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() :
42 /* First thread created will have id INITIAL_THREAD_ID */
43 next_thread_id(INITIAL_THREAD_ID),
44 used_sequence_numbers(0),
48 failed_promise(false),
49 too_many_reads(false),
50 no_valid_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 unsigned int next_thread_id;
62 modelclock_t used_sequence_numbers;
63 ModelAction *next_backtrack;
64 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
65 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 */
163 * FIXME: if we utilize partial rollback, we will need to free only
164 * those pending actions which were NOT pending before the rollback
167 for (unsigned int i = 0; i < get_num_threads(); i++)
168 delete get_thread(int_to_id(i))->get_pending();
170 snapshot_backtrack_before(0);
173 /** @return a thread ID for a new Thread */
174 thread_id_t ModelChecker::get_next_id()
176 return priv->next_thread_id++;
179 /** @return the number of user threads created during this execution */
180 unsigned int ModelChecker::get_num_threads() const
182 return priv->next_thread_id;
186 * Must be called from user-thread context (e.g., through the global
187 * thread_current() interface)
189 * @return The currently executing Thread.
191 Thread * ModelChecker::get_current_thread() const
193 return scheduler->get_current_thread();
196 /** @return a sequence number for a new ModelAction */
197 modelclock_t ModelChecker::get_next_seq_num()
199 return ++priv->used_sequence_numbers;
202 Node * ModelChecker::get_curr_node() const
204 return node_stack->get_head();
208 * @brief Choose the next thread to execute.
210 * This function chooses the next thread that should execute. It can force the
211 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
212 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
213 * The model-checker may have no preference regarding the next thread (i.e.,
214 * when exploring a new execution ordering), in which case we defer to the
217 * @param curr Optional: The current ModelAction. Only used if non-NULL and it
218 * might guide the choice of next thread (i.e., THREAD_CREATE should be
219 * followed by THREAD_START, or ATOMIC_RMWR followed by ATOMIC_{RMW,RMWC})
220 * @return The next chosen thread to run, if any exist. Or else if no threads
221 * remain to be executed, return NULL.
223 Thread * ModelChecker::get_next_thread(ModelAction *curr)
228 /* Do not split atomic actions. */
230 return get_thread(curr);
231 else if (curr->get_type() == THREAD_CREATE)
232 return curr->get_thread_operand();
236 * Have we completed exploring the preselected path? Then let the
240 return scheduler->select_next_thread();
242 /* Else, we are trying to replay an execution */
243 ModelAction *next = node_stack->get_next()->get_action();
245 if (next == diverge) {
246 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
247 earliest_diverge = diverge;
249 Node *nextnode = next->get_node();
250 Node *prevnode = nextnode->get_parent();
251 scheduler->update_sleep_set(prevnode);
253 /* Reached divergence point */
254 if (nextnode->increment_misc()) {
255 /* The next node will try to satisfy a different misc_index values. */
256 tid = next->get_tid();
257 node_stack->pop_restofstack(2);
258 } else if (nextnode->increment_promise()) {
259 /* The next node will try to satisfy a different set of promises. */
260 tid = next->get_tid();
261 node_stack->pop_restofstack(2);
262 } else if (nextnode->increment_read_from()) {
263 /* The next node will read from a different value. */
264 tid = next->get_tid();
265 node_stack->pop_restofstack(2);
266 } else if (nextnode->increment_future_value()) {
267 /* The next node will try to read from a different future value. */
268 tid = next->get_tid();
269 node_stack->pop_restofstack(2);
270 } else if (nextnode->increment_relseq_break()) {
271 /* The next node will try to resolve a release sequence differently */
272 tid = next->get_tid();
273 node_stack->pop_restofstack(2);
276 /* Make a different thread execute for next step */
277 scheduler->add_sleep(get_thread(next->get_tid()));
278 tid = prevnode->get_next_backtrack();
279 /* Make sure the backtracked thread isn't sleeping. */
280 node_stack->pop_restofstack(1);
281 if (diverge == earliest_diverge) {
282 earliest_diverge = prevnode->get_action();
285 /* The correct sleep set is in the parent node. */
288 DEBUG("*** Divergence point ***\n");
292 tid = next->get_tid();
294 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
295 ASSERT(tid != THREAD_ID_T_NONE);
296 return thread_map->get(id_to_int(tid));
300 * We need to know what the next actions of all threads in the sleep
301 * set will be. This method computes them and stores the actions at
302 * the corresponding thread object's pending action.
305 void ModelChecker::execute_sleep_set()
307 for (unsigned int i = 0; i < get_num_threads(); i++) {
308 thread_id_t tid = int_to_id(i);
309 Thread *thr = get_thread(tid);
310 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
311 thr->get_pending()->set_sleep_flag();
316 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
318 for (unsigned int i = 0; i < get_num_threads(); i++) {
319 Thread *thr = get_thread(int_to_id(i));
320 if (scheduler->is_sleep_set(thr)) {
321 ModelAction *pending_act = thr->get_pending();
322 if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
323 //Remove this thread from sleep set
324 scheduler->remove_sleep(thr);
329 /** @brief Alert the model-checker that an incorrectly-ordered
330 * synchronization was made */
331 void ModelChecker::set_bad_synchronization()
333 priv->bad_synchronization = true;
337 * Check whether the current trace has triggered an assertion which should halt
340 * @return True, if the execution should be aborted; false otherwise
342 bool ModelChecker::has_asserted() const
344 return priv->asserted;
348 * Trigger a trace assertion which should cause this execution to be halted.
349 * This can be due to a detected bug or due to an infeasibility that should
352 void ModelChecker::set_assert()
354 priv->asserted = true;
358 * Check if we are in a deadlock. Should only be called at the end of an
359 * execution, although it should not give false positives in the middle of an
360 * execution (there should be some ENABLED thread).
362 * @return True if program is in a deadlock; false otherwise
364 bool ModelChecker::is_deadlocked() const
366 bool blocking_threads = false;
367 for (unsigned int i = 0; i < get_num_threads(); i++) {
368 thread_id_t tid = int_to_id(i);
371 Thread *t = get_thread(tid);
372 if (!t->is_model_thread() && t->get_pending())
373 blocking_threads = true;
375 return blocking_threads;
379 * Check if this is a complete execution. That is, have all thread completed
380 * execution (rather than exiting because sleep sets have forced a redundant
383 * @return True if the execution is complete.
385 bool ModelChecker::is_complete_execution() const
387 for (unsigned int i = 0; i < get_num_threads(); i++)
388 if (is_enabled(int_to_id(i)))
394 * @brief Assert a bug in the executing program.
396 * Use this function to assert any sort of bug in the user program. If the
397 * current trace is feasible (actually, a prefix of some feasible execution),
398 * then this execution will be aborted, printing the appropriate message. If
399 * the current trace is not yet feasible, the error message will be stashed and
400 * printed if the execution ever becomes feasible.
402 * @param msg Descriptive message for the bug (do not include newline char)
403 * @return True if bug is immediately-feasible
405 bool ModelChecker::assert_bug(const char *msg)
407 priv->bugs.push_back(new bug_message(msg));
409 if (isfeasibleprefix()) {
417 * @brief Assert a bug in the executing program, asserted by a user thread
418 * @see ModelChecker::assert_bug
419 * @param msg Descriptive message for the bug (do not include newline char)
421 void ModelChecker::assert_user_bug(const char *msg)
423 /* If feasible bug, bail out now */
425 switch_to_master(NULL);
428 /** @return True, if any bugs have been reported for this execution */
429 bool ModelChecker::have_bug_reports() const
431 return priv->bugs.size() != 0;
434 /** @brief Print bug report listing for this execution (if any bugs exist) */
435 void ModelChecker::print_bugs() const
437 if (have_bug_reports()) {
438 model_print("Bug report: %zu bug%s detected\n",
440 priv->bugs.size() > 1 ? "s" : "");
441 for (unsigned int i = 0; i < priv->bugs.size(); i++)
442 priv->bugs[i]->print();
447 * @brief Record end-of-execution stats
449 * Must be run when exiting an execution. Records various stats.
450 * @see struct execution_stats
452 void ModelChecker::record_stats()
455 if (!isfeasibleprefix())
456 stats.num_infeasible++;
457 else if (have_bug_reports())
458 stats.num_buggy_executions++;
459 else if (is_complete_execution())
460 stats.num_complete++;
462 stats.num_redundant++;
465 /** @brief Print execution stats */
466 void ModelChecker::print_stats() const
468 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
469 model_print("Number of redundant executions: %d\n", stats.num_redundant);
470 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
471 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
472 model_print("Total executions: %d\n", stats.num_total);
473 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
477 * @brief End-of-exeuction print
478 * @param printbugs Should any existing bugs be printed?
480 void ModelChecker::print_execution(bool printbugs) const
482 print_program_output();
484 if (DBG_ENABLED() || params.verbose) {
485 model_print("Earliest divergence point since last feasible execution:\n");
486 if (earliest_diverge)
487 earliest_diverge->print();
489 model_print("(Not set)\n");
495 /* Don't print invalid bugs */
504 * Queries the model-checker for more executions to explore and, if one
505 * exists, resets the model-checker state to execute a new execution.
507 * @return If there are more executions to explore, return true. Otherwise,
510 bool ModelChecker::next_execution()
513 /* Is this execution a feasible execution that's worth bug-checking? */
514 bool complete = isfeasibleprefix() && (is_complete_execution() ||
517 /* End-of-execution bug checks */
520 assert_bug("Deadlock detected");
528 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
529 print_execution(complete);
531 clear_program_output();
534 earliest_diverge = NULL;
536 if ((diverge = get_next_backtrack()) == NULL)
540 model_print("Next execution will diverge at:\n");
544 reset_to_initial_state();
548 ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const
550 /* Only perform release/acquire fence backtracking for stores */
551 if (!act->is_write())
554 /* Find a fence-release (or, act is a release) */
555 ModelAction *last_release;
556 if (act->is_release())
559 last_release = get_last_fence_release(act->get_tid());
563 std::vector< ModelAction *, ModelAlloc<ModelAction *> > acquire_fences(get_num_threads(), NULL);
564 std::vector< ModelAction *, ModelAlloc<ModelAction *> > prior_loads(get_num_threads(), NULL);
565 bool found_acquire_fences = false;
569 * load --sb-> fence-acquire */
570 action_list_t *list = action_trace;
571 action_list_t::reverse_iterator rit;
572 for (rit = list->rbegin(); rit != list->rend(); rit++) {
573 ModelAction *prev = *rit;
574 if (act->same_thread(prev))
577 int tid = id_to_int(prev->get_tid());
579 if (prev->is_read() && act->same_var(prev)) {
580 if (prev->is_acquire()) {
581 /* Found most recent load-acquire, don't need
582 * to search for more fences */
583 if (!found_acquire_fences)
586 prior_loads[tid] = prev;
589 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
590 found_acquire_fences = true;
591 acquire_fences[tid] = prev;
595 ModelAction *latest_backtrack = NULL;
596 for (unsigned int i = 0; i < acquire_fences.size(); i++)
597 if (acquire_fences[i] && prior_loads[i])
598 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
599 latest_backtrack = acquire_fences[i];
600 return latest_backtrack;
603 ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const
605 switch (act->get_type()) {
606 /* case ATOMIC_FENCE: fences don't directly cause backtracking */
610 ModelAction *ret = NULL;
612 /* linear search: from most recent to oldest */
613 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
614 action_list_t::reverse_iterator rit;
615 for (rit = list->rbegin(); rit != list->rend(); rit++) {
616 ModelAction *prev = *rit;
617 if (prev->could_synchronize_with(act)) {
623 ModelAction *ret2 = get_last_fence_conflict(act);
633 case ATOMIC_TRYLOCK: {
634 /* linear search: from most recent to oldest */
635 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
636 action_list_t::reverse_iterator rit;
637 for (rit = list->rbegin(); rit != list->rend(); rit++) {
638 ModelAction *prev = *rit;
639 if (act->is_conflicting_lock(prev))
644 case ATOMIC_UNLOCK: {
645 /* linear search: from most recent to oldest */
646 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
647 action_list_t::reverse_iterator rit;
648 for (rit = list->rbegin(); rit != list->rend(); rit++) {
649 ModelAction *prev = *rit;
650 if (!act->same_thread(prev) && prev->is_failed_trylock())
656 /* linear search: from most recent to oldest */
657 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
658 action_list_t::reverse_iterator rit;
659 for (rit = list->rbegin(); rit != list->rend(); rit++) {
660 ModelAction *prev = *rit;
661 if (!act->same_thread(prev) && prev->is_failed_trylock())
663 if (!act->same_thread(prev) && prev->is_notify())
669 case ATOMIC_NOTIFY_ALL:
670 case ATOMIC_NOTIFY_ONE: {
671 /* linear search: from most recent to oldest */
672 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
673 action_list_t::reverse_iterator rit;
674 for (rit = list->rbegin(); rit != list->rend(); rit++) {
675 ModelAction *prev = *rit;
676 if (!act->same_thread(prev) && prev->is_wait())
687 /** This method finds backtracking points where we should try to
688 * reorder the parameter ModelAction against.
690 * @param the ModelAction to find backtracking points for.
692 void ModelChecker::set_backtracking(ModelAction *act)
694 Thread *t = get_thread(act);
695 ModelAction *prev = get_last_conflict(act);
699 Node *node = prev->get_node()->get_parent();
701 int low_tid, high_tid;
702 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
703 low_tid = id_to_int(act->get_tid());
704 high_tid = low_tid + 1;
707 high_tid = get_num_threads();
710 for (int i = low_tid; i < high_tid; i++) {
711 thread_id_t tid = int_to_id(i);
713 /* Make sure this thread can be enabled here. */
714 if (i >= node->get_num_threads())
717 /* Don't backtrack into a point where the thread is disabled or sleeping. */
718 if (node->enabled_status(tid) != THREAD_ENABLED)
721 /* Check if this has been explored already */
722 if (node->has_been_explored(tid))
725 /* See if fairness allows */
726 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
728 for (int t = 0; t < node->get_num_threads(); t++) {
729 thread_id_t tother = int_to_id(t);
730 if (node->is_enabled(tother) && node->has_priority(tother)) {
738 /* Cache the latest backtracking point */
739 set_latest_backtrack(prev);
741 /* If this is a new backtracking point, mark the tree */
742 if (!node->set_backtrack(tid))
744 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
745 id_to_int(prev->get_tid()),
746 id_to_int(t->get_id()));
755 * @brief Cache the a backtracking point as the "most recent", if eligible
757 * Note that this does not prepare the NodeStack for this backtracking
758 * operation, it only caches the action on a per-execution basis
760 * @param act The operation at which we should explore a different next action
761 * (i.e., backtracking point)
762 * @return True, if this action is now the most recent backtracking point;
765 bool ModelChecker::set_latest_backtrack(ModelAction *act)
767 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
768 priv->next_backtrack = act;
775 * Returns last backtracking point. The model checker will explore a different
776 * path for this point in the next execution.
777 * @return The ModelAction at which the next execution should diverge.
779 ModelAction * ModelChecker::get_next_backtrack()
781 ModelAction *next = priv->next_backtrack;
782 priv->next_backtrack = NULL;
787 * Processes a read or rmw model action.
788 * @param curr is the read model action to process.
789 * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
790 * @return True if processing this read updates the mo_graph.
792 bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
794 uint64_t value = VALUE_NONE;
795 bool updated = false;
797 const ModelAction *reads_from = curr->get_node()->get_read_from();
798 if (reads_from != NULL) {
799 mo_graph->startChanges();
801 value = reads_from->get_value();
802 bool r_status = false;
804 if (!second_part_of_rmw) {
805 check_recency(curr, reads_from);
806 r_status = r_modification_order(curr, reads_from);
809 if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
810 mo_graph->rollbackChanges();
811 priv->too_many_reads = false;
815 read_from(curr, reads_from);
816 mo_graph->commitChanges();
817 mo_check_promises(curr, true);
820 } else if (!second_part_of_rmw) {
821 /* Read from future value */
822 struct future_value fv = curr->get_node()->get_future_value();
823 Promise *promise = new Promise(curr, fv);
825 curr->set_read_from_promise(promise);
826 promises->push_back(promise);
827 mo_graph->startChanges();
828 updated = r_modification_order(curr, promise);
829 mo_graph->commitChanges();
831 get_thread(curr)->set_return_value(value);
837 * Processes a lock, trylock, or unlock model action. @param curr is
838 * the read model action to process.
840 * The try lock operation checks whether the lock is taken. If not,
841 * it falls to the normal lock operation case. If so, it returns
844 * The lock operation has already been checked that it is enabled, so
845 * it just grabs the lock and synchronizes with the previous unlock.
847 * The unlock operation has to re-enable all of the threads that are
848 * waiting on the lock.
850 * @return True if synchronization was updated; false otherwise
852 bool ModelChecker::process_mutex(ModelAction *curr)
854 std::mutex *mutex = NULL;
855 struct std::mutex_state *state = NULL;
857 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
858 mutex = (std::mutex *)curr->get_location();
859 state = mutex->get_state();
860 } else if (curr->is_wait()) {
861 mutex = (std::mutex *)curr->get_value();
862 state = mutex->get_state();
865 switch (curr->get_type()) {
866 case ATOMIC_TRYLOCK: {
867 bool success = !state->islocked;
868 curr->set_try_lock(success);
870 get_thread(curr)->set_return_value(0);
873 get_thread(curr)->set_return_value(1);
875 //otherwise fall into the lock case
877 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
878 assert_bug("Lock access before initialization");
879 state->islocked = true;
880 ModelAction *unlock = get_last_unlock(curr);
881 //synchronize with the previous unlock statement
882 if (unlock != NULL) {
883 curr->synchronize_with(unlock);
888 case ATOMIC_UNLOCK: {
890 state->islocked = false;
891 //wake up the other threads
892 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
893 //activate all the waiting threads
894 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
895 scheduler->wake(get_thread(*rit));
902 state->islocked = false;
903 //wake up the other threads
904 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
905 //activate all the waiting threads
906 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
907 scheduler->wake(get_thread(*rit));
910 //check whether we should go to sleep or not...simulate spurious failures
911 if (curr->get_node()->get_misc() == 0) {
912 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
914 scheduler->sleep(get_thread(curr));
918 case ATOMIC_NOTIFY_ALL: {
919 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
920 //activate all the waiting threads
921 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
922 scheduler->wake(get_thread(*rit));
927 case ATOMIC_NOTIFY_ONE: {
928 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
929 int wakeupthread = curr->get_node()->get_misc();
930 action_list_t::iterator it = waiters->begin();
931 advance(it, wakeupthread);
932 scheduler->wake(get_thread(*it));
943 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
945 /* Do more ambitious checks now that mo is more complete */
946 if (mo_may_allow(writer, reader)) {
947 Node *node = reader->get_node();
949 /* Find an ancestor thread which exists at the time of the reader */
950 Thread *write_thread = get_thread(writer);
951 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
952 write_thread = write_thread->get_parent();
954 struct future_value fv = {
956 writer->get_seq_number() + params.maxfuturedelay,
957 write_thread->get_id(),
959 if (node->add_future_value(fv))
960 set_latest_backtrack(reader);
965 * Process a write ModelAction
966 * @param curr The ModelAction to process
967 * @return True if the mo_graph was updated or promises were resolved
969 bool ModelChecker::process_write(ModelAction *curr)
971 bool updated_mod_order = w_modification_order(curr);
972 bool updated_promises = resolve_promises(curr);
974 if (promises->size() == 0) {
975 for (unsigned int i = 0; i < futurevalues->size(); i++) {
976 struct PendingFutureValue pfv = (*futurevalues)[i];
977 add_future_value(pfv.writer, pfv.act);
979 futurevalues->clear();
982 mo_graph->commitChanges();
983 mo_check_promises(curr, false);
985 get_thread(curr)->set_return_value(VALUE_NONE);
986 return updated_mod_order || updated_promises;
990 * Process a fence ModelAction
991 * @param curr The ModelAction to process
992 * @return True if synchronization was updated
994 bool ModelChecker::process_fence(ModelAction *curr)
997 * fence-relaxed: no-op
998 * fence-release: only log the occurence (not in this function), for
999 * use in later synchronization
1000 * fence-acquire (this function): search for hypothetical release
1003 bool updated = false;
1004 if (curr->is_acquire()) {
1005 action_list_t *list = action_trace;
1006 action_list_t::reverse_iterator rit;
1007 /* Find X : is_read(X) && X --sb-> curr */
1008 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1009 ModelAction *act = *rit;
1012 if (act->get_tid() != curr->get_tid())
1014 /* Stop at the beginning of the thread */
1015 if (act->is_thread_start())
1017 /* Stop once we reach a prior fence-acquire */
1018 if (act->is_fence() && act->is_acquire())
1020 if (!act->is_read())
1022 /* read-acquire will find its own release sequences */
1023 if (act->is_acquire())
1026 /* Establish hypothetical release sequences */
1027 rel_heads_list_t release_heads;
1028 get_release_seq_heads(curr, act, &release_heads);
1029 for (unsigned int i = 0; i < release_heads.size(); i++)
1030 if (!curr->synchronize_with(release_heads[i]))
1031 set_bad_synchronization();
1032 if (release_heads.size() != 0)
1040 * @brief Process the current action for thread-related activity
1042 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1043 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1044 * synchronization, etc. This function is a no-op for non-THREAD actions
1045 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1047 * @param curr The current action
1048 * @return True if synchronization was updated or a thread completed
1050 bool ModelChecker::process_thread_action(ModelAction *curr)
1052 bool updated = false;
1054 switch (curr->get_type()) {
1055 case THREAD_CREATE: {
1056 thrd_t *thrd = (thrd_t *)curr->get_location();
1057 struct thread_params *params = (struct thread_params *)curr->get_value();
1058 Thread *th = new Thread(thrd, params->func, params->arg);
1060 th->set_creation(curr);
1061 /* Promises can be satisfied by children */
1062 for (unsigned int i = 0; i < promises->size(); i++) {
1063 Promise *promise = (*promises)[i];
1064 if (promise->thread_is_available(curr->get_tid()))
1065 promise->add_thread(th->get_id());
1070 Thread *blocking = curr->get_thread_operand();
1071 ModelAction *act = get_last_action(blocking->get_id());
1072 curr->synchronize_with(act);
1073 updated = true; /* trigger rel-seq checks */
1076 case THREAD_FINISH: {
1077 Thread *th = get_thread(curr);
1078 while (!th->wait_list_empty()) {
1079 ModelAction *act = th->pop_wait_list();
1080 scheduler->wake(get_thread(act));
1083 /* Completed thread can't satisfy promises */
1084 for (unsigned int i = 0; i < promises->size(); i++) {
1085 Promise *promise = (*promises)[i];
1086 if (promise->thread_is_available(th->get_id()))
1087 if (promise->eliminate_thread(th->get_id()))
1088 priv->failed_promise = true;
1090 updated = true; /* trigger rel-seq checks */
1093 case THREAD_START: {
1094 check_promises(curr->get_tid(), NULL, curr->get_cv());
1105 * @brief Process the current action for release sequence fixup activity
1107 * Performs model-checker release sequence fixups for the current action,
1108 * forcing a single pending release sequence to break (with a given, potential
1109 * "loose" write) or to complete (i.e., synchronize). If a pending release
1110 * sequence forms a complete release sequence, then we must perform the fixup
1111 * synchronization, mo_graph additions, etc.
1113 * @param curr The current action; must be a release sequence fixup action
1114 * @param work_queue The work queue to which to add work items as they are
1117 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1119 const ModelAction *write = curr->get_node()->get_relseq_break();
1120 struct release_seq *sequence = pending_rel_seqs->back();
1121 pending_rel_seqs->pop_back();
1123 ModelAction *acquire = sequence->acquire;
1124 const ModelAction *rf = sequence->rf;
1125 const ModelAction *release = sequence->release;
1129 ASSERT(release->same_thread(rf));
1131 if (write == NULL) {
1133 * @todo Forcing a synchronization requires that we set
1134 * modification order constraints. For instance, we can't allow
1135 * a fixup sequence in which two separate read-acquire
1136 * operations read from the same sequence, where the first one
1137 * synchronizes and the other doesn't. Essentially, we can't
1138 * allow any writes to insert themselves between 'release' and
1142 /* Must synchronize */
1143 if (!acquire->synchronize_with(release)) {
1144 set_bad_synchronization();
1147 /* Re-check all pending release sequences */
1148 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1149 /* Re-check act for mo_graph edges */
1150 work_queue->push_back(MOEdgeWorkEntry(acquire));
1152 /* propagate synchronization to later actions */
1153 action_list_t::reverse_iterator rit = action_trace->rbegin();
1154 for (; (*rit) != acquire; rit++) {
1155 ModelAction *propagate = *rit;
1156 if (acquire->happens_before(propagate)) {
1157 propagate->synchronize_with(acquire);
1158 /* Re-check 'propagate' for mo_graph edges */
1159 work_queue->push_back(MOEdgeWorkEntry(propagate));
1163 /* Break release sequence with new edges:
1164 * release --mo--> write --mo--> rf */
1165 mo_graph->addEdge(release, write);
1166 mo_graph->addEdge(write, rf);
1169 /* See if we have realized a data race */
1174 * Initialize the current action by performing one or more of the following
1175 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1176 * in the NodeStack, manipulating backtracking sets, allocating and
1177 * initializing clock vectors, and computing the promises to fulfill.
1179 * @param curr The current action, as passed from the user context; may be
1180 * freed/invalidated after the execution of this function, with a different
1181 * action "returned" its place (pass-by-reference)
1182 * @return True if curr is a newly-explored action; false otherwise
1184 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1186 ModelAction *newcurr;
1188 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1189 newcurr = process_rmw(*curr);
1192 if (newcurr->is_rmw())
1193 compute_promises(newcurr);
1199 (*curr)->set_seq_number(get_next_seq_num());
1201 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1203 /* First restore type and order in case of RMW operation */
1204 if ((*curr)->is_rmwr())
1205 newcurr->copy_typeandorder(*curr);
1207 ASSERT((*curr)->get_location() == newcurr->get_location());
1208 newcurr->copy_from_new(*curr);
1210 /* Discard duplicate ModelAction; use action from NodeStack */
1213 /* Always compute new clock vector */
1214 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1217 return false; /* Action was explored previously */
1221 /* Always compute new clock vector */
1222 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1224 /* Assign most recent release fence */
1225 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1228 * Perform one-time actions when pushing new ModelAction onto
1231 if (newcurr->is_write())
1232 compute_promises(newcurr);
1233 else if (newcurr->is_relseq_fixup())
1234 compute_relseq_breakwrites(newcurr);
1235 else if (newcurr->is_wait())
1236 newcurr->get_node()->set_misc_max(2);
1237 else if (newcurr->is_notify_one()) {
1238 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1240 return true; /* This was a new ModelAction */
1245 * @brief Establish reads-from relation between two actions
1247 * Perform basic operations involved with establishing a concrete rf relation,
1248 * including setting the ModelAction data and checking for release sequences.
1250 * @param act The action that is reading (must be a read)
1251 * @param rf The action from which we are reading (must be a write)
1253 * @return True if this read established synchronization
1255 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1257 act->set_read_from(rf);
1258 if (rf != NULL && act->is_acquire()) {
1259 rel_heads_list_t release_heads;
1260 get_release_seq_heads(act, act, &release_heads);
1261 int num_heads = release_heads.size();
1262 for (unsigned int i = 0; i < release_heads.size(); i++)
1263 if (!act->synchronize_with(release_heads[i])) {
1264 set_bad_synchronization();
1267 return num_heads > 0;
1273 * @brief Check whether a model action is enabled.
1275 * Checks whether a lock or join operation would be successful (i.e., is the
1276 * lock already locked, or is the joined thread already complete). If not, put
1277 * the action in a waiter list.
1279 * @param curr is the ModelAction to check whether it is enabled.
1280 * @return a bool that indicates whether the action is enabled.
1282 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1283 if (curr->is_lock()) {
1284 std::mutex *lock = (std::mutex *)curr->get_location();
1285 struct std::mutex_state *state = lock->get_state();
1286 if (state->islocked) {
1287 //Stick the action in the appropriate waiting queue
1288 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1291 } else if (curr->get_type() == THREAD_JOIN) {
1292 Thread *blocking = (Thread *)curr->get_location();
1293 if (!blocking->is_complete()) {
1294 blocking->push_wait_list(curr);
1303 * This is the heart of the model checker routine. It performs model-checking
1304 * actions corresponding to a given "current action." Among other processes, it
1305 * calculates reads-from relationships, updates synchronization clock vectors,
1306 * forms a memory_order constraints graph, and handles replay/backtrack
1307 * execution when running permutations of previously-observed executions.
1309 * @param curr The current action to process
1310 * @return The ModelAction that is actually executed; may be different than
1311 * curr; may be NULL, if the current action is not enabled to run
1313 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1316 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1318 if (!check_action_enabled(curr)) {
1319 /* Make the execution look like we chose to run this action
1320 * much later, when a lock/join can succeed */
1321 get_thread(curr)->set_pending(curr);
1322 scheduler->sleep(get_thread(curr));
1326 bool newly_explored = initialize_curr_action(&curr);
1332 wake_up_sleeping_actions(curr);
1334 /* Add the action to lists before any other model-checking tasks */
1335 if (!second_part_of_rmw)
1336 add_action_to_lists(curr);
1338 /* Build may_read_from set for newly-created actions */
1339 if (newly_explored && curr->is_read())
1340 build_reads_from_past(curr);
1342 /* Initialize work_queue with the "current action" work */
1343 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1344 while (!work_queue.empty() && !has_asserted()) {
1345 WorkQueueEntry work = work_queue.front();
1346 work_queue.pop_front();
1348 switch (work.type) {
1349 case WORK_CHECK_CURR_ACTION: {
1350 ModelAction *act = work.action;
1351 bool update = false; /* update this location's release seq's */
1352 bool update_all = false; /* update all release seq's */
1354 if (process_thread_action(curr))
1357 if (act->is_read() && process_read(act, second_part_of_rmw))
1360 if (act->is_write() && process_write(act))
1363 if (act->is_fence() && process_fence(act))
1366 if (act->is_mutex_op() && process_mutex(act))
1369 if (act->is_relseq_fixup())
1370 process_relseq_fixup(curr, &work_queue);
1373 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1375 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1378 case WORK_CHECK_RELEASE_SEQ:
1379 resolve_release_sequences(work.location, &work_queue);
1381 case WORK_CHECK_MO_EDGES: {
1382 /** @todo Complete verification of work_queue */
1383 ModelAction *act = work.action;
1384 bool updated = false;
1386 if (act->is_read()) {
1387 const ModelAction *rf = act->get_reads_from();
1388 const Promise *promise = act->get_reads_from_promise();
1390 if (r_modification_order(act, rf))
1392 } else if (promise) {
1393 if (r_modification_order(act, promise))
1397 if (act->is_write()) {
1398 if (w_modification_order(act))
1401 mo_graph->commitChanges();
1404 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1413 check_curr_backtracking(curr);
1414 set_backtracking(curr);
1418 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1420 Node *currnode = curr->get_node();
1421 Node *parnode = currnode->get_parent();
1423 if ((parnode && !parnode->backtrack_empty()) ||
1424 !currnode->misc_empty() ||
1425 !currnode->read_from_empty() ||
1426 !currnode->future_value_empty() ||
1427 !currnode->promise_empty() ||
1428 !currnode->relseq_break_empty()) {
1429 set_latest_backtrack(curr);
1433 bool ModelChecker::promises_expired() const
1435 for (unsigned int i = 0; i < promises->size(); i++) {
1436 Promise *promise = (*promises)[i];
1437 if (promise->get_expiration() < priv->used_sequence_numbers)
1444 * This is the strongest feasibility check available.
1445 * @return whether the current trace (partial or complete) must be a prefix of
1448 bool ModelChecker::isfeasibleprefix() const
1450 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1454 * Print disagnostic information about an infeasible execution
1455 * @param prefix A string to prefix the output with; if NULL, then a default
1456 * message prefix will be provided
1458 void ModelChecker::print_infeasibility(const char *prefix) const
1462 if (mo_graph->checkForCycles())
1463 ptr += sprintf(ptr, "[mo cycle]");
1464 if (priv->failed_promise)
1465 ptr += sprintf(ptr, "[failed promise]");
1466 if (priv->too_many_reads)
1467 ptr += sprintf(ptr, "[too many reads]");
1468 if (priv->no_valid_reads)
1469 ptr += sprintf(ptr, "[no valid reads-from]");
1470 if (priv->bad_synchronization)
1471 ptr += sprintf(ptr, "[bad sw ordering]");
1472 if (promises_expired())
1473 ptr += sprintf(ptr, "[promise expired]");
1474 if (promises->size() != 0)
1475 ptr += sprintf(ptr, "[unresolved promise]");
1477 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1481 * Returns whether the current completed trace is feasible, except for pending
1482 * release sequences.
1484 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1486 return !is_infeasible() && promises->size() == 0;
1490 * Check if the current partial trace is infeasible. Does not check any
1491 * end-of-execution flags, which might rule out the execution. Thus, this is
1492 * useful only for ruling an execution as infeasible.
1493 * @return whether the current partial trace is infeasible.
1495 bool ModelChecker::is_infeasible() const
1497 return mo_graph->checkForCycles() ||
1498 priv->no_valid_reads ||
1499 priv->failed_promise ||
1500 priv->too_many_reads ||
1501 priv->bad_synchronization ||
1505 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1506 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1507 ModelAction *lastread = get_last_action(act->get_tid());
1508 lastread->process_rmw(act);
1509 if (act->is_rmw()) {
1510 if (lastread->get_reads_from())
1511 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1513 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1514 mo_graph->commitChanges();
1520 * Checks whether a thread has read from the same write for too many times
1521 * without seeing the effects of a later write.
1524 * 1) there must a different write that we could read from that would satisfy the modification order,
1525 * 2) we must have read from the same value in excess of maxreads times, and
1526 * 3) that other write must have been in the reads_from set for maxreads times.
1528 * If so, we decide that the execution is no longer feasible.
1530 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1532 if (params.maxreads != 0) {
1533 if (curr->get_node()->get_read_from_size() <= 1)
1535 //Must make sure that execution is currently feasible... We could
1536 //accidentally clear by rolling back
1537 if (is_infeasible())
1539 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1540 int tid = id_to_int(curr->get_tid());
1543 if ((int)thrd_lists->size() <= tid)
1545 action_list_t *list = &(*thrd_lists)[tid];
1547 action_list_t::reverse_iterator rit = list->rbegin();
1548 /* Skip past curr */
1549 for (; (*rit) != curr; rit++)
1551 /* go past curr now */
1554 action_list_t::reverse_iterator ritcopy = rit;
1555 //See if we have enough reads from the same value
1557 for (; count < params.maxreads; rit++, count++) {
1558 if (rit == list->rend())
1560 ModelAction *act = *rit;
1561 if (!act->is_read())
1564 if (act->get_reads_from() != rf)
1566 if (act->get_node()->get_read_from_size() <= 1)
1569 for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
1571 const ModelAction *write = curr->get_node()->get_read_from_at(i);
1573 /* Need a different write */
1577 /* Test to see whether this is a feasible write to read from */
1578 /** NOTE: all members of read-from set should be
1579 * feasible, so we no longer check it here **/
1583 bool feasiblewrite = true;
1584 //new we need to see if this write works for everyone
1586 for (int loop = count; loop > 0; loop--, rit++) {
1587 ModelAction *act = *rit;
1588 bool foundvalue = false;
1589 for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
1590 if (act->get_node()->get_read_from_at(j) == write) {
1596 feasiblewrite = false;
1600 if (feasiblewrite) {
1601 priv->too_many_reads = true;
1609 * Updates the mo_graph with the constraints imposed from the current
1612 * Basic idea is the following: Go through each other thread and find
1613 * the last action that happened before our read. Two cases:
1615 * (1) The action is a write => that write must either occur before
1616 * the write we read from or be the write we read from.
1618 * (2) The action is a read => the write that that action read from
1619 * must occur before the write we read from or be the same write.
1621 * @param curr The current action. Must be a read.
1622 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1623 * @return True if modification order edges were added; false otherwise
1625 template <typename rf_type>
1626 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1628 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1631 ASSERT(curr->is_read());
1633 /* Last SC fence in the current thread */
1634 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1636 /* Iterate over all threads */
1637 for (i = 0; i < thrd_lists->size(); i++) {
1638 /* Last SC fence in thread i */
1639 ModelAction *last_sc_fence_thread_local = NULL;
1640 if (int_to_id((int)i) != curr->get_tid())
1641 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1643 /* Last SC fence in thread i, before last SC fence in current thread */
1644 ModelAction *last_sc_fence_thread_before = NULL;
1645 if (last_sc_fence_local)
1646 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1648 /* Iterate over actions in thread, starting from most recent */
1649 action_list_t *list = &(*thrd_lists)[i];
1650 action_list_t::reverse_iterator rit;
1651 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1652 ModelAction *act = *rit;
1654 if (act->is_write() && !act->equals(rf) && act != curr) {
1655 /* C++, Section 29.3 statement 5 */
1656 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1657 *act < *last_sc_fence_thread_local) {
1658 added = mo_graph->addEdge(act, rf) || added;
1661 /* C++, Section 29.3 statement 4 */
1662 else if (act->is_seqcst() && last_sc_fence_local &&
1663 *act < *last_sc_fence_local) {
1664 added = mo_graph->addEdge(act, rf) || added;
1667 /* C++, Section 29.3 statement 6 */
1668 else if (last_sc_fence_thread_before &&
1669 *act < *last_sc_fence_thread_before) {
1670 added = mo_graph->addEdge(act, rf) || added;
1676 * Include at most one act per-thread that "happens
1677 * before" curr. Don't consider reflexively.
1679 if (act->happens_before(curr) && act != curr) {
1680 if (act->is_write()) {
1681 if (!act->equals(rf)) {
1682 added = mo_graph->addEdge(act, rf) || added;
1685 const ModelAction *prevreadfrom = act->get_reads_from();
1686 //if the previous read is unresolved, keep going...
1687 if (prevreadfrom == NULL)
1690 if (!prevreadfrom->equals(rf)) {
1691 added = mo_graph->addEdge(prevreadfrom, rf) || added;
1700 * All compatible, thread-exclusive promises must be ordered after any
1701 * concrete loads from the same thread
1703 for (unsigned int i = 0; i < promises->size(); i++)
1704 if ((*promises)[i]->is_compatible_exclusive(curr))
1705 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1711 * Updates the mo_graph with the constraints imposed from the current write.
1713 * Basic idea is the following: Go through each other thread and find
1714 * the lastest action that happened before our write. Two cases:
1716 * (1) The action is a write => that write must occur before
1719 * (2) The action is a read => the write that that action read from
1720 * must occur before the current write.
1722 * This method also handles two other issues:
1724 * (I) Sequential Consistency: Making sure that if the current write is
1725 * seq_cst, that it occurs after the previous seq_cst write.
1727 * (II) Sending the write back to non-synchronizing reads.
1729 * @param curr The current action. Must be a write.
1730 * @return True if modification order edges were added; false otherwise
1732 bool ModelChecker::w_modification_order(ModelAction *curr)
1734 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1737 ASSERT(curr->is_write());
1739 if (curr->is_seqcst()) {
1740 /* We have to at least see the last sequentially consistent write,
1741 so we are initialized. */
1742 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1743 if (last_seq_cst != NULL) {
1744 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1748 /* Last SC fence in the current thread */
1749 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1751 /* Iterate over all threads */
1752 for (i = 0; i < thrd_lists->size(); i++) {
1753 /* Last SC fence in thread i, before last SC fence in current thread */
1754 ModelAction *last_sc_fence_thread_before = NULL;
1755 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1756 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1758 /* Iterate over actions in thread, starting from most recent */
1759 action_list_t *list = &(*thrd_lists)[i];
1760 action_list_t::reverse_iterator rit;
1761 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1762 ModelAction *act = *rit;
1765 * 1) If RMW and it actually read from something, then we
1766 * already have all relevant edges, so just skip to next
1769 * 2) If RMW and it didn't read from anything, we should
1770 * whatever edge we can get to speed up convergence.
1772 * 3) If normal write, we need to look at earlier actions, so
1773 * continue processing list.
1775 if (curr->is_rmw()) {
1776 if (curr->get_reads_from() != NULL)
1784 /* C++, Section 29.3 statement 7 */
1785 if (last_sc_fence_thread_before && act->is_write() &&
1786 *act < *last_sc_fence_thread_before) {
1787 added = mo_graph->addEdge(act, curr) || added;
1792 * Include at most one act per-thread that "happens
1795 if (act->happens_before(curr)) {
1797 * Note: if act is RMW, just add edge:
1799 * The following edge should be handled elsewhere:
1800 * readfrom(act) --mo--> act
1802 if (act->is_write())
1803 added = mo_graph->addEdge(act, curr) || added;
1804 else if (act->is_read()) {
1805 //if previous read accessed a null, just keep going
1806 if (act->get_reads_from() == NULL)
1808 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1811 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1812 !act->same_thread(curr)) {
1813 /* We have an action that:
1814 (1) did not happen before us
1815 (2) is a read and we are a write
1816 (3) cannot synchronize with us
1817 (4) is in a different thread
1819 that read could potentially read from our write. Note that
1820 these checks are overly conservative at this point, we'll
1821 do more checks before actually removing the
1825 if (thin_air_constraint_may_allow(curr, act)) {
1826 if (!is_infeasible())
1827 futurevalues->push_back(PendingFutureValue(curr, act));
1828 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1829 add_future_value(curr, act);
1836 * All compatible, thread-exclusive promises must be ordered after any
1837 * concrete stores to the same thread, or else they can be merged with
1840 for (unsigned int i = 0; i < promises->size(); i++)
1841 if ((*promises)[i]->is_compatible_exclusive(curr))
1842 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1847 /** Arbitrary reads from the future are not allowed. Section 29.3
1848 * part 9 places some constraints. This method checks one result of constraint
1849 * constraint. Others require compiler support. */
1850 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1852 if (!writer->is_rmw())
1855 if (!reader->is_rmw())
1858 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1859 if (search == reader)
1861 if (search->get_tid() == reader->get_tid() &&
1862 search->happens_before(reader))
1870 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1871 * some constraints. This method checks one the following constraint (others
1872 * require compiler support):
1874 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1876 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1878 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1880 /* Iterate over all threads */
1881 for (i = 0; i < thrd_lists->size(); i++) {
1882 const ModelAction *write_after_read = NULL;
1884 /* Iterate over actions in thread, starting from most recent */
1885 action_list_t *list = &(*thrd_lists)[i];
1886 action_list_t::reverse_iterator rit;
1887 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1888 ModelAction *act = *rit;
1890 /* Don't disallow due to act == reader */
1891 if (!reader->happens_before(act) || reader == act)
1893 else if (act->is_write())
1894 write_after_read = act;
1895 else if (act->is_read() && act->get_reads_from() != NULL)
1896 write_after_read = act->get_reads_from();
1899 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1906 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1907 * The ModelAction under consideration is expected to be taking part in
1908 * release/acquire synchronization as an object of the "reads from" relation.
1909 * Note that this can only provide release sequence support for RMW chains
1910 * which do not read from the future, as those actions cannot be traced until
1911 * their "promise" is fulfilled. Similarly, we may not even establish the
1912 * presence of a release sequence with certainty, as some modification order
1913 * constraints may be decided further in the future. Thus, this function
1914 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1915 * and a boolean representing certainty.
1917 * @param rf The action that might be part of a release sequence. Must be a
1919 * @param release_heads A pass-by-reference style return parameter. After
1920 * execution of this function, release_heads will contain the heads of all the
1921 * relevant release sequences, if any exists with certainty
1922 * @param pending A pass-by-reference style return parameter which is only used
1923 * when returning false (i.e., uncertain). Returns most information regarding
1924 * an uncertain release sequence, including any write operations that might
1925 * break the sequence.
1926 * @return true, if the ModelChecker is certain that release_heads is complete;
1929 bool ModelChecker::release_seq_heads(const ModelAction *rf,
1930 rel_heads_list_t *release_heads,
1931 struct release_seq *pending) const
1933 /* Only check for release sequences if there are no cycles */
1934 if (mo_graph->checkForCycles())
1937 for ( ; rf != NULL; rf = rf->get_reads_from()) {
1938 ASSERT(rf->is_write());
1940 if (rf->is_release())
1941 release_heads->push_back(rf);
1942 else if (rf->get_last_fence_release())
1943 release_heads->push_back(rf->get_last_fence_release());
1945 break; /* End of RMW chain */
1947 /** @todo Need to be smarter here... In the linux lock
1948 * example, this will run to the beginning of the program for
1950 /** @todo The way to be smarter here is to keep going until 1
1951 * thread has a release preceded by an acquire and you've seen
1954 /* acq_rel RMW is a sufficient stopping condition */
1955 if (rf->is_acquire() && rf->is_release())
1956 return true; /* complete */
1959 /* read from future: need to settle this later */
1961 return false; /* incomplete */
1964 if (rf->is_release())
1965 return true; /* complete */
1967 /* else relaxed write
1968 * - check for fence-release in the same thread (29.8, stmt. 3)
1969 * - check modification order for contiguous subsequence
1970 * -> rf must be same thread as release */
1972 const ModelAction *fence_release = rf->get_last_fence_release();
1973 /* Synchronize with a fence-release unconditionally; we don't need to
1974 * find any more "contiguous subsequence..." for it */
1976 release_heads->push_back(fence_release);
1978 int tid = id_to_int(rf->get_tid());
1979 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
1980 action_list_t *list = &(*thrd_lists)[tid];
1981 action_list_t::const_reverse_iterator rit;
1983 /* Find rf in the thread list */
1984 rit = std::find(list->rbegin(), list->rend(), rf);
1985 ASSERT(rit != list->rend());
1987 /* Find the last {write,fence}-release */
1988 for (; rit != list->rend(); rit++) {
1989 if (fence_release && *(*rit) < *fence_release)
1991 if ((*rit)->is_release())
1994 if (rit == list->rend()) {
1995 /* No write-release in this thread */
1996 return true; /* complete */
1997 } else if (fence_release && *(*rit) < *fence_release) {
1998 /* The fence-release is more recent (and so, "stronger") than
1999 * the most recent write-release */
2000 return true; /* complete */
2001 } /* else, need to establish contiguous release sequence */
2002 ModelAction *release = *rit;
2004 ASSERT(rf->same_thread(release));
2006 pending->writes.clear();
2008 bool certain = true;
2009 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2010 if (id_to_int(rf->get_tid()) == (int)i)
2012 list = &(*thrd_lists)[i];
2014 /* Can we ensure no future writes from this thread may break
2015 * the release seq? */
2016 bool future_ordered = false;
2018 ModelAction *last = get_last_action(int_to_id(i));
2019 Thread *th = get_thread(int_to_id(i));
2020 if ((last && rf->happens_before(last)) ||
2023 future_ordered = true;
2025 ASSERT(!th->is_model_thread() || future_ordered);
2027 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2028 const ModelAction *act = *rit;
2029 /* Reach synchronization -> this thread is complete */
2030 if (act->happens_before(release))
2032 if (rf->happens_before(act)) {
2033 future_ordered = true;
2037 /* Only non-RMW writes can break release sequences */
2038 if (!act->is_write() || act->is_rmw())
2041 /* Check modification order */
2042 if (mo_graph->checkReachable(rf, act)) {
2043 /* rf --mo--> act */
2044 future_ordered = true;
2047 if (mo_graph->checkReachable(act, release))
2048 /* act --mo--> release */
2050 if (mo_graph->checkReachable(release, act) &&
2051 mo_graph->checkReachable(act, rf)) {
2052 /* release --mo-> act --mo--> rf */
2053 return true; /* complete */
2055 /* act may break release sequence */
2056 pending->writes.push_back(act);
2059 if (!future_ordered)
2060 certain = false; /* This thread is uncertain */
2064 release_heads->push_back(release);
2065 pending->writes.clear();
2067 pending->release = release;
2074 * An interface for getting the release sequence head(s) with which a
2075 * given ModelAction must synchronize. This function only returns a non-empty
2076 * result when it can locate a release sequence head with certainty. Otherwise,
2077 * it may mark the internal state of the ModelChecker so that it will handle
2078 * the release sequence at a later time, causing @a acquire to update its
2079 * synchronization at some later point in execution.
2081 * @param acquire The 'acquire' action that may synchronize with a release
2083 * @param read The read action that may read from a release sequence; this may
2084 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2085 * when 'acquire' is a fence-acquire)
2086 * @param release_heads A pass-by-reference return parameter. Will be filled
2087 * with the head(s) of the release sequence(s), if they exists with certainty.
2088 * @see ModelChecker::release_seq_heads
2090 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2091 ModelAction *read, rel_heads_list_t *release_heads)
2093 const ModelAction *rf = read->get_reads_from();
2094 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2095 sequence->acquire = acquire;
2096 sequence->read = read;
2098 if (!release_seq_heads(rf, release_heads, sequence)) {
2099 /* add act to 'lazy checking' list */
2100 pending_rel_seqs->push_back(sequence);
2102 snapshot_free(sequence);
2107 * Attempt to resolve all stashed operations that might synchronize with a
2108 * release sequence for a given location. This implements the "lazy" portion of
2109 * determining whether or not a release sequence was contiguous, since not all
2110 * modification order information is present at the time an action occurs.
2112 * @param location The location/object that should be checked for release
2113 * sequence resolutions. A NULL value means to check all locations.
2114 * @param work_queue The work queue to which to add work items as they are
2116 * @return True if any updates occurred (new synchronization, new mo_graph
2119 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2121 bool updated = false;
2122 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2123 while (it != pending_rel_seqs->end()) {
2124 struct release_seq *pending = *it;
2125 ModelAction *acquire = pending->acquire;
2126 const ModelAction *read = pending->read;
2128 /* Only resolve sequences on the given location, if provided */
2129 if (location && read->get_location() != location) {
2134 const ModelAction *rf = read->get_reads_from();
2135 rel_heads_list_t release_heads;
2137 complete = release_seq_heads(rf, &release_heads, pending);
2138 for (unsigned int i = 0; i < release_heads.size(); i++) {
2139 if (!acquire->has_synchronized_with(release_heads[i])) {
2140 if (acquire->synchronize_with(release_heads[i]))
2143 set_bad_synchronization();
2148 /* Re-check all pending release sequences */
2149 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2150 /* Re-check read-acquire for mo_graph edges */
2151 if (acquire->is_read())
2152 work_queue->push_back(MOEdgeWorkEntry(acquire));
2154 /* propagate synchronization to later actions */
2155 action_list_t::reverse_iterator rit = action_trace->rbegin();
2156 for (; (*rit) != acquire; rit++) {
2157 ModelAction *propagate = *rit;
2158 if (acquire->happens_before(propagate)) {
2159 propagate->synchronize_with(acquire);
2160 /* Re-check 'propagate' for mo_graph edges */
2161 work_queue->push_back(MOEdgeWorkEntry(propagate));
2166 it = pending_rel_seqs->erase(it);
2167 snapshot_free(pending);
2173 // If we resolved promises or data races, see if we have realized a data race.
2180 * Performs various bookkeeping operations for the current ModelAction. For
2181 * instance, adds action to the per-object, per-thread action vector and to the
2182 * action trace list of all thread actions.
2184 * @param act is the ModelAction to add.
2186 void ModelChecker::add_action_to_lists(ModelAction *act)
2188 int tid = id_to_int(act->get_tid());
2189 ModelAction *uninit = NULL;
2191 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2192 if (list->empty() && act->is_atomic_var()) {
2193 uninit = new_uninitialized_action(act->get_location());
2194 uninit_id = id_to_int(uninit->get_tid());
2195 list->push_back(uninit);
2197 list->push_back(act);
2199 action_trace->push_back(act);
2201 action_trace->push_front(uninit);
2203 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2204 if (tid >= (int)vec->size())
2205 vec->resize(priv->next_thread_id);
2206 (*vec)[tid].push_back(act);
2208 (*vec)[uninit_id].push_front(uninit);
2210 if ((int)thrd_last_action->size() <= tid)
2211 thrd_last_action->resize(get_num_threads());
2212 (*thrd_last_action)[tid] = act;
2214 (*thrd_last_action)[uninit_id] = uninit;
2216 if (act->is_fence() && act->is_release()) {
2217 if ((int)thrd_last_fence_release->size() <= tid)
2218 thrd_last_fence_release->resize(get_num_threads());
2219 (*thrd_last_fence_release)[tid] = act;
2222 if (act->is_wait()) {
2223 void *mutex_loc = (void *) act->get_value();
2224 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2226 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2227 if (tid >= (int)vec->size())
2228 vec->resize(priv->next_thread_id);
2229 (*vec)[tid].push_back(act);
2234 * @brief Get the last action performed by a particular Thread
2235 * @param tid The thread ID of the Thread in question
2236 * @return The last action in the thread
2238 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2240 int threadid = id_to_int(tid);
2241 if (threadid < (int)thrd_last_action->size())
2242 return (*thrd_last_action)[id_to_int(tid)];
2248 * @brief Get the last fence release performed by a particular Thread
2249 * @param tid The thread ID of the Thread in question
2250 * @return The last fence release in the thread, if one exists; NULL otherwise
2252 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2254 int threadid = id_to_int(tid);
2255 if (threadid < (int)thrd_last_fence_release->size())
2256 return (*thrd_last_fence_release)[id_to_int(tid)];
2262 * Gets the last memory_order_seq_cst write (in the total global sequence)
2263 * performed on a particular object (i.e., memory location), not including the
2265 * @param curr The current ModelAction; also denotes the object location to
2267 * @return The last seq_cst write
2269 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2271 void *location = curr->get_location();
2272 action_list_t *list = get_safe_ptr_action(obj_map, location);
2273 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2274 action_list_t::reverse_iterator rit;
2275 for (rit = list->rbegin(); rit != list->rend(); rit++)
2276 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2282 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2283 * performed in a particular thread, prior to a particular fence.
2284 * @param tid The ID of the thread to check
2285 * @param before_fence The fence from which to begin the search; if NULL, then
2286 * search for the most recent fence in the thread.
2287 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2289 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2291 /* All fences should have NULL location */
2292 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2293 action_list_t::reverse_iterator rit = list->rbegin();
2296 for (; rit != list->rend(); rit++)
2297 if (*rit == before_fence)
2300 ASSERT(*rit == before_fence);
2304 for (; rit != list->rend(); rit++)
2305 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2311 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2312 * location). This function identifies the mutex according to the current
2313 * action, which is presumed to perform on the same mutex.
2314 * @param curr The current ModelAction; also denotes the object location to
2316 * @return The last unlock operation
2318 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2320 void *location = curr->get_location();
2321 action_list_t *list = get_safe_ptr_action(obj_map, location);
2322 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2323 action_list_t::reverse_iterator rit;
2324 for (rit = list->rbegin(); rit != list->rend(); rit++)
2325 if ((*rit)->is_unlock() || (*rit)->is_wait())
2330 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2332 ModelAction *parent = get_last_action(tid);
2334 parent = get_thread(tid)->get_creation();
2339 * Returns the clock vector for a given thread.
2340 * @param tid The thread whose clock vector we want
2341 * @return Desired clock vector
2343 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2345 return get_parent_action(tid)->get_cv();
2349 * Resolve a set of Promises with a current write. The set is provided in the
2350 * Node corresponding to @a write.
2351 * @param write The ModelAction that is fulfilling Promises
2352 * @return True if promises were resolved; false otherwise
2354 bool ModelChecker::resolve_promises(ModelAction *write)
2356 bool haveResolved = false;
2357 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2358 promise_list_t mustResolve, resolved;
2360 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2361 Promise *promise = (*promises)[promise_index];
2362 if (write->get_node()->get_promise(i)) {
2363 ModelAction *read = promise->get_action();
2364 read_from(read, write);
2365 //Make sure the promise's value matches the write's value
2366 ASSERT(promise->is_compatible(write));
2367 mo_graph->resolvePromise(read, write, &mustResolve);
2369 resolved.push_back(promise);
2370 promises->erase(promises->begin() + promise_index);
2371 actions_to_check.push_back(read);
2373 haveResolved = true;
2378 for (unsigned int i = 0; i < mustResolve.size(); i++) {
2379 if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
2381 priv->failed_promise = true;
2383 for (unsigned int i = 0; i < resolved.size(); i++)
2385 //Check whether reading these writes has made threads unable to
2388 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2389 ModelAction *read = actions_to_check[i];
2390 mo_check_promises(read, true);
2393 return haveResolved;
2397 * Compute the set of promises that could potentially be satisfied by this
2398 * action. Note that the set computation actually appears in the Node, not in
2400 * @param curr The ModelAction that may satisfy promises
2402 void ModelChecker::compute_promises(ModelAction *curr)
2404 for (unsigned int i = 0; i < promises->size(); i++) {
2405 Promise *promise = (*promises)[i];
2406 const ModelAction *act = promise->get_action();
2407 if (!act->happens_before(curr) &&
2409 !act->could_synchronize_with(curr) &&
2410 !act->same_thread(curr) &&
2411 act->get_location() == curr->get_location() &&
2412 promise->get_value() == curr->get_value()) {
2413 curr->get_node()->set_promise(i, act->is_rmw());
2418 /** Checks promises in response to change in ClockVector Threads. */
2419 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2421 for (unsigned int i = 0; i < promises->size(); i++) {
2422 Promise *promise = (*promises)[i];
2423 const ModelAction *act = promise->get_action();
2424 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2425 merge_cv->synchronized_since(act)) {
2426 if (promise->eliminate_thread(tid)) {
2427 //Promise has failed
2428 priv->failed_promise = true;
2435 void ModelChecker::check_promises_thread_disabled()
2437 for (unsigned int i = 0; i < promises->size(); i++) {
2438 Promise *promise = (*promises)[i];
2439 if (promise->has_failed()) {
2440 priv->failed_promise = true;
2447 * @brief Checks promises in response to addition to modification order for
2450 * We test whether threads are still available for satisfying promises after an
2451 * addition to our modification order constraints. Those that are unavailable
2452 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2453 * that promise has failed.
2455 * @param act The ModelAction which updated the modification order
2456 * @param is_read_check Should be true if act is a read and we must check for
2457 * updates to the store from which it read (there is a distinction here for
2458 * RMW's, which are both a load and a store)
2460 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2462 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2464 for (unsigned int i = 0; i < promises->size(); i++) {
2465 Promise *promise = (*promises)[i];
2466 const ModelAction *pread = promise->get_action();
2468 // Is this promise on the same location?
2469 if (!pread->same_var(write))
2472 if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
2473 priv->failed_promise = true;
2477 // Don't do any lookups twice for the same thread
2478 if (!promise->thread_is_available(act->get_tid()))
2481 if (mo_graph->checkReachable(promise, write)) {
2482 if (mo_graph->checkPromise(write, promise)) {
2483 priv->failed_promise = true;
2491 * Compute the set of writes that may break the current pending release
2492 * sequence. This information is extracted from previou release sequence
2495 * @param curr The current ModelAction. Must be a release sequence fixup
2498 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2500 if (pending_rel_seqs->empty())
2503 struct release_seq *pending = pending_rel_seqs->back();
2504 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2505 const ModelAction *write = pending->writes[i];
2506 curr->get_node()->add_relseq_break(write);
2509 /* NULL means don't break the sequence; just synchronize */
2510 curr->get_node()->add_relseq_break(NULL);
2514 * Build up an initial set of all past writes that this 'read' action may read
2515 * from. This set is determined by the clock vector's "happens before"
2517 * @param curr is the current ModelAction that we are exploring; it must be a
2520 void ModelChecker::build_reads_from_past(ModelAction *curr)
2522 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2524 ASSERT(curr->is_read());
2526 ModelAction *last_sc_write = NULL;
2528 if (curr->is_seqcst())
2529 last_sc_write = get_last_seq_cst_write(curr);
2531 /* Iterate over all threads */
2532 for (i = 0; i < thrd_lists->size(); i++) {
2533 /* Iterate over actions in thread, starting from most recent */
2534 action_list_t *list = &(*thrd_lists)[i];
2535 action_list_t::reverse_iterator rit;
2536 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2537 ModelAction *act = *rit;
2539 /* Only consider 'write' actions */
2540 if (!act->is_write() || act == curr)
2543 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2544 bool allow_read = true;
2546 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2548 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2552 /* Only add feasible reads */
2553 mo_graph->startChanges();
2554 r_modification_order(curr, act);
2555 if (!is_infeasible())
2556 curr->get_node()->add_read_from(act);
2557 mo_graph->rollbackChanges();
2560 /* Include at most one act per-thread that "happens before" curr */
2561 if (act->happens_before(curr))
2565 /* We may find no valid may-read-from only if the execution is doomed */
2566 if (!curr->get_node()->get_read_from_size()) {
2567 priv->no_valid_reads = true;
2571 if (DBG_ENABLED()) {
2572 model_print("Reached read action:\n");
2574 model_print("Printing may_read_from\n");
2575 curr->get_node()->print_may_read_from();
2576 model_print("End printing may_read_from\n");
2580 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2582 for ( ; write != NULL; write = write->get_reads_from()) {
2583 /* UNINIT actions don't have a Node, and they never sleep */
2584 if (write->is_uninitialized())
2586 Node *prevnode = write->get_node()->get_parent();
2588 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2589 if (write->is_release() && thread_sleep)
2591 if (!write->is_rmw())
2598 * @brief Create a new action representing an uninitialized atomic
2599 * @param location The memory location of the atomic object
2600 * @return A pointer to a new ModelAction
2602 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2604 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2605 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2606 act->create_cv(NULL);
2610 static void print_list(action_list_t *list)
2612 action_list_t::iterator it;
2614 model_print("---------------------------------------------------------------------\n");
2616 unsigned int hash = 0;
2618 for (it = list->begin(); it != list->end(); it++) {
2620 hash = hash^(hash<<3)^((*it)->hash());
2622 model_print("HASH %u\n", hash);
2623 model_print("---------------------------------------------------------------------\n");
2626 #if SUPPORT_MOD_ORDER_DUMP
2627 void ModelChecker::dumpGraph(char *filename) const
2630 sprintf(buffer, "%s.dot", filename);
2631 FILE *file = fopen(buffer, "w");
2632 fprintf(file, "digraph %s {\n", filename);
2633 mo_graph->dumpNodes(file);
2634 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2636 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2637 ModelAction *action = *it;
2638 if (action->is_read()) {
2639 fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2640 if (action->get_reads_from() != NULL)
2641 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2643 if (thread_array[action->get_tid()] != NULL) {
2644 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2647 thread_array[action->get_tid()] = action;
2649 fprintf(file, "}\n");
2650 model_free(thread_array);
2655 /** @brief Prints an execution trace summary. */
2656 void ModelChecker::print_summary() const
2658 #if SUPPORT_MOD_ORDER_DUMP
2659 char buffername[100];
2660 sprintf(buffername, "exec%04u", stats.num_total);
2661 mo_graph->dumpGraphToFile(buffername);
2662 sprintf(buffername, "graph%04u", stats.num_total);
2663 dumpGraph(buffername);
2666 model_print("Execution %d:", stats.num_total);
2667 if (isfeasibleprefix())
2670 print_infeasibility(" INFEASIBLE");
2671 print_list(action_trace);
2676 * Add a Thread to the system for the first time. Should only be called once
2678 * @param t The Thread to add
2680 void ModelChecker::add_thread(Thread *t)
2682 thread_map->put(id_to_int(t->get_id()), t);
2683 scheduler->add_thread(t);
2687 * Removes a thread from the scheduler.
2688 * @param the thread to remove.
2690 void ModelChecker::remove_thread(Thread *t)
2692 scheduler->remove_thread(t);
2696 * @brief Get a Thread reference by its ID
2697 * @param tid The Thread's ID
2698 * @return A Thread reference
2700 Thread * ModelChecker::get_thread(thread_id_t tid) const
2702 return thread_map->get(id_to_int(tid));
2706 * @brief Get a reference to the Thread in which a ModelAction was executed
2707 * @param act The ModelAction
2708 * @return A Thread reference
2710 Thread * ModelChecker::get_thread(const ModelAction *act) const
2712 return get_thread(act->get_tid());
2716 * @brief Check if a Thread is currently enabled
2717 * @param t The Thread to check
2718 * @return True if the Thread is currently enabled
2720 bool ModelChecker::is_enabled(Thread *t) const
2722 return scheduler->is_enabled(t);
2726 * @brief Check if a Thread is currently enabled
2727 * @param tid The ID of the Thread to check
2728 * @return True if the Thread is currently enabled
2730 bool ModelChecker::is_enabled(thread_id_t tid) const
2732 return scheduler->is_enabled(tid);
2736 * Switch from a model-checker context to a user-thread context. This is the
2737 * complement of ModelChecker::switch_to_master and must be called from the
2738 * model-checker context
2740 * @param thread The user-thread to switch to
2742 void ModelChecker::switch_from_master(Thread *thread)
2744 scheduler->set_current_thread(thread);
2745 Thread::swap(&system_context, thread);
2749 * Switch from a user-context to the "master thread" context (a.k.a. system
2750 * context). This switch is made with the intention of exploring a particular
2751 * model-checking action (described by a ModelAction object). Must be called
2752 * from a user-thread context.
2754 * @param act The current action that will be explored. May be NULL only if
2755 * trace is exiting via an assertion (see ModelChecker::set_assert and
2756 * ModelChecker::has_asserted).
2757 * @return Return the value returned by the current action
2759 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2762 Thread *old = thread_current();
2763 ASSERT(!old->get_pending());
2764 old->set_pending(act);
2765 if (Thread::swap(old, &system_context) < 0) {
2766 perror("swap threads");
2769 return old->get_return_value();
2773 * Takes the next step in the execution, if possible.
2774 * @param curr The current step to take
2775 * @return Returns the next Thread to run, if any; NULL if this execution
2778 Thread * ModelChecker::take_step(ModelAction *curr)
2780 Thread *curr_thrd = get_thread(curr);
2781 ASSERT(curr_thrd->get_state() == THREAD_READY);
2783 curr = check_current_action(curr);
2785 /* Infeasible -> don't take any more steps */
2786 if (is_infeasible())
2788 else if (isfeasibleprefix() && have_bug_reports()) {
2793 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2796 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2797 scheduler->remove_thread(curr_thrd);
2799 Thread *next_thrd = get_next_thread(curr);
2801 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2802 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2807 /** Wrapper to run the user's main function, with appropriate arguments */
2808 void user_main_wrapper(void *)
2810 user_main(model->params.argc, model->params.argv);
2813 /** @brief Run ModelChecker for the user program */
2814 void ModelChecker::run()
2818 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
2823 * Stash next pending action(s) for thread(s). There
2824 * should only need to stash one thread's action--the
2825 * thread which just took a step--plus the first step
2826 * for any newly-created thread
2828 for (unsigned int i = 0; i < get_num_threads(); i++) {
2829 thread_id_t tid = int_to_id(i);
2830 Thread *thr = get_thread(tid);
2831 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
2832 switch_from_master(thr);
2836 /* Catch assertions from prior take_step or from
2837 * between-ModelAction bugs (e.g., data races) */
2841 /* Consume the next action for a Thread */
2842 ModelAction *curr = t->get_pending();
2843 t->set_pending(NULL);
2844 t = take_step(curr);
2845 } while (t && !t->is_model_thread());
2848 * Launch end-of-execution release sequence fixups only when
2849 * the execution is otherwise feasible AND there are:
2851 * (1) pending release sequences
2852 * (2) pending assertions that could be invalidated by a change
2853 * in clock vectors (i.e., data races)
2854 * (3) no pending promises
2856 while (!pending_rel_seqs->empty() &&
2857 is_feasible_prefix_ignore_relseq() &&
2858 !unrealizedraces.empty()) {
2859 model_print("*** WARNING: release sequence fixup action "
2860 "(%zu pending release seuqence(s)) ***\n",
2861 pending_rel_seqs->size());
2862 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2863 std::memory_order_seq_cst, NULL, VALUE_NONE,
2867 } while (next_execution());
2869 model_print("******* Model-checking complete: *******\n");