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 priv->too_many_reads = true;
869 updated = r_modification_order(curr, rf);
871 if (is_infeasible() && node->increment_read_from()) {
872 mo_graph->rollbackChanges();
873 priv->too_many_reads = false;
877 value = rf->get_value();
879 mo_graph->commitChanges();
880 mo_check_promises(curr, true);
884 case READ_FROM_PROMISE: {
885 Promise *promise = curr->get_node()->get_read_from_promise();
886 promise->add_reader(curr);
887 value = promise->get_value();
888 curr->set_read_from_promise(promise);
889 mo_graph->startChanges();
890 if (!check_recency(curr, promise))
891 priv->too_many_reads = true;
892 updated = r_modification_order(curr, promise);
893 mo_graph->commitChanges();
896 case READ_FROM_FUTURE: {
897 /* Read from future value */
898 struct future_value fv = node->get_future_value();
899 Promise *promise = new Promise(curr, fv);
901 curr->set_read_from_promise(promise);
902 promises->push_back(promise);
903 mo_graph->startChanges();
904 updated = r_modification_order(curr, promise);
905 mo_graph->commitChanges();
911 get_thread(curr)->set_return_value(value);
917 * Processes a lock, trylock, or unlock model action. @param curr is
918 * the read model action to process.
920 * The try lock operation checks whether the lock is taken. If not,
921 * it falls to the normal lock operation case. If so, it returns
924 * The lock operation has already been checked that it is enabled, so
925 * it just grabs the lock and synchronizes with the previous unlock.
927 * The unlock operation has to re-enable all of the threads that are
928 * waiting on the lock.
930 * @return True if synchronization was updated; false otherwise
932 bool ModelChecker::process_mutex(ModelAction *curr)
934 std::mutex *mutex = NULL;
935 struct std::mutex_state *state = NULL;
937 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
938 mutex = (std::mutex *)curr->get_location();
939 state = mutex->get_state();
940 } else if (curr->is_wait()) {
941 mutex = (std::mutex *)curr->get_value();
942 state = mutex->get_state();
945 switch (curr->get_type()) {
946 case ATOMIC_TRYLOCK: {
947 bool success = !state->islocked;
948 curr->set_try_lock(success);
950 get_thread(curr)->set_return_value(0);
953 get_thread(curr)->set_return_value(1);
955 //otherwise fall into the lock case
957 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
958 assert_bug("Lock access before initialization");
959 state->islocked = true;
960 ModelAction *unlock = get_last_unlock(curr);
961 //synchronize with the previous unlock statement
962 if (unlock != NULL) {
963 curr->synchronize_with(unlock);
968 case ATOMIC_UNLOCK: {
970 state->islocked = false;
971 //wake up the other threads
972 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
973 //activate all the waiting threads
974 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
975 scheduler->wake(get_thread(*rit));
982 state->islocked = false;
983 //wake up the other threads
984 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
985 //activate all the waiting threads
986 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
987 scheduler->wake(get_thread(*rit));
990 //check whether we should go to sleep or not...simulate spurious failures
991 if (curr->get_node()->get_misc() == 0) {
992 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
994 scheduler->sleep(get_thread(curr));
998 case ATOMIC_NOTIFY_ALL: {
999 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
1000 //activate all the waiting threads
1001 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
1002 scheduler->wake(get_thread(*rit));
1007 case ATOMIC_NOTIFY_ONE: {
1008 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
1009 int wakeupthread = curr->get_node()->get_misc();
1010 action_list_t::iterator it = waiters->begin();
1011 advance(it, wakeupthread);
1012 scheduler->wake(get_thread(*it));
1023 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
1025 /* Do more ambitious checks now that mo is more complete */
1026 if (mo_may_allow(writer, reader)) {
1027 Node *node = reader->get_node();
1029 /* Find an ancestor thread which exists at the time of the reader */
1030 Thread *write_thread = get_thread(writer);
1031 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
1032 write_thread = write_thread->get_parent();
1034 struct future_value fv = {
1035 writer->get_write_value(),
1036 writer->get_seq_number() + params.maxfuturedelay,
1037 write_thread->get_id(),
1039 if (node->add_future_value(fv))
1040 set_latest_backtrack(reader);
1045 * Process a write ModelAction
1046 * @param curr The ModelAction to process
1047 * @return True if the mo_graph was updated or promises were resolved
1049 bool ModelChecker::process_write(ModelAction *curr)
1051 /* Readers to which we may send our future value */
1052 std::vector< ModelAction *, ModelAlloc<ModelAction *> > send_fv;
1054 bool updated_mod_order = w_modification_order(curr, &send_fv);
1055 int promise_idx = get_promise_to_resolve(curr);
1056 const ModelAction *earliest_promise_reader;
1057 bool updated_promises = false;
1059 if (promise_idx >= 0) {
1060 earliest_promise_reader = (*promises)[promise_idx]->get_reader(0);
1061 updated_promises = resolve_promise(curr, promise_idx);
1063 earliest_promise_reader = NULL;
1065 /* Don't send future values to reads after the Promise we resolve */
1066 for (unsigned int i = 0; i < send_fv.size(); i++) {
1067 ModelAction *read = send_fv[i];
1068 if (!earliest_promise_reader || *read < *earliest_promise_reader)
1069 futurevalues->push_back(PendingFutureValue(curr, read));
1072 if (promises->size() == 0) {
1073 for (unsigned int i = 0; i < futurevalues->size(); i++) {
1074 struct PendingFutureValue pfv = (*futurevalues)[i];
1075 add_future_value(pfv.writer, pfv.act);
1077 futurevalues->clear();
1080 mo_graph->commitChanges();
1081 mo_check_promises(curr, false);
1083 get_thread(curr)->set_return_value(VALUE_NONE);
1084 return updated_mod_order || updated_promises;
1088 * Process a fence ModelAction
1089 * @param curr The ModelAction to process
1090 * @return True if synchronization was updated
1092 bool ModelChecker::process_fence(ModelAction *curr)
1095 * fence-relaxed: no-op
1096 * fence-release: only log the occurence (not in this function), for
1097 * use in later synchronization
1098 * fence-acquire (this function): search for hypothetical release
1101 bool updated = false;
1102 if (curr->is_acquire()) {
1103 action_list_t *list = action_trace;
1104 action_list_t::reverse_iterator rit;
1105 /* Find X : is_read(X) && X --sb-> curr */
1106 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1107 ModelAction *act = *rit;
1110 if (act->get_tid() != curr->get_tid())
1112 /* Stop at the beginning of the thread */
1113 if (act->is_thread_start())
1115 /* Stop once we reach a prior fence-acquire */
1116 if (act->is_fence() && act->is_acquire())
1118 if (!act->is_read())
1120 /* read-acquire will find its own release sequences */
1121 if (act->is_acquire())
1124 /* Establish hypothetical release sequences */
1125 rel_heads_list_t release_heads;
1126 get_release_seq_heads(curr, act, &release_heads);
1127 for (unsigned int i = 0; i < release_heads.size(); i++)
1128 if (!curr->synchronize_with(release_heads[i]))
1129 set_bad_synchronization();
1130 if (release_heads.size() != 0)
1138 * @brief Process the current action for thread-related activity
1140 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1141 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1142 * synchronization, etc. This function is a no-op for non-THREAD actions
1143 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1145 * @param curr The current action
1146 * @return True if synchronization was updated or a thread completed
1148 bool ModelChecker::process_thread_action(ModelAction *curr)
1150 bool updated = false;
1152 switch (curr->get_type()) {
1153 case THREAD_CREATE: {
1154 thrd_t *thrd = (thrd_t *)curr->get_location();
1155 struct thread_params *params = (struct thread_params *)curr->get_value();
1156 Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
1158 th->set_creation(curr);
1159 /* Promises can be satisfied by children */
1160 for (unsigned int i = 0; i < promises->size(); i++) {
1161 Promise *promise = (*promises)[i];
1162 if (promise->thread_is_available(curr->get_tid()))
1163 promise->add_thread(th->get_id());
1168 Thread *blocking = curr->get_thread_operand();
1169 ModelAction *act = get_last_action(blocking->get_id());
1170 curr->synchronize_with(act);
1171 updated = true; /* trigger rel-seq checks */
1174 case THREAD_FINISH: {
1175 Thread *th = get_thread(curr);
1176 while (!th->wait_list_empty()) {
1177 ModelAction *act = th->pop_wait_list();
1178 scheduler->wake(get_thread(act));
1181 /* Completed thread can't satisfy promises */
1182 for (unsigned int i = 0; i < promises->size(); i++) {
1183 Promise *promise = (*promises)[i];
1184 if (promise->thread_is_available(th->get_id()))
1185 if (promise->eliminate_thread(th->get_id()))
1186 priv->failed_promise = true;
1188 updated = true; /* trigger rel-seq checks */
1191 case THREAD_START: {
1192 check_promises(curr->get_tid(), NULL, curr->get_cv());
1203 * @brief Process the current action for release sequence fixup activity
1205 * Performs model-checker release sequence fixups for the current action,
1206 * forcing a single pending release sequence to break (with a given, potential
1207 * "loose" write) or to complete (i.e., synchronize). If a pending release
1208 * sequence forms a complete release sequence, then we must perform the fixup
1209 * synchronization, mo_graph additions, etc.
1211 * @param curr The current action; must be a release sequence fixup action
1212 * @param work_queue The work queue to which to add work items as they are
1215 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1217 const ModelAction *write = curr->get_node()->get_relseq_break();
1218 struct release_seq *sequence = pending_rel_seqs->back();
1219 pending_rel_seqs->pop_back();
1221 ModelAction *acquire = sequence->acquire;
1222 const ModelAction *rf = sequence->rf;
1223 const ModelAction *release = sequence->release;
1227 ASSERT(release->same_thread(rf));
1229 if (write == NULL) {
1231 * @todo Forcing a synchronization requires that we set
1232 * modification order constraints. For instance, we can't allow
1233 * a fixup sequence in which two separate read-acquire
1234 * operations read from the same sequence, where the first one
1235 * synchronizes and the other doesn't. Essentially, we can't
1236 * allow any writes to insert themselves between 'release' and
1240 /* Must synchronize */
1241 if (!acquire->synchronize_with(release)) {
1242 set_bad_synchronization();
1245 /* Re-check all pending release sequences */
1246 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1247 /* Re-check act for mo_graph edges */
1248 work_queue->push_back(MOEdgeWorkEntry(acquire));
1250 /* propagate synchronization to later actions */
1251 action_list_t::reverse_iterator rit = action_trace->rbegin();
1252 for (; (*rit) != acquire; rit++) {
1253 ModelAction *propagate = *rit;
1254 if (acquire->happens_before(propagate)) {
1255 propagate->synchronize_with(acquire);
1256 /* Re-check 'propagate' for mo_graph edges */
1257 work_queue->push_back(MOEdgeWorkEntry(propagate));
1261 /* Break release sequence with new edges:
1262 * release --mo--> write --mo--> rf */
1263 mo_graph->addEdge(release, write);
1264 mo_graph->addEdge(write, rf);
1267 /* See if we have realized a data race */
1272 * Initialize the current action by performing one or more of the following
1273 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1274 * in the NodeStack, manipulating backtracking sets, allocating and
1275 * initializing clock vectors, and computing the promises to fulfill.
1277 * @param curr The current action, as passed from the user context; may be
1278 * freed/invalidated after the execution of this function, with a different
1279 * action "returned" its place (pass-by-reference)
1280 * @return True if curr is a newly-explored action; false otherwise
1282 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1284 ModelAction *newcurr;
1286 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1287 newcurr = process_rmw(*curr);
1290 if (newcurr->is_rmw())
1291 compute_promises(newcurr);
1297 (*curr)->set_seq_number(get_next_seq_num());
1299 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1301 /* First restore type and order in case of RMW operation */
1302 if ((*curr)->is_rmwr())
1303 newcurr->copy_typeandorder(*curr);
1305 ASSERT((*curr)->get_location() == newcurr->get_location());
1306 newcurr->copy_from_new(*curr);
1308 /* Discard duplicate ModelAction; use action from NodeStack */
1311 /* Always compute new clock vector */
1312 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1315 return false; /* Action was explored previously */
1319 /* Always compute new clock vector */
1320 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1322 /* Assign most recent release fence */
1323 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1326 * Perform one-time actions when pushing new ModelAction onto
1329 if (newcurr->is_write())
1330 compute_promises(newcurr);
1331 else if (newcurr->is_relseq_fixup())
1332 compute_relseq_breakwrites(newcurr);
1333 else if (newcurr->is_wait())
1334 newcurr->get_node()->set_misc_max(2);
1335 else if (newcurr->is_notify_one()) {
1336 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1338 return true; /* This was a new ModelAction */
1343 * @brief Establish reads-from relation between two actions
1345 * Perform basic operations involved with establishing a concrete rf relation,
1346 * including setting the ModelAction data and checking for release sequences.
1348 * @param act The action that is reading (must be a read)
1349 * @param rf The action from which we are reading (must be a write)
1351 * @return True if this read established synchronization
1353 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1356 act->set_read_from(rf);
1357 if (act->is_acquire()) {
1358 rel_heads_list_t release_heads;
1359 get_release_seq_heads(act, act, &release_heads);
1360 int num_heads = release_heads.size();
1361 for (unsigned int i = 0; i < release_heads.size(); i++)
1362 if (!act->synchronize_with(release_heads[i])) {
1363 set_bad_synchronization();
1366 return num_heads > 0;
1372 * Check promises and eliminate potentially-satisfying threads when a thread is
1373 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1374 * no longer satisfy a promise generated from that thread.
1376 * @param blocker The thread on which a thread is waiting
1377 * @param waiting The waiting thread
1379 void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1381 for (unsigned int i = 0; i < promises->size(); i++) {
1382 Promise *promise = (*promises)[i];
1383 if (!promise->thread_is_available(waiting->get_id()))
1385 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1386 ModelAction *reader = promise->get_reader(j);
1387 if (reader->get_tid() != blocker->get_id())
1389 if (promise->eliminate_thread(waiting->get_id())) {
1390 /* Promise has failed */
1391 priv->failed_promise = true;
1393 /* Only eliminate the 'waiting' thread once */
1401 * @brief Check whether a model action is enabled.
1403 * Checks whether a lock or join operation would be successful (i.e., is the
1404 * lock already locked, or is the joined thread already complete). If not, put
1405 * the action in a waiter list.
1407 * @param curr is the ModelAction to check whether it is enabled.
1408 * @return a bool that indicates whether the action is enabled.
1410 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1411 if (curr->is_lock()) {
1412 std::mutex *lock = (std::mutex *)curr->get_location();
1413 struct std::mutex_state *state = lock->get_state();
1414 if (state->islocked) {
1415 //Stick the action in the appropriate waiting queue
1416 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1419 } else if (curr->get_type() == THREAD_JOIN) {
1420 Thread *blocking = (Thread *)curr->get_location();
1421 if (!blocking->is_complete()) {
1422 blocking->push_wait_list(curr);
1423 thread_blocking_check_promises(blocking, get_thread(curr));
1432 * This is the heart of the model checker routine. It performs model-checking
1433 * actions corresponding to a given "current action." Among other processes, it
1434 * calculates reads-from relationships, updates synchronization clock vectors,
1435 * forms a memory_order constraints graph, and handles replay/backtrack
1436 * execution when running permutations of previously-observed executions.
1438 * @param curr The current action to process
1439 * @return The ModelAction that is actually executed; may be different than
1440 * curr; may be NULL, if the current action is not enabled to run
1442 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1445 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1447 if (!check_action_enabled(curr)) {
1448 /* Make the execution look like we chose to run this action
1449 * much later, when a lock/join can succeed */
1450 get_thread(curr)->set_pending(curr);
1451 scheduler->sleep(get_thread(curr));
1455 bool newly_explored = initialize_curr_action(&curr);
1461 wake_up_sleeping_actions(curr);
1463 /* Add the action to lists before any other model-checking tasks */
1464 if (!second_part_of_rmw)
1465 add_action_to_lists(curr);
1467 /* Build may_read_from set for newly-created actions */
1468 if (newly_explored && curr->is_read())
1469 build_may_read_from(curr);
1471 /* Initialize work_queue with the "current action" work */
1472 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1473 while (!work_queue.empty() && !has_asserted()) {
1474 WorkQueueEntry work = work_queue.front();
1475 work_queue.pop_front();
1477 switch (work.type) {
1478 case WORK_CHECK_CURR_ACTION: {
1479 ModelAction *act = work.action;
1480 bool update = false; /* update this location's release seq's */
1481 bool update_all = false; /* update all release seq's */
1483 if (process_thread_action(curr))
1486 if (act->is_read() && !second_part_of_rmw && process_read(act))
1489 if (act->is_write() && process_write(act))
1492 if (act->is_fence() && process_fence(act))
1495 if (act->is_mutex_op() && process_mutex(act))
1498 if (act->is_relseq_fixup())
1499 process_relseq_fixup(curr, &work_queue);
1502 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1504 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1507 case WORK_CHECK_RELEASE_SEQ:
1508 resolve_release_sequences(work.location, &work_queue);
1510 case WORK_CHECK_MO_EDGES: {
1511 /** @todo Complete verification of work_queue */
1512 ModelAction *act = work.action;
1513 bool updated = false;
1515 if (act->is_read()) {
1516 const ModelAction *rf = act->get_reads_from();
1517 const Promise *promise = act->get_reads_from_promise();
1519 if (r_modification_order(act, rf))
1521 } else if (promise) {
1522 if (r_modification_order(act, promise))
1526 if (act->is_write()) {
1527 if (w_modification_order(act, NULL))
1530 mo_graph->commitChanges();
1533 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1542 check_curr_backtracking(curr);
1543 set_backtracking(curr);
1547 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1549 Node *currnode = curr->get_node();
1550 Node *parnode = currnode->get_parent();
1552 if ((parnode && !parnode->backtrack_empty()) ||
1553 !currnode->misc_empty() ||
1554 !currnode->read_from_empty() ||
1555 !currnode->promise_empty() ||
1556 !currnode->relseq_break_empty()) {
1557 set_latest_backtrack(curr);
1561 bool ModelChecker::promises_expired() const
1563 for (unsigned int i = 0; i < promises->size(); i++) {
1564 Promise *promise = (*promises)[i];
1565 if (promise->get_expiration() < priv->used_sequence_numbers)
1572 * This is the strongest feasibility check available.
1573 * @return whether the current trace (partial or complete) must be a prefix of
1576 bool ModelChecker::isfeasibleprefix() const
1578 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1582 * Print disagnostic information about an infeasible execution
1583 * @param prefix A string to prefix the output with; if NULL, then a default
1584 * message prefix will be provided
1586 void ModelChecker::print_infeasibility(const char *prefix) const
1590 if (mo_graph->checkForCycles())
1591 ptr += sprintf(ptr, "[mo cycle]");
1592 if (priv->failed_promise)
1593 ptr += sprintf(ptr, "[failed promise]");
1594 if (priv->too_many_reads)
1595 ptr += sprintf(ptr, "[too many reads]");
1596 if (priv->no_valid_reads)
1597 ptr += sprintf(ptr, "[no valid reads-from]");
1598 if (priv->bad_synchronization)
1599 ptr += sprintf(ptr, "[bad sw ordering]");
1600 if (promises_expired())
1601 ptr += sprintf(ptr, "[promise expired]");
1602 if (promises->size() != 0)
1603 ptr += sprintf(ptr, "[unresolved promise]");
1605 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1609 * Returns whether the current completed trace is feasible, except for pending
1610 * release sequences.
1612 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1614 return !is_infeasible() && promises->size() == 0;
1618 * Check if the current partial trace is infeasible. Does not check any
1619 * end-of-execution flags, which might rule out the execution. Thus, this is
1620 * useful only for ruling an execution as infeasible.
1621 * @return whether the current partial trace is infeasible.
1623 bool ModelChecker::is_infeasible() const
1625 return mo_graph->checkForCycles() ||
1626 priv->no_valid_reads ||
1627 priv->failed_promise ||
1628 priv->too_many_reads ||
1629 priv->bad_synchronization ||
1633 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1634 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1635 ModelAction *lastread = get_last_action(act->get_tid());
1636 lastread->process_rmw(act);
1637 if (act->is_rmw()) {
1638 if (lastread->get_reads_from())
1639 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1641 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1642 mo_graph->commitChanges();
1647 template <typename T, typename U>
1648 bool ModelChecker::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
1650 /* Need a different write/promise */
1651 if (other_rf->equals(rf))
1654 /* Only look for "newer" writes/promises */
1655 if (!mo_graph->checkReachable(rf, other_rf))
1658 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1659 action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
1660 action_list_t::reverse_iterator rit = list->rbegin();
1661 ASSERT((*rit) == curr);
1662 /* Skip past curr */
1665 /* Does this write/promise work for everyone? */
1666 for (int i = 0; i < params.maxreads; i++, rit++) {
1667 ModelAction *act = *rit;
1668 if (!act->may_read_from(other_rf))
1675 * Checks whether a thread has read from the same write for too many times
1676 * without seeing the effects of a later write.
1679 * 1) there must a different write that we could read from that would satisfy the modification order,
1680 * 2) we must have read from the same value in excess of maxreads times, and
1681 * 3) that other write must have been in the reads_from set for maxreads times.
1683 * If so, we decide that the execution is no longer feasible.
1685 * @param curr The current action. Must be a read.
1686 * @param rf The ModelAction/Promise from which we might read.
1687 * @return True if the read should succeed; false otherwise
1689 template <typename T>
1690 bool ModelChecker::check_recency(ModelAction *curr, const T *rf) const
1692 if (!params.maxreads)
1695 //NOTE: Next check is just optimization, not really necessary....
1696 if (curr->get_node()->get_read_from_past_size() +
1697 curr->get_node()->get_read_from_promise_size() <= 1)
1700 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1701 int tid = id_to_int(curr->get_tid());
1702 ASSERT(tid < (int)thrd_lists->size());
1703 action_list_t *list = &(*thrd_lists)[tid];
1704 action_list_t::reverse_iterator rit = list->rbegin();
1705 ASSERT((*rit) == curr);
1706 /* Skip past curr */
1709 action_list_t::reverse_iterator ritcopy = rit;
1710 /* See if we have enough reads from the same value */
1711 for (int count = 0; count < params.maxreads; ritcopy++, count++) {
1712 if (ritcopy == list->rend())
1714 ModelAction *act = *ritcopy;
1715 if (!act->is_read())
1717 if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
1719 if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
1721 if (act->get_node()->get_read_from_past_size() +
1722 act->get_node()->get_read_from_promise_size() <= 1)
1725 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1726 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1727 if (should_read_instead(curr, rf, write))
1728 return false; /* liveness failure */
1730 for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
1731 const Promise *promise = curr->get_node()->get_read_from_promise(i);
1732 if (should_read_instead(curr, rf, promise))
1733 return false; /* liveness failure */
1739 * Updates the mo_graph with the constraints imposed from the current
1742 * Basic idea is the following: Go through each other thread and find
1743 * the last action that happened before our read. Two cases:
1745 * (1) The action is a write => that write must either occur before
1746 * the write we read from or be the write we read from.
1748 * (2) The action is a read => the write that that action read from
1749 * must occur before the write we read from or be the same write.
1751 * @param curr The current action. Must be a read.
1752 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1753 * @return True if modification order edges were added; false otherwise
1755 template <typename rf_type>
1756 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1758 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1761 ASSERT(curr->is_read());
1763 /* Last SC fence in the current thread */
1764 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1766 /* Iterate over all threads */
1767 for (i = 0; i < thrd_lists->size(); i++) {
1768 /* Last SC fence in thread i */
1769 ModelAction *last_sc_fence_thread_local = NULL;
1770 if (int_to_id((int)i) != curr->get_tid())
1771 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1773 /* Last SC fence in thread i, before last SC fence in current thread */
1774 ModelAction *last_sc_fence_thread_before = NULL;
1775 if (last_sc_fence_local)
1776 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1778 /* Iterate over actions in thread, starting from most recent */
1779 action_list_t *list = &(*thrd_lists)[i];
1780 action_list_t::reverse_iterator rit;
1781 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1782 ModelAction *act = *rit;
1784 if (act->is_write() && !act->equals(rf) && act != curr) {
1785 /* C++, Section 29.3 statement 5 */
1786 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1787 *act < *last_sc_fence_thread_local) {
1788 added = mo_graph->addEdge(act, rf) || added;
1791 /* C++, Section 29.3 statement 4 */
1792 else if (act->is_seqcst() && last_sc_fence_local &&
1793 *act < *last_sc_fence_local) {
1794 added = mo_graph->addEdge(act, rf) || added;
1797 /* C++, Section 29.3 statement 6 */
1798 else if (last_sc_fence_thread_before &&
1799 *act < *last_sc_fence_thread_before) {
1800 added = mo_graph->addEdge(act, rf) || added;
1806 * Include at most one act per-thread that "happens
1807 * before" curr. Don't consider reflexively.
1809 if (act->happens_before(curr) && act != curr) {
1810 if (act->is_write()) {
1811 if (!act->equals(rf)) {
1812 added = mo_graph->addEdge(act, rf) || added;
1815 const ModelAction *prevrf = act->get_reads_from();
1816 const Promise *prevrf_promise = act->get_reads_from_promise();
1818 if (!prevrf->equals(rf))
1819 added = mo_graph->addEdge(prevrf, rf) || added;
1820 } else if (!prevrf_promise->equals(rf)) {
1821 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1830 * All compatible, thread-exclusive promises must be ordered after any
1831 * concrete loads from the same thread
1833 for (unsigned int i = 0; i < promises->size(); i++)
1834 if ((*promises)[i]->is_compatible_exclusive(curr))
1835 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1841 * Updates the mo_graph with the constraints imposed from the current write.
1843 * Basic idea is the following: Go through each other thread and find
1844 * the lastest action that happened before our write. Two cases:
1846 * (1) The action is a write => that write must occur before
1849 * (2) The action is a read => the write that that action read from
1850 * must occur before the current write.
1852 * This method also handles two other issues:
1854 * (I) Sequential Consistency: Making sure that if the current write is
1855 * seq_cst, that it occurs after the previous seq_cst write.
1857 * (II) Sending the write back to non-synchronizing reads.
1859 * @param curr The current action. Must be a write.
1860 * @param send_fv A vector for stashing reads to which we may pass our future
1861 * value. If NULL, then don't record any future values.
1862 * @return True if modification order edges were added; false otherwise
1864 bool ModelChecker::w_modification_order(ModelAction *curr, std::vector< ModelAction *, ModelAlloc<ModelAction *> > *send_fv)
1866 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1869 ASSERT(curr->is_write());
1871 if (curr->is_seqcst()) {
1872 /* We have to at least see the last sequentially consistent write,
1873 so we are initialized. */
1874 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1875 if (last_seq_cst != NULL) {
1876 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1880 /* Last SC fence in the current thread */
1881 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1883 /* Iterate over all threads */
1884 for (i = 0; i < thrd_lists->size(); i++) {
1885 /* Last SC fence in thread i, before last SC fence in current thread */
1886 ModelAction *last_sc_fence_thread_before = NULL;
1887 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1888 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1890 /* Iterate over actions in thread, starting from most recent */
1891 action_list_t *list = &(*thrd_lists)[i];
1892 action_list_t::reverse_iterator rit;
1893 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1894 ModelAction *act = *rit;
1897 * 1) If RMW and it actually read from something, then we
1898 * already have all relevant edges, so just skip to next
1901 * 2) If RMW and it didn't read from anything, we should
1902 * whatever edge we can get to speed up convergence.
1904 * 3) If normal write, we need to look at earlier actions, so
1905 * continue processing list.
1907 if (curr->is_rmw()) {
1908 if (curr->get_reads_from() != NULL)
1916 /* C++, Section 29.3 statement 7 */
1917 if (last_sc_fence_thread_before && act->is_write() &&
1918 *act < *last_sc_fence_thread_before) {
1919 added = mo_graph->addEdge(act, curr) || added;
1924 * Include at most one act per-thread that "happens
1927 if (act->happens_before(curr)) {
1929 * Note: if act is RMW, just add edge:
1931 * The following edge should be handled elsewhere:
1932 * readfrom(act) --mo--> act
1934 if (act->is_write())
1935 added = mo_graph->addEdge(act, curr) || added;
1936 else if (act->is_read()) {
1937 //if previous read accessed a null, just keep going
1938 if (act->get_reads_from() == NULL)
1940 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1943 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1944 !act->same_thread(curr)) {
1945 /* We have an action that:
1946 (1) did not happen before us
1947 (2) is a read and we are a write
1948 (3) cannot synchronize with us
1949 (4) is in a different thread
1951 that read could potentially read from our write. Note that
1952 these checks are overly conservative at this point, we'll
1953 do more checks before actually removing the
1957 if (send_fv && thin_air_constraint_may_allow(curr, act)) {
1958 if (!is_infeasible())
1959 send_fv->push_back(act);
1960 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1961 add_future_value(curr, act);
1968 * All compatible, thread-exclusive promises must be ordered after any
1969 * concrete stores to the same thread, or else they can be merged with
1972 for (unsigned int i = 0; i < promises->size(); i++)
1973 if ((*promises)[i]->is_compatible_exclusive(curr))
1974 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1979 /** Arbitrary reads from the future are not allowed. Section 29.3
1980 * part 9 places some constraints. This method checks one result of constraint
1981 * constraint. Others require compiler support. */
1982 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1984 if (!writer->is_rmw())
1987 if (!reader->is_rmw())
1990 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1991 if (search == reader)
1993 if (search->get_tid() == reader->get_tid() &&
1994 search->happens_before(reader))
2002 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
2003 * some constraints. This method checks one the following constraint (others
2004 * require compiler support):
2006 * If X --hb-> Y --mo-> Z, then X should not read from Z.
2008 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
2010 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
2012 /* Iterate over all threads */
2013 for (i = 0; i < thrd_lists->size(); i++) {
2014 const ModelAction *write_after_read = NULL;
2016 /* Iterate over actions in thread, starting from most recent */
2017 action_list_t *list = &(*thrd_lists)[i];
2018 action_list_t::reverse_iterator rit;
2019 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2020 ModelAction *act = *rit;
2022 /* Don't disallow due to act == reader */
2023 if (!reader->happens_before(act) || reader == act)
2025 else if (act->is_write())
2026 write_after_read = act;
2027 else if (act->is_read() && act->get_reads_from() != NULL)
2028 write_after_read = act->get_reads_from();
2031 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
2038 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
2039 * The ModelAction under consideration is expected to be taking part in
2040 * release/acquire synchronization as an object of the "reads from" relation.
2041 * Note that this can only provide release sequence support for RMW chains
2042 * which do not read from the future, as those actions cannot be traced until
2043 * their "promise" is fulfilled. Similarly, we may not even establish the
2044 * presence of a release sequence with certainty, as some modification order
2045 * constraints may be decided further in the future. Thus, this function
2046 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
2047 * and a boolean representing certainty.
2049 * @param rf The action that might be part of a release sequence. Must be a
2051 * @param release_heads A pass-by-reference style return parameter. After
2052 * execution of this function, release_heads will contain the heads of all the
2053 * relevant release sequences, if any exists with certainty
2054 * @param pending A pass-by-reference style return parameter which is only used
2055 * when returning false (i.e., uncertain). Returns most information regarding
2056 * an uncertain release sequence, including any write operations that might
2057 * break the sequence.
2058 * @return true, if the ModelChecker is certain that release_heads is complete;
2061 bool ModelChecker::release_seq_heads(const ModelAction *rf,
2062 rel_heads_list_t *release_heads,
2063 struct release_seq *pending) const
2065 /* Only check for release sequences if there are no cycles */
2066 if (mo_graph->checkForCycles())
2069 for ( ; rf != NULL; rf = rf->get_reads_from()) {
2070 ASSERT(rf->is_write());
2072 if (rf->is_release())
2073 release_heads->push_back(rf);
2074 else if (rf->get_last_fence_release())
2075 release_heads->push_back(rf->get_last_fence_release());
2077 break; /* End of RMW chain */
2079 /** @todo Need to be smarter here... In the linux lock
2080 * example, this will run to the beginning of the program for
2082 /** @todo The way to be smarter here is to keep going until 1
2083 * thread has a release preceded by an acquire and you've seen
2086 /* acq_rel RMW is a sufficient stopping condition */
2087 if (rf->is_acquire() && rf->is_release())
2088 return true; /* complete */
2091 /* read from future: need to settle this later */
2093 return false; /* incomplete */
2096 if (rf->is_release())
2097 return true; /* complete */
2099 /* else relaxed write
2100 * - check for fence-release in the same thread (29.8, stmt. 3)
2101 * - check modification order for contiguous subsequence
2102 * -> rf must be same thread as release */
2104 const ModelAction *fence_release = rf->get_last_fence_release();
2105 /* Synchronize with a fence-release unconditionally; we don't need to
2106 * find any more "contiguous subsequence..." for it */
2108 release_heads->push_back(fence_release);
2110 int tid = id_to_int(rf->get_tid());
2111 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
2112 action_list_t *list = &(*thrd_lists)[tid];
2113 action_list_t::const_reverse_iterator rit;
2115 /* Find rf in the thread list */
2116 rit = std::find(list->rbegin(), list->rend(), rf);
2117 ASSERT(rit != list->rend());
2119 /* Find the last {write,fence}-release */
2120 for (; rit != list->rend(); rit++) {
2121 if (fence_release && *(*rit) < *fence_release)
2123 if ((*rit)->is_release())
2126 if (rit == list->rend()) {
2127 /* No write-release in this thread */
2128 return true; /* complete */
2129 } else if (fence_release && *(*rit) < *fence_release) {
2130 /* The fence-release is more recent (and so, "stronger") than
2131 * the most recent write-release */
2132 return true; /* complete */
2133 } /* else, need to establish contiguous release sequence */
2134 ModelAction *release = *rit;
2136 ASSERT(rf->same_thread(release));
2138 pending->writes.clear();
2140 bool certain = true;
2141 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2142 if (id_to_int(rf->get_tid()) == (int)i)
2144 list = &(*thrd_lists)[i];
2146 /* Can we ensure no future writes from this thread may break
2147 * the release seq? */
2148 bool future_ordered = false;
2150 ModelAction *last = get_last_action(int_to_id(i));
2151 Thread *th = get_thread(int_to_id(i));
2152 if ((last && rf->happens_before(last)) ||
2155 future_ordered = true;
2157 ASSERT(!th->is_model_thread() || future_ordered);
2159 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2160 const ModelAction *act = *rit;
2161 /* Reach synchronization -> this thread is complete */
2162 if (act->happens_before(release))
2164 if (rf->happens_before(act)) {
2165 future_ordered = true;
2169 /* Only non-RMW writes can break release sequences */
2170 if (!act->is_write() || act->is_rmw())
2173 /* Check modification order */
2174 if (mo_graph->checkReachable(rf, act)) {
2175 /* rf --mo--> act */
2176 future_ordered = true;
2179 if (mo_graph->checkReachable(act, release))
2180 /* act --mo--> release */
2182 if (mo_graph->checkReachable(release, act) &&
2183 mo_graph->checkReachable(act, rf)) {
2184 /* release --mo-> act --mo--> rf */
2185 return true; /* complete */
2187 /* act may break release sequence */
2188 pending->writes.push_back(act);
2191 if (!future_ordered)
2192 certain = false; /* This thread is uncertain */
2196 release_heads->push_back(release);
2197 pending->writes.clear();
2199 pending->release = release;
2206 * An interface for getting the release sequence head(s) with which a
2207 * given ModelAction must synchronize. This function only returns a non-empty
2208 * result when it can locate a release sequence head with certainty. Otherwise,
2209 * it may mark the internal state of the ModelChecker so that it will handle
2210 * the release sequence at a later time, causing @a acquire to update its
2211 * synchronization at some later point in execution.
2213 * @param acquire The 'acquire' action that may synchronize with a release
2215 * @param read The read action that may read from a release sequence; this may
2216 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2217 * when 'acquire' is a fence-acquire)
2218 * @param release_heads A pass-by-reference return parameter. Will be filled
2219 * with the head(s) of the release sequence(s), if they exists with certainty.
2220 * @see ModelChecker::release_seq_heads
2222 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2223 ModelAction *read, rel_heads_list_t *release_heads)
2225 const ModelAction *rf = read->get_reads_from();
2226 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2227 sequence->acquire = acquire;
2228 sequence->read = read;
2230 if (!release_seq_heads(rf, release_heads, sequence)) {
2231 /* add act to 'lazy checking' list */
2232 pending_rel_seqs->push_back(sequence);
2234 snapshot_free(sequence);
2239 * Attempt to resolve all stashed operations that might synchronize with a
2240 * release sequence for a given location. This implements the "lazy" portion of
2241 * determining whether or not a release sequence was contiguous, since not all
2242 * modification order information is present at the time an action occurs.
2244 * @param location The location/object that should be checked for release
2245 * sequence resolutions. A NULL value means to check all locations.
2246 * @param work_queue The work queue to which to add work items as they are
2248 * @return True if any updates occurred (new synchronization, new mo_graph
2251 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2253 bool updated = false;
2254 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2255 while (it != pending_rel_seqs->end()) {
2256 struct release_seq *pending = *it;
2257 ModelAction *acquire = pending->acquire;
2258 const ModelAction *read = pending->read;
2260 /* Only resolve sequences on the given location, if provided */
2261 if (location && read->get_location() != location) {
2266 const ModelAction *rf = read->get_reads_from();
2267 rel_heads_list_t release_heads;
2269 complete = release_seq_heads(rf, &release_heads, pending);
2270 for (unsigned int i = 0; i < release_heads.size(); i++) {
2271 if (!acquire->has_synchronized_with(release_heads[i])) {
2272 if (acquire->synchronize_with(release_heads[i]))
2275 set_bad_synchronization();
2280 /* Re-check all pending release sequences */
2281 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2282 /* Re-check read-acquire for mo_graph edges */
2283 if (acquire->is_read())
2284 work_queue->push_back(MOEdgeWorkEntry(acquire));
2286 /* propagate synchronization to later actions */
2287 action_list_t::reverse_iterator rit = action_trace->rbegin();
2288 for (; (*rit) != acquire; rit++) {
2289 ModelAction *propagate = *rit;
2290 if (acquire->happens_before(propagate)) {
2291 propagate->synchronize_with(acquire);
2292 /* Re-check 'propagate' for mo_graph edges */
2293 work_queue->push_back(MOEdgeWorkEntry(propagate));
2298 it = pending_rel_seqs->erase(it);
2299 snapshot_free(pending);
2305 // If we resolved promises or data races, see if we have realized a data race.
2312 * Performs various bookkeeping operations for the current ModelAction. For
2313 * instance, adds action to the per-object, per-thread action vector and to the
2314 * action trace list of all thread actions.
2316 * @param act is the ModelAction to add.
2318 void ModelChecker::add_action_to_lists(ModelAction *act)
2320 int tid = id_to_int(act->get_tid());
2321 ModelAction *uninit = NULL;
2323 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2324 if (list->empty() && act->is_atomic_var()) {
2325 uninit = new_uninitialized_action(act->get_location());
2326 uninit_id = id_to_int(uninit->get_tid());
2327 list->push_back(uninit);
2329 list->push_back(act);
2331 action_trace->push_back(act);
2333 action_trace->push_front(uninit);
2335 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2336 if (tid >= (int)vec->size())
2337 vec->resize(priv->next_thread_id);
2338 (*vec)[tid].push_back(act);
2340 (*vec)[uninit_id].push_front(uninit);
2342 if ((int)thrd_last_action->size() <= tid)
2343 thrd_last_action->resize(get_num_threads());
2344 (*thrd_last_action)[tid] = act;
2346 (*thrd_last_action)[uninit_id] = uninit;
2348 if (act->is_fence() && act->is_release()) {
2349 if ((int)thrd_last_fence_release->size() <= tid)
2350 thrd_last_fence_release->resize(get_num_threads());
2351 (*thrd_last_fence_release)[tid] = act;
2354 if (act->is_wait()) {
2355 void *mutex_loc = (void *) act->get_value();
2356 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2358 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2359 if (tid >= (int)vec->size())
2360 vec->resize(priv->next_thread_id);
2361 (*vec)[tid].push_back(act);
2366 * @brief Get the last action performed by a particular Thread
2367 * @param tid The thread ID of the Thread in question
2368 * @return The last action in the thread
2370 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2372 int threadid = id_to_int(tid);
2373 if (threadid < (int)thrd_last_action->size())
2374 return (*thrd_last_action)[id_to_int(tid)];
2380 * @brief Get the last fence release performed by a particular Thread
2381 * @param tid The thread ID of the Thread in question
2382 * @return The last fence release in the thread, if one exists; NULL otherwise
2384 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2386 int threadid = id_to_int(tid);
2387 if (threadid < (int)thrd_last_fence_release->size())
2388 return (*thrd_last_fence_release)[id_to_int(tid)];
2394 * Gets the last memory_order_seq_cst write (in the total global sequence)
2395 * performed on a particular object (i.e., memory location), not including the
2397 * @param curr The current ModelAction; also denotes the object location to
2399 * @return The last seq_cst write
2401 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2403 void *location = curr->get_location();
2404 action_list_t *list = get_safe_ptr_action(obj_map, location);
2405 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2406 action_list_t::reverse_iterator rit;
2407 for (rit = list->rbegin(); rit != list->rend(); rit++)
2408 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2414 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2415 * performed in a particular thread, prior to a particular fence.
2416 * @param tid The ID of the thread to check
2417 * @param before_fence The fence from which to begin the search; if NULL, then
2418 * search for the most recent fence in the thread.
2419 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2421 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2423 /* All fences should have NULL location */
2424 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2425 action_list_t::reverse_iterator rit = list->rbegin();
2428 for (; rit != list->rend(); rit++)
2429 if (*rit == before_fence)
2432 ASSERT(*rit == before_fence);
2436 for (; rit != list->rend(); rit++)
2437 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2443 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2444 * location). This function identifies the mutex according to the current
2445 * action, which is presumed to perform on the same mutex.
2446 * @param curr The current ModelAction; also denotes the object location to
2448 * @return The last unlock operation
2450 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2452 void *location = curr->get_location();
2453 action_list_t *list = get_safe_ptr_action(obj_map, location);
2454 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2455 action_list_t::reverse_iterator rit;
2456 for (rit = list->rbegin(); rit != list->rend(); rit++)
2457 if ((*rit)->is_unlock() || (*rit)->is_wait())
2462 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2464 ModelAction *parent = get_last_action(tid);
2466 parent = get_thread(tid)->get_creation();
2471 * Returns the clock vector for a given thread.
2472 * @param tid The thread whose clock vector we want
2473 * @return Desired clock vector
2475 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2477 return get_parent_action(tid)->get_cv();
2481 * @brief Find the promise, if any to resolve for the current action
2482 * @param curr The current ModelAction. Should be a write.
2483 * @return The (non-negative) index for the Promise to resolve, if any;
2486 int ModelChecker::get_promise_to_resolve(const ModelAction *curr) const
2488 for (unsigned int i = 0; i < promises->size(); i++)
2489 if (curr->get_node()->get_promise(i))
2495 * Resolve a Promise with a current write.
2496 * @param write The ModelAction that is fulfilling Promises
2497 * @param promise_idx The index corresponding to the promise
2498 * @return True if the Promise was successfully resolved; false otherwise
2500 bool ModelChecker::resolve_promise(ModelAction *write, unsigned int promise_idx)
2502 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2503 promise_list_t mustResolve;
2504 Promise *promise = (*promises)[promise_idx];
2506 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2507 ModelAction *read = promise->get_reader(i);
2508 read_from(read, write);
2509 actions_to_check.push_back(read);
2511 /* Make sure the promise's value matches the write's value */
2512 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2513 mo_graph->resolvePromise(promise, write, &mustResolve);
2515 promises->erase(promises->begin() + promise_idx);
2517 /** @todo simplify the 'mustResolve' stuff */
2518 ASSERT(mustResolve.size() <= 1);
2520 if (!mustResolve.empty() && mustResolve[0] != promise)
2521 priv->failed_promise = true;
2524 //Check whether reading these writes has made threads unable to
2527 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2528 ModelAction *read = actions_to_check[i];
2529 mo_check_promises(read, true);
2536 * Compute the set of promises that could potentially be satisfied by this
2537 * action. Note that the set computation actually appears in the Node, not in
2539 * @param curr The ModelAction that may satisfy promises
2541 void ModelChecker::compute_promises(ModelAction *curr)
2543 for (unsigned int i = 0; i < promises->size(); i++) {
2544 Promise *promise = (*promises)[i];
2545 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2548 bool satisfy = true;
2549 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2550 const ModelAction *act = promise->get_reader(j);
2551 if (act->happens_before(curr) ||
2552 act->could_synchronize_with(curr)) {
2558 curr->get_node()->set_promise(i);
2562 /** Checks promises in response to change in ClockVector Threads. */
2563 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2565 for (unsigned int i = 0; i < promises->size(); i++) {
2566 Promise *promise = (*promises)[i];
2567 if (!promise->thread_is_available(tid))
2569 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2570 const ModelAction *act = promise->get_reader(j);
2571 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2572 merge_cv->synchronized_since(act)) {
2573 if (promise->eliminate_thread(tid)) {
2574 /* Promise has failed */
2575 priv->failed_promise = true;
2583 void ModelChecker::check_promises_thread_disabled()
2585 for (unsigned int i = 0; i < promises->size(); i++) {
2586 Promise *promise = (*promises)[i];
2587 if (promise->has_failed()) {
2588 priv->failed_promise = true;
2595 * @brief Checks promises in response to addition to modification order for
2598 * We test whether threads are still available for satisfying promises after an
2599 * addition to our modification order constraints. Those that are unavailable
2600 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2601 * that promise has failed.
2603 * @param act The ModelAction which updated the modification order
2604 * @param is_read_check Should be true if act is a read and we must check for
2605 * updates to the store from which it read (there is a distinction here for
2606 * RMW's, which are both a load and a store)
2608 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2610 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2612 for (unsigned int i = 0; i < promises->size(); i++) {
2613 Promise *promise = (*promises)[i];
2615 // Is this promise on the same location?
2616 if (!promise->same_location(write))
2619 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2620 const ModelAction *pread = promise->get_reader(j);
2621 if (!pread->happens_before(act))
2623 if (mo_graph->checkPromise(write, promise)) {
2624 priv->failed_promise = true;
2630 // Don't do any lookups twice for the same thread
2631 if (!promise->thread_is_available(act->get_tid()))
2634 if (mo_graph->checkReachable(promise, write)) {
2635 if (mo_graph->checkPromise(write, promise)) {
2636 priv->failed_promise = true;
2644 * Compute the set of writes that may break the current pending release
2645 * sequence. This information is extracted from previou release sequence
2648 * @param curr The current ModelAction. Must be a release sequence fixup
2651 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2653 if (pending_rel_seqs->empty())
2656 struct release_seq *pending = pending_rel_seqs->back();
2657 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2658 const ModelAction *write = pending->writes[i];
2659 curr->get_node()->add_relseq_break(write);
2662 /* NULL means don't break the sequence; just synchronize */
2663 curr->get_node()->add_relseq_break(NULL);
2667 * Build up an initial set of all past writes that this 'read' action may read
2668 * from, as well as any previously-observed future values that must still be valid.
2670 * @param curr is the current ModelAction that we are exploring; it must be a
2673 void ModelChecker::build_may_read_from(ModelAction *curr)
2675 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2677 ASSERT(curr->is_read());
2679 ModelAction *last_sc_write = NULL;
2681 if (curr->is_seqcst())
2682 last_sc_write = get_last_seq_cst_write(curr);
2684 /* Iterate over all threads */
2685 for (i = 0; i < thrd_lists->size(); i++) {
2686 /* Iterate over actions in thread, starting from most recent */
2687 action_list_t *list = &(*thrd_lists)[i];
2688 action_list_t::reverse_iterator rit;
2689 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2690 ModelAction *act = *rit;
2692 /* Only consider 'write' actions */
2693 if (!act->is_write() || act == curr)
2696 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2697 bool allow_read = true;
2699 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2701 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2705 /* Only add feasible reads */
2706 mo_graph->startChanges();
2707 r_modification_order(curr, act);
2708 if (!is_infeasible())
2709 curr->get_node()->add_read_from_past(act);
2710 mo_graph->rollbackChanges();
2713 /* Include at most one act per-thread that "happens before" curr */
2714 if (act->happens_before(curr))
2719 /* Inherit existing, promised future values */
2720 for (i = 0; i < promises->size(); i++) {
2721 const Promise *promise = (*promises)[i];
2722 const ModelAction *promise_read = promise->get_reader(0);
2723 if (promise_read->same_var(curr)) {
2724 /* Only add feasible future-values */
2725 mo_graph->startChanges();
2726 r_modification_order(curr, promise);
2727 if (!is_infeasible())
2728 curr->get_node()->add_read_from_promise(promise_read);
2729 mo_graph->rollbackChanges();
2733 /* We may find no valid may-read-from only if the execution is doomed */
2734 if (!curr->get_node()->read_from_size()) {
2735 priv->no_valid_reads = true;
2739 if (DBG_ENABLED()) {
2740 model_print("Reached read action:\n");
2742 model_print("Printing read_from_past\n");
2743 curr->get_node()->print_read_from_past();
2744 model_print("End printing read_from_past\n");
2748 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2750 for ( ; write != NULL; write = write->get_reads_from()) {
2751 /* UNINIT actions don't have a Node, and they never sleep */
2752 if (write->is_uninitialized())
2754 Node *prevnode = write->get_node()->get_parent();
2756 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2757 if (write->is_release() && thread_sleep)
2759 if (!write->is_rmw())
2766 * @brief Create a new action representing an uninitialized atomic
2767 * @param location The memory location of the atomic object
2768 * @return A pointer to a new ModelAction
2770 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2772 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2773 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2774 act->create_cv(NULL);
2778 static void print_list(action_list_t *list)
2780 action_list_t::iterator it;
2782 model_print("---------------------------------------------------------------------\n");
2784 unsigned int hash = 0;
2786 for (it = list->begin(); it != list->end(); it++) {
2788 hash = hash^(hash<<3)^((*it)->hash());
2790 model_print("HASH %u\n", hash);
2791 model_print("---------------------------------------------------------------------\n");
2794 #if SUPPORT_MOD_ORDER_DUMP
2795 void ModelChecker::dumpGraph(char *filename) const
2798 sprintf(buffer, "%s.dot", filename);
2799 FILE *file = fopen(buffer, "w");
2800 fprintf(file, "digraph %s {\n", filename);
2801 mo_graph->dumpNodes(file);
2802 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2804 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2805 ModelAction *act = *it;
2806 if (act->is_read()) {
2807 mo_graph->dot_print_node(file, act);
2808 if (act->get_reads_from())
2809 mo_graph->dot_print_edge(file,
2810 act->get_reads_from(),
2812 "label=\"rf\", color=red, weight=2");
2814 mo_graph->dot_print_edge(file,
2815 act->get_reads_from_promise(),
2817 "label=\"rf\", color=red");
2819 if (thread_array[act->get_tid()]) {
2820 mo_graph->dot_print_edge(file,
2821 thread_array[id_to_int(act->get_tid())],
2823 "label=\"sb\", color=blue, weight=400");
2826 thread_array[act->get_tid()] = act;
2828 fprintf(file, "}\n");
2829 model_free(thread_array);
2834 /** @brief Prints an execution trace summary. */
2835 void ModelChecker::print_summary() const
2837 #if SUPPORT_MOD_ORDER_DUMP
2838 char buffername[100];
2839 sprintf(buffername, "exec%04u", stats.num_total);
2840 mo_graph->dumpGraphToFile(buffername);
2841 sprintf(buffername, "graph%04u", stats.num_total);
2842 dumpGraph(buffername);
2845 model_print("Execution %d:", stats.num_total);
2846 if (isfeasibleprefix()) {
2847 if (scheduler->all_threads_sleeping())
2848 model_print(" SLEEP-SET REDUNDANT");
2851 print_infeasibility(" INFEASIBLE");
2852 print_list(action_trace);
2857 * Add a Thread to the system for the first time. Should only be called once
2859 * @param t The Thread to add
2861 void ModelChecker::add_thread(Thread *t)
2863 thread_map->put(id_to_int(t->get_id()), t);
2864 scheduler->add_thread(t);
2868 * Removes a thread from the scheduler.
2869 * @param the thread to remove.
2871 void ModelChecker::remove_thread(Thread *t)
2873 scheduler->remove_thread(t);
2877 * @brief Get a Thread reference by its ID
2878 * @param tid The Thread's ID
2879 * @return A Thread reference
2881 Thread * ModelChecker::get_thread(thread_id_t tid) const
2883 return thread_map->get(id_to_int(tid));
2887 * @brief Get a reference to the Thread in which a ModelAction was executed
2888 * @param act The ModelAction
2889 * @return A Thread reference
2891 Thread * ModelChecker::get_thread(const ModelAction *act) const
2893 return get_thread(act->get_tid());
2897 * @brief Get a Promise's "promise number"
2899 * A "promise number" is an index number that is unique to a promise, valid
2900 * only for a specific snapshot of an execution trace. Promises may come and go
2901 * as they are generated an resolved, so an index only retains meaning for the
2904 * @param promise The Promise to check
2905 * @return The promise index, if the promise still is valid; otherwise -1
2907 int ModelChecker::get_promise_number(const Promise *promise) const
2909 for (unsigned int i = 0; i < promises->size(); i++)
2910 if ((*promises)[i] == promise)
2917 * @brief Check if a Thread is currently enabled
2918 * @param t The Thread to check
2919 * @return True if the Thread is currently enabled
2921 bool ModelChecker::is_enabled(Thread *t) const
2923 return scheduler->is_enabled(t);
2927 * @brief Check if a Thread is currently enabled
2928 * @param tid The ID of the Thread to check
2929 * @return True if the Thread is currently enabled
2931 bool ModelChecker::is_enabled(thread_id_t tid) const
2933 return scheduler->is_enabled(tid);
2937 * Switch from a model-checker context to a user-thread context. This is the
2938 * complement of ModelChecker::switch_to_master and must be called from the
2939 * model-checker context
2941 * @param thread The user-thread to switch to
2943 void ModelChecker::switch_from_master(Thread *thread)
2945 scheduler->set_current_thread(thread);
2946 Thread::swap(&system_context, thread);
2950 * Switch from a user-context to the "master thread" context (a.k.a. system
2951 * context). This switch is made with the intention of exploring a particular
2952 * model-checking action (described by a ModelAction object). Must be called
2953 * from a user-thread context.
2955 * @param act The current action that will be explored. May be NULL only if
2956 * trace is exiting via an assertion (see ModelChecker::set_assert and
2957 * ModelChecker::has_asserted).
2958 * @return Return the value returned by the current action
2960 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2963 Thread *old = thread_current();
2964 ASSERT(!old->get_pending());
2965 old->set_pending(act);
2966 if (Thread::swap(old, &system_context) < 0) {
2967 perror("swap threads");
2970 return old->get_return_value();
2974 * Takes the next step in the execution, if possible.
2975 * @param curr The current step to take
2976 * @return Returns the next Thread to run, if any; NULL if this execution
2979 Thread * ModelChecker::take_step(ModelAction *curr)
2981 Thread *curr_thrd = get_thread(curr);
2982 ASSERT(curr_thrd->get_state() == THREAD_READY);
2984 curr = check_current_action(curr);
2986 /* Infeasible -> don't take any more steps */
2987 if (is_infeasible())
2989 else if (isfeasibleprefix() && have_bug_reports()) {
2994 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2997 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2998 scheduler->remove_thread(curr_thrd);
3000 Thread *next_thrd = get_next_thread(curr);
3002 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
3003 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
3008 /** Wrapper to run the user's main function, with appropriate arguments */
3009 void user_main_wrapper(void *)
3011 user_main(model->params.argc, model->params.argv);
3014 /** @brief Run ModelChecker for the user program */
3015 void ModelChecker::run()
3019 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
3024 * Stash next pending action(s) for thread(s). There
3025 * should only need to stash one thread's action--the
3026 * thread which just took a step--plus the first step
3027 * for any newly-created thread
3029 for (unsigned int i = 0; i < get_num_threads(); i++) {
3030 thread_id_t tid = int_to_id(i);
3031 Thread *thr = get_thread(tid);
3032 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
3033 switch_from_master(thr);
3037 /* Catch assertions from prior take_step or from
3038 * between-ModelAction bugs (e.g., data races) */
3042 /* Consume the next action for a Thread */
3043 ModelAction *curr = t->get_pending();
3044 t->set_pending(NULL);
3045 t = take_step(curr);
3046 } while (t && !t->is_model_thread());
3049 * Launch end-of-execution release sequence fixups only when
3050 * the execution is otherwise feasible AND there are:
3052 * (1) pending release sequences
3053 * (2) pending assertions that could be invalidated by a change
3054 * in clock vectors (i.e., data races)
3055 * (3) no pending promises
3057 while (!pending_rel_seqs->empty() &&
3058 is_feasible_prefix_ignore_relseq() &&
3059 !unrealizedraces.empty()) {
3060 model_print("*** WARNING: release sequence fixup action "
3061 "(%zu pending release seuqence(s)) ***\n",
3062 pending_rel_seqs->size());
3063 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
3064 std::memory_order_seq_cst, NULL, VALUE_NONE,
3068 } while (next_execution());
3070 model_print("******* Model-checking complete: *******\n");