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 * @todo We can violate this ASSERT() when fairness/sleep sets
491 * conflict to cause an execution to terminate, e.g. with:
492 * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
494 //ASSERT(scheduler->all_threads_sleeping());
498 /** @brief Print execution stats */
499 void ModelChecker::print_stats() const
501 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
502 model_print("Number of redundant executions: %d\n", stats.num_redundant);
503 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
504 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
505 model_print("Total executions: %d\n", stats.num_total);
506 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
510 * @brief End-of-exeuction print
511 * @param printbugs Should any existing bugs be printed?
513 void ModelChecker::print_execution(bool printbugs) const
515 print_program_output();
517 if (DBG_ENABLED() || params.verbose) {
518 model_print("Earliest divergence point since last feasible execution:\n");
519 if (earliest_diverge)
520 earliest_diverge->print();
522 model_print("(Not set)\n");
528 /* Don't print invalid bugs */
537 * Queries the model-checker for more executions to explore and, if one
538 * exists, resets the model-checker state to execute a new execution.
540 * @return If there are more executions to explore, return true. Otherwise,
543 bool ModelChecker::next_execution()
546 /* Is this execution a feasible execution that's worth bug-checking? */
547 bool complete = isfeasibleprefix() && (is_complete_execution() ||
550 /* End-of-execution bug checks */
553 assert_bug("Deadlock detected");
561 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
562 print_execution(complete);
564 clear_program_output();
567 earliest_diverge = NULL;
569 if ((diverge = get_next_backtrack()) == NULL)
573 model_print("Next execution will diverge at:\n");
577 reset_to_initial_state();
582 * @brief Find the last fence-related backtracking conflict for a ModelAction
584 * This function performs the search for the most recent conflicting action
585 * against which we should perform backtracking, as affected by fence
586 * operations. This includes pairs of potentially-synchronizing actions which
587 * occur due to fence-acquire or fence-release, and hence should be explored in
588 * the opposite execution order.
590 * @param act The current action
591 * @return The most recent action which conflicts with act due to fences
593 ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const
595 /* Only perform release/acquire fence backtracking for stores */
596 if (!act->is_write())
599 /* Find a fence-release (or, act is a release) */
600 ModelAction *last_release;
601 if (act->is_release())
604 last_release = get_last_fence_release(act->get_tid());
608 /* Skip past the release */
609 action_list_t *list = action_trace;
610 action_list_t::reverse_iterator rit;
611 for (rit = list->rbegin(); rit != list->rend(); rit++)
612 if (*rit == last_release)
614 ASSERT(rit != list->rend());
619 * load --sb-> fence-acquire */
620 std::vector< ModelAction *, ModelAlloc<ModelAction *> > acquire_fences(get_num_threads(), NULL);
621 std::vector< ModelAction *, ModelAlloc<ModelAction *> > prior_loads(get_num_threads(), NULL);
622 bool found_acquire_fences = false;
623 for ( ; rit != list->rend(); rit++) {
624 ModelAction *prev = *rit;
625 if (act->same_thread(prev))
628 int tid = id_to_int(prev->get_tid());
630 if (prev->is_read() && act->same_var(prev)) {
631 if (prev->is_acquire()) {
632 /* Found most recent load-acquire, don't need
633 * to search for more fences */
634 if (!found_acquire_fences)
637 prior_loads[tid] = prev;
640 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
641 found_acquire_fences = true;
642 acquire_fences[tid] = prev;
646 ModelAction *latest_backtrack = NULL;
647 for (unsigned int i = 0; i < acquire_fences.size(); i++)
648 if (acquire_fences[i] && prior_loads[i])
649 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
650 latest_backtrack = acquire_fences[i];
651 return latest_backtrack;
655 * @brief Find the last backtracking conflict for a ModelAction
657 * This function performs the search for the most recent conflicting action
658 * against which we should perform backtracking. This primary includes pairs of
659 * synchronizing actions which should be explored in the opposite execution
662 * @param act The current action
663 * @return The most recent action which conflicts with act
665 ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const
667 switch (act->get_type()) {
668 /* case ATOMIC_FENCE: fences don't directly cause backtracking */
672 ModelAction *ret = NULL;
674 /* linear search: from most recent to oldest */
675 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
676 action_list_t::reverse_iterator rit;
677 for (rit = list->rbegin(); rit != list->rend(); rit++) {
678 ModelAction *prev = *rit;
679 if (prev->could_synchronize_with(act)) {
685 ModelAction *ret2 = get_last_fence_conflict(act);
695 case ATOMIC_TRYLOCK: {
696 /* linear search: from most recent to oldest */
697 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
698 action_list_t::reverse_iterator rit;
699 for (rit = list->rbegin(); rit != list->rend(); rit++) {
700 ModelAction *prev = *rit;
701 if (act->is_conflicting_lock(prev))
706 case ATOMIC_UNLOCK: {
707 /* linear search: from most recent to oldest */
708 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
709 action_list_t::reverse_iterator rit;
710 for (rit = list->rbegin(); rit != list->rend(); rit++) {
711 ModelAction *prev = *rit;
712 if (!act->same_thread(prev) && prev->is_failed_trylock())
718 /* linear search: from most recent to oldest */
719 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
720 action_list_t::reverse_iterator rit;
721 for (rit = list->rbegin(); rit != list->rend(); rit++) {
722 ModelAction *prev = *rit;
723 if (!act->same_thread(prev) && prev->is_failed_trylock())
725 if (!act->same_thread(prev) && prev->is_notify())
731 case ATOMIC_NOTIFY_ALL:
732 case ATOMIC_NOTIFY_ONE: {
733 /* linear search: from most recent to oldest */
734 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
735 action_list_t::reverse_iterator rit;
736 for (rit = list->rbegin(); rit != list->rend(); rit++) {
737 ModelAction *prev = *rit;
738 if (!act->same_thread(prev) && prev->is_wait())
749 /** This method finds backtracking points where we should try to
750 * reorder the parameter ModelAction against.
752 * @param the ModelAction to find backtracking points for.
754 void ModelChecker::set_backtracking(ModelAction *act)
756 Thread *t = get_thread(act);
757 ModelAction *prev = get_last_conflict(act);
761 Node *node = prev->get_node()->get_parent();
763 int low_tid, high_tid;
764 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
765 low_tid = id_to_int(act->get_tid());
766 high_tid = low_tid + 1;
769 high_tid = get_num_threads();
772 for (int i = low_tid; i < high_tid; i++) {
773 thread_id_t tid = int_to_id(i);
775 /* Make sure this thread can be enabled here. */
776 if (i >= node->get_num_threads())
779 /* Don't backtrack into a point where the thread is disabled or sleeping. */
780 if (node->enabled_status(tid) != THREAD_ENABLED)
783 /* Check if this has been explored already */
784 if (node->has_been_explored(tid))
787 /* See if fairness allows */
788 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
790 for (int t = 0; t < node->get_num_threads(); t++) {
791 thread_id_t tother = int_to_id(t);
792 if (node->is_enabled(tother) && node->has_priority(tother)) {
800 /* Cache the latest backtracking point */
801 set_latest_backtrack(prev);
803 /* If this is a new backtracking point, mark the tree */
804 if (!node->set_backtrack(tid))
806 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
807 id_to_int(prev->get_tid()),
808 id_to_int(t->get_id()));
817 * @brief Cache the a backtracking point as the "most recent", if eligible
819 * Note that this does not prepare the NodeStack for this backtracking
820 * operation, it only caches the action on a per-execution basis
822 * @param act The operation at which we should explore a different next action
823 * (i.e., backtracking point)
824 * @return True, if this action is now the most recent backtracking point;
827 bool ModelChecker::set_latest_backtrack(ModelAction *act)
829 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
830 priv->next_backtrack = act;
837 * Returns last backtracking point. The model checker will explore a different
838 * path for this point in the next execution.
839 * @return The ModelAction at which the next execution should diverge.
841 ModelAction * ModelChecker::get_next_backtrack()
843 ModelAction *next = priv->next_backtrack;
844 priv->next_backtrack = NULL;
849 * Processes a read model action.
850 * @param curr is the read model action to process.
851 * @return True if processing this read updates the mo_graph.
853 bool ModelChecker::process_read(ModelAction *curr)
855 Node *node = curr->get_node();
856 uint64_t value = VALUE_NONE;
858 bool updated = false;
859 switch (node->get_read_from_status()) {
860 case READ_FROM_PAST: {
861 const ModelAction *rf = node->get_read_from_past();
864 mo_graph->startChanges();
866 ASSERT(!is_infeasible());
867 if (!check_recency(curr, rf)) {
868 if (node->increment_read_from()) {
869 mo_graph->rollbackChanges();
872 priv->too_many_reads = true;
876 updated = r_modification_order(curr, rf);
877 value = rf->get_value();
879 mo_graph->commitChanges();
880 mo_check_promises(curr, true);
883 case READ_FROM_PROMISE: {
884 Promise *promise = curr->get_node()->get_read_from_promise();
885 promise->add_reader(curr);
886 value = promise->get_value();
887 curr->set_read_from_promise(promise);
888 mo_graph->startChanges();
889 if (!check_recency(curr, promise))
890 priv->too_many_reads = true;
891 updated = r_modification_order(curr, promise);
892 mo_graph->commitChanges();
895 case READ_FROM_FUTURE: {
896 /* Read from future value */
897 struct future_value fv = node->get_future_value();
898 Promise *promise = new Promise(curr, fv);
900 curr->set_read_from_promise(promise);
901 promises->push_back(promise);
902 mo_graph->startChanges();
903 updated = r_modification_order(curr, promise);
904 mo_graph->commitChanges();
910 get_thread(curr)->set_return_value(value);
916 * Processes a lock, trylock, or unlock model action. @param curr is
917 * the read model action to process.
919 * The try lock operation checks whether the lock is taken. If not,
920 * it falls to the normal lock operation case. If so, it returns
923 * The lock operation has already been checked that it is enabled, so
924 * it just grabs the lock and synchronizes with the previous unlock.
926 * The unlock operation has to re-enable all of the threads that are
927 * waiting on the lock.
929 * @return True if synchronization was updated; false otherwise
931 bool ModelChecker::process_mutex(ModelAction *curr)
933 std::mutex *mutex = NULL;
934 struct std::mutex_state *state = NULL;
936 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
937 mutex = (std::mutex *)curr->get_location();
938 state = mutex->get_state();
939 } else if (curr->is_wait()) {
940 mutex = (std::mutex *)curr->get_value();
941 state = mutex->get_state();
944 switch (curr->get_type()) {
945 case ATOMIC_TRYLOCK: {
946 bool success = !state->islocked;
947 curr->set_try_lock(success);
949 get_thread(curr)->set_return_value(0);
952 get_thread(curr)->set_return_value(1);
954 //otherwise fall into the lock case
956 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
957 assert_bug("Lock access before initialization");
958 state->islocked = true;
959 ModelAction *unlock = get_last_unlock(curr);
960 //synchronize with the previous unlock statement
961 if (unlock != NULL) {
962 curr->synchronize_with(unlock);
967 case ATOMIC_UNLOCK: {
969 state->islocked = false;
970 //wake up the other threads
971 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
972 //activate all the waiting threads
973 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
974 scheduler->wake(get_thread(*rit));
981 state->islocked = false;
982 //wake up the other threads
983 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
984 //activate all the waiting threads
985 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
986 scheduler->wake(get_thread(*rit));
989 //check whether we should go to sleep or not...simulate spurious failures
990 if (curr->get_node()->get_misc() == 0) {
991 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
993 scheduler->sleep(get_thread(curr));
997 case ATOMIC_NOTIFY_ALL: {
998 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
999 //activate all the waiting threads
1000 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
1001 scheduler->wake(get_thread(*rit));
1006 case ATOMIC_NOTIFY_ONE: {
1007 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
1008 int wakeupthread = curr->get_node()->get_misc();
1009 action_list_t::iterator it = waiters->begin();
1010 advance(it, wakeupthread);
1011 scheduler->wake(get_thread(*it));
1022 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
1024 /* Do more ambitious checks now that mo is more complete */
1025 if (mo_may_allow(writer, reader)) {
1026 Node *node = reader->get_node();
1028 /* Find an ancestor thread which exists at the time of the reader */
1029 Thread *write_thread = get_thread(writer);
1030 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
1031 write_thread = write_thread->get_parent();
1033 struct future_value fv = {
1034 writer->get_write_value(),
1035 writer->get_seq_number() + params.maxfuturedelay,
1036 write_thread->get_id(),
1038 if (node->add_future_value(fv))
1039 set_latest_backtrack(reader);
1044 * Process a write ModelAction
1045 * @param curr The ModelAction to process
1046 * @return True if the mo_graph was updated or promises were resolved
1048 bool ModelChecker::process_write(ModelAction *curr)
1050 /* Readers to which we may send our future value */
1051 std::vector< ModelAction *, ModelAlloc<ModelAction *> > send_fv;
1053 bool updated_mod_order = w_modification_order(curr, &send_fv);
1054 int promise_idx = get_promise_to_resolve(curr);
1055 const ModelAction *earliest_promise_reader;
1056 bool updated_promises = false;
1058 if (promise_idx >= 0) {
1059 earliest_promise_reader = (*promises)[promise_idx]->get_reader(0);
1060 updated_promises = resolve_promise(curr, promise_idx);
1062 earliest_promise_reader = NULL;
1064 /* Don't send future values to reads after the Promise we resolve */
1065 for (unsigned int i = 0; i < send_fv.size(); i++) {
1066 ModelAction *read = send_fv[i];
1067 if (!earliest_promise_reader || *read < *earliest_promise_reader)
1068 futurevalues->push_back(PendingFutureValue(curr, read));
1071 if (promises->size() == 0) {
1072 for (unsigned int i = 0; i < futurevalues->size(); i++) {
1073 struct PendingFutureValue pfv = (*futurevalues)[i];
1074 add_future_value(pfv.writer, pfv.act);
1076 futurevalues->clear();
1079 mo_graph->commitChanges();
1080 mo_check_promises(curr, false);
1082 get_thread(curr)->set_return_value(VALUE_NONE);
1083 return updated_mod_order || updated_promises;
1087 * Process a fence ModelAction
1088 * @param curr The ModelAction to process
1089 * @return True if synchronization was updated
1091 bool ModelChecker::process_fence(ModelAction *curr)
1094 * fence-relaxed: no-op
1095 * fence-release: only log the occurence (not in this function), for
1096 * use in later synchronization
1097 * fence-acquire (this function): search for hypothetical release
1100 bool updated = false;
1101 if (curr->is_acquire()) {
1102 action_list_t *list = action_trace;
1103 action_list_t::reverse_iterator rit;
1104 /* Find X : is_read(X) && X --sb-> curr */
1105 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1106 ModelAction *act = *rit;
1109 if (act->get_tid() != curr->get_tid())
1111 /* Stop at the beginning of the thread */
1112 if (act->is_thread_start())
1114 /* Stop once we reach a prior fence-acquire */
1115 if (act->is_fence() && act->is_acquire())
1117 if (!act->is_read())
1119 /* read-acquire will find its own release sequences */
1120 if (act->is_acquire())
1123 /* Establish hypothetical release sequences */
1124 rel_heads_list_t release_heads;
1125 get_release_seq_heads(curr, act, &release_heads);
1126 for (unsigned int i = 0; i < release_heads.size(); i++)
1127 if (!curr->synchronize_with(release_heads[i]))
1128 set_bad_synchronization();
1129 if (release_heads.size() != 0)
1137 * @brief Process the current action for thread-related activity
1139 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1140 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1141 * synchronization, etc. This function is a no-op for non-THREAD actions
1142 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1144 * @param curr The current action
1145 * @return True if synchronization was updated or a thread completed
1147 bool ModelChecker::process_thread_action(ModelAction *curr)
1149 bool updated = false;
1151 switch (curr->get_type()) {
1152 case THREAD_CREATE: {
1153 thrd_t *thrd = (thrd_t *)curr->get_location();
1154 struct thread_params *params = (struct thread_params *)curr->get_value();
1155 Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
1157 th->set_creation(curr);
1158 /* Promises can be satisfied by children */
1159 for (unsigned int i = 0; i < promises->size(); i++) {
1160 Promise *promise = (*promises)[i];
1161 if (promise->thread_is_available(curr->get_tid()))
1162 promise->add_thread(th->get_id());
1167 Thread *blocking = curr->get_thread_operand();
1168 ModelAction *act = get_last_action(blocking->get_id());
1169 curr->synchronize_with(act);
1170 updated = true; /* trigger rel-seq checks */
1173 case THREAD_FINISH: {
1174 Thread *th = get_thread(curr);
1175 while (!th->wait_list_empty()) {
1176 ModelAction *act = th->pop_wait_list();
1177 scheduler->wake(get_thread(act));
1180 /* Completed thread can't satisfy promises */
1181 for (unsigned int i = 0; i < promises->size(); i++) {
1182 Promise *promise = (*promises)[i];
1183 if (promise->thread_is_available(th->get_id()))
1184 if (promise->eliminate_thread(th->get_id()))
1185 priv->failed_promise = true;
1187 updated = true; /* trigger rel-seq checks */
1190 case THREAD_START: {
1191 check_promises(curr->get_tid(), NULL, curr->get_cv());
1202 * @brief Process the current action for release sequence fixup activity
1204 * Performs model-checker release sequence fixups for the current action,
1205 * forcing a single pending release sequence to break (with a given, potential
1206 * "loose" write) or to complete (i.e., synchronize). If a pending release
1207 * sequence forms a complete release sequence, then we must perform the fixup
1208 * synchronization, mo_graph additions, etc.
1210 * @param curr The current action; must be a release sequence fixup action
1211 * @param work_queue The work queue to which to add work items as they are
1214 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1216 const ModelAction *write = curr->get_node()->get_relseq_break();
1217 struct release_seq *sequence = pending_rel_seqs->back();
1218 pending_rel_seqs->pop_back();
1220 ModelAction *acquire = sequence->acquire;
1221 const ModelAction *rf = sequence->rf;
1222 const ModelAction *release = sequence->release;
1226 ASSERT(release->same_thread(rf));
1228 if (write == NULL) {
1230 * @todo Forcing a synchronization requires that we set
1231 * modification order constraints. For instance, we can't allow
1232 * a fixup sequence in which two separate read-acquire
1233 * operations read from the same sequence, where the first one
1234 * synchronizes and the other doesn't. Essentially, we can't
1235 * allow any writes to insert themselves between 'release' and
1239 /* Must synchronize */
1240 if (!acquire->synchronize_with(release)) {
1241 set_bad_synchronization();
1244 /* Re-check all pending release sequences */
1245 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1246 /* Re-check act for mo_graph edges */
1247 work_queue->push_back(MOEdgeWorkEntry(acquire));
1249 /* propagate synchronization to later actions */
1250 action_list_t::reverse_iterator rit = action_trace->rbegin();
1251 for (; (*rit) != acquire; rit++) {
1252 ModelAction *propagate = *rit;
1253 if (acquire->happens_before(propagate)) {
1254 propagate->synchronize_with(acquire);
1255 /* Re-check 'propagate' for mo_graph edges */
1256 work_queue->push_back(MOEdgeWorkEntry(propagate));
1260 /* Break release sequence with new edges:
1261 * release --mo--> write --mo--> rf */
1262 mo_graph->addEdge(release, write);
1263 mo_graph->addEdge(write, rf);
1266 /* See if we have realized a data race */
1271 * Initialize the current action by performing one or more of the following
1272 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1273 * in the NodeStack, manipulating backtracking sets, allocating and
1274 * initializing clock vectors, and computing the promises to fulfill.
1276 * @param curr The current action, as passed from the user context; may be
1277 * freed/invalidated after the execution of this function, with a different
1278 * action "returned" its place (pass-by-reference)
1279 * @return True if curr is a newly-explored action; false otherwise
1281 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1283 ModelAction *newcurr;
1285 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1286 newcurr = process_rmw(*curr);
1289 if (newcurr->is_rmw())
1290 compute_promises(newcurr);
1296 (*curr)->set_seq_number(get_next_seq_num());
1298 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1300 /* First restore type and order in case of RMW operation */
1301 if ((*curr)->is_rmwr())
1302 newcurr->copy_typeandorder(*curr);
1304 ASSERT((*curr)->get_location() == newcurr->get_location());
1305 newcurr->copy_from_new(*curr);
1307 /* Discard duplicate ModelAction; use action from NodeStack */
1310 /* Always compute new clock vector */
1311 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1314 return false; /* Action was explored previously */
1318 /* Always compute new clock vector */
1319 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1321 /* Assign most recent release fence */
1322 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1325 * Perform one-time actions when pushing new ModelAction onto
1328 if (newcurr->is_write())
1329 compute_promises(newcurr);
1330 else if (newcurr->is_relseq_fixup())
1331 compute_relseq_breakwrites(newcurr);
1332 else if (newcurr->is_wait())
1333 newcurr->get_node()->set_misc_max(2);
1334 else if (newcurr->is_notify_one()) {
1335 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1337 return true; /* This was a new ModelAction */
1342 * @brief Establish reads-from relation between two actions
1344 * Perform basic operations involved with establishing a concrete rf relation,
1345 * including setting the ModelAction data and checking for release sequences.
1347 * @param act The action that is reading (must be a read)
1348 * @param rf The action from which we are reading (must be a write)
1350 * @return True if this read established synchronization
1352 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1355 act->set_read_from(rf);
1356 if (act->is_acquire()) {
1357 rel_heads_list_t release_heads;
1358 get_release_seq_heads(act, act, &release_heads);
1359 int num_heads = release_heads.size();
1360 for (unsigned int i = 0; i < release_heads.size(); i++)
1361 if (!act->synchronize_with(release_heads[i])) {
1362 set_bad_synchronization();
1365 return num_heads > 0;
1371 * Check promises and eliminate potentially-satisfying threads when a thread is
1372 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1373 * no longer satisfy a promise generated from that thread.
1375 * @param blocker The thread on which a thread is waiting
1376 * @param waiting The waiting thread
1378 void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1380 for (unsigned int i = 0; i < promises->size(); i++) {
1381 Promise *promise = (*promises)[i];
1382 if (!promise->thread_is_available(waiting->get_id()))
1384 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1385 ModelAction *reader = promise->get_reader(j);
1386 if (reader->get_tid() != blocker->get_id())
1388 if (promise->eliminate_thread(waiting->get_id())) {
1389 /* Promise has failed */
1390 priv->failed_promise = true;
1392 /* Only eliminate the 'waiting' thread once */
1400 * @brief Check whether a model action is enabled.
1402 * Checks whether a lock or join operation would be successful (i.e., is the
1403 * lock already locked, or is the joined thread already complete). If not, put
1404 * the action in a waiter list.
1406 * @param curr is the ModelAction to check whether it is enabled.
1407 * @return a bool that indicates whether the action is enabled.
1409 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1410 if (curr->is_lock()) {
1411 std::mutex *lock = (std::mutex *)curr->get_location();
1412 struct std::mutex_state *state = lock->get_state();
1413 if (state->islocked) {
1414 //Stick the action in the appropriate waiting queue
1415 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1418 } else if (curr->get_type() == THREAD_JOIN) {
1419 Thread *blocking = (Thread *)curr->get_location();
1420 if (!blocking->is_complete()) {
1421 blocking->push_wait_list(curr);
1422 thread_blocking_check_promises(blocking, get_thread(curr));
1431 * This is the heart of the model checker routine. It performs model-checking
1432 * actions corresponding to a given "current action." Among other processes, it
1433 * calculates reads-from relationships, updates synchronization clock vectors,
1434 * forms a memory_order constraints graph, and handles replay/backtrack
1435 * execution when running permutations of previously-observed executions.
1437 * @param curr The current action to process
1438 * @return The ModelAction that is actually executed; may be different than
1439 * curr; may be NULL, if the current action is not enabled to run
1441 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1444 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1446 if (!check_action_enabled(curr)) {
1447 /* Make the execution look like we chose to run this action
1448 * much later, when a lock/join can succeed */
1449 get_thread(curr)->set_pending(curr);
1450 scheduler->sleep(get_thread(curr));
1454 bool newly_explored = initialize_curr_action(&curr);
1460 wake_up_sleeping_actions(curr);
1462 /* Add the action to lists before any other model-checking tasks */
1463 if (!second_part_of_rmw)
1464 add_action_to_lists(curr);
1466 /* Build may_read_from set for newly-created actions */
1467 if (newly_explored && curr->is_read())
1468 build_may_read_from(curr);
1470 /* Initialize work_queue with the "current action" work */
1471 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1472 while (!work_queue.empty() && !has_asserted()) {
1473 WorkQueueEntry work = work_queue.front();
1474 work_queue.pop_front();
1476 switch (work.type) {
1477 case WORK_CHECK_CURR_ACTION: {
1478 ModelAction *act = work.action;
1479 bool update = false; /* update this location's release seq's */
1480 bool update_all = false; /* update all release seq's */
1482 if (process_thread_action(curr))
1485 if (act->is_read() && !second_part_of_rmw && process_read(act))
1488 if (act->is_write() && process_write(act))
1491 if (act->is_fence() && process_fence(act))
1494 if (act->is_mutex_op() && process_mutex(act))
1497 if (act->is_relseq_fixup())
1498 process_relseq_fixup(curr, &work_queue);
1501 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1503 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1506 case WORK_CHECK_RELEASE_SEQ:
1507 resolve_release_sequences(work.location, &work_queue);
1509 case WORK_CHECK_MO_EDGES: {
1510 /** @todo Complete verification of work_queue */
1511 ModelAction *act = work.action;
1512 bool updated = false;
1514 if (act->is_read()) {
1515 const ModelAction *rf = act->get_reads_from();
1516 const Promise *promise = act->get_reads_from_promise();
1518 if (r_modification_order(act, rf))
1520 } else if (promise) {
1521 if (r_modification_order(act, promise))
1525 if (act->is_write()) {
1526 if (w_modification_order(act, NULL))
1529 mo_graph->commitChanges();
1532 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1541 check_curr_backtracking(curr);
1542 set_backtracking(curr);
1546 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1548 Node *currnode = curr->get_node();
1549 Node *parnode = currnode->get_parent();
1551 if ((parnode && !parnode->backtrack_empty()) ||
1552 !currnode->misc_empty() ||
1553 !currnode->read_from_empty() ||
1554 !currnode->promise_empty() ||
1555 !currnode->relseq_break_empty()) {
1556 set_latest_backtrack(curr);
1560 bool ModelChecker::promises_expired() const
1562 for (unsigned int i = 0; i < promises->size(); i++) {
1563 Promise *promise = (*promises)[i];
1564 if (promise->get_expiration() < priv->used_sequence_numbers)
1571 * This is the strongest feasibility check available.
1572 * @return whether the current trace (partial or complete) must be a prefix of
1575 bool ModelChecker::isfeasibleprefix() const
1577 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1581 * Print disagnostic information about an infeasible execution
1582 * @param prefix A string to prefix the output with; if NULL, then a default
1583 * message prefix will be provided
1585 void ModelChecker::print_infeasibility(const char *prefix) const
1589 if (mo_graph->checkForCycles())
1590 ptr += sprintf(ptr, "[mo cycle]");
1591 if (priv->failed_promise)
1592 ptr += sprintf(ptr, "[failed promise]");
1593 if (priv->too_many_reads)
1594 ptr += sprintf(ptr, "[too many reads]");
1595 if (priv->no_valid_reads)
1596 ptr += sprintf(ptr, "[no valid reads-from]");
1597 if (priv->bad_synchronization)
1598 ptr += sprintf(ptr, "[bad sw ordering]");
1599 if (promises_expired())
1600 ptr += sprintf(ptr, "[promise expired]");
1601 if (promises->size() != 0)
1602 ptr += sprintf(ptr, "[unresolved promise]");
1604 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1608 * Returns whether the current completed trace is feasible, except for pending
1609 * release sequences.
1611 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1613 return !is_infeasible() && promises->size() == 0;
1617 * Check if the current partial trace is infeasible. Does not check any
1618 * end-of-execution flags, which might rule out the execution. Thus, this is
1619 * useful only for ruling an execution as infeasible.
1620 * @return whether the current partial trace is infeasible.
1622 bool ModelChecker::is_infeasible() const
1624 return mo_graph->checkForCycles() ||
1625 priv->no_valid_reads ||
1626 priv->failed_promise ||
1627 priv->too_many_reads ||
1628 priv->bad_synchronization ||
1632 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1633 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1634 ModelAction *lastread = get_last_action(act->get_tid());
1635 lastread->process_rmw(act);
1636 if (act->is_rmw()) {
1637 if (lastread->get_reads_from())
1638 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1640 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1641 mo_graph->commitChanges();
1647 * A helper function for ModelChecker::check_recency, to check if the current
1648 * thread is able to read from a different write/promise for 'params.maxreads'
1649 * number of steps and if that write/promise should become visible (i.e., is
1650 * ordered later in the modification order). This helps model memory liveness.
1652 * @param curr The current action. Must be a read.
1653 * @param rf The write/promise from which we plan to read
1654 * @param other_rf The write/promise from which we may read
1655 * @return True if we were able to read from other_rf for params.maxreads steps
1657 template <typename T, typename U>
1658 bool ModelChecker::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
1660 /* Need a different write/promise */
1661 if (other_rf->equals(rf))
1664 /* Only look for "newer" writes/promises */
1665 if (!mo_graph->checkReachable(rf, other_rf))
1668 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1669 action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
1670 action_list_t::reverse_iterator rit = list->rbegin();
1671 ASSERT((*rit) == curr);
1672 /* Skip past curr */
1675 /* Does this write/promise work for everyone? */
1676 for (int i = 0; i < params.maxreads; i++, rit++) {
1677 ModelAction *act = *rit;
1678 if (!act->may_read_from(other_rf))
1685 * Checks whether a thread has read from the same write or Promise for too many
1686 * times without seeing the effects of a later write/Promise.
1689 * 1) there must a different write/promise that we could read from,
1690 * 2) we must have read from the same write/promise in excess of maxreads times,
1691 * 3) that other write/promise must have been in the reads_from set for maxreads times, and
1692 * 4) that other write/promise must be mod-ordered after the write/promise we are reading.
1694 * If so, we decide that the execution is no longer feasible.
1696 * @param curr The current action. Must be a read.
1697 * @param rf The ModelAction/Promise from which we might read.
1698 * @return True if the read should succeed; false otherwise
1700 template <typename T>
1701 bool ModelChecker::check_recency(ModelAction *curr, const T *rf) const
1703 if (!params.maxreads)
1706 //NOTE: Next check is just optimization, not really necessary....
1707 if (curr->get_node()->get_read_from_past_size() +
1708 curr->get_node()->get_read_from_promise_size() <= 1)
1711 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1712 int tid = id_to_int(curr->get_tid());
1713 ASSERT(tid < (int)thrd_lists->size());
1714 action_list_t *list = &(*thrd_lists)[tid];
1715 action_list_t::reverse_iterator rit = list->rbegin();
1716 ASSERT((*rit) == curr);
1717 /* Skip past curr */
1720 action_list_t::reverse_iterator ritcopy = rit;
1721 /* See if we have enough reads from the same value */
1722 for (int count = 0; count < params.maxreads; ritcopy++, count++) {
1723 if (ritcopy == list->rend())
1725 ModelAction *act = *ritcopy;
1726 if (!act->is_read())
1728 if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
1730 if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
1732 if (act->get_node()->get_read_from_past_size() +
1733 act->get_node()->get_read_from_promise_size() <= 1)
1736 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1737 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1738 if (should_read_instead(curr, rf, write))
1739 return false; /* liveness failure */
1741 for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
1742 const Promise *promise = curr->get_node()->get_read_from_promise(i);
1743 if (should_read_instead(curr, rf, promise))
1744 return false; /* liveness failure */
1750 * Updates the mo_graph with the constraints imposed from the current
1753 * Basic idea is the following: Go through each other thread and find
1754 * the last action that happened before our read. Two cases:
1756 * (1) The action is a write => that write must either occur before
1757 * the write we read from or be the write we read from.
1759 * (2) The action is a read => the write that that action read from
1760 * must occur before the write we read from or be the same write.
1762 * @param curr The current action. Must be a read.
1763 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1764 * @return True if modification order edges were added; false otherwise
1766 template <typename rf_type>
1767 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1769 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1772 ASSERT(curr->is_read());
1774 /* Last SC fence in the current thread */
1775 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1777 /* Iterate over all threads */
1778 for (i = 0; i < thrd_lists->size(); i++) {
1779 /* Last SC fence in thread i */
1780 ModelAction *last_sc_fence_thread_local = NULL;
1781 if (int_to_id((int)i) != curr->get_tid())
1782 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1784 /* Last SC fence in thread i, before last SC fence in current thread */
1785 ModelAction *last_sc_fence_thread_before = NULL;
1786 if (last_sc_fence_local)
1787 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1789 /* Iterate over actions in thread, starting from most recent */
1790 action_list_t *list = &(*thrd_lists)[i];
1791 action_list_t::reverse_iterator rit;
1792 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1793 ModelAction *act = *rit;
1795 if (act->is_write() && !act->equals(rf) && act != curr) {
1796 /* C++, Section 29.3 statement 5 */
1797 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1798 *act < *last_sc_fence_thread_local) {
1799 added = mo_graph->addEdge(act, rf) || added;
1802 /* C++, Section 29.3 statement 4 */
1803 else if (act->is_seqcst() && last_sc_fence_local &&
1804 *act < *last_sc_fence_local) {
1805 added = mo_graph->addEdge(act, rf) || added;
1808 /* C++, Section 29.3 statement 6 */
1809 else if (last_sc_fence_thread_before &&
1810 *act < *last_sc_fence_thread_before) {
1811 added = mo_graph->addEdge(act, rf) || added;
1817 * Include at most one act per-thread that "happens
1818 * before" curr. Don't consider reflexively.
1820 if (act->happens_before(curr) && act != curr) {
1821 if (act->is_write()) {
1822 if (!act->equals(rf)) {
1823 added = mo_graph->addEdge(act, rf) || added;
1826 const ModelAction *prevrf = act->get_reads_from();
1827 const Promise *prevrf_promise = act->get_reads_from_promise();
1829 if (!prevrf->equals(rf))
1830 added = mo_graph->addEdge(prevrf, rf) || added;
1831 } else if (!prevrf_promise->equals(rf)) {
1832 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1841 * All compatible, thread-exclusive promises must be ordered after any
1842 * concrete loads from the same thread
1844 for (unsigned int i = 0; i < promises->size(); i++)
1845 if ((*promises)[i]->is_compatible_exclusive(curr))
1846 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1852 * Updates the mo_graph with the constraints imposed from the current write.
1854 * Basic idea is the following: Go through each other thread and find
1855 * the lastest action that happened before our write. Two cases:
1857 * (1) The action is a write => that write must occur before
1860 * (2) The action is a read => the write that that action read from
1861 * must occur before the current write.
1863 * This method also handles two other issues:
1865 * (I) Sequential Consistency: Making sure that if the current write is
1866 * seq_cst, that it occurs after the previous seq_cst write.
1868 * (II) Sending the write back to non-synchronizing reads.
1870 * @param curr The current action. Must be a write.
1871 * @param send_fv A vector for stashing reads to which we may pass our future
1872 * value. If NULL, then don't record any future values.
1873 * @return True if modification order edges were added; false otherwise
1875 bool ModelChecker::w_modification_order(ModelAction *curr, std::vector< ModelAction *, ModelAlloc<ModelAction *> > *send_fv)
1877 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1880 ASSERT(curr->is_write());
1882 if (curr->is_seqcst()) {
1883 /* We have to at least see the last sequentially consistent write,
1884 so we are initialized. */
1885 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1886 if (last_seq_cst != NULL) {
1887 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1891 /* Last SC fence in the current thread */
1892 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1894 /* Iterate over all threads */
1895 for (i = 0; i < thrd_lists->size(); i++) {
1896 /* Last SC fence in thread i, before last SC fence in current thread */
1897 ModelAction *last_sc_fence_thread_before = NULL;
1898 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1899 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1901 /* Iterate over actions in thread, starting from most recent */
1902 action_list_t *list = &(*thrd_lists)[i];
1903 action_list_t::reverse_iterator rit;
1904 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1905 ModelAction *act = *rit;
1908 * 1) If RMW and it actually read from something, then we
1909 * already have all relevant edges, so just skip to next
1912 * 2) If RMW and it didn't read from anything, we should
1913 * whatever edge we can get to speed up convergence.
1915 * 3) If normal write, we need to look at earlier actions, so
1916 * continue processing list.
1918 if (curr->is_rmw()) {
1919 if (curr->get_reads_from() != NULL)
1927 /* C++, Section 29.3 statement 7 */
1928 if (last_sc_fence_thread_before && act->is_write() &&
1929 *act < *last_sc_fence_thread_before) {
1930 added = mo_graph->addEdge(act, curr) || added;
1935 * Include at most one act per-thread that "happens
1938 if (act->happens_before(curr)) {
1940 * Note: if act is RMW, just add edge:
1942 * The following edge should be handled elsewhere:
1943 * readfrom(act) --mo--> act
1945 if (act->is_write())
1946 added = mo_graph->addEdge(act, curr) || added;
1947 else if (act->is_read()) {
1948 //if previous read accessed a null, just keep going
1949 if (act->get_reads_from() == NULL)
1951 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1954 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1955 !act->same_thread(curr)) {
1956 /* We have an action that:
1957 (1) did not happen before us
1958 (2) is a read and we are a write
1959 (3) cannot synchronize with us
1960 (4) is in a different thread
1962 that read could potentially read from our write. Note that
1963 these checks are overly conservative at this point, we'll
1964 do more checks before actually removing the
1968 if (send_fv && thin_air_constraint_may_allow(curr, act)) {
1969 if (!is_infeasible())
1970 send_fv->push_back(act);
1971 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1972 add_future_value(curr, act);
1979 * All compatible, thread-exclusive promises must be ordered after any
1980 * concrete stores to the same thread, or else they can be merged with
1983 for (unsigned int i = 0; i < promises->size(); i++)
1984 if ((*promises)[i]->is_compatible_exclusive(curr))
1985 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1990 /** Arbitrary reads from the future are not allowed. Section 29.3
1991 * part 9 places some constraints. This method checks one result of constraint
1992 * constraint. Others require compiler support. */
1993 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1995 if (!writer->is_rmw())
1998 if (!reader->is_rmw())
2001 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
2002 if (search == reader)
2004 if (search->get_tid() == reader->get_tid() &&
2005 search->happens_before(reader))
2013 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
2014 * some constraints. This method checks one the following constraint (others
2015 * require compiler support):
2017 * If X --hb-> Y --mo-> Z, then X should not read from Z.
2019 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
2021 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
2023 /* Iterate over all threads */
2024 for (i = 0; i < thrd_lists->size(); i++) {
2025 const ModelAction *write_after_read = NULL;
2027 /* Iterate over actions in thread, starting from most recent */
2028 action_list_t *list = &(*thrd_lists)[i];
2029 action_list_t::reverse_iterator rit;
2030 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2031 ModelAction *act = *rit;
2033 /* Don't disallow due to act == reader */
2034 if (!reader->happens_before(act) || reader == act)
2036 else if (act->is_write())
2037 write_after_read = act;
2038 else if (act->is_read() && act->get_reads_from() != NULL)
2039 write_after_read = act->get_reads_from();
2042 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
2049 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
2050 * The ModelAction under consideration is expected to be taking part in
2051 * release/acquire synchronization as an object of the "reads from" relation.
2052 * Note that this can only provide release sequence support for RMW chains
2053 * which do not read from the future, as those actions cannot be traced until
2054 * their "promise" is fulfilled. Similarly, we may not even establish the
2055 * presence of a release sequence with certainty, as some modification order
2056 * constraints may be decided further in the future. Thus, this function
2057 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
2058 * and a boolean representing certainty.
2060 * @param rf The action that might be part of a release sequence. Must be a
2062 * @param release_heads A pass-by-reference style return parameter. After
2063 * execution of this function, release_heads will contain the heads of all the
2064 * relevant release sequences, if any exists with certainty
2065 * @param pending A pass-by-reference style return parameter which is only used
2066 * when returning false (i.e., uncertain). Returns most information regarding
2067 * an uncertain release sequence, including any write operations that might
2068 * break the sequence.
2069 * @return true, if the ModelChecker is certain that release_heads is complete;
2072 bool ModelChecker::release_seq_heads(const ModelAction *rf,
2073 rel_heads_list_t *release_heads,
2074 struct release_seq *pending) const
2076 /* Only check for release sequences if there are no cycles */
2077 if (mo_graph->checkForCycles())
2080 for ( ; rf != NULL; rf = rf->get_reads_from()) {
2081 ASSERT(rf->is_write());
2083 if (rf->is_release())
2084 release_heads->push_back(rf);
2085 else if (rf->get_last_fence_release())
2086 release_heads->push_back(rf->get_last_fence_release());
2088 break; /* End of RMW chain */
2090 /** @todo Need to be smarter here... In the linux lock
2091 * example, this will run to the beginning of the program for
2093 /** @todo The way to be smarter here is to keep going until 1
2094 * thread has a release preceded by an acquire and you've seen
2097 /* acq_rel RMW is a sufficient stopping condition */
2098 if (rf->is_acquire() && rf->is_release())
2099 return true; /* complete */
2102 /* read from future: need to settle this later */
2104 return false; /* incomplete */
2107 if (rf->is_release())
2108 return true; /* complete */
2110 /* else relaxed write
2111 * - check for fence-release in the same thread (29.8, stmt. 3)
2112 * - check modification order for contiguous subsequence
2113 * -> rf must be same thread as release */
2115 const ModelAction *fence_release = rf->get_last_fence_release();
2116 /* Synchronize with a fence-release unconditionally; we don't need to
2117 * find any more "contiguous subsequence..." for it */
2119 release_heads->push_back(fence_release);
2121 int tid = id_to_int(rf->get_tid());
2122 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
2123 action_list_t *list = &(*thrd_lists)[tid];
2124 action_list_t::const_reverse_iterator rit;
2126 /* Find rf in the thread list */
2127 rit = std::find(list->rbegin(), list->rend(), rf);
2128 ASSERT(rit != list->rend());
2130 /* Find the last {write,fence}-release */
2131 for (; rit != list->rend(); rit++) {
2132 if (fence_release && *(*rit) < *fence_release)
2134 if ((*rit)->is_release())
2137 if (rit == list->rend()) {
2138 /* No write-release in this thread */
2139 return true; /* complete */
2140 } else if (fence_release && *(*rit) < *fence_release) {
2141 /* The fence-release is more recent (and so, "stronger") than
2142 * the most recent write-release */
2143 return true; /* complete */
2144 } /* else, need to establish contiguous release sequence */
2145 ModelAction *release = *rit;
2147 ASSERT(rf->same_thread(release));
2149 pending->writes.clear();
2151 bool certain = true;
2152 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2153 if (id_to_int(rf->get_tid()) == (int)i)
2155 list = &(*thrd_lists)[i];
2157 /* Can we ensure no future writes from this thread may break
2158 * the release seq? */
2159 bool future_ordered = false;
2161 ModelAction *last = get_last_action(int_to_id(i));
2162 Thread *th = get_thread(int_to_id(i));
2163 if ((last && rf->happens_before(last)) ||
2166 future_ordered = true;
2168 ASSERT(!th->is_model_thread() || future_ordered);
2170 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2171 const ModelAction *act = *rit;
2172 /* Reach synchronization -> this thread is complete */
2173 if (act->happens_before(release))
2175 if (rf->happens_before(act)) {
2176 future_ordered = true;
2180 /* Only non-RMW writes can break release sequences */
2181 if (!act->is_write() || act->is_rmw())
2184 /* Check modification order */
2185 if (mo_graph->checkReachable(rf, act)) {
2186 /* rf --mo--> act */
2187 future_ordered = true;
2190 if (mo_graph->checkReachable(act, release))
2191 /* act --mo--> release */
2193 if (mo_graph->checkReachable(release, act) &&
2194 mo_graph->checkReachable(act, rf)) {
2195 /* release --mo-> act --mo--> rf */
2196 return true; /* complete */
2198 /* act may break release sequence */
2199 pending->writes.push_back(act);
2202 if (!future_ordered)
2203 certain = false; /* This thread is uncertain */
2207 release_heads->push_back(release);
2208 pending->writes.clear();
2210 pending->release = release;
2217 * An interface for getting the release sequence head(s) with which a
2218 * given ModelAction must synchronize. This function only returns a non-empty
2219 * result when it can locate a release sequence head with certainty. Otherwise,
2220 * it may mark the internal state of the ModelChecker so that it will handle
2221 * the release sequence at a later time, causing @a acquire to update its
2222 * synchronization at some later point in execution.
2224 * @param acquire The 'acquire' action that may synchronize with a release
2226 * @param read The read action that may read from a release sequence; this may
2227 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2228 * when 'acquire' is a fence-acquire)
2229 * @param release_heads A pass-by-reference return parameter. Will be filled
2230 * with the head(s) of the release sequence(s), if they exists with certainty.
2231 * @see ModelChecker::release_seq_heads
2233 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2234 ModelAction *read, rel_heads_list_t *release_heads)
2236 const ModelAction *rf = read->get_reads_from();
2237 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2238 sequence->acquire = acquire;
2239 sequence->read = read;
2241 if (!release_seq_heads(rf, release_heads, sequence)) {
2242 /* add act to 'lazy checking' list */
2243 pending_rel_seqs->push_back(sequence);
2245 snapshot_free(sequence);
2250 * Attempt to resolve all stashed operations that might synchronize with a
2251 * release sequence for a given location. This implements the "lazy" portion of
2252 * determining whether or not a release sequence was contiguous, since not all
2253 * modification order information is present at the time an action occurs.
2255 * @param location The location/object that should be checked for release
2256 * sequence resolutions. A NULL value means to check all locations.
2257 * @param work_queue The work queue to which to add work items as they are
2259 * @return True if any updates occurred (new synchronization, new mo_graph
2262 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2264 bool updated = false;
2265 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2266 while (it != pending_rel_seqs->end()) {
2267 struct release_seq *pending = *it;
2268 ModelAction *acquire = pending->acquire;
2269 const ModelAction *read = pending->read;
2271 /* Only resolve sequences on the given location, if provided */
2272 if (location && read->get_location() != location) {
2277 const ModelAction *rf = read->get_reads_from();
2278 rel_heads_list_t release_heads;
2280 complete = release_seq_heads(rf, &release_heads, pending);
2281 for (unsigned int i = 0; i < release_heads.size(); i++) {
2282 if (!acquire->has_synchronized_with(release_heads[i])) {
2283 if (acquire->synchronize_with(release_heads[i]))
2286 set_bad_synchronization();
2291 /* Re-check all pending release sequences */
2292 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2293 /* Re-check read-acquire for mo_graph edges */
2294 if (acquire->is_read())
2295 work_queue->push_back(MOEdgeWorkEntry(acquire));
2297 /* propagate synchronization to later actions */
2298 action_list_t::reverse_iterator rit = action_trace->rbegin();
2299 for (; (*rit) != acquire; rit++) {
2300 ModelAction *propagate = *rit;
2301 if (acquire->happens_before(propagate)) {
2302 propagate->synchronize_with(acquire);
2303 /* Re-check 'propagate' for mo_graph edges */
2304 work_queue->push_back(MOEdgeWorkEntry(propagate));
2309 it = pending_rel_seqs->erase(it);
2310 snapshot_free(pending);
2316 // If we resolved promises or data races, see if we have realized a data race.
2323 * Performs various bookkeeping operations for the current ModelAction. For
2324 * instance, adds action to the per-object, per-thread action vector and to the
2325 * action trace list of all thread actions.
2327 * @param act is the ModelAction to add.
2329 void ModelChecker::add_action_to_lists(ModelAction *act)
2331 int tid = id_to_int(act->get_tid());
2332 ModelAction *uninit = NULL;
2334 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2335 if (list->empty() && act->is_atomic_var()) {
2336 uninit = new_uninitialized_action(act->get_location());
2337 uninit_id = id_to_int(uninit->get_tid());
2338 list->push_back(uninit);
2340 list->push_back(act);
2342 action_trace->push_back(act);
2344 action_trace->push_front(uninit);
2346 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2347 if (tid >= (int)vec->size())
2348 vec->resize(priv->next_thread_id);
2349 (*vec)[tid].push_back(act);
2351 (*vec)[uninit_id].push_front(uninit);
2353 if ((int)thrd_last_action->size() <= tid)
2354 thrd_last_action->resize(get_num_threads());
2355 (*thrd_last_action)[tid] = act;
2357 (*thrd_last_action)[uninit_id] = uninit;
2359 if (act->is_fence() && act->is_release()) {
2360 if ((int)thrd_last_fence_release->size() <= tid)
2361 thrd_last_fence_release->resize(get_num_threads());
2362 (*thrd_last_fence_release)[tid] = act;
2365 if (act->is_wait()) {
2366 void *mutex_loc = (void *) act->get_value();
2367 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2369 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2370 if (tid >= (int)vec->size())
2371 vec->resize(priv->next_thread_id);
2372 (*vec)[tid].push_back(act);
2377 * @brief Get the last action performed by a particular Thread
2378 * @param tid The thread ID of the Thread in question
2379 * @return The last action in the thread
2381 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2383 int threadid = id_to_int(tid);
2384 if (threadid < (int)thrd_last_action->size())
2385 return (*thrd_last_action)[id_to_int(tid)];
2391 * @brief Get the last fence release performed by a particular Thread
2392 * @param tid The thread ID of the Thread in question
2393 * @return The last fence release in the thread, if one exists; NULL otherwise
2395 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2397 int threadid = id_to_int(tid);
2398 if (threadid < (int)thrd_last_fence_release->size())
2399 return (*thrd_last_fence_release)[id_to_int(tid)];
2405 * Gets the last memory_order_seq_cst write (in the total global sequence)
2406 * performed on a particular object (i.e., memory location), not including the
2408 * @param curr The current ModelAction; also denotes the object location to
2410 * @return The last seq_cst write
2412 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2414 void *location = curr->get_location();
2415 action_list_t *list = get_safe_ptr_action(obj_map, location);
2416 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2417 action_list_t::reverse_iterator rit;
2418 for (rit = list->rbegin(); rit != list->rend(); rit++)
2419 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2425 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2426 * performed in a particular thread, prior to a particular fence.
2427 * @param tid The ID of the thread to check
2428 * @param before_fence The fence from which to begin the search; if NULL, then
2429 * search for the most recent fence in the thread.
2430 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2432 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2434 /* All fences should have NULL location */
2435 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2436 action_list_t::reverse_iterator rit = list->rbegin();
2439 for (; rit != list->rend(); rit++)
2440 if (*rit == before_fence)
2443 ASSERT(*rit == before_fence);
2447 for (; rit != list->rend(); rit++)
2448 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2454 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2455 * location). This function identifies the mutex according to the current
2456 * action, which is presumed to perform on the same mutex.
2457 * @param curr The current ModelAction; also denotes the object location to
2459 * @return The last unlock operation
2461 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2463 void *location = curr->get_location();
2464 action_list_t *list = get_safe_ptr_action(obj_map, location);
2465 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2466 action_list_t::reverse_iterator rit;
2467 for (rit = list->rbegin(); rit != list->rend(); rit++)
2468 if ((*rit)->is_unlock() || (*rit)->is_wait())
2473 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2475 ModelAction *parent = get_last_action(tid);
2477 parent = get_thread(tid)->get_creation();
2482 * Returns the clock vector for a given thread.
2483 * @param tid The thread whose clock vector we want
2484 * @return Desired clock vector
2486 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2488 return get_parent_action(tid)->get_cv();
2492 * @brief Find the promise, if any to resolve for the current action
2493 * @param curr The current ModelAction. Should be a write.
2494 * @return The (non-negative) index for the Promise to resolve, if any;
2497 int ModelChecker::get_promise_to_resolve(const ModelAction *curr) const
2499 for (unsigned int i = 0; i < promises->size(); i++)
2500 if (curr->get_node()->get_promise(i))
2506 * Resolve a Promise with a current write.
2507 * @param write The ModelAction that is fulfilling Promises
2508 * @param promise_idx The index corresponding to the promise
2509 * @return True if the Promise was successfully resolved; false otherwise
2511 bool ModelChecker::resolve_promise(ModelAction *write, unsigned int promise_idx)
2513 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2514 Promise *promise = (*promises)[promise_idx];
2516 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2517 ModelAction *read = promise->get_reader(i);
2518 read_from(read, write);
2519 actions_to_check.push_back(read);
2521 /* Make sure the promise's value matches the write's value */
2522 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2523 if (!mo_graph->resolvePromise(promise, write))
2524 priv->failed_promise = true;
2526 promises->erase(promises->begin() + promise_idx);
2529 //Check whether reading these writes has made threads unable to
2532 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2533 ModelAction *read = actions_to_check[i];
2534 mo_check_promises(read, true);
2541 * Compute the set of promises that could potentially be satisfied by this
2542 * action. Note that the set computation actually appears in the Node, not in
2544 * @param curr The ModelAction that may satisfy promises
2546 void ModelChecker::compute_promises(ModelAction *curr)
2548 for (unsigned int i = 0; i < promises->size(); i++) {
2549 Promise *promise = (*promises)[i];
2550 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2553 bool satisfy = true;
2554 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2555 const ModelAction *act = promise->get_reader(j);
2556 if (act->happens_before(curr) ||
2557 act->could_synchronize_with(curr)) {
2563 curr->get_node()->set_promise(i);
2567 /** Checks promises in response to change in ClockVector Threads. */
2568 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2570 for (unsigned int i = 0; i < promises->size(); i++) {
2571 Promise *promise = (*promises)[i];
2572 if (!promise->thread_is_available(tid))
2574 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2575 const ModelAction *act = promise->get_reader(j);
2576 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2577 merge_cv->synchronized_since(act)) {
2578 if (promise->eliminate_thread(tid)) {
2579 /* Promise has failed */
2580 priv->failed_promise = true;
2588 void ModelChecker::check_promises_thread_disabled()
2590 for (unsigned int i = 0; i < promises->size(); i++) {
2591 Promise *promise = (*promises)[i];
2592 if (promise->has_failed()) {
2593 priv->failed_promise = true;
2600 * @brief Checks promises in response to addition to modification order for
2603 * We test whether threads are still available for satisfying promises after an
2604 * addition to our modification order constraints. Those that are unavailable
2605 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2606 * that promise has failed.
2608 * @param act The ModelAction which updated the modification order
2609 * @param is_read_check Should be true if act is a read and we must check for
2610 * updates to the store from which it read (there is a distinction here for
2611 * RMW's, which are both a load and a store)
2613 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2615 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2617 for (unsigned int i = 0; i < promises->size(); i++) {
2618 Promise *promise = (*promises)[i];
2620 // Is this promise on the same location?
2621 if (!promise->same_location(write))
2624 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2625 const ModelAction *pread = promise->get_reader(j);
2626 if (!pread->happens_before(act))
2628 if (mo_graph->checkPromise(write, promise)) {
2629 priv->failed_promise = true;
2635 // Don't do any lookups twice for the same thread
2636 if (!promise->thread_is_available(act->get_tid()))
2639 if (mo_graph->checkReachable(promise, write)) {
2640 if (mo_graph->checkPromise(write, promise)) {
2641 priv->failed_promise = true;
2649 * Compute the set of writes that may break the current pending release
2650 * sequence. This information is extracted from previou release sequence
2653 * @param curr The current ModelAction. Must be a release sequence fixup
2656 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2658 if (pending_rel_seqs->empty())
2661 struct release_seq *pending = pending_rel_seqs->back();
2662 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2663 const ModelAction *write = pending->writes[i];
2664 curr->get_node()->add_relseq_break(write);
2667 /* NULL means don't break the sequence; just synchronize */
2668 curr->get_node()->add_relseq_break(NULL);
2672 * Build up an initial set of all past writes that this 'read' action may read
2673 * from, as well as any previously-observed future values that must still be valid.
2675 * @param curr is the current ModelAction that we are exploring; it must be a
2678 void ModelChecker::build_may_read_from(ModelAction *curr)
2680 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2682 ASSERT(curr->is_read());
2684 ModelAction *last_sc_write = NULL;
2686 if (curr->is_seqcst())
2687 last_sc_write = get_last_seq_cst_write(curr);
2689 /* Iterate over all threads */
2690 for (i = 0; i < thrd_lists->size(); i++) {
2691 /* Iterate over actions in thread, starting from most recent */
2692 action_list_t *list = &(*thrd_lists)[i];
2693 action_list_t::reverse_iterator rit;
2694 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2695 ModelAction *act = *rit;
2697 /* Only consider 'write' actions */
2698 if (!act->is_write() || act == curr)
2701 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2702 bool allow_read = true;
2704 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2706 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2710 /* Only add feasible reads */
2711 mo_graph->startChanges();
2712 r_modification_order(curr, act);
2713 if (!is_infeasible())
2714 curr->get_node()->add_read_from_past(act);
2715 mo_graph->rollbackChanges();
2718 /* Include at most one act per-thread that "happens before" curr */
2719 if (act->happens_before(curr))
2724 /* Inherit existing, promised future values */
2725 for (i = 0; i < promises->size(); i++) {
2726 const Promise *promise = (*promises)[i];
2727 const ModelAction *promise_read = promise->get_reader(0);
2728 if (promise_read->same_var(curr)) {
2729 /* Only add feasible future-values */
2730 mo_graph->startChanges();
2731 r_modification_order(curr, promise);
2732 if (!is_infeasible())
2733 curr->get_node()->add_read_from_promise(promise_read);
2734 mo_graph->rollbackChanges();
2738 /* We may find no valid may-read-from only if the execution is doomed */
2739 if (!curr->get_node()->read_from_size()) {
2740 priv->no_valid_reads = true;
2744 if (DBG_ENABLED()) {
2745 model_print("Reached read action:\n");
2747 model_print("Printing read_from_past\n");
2748 curr->get_node()->print_read_from_past();
2749 model_print("End printing read_from_past\n");
2753 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2755 for ( ; write != NULL; write = write->get_reads_from()) {
2756 /* UNINIT actions don't have a Node, and they never sleep */
2757 if (write->is_uninitialized())
2759 Node *prevnode = write->get_node()->get_parent();
2761 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2762 if (write->is_release() && thread_sleep)
2764 if (!write->is_rmw())
2771 * @brief Create a new action representing an uninitialized atomic
2772 * @param location The memory location of the atomic object
2773 * @return A pointer to a new ModelAction
2775 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2777 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2778 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2779 act->create_cv(NULL);
2783 static void print_list(action_list_t *list)
2785 action_list_t::iterator it;
2787 model_print("---------------------------------------------------------------------\n");
2789 unsigned int hash = 0;
2791 for (it = list->begin(); it != list->end(); it++) {
2793 hash = hash^(hash<<3)^((*it)->hash());
2795 model_print("HASH %u\n", hash);
2796 model_print("---------------------------------------------------------------------\n");
2799 #if SUPPORT_MOD_ORDER_DUMP
2800 void ModelChecker::dumpGraph(char *filename) const
2803 sprintf(buffer, "%s.dot", filename);
2804 FILE *file = fopen(buffer, "w");
2805 fprintf(file, "digraph %s {\n", filename);
2806 mo_graph->dumpNodes(file);
2807 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2809 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2810 ModelAction *act = *it;
2811 if (act->is_read()) {
2812 mo_graph->dot_print_node(file, act);
2813 if (act->get_reads_from())
2814 mo_graph->dot_print_edge(file,
2815 act->get_reads_from(),
2817 "label=\"rf\", color=red, weight=2");
2819 mo_graph->dot_print_edge(file,
2820 act->get_reads_from_promise(),
2822 "label=\"rf\", color=red");
2824 if (thread_array[act->get_tid()]) {
2825 mo_graph->dot_print_edge(file,
2826 thread_array[id_to_int(act->get_tid())],
2828 "label=\"sb\", color=blue, weight=400");
2831 thread_array[act->get_tid()] = act;
2833 fprintf(file, "}\n");
2834 model_free(thread_array);
2839 /** @brief Prints an execution trace summary. */
2840 void ModelChecker::print_summary() const
2842 #if SUPPORT_MOD_ORDER_DUMP
2843 char buffername[100];
2844 sprintf(buffername, "exec%04u", stats.num_total);
2845 mo_graph->dumpGraphToFile(buffername);
2846 sprintf(buffername, "graph%04u", stats.num_total);
2847 dumpGraph(buffername);
2850 model_print("Execution %d:", stats.num_total);
2851 if (isfeasibleprefix()) {
2852 if (scheduler->all_threads_sleeping())
2853 model_print(" SLEEP-SET REDUNDANT");
2856 print_infeasibility(" INFEASIBLE");
2857 print_list(action_trace);
2862 * Add a Thread to the system for the first time. Should only be called once
2864 * @param t The Thread to add
2866 void ModelChecker::add_thread(Thread *t)
2868 thread_map->put(id_to_int(t->get_id()), t);
2869 scheduler->add_thread(t);
2873 * Removes a thread from the scheduler.
2874 * @param the thread to remove.
2876 void ModelChecker::remove_thread(Thread *t)
2878 scheduler->remove_thread(t);
2882 * @brief Get a Thread reference by its ID
2883 * @param tid The Thread's ID
2884 * @return A Thread reference
2886 Thread * ModelChecker::get_thread(thread_id_t tid) const
2888 return thread_map->get(id_to_int(tid));
2892 * @brief Get a reference to the Thread in which a ModelAction was executed
2893 * @param act The ModelAction
2894 * @return A Thread reference
2896 Thread * ModelChecker::get_thread(const ModelAction *act) const
2898 return get_thread(act->get_tid());
2902 * @brief Get a Promise's "promise number"
2904 * A "promise number" is an index number that is unique to a promise, valid
2905 * only for a specific snapshot of an execution trace. Promises may come and go
2906 * as they are generated an resolved, so an index only retains meaning for the
2909 * @param promise The Promise to check
2910 * @return The promise index, if the promise still is valid; otherwise -1
2912 int ModelChecker::get_promise_number(const Promise *promise) const
2914 for (unsigned int i = 0; i < promises->size(); i++)
2915 if ((*promises)[i] == promise)
2922 * @brief Check if a Thread is currently enabled
2923 * @param t The Thread to check
2924 * @return True if the Thread is currently enabled
2926 bool ModelChecker::is_enabled(Thread *t) const
2928 return scheduler->is_enabled(t);
2932 * @brief Check if a Thread is currently enabled
2933 * @param tid The ID of the Thread to check
2934 * @return True if the Thread is currently enabled
2936 bool ModelChecker::is_enabled(thread_id_t tid) const
2938 return scheduler->is_enabled(tid);
2942 * Switch from a model-checker context to a user-thread context. This is the
2943 * complement of ModelChecker::switch_to_master and must be called from the
2944 * model-checker context
2946 * @param thread The user-thread to switch to
2948 void ModelChecker::switch_from_master(Thread *thread)
2950 scheduler->set_current_thread(thread);
2951 Thread::swap(&system_context, thread);
2955 * Switch from a user-context to the "master thread" context (a.k.a. system
2956 * context). This switch is made with the intention of exploring a particular
2957 * model-checking action (described by a ModelAction object). Must be called
2958 * from a user-thread context.
2960 * @param act The current action that will be explored. May be NULL only if
2961 * trace is exiting via an assertion (see ModelChecker::set_assert and
2962 * ModelChecker::has_asserted).
2963 * @return Return the value returned by the current action
2965 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2968 Thread *old = thread_current();
2969 ASSERT(!old->get_pending());
2970 old->set_pending(act);
2971 if (Thread::swap(old, &system_context) < 0) {
2972 perror("swap threads");
2975 return old->get_return_value();
2979 * Takes the next step in the execution, if possible.
2980 * @param curr The current step to take
2981 * @return Returns the next Thread to run, if any; NULL if this execution
2984 Thread * ModelChecker::take_step(ModelAction *curr)
2986 Thread *curr_thrd = get_thread(curr);
2987 ASSERT(curr_thrd->get_state() == THREAD_READY);
2989 curr = check_current_action(curr);
2991 /* Infeasible -> don't take any more steps */
2992 if (is_infeasible())
2994 else if (isfeasibleprefix() && have_bug_reports()) {
2999 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
3002 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
3003 scheduler->remove_thread(curr_thrd);
3005 Thread *next_thrd = get_next_thread(curr);
3007 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
3008 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
3013 /** Wrapper to run the user's main function, with appropriate arguments */
3014 void user_main_wrapper(void *)
3016 user_main(model->params.argc, model->params.argv);
3019 /** @brief Run ModelChecker for the user program */
3020 void ModelChecker::run()
3024 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
3029 * Stash next pending action(s) for thread(s). There
3030 * should only need to stash one thread's action--the
3031 * thread which just took a step--plus the first step
3032 * for any newly-created thread
3034 for (unsigned int i = 0; i < get_num_threads(); i++) {
3035 thread_id_t tid = int_to_id(i);
3036 Thread *thr = get_thread(tid);
3037 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
3038 switch_from_master(thr);
3042 /* Catch assertions from prior take_step or from
3043 * between-ModelAction bugs (e.g., data races) */
3047 /* Consume the next action for a Thread */
3048 ModelAction *curr = t->get_pending();
3049 t->set_pending(NULL);
3050 t = take_step(curr);
3051 } while (t && !t->is_model_thread());
3054 * Launch end-of-execution release sequence fixups only when
3055 * the execution is otherwise feasible AND there are:
3057 * (1) pending release sequences
3058 * (2) pending assertions that could be invalidated by a change
3059 * in clock vectors (i.e., data races)
3060 * (3) no pending promises
3062 while (!pending_rel_seqs->empty() &&
3063 is_feasible_prefix_ignore_relseq() &&
3064 !unrealizedraces.empty()) {
3065 model_print("*** WARNING: release sequence fixup action "
3066 "(%zu pending release seuqence(s)) ***\n",
3067 pending_rel_seqs->size());
3068 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
3069 std::memory_order_seq_cst, NULL, VALUE_NONE,
3073 } while (next_execution());
3075 model_print("******* Model-checking complete: *******\n");