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_relseq_break()) {
267 /* The next node will try to resolve a release sequence differently */
268 tid = next->get_tid();
269 node_stack->pop_restofstack(2);
272 /* Make a different thread execute for next step */
273 scheduler->add_sleep(get_thread(next->get_tid()));
274 tid = prevnode->get_next_backtrack();
275 /* Make sure the backtracked thread isn't sleeping. */
276 node_stack->pop_restofstack(1);
277 if (diverge == earliest_diverge) {
278 earliest_diverge = prevnode->get_action();
281 /* Start the round robin scheduler from this thread id */
282 scheduler->set_scheduler_thread(tid);
283 /* The correct sleep set is in the parent node. */
286 DEBUG("*** Divergence point ***\n");
290 tid = next->get_tid();
292 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
293 ASSERT(tid != THREAD_ID_T_NONE);
294 return thread_map->get(id_to_int(tid));
298 * We need to know what the next actions of all threads in the sleep
299 * set will be. This method computes them and stores the actions at
300 * the corresponding thread object's pending action.
303 void ModelChecker::execute_sleep_set()
305 for (unsigned int i = 0; i < get_num_threads(); i++) {
306 thread_id_t tid = int_to_id(i);
307 Thread *thr = get_thread(tid);
308 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
309 thr->get_pending()->set_sleep_flag();
315 * @brief Should the current action wake up a given thread?
317 * @param curr The current action
318 * @param thread The thread that we might wake up
319 * @return True, if we should wake up the sleeping thread; false otherwise
321 bool ModelChecker::should_wake_up(const ModelAction *curr, const Thread *thread) const
323 const ModelAction *asleep = thread->get_pending();
324 /* Don't allow partial RMW to wake anyone up */
327 /* Synchronizing actions may have been backtracked */
328 if (asleep->could_synchronize_with(curr))
330 /* All acquire/release fences and fence-acquire/store-release */
331 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
333 /* Fence-release + store can awake load-acquire on the same location */
334 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
335 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
336 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
342 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
344 for (unsigned int i = 0; i < get_num_threads(); i++) {
345 Thread *thr = get_thread(int_to_id(i));
346 if (scheduler->is_sleep_set(thr)) {
347 if (should_wake_up(curr, thr))
348 /* Remove this thread from sleep set */
349 scheduler->remove_sleep(thr);
354 /** @brief Alert the model-checker that an incorrectly-ordered
355 * synchronization was made */
356 void ModelChecker::set_bad_synchronization()
358 priv->bad_synchronization = true;
362 * Check whether the current trace has triggered an assertion which should halt
365 * @return True, if the execution should be aborted; false otherwise
367 bool ModelChecker::has_asserted() const
369 return priv->asserted;
373 * Trigger a trace assertion which should cause this execution to be halted.
374 * This can be due to a detected bug or due to an infeasibility that should
377 void ModelChecker::set_assert()
379 priv->asserted = true;
383 * Check if we are in a deadlock. Should only be called at the end of an
384 * execution, although it should not give false positives in the middle of an
385 * execution (there should be some ENABLED thread).
387 * @return True if program is in a deadlock; false otherwise
389 bool ModelChecker::is_deadlocked() const
391 bool blocking_threads = false;
392 for (unsigned int i = 0; i < get_num_threads(); i++) {
393 thread_id_t tid = int_to_id(i);
396 Thread *t = get_thread(tid);
397 if (!t->is_model_thread() && t->get_pending())
398 blocking_threads = true;
400 return blocking_threads;
404 * Check if this is a complete execution. That is, have all thread completed
405 * execution (rather than exiting because sleep sets have forced a redundant
408 * @return True if the execution is complete.
410 bool ModelChecker::is_complete_execution() const
412 for (unsigned int i = 0; i < get_num_threads(); i++)
413 if (is_enabled(int_to_id(i)))
419 * @brief Assert a bug in the executing program.
421 * Use this function to assert any sort of bug in the user program. If the
422 * current trace is feasible (actually, a prefix of some feasible execution),
423 * then this execution will be aborted, printing the appropriate message. If
424 * the current trace is not yet feasible, the error message will be stashed and
425 * printed if the execution ever becomes feasible.
427 * @param msg Descriptive message for the bug (do not include newline char)
428 * @return True if bug is immediately-feasible
430 bool ModelChecker::assert_bug(const char *msg)
432 priv->bugs.push_back(new bug_message(msg));
434 if (isfeasibleprefix()) {
442 * @brief Assert a bug in the executing program, asserted by a user thread
443 * @see ModelChecker::assert_bug
444 * @param msg Descriptive message for the bug (do not include newline char)
446 void ModelChecker::assert_user_bug(const char *msg)
448 /* If feasible bug, bail out now */
450 switch_to_master(NULL);
453 /** @return True, if any bugs have been reported for this execution */
454 bool ModelChecker::have_bug_reports() const
456 return priv->bugs.size() != 0;
459 /** @brief Print bug report listing for this execution (if any bugs exist) */
460 void ModelChecker::print_bugs() const
462 if (have_bug_reports()) {
463 model_print("Bug report: %zu bug%s detected\n",
465 priv->bugs.size() > 1 ? "s" : "");
466 for (unsigned int i = 0; i < priv->bugs.size(); i++)
467 priv->bugs[i]->print();
472 * @brief Record end-of-execution stats
474 * Must be run when exiting an execution. Records various stats.
475 * @see struct execution_stats
477 void ModelChecker::record_stats()
480 if (!isfeasibleprefix())
481 stats.num_infeasible++;
482 else if (have_bug_reports())
483 stats.num_buggy_executions++;
484 else if (is_complete_execution())
485 stats.num_complete++;
487 stats.num_redundant++;
490 /** @brief Print execution stats */
491 void ModelChecker::print_stats() const
493 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
494 model_print("Number of redundant executions: %d\n", stats.num_redundant);
495 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
496 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
497 model_print("Total executions: %d\n", stats.num_total);
498 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
502 * @brief End-of-exeuction print
503 * @param printbugs Should any existing bugs be printed?
505 void ModelChecker::print_execution(bool printbugs) const
507 print_program_output();
509 if (DBG_ENABLED() || params.verbose) {
510 model_print("Earliest divergence point since last feasible execution:\n");
511 if (earliest_diverge)
512 earliest_diverge->print();
514 model_print("(Not set)\n");
520 /* Don't print invalid bugs */
529 * Queries the model-checker for more executions to explore and, if one
530 * exists, resets the model-checker state to execute a new execution.
532 * @return If there are more executions to explore, return true. Otherwise,
535 bool ModelChecker::next_execution()
538 /* Is this execution a feasible execution that's worth bug-checking? */
539 bool complete = isfeasibleprefix() && (is_complete_execution() ||
542 /* End-of-execution bug checks */
545 assert_bug("Deadlock detected");
553 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
554 print_execution(complete);
556 clear_program_output();
559 earliest_diverge = NULL;
561 if ((diverge = get_next_backtrack()) == NULL)
565 model_print("Next execution will diverge at:\n");
569 reset_to_initial_state();
574 * @brief Find the last fence-related backtracking conflict for a ModelAction
576 * This function performs the search for the most recent conflicting action
577 * against which we should perform backtracking, as affected by fence
578 * operations. This includes pairs of potentially-synchronizing actions which
579 * occur due to fence-acquire or fence-release, and hence should be explored in
580 * the opposite execution order.
582 * @param act The current action
583 * @return The most recent action which conflicts with act due to fences
585 ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const
587 /* Only perform release/acquire fence backtracking for stores */
588 if (!act->is_write())
591 /* Find a fence-release (or, act is a release) */
592 ModelAction *last_release;
593 if (act->is_release())
596 last_release = get_last_fence_release(act->get_tid());
600 /* Skip past the release */
601 action_list_t *list = action_trace;
602 action_list_t::reverse_iterator rit;
603 for (rit = list->rbegin(); rit != list->rend(); rit++)
604 if (*rit == last_release)
606 ASSERT(rit != list->rend());
611 * load --sb-> fence-acquire */
612 std::vector< ModelAction *, ModelAlloc<ModelAction *> > acquire_fences(get_num_threads(), NULL);
613 std::vector< ModelAction *, ModelAlloc<ModelAction *> > prior_loads(get_num_threads(), NULL);
614 bool found_acquire_fences = false;
615 for ( ; rit != list->rend(); rit++) {
616 ModelAction *prev = *rit;
617 if (act->same_thread(prev))
620 int tid = id_to_int(prev->get_tid());
622 if (prev->is_read() && act->same_var(prev)) {
623 if (prev->is_acquire()) {
624 /* Found most recent load-acquire, don't need
625 * to search for more fences */
626 if (!found_acquire_fences)
629 prior_loads[tid] = prev;
632 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
633 found_acquire_fences = true;
634 acquire_fences[tid] = prev;
638 ModelAction *latest_backtrack = NULL;
639 for (unsigned int i = 0; i < acquire_fences.size(); i++)
640 if (acquire_fences[i] && prior_loads[i])
641 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
642 latest_backtrack = acquire_fences[i];
643 return latest_backtrack;
647 * @brief Find the last backtracking conflict for a ModelAction
649 * This function performs the search for the most recent conflicting action
650 * against which we should perform backtracking. This primary includes pairs of
651 * synchronizing actions which should be explored in the opposite execution
654 * @param act The current action
655 * @return The most recent action which conflicts with act
657 ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const
659 switch (act->get_type()) {
660 /* case ATOMIC_FENCE: fences don't directly cause backtracking */
664 ModelAction *ret = NULL;
666 /* linear search: from most recent to oldest */
667 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
668 action_list_t::reverse_iterator rit;
669 for (rit = list->rbegin(); rit != list->rend(); rit++) {
670 ModelAction *prev = *rit;
671 if (prev->could_synchronize_with(act)) {
677 ModelAction *ret2 = get_last_fence_conflict(act);
687 case ATOMIC_TRYLOCK: {
688 /* linear search: from most recent to oldest */
689 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
690 action_list_t::reverse_iterator rit;
691 for (rit = list->rbegin(); rit != list->rend(); rit++) {
692 ModelAction *prev = *rit;
693 if (act->is_conflicting_lock(prev))
698 case ATOMIC_UNLOCK: {
699 /* linear search: from most recent to oldest */
700 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
701 action_list_t::reverse_iterator rit;
702 for (rit = list->rbegin(); rit != list->rend(); rit++) {
703 ModelAction *prev = *rit;
704 if (!act->same_thread(prev) && prev->is_failed_trylock())
710 /* linear search: from most recent to oldest */
711 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
712 action_list_t::reverse_iterator rit;
713 for (rit = list->rbegin(); rit != list->rend(); rit++) {
714 ModelAction *prev = *rit;
715 if (!act->same_thread(prev) && prev->is_failed_trylock())
717 if (!act->same_thread(prev) && prev->is_notify())
723 case ATOMIC_NOTIFY_ALL:
724 case ATOMIC_NOTIFY_ONE: {
725 /* linear search: from most recent to oldest */
726 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
727 action_list_t::reverse_iterator rit;
728 for (rit = list->rbegin(); rit != list->rend(); rit++) {
729 ModelAction *prev = *rit;
730 if (!act->same_thread(prev) && prev->is_wait())
741 /** This method finds backtracking points where we should try to
742 * reorder the parameter ModelAction against.
744 * @param the ModelAction to find backtracking points for.
746 void ModelChecker::set_backtracking(ModelAction *act)
748 Thread *t = get_thread(act);
749 ModelAction *prev = get_last_conflict(act);
753 Node *node = prev->get_node()->get_parent();
755 int low_tid, high_tid;
756 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
757 low_tid = id_to_int(act->get_tid());
758 high_tid = low_tid + 1;
761 high_tid = get_num_threads();
764 for (int i = low_tid; i < high_tid; i++) {
765 thread_id_t tid = int_to_id(i);
767 /* Make sure this thread can be enabled here. */
768 if (i >= node->get_num_threads())
771 /* Don't backtrack into a point where the thread is disabled or sleeping. */
772 if (node->enabled_status(tid) != THREAD_ENABLED)
775 /* Check if this has been explored already */
776 if (node->has_been_explored(tid))
779 /* See if fairness allows */
780 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
782 for (int t = 0; t < node->get_num_threads(); t++) {
783 thread_id_t tother = int_to_id(t);
784 if (node->is_enabled(tother) && node->has_priority(tother)) {
792 /* Cache the latest backtracking point */
793 set_latest_backtrack(prev);
795 /* If this is a new backtracking point, mark the tree */
796 if (!node->set_backtrack(tid))
798 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
799 id_to_int(prev->get_tid()),
800 id_to_int(t->get_id()));
809 * @brief Cache the a backtracking point as the "most recent", if eligible
811 * Note that this does not prepare the NodeStack for this backtracking
812 * operation, it only caches the action on a per-execution basis
814 * @param act The operation at which we should explore a different next action
815 * (i.e., backtracking point)
816 * @return True, if this action is now the most recent backtracking point;
819 bool ModelChecker::set_latest_backtrack(ModelAction *act)
821 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
822 priv->next_backtrack = act;
829 * Returns last backtracking point. The model checker will explore a different
830 * path for this point in the next execution.
831 * @return The ModelAction at which the next execution should diverge.
833 ModelAction * ModelChecker::get_next_backtrack()
835 ModelAction *next = priv->next_backtrack;
836 priv->next_backtrack = NULL;
841 * Processes a read model action.
842 * @param curr is the read model action to process.
843 * @return True if processing this read updates the mo_graph.
845 bool ModelChecker::process_read(ModelAction *curr)
847 Node *node = curr->get_node();
848 uint64_t value = VALUE_NONE;
849 bool updated = false;
851 switch (node->get_read_from_status()) {
852 case READ_FROM_PAST: {
853 const ModelAction *rf = node->get_read_from_past();
856 mo_graph->startChanges();
857 value = rf->get_value();
858 check_recency(curr, rf);
859 bool r_status = r_modification_order(curr, rf);
861 if (is_infeasible() && node->increment_read_from()) {
862 mo_graph->rollbackChanges();
863 priv->too_many_reads = false;
868 mo_graph->commitChanges();
869 mo_check_promises(curr, true);
874 case READ_FROM_FUTURE: {
875 /* Read from future value */
876 struct future_value fv = node->get_future_value();
877 Promise *promise = new Promise(curr, fv);
879 curr->set_read_from_promise(promise);
880 promises->push_back(promise);
881 mo_graph->startChanges();
882 updated = r_modification_order(curr, promise);
883 mo_graph->commitChanges();
889 get_thread(curr)->set_return_value(value);
895 * Processes a lock, trylock, or unlock model action. @param curr is
896 * the read model action to process.
898 * The try lock operation checks whether the lock is taken. If not,
899 * it falls to the normal lock operation case. If so, it returns
902 * The lock operation has already been checked that it is enabled, so
903 * it just grabs the lock and synchronizes with the previous unlock.
905 * The unlock operation has to re-enable all of the threads that are
906 * waiting on the lock.
908 * @return True if synchronization was updated; false otherwise
910 bool ModelChecker::process_mutex(ModelAction *curr)
912 std::mutex *mutex = NULL;
913 struct std::mutex_state *state = NULL;
915 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
916 mutex = (std::mutex *)curr->get_location();
917 state = mutex->get_state();
918 } else if (curr->is_wait()) {
919 mutex = (std::mutex *)curr->get_value();
920 state = mutex->get_state();
923 switch (curr->get_type()) {
924 case ATOMIC_TRYLOCK: {
925 bool success = !state->islocked;
926 curr->set_try_lock(success);
928 get_thread(curr)->set_return_value(0);
931 get_thread(curr)->set_return_value(1);
933 //otherwise fall into the lock case
935 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
936 assert_bug("Lock access before initialization");
937 state->islocked = true;
938 ModelAction *unlock = get_last_unlock(curr);
939 //synchronize with the previous unlock statement
940 if (unlock != NULL) {
941 curr->synchronize_with(unlock);
946 case ATOMIC_UNLOCK: {
948 state->islocked = false;
949 //wake up the other threads
950 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
951 //activate all the waiting threads
952 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
953 scheduler->wake(get_thread(*rit));
960 state->islocked = false;
961 //wake up the other threads
962 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
963 //activate all the waiting threads
964 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
965 scheduler->wake(get_thread(*rit));
968 //check whether we should go to sleep or not...simulate spurious failures
969 if (curr->get_node()->get_misc() == 0) {
970 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
972 scheduler->sleep(get_thread(curr));
976 case ATOMIC_NOTIFY_ALL: {
977 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
978 //activate all the waiting threads
979 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
980 scheduler->wake(get_thread(*rit));
985 case ATOMIC_NOTIFY_ONE: {
986 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
987 int wakeupthread = curr->get_node()->get_misc();
988 action_list_t::iterator it = waiters->begin();
989 advance(it, wakeupthread);
990 scheduler->wake(get_thread(*it));
1001 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
1003 /* Do more ambitious checks now that mo is more complete */
1004 if (mo_may_allow(writer, reader)) {
1005 Node *node = reader->get_node();
1007 /* Find an ancestor thread which exists at the time of the reader */
1008 Thread *write_thread = get_thread(writer);
1009 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
1010 write_thread = write_thread->get_parent();
1012 struct future_value fv = {
1013 writer->get_value(),
1014 writer->get_seq_number() + params.maxfuturedelay,
1015 write_thread->get_id(),
1017 if (node->add_future_value(fv))
1018 set_latest_backtrack(reader);
1023 * Process a write ModelAction
1024 * @param curr The ModelAction to process
1025 * @return True if the mo_graph was updated or promises were resolved
1027 bool ModelChecker::process_write(ModelAction *curr)
1029 bool updated_mod_order = w_modification_order(curr);
1030 bool updated_promises = resolve_promises(curr);
1032 if (promises->size() == 0) {
1033 for (unsigned int i = 0; i < futurevalues->size(); i++) {
1034 struct PendingFutureValue pfv = (*futurevalues)[i];
1035 add_future_value(pfv.writer, pfv.act);
1037 futurevalues->clear();
1040 mo_graph->commitChanges();
1041 mo_check_promises(curr, false);
1043 get_thread(curr)->set_return_value(VALUE_NONE);
1044 return updated_mod_order || updated_promises;
1048 * Process a fence ModelAction
1049 * @param curr The ModelAction to process
1050 * @return True if synchronization was updated
1052 bool ModelChecker::process_fence(ModelAction *curr)
1055 * fence-relaxed: no-op
1056 * fence-release: only log the occurence (not in this function), for
1057 * use in later synchronization
1058 * fence-acquire (this function): search for hypothetical release
1061 bool updated = false;
1062 if (curr->is_acquire()) {
1063 action_list_t *list = action_trace;
1064 action_list_t::reverse_iterator rit;
1065 /* Find X : is_read(X) && X --sb-> curr */
1066 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1067 ModelAction *act = *rit;
1070 if (act->get_tid() != curr->get_tid())
1072 /* Stop at the beginning of the thread */
1073 if (act->is_thread_start())
1075 /* Stop once we reach a prior fence-acquire */
1076 if (act->is_fence() && act->is_acquire())
1078 if (!act->is_read())
1080 /* read-acquire will find its own release sequences */
1081 if (act->is_acquire())
1084 /* Establish hypothetical release sequences */
1085 rel_heads_list_t release_heads;
1086 get_release_seq_heads(curr, act, &release_heads);
1087 for (unsigned int i = 0; i < release_heads.size(); i++)
1088 if (!curr->synchronize_with(release_heads[i]))
1089 set_bad_synchronization();
1090 if (release_heads.size() != 0)
1098 * @brief Process the current action for thread-related activity
1100 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1101 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1102 * synchronization, etc. This function is a no-op for non-THREAD actions
1103 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1105 * @param curr The current action
1106 * @return True if synchronization was updated or a thread completed
1108 bool ModelChecker::process_thread_action(ModelAction *curr)
1110 bool updated = false;
1112 switch (curr->get_type()) {
1113 case THREAD_CREATE: {
1114 thrd_t *thrd = (thrd_t *)curr->get_location();
1115 struct thread_params *params = (struct thread_params *)curr->get_value();
1116 Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
1118 th->set_creation(curr);
1119 /* Promises can be satisfied by children */
1120 for (unsigned int i = 0; i < promises->size(); i++) {
1121 Promise *promise = (*promises)[i];
1122 if (promise->thread_is_available(curr->get_tid()))
1123 promise->add_thread(th->get_id());
1128 Thread *blocking = curr->get_thread_operand();
1129 ModelAction *act = get_last_action(blocking->get_id());
1130 curr->synchronize_with(act);
1131 updated = true; /* trigger rel-seq checks */
1134 case THREAD_FINISH: {
1135 Thread *th = get_thread(curr);
1136 while (!th->wait_list_empty()) {
1137 ModelAction *act = th->pop_wait_list();
1138 scheduler->wake(get_thread(act));
1141 /* Completed thread can't satisfy promises */
1142 for (unsigned int i = 0; i < promises->size(); i++) {
1143 Promise *promise = (*promises)[i];
1144 if (promise->thread_is_available(th->get_id()))
1145 if (promise->eliminate_thread(th->get_id()))
1146 priv->failed_promise = true;
1148 updated = true; /* trigger rel-seq checks */
1151 case THREAD_START: {
1152 check_promises(curr->get_tid(), NULL, curr->get_cv());
1163 * @brief Process the current action for release sequence fixup activity
1165 * Performs model-checker release sequence fixups for the current action,
1166 * forcing a single pending release sequence to break (with a given, potential
1167 * "loose" write) or to complete (i.e., synchronize). If a pending release
1168 * sequence forms a complete release sequence, then we must perform the fixup
1169 * synchronization, mo_graph additions, etc.
1171 * @param curr The current action; must be a release sequence fixup action
1172 * @param work_queue The work queue to which to add work items as they are
1175 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1177 const ModelAction *write = curr->get_node()->get_relseq_break();
1178 struct release_seq *sequence = pending_rel_seqs->back();
1179 pending_rel_seqs->pop_back();
1181 ModelAction *acquire = sequence->acquire;
1182 const ModelAction *rf = sequence->rf;
1183 const ModelAction *release = sequence->release;
1187 ASSERT(release->same_thread(rf));
1189 if (write == NULL) {
1191 * @todo Forcing a synchronization requires that we set
1192 * modification order constraints. For instance, we can't allow
1193 * a fixup sequence in which two separate read-acquire
1194 * operations read from the same sequence, where the first one
1195 * synchronizes and the other doesn't. Essentially, we can't
1196 * allow any writes to insert themselves between 'release' and
1200 /* Must synchronize */
1201 if (!acquire->synchronize_with(release)) {
1202 set_bad_synchronization();
1205 /* Re-check all pending release sequences */
1206 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1207 /* Re-check act for mo_graph edges */
1208 work_queue->push_back(MOEdgeWorkEntry(acquire));
1210 /* propagate synchronization to later actions */
1211 action_list_t::reverse_iterator rit = action_trace->rbegin();
1212 for (; (*rit) != acquire; rit++) {
1213 ModelAction *propagate = *rit;
1214 if (acquire->happens_before(propagate)) {
1215 propagate->synchronize_with(acquire);
1216 /* Re-check 'propagate' for mo_graph edges */
1217 work_queue->push_back(MOEdgeWorkEntry(propagate));
1221 /* Break release sequence with new edges:
1222 * release --mo--> write --mo--> rf */
1223 mo_graph->addEdge(release, write);
1224 mo_graph->addEdge(write, rf);
1227 /* See if we have realized a data race */
1232 * Initialize the current action by performing one or more of the following
1233 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1234 * in the NodeStack, manipulating backtracking sets, allocating and
1235 * initializing clock vectors, and computing the promises to fulfill.
1237 * @param curr The current action, as passed from the user context; may be
1238 * freed/invalidated after the execution of this function, with a different
1239 * action "returned" its place (pass-by-reference)
1240 * @return True if curr is a newly-explored action; false otherwise
1242 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1244 ModelAction *newcurr;
1246 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1247 newcurr = process_rmw(*curr);
1250 if (newcurr->is_rmw())
1251 compute_promises(newcurr);
1257 (*curr)->set_seq_number(get_next_seq_num());
1259 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1261 /* First restore type and order in case of RMW operation */
1262 if ((*curr)->is_rmwr())
1263 newcurr->copy_typeandorder(*curr);
1265 ASSERT((*curr)->get_location() == newcurr->get_location());
1266 newcurr->copy_from_new(*curr);
1268 /* Discard duplicate ModelAction; use action from NodeStack */
1271 /* Always compute new clock vector */
1272 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1275 return false; /* Action was explored previously */
1279 /* Always compute new clock vector */
1280 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1282 /* Assign most recent release fence */
1283 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1286 * Perform one-time actions when pushing new ModelAction onto
1289 if (newcurr->is_write())
1290 compute_promises(newcurr);
1291 else if (newcurr->is_relseq_fixup())
1292 compute_relseq_breakwrites(newcurr);
1293 else if (newcurr->is_wait())
1294 newcurr->get_node()->set_misc_max(2);
1295 else if (newcurr->is_notify_one()) {
1296 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1298 return true; /* This was a new ModelAction */
1303 * @brief Establish reads-from relation between two actions
1305 * Perform basic operations involved with establishing a concrete rf relation,
1306 * including setting the ModelAction data and checking for release sequences.
1308 * @param act The action that is reading (must be a read)
1309 * @param rf The action from which we are reading (must be a write)
1311 * @return True if this read established synchronization
1313 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1315 act->set_read_from(rf);
1316 if (rf != NULL && act->is_acquire()) {
1317 rel_heads_list_t release_heads;
1318 get_release_seq_heads(act, act, &release_heads);
1319 int num_heads = release_heads.size();
1320 for (unsigned int i = 0; i < release_heads.size(); i++)
1321 if (!act->synchronize_with(release_heads[i])) {
1322 set_bad_synchronization();
1325 return num_heads > 0;
1331 * Check promises and eliminate potentially-satisfying threads when a thread is
1332 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1333 * no longer satisfy a promise generated from that thread.
1335 * @param blocker The thread on which a thread is waiting
1336 * @param waiting The waiting thread
1338 void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1340 for (unsigned int i = 0; i < promises->size(); i++) {
1341 Promise *promise = (*promises)[i];
1342 ModelAction *reader = promise->get_action();
1343 if (reader->get_tid() != blocker->get_id())
1345 if (!promise->thread_is_available(waiting->get_id()))
1347 if (promise->eliminate_thread(waiting->get_id())) {
1348 /* Promise has failed */
1349 priv->failed_promise = true;
1355 * @brief Check whether a model action is enabled.
1357 * Checks whether a lock or join operation would be successful (i.e., is the
1358 * lock already locked, or is the joined thread already complete). If not, put
1359 * the action in a waiter list.
1361 * @param curr is the ModelAction to check whether it is enabled.
1362 * @return a bool that indicates whether the action is enabled.
1364 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1365 if (curr->is_lock()) {
1366 std::mutex *lock = (std::mutex *)curr->get_location();
1367 struct std::mutex_state *state = lock->get_state();
1368 if (state->islocked) {
1369 //Stick the action in the appropriate waiting queue
1370 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1373 } else if (curr->get_type() == THREAD_JOIN) {
1374 Thread *blocking = (Thread *)curr->get_location();
1375 if (!blocking->is_complete()) {
1376 blocking->push_wait_list(curr);
1377 thread_blocking_check_promises(blocking, get_thread(curr));
1386 * This is the heart of the model checker routine. It performs model-checking
1387 * actions corresponding to a given "current action." Among other processes, it
1388 * calculates reads-from relationships, updates synchronization clock vectors,
1389 * forms a memory_order constraints graph, and handles replay/backtrack
1390 * execution when running permutations of previously-observed executions.
1392 * @param curr The current action to process
1393 * @return The ModelAction that is actually executed; may be different than
1394 * curr; may be NULL, if the current action is not enabled to run
1396 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1399 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1401 if (!check_action_enabled(curr)) {
1402 /* Make the execution look like we chose to run this action
1403 * much later, when a lock/join can succeed */
1404 get_thread(curr)->set_pending(curr);
1405 scheduler->sleep(get_thread(curr));
1409 bool newly_explored = initialize_curr_action(&curr);
1415 wake_up_sleeping_actions(curr);
1417 /* Add the action to lists before any other model-checking tasks */
1418 if (!second_part_of_rmw)
1419 add_action_to_lists(curr);
1421 /* Build may_read_from set for newly-created actions */
1422 if (newly_explored && curr->is_read())
1423 build_may_read_from(curr);
1425 /* Initialize work_queue with the "current action" work */
1426 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1427 while (!work_queue.empty() && !has_asserted()) {
1428 WorkQueueEntry work = work_queue.front();
1429 work_queue.pop_front();
1431 switch (work.type) {
1432 case WORK_CHECK_CURR_ACTION: {
1433 ModelAction *act = work.action;
1434 bool update = false; /* update this location's release seq's */
1435 bool update_all = false; /* update all release seq's */
1437 if (process_thread_action(curr))
1440 if (act->is_read() && !second_part_of_rmw && process_read(act))
1443 if (act->is_write() && process_write(act))
1446 if (act->is_fence() && process_fence(act))
1449 if (act->is_mutex_op() && process_mutex(act))
1452 if (act->is_relseq_fixup())
1453 process_relseq_fixup(curr, &work_queue);
1456 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1458 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1461 case WORK_CHECK_RELEASE_SEQ:
1462 resolve_release_sequences(work.location, &work_queue);
1464 case WORK_CHECK_MO_EDGES: {
1465 /** @todo Complete verification of work_queue */
1466 ModelAction *act = work.action;
1467 bool updated = false;
1469 if (act->is_read()) {
1470 const ModelAction *rf = act->get_reads_from();
1471 const Promise *promise = act->get_reads_from_promise();
1473 if (r_modification_order(act, rf))
1475 } else if (promise) {
1476 if (r_modification_order(act, promise))
1480 if (act->is_write()) {
1481 if (w_modification_order(act))
1484 mo_graph->commitChanges();
1487 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1496 check_curr_backtracking(curr);
1497 set_backtracking(curr);
1501 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1503 Node *currnode = curr->get_node();
1504 Node *parnode = currnode->get_parent();
1506 if ((parnode && !parnode->backtrack_empty()) ||
1507 !currnode->misc_empty() ||
1508 !currnode->read_from_empty() ||
1509 !currnode->promise_empty() ||
1510 !currnode->relseq_break_empty()) {
1511 set_latest_backtrack(curr);
1515 bool ModelChecker::promises_expired() const
1517 for (unsigned int i = 0; i < promises->size(); i++) {
1518 Promise *promise = (*promises)[i];
1519 if (promise->get_expiration() < priv->used_sequence_numbers)
1526 * This is the strongest feasibility check available.
1527 * @return whether the current trace (partial or complete) must be a prefix of
1530 bool ModelChecker::isfeasibleprefix() const
1532 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1536 * Print disagnostic information about an infeasible execution
1537 * @param prefix A string to prefix the output with; if NULL, then a default
1538 * message prefix will be provided
1540 void ModelChecker::print_infeasibility(const char *prefix) const
1544 if (mo_graph->checkForCycles())
1545 ptr += sprintf(ptr, "[mo cycle]");
1546 if (priv->failed_promise)
1547 ptr += sprintf(ptr, "[failed promise]");
1548 if (priv->too_many_reads)
1549 ptr += sprintf(ptr, "[too many reads]");
1550 if (priv->no_valid_reads)
1551 ptr += sprintf(ptr, "[no valid reads-from]");
1552 if (priv->bad_synchronization)
1553 ptr += sprintf(ptr, "[bad sw ordering]");
1554 if (promises_expired())
1555 ptr += sprintf(ptr, "[promise expired]");
1556 if (promises->size() != 0)
1557 ptr += sprintf(ptr, "[unresolved promise]");
1559 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1563 * Returns whether the current completed trace is feasible, except for pending
1564 * release sequences.
1566 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1568 return !is_infeasible() && promises->size() == 0;
1572 * Check if the current partial trace is infeasible. Does not check any
1573 * end-of-execution flags, which might rule out the execution. Thus, this is
1574 * useful only for ruling an execution as infeasible.
1575 * @return whether the current partial trace is infeasible.
1577 bool ModelChecker::is_infeasible() const
1579 return mo_graph->checkForCycles() ||
1580 priv->no_valid_reads ||
1581 priv->failed_promise ||
1582 priv->too_many_reads ||
1583 priv->bad_synchronization ||
1587 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1588 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1589 ModelAction *lastread = get_last_action(act->get_tid());
1590 lastread->process_rmw(act);
1591 if (act->is_rmw()) {
1592 if (lastread->get_reads_from())
1593 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1595 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1596 mo_graph->commitChanges();
1602 * Checks whether a thread has read from the same write for too many times
1603 * without seeing the effects of a later write.
1606 * 1) there must a different write that we could read from that would satisfy the modification order,
1607 * 2) we must have read from the same value in excess of maxreads times, and
1608 * 3) that other write must have been in the reads_from set for maxreads times.
1610 * If so, we decide that the execution is no longer feasible.
1612 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1614 if (params.maxreads != 0) {
1615 if (curr->get_node()->get_read_from_past_size() <= 1)
1617 //Must make sure that execution is currently feasible... We could
1618 //accidentally clear by rolling back
1619 if (is_infeasible())
1621 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1622 int tid = id_to_int(curr->get_tid());
1625 if ((int)thrd_lists->size() <= tid)
1627 action_list_t *list = &(*thrd_lists)[tid];
1629 action_list_t::reverse_iterator rit = list->rbegin();
1630 /* Skip past curr */
1631 for (; (*rit) != curr; rit++)
1633 /* go past curr now */
1636 action_list_t::reverse_iterator ritcopy = rit;
1637 //See if we have enough reads from the same value
1639 for (; count < params.maxreads; rit++, count++) {
1640 if (rit == list->rend())
1642 ModelAction *act = *rit;
1643 if (!act->is_read())
1646 if (act->get_reads_from() != rf)
1648 if (act->get_node()->get_read_from_past_size() <= 1)
1651 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1653 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1655 /* Need a different write */
1659 /* Test to see whether this is a feasible write to read from */
1660 /** NOTE: all members of read-from set should be
1661 * feasible, so we no longer check it here **/
1665 bool feasiblewrite = true;
1666 //new we need to see if this write works for everyone
1668 for (int loop = count; loop > 0; loop--, rit++) {
1669 ModelAction *act = *rit;
1670 bool foundvalue = false;
1671 for (int j = 0; j < act->get_node()->get_read_from_past_size(); j++) {
1672 if (act->get_node()->get_read_from_past(j) == write) {
1678 feasiblewrite = false;
1682 if (feasiblewrite) {
1683 priv->too_many_reads = true;
1691 * Updates the mo_graph with the constraints imposed from the current
1694 * Basic idea is the following: Go through each other thread and find
1695 * the last action that happened before our read. Two cases:
1697 * (1) The action is a write => that write must either occur before
1698 * the write we read from or be the write we read from.
1700 * (2) The action is a read => the write that that action read from
1701 * must occur before the write we read from or be the same write.
1703 * @param curr The current action. Must be a read.
1704 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1705 * @return True if modification order edges were added; false otherwise
1707 template <typename rf_type>
1708 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1710 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1713 ASSERT(curr->is_read());
1715 /* Last SC fence in the current thread */
1716 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1718 /* Iterate over all threads */
1719 for (i = 0; i < thrd_lists->size(); i++) {
1720 /* Last SC fence in thread i */
1721 ModelAction *last_sc_fence_thread_local = NULL;
1722 if (int_to_id((int)i) != curr->get_tid())
1723 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1725 /* Last SC fence in thread i, before last SC fence in current thread */
1726 ModelAction *last_sc_fence_thread_before = NULL;
1727 if (last_sc_fence_local)
1728 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1730 /* Iterate over actions in thread, starting from most recent */
1731 action_list_t *list = &(*thrd_lists)[i];
1732 action_list_t::reverse_iterator rit;
1733 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1734 ModelAction *act = *rit;
1736 if (act->is_write() && !act->equals(rf) && act != curr) {
1737 /* C++, Section 29.3 statement 5 */
1738 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1739 *act < *last_sc_fence_thread_local) {
1740 added = mo_graph->addEdge(act, rf) || added;
1743 /* C++, Section 29.3 statement 4 */
1744 else if (act->is_seqcst() && last_sc_fence_local &&
1745 *act < *last_sc_fence_local) {
1746 added = mo_graph->addEdge(act, rf) || added;
1749 /* C++, Section 29.3 statement 6 */
1750 else if (last_sc_fence_thread_before &&
1751 *act < *last_sc_fence_thread_before) {
1752 added = mo_graph->addEdge(act, rf) || added;
1758 * Include at most one act per-thread that "happens
1759 * before" curr. Don't consider reflexively.
1761 if (act->happens_before(curr) && act != curr) {
1762 if (act->is_write()) {
1763 if (!act->equals(rf)) {
1764 added = mo_graph->addEdge(act, rf) || added;
1767 const ModelAction *prevrf = act->get_reads_from();
1768 const Promise *prevrf_promise = act->get_reads_from_promise();
1770 if (!prevrf->equals(rf))
1771 added = mo_graph->addEdge(prevrf, rf) || added;
1772 } else if (!prevrf_promise->equals(rf)) {
1773 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1782 * All compatible, thread-exclusive promises must be ordered after any
1783 * concrete loads from the same thread
1785 for (unsigned int i = 0; i < promises->size(); i++)
1786 if ((*promises)[i]->is_compatible_exclusive(curr))
1787 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1793 * Updates the mo_graph with the constraints imposed from the current write.
1795 * Basic idea is the following: Go through each other thread and find
1796 * the lastest action that happened before our write. Two cases:
1798 * (1) The action is a write => that write must occur before
1801 * (2) The action is a read => the write that that action read from
1802 * must occur before the current write.
1804 * This method also handles two other issues:
1806 * (I) Sequential Consistency: Making sure that if the current write is
1807 * seq_cst, that it occurs after the previous seq_cst write.
1809 * (II) Sending the write back to non-synchronizing reads.
1811 * @param curr The current action. Must be a write.
1812 * @return True if modification order edges were added; false otherwise
1814 bool ModelChecker::w_modification_order(ModelAction *curr)
1816 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1819 ASSERT(curr->is_write());
1821 if (curr->is_seqcst()) {
1822 /* We have to at least see the last sequentially consistent write,
1823 so we are initialized. */
1824 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1825 if (last_seq_cst != NULL) {
1826 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1830 /* Last SC fence in the current thread */
1831 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1833 /* Iterate over all threads */
1834 for (i = 0; i < thrd_lists->size(); i++) {
1835 /* Last SC fence in thread i, before last SC fence in current thread */
1836 ModelAction *last_sc_fence_thread_before = NULL;
1837 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1838 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1840 /* Iterate over actions in thread, starting from most recent */
1841 action_list_t *list = &(*thrd_lists)[i];
1842 action_list_t::reverse_iterator rit;
1843 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1844 ModelAction *act = *rit;
1847 * 1) If RMW and it actually read from something, then we
1848 * already have all relevant edges, so just skip to next
1851 * 2) If RMW and it didn't read from anything, we should
1852 * whatever edge we can get to speed up convergence.
1854 * 3) If normal write, we need to look at earlier actions, so
1855 * continue processing list.
1857 if (curr->is_rmw()) {
1858 if (curr->get_reads_from() != NULL)
1866 /* C++, Section 29.3 statement 7 */
1867 if (last_sc_fence_thread_before && act->is_write() &&
1868 *act < *last_sc_fence_thread_before) {
1869 added = mo_graph->addEdge(act, curr) || added;
1874 * Include at most one act per-thread that "happens
1877 if (act->happens_before(curr)) {
1879 * Note: if act is RMW, just add edge:
1881 * The following edge should be handled elsewhere:
1882 * readfrom(act) --mo--> act
1884 if (act->is_write())
1885 added = mo_graph->addEdge(act, curr) || added;
1886 else if (act->is_read()) {
1887 //if previous read accessed a null, just keep going
1888 if (act->get_reads_from() == NULL)
1890 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1893 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1894 !act->same_thread(curr)) {
1895 /* We have an action that:
1896 (1) did not happen before us
1897 (2) is a read and we are a write
1898 (3) cannot synchronize with us
1899 (4) is in a different thread
1901 that read could potentially read from our write. Note that
1902 these checks are overly conservative at this point, we'll
1903 do more checks before actually removing the
1907 if (thin_air_constraint_may_allow(curr, act)) {
1908 if (!is_infeasible())
1909 futurevalues->push_back(PendingFutureValue(curr, act));
1910 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1911 add_future_value(curr, act);
1918 * All compatible, thread-exclusive promises must be ordered after any
1919 * concrete stores to the same thread, or else they can be merged with
1922 for (unsigned int i = 0; i < promises->size(); i++)
1923 if ((*promises)[i]->is_compatible_exclusive(curr))
1924 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1929 /** Arbitrary reads from the future are not allowed. Section 29.3
1930 * part 9 places some constraints. This method checks one result of constraint
1931 * constraint. Others require compiler support. */
1932 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1934 if (!writer->is_rmw())
1937 if (!reader->is_rmw())
1940 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1941 if (search == reader)
1943 if (search->get_tid() == reader->get_tid() &&
1944 search->happens_before(reader))
1952 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1953 * some constraints. This method checks one the following constraint (others
1954 * require compiler support):
1956 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1958 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1960 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1962 /* Iterate over all threads */
1963 for (i = 0; i < thrd_lists->size(); i++) {
1964 const ModelAction *write_after_read = NULL;
1966 /* Iterate over actions in thread, starting from most recent */
1967 action_list_t *list = &(*thrd_lists)[i];
1968 action_list_t::reverse_iterator rit;
1969 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1970 ModelAction *act = *rit;
1972 /* Don't disallow due to act == reader */
1973 if (!reader->happens_before(act) || reader == act)
1975 else if (act->is_write())
1976 write_after_read = act;
1977 else if (act->is_read() && act->get_reads_from() != NULL)
1978 write_after_read = act->get_reads_from();
1981 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
1988 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
1989 * The ModelAction under consideration is expected to be taking part in
1990 * release/acquire synchronization as an object of the "reads from" relation.
1991 * Note that this can only provide release sequence support for RMW chains
1992 * which do not read from the future, as those actions cannot be traced until
1993 * their "promise" is fulfilled. Similarly, we may not even establish the
1994 * presence of a release sequence with certainty, as some modification order
1995 * constraints may be decided further in the future. Thus, this function
1996 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
1997 * and a boolean representing certainty.
1999 * @param rf The action that might be part of a release sequence. Must be a
2001 * @param release_heads A pass-by-reference style return parameter. After
2002 * execution of this function, release_heads will contain the heads of all the
2003 * relevant release sequences, if any exists with certainty
2004 * @param pending A pass-by-reference style return parameter which is only used
2005 * when returning false (i.e., uncertain). Returns most information regarding
2006 * an uncertain release sequence, including any write operations that might
2007 * break the sequence.
2008 * @return true, if the ModelChecker is certain that release_heads is complete;
2011 bool ModelChecker::release_seq_heads(const ModelAction *rf,
2012 rel_heads_list_t *release_heads,
2013 struct release_seq *pending) const
2015 /* Only check for release sequences if there are no cycles */
2016 if (mo_graph->checkForCycles())
2019 for ( ; rf != NULL; rf = rf->get_reads_from()) {
2020 ASSERT(rf->is_write());
2022 if (rf->is_release())
2023 release_heads->push_back(rf);
2024 else if (rf->get_last_fence_release())
2025 release_heads->push_back(rf->get_last_fence_release());
2027 break; /* End of RMW chain */
2029 /** @todo Need to be smarter here... In the linux lock
2030 * example, this will run to the beginning of the program for
2032 /** @todo The way to be smarter here is to keep going until 1
2033 * thread has a release preceded by an acquire and you've seen
2036 /* acq_rel RMW is a sufficient stopping condition */
2037 if (rf->is_acquire() && rf->is_release())
2038 return true; /* complete */
2041 /* read from future: need to settle this later */
2043 return false; /* incomplete */
2046 if (rf->is_release())
2047 return true; /* complete */
2049 /* else relaxed write
2050 * - check for fence-release in the same thread (29.8, stmt. 3)
2051 * - check modification order for contiguous subsequence
2052 * -> rf must be same thread as release */
2054 const ModelAction *fence_release = rf->get_last_fence_release();
2055 /* Synchronize with a fence-release unconditionally; we don't need to
2056 * find any more "contiguous subsequence..." for it */
2058 release_heads->push_back(fence_release);
2060 int tid = id_to_int(rf->get_tid());
2061 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
2062 action_list_t *list = &(*thrd_lists)[tid];
2063 action_list_t::const_reverse_iterator rit;
2065 /* Find rf in the thread list */
2066 rit = std::find(list->rbegin(), list->rend(), rf);
2067 ASSERT(rit != list->rend());
2069 /* Find the last {write,fence}-release */
2070 for (; rit != list->rend(); rit++) {
2071 if (fence_release && *(*rit) < *fence_release)
2073 if ((*rit)->is_release())
2076 if (rit == list->rend()) {
2077 /* No write-release in this thread */
2078 return true; /* complete */
2079 } else if (fence_release && *(*rit) < *fence_release) {
2080 /* The fence-release is more recent (and so, "stronger") than
2081 * the most recent write-release */
2082 return true; /* complete */
2083 } /* else, need to establish contiguous release sequence */
2084 ModelAction *release = *rit;
2086 ASSERT(rf->same_thread(release));
2088 pending->writes.clear();
2090 bool certain = true;
2091 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2092 if (id_to_int(rf->get_tid()) == (int)i)
2094 list = &(*thrd_lists)[i];
2096 /* Can we ensure no future writes from this thread may break
2097 * the release seq? */
2098 bool future_ordered = false;
2100 ModelAction *last = get_last_action(int_to_id(i));
2101 Thread *th = get_thread(int_to_id(i));
2102 if ((last && rf->happens_before(last)) ||
2105 future_ordered = true;
2107 ASSERT(!th->is_model_thread() || future_ordered);
2109 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2110 const ModelAction *act = *rit;
2111 /* Reach synchronization -> this thread is complete */
2112 if (act->happens_before(release))
2114 if (rf->happens_before(act)) {
2115 future_ordered = true;
2119 /* Only non-RMW writes can break release sequences */
2120 if (!act->is_write() || act->is_rmw())
2123 /* Check modification order */
2124 if (mo_graph->checkReachable(rf, act)) {
2125 /* rf --mo--> act */
2126 future_ordered = true;
2129 if (mo_graph->checkReachable(act, release))
2130 /* act --mo--> release */
2132 if (mo_graph->checkReachable(release, act) &&
2133 mo_graph->checkReachable(act, rf)) {
2134 /* release --mo-> act --mo--> rf */
2135 return true; /* complete */
2137 /* act may break release sequence */
2138 pending->writes.push_back(act);
2141 if (!future_ordered)
2142 certain = false; /* This thread is uncertain */
2146 release_heads->push_back(release);
2147 pending->writes.clear();
2149 pending->release = release;
2156 * An interface for getting the release sequence head(s) with which a
2157 * given ModelAction must synchronize. This function only returns a non-empty
2158 * result when it can locate a release sequence head with certainty. Otherwise,
2159 * it may mark the internal state of the ModelChecker so that it will handle
2160 * the release sequence at a later time, causing @a acquire to update its
2161 * synchronization at some later point in execution.
2163 * @param acquire The 'acquire' action that may synchronize with a release
2165 * @param read The read action that may read from a release sequence; this may
2166 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2167 * when 'acquire' is a fence-acquire)
2168 * @param release_heads A pass-by-reference return parameter. Will be filled
2169 * with the head(s) of the release sequence(s), if they exists with certainty.
2170 * @see ModelChecker::release_seq_heads
2172 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2173 ModelAction *read, rel_heads_list_t *release_heads)
2175 const ModelAction *rf = read->get_reads_from();
2176 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2177 sequence->acquire = acquire;
2178 sequence->read = read;
2180 if (!release_seq_heads(rf, release_heads, sequence)) {
2181 /* add act to 'lazy checking' list */
2182 pending_rel_seqs->push_back(sequence);
2184 snapshot_free(sequence);
2189 * Attempt to resolve all stashed operations that might synchronize with a
2190 * release sequence for a given location. This implements the "lazy" portion of
2191 * determining whether or not a release sequence was contiguous, since not all
2192 * modification order information is present at the time an action occurs.
2194 * @param location The location/object that should be checked for release
2195 * sequence resolutions. A NULL value means to check all locations.
2196 * @param work_queue The work queue to which to add work items as they are
2198 * @return True if any updates occurred (new synchronization, new mo_graph
2201 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2203 bool updated = false;
2204 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2205 while (it != pending_rel_seqs->end()) {
2206 struct release_seq *pending = *it;
2207 ModelAction *acquire = pending->acquire;
2208 const ModelAction *read = pending->read;
2210 /* Only resolve sequences on the given location, if provided */
2211 if (location && read->get_location() != location) {
2216 const ModelAction *rf = read->get_reads_from();
2217 rel_heads_list_t release_heads;
2219 complete = release_seq_heads(rf, &release_heads, pending);
2220 for (unsigned int i = 0; i < release_heads.size(); i++) {
2221 if (!acquire->has_synchronized_with(release_heads[i])) {
2222 if (acquire->synchronize_with(release_heads[i]))
2225 set_bad_synchronization();
2230 /* Re-check all pending release sequences */
2231 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2232 /* Re-check read-acquire for mo_graph edges */
2233 if (acquire->is_read())
2234 work_queue->push_back(MOEdgeWorkEntry(acquire));
2236 /* propagate synchronization to later actions */
2237 action_list_t::reverse_iterator rit = action_trace->rbegin();
2238 for (; (*rit) != acquire; rit++) {
2239 ModelAction *propagate = *rit;
2240 if (acquire->happens_before(propagate)) {
2241 propagate->synchronize_with(acquire);
2242 /* Re-check 'propagate' for mo_graph edges */
2243 work_queue->push_back(MOEdgeWorkEntry(propagate));
2248 it = pending_rel_seqs->erase(it);
2249 snapshot_free(pending);
2255 // If we resolved promises or data races, see if we have realized a data race.
2262 * Performs various bookkeeping operations for the current ModelAction. For
2263 * instance, adds action to the per-object, per-thread action vector and to the
2264 * action trace list of all thread actions.
2266 * @param act is the ModelAction to add.
2268 void ModelChecker::add_action_to_lists(ModelAction *act)
2270 int tid = id_to_int(act->get_tid());
2271 ModelAction *uninit = NULL;
2273 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2274 if (list->empty() && act->is_atomic_var()) {
2275 uninit = new_uninitialized_action(act->get_location());
2276 uninit_id = id_to_int(uninit->get_tid());
2277 list->push_back(uninit);
2279 list->push_back(act);
2281 action_trace->push_back(act);
2283 action_trace->push_front(uninit);
2285 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2286 if (tid >= (int)vec->size())
2287 vec->resize(priv->next_thread_id);
2288 (*vec)[tid].push_back(act);
2290 (*vec)[uninit_id].push_front(uninit);
2292 if ((int)thrd_last_action->size() <= tid)
2293 thrd_last_action->resize(get_num_threads());
2294 (*thrd_last_action)[tid] = act;
2296 (*thrd_last_action)[uninit_id] = uninit;
2298 if (act->is_fence() && act->is_release()) {
2299 if ((int)thrd_last_fence_release->size() <= tid)
2300 thrd_last_fence_release->resize(get_num_threads());
2301 (*thrd_last_fence_release)[tid] = act;
2304 if (act->is_wait()) {
2305 void *mutex_loc = (void *) act->get_value();
2306 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2308 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2309 if (tid >= (int)vec->size())
2310 vec->resize(priv->next_thread_id);
2311 (*vec)[tid].push_back(act);
2316 * @brief Get the last action performed by a particular Thread
2317 * @param tid The thread ID of the Thread in question
2318 * @return The last action in the thread
2320 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2322 int threadid = id_to_int(tid);
2323 if (threadid < (int)thrd_last_action->size())
2324 return (*thrd_last_action)[id_to_int(tid)];
2330 * @brief Get the last fence release performed by a particular Thread
2331 * @param tid The thread ID of the Thread in question
2332 * @return The last fence release in the thread, if one exists; NULL otherwise
2334 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2336 int threadid = id_to_int(tid);
2337 if (threadid < (int)thrd_last_fence_release->size())
2338 return (*thrd_last_fence_release)[id_to_int(tid)];
2344 * Gets the last memory_order_seq_cst write (in the total global sequence)
2345 * performed on a particular object (i.e., memory location), not including the
2347 * @param curr The current ModelAction; also denotes the object location to
2349 * @return The last seq_cst write
2351 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2353 void *location = curr->get_location();
2354 action_list_t *list = get_safe_ptr_action(obj_map, location);
2355 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2356 action_list_t::reverse_iterator rit;
2357 for (rit = list->rbegin(); rit != list->rend(); rit++)
2358 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2364 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2365 * performed in a particular thread, prior to a particular fence.
2366 * @param tid The ID of the thread to check
2367 * @param before_fence The fence from which to begin the search; if NULL, then
2368 * search for the most recent fence in the thread.
2369 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2371 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2373 /* All fences should have NULL location */
2374 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2375 action_list_t::reverse_iterator rit = list->rbegin();
2378 for (; rit != list->rend(); rit++)
2379 if (*rit == before_fence)
2382 ASSERT(*rit == before_fence);
2386 for (; rit != list->rend(); rit++)
2387 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2393 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2394 * location). This function identifies the mutex according to the current
2395 * action, which is presumed to perform on the same mutex.
2396 * @param curr The current ModelAction; also denotes the object location to
2398 * @return The last unlock operation
2400 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2402 void *location = curr->get_location();
2403 action_list_t *list = get_safe_ptr_action(obj_map, location);
2404 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2405 action_list_t::reverse_iterator rit;
2406 for (rit = list->rbegin(); rit != list->rend(); rit++)
2407 if ((*rit)->is_unlock() || (*rit)->is_wait())
2412 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2414 ModelAction *parent = get_last_action(tid);
2416 parent = get_thread(tid)->get_creation();
2421 * Returns the clock vector for a given thread.
2422 * @param tid The thread whose clock vector we want
2423 * @return Desired clock vector
2425 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2427 return get_parent_action(tid)->get_cv();
2431 * Resolve a set of Promises with a current write. The set is provided in the
2432 * Node corresponding to @a write.
2433 * @param write The ModelAction that is fulfilling Promises
2434 * @return True if promises were resolved; false otherwise
2436 bool ModelChecker::resolve_promises(ModelAction *write)
2438 bool haveResolved = false;
2439 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2440 promise_list_t mustResolve, resolved;
2442 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2443 Promise *promise = (*promises)[promise_index];
2444 if (write->get_node()->get_promise(i)) {
2445 ModelAction *read = promise->get_action();
2446 read_from(read, write);
2447 //Make sure the promise's value matches the write's value
2448 ASSERT(promise->is_compatible(write));
2449 mo_graph->resolvePromise(promise, write, &mustResolve);
2451 resolved.push_back(promise);
2452 promises->erase(promises->begin() + promise_index);
2453 actions_to_check.push_back(read);
2455 haveResolved = true;
2460 for (unsigned int i = 0; i < mustResolve.size(); i++) {
2461 if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
2463 priv->failed_promise = true;
2465 for (unsigned int i = 0; i < resolved.size(); i++)
2467 //Check whether reading these writes has made threads unable to
2470 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2471 ModelAction *read = actions_to_check[i];
2472 mo_check_promises(read, true);
2475 return haveResolved;
2479 * Compute the set of promises that could potentially be satisfied by this
2480 * action. Note that the set computation actually appears in the Node, not in
2482 * @param curr The ModelAction that may satisfy promises
2484 void ModelChecker::compute_promises(ModelAction *curr)
2486 for (unsigned int i = 0; i < promises->size(); i++) {
2487 Promise *promise = (*promises)[i];
2488 const ModelAction *act = promise->get_action();
2489 ASSERT(act->is_read());
2490 if (!act->happens_before(curr) &&
2491 !act->could_synchronize_with(curr) &&
2492 promise->is_compatible(curr) &&
2493 promise->get_value() == curr->get_value()) {
2494 curr->get_node()->set_promise(i, act->is_rmw());
2499 /** Checks promises in response to change in ClockVector Threads. */
2500 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2502 for (unsigned int i = 0; i < promises->size(); i++) {
2503 Promise *promise = (*promises)[i];
2504 const ModelAction *act = promise->get_action();
2505 if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
2506 merge_cv->synchronized_since(act)) {
2507 if (promise->eliminate_thread(tid)) {
2508 //Promise has failed
2509 priv->failed_promise = true;
2516 void ModelChecker::check_promises_thread_disabled()
2518 for (unsigned int i = 0; i < promises->size(); i++) {
2519 Promise *promise = (*promises)[i];
2520 if (promise->has_failed()) {
2521 priv->failed_promise = true;
2528 * @brief Checks promises in response to addition to modification order for
2531 * We test whether threads are still available for satisfying promises after an
2532 * addition to our modification order constraints. Those that are unavailable
2533 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2534 * that promise has failed.
2536 * @param act The ModelAction which updated the modification order
2537 * @param is_read_check Should be true if act is a read and we must check for
2538 * updates to the store from which it read (there is a distinction here for
2539 * RMW's, which are both a load and a store)
2541 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2543 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2545 for (unsigned int i = 0; i < promises->size(); i++) {
2546 Promise *promise = (*promises)[i];
2547 const ModelAction *pread = promise->get_action();
2549 // Is this promise on the same location?
2550 if (!pread->same_var(write))
2553 if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
2554 priv->failed_promise = true;
2558 // Don't do any lookups twice for the same thread
2559 if (!promise->thread_is_available(act->get_tid()))
2562 if (mo_graph->checkReachable(promise, write)) {
2563 if (mo_graph->checkPromise(write, promise)) {
2564 priv->failed_promise = true;
2572 * Compute the set of writes that may break the current pending release
2573 * sequence. This information is extracted from previou release sequence
2576 * @param curr The current ModelAction. Must be a release sequence fixup
2579 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2581 if (pending_rel_seqs->empty())
2584 struct release_seq *pending = pending_rel_seqs->back();
2585 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2586 const ModelAction *write = pending->writes[i];
2587 curr->get_node()->add_relseq_break(write);
2590 /* NULL means don't break the sequence; just synchronize */
2591 curr->get_node()->add_relseq_break(NULL);
2595 * Build up an initial set of all past writes that this 'read' action may read
2596 * from, as well as any previously-observed future values that must still be valid.
2598 * @param curr is the current ModelAction that we are exploring; it must be a
2601 void ModelChecker::build_may_read_from(ModelAction *curr)
2603 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2605 ASSERT(curr->is_read());
2607 ModelAction *last_sc_write = NULL;
2609 if (curr->is_seqcst())
2610 last_sc_write = get_last_seq_cst_write(curr);
2612 /* Iterate over all threads */
2613 for (i = 0; i < thrd_lists->size(); i++) {
2614 /* Iterate over actions in thread, starting from most recent */
2615 action_list_t *list = &(*thrd_lists)[i];
2616 action_list_t::reverse_iterator rit;
2617 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2618 ModelAction *act = *rit;
2620 /* Only consider 'write' actions */
2621 if (!act->is_write() || act == curr)
2624 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2625 bool allow_read = true;
2627 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2629 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2633 /* Only add feasible reads */
2634 mo_graph->startChanges();
2635 r_modification_order(curr, act);
2636 if (!is_infeasible())
2637 curr->get_node()->add_read_from_past(act);
2638 mo_graph->rollbackChanges();
2641 /* Include at most one act per-thread that "happens before" curr */
2642 if (act->happens_before(curr))
2647 /* Inherit existing, promised future values */
2648 for (i = 0; i < promises->size(); i++) {
2649 const Promise *promise = (*promises)[i];
2650 const ModelAction *promise_read = promise->get_action();
2651 if (promise_read->same_var(curr)) {
2652 /* Only add feasible future-values */
2653 mo_graph->startChanges();
2654 r_modification_order(curr, promise);
2655 if (!is_infeasible()) {
2656 const struct future_value fv = promise->get_fv();
2657 curr->get_node()->add_future_value(fv);
2659 mo_graph->rollbackChanges();
2663 /* We may find no valid may-read-from only if the execution is doomed */
2664 if (!curr->get_node()->read_from_size()) {
2665 priv->no_valid_reads = true;
2669 if (DBG_ENABLED()) {
2670 model_print("Reached read action:\n");
2672 model_print("Printing read_from_past\n");
2673 curr->get_node()->print_read_from_past();
2674 model_print("End printing read_from_past\n");
2678 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2680 for ( ; write != NULL; write = write->get_reads_from()) {
2681 /* UNINIT actions don't have a Node, and they never sleep */
2682 if (write->is_uninitialized())
2684 Node *prevnode = write->get_node()->get_parent();
2686 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2687 if (write->is_release() && thread_sleep)
2689 if (!write->is_rmw())
2696 * @brief Create a new action representing an uninitialized atomic
2697 * @param location The memory location of the atomic object
2698 * @return A pointer to a new ModelAction
2700 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2702 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2703 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2704 act->create_cv(NULL);
2708 static void print_list(action_list_t *list)
2710 action_list_t::iterator it;
2712 model_print("---------------------------------------------------------------------\n");
2714 unsigned int hash = 0;
2716 for (it = list->begin(); it != list->end(); it++) {
2718 hash = hash^(hash<<3)^((*it)->hash());
2720 model_print("HASH %u\n", hash);
2721 model_print("---------------------------------------------------------------------\n");
2724 #if SUPPORT_MOD_ORDER_DUMP
2725 void ModelChecker::dumpGraph(char *filename) const
2728 sprintf(buffer, "%s.dot", filename);
2729 FILE *file = fopen(buffer, "w");
2730 fprintf(file, "digraph %s {\n", filename);
2731 mo_graph->dumpNodes(file);
2732 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2734 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2735 ModelAction *action = *it;
2736 if (action->is_read()) {
2737 fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2738 if (action->get_reads_from() != NULL)
2739 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2741 if (thread_array[action->get_tid()] != NULL) {
2742 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2745 thread_array[action->get_tid()] = action;
2747 fprintf(file, "}\n");
2748 model_free(thread_array);
2753 /** @brief Prints an execution trace summary. */
2754 void ModelChecker::print_summary() const
2756 #if SUPPORT_MOD_ORDER_DUMP
2757 char buffername[100];
2758 sprintf(buffername, "exec%04u", stats.num_total);
2759 mo_graph->dumpGraphToFile(buffername);
2760 sprintf(buffername, "graph%04u", stats.num_total);
2761 dumpGraph(buffername);
2764 model_print("Execution %d:", stats.num_total);
2765 if (isfeasibleprefix())
2768 print_infeasibility(" INFEASIBLE");
2769 print_list(action_trace);
2774 * Add a Thread to the system for the first time. Should only be called once
2776 * @param t The Thread to add
2778 void ModelChecker::add_thread(Thread *t)
2780 thread_map->put(id_to_int(t->get_id()), t);
2781 scheduler->add_thread(t);
2785 * Removes a thread from the scheduler.
2786 * @param the thread to remove.
2788 void ModelChecker::remove_thread(Thread *t)
2790 scheduler->remove_thread(t);
2794 * @brief Get a Thread reference by its ID
2795 * @param tid The Thread's ID
2796 * @return A Thread reference
2798 Thread * ModelChecker::get_thread(thread_id_t tid) const
2800 return thread_map->get(id_to_int(tid));
2804 * @brief Get a reference to the Thread in which a ModelAction was executed
2805 * @param act The ModelAction
2806 * @return A Thread reference
2808 Thread * ModelChecker::get_thread(const ModelAction *act) const
2810 return get_thread(act->get_tid());
2814 * @brief Check if a Thread is currently enabled
2815 * @param t The Thread to check
2816 * @return True if the Thread is currently enabled
2818 bool ModelChecker::is_enabled(Thread *t) const
2820 return scheduler->is_enabled(t);
2824 * @brief Check if a Thread is currently enabled
2825 * @param tid The ID of the Thread to check
2826 * @return True if the Thread is currently enabled
2828 bool ModelChecker::is_enabled(thread_id_t tid) const
2830 return scheduler->is_enabled(tid);
2834 * Switch from a model-checker context to a user-thread context. This is the
2835 * complement of ModelChecker::switch_to_master and must be called from the
2836 * model-checker context
2838 * @param thread The user-thread to switch to
2840 void ModelChecker::switch_from_master(Thread *thread)
2842 scheduler->set_current_thread(thread);
2843 Thread::swap(&system_context, thread);
2847 * Switch from a user-context to the "master thread" context (a.k.a. system
2848 * context). This switch is made with the intention of exploring a particular
2849 * model-checking action (described by a ModelAction object). Must be called
2850 * from a user-thread context.
2852 * @param act The current action that will be explored. May be NULL only if
2853 * trace is exiting via an assertion (see ModelChecker::set_assert and
2854 * ModelChecker::has_asserted).
2855 * @return Return the value returned by the current action
2857 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2860 Thread *old = thread_current();
2861 ASSERT(!old->get_pending());
2862 old->set_pending(act);
2863 if (Thread::swap(old, &system_context) < 0) {
2864 perror("swap threads");
2867 return old->get_return_value();
2871 * Takes the next step in the execution, if possible.
2872 * @param curr The current step to take
2873 * @return Returns the next Thread to run, if any; NULL if this execution
2876 Thread * ModelChecker::take_step(ModelAction *curr)
2878 Thread *curr_thrd = get_thread(curr);
2879 ASSERT(curr_thrd->get_state() == THREAD_READY);
2881 curr = check_current_action(curr);
2883 /* Infeasible -> don't take any more steps */
2884 if (is_infeasible())
2886 else if (isfeasibleprefix() && have_bug_reports()) {
2891 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2894 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2895 scheduler->remove_thread(curr_thrd);
2897 Thread *next_thrd = get_next_thread(curr);
2899 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2900 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2905 /** Wrapper to run the user's main function, with appropriate arguments */
2906 void user_main_wrapper(void *)
2908 user_main(model->params.argc, model->params.argv);
2911 /** @brief Run ModelChecker for the user program */
2912 void ModelChecker::run()
2916 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
2921 * Stash next pending action(s) for thread(s). There
2922 * should only need to stash one thread's action--the
2923 * thread which just took a step--plus the first step
2924 * for any newly-created thread
2926 for (unsigned int i = 0; i < get_num_threads(); i++) {
2927 thread_id_t tid = int_to_id(i);
2928 Thread *thr = get_thread(tid);
2929 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
2930 switch_from_master(thr);
2934 /* Catch assertions from prior take_step or from
2935 * between-ModelAction bugs (e.g., data races) */
2939 /* Consume the next action for a Thread */
2940 ModelAction *curr = t->get_pending();
2941 t->set_pending(NULL);
2942 t = take_step(curr);
2943 } while (t && !t->is_model_thread());
2946 * Launch end-of-execution release sequence fixups only when
2947 * the execution is otherwise feasible AND there are:
2949 * (1) pending release sequences
2950 * (2) pending assertions that could be invalidated by a change
2951 * in clock vectors (i.e., data races)
2952 * (3) no pending promises
2954 while (!pending_rel_seqs->empty() &&
2955 is_feasible_prefix_ignore_relseq() &&
2956 !unrealizedraces.empty()) {
2957 model_print("*** WARNING: release sequence fixup action "
2958 "(%zu pending release seuqence(s)) ***\n",
2959 pending_rel_seqs->size());
2960 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2961 std::memory_order_seq_cst, NULL, VALUE_NONE,
2965 } while (next_execution());
2967 model_print("******* Model-checking complete: *******\n");