a fence-release unconditionally; we don't need to
1933 * find any more "contiguous subsequence..." for it */
1935 release_heads->push_back(fence_release);
1937 int tid = id_to_int(rf->get_tid());
1938 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1939 action_list_t *list = &(*thrd_lists)[tid];
1940 action_list_t::const_reverse_iterator rit;
1942 /* Find rf in the thread list */
1943 rit = std::find(list->rbegin(), list->rend(), rf);
1944 ASSERT(rit != list->rend());
1946 /* Find the last {write,fence}-release */
1947 for (; rit != list->rend(); rit++) {
1948 if (fence_release && *(*rit) < *fence_release)
1950 if ((*rit)->is_release())
1953 if (rit == list->rend()) {
1954 /* No write-release in this thread */
1955 return true; /* complete */
1956 } else if (fence_release && *(*rit) < *fence_release) {
1957 /* The fence-release is more recent (and so, "stronger") than
1958 * the most recent write-release */
1959 return true; /* complete */
1960 } /* else, need to establish contiguous release sequence */
1961 ModelAction *release = *rit;
1963 ASSERT(rf->same_thread(release));
1965 pending->writes.clear();
1967 bool certain = true;
1968 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
1969 if (id_to_int(rf->get_tid()) == (int)i)
1971 list = &(*thrd_lists)[i];
1973 /* Can we ensure no future writes from this thread may break
1974 * the release seq? */
1975 bool future_ordered = false;
1977 ModelAction *last = get_last_action(int_to_id(i));
1978 Thread *th = get_thread(int_to_id(i));
1979 if ((last && rf->happens_before(last)) ||
1982 future_ordered = true;
1984 ASSERT(!th->is_model_thread() || future_ordered);
1986 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1987 const ModelAction *act = *rit;
1988 /* Reach synchronization -> this thread is complete */
1989 if (act->happens_before(release))
1991 if (rf->happens_before(act)) {
1992 future_ordered = true;
1996 /* Only non-RMW writes can break release sequences */
1997 if (!act->is_write() || act->is_rmw())
2000 /* Check modification order */
2001 if (mo_graph->checkReachable(rf, act)) {
2002 /* rf --mo--> act */
2003 future_ordered = true;
2006 if (mo_graph->checkReachable(act, release))
2007 /* act --mo--> release */
2009 if (mo_graph->checkReachable(release, act) &&
2010 mo_graph->checkReachable(act, rf)) {
2011 /* release --mo-> act --mo--> rf */
2012 return true; /* complete */
2014 /* act may break release sequence */
2015 pending->writes.push_back(act);
2018 if (!future_ordered)
2019 certain = false; /* This thread is uncertain */
2023 release_heads->push_back(release);
2024 pending->writes.clear();
2026 pending->release = release;
2033 * An interface for getting the release sequence head(s) with which a
2034 * given ModelAction must synchronize. This function only returns a non-empty
2035 * result when it can locate a release sequence head with certainty. Otherwise,
2036 * it may mark the internal state of the ModelChecker so that it will handle
2037 * the release sequence at a later time, causing @a acquire to update its
2038 * synchronization at some later point in execution.
2040 * @param acquire The 'acquire' action that may synchronize with a release
2042 * @param read The read action that may read from a release sequence; this may
2043 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2044 * when 'acquire' is a fence-acquire)
2045 * @param release_heads A pass-by-reference return parameter. Will be filled
2046 * with the head(s) of the release sequence(s), if they exists with certainty.
2047 * @see ModelChecker::release_seq_heads
2049 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2050 ModelAction *read, rel_heads_list_t *release_heads)
2052 const ModelAction *rf = read->get_reads_from();
2053 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2054 sequence->acquire = acquire;
2055 sequence->read = read;
2057 if (!release_seq_heads(rf, release_heads, sequence)) {
2058 /* add act to 'lazy checking' list */
2059 pending_rel_seqs->push_back(sequence);
2061 snapshot_free(sequence);
2066 * Attempt to resolve all stashed operations that might synchronize with a
2067 * release sequence for a given location. This implements the "lazy" portion of
2068 * determining whether or not a release sequence was contiguous, since not all
2069 * modification order information is present at the time an action occurs.
2071 * @param location The location/object that should be checked for release
2072 * sequence resolutions. A NULL value means to check all locations.
2073 * @param work_queue The work queue to which to add work items as they are
2075 * @return True if any updates occurred (new synchronization, new mo_graph
2078 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2080 bool updated = false;
2081 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2082 while (it != pending_rel_seqs->end()) {
2083 struct release_seq *pending = *it;
2084 ModelAction *acquire = pending->acquire;
2085 const ModelAction *read = pending->read;
2087 /* Only resolve sequences on the given location, if provided */
2088 if (location && read->get_location() != location) {
2093 const ModelAction *rf = read->get_reads_from();
2094 rel_heads_list_t release_heads;
2096 complete = release_seq_heads(rf, &release_heads, pending);
2097 for (unsigned int i = 0; i < release_heads.size(); i++) {
2098 if (!acquire->has_synchronized_with(release_heads[i])) {
2099 if (acquire->synchronize_with(release_heads[i]))
2102 set_bad_synchronization();
2107 /* Re-check all pending release sequences */
2108 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2109 /* Re-check read-acquire for mo_graph edges */
2110 if (acquire->is_read())
2111 work_queue->push_back(MOEdgeWorkEntry(acquire));
2113 /* propagate synchronization to later actions */
2114 action_list_t::reverse_iterator rit = action_trace->rbegin();
2115 for (; (*rit) != acquire; rit++) {
2116 ModelAction *propagate = *rit;
2117 if (acquire->happens_before(propagate)) {
2118 propagate->synchronize_with(acquire);
2119 /* Re-check 'propagate' for mo_graph edges */
2120 work_queue->push_back(MOEdgeWorkEntry(propagate));
2125 it = pending_rel_seqs->erase(it);
2126 snapshot_free(pending);
2132 // If we resolved promises or data races, see if we have realized a data race.
2139 * Performs various bookkeeping operations for the current ModelAction. For
2140 * instance, adds action to the per-object, per-thread action vector and to the
2141 * action trace list of all thread actions.
2143 * @param act is the ModelAction to add.
2145 void ModelChecker::add_action_to_lists(ModelAction *act)
2147 int tid = id_to_int(act->get_tid());
2148 ModelAction *uninit = NULL;
2150 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2151 if (list->empty() && act->is_atomic_var()) {
2152 uninit = new_uninitialized_action(act->get_location());
2153 uninit_id = id_to_int(uninit->get_tid());
2154 list->push_back(uninit);
2156 list->push_back(act);
2158 action_trace->push_back(act);
2160 action_trace->push_front(uninit);
2162 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2163 if (tid >= (int)vec->size())
2164 vec->resize(priv->next_thread_id);
2165 (*vec)[tid].push_back(act);
2167 (*vec)[uninit_id].push_front(uninit);
2169 if ((int)thrd_last_action->size() <= tid)
2170 thrd_last_action->resize(get_num_threads());
2171 (*thrd_last_action)[tid] = act;
2173 (*thrd_last_action)[uninit_id] = uninit;
2175 if (act->is_fence() && act->is_release()) {
2176 if ((int)thrd_last_fence_release->size() <= tid)
2177 thrd_last_fence_release->resize(get_num_threads());
2178 (*thrd_last_fence_release)[tid] = act;
2181 if (act->is_wait()) {
2182 void *mutex_loc = (void *) act->get_value();
2183 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2185 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2186 if (tid >= (int)vec->size())
2187 vec->resize(priv->next_thread_id);
2188 (*vec)[tid].push_back(act);
2193 * @brief Get the last action performed by a particular Thread
2194 * @param tid The thread ID of the Thread in question
2195 * @return The last action in the thread
2197 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2199 int threadid = id_to_int(tid);
2200 if (threadid < (int)thrd_last_action->size())
2201 return (*thrd_last_action)[id_to_int(tid)];
2207 * @brief Get the last fence release performed by a particular Thread
2208 * @param tid The thread ID of the Thread in question
2209 * @return The last fence release in the thread, if one exists; NULL otherwise
2211 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2213 int threadid = id_to_int(tid);
2214 if (threadid < (int)thrd_last_fence_release->size())
2215 return (*thrd_last_fence_release)[id_to_int(tid)];
2221 * Gets the last memory_order_seq_cst write (in the total global sequence)
2222 * performed on a particular object (i.e., memory location), not including the
2224 * @param curr The current ModelAction; also denotes the object location to
2226 * @return The last seq_cst write
2228 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2230 void *location = curr->get_location();
2231 action_list_t *list = get_safe_ptr_action(obj_map, location);
2232 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2233 action_list_t::reverse_iterator rit;
2234 for (rit = list->rbegin(); rit != list->rend(); rit++)
2235 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2241 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2242 * performed in a particular thread, prior to a particular fence.
2243 * @param tid The ID of the thread to check
2244 * @param before_fence The fence from which to begin the search; if NULL, then
2245 * search for the most recent fence in the thread.
2246 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2248 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2250 /* All fences should have NULL location */
2251 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2252 action_list_t::reverse_iterator rit = list->rbegin();
2255 for (; rit != list->rend(); rit++)
2256 if (*rit == before_fence)
2259 ASSERT(*rit == before_fence);
2263 for (; rit != list->rend(); rit++)
2264 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2270 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2271 * location). This function identifies the mutex according to the current
2272 * action, which is presumed to perform on the same mutex.
2273 * @param curr The current ModelAction; also denotes the object location to
2275 * @return The last unlock operation
2277 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2279 void *location = curr->get_location();
2280 action_list_t *list = get_safe_ptr_action(obj_map, location);
2281 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2282 action_list_t::reverse_iterator rit;
2283 for (rit = list->rbegin(); rit != list->rend(); rit++)
2284 if ((*rit)->is_unlock() || (*rit)->is_wait())
2289 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2291 ModelAction *parent = get_last_action(tid);
2293 parent = get_thread(tid)->get_creation();
2298 * Returns the clock vector for a given thread.
2299 * @param tid The thread whose clock vector we want
2300 * @return Desired clock vector
2302 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2304 return get_parent_action(tid)->get_cv();
2308 * Resolve a set of Promises with a current write. The set is provided in the
2309 * Node corresponding to @a write.
2310 * @param write The ModelAction that is fulfilling Promises
2311 * @return True if promises were resolved; false otherwise
2313 bool ModelChecker::resolve_promises(ModelAction *write)
2315 bool resolved = false;
2316 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2318 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2319 Promise *promise = (*promises)[promise_index];
2320 if (write->get_node()->get_promise(i)) {
2321 ModelAction *read = promise->get_action();
2322 if (read->is_rmw()) {
2323 mo_graph->addRMWEdge(write, read);
2325 read_from(read, write);
2326 //First fix up the modification order for actions that happened
2328 r_modification_order(read, write);
2329 //Next fix up the modification order for actions that happened
2331 post_r_modification_order(read, write);
2332 //Make sure the promise's value matches the write's value
2333 ASSERT(promise->get_value() == write->get_value());
2336 promises->erase(promises->begin() + promise_index);
2337 actions_to_check.push_back(read);
2344 //Check whether reading these writes has made threads unable to
2347 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2348 ModelAction *read=actions_to_check[i];
2349 mo_check_promises(read->get_tid(), write, read);
2356 * Compute the set of promises that could potentially be satisfied by this
2357 * action. Note that the set computation actually appears in the Node, not in
2359 * @param curr The ModelAction that may satisfy promises
2361 void ModelChecker::compute_promises(ModelAction *curr)
2363 for (unsigned int i = 0; i < promises->size(); i++) {
2364 Promise *promise = (*promises)[i];
2365 const ModelAction *act = promise->get_action();
2366 if (!act->happens_before(curr) &&
2368 !act->could_synchronize_with(curr) &&
2369 !act->same_thread(curr) &&
2370 act->get_location() == curr->get_location() &&
2371 promise->get_value() == curr->get_value()) {
2372 curr->get_node()->set_promise(i, act->is_rmw());
2377 /** Checks promises in response to change in ClockVector Threads. */
2378 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2380 for (unsigned int i = 0; i < promises->size(); i++) {
2381 Promise *promise = (*promises)[i];
2382 const ModelAction *act = promise->get_action();
2383 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2384 merge_cv->synchronized_since(act)) {
2385 if (promise->eliminate_thread(tid)) {
2386 //Promise has failed
2387 priv->failed_promise = true;
2394 void ModelChecker::check_promises_thread_disabled()
2396 for (unsigned int i = 0; i < promises->size(); i++) {
2397 Promise *promise = (*promises)[i];
2398 if (promise->has_failed()) {
2399 priv->failed_promise = true;
2406 * @brief Checks promises in response to addition to modification order for
2411 * pthread is the thread that performed the read that created the promise
2413 * pread is the read that created the promise
2415 * pwrite is either the first write to same location as pread by
2416 * pthread that is sequenced after pread or the write read by the
2417 * first read to the same location as pread by pthread that is
2418 * sequenced after pread.
2420 * 1. If tid=pthread, then we check what other threads are reachable
2421 * through the mod order starting with pwrite. Those threads cannot
2422 * perform a write that will resolve the promise due to modification
2423 * order constraints.
2425 * 2. If the tid is not pthread, we check whether pwrite can reach the
2426 * action write through the modification order. If so, that thread
2427 * cannot perform a future write that will resolve the promise due to
2428 * modificatin order constraints.
2430 * @param tid The thread that either read from the model action write, or
2431 * actually did the model action write.
2433 * @param write The ModelAction representing the relevant write.
2434 * @param read The ModelAction that reads a promised write, or NULL otherwise.
2436 void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write, const ModelAction *read)
2438 void *location = write->get_location();
2439 for (unsigned int i = 0; i < promises->size(); i++) {
2440 Promise *promise = (*promises)[i];
2441 const ModelAction *act = promise->get_action();
2443 // Is this promise on the same location?
2444 if (act->get_location() != location)
2447 // same thread as the promise
2448 if (act->get_tid() == tid) {
2449 // make sure that the reader of this write happens after the promise
2450 if ((read == NULL) || (promise->get_action()->happens_before(read))) {
2451 // do we have a pwrite for the promise, if not, set it
2452 if (promise->get_write() == NULL) {
2453 promise->set_write(write);
2454 // The pwrite cannot happen before the promise
2455 if (write->happens_before(act) && (write != act)) {
2456 priv->failed_promise = true;
2461 if (mo_graph->checkPromise(write, promise)) {
2462 priv->failed_promise = true;
2468 // Don't do any lookups twice for the same thread
2469 if (promise->thread_is_eliminated(tid))
2472 if (promise->get_write() && mo_graph->checkReachable(promise->get_write(), write)) {
2473 if (promise->eliminate_thread(tid)) {
2474 priv->failed_promise = true;
2482 * Compute the set of writes that may break the current pending release
2483 * sequence. This information is extracted from previou release sequence
2486 * @param curr The current ModelAction. Must be a release sequence fixup
2489 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2491 if (pending_rel_seqs->empty())
2494 struct release_seq *pending = pending_rel_seqs->back();
2495 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2496 const ModelAction *write = pending->writes[i];
2497 curr->get_node()->add_relseq_break(write);
2500 /* NULL means don't break the sequence; just synchronize */
2501 curr->get_node()->add_relseq_break(NULL);
2505 * Build up an initial set of all past writes that this 'read' action may read
2506 * from. This set is determined by the clock vector's "happens before"
2508 * @param curr is the current ModelAction that we are exploring; it must be a
2511 void ModelChecker::build_reads_from_past(ModelAction *curr)
2513 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2515 ASSERT(curr->is_read());
2517 ModelAction *last_sc_write = NULL;
2519 if (curr->is_seqcst())
2520 last_sc_write = get_last_seq_cst_write(curr);
2522 /* Iterate over all threads */
2523 for (i = 0; i < thrd_lists->size(); i++) {
2524 /* Iterate over actions in thread, starting from most recent */
2525 action_list_t *list = &(*thrd_lists)[i];
2526 action_list_t::reverse_iterator rit;
2527 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2528 ModelAction *act = *rit;
2530 /* Only consider 'write' actions */
2531 if (!act->is_write() || act == curr)
2534 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2535 bool allow_read = true;
2537 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2539 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2543 curr->get_node()->add_read_from(act);
2545 /* Include at most one act per-thread that "happens before" curr */
2546 if (act->happens_before(curr))
2551 if (DBG_ENABLED()) {
2552 model_print("Reached read action:\n");
2554 model_print("Printing may_read_from\n");
2555 curr->get_node()->print_may_read_from();
2556 model_print("End printing may_read_from\n");
2560 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2563 /* UNINIT actions don't have a Node, and they never sleep */
2564 if (write->is_uninitialized())
2566 Node *prevnode = write->get_node()->get_parent();
2568 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2569 if (write->is_release() && thread_sleep)
2571 if (!write->is_rmw()) {
2574 if (write->get_reads_from() == NULL)
2576 write = write->get_reads_from();
2581 * @brief Create a new action representing an uninitialized atomic
2582 * @param location The memory location of the atomic object
2583 * @return A pointer to a new ModelAction
2585 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2587 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2588 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2589 act->create_cv(NULL);
2593 static void print_list(action_list_t *list)
2595 action_list_t::iterator it;
2597 model_print("---------------------------------------------------------------------\n");
2599 unsigned int hash = 0;
2601 for (it = list->begin(); it != list->end(); it++) {
2603 hash = hash^(hash<<3)^((*it)->hash());
2605 model_print("HASH %u\n", hash);
2606 model_print("---------------------------------------------------------------------\n");
2609 #if SUPPORT_MOD_ORDER_DUMP
2610 void ModelChecker::dumpGraph(char *filename) const
2613 sprintf(buffer, "%s.dot", filename);
2614 FILE *file = fopen(buffer, "w");
2615 fprintf(file, "digraph %s {\n", filename);
2616 mo_graph->dumpNodes(file);
2617 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2619 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2620 ModelAction *action = *it;
2621 if (action->is_read()) {
2622 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2623 if (action->get_reads_from() != NULL)
2624 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2626 if (thread_array[action->get_tid()] != NULL) {
2627 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2630 thread_array[action->get_tid()] = action;
2632 fprintf(file, "}\n");
2633 model_free(thread_array);
2638 /** @brief Prints an execution trace summary. */
2639 void ModelChecker::print_summary() const
2641 #if SUPPORT_MOD_ORDER_DUMP
2643 char buffername[100];
2644 sprintf(buffername, "exec%04u", stats.num_total);
2645 mo_graph->dumpGraphToFile(buffername);
2646 sprintf(buffername, "graph%04u", stats.num_total);
2647 dumpGraph(buffername);
2650 model_print("Execution %d:", stats.num_total);
2651 if (isfeasibleprefix())
2654 print_infeasibility(" INFEASIBLE");
2655 print_list(action_trace);
2660 * Add a Thread to the system for the first time. Should only be called once
2662 * @param t The Thread to add
2664 void ModelChecker::add_thread(Thread *t)
2666 thread_map->put(id_to_int(t->get_id()), t);
2667 scheduler->add_thread(t);
2671 * Removes a thread from the scheduler.
2672 * @param the thread to remove.
2674 void ModelChecker::remove_thread(Thread *t)
2676 scheduler->remove_thread(t);
2680 * @brief Get a Thread reference by its ID
2681 * @param tid The Thread's ID
2682 * @return A Thread reference
2684 Thread * ModelChecker::get_thread(thread_id_t tid) const
2686 return thread_map->get(id_to_int(tid));
2690 * @brief Get a reference to the Thread in which a ModelAction was executed
2691 * @param act The ModelAction
2692 * @return A Thread reference
2694 Thread * ModelChecker::get_thread(const ModelAction *act) const
2696 return get_thread(act->get_tid());
2700 * @brief Check if a Thread is currently enabled
2701 * @param t The Thread to check
2702 * @return True if the Thread is currently enabled
2704 bool ModelChecker::is_enabled(Thread *t) const
2706 return scheduler->is_enabled(t);
2710 * @brief Check if a Thread is currently enabled
2711 * @param tid The ID of the Thread to check
2712 * @return True if the Thread is currently enabled
2714 bool ModelChecker::is_enabled(thread_id_t tid) const
2716 return scheduler->is_enabled(tid);
2720 * Switch from a user-context to the "master thread" context (a.k.a. system
2721 * context). This switch is made with the intention of exploring a particular
2722 * model-checking action (described by a ModelAction object). Must be called
2723 * from a user-thread context.
2725 * @param act The current action that will be explored. May be NULL only if
2726 * trace is exiting via an assertion (see ModelChecker::set_assert and
2727 * ModelChecker::has_asserted).
2728 * @return Return the value returned by the current action
2730 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2733 Thread *old = thread_current();
2734 set_current_action(act);
2735 old->set_state(THREAD_READY);
2736 if (Thread::swap(old, &system_context) < 0) {
2737 perror("swap threads");
2740 return old->get_return_value();
2744 * Takes the next step in the execution, if possible.
2745 * @param curr The current step to take
2746 * @return Returns true (success) if a step was taken and false otherwise.
2748 bool ModelChecker::take_step(ModelAction *curr)
2753 Thread *curr_thrd = get_thread(curr);
2754 ASSERT(curr_thrd->get_state() == THREAD_READY);
2756 curr = check_current_action(curr);
2758 /* Infeasible -> don't take any more steps */
2759 if (is_infeasible())
2761 else if (isfeasibleprefix() && have_bug_reports()) {
2766 if (params.bound != 0)
2767 if (priv->used_sequence_numbers > params.bound)
2770 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2771 scheduler->remove_thread(curr_thrd);
2773 Thread *next_thrd = get_next_thread(curr);
2774 next_thrd = scheduler->next_thread(next_thrd);
2776 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2777 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2780 * Launch end-of-execution release sequence fixups only when there are:
2782 * (1) no more user threads to run (or when execution replay chooses
2783 * the 'model_thread')
2784 * (2) pending release sequences
2785 * (3) pending assertions (i.e., data races)
2786 * (4) no pending promises
2788 if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
2789 is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
2790 model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
2791 pending_rel_seqs->size());
2792 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2793 std::memory_order_seq_cst, NULL, VALUE_NONE,
2795 set_current_action(fixup);
2799 /* next_thrd == NULL -> don't take any more steps */
2803 next_thrd->set_state(THREAD_RUNNING);
2805 if (next_thrd->get_pending() != NULL) {
2806 /* restart a pending action */
2807 set_current_action(next_thrd->get_pending());
2808 next_thrd->set_pending(NULL);
2809 next_thrd->set_state(THREAD_READY);
2813 /* Return false only if swap fails with an error */
2814 return (Thread::swap(&system_context, next_thrd) == 0);
2817 /** Wrapper to run the user's main function, with appropriate arguments */
2818 void user_main_wrapper(void *)
2820 user_main(model->params.argc, model->params.argv);
2823 /** @brief Run ModelChecker for the user program */
2824 void ModelChecker::run()
2828 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2832 /* Run user thread up to its first action */
2833 scheduler->next_thread(t);
2834 Thread::swap(&system_context, t);
2836 /* Wait for all threads to complete */
2837 while (take_step(priv->current_action));
2838 } while (next_execution());