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 updated = r_modification_order(curr, promise);
891 mo_graph->commitChanges();
894 case READ_FROM_FUTURE: {
895 /* Read from future value */
896 struct future_value fv = node->get_future_value();
897 Promise *promise = new Promise(curr, fv);
899 curr->set_read_from_promise(promise);
900 promises->push_back(promise);
901 mo_graph->startChanges();
902 updated = r_modification_order(curr, promise);
903 mo_graph->commitChanges();
909 get_thread(curr)->set_return_value(value);
915 * Processes a lock, trylock, or unlock model action. @param curr is
916 * the read model action to process.
918 * The try lock operation checks whether the lock is taken. If not,
919 * it falls to the normal lock operation case. If so, it returns
922 * The lock operation has already been checked that it is enabled, so
923 * it just grabs the lock and synchronizes with the previous unlock.
925 * The unlock operation has to re-enable all of the threads that are
926 * waiting on the lock.
928 * @return True if synchronization was updated; false otherwise
930 bool ModelChecker::process_mutex(ModelAction *curr)
932 std::mutex *mutex = NULL;
933 struct std::mutex_state *state = NULL;
935 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
936 mutex = (std::mutex *)curr->get_location();
937 state = mutex->get_state();
938 } else if (curr->is_wait()) {
939 mutex = (std::mutex *)curr->get_value();
940 state = mutex->get_state();
943 switch (curr->get_type()) {
944 case ATOMIC_TRYLOCK: {
945 bool success = !state->islocked;
946 curr->set_try_lock(success);
948 get_thread(curr)->set_return_value(0);
951 get_thread(curr)->set_return_value(1);
953 //otherwise fall into the lock case
955 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
956 assert_bug("Lock access before initialization");
957 state->islocked = true;
958 ModelAction *unlock = get_last_unlock(curr);
959 //synchronize with the previous unlock statement
960 if (unlock != NULL) {
961 curr->synchronize_with(unlock);
966 case ATOMIC_UNLOCK: {
968 state->islocked = false;
969 //wake up the other threads
970 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
971 //activate all the waiting threads
972 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
973 scheduler->wake(get_thread(*rit));
980 state->islocked = false;
981 //wake up the other threads
982 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
983 //activate all the waiting threads
984 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
985 scheduler->wake(get_thread(*rit));
988 //check whether we should go to sleep or not...simulate spurious failures
989 if (curr->get_node()->get_misc() == 0) {
990 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
992 scheduler->sleep(get_thread(curr));
996 case ATOMIC_NOTIFY_ALL: {
997 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
998 //activate all the waiting threads
999 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
1000 scheduler->wake(get_thread(*rit));
1005 case ATOMIC_NOTIFY_ONE: {
1006 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
1007 int wakeupthread = curr->get_node()->get_misc();
1008 action_list_t::iterator it = waiters->begin();
1009 advance(it, wakeupthread);
1010 scheduler->wake(get_thread(*it));
1021 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
1023 /* Do more ambitious checks now that mo is more complete */
1024 if (mo_may_allow(writer, reader)) {
1025 Node *node = reader->get_node();
1027 /* Find an ancestor thread which exists at the time of the reader */
1028 Thread *write_thread = get_thread(writer);
1029 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
1030 write_thread = write_thread->get_parent();
1032 struct future_value fv = {
1033 writer->get_write_value(),
1034 writer->get_seq_number() + params.maxfuturedelay,
1035 write_thread->get_id(),
1037 if (node->add_future_value(fv))
1038 set_latest_backtrack(reader);
1043 * Process a write ModelAction
1044 * @param curr The ModelAction to process
1045 * @return True if the mo_graph was updated or promises were resolved
1047 bool ModelChecker::process_write(ModelAction *curr)
1049 /* Readers to which we may send our future value */
1050 std::vector< ModelAction *, ModelAlloc<ModelAction *> > send_fv;
1052 bool updated_mod_order = w_modification_order(curr, &send_fv);
1053 int promise_idx = get_promise_to_resolve(curr);
1054 const ModelAction *earliest_promise_reader;
1055 bool updated_promises = false;
1057 if (promise_idx >= 0) {
1058 earliest_promise_reader = (*promises)[promise_idx]->get_reader(0);
1059 updated_promises = resolve_promise(curr, promise_idx);
1061 earliest_promise_reader = NULL;
1063 /* Don't send future values to reads after the Promise we resolve */
1064 for (unsigned int i = 0; i < send_fv.size(); i++) {
1065 ModelAction *read = send_fv[i];
1066 if (!earliest_promise_reader || *read < *earliest_promise_reader)
1067 futurevalues->push_back(PendingFutureValue(curr, read));
1070 if (promises->size() == 0) {
1071 for (unsigned int i = 0; i < futurevalues->size(); i++) {
1072 struct PendingFutureValue pfv = (*futurevalues)[i];
1073 add_future_value(pfv.writer, pfv.act);
1075 futurevalues->clear();
1078 mo_graph->commitChanges();
1079 mo_check_promises(curr, false);
1081 get_thread(curr)->set_return_value(VALUE_NONE);
1082 return updated_mod_order || updated_promises;
1086 * Process a fence ModelAction
1087 * @param curr The ModelAction to process
1088 * @return True if synchronization was updated
1090 bool ModelChecker::process_fence(ModelAction *curr)
1093 * fence-relaxed: no-op
1094 * fence-release: only log the occurence (not in this function), for
1095 * use in later synchronization
1096 * fence-acquire (this function): search for hypothetical release
1099 bool updated = false;
1100 if (curr->is_acquire()) {
1101 action_list_t *list = action_trace;
1102 action_list_t::reverse_iterator rit;
1103 /* Find X : is_read(X) && X --sb-> curr */
1104 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1105 ModelAction *act = *rit;
1108 if (act->get_tid() != curr->get_tid())
1110 /* Stop at the beginning of the thread */
1111 if (act->is_thread_start())
1113 /* Stop once we reach a prior fence-acquire */
1114 if (act->is_fence() && act->is_acquire())
1116 if (!act->is_read())
1118 /* read-acquire will find its own release sequences */
1119 if (act->is_acquire())
1122 /* Establish hypothetical release sequences */
1123 rel_heads_list_t release_heads;
1124 get_release_seq_heads(curr, act, &release_heads);
1125 for (unsigned int i = 0; i < release_heads.size(); i++)
1126 if (!curr->synchronize_with(release_heads[i]))
1127 set_bad_synchronization();
1128 if (release_heads.size() != 0)
1136 * @brief Process the current action for thread-related activity
1138 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1139 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1140 * synchronization, etc. This function is a no-op for non-THREAD actions
1141 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1143 * @param curr The current action
1144 * @return True if synchronization was updated or a thread completed
1146 bool ModelChecker::process_thread_action(ModelAction *curr)
1148 bool updated = false;
1150 switch (curr->get_type()) {
1151 case THREAD_CREATE: {
1152 thrd_t *thrd = (thrd_t *)curr->get_location();
1153 struct thread_params *params = (struct thread_params *)curr->get_value();
1154 Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
1156 th->set_creation(curr);
1157 /* Promises can be satisfied by children */
1158 for (unsigned int i = 0; i < promises->size(); i++) {
1159 Promise *promise = (*promises)[i];
1160 if (promise->thread_is_available(curr->get_tid()))
1161 promise->add_thread(th->get_id());
1166 Thread *blocking = curr->get_thread_operand();
1167 ModelAction *act = get_last_action(blocking->get_id());
1168 curr->synchronize_with(act);
1169 updated = true; /* trigger rel-seq checks */
1172 case THREAD_FINISH: {
1173 Thread *th = get_thread(curr);
1174 while (!th->wait_list_empty()) {
1175 ModelAction *act = th->pop_wait_list();
1176 scheduler->wake(get_thread(act));
1179 /* Completed thread can't satisfy promises */
1180 for (unsigned int i = 0; i < promises->size(); i++) {
1181 Promise *promise = (*promises)[i];
1182 if (promise->thread_is_available(th->get_id()))
1183 if (promise->eliminate_thread(th->get_id()))
1184 priv->failed_promise = true;
1186 updated = true; /* trigger rel-seq checks */
1189 case THREAD_START: {
1190 check_promises(curr->get_tid(), NULL, curr->get_cv());
1201 * @brief Process the current action for release sequence fixup activity
1203 * Performs model-checker release sequence fixups for the current action,
1204 * forcing a single pending release sequence to break (with a given, potential
1205 * "loose" write) or to complete (i.e., synchronize). If a pending release
1206 * sequence forms a complete release sequence, then we must perform the fixup
1207 * synchronization, mo_graph additions, etc.
1209 * @param curr The current action; must be a release sequence fixup action
1210 * @param work_queue The work queue to which to add work items as they are
1213 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1215 const ModelAction *write = curr->get_node()->get_relseq_break();
1216 struct release_seq *sequence = pending_rel_seqs->back();
1217 pending_rel_seqs->pop_back();
1219 ModelAction *acquire = sequence->acquire;
1220 const ModelAction *rf = sequence->rf;
1221 const ModelAction *release = sequence->release;
1225 ASSERT(release->same_thread(rf));
1227 if (write == NULL) {
1229 * @todo Forcing a synchronization requires that we set
1230 * modification order constraints. For instance, we can't allow
1231 * a fixup sequence in which two separate read-acquire
1232 * operations read from the same sequence, where the first one
1233 * synchronizes and the other doesn't. Essentially, we can't
1234 * allow any writes to insert themselves between 'release' and
1238 /* Must synchronize */
1239 if (!acquire->synchronize_with(release)) {
1240 set_bad_synchronization();
1243 /* Re-check all pending release sequences */
1244 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1245 /* Re-check act for mo_graph edges */
1246 work_queue->push_back(MOEdgeWorkEntry(acquire));
1248 /* propagate synchronization to later actions */
1249 action_list_t::reverse_iterator rit = action_trace->rbegin();
1250 for (; (*rit) != acquire; rit++) {
1251 ModelAction *propagate = *rit;
1252 if (acquire->happens_before(propagate)) {
1253 propagate->synchronize_with(acquire);
1254 /* Re-check 'propagate' for mo_graph edges */
1255 work_queue->push_back(MOEdgeWorkEntry(propagate));
1259 /* Break release sequence with new edges:
1260 * release --mo--> write --mo--> rf */
1261 mo_graph->addEdge(release, write);
1262 mo_graph->addEdge(write, rf);
1265 /* See if we have realized a data race */
1270 * Initialize the current action by performing one or more of the following
1271 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1272 * in the NodeStack, manipulating backtracking sets, allocating and
1273 * initializing clock vectors, and computing the promises to fulfill.
1275 * @param curr The current action, as passed from the user context; may be
1276 * freed/invalidated after the execution of this function, with a different
1277 * action "returned" its place (pass-by-reference)
1278 * @return True if curr is a newly-explored action; false otherwise
1280 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1282 ModelAction *newcurr;
1284 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1285 newcurr = process_rmw(*curr);
1288 if (newcurr->is_rmw())
1289 compute_promises(newcurr);
1295 (*curr)->set_seq_number(get_next_seq_num());
1297 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1299 /* First restore type and order in case of RMW operation */
1300 if ((*curr)->is_rmwr())
1301 newcurr->copy_typeandorder(*curr);
1303 ASSERT((*curr)->get_location() == newcurr->get_location());
1304 newcurr->copy_from_new(*curr);
1306 /* Discard duplicate ModelAction; use action from NodeStack */
1309 /* Always compute new clock vector */
1310 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1313 return false; /* Action was explored previously */
1317 /* Always compute new clock vector */
1318 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1320 /* Assign most recent release fence */
1321 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1324 * Perform one-time actions when pushing new ModelAction onto
1327 if (newcurr->is_write())
1328 compute_promises(newcurr);
1329 else if (newcurr->is_relseq_fixup())
1330 compute_relseq_breakwrites(newcurr);
1331 else if (newcurr->is_wait())
1332 newcurr->get_node()->set_misc_max(2);
1333 else if (newcurr->is_notify_one()) {
1334 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1336 return true; /* This was a new ModelAction */
1341 * @brief Establish reads-from relation between two actions
1343 * Perform basic operations involved with establishing a concrete rf relation,
1344 * including setting the ModelAction data and checking for release sequences.
1346 * @param act The action that is reading (must be a read)
1347 * @param rf The action from which we are reading (must be a write)
1349 * @return True if this read established synchronization
1351 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1354 act->set_read_from(rf);
1355 if (act->is_acquire()) {
1356 rel_heads_list_t release_heads;
1357 get_release_seq_heads(act, act, &release_heads);
1358 int num_heads = release_heads.size();
1359 for (unsigned int i = 0; i < release_heads.size(); i++)
1360 if (!act->synchronize_with(release_heads[i])) {
1361 set_bad_synchronization();
1364 return num_heads > 0;
1370 * Check promises and eliminate potentially-satisfying threads when a thread is
1371 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1372 * no longer satisfy a promise generated from that thread.
1374 * @param blocker The thread on which a thread is waiting
1375 * @param waiting The waiting thread
1377 void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1379 for (unsigned int i = 0; i < promises->size(); i++) {
1380 Promise *promise = (*promises)[i];
1381 if (!promise->thread_is_available(waiting->get_id()))
1383 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1384 ModelAction *reader = promise->get_reader(j);
1385 if (reader->get_tid() != blocker->get_id())
1387 if (promise->eliminate_thread(waiting->get_id())) {
1388 /* Promise has failed */
1389 priv->failed_promise = true;
1391 /* Only eliminate the 'waiting' thread once */
1399 * @brief Check whether a model action is enabled.
1401 * Checks whether a lock or join operation would be successful (i.e., is the
1402 * lock already locked, or is the joined thread already complete). If not, put
1403 * the action in a waiter list.
1405 * @param curr is the ModelAction to check whether it is enabled.
1406 * @return a bool that indicates whether the action is enabled.
1408 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1409 if (curr->is_lock()) {
1410 std::mutex *lock = (std::mutex *)curr->get_location();
1411 struct std::mutex_state *state = lock->get_state();
1412 if (state->islocked) {
1413 //Stick the action in the appropriate waiting queue
1414 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1417 } else if (curr->get_type() == THREAD_JOIN) {
1418 Thread *blocking = (Thread *)curr->get_location();
1419 if (!blocking->is_complete()) {
1420 blocking->push_wait_list(curr);
1421 thread_blocking_check_promises(blocking, get_thread(curr));
1430 * This is the heart of the model checker routine. It performs model-checking
1431 * actions corresponding to a given "current action." Among other processes, it
1432 * calculates reads-from relationships, updates synchronization clock vectors,
1433 * forms a memory_order constraints graph, and handles replay/backtrack
1434 * execution when running permutations of previously-observed executions.
1436 * @param curr The current action to process
1437 * @return The ModelAction that is actually executed; may be different than
1438 * curr; may be NULL, if the current action is not enabled to run
1440 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1443 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1445 if (!check_action_enabled(curr)) {
1446 /* Make the execution look like we chose to run this action
1447 * much later, when a lock/join can succeed */
1448 get_thread(curr)->set_pending(curr);
1449 scheduler->sleep(get_thread(curr));
1453 bool newly_explored = initialize_curr_action(&curr);
1459 wake_up_sleeping_actions(curr);
1461 /* Add the action to lists before any other model-checking tasks */
1462 if (!second_part_of_rmw)
1463 add_action_to_lists(curr);
1465 /* Build may_read_from set for newly-created actions */
1466 if (newly_explored && curr->is_read())
1467 build_may_read_from(curr);
1469 /* Initialize work_queue with the "current action" work */
1470 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1471 while (!work_queue.empty() && !has_asserted()) {
1472 WorkQueueEntry work = work_queue.front();
1473 work_queue.pop_front();
1475 switch (work.type) {
1476 case WORK_CHECK_CURR_ACTION: {
1477 ModelAction *act = work.action;
1478 bool update = false; /* update this location's release seq's */
1479 bool update_all = false; /* update all release seq's */
1481 if (process_thread_action(curr))
1484 if (act->is_read() && !second_part_of_rmw && process_read(act))
1487 if (act->is_write() && process_write(act))
1490 if (act->is_fence() && process_fence(act))
1493 if (act->is_mutex_op() && process_mutex(act))
1496 if (act->is_relseq_fixup())
1497 process_relseq_fixup(curr, &work_queue);
1500 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1502 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1505 case WORK_CHECK_RELEASE_SEQ:
1506 resolve_release_sequences(work.location, &work_queue);
1508 case WORK_CHECK_MO_EDGES: {
1509 /** @todo Complete verification of work_queue */
1510 ModelAction *act = work.action;
1511 bool updated = false;
1513 if (act->is_read()) {
1514 const ModelAction *rf = act->get_reads_from();
1515 const Promise *promise = act->get_reads_from_promise();
1517 if (r_modification_order(act, rf))
1519 } else if (promise) {
1520 if (r_modification_order(act, promise))
1524 if (act->is_write()) {
1525 if (w_modification_order(act, NULL))
1528 mo_graph->commitChanges();
1531 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1540 check_curr_backtracking(curr);
1541 set_backtracking(curr);
1545 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1547 Node *currnode = curr->get_node();
1548 Node *parnode = currnode->get_parent();
1550 if ((parnode && !parnode->backtrack_empty()) ||
1551 !currnode->misc_empty() ||
1552 !currnode->read_from_empty() ||
1553 !currnode->promise_empty() ||
1554 !currnode->relseq_break_empty()) {
1555 set_latest_backtrack(curr);
1559 bool ModelChecker::promises_expired() const
1561 for (unsigned int i = 0; i < promises->size(); i++) {
1562 Promise *promise = (*promises)[i];
1563 if (promise->get_expiration() < priv->used_sequence_numbers)
1570 * This is the strongest feasibility check available.
1571 * @return whether the current trace (partial or complete) must be a prefix of
1574 bool ModelChecker::isfeasibleprefix() const
1576 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1580 * Print disagnostic information about an infeasible execution
1581 * @param prefix A string to prefix the output with; if NULL, then a default
1582 * message prefix will be provided
1584 void ModelChecker::print_infeasibility(const char *prefix) const
1588 if (mo_graph->checkForCycles())
1589 ptr += sprintf(ptr, "[mo cycle]");
1590 if (priv->failed_promise)
1591 ptr += sprintf(ptr, "[failed promise]");
1592 if (priv->too_many_reads)
1593 ptr += sprintf(ptr, "[too many reads]");
1594 if (priv->no_valid_reads)
1595 ptr += sprintf(ptr, "[no valid reads-from]");
1596 if (priv->bad_synchronization)
1597 ptr += sprintf(ptr, "[bad sw ordering]");
1598 if (promises_expired())
1599 ptr += sprintf(ptr, "[promise expired]");
1600 if (promises->size() != 0)
1601 ptr += sprintf(ptr, "[unresolved promise]");
1603 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1607 * Returns whether the current completed trace is feasible, except for pending
1608 * release sequences.
1610 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1612 return !is_infeasible() && promises->size() == 0;
1616 * Check if the current partial trace is infeasible. Does not check any
1617 * end-of-execution flags, which might rule out the execution. Thus, this is
1618 * useful only for ruling an execution as infeasible.
1619 * @return whether the current partial trace is infeasible.
1621 bool ModelChecker::is_infeasible() const
1623 return mo_graph->checkForCycles() ||
1624 priv->no_valid_reads ||
1625 priv->failed_promise ||
1626 priv->too_many_reads ||
1627 priv->bad_synchronization ||
1631 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1632 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1633 ModelAction *lastread = get_last_action(act->get_tid());
1634 lastread->process_rmw(act);
1635 if (act->is_rmw()) {
1636 if (lastread->get_reads_from())
1637 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1639 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1640 mo_graph->commitChanges();
1646 * Checks whether a thread has read from the same write for too many times
1647 * without seeing the effects of a later write.
1650 * 1) there must a different write that we could read from that would satisfy the modification order,
1651 * 2) we must have read from the same value in excess of maxreads times, and
1652 * 3) that other write must have been in the reads_from set for maxreads times.
1654 * If so, we decide that the execution is no longer feasible.
1656 * @param curr The current action. Must be a read.
1657 * @param rf The store from which we might read.
1658 * @return True if the read should succeed; false otherwise
1660 bool ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) const
1662 if (!params.maxreads)
1665 //NOTE: Next check is just optimization, not really necessary....
1666 if (curr->get_node()->get_read_from_past_size() <= 1)
1669 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1670 int tid = id_to_int(curr->get_tid());
1671 ASSERT(tid < (int)thrd_lists->size());
1672 action_list_t *list = &(*thrd_lists)[tid];
1673 action_list_t::reverse_iterator rit = list->rbegin();
1674 ASSERT((*rit) == curr);
1675 /* Skip past curr */
1678 action_list_t::reverse_iterator ritcopy = rit;
1679 /* See if we have enough reads from the same value */
1680 for (int count = 0; count < params.maxreads; ritcopy++, count++) {
1681 if (ritcopy == list->rend())
1683 ModelAction *act = *ritcopy;
1684 if (!act->is_read())
1686 if (act->get_reads_from() != rf)
1688 if (act->get_node()->get_read_from_past_size() <= 1)
1691 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1693 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1695 /* Need a different write */
1699 /* Only look for "newer" writes */
1700 if (!mo_graph->checkReachable(rf, write))
1705 bool feasiblewrite = true;
1706 /* now we need to see if this write works for everyone */
1707 for (int loop = params.maxreads; loop > 0; loop--, ritcopy++) {
1708 ModelAction *act = *ritcopy;
1709 if (!act->may_read_from(write)) {
1710 feasiblewrite = false;
1721 * Updates the mo_graph with the constraints imposed from the current
1724 * Basic idea is the following: Go through each other thread and find
1725 * the last action that happened before our read. Two cases:
1727 * (1) The action is a write => that write must either occur before
1728 * the write we read from or be the write we read from.
1730 * (2) The action is a read => the write that that action read from
1731 * must occur before the write we read from or be the same write.
1733 * @param curr The current action. Must be a read.
1734 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1735 * @return True if modification order edges were added; false otherwise
1737 template <typename rf_type>
1738 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1740 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1743 ASSERT(curr->is_read());
1745 /* Last SC fence in the current thread */
1746 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1748 /* Iterate over all threads */
1749 for (i = 0; i < thrd_lists->size(); i++) {
1750 /* Last SC fence in thread i */
1751 ModelAction *last_sc_fence_thread_local = NULL;
1752 if (int_to_id((int)i) != curr->get_tid())
1753 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1755 /* Last SC fence in thread i, before last SC fence in current thread */
1756 ModelAction *last_sc_fence_thread_before = NULL;
1757 if (last_sc_fence_local)
1758 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1760 /* Iterate over actions in thread, starting from most recent */
1761 action_list_t *list = &(*thrd_lists)[i];
1762 action_list_t::reverse_iterator rit;
1763 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1764 ModelAction *act = *rit;
1766 if (act->is_write() && !act->equals(rf) && act != curr) {
1767 /* C++, Section 29.3 statement 5 */
1768 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1769 *act < *last_sc_fence_thread_local) {
1770 added = mo_graph->addEdge(act, rf) || added;
1773 /* C++, Section 29.3 statement 4 */
1774 else if (act->is_seqcst() && last_sc_fence_local &&
1775 *act < *last_sc_fence_local) {
1776 added = mo_graph->addEdge(act, rf) || added;
1779 /* C++, Section 29.3 statement 6 */
1780 else if (last_sc_fence_thread_before &&
1781 *act < *last_sc_fence_thread_before) {
1782 added = mo_graph->addEdge(act, rf) || added;
1788 * Include at most one act per-thread that "happens
1789 * before" curr. Don't consider reflexively.
1791 if (act->happens_before(curr) && act != curr) {
1792 if (act->is_write()) {
1793 if (!act->equals(rf)) {
1794 added = mo_graph->addEdge(act, rf) || added;
1797 const ModelAction *prevrf = act->get_reads_from();
1798 const Promise *prevrf_promise = act->get_reads_from_promise();
1800 if (!prevrf->equals(rf))
1801 added = mo_graph->addEdge(prevrf, rf) || added;
1802 } else if (!prevrf_promise->equals(rf)) {
1803 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1812 * All compatible, thread-exclusive promises must be ordered after any
1813 * concrete loads from the same thread
1815 for (unsigned int i = 0; i < promises->size(); i++)
1816 if ((*promises)[i]->is_compatible_exclusive(curr))
1817 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1823 * Updates the mo_graph with the constraints imposed from the current write.
1825 * Basic idea is the following: Go through each other thread and find
1826 * the lastest action that happened before our write. Two cases:
1828 * (1) The action is a write => that write must occur before
1831 * (2) The action is a read => the write that that action read from
1832 * must occur before the current write.
1834 * This method also handles two other issues:
1836 * (I) Sequential Consistency: Making sure that if the current write is
1837 * seq_cst, that it occurs after the previous seq_cst write.
1839 * (II) Sending the write back to non-synchronizing reads.
1841 * @param curr The current action. Must be a write.
1842 * @param send_fv A vector for stashing reads to which we may pass our future
1843 * value. If NULL, then don't record any future values.
1844 * @return True if modification order edges were added; false otherwise
1846 bool ModelChecker::w_modification_order(ModelAction *curr, std::vector< ModelAction *, ModelAlloc<ModelAction *> > *send_fv)
1848 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1851 ASSERT(curr->is_write());
1853 if (curr->is_seqcst()) {
1854 /* We have to at least see the last sequentially consistent write,
1855 so we are initialized. */
1856 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1857 if (last_seq_cst != NULL) {
1858 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1862 /* Last SC fence in the current thread */
1863 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1865 /* Iterate over all threads */
1866 for (i = 0; i < thrd_lists->size(); i++) {
1867 /* Last SC fence in thread i, before last SC fence in current thread */
1868 ModelAction *last_sc_fence_thread_before = NULL;
1869 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1870 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1872 /* Iterate over actions in thread, starting from most recent */
1873 action_list_t *list = &(*thrd_lists)[i];
1874 action_list_t::reverse_iterator rit;
1875 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1876 ModelAction *act = *rit;
1879 * 1) If RMW and it actually read from something, then we
1880 * already have all relevant edges, so just skip to next
1883 * 2) If RMW and it didn't read from anything, we should
1884 * whatever edge we can get to speed up convergence.
1886 * 3) If normal write, we need to look at earlier actions, so
1887 * continue processing list.
1889 if (curr->is_rmw()) {
1890 if (curr->get_reads_from() != NULL)
1898 /* C++, Section 29.3 statement 7 */
1899 if (last_sc_fence_thread_before && act->is_write() &&
1900 *act < *last_sc_fence_thread_before) {
1901 added = mo_graph->addEdge(act, curr) || added;
1906 * Include at most one act per-thread that "happens
1909 if (act->happens_before(curr)) {
1911 * Note: if act is RMW, just add edge:
1913 * The following edge should be handled elsewhere:
1914 * readfrom(act) --mo--> act
1916 if (act->is_write())
1917 added = mo_graph->addEdge(act, curr) || added;
1918 else if (act->is_read()) {
1919 //if previous read accessed a null, just keep going
1920 if (act->get_reads_from() == NULL)
1922 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1925 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1926 !act->same_thread(curr)) {
1927 /* We have an action that:
1928 (1) did not happen before us
1929 (2) is a read and we are a write
1930 (3) cannot synchronize with us
1931 (4) is in a different thread
1933 that read could potentially read from our write. Note that
1934 these checks are overly conservative at this point, we'll
1935 do more checks before actually removing the
1939 if (send_fv && thin_air_constraint_may_allow(curr, act)) {
1940 if (!is_infeasible())
1941 send_fv->push_back(act);
1942 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1943 add_future_value(curr, act);
1950 * All compatible, thread-exclusive promises must be ordered after any
1951 * concrete stores to the same thread, or else they can be merged with
1954 for (unsigned int i = 0; i < promises->size(); i++)
1955 if ((*promises)[i]->is_compatible_exclusive(curr))
1956 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1961 /** Arbitrary reads from the future are not allowed. Section 29.3
1962 * part 9 places some constraints. This method checks one result of constraint
1963 * constraint. Others require compiler support. */
1964 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1966 if (!writer->is_rmw())
1969 if (!reader->is_rmw())
1972 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1973 if (search == reader)
1975 if (search->get_tid() == reader->get_tid() &&
1976 search->happens_before(reader))
1984 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1985 * some constraints. This method checks one the following constraint (others
1986 * require compiler support):
1988 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1990 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1992 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1994 /* Iterate over all threads */
1995 for (i = 0; i < thrd_lists->size(); i++) {
1996 const ModelAction *write_after_read = NULL;
1998 /* Iterate over actions in thread, starting from most recent */
1999 action_list_t *list = &(*thrd_lists)[i];
2000 action_list_t::reverse_iterator rit;
2001 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2002 ModelAction *act = *rit;
2004 /* Don't disallow due to act == reader */
2005 if (!reader->happens_before(act) || reader == act)
2007 else if (act->is_write())
2008 write_after_read = act;
2009 else if (act->is_read() && act->get_reads_from() != NULL)
2010 write_after_read = act->get_reads_from();
2013 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
2020 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
2021 * The ModelAction under consideration is expected to be taking part in
2022 * release/acquire synchronization as an object of the "reads from" relation.
2023 * Note that this can only provide release sequence support for RMW chains
2024 * which do not read from the future, as those actions cannot be traced until
2025 * their "promise" is fulfilled. Similarly, we may not even establish the
2026 * presence of a release sequence with certainty, as some modification order
2027 * constraints may be decided further in the future. Thus, this function
2028 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
2029 * and a boolean representing certainty.
2031 * @param rf The action that might be part of a release sequence. Must be a
2033 * @param release_heads A pass-by-reference style return parameter. After
2034 * execution of this function, release_heads will contain the heads of all the
2035 * relevant release sequences, if any exists with certainty
2036 * @param pending A pass-by-reference style return parameter which is only used
2037 * when returning false (i.e., uncertain). Returns most information regarding
2038 * an uncertain release sequence, including any write operations that might
2039 * break the sequence.
2040 * @return true, if the ModelChecker is certain that release_heads is complete;
2043 bool ModelChecker::release_seq_heads(const ModelAction *rf,
2044 rel_heads_list_t *release_heads,
2045 struct release_seq *pending) const
2047 /* Only check for release sequences if there are no cycles */
2048 if (mo_graph->checkForCycles())
2051 for ( ; rf != NULL; rf = rf->get_reads_from()) {
2052 ASSERT(rf->is_write());
2054 if (rf->is_release())
2055 release_heads->push_back(rf);
2056 else if (rf->get_last_fence_release())
2057 release_heads->push_back(rf->get_last_fence_release());
2059 break; /* End of RMW chain */
2061 /** @todo Need to be smarter here... In the linux lock
2062 * example, this will run to the beginning of the program for
2064 /** @todo The way to be smarter here is to keep going until 1
2065 * thread has a release preceded by an acquire and you've seen
2068 /* acq_rel RMW is a sufficient stopping condition */
2069 if (rf->is_acquire() && rf->is_release())
2070 return true; /* complete */
2073 /* read from future: need to settle this later */
2075 return false; /* incomplete */
2078 if (rf->is_release())
2079 return true; /* complete */
2081 /* else relaxed write
2082 * - check for fence-release in the same thread (29.8, stmt. 3)
2083 * - check modification order for contiguous subsequence
2084 * -> rf must be same thread as release */
2086 const ModelAction *fence_release = rf->get_last_fence_release();
2087 /* Synchronize with a fence-release unconditionally; we don't need to
2088 * find any more "contiguous subsequence..." for it */
2090 release_heads->push_back(fence_release);
2092 int tid = id_to_int(rf->get_tid());
2093 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
2094 action_list_t *list = &(*thrd_lists)[tid];
2095 action_list_t::const_reverse_iterator rit;
2097 /* Find rf in the thread list */
2098 rit = std::find(list->rbegin(), list->rend(), rf);
2099 ASSERT(rit != list->rend());
2101 /* Find the last {write,fence}-release */
2102 for (; rit != list->rend(); rit++) {
2103 if (fence_release && *(*rit) < *fence_release)
2105 if ((*rit)->is_release())
2108 if (rit == list->rend()) {
2109 /* No write-release in this thread */
2110 return true; /* complete */
2111 } else if (fence_release && *(*rit) < *fence_release) {
2112 /* The fence-release is more recent (and so, "stronger") than
2113 * the most recent write-release */
2114 return true; /* complete */
2115 } /* else, need to establish contiguous release sequence */
2116 ModelAction *release = *rit;
2118 ASSERT(rf->same_thread(release));
2120 pending->writes.clear();
2122 bool certain = true;
2123 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2124 if (id_to_int(rf->get_tid()) == (int)i)
2126 list = &(*thrd_lists)[i];
2128 /* Can we ensure no future writes from this thread may break
2129 * the release seq? */
2130 bool future_ordered = false;
2132 ModelAction *last = get_last_action(int_to_id(i));
2133 Thread *th = get_thread(int_to_id(i));
2134 if ((last && rf->happens_before(last)) ||
2137 future_ordered = true;
2139 ASSERT(!th->is_model_thread() || future_ordered);
2141 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2142 const ModelAction *act = *rit;
2143 /* Reach synchronization -> this thread is complete */
2144 if (act->happens_before(release))
2146 if (rf->happens_before(act)) {
2147 future_ordered = true;
2151 /* Only non-RMW writes can break release sequences */
2152 if (!act->is_write() || act->is_rmw())
2155 /* Check modification order */
2156 if (mo_graph->checkReachable(rf, act)) {
2157 /* rf --mo--> act */
2158 future_ordered = true;
2161 if (mo_graph->checkReachable(act, release))
2162 /* act --mo--> release */
2164 if (mo_graph->checkReachable(release, act) &&
2165 mo_graph->checkReachable(act, rf)) {
2166 /* release --mo-> act --mo--> rf */
2167 return true; /* complete */
2169 /* act may break release sequence */
2170 pending->writes.push_back(act);
2173 if (!future_ordered)
2174 certain = false; /* This thread is uncertain */
2178 release_heads->push_back(release);
2179 pending->writes.clear();
2181 pending->release = release;
2188 * An interface for getting the release sequence head(s) with which a
2189 * given ModelAction must synchronize. This function only returns a non-empty
2190 * result when it can locate a release sequence head with certainty. Otherwise,
2191 * it may mark the internal state of the ModelChecker so that it will handle
2192 * the release sequence at a later time, causing @a acquire to update its
2193 * synchronization at some later point in execution.
2195 * @param acquire The 'acquire' action that may synchronize with a release
2197 * @param read The read action that may read from a release sequence; this may
2198 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2199 * when 'acquire' is a fence-acquire)
2200 * @param release_heads A pass-by-reference return parameter. Will be filled
2201 * with the head(s) of the release sequence(s), if they exists with certainty.
2202 * @see ModelChecker::release_seq_heads
2204 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2205 ModelAction *read, rel_heads_list_t *release_heads)
2207 const ModelAction *rf = read->get_reads_from();
2208 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2209 sequence->acquire = acquire;
2210 sequence->read = read;
2212 if (!release_seq_heads(rf, release_heads, sequence)) {
2213 /* add act to 'lazy checking' list */
2214 pending_rel_seqs->push_back(sequence);
2216 snapshot_free(sequence);
2221 * Attempt to resolve all stashed operations that might synchronize with a
2222 * release sequence for a given location. This implements the "lazy" portion of
2223 * determining whether or not a release sequence was contiguous, since not all
2224 * modification order information is present at the time an action occurs.
2226 * @param location The location/object that should be checked for release
2227 * sequence resolutions. A NULL value means to check all locations.
2228 * @param work_queue The work queue to which to add work items as they are
2230 * @return True if any updates occurred (new synchronization, new mo_graph
2233 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2235 bool updated = false;
2236 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2237 while (it != pending_rel_seqs->end()) {
2238 struct release_seq *pending = *it;
2239 ModelAction *acquire = pending->acquire;
2240 const ModelAction *read = pending->read;
2242 /* Only resolve sequences on the given location, if provided */
2243 if (location && read->get_location() != location) {
2248 const ModelAction *rf = read->get_reads_from();
2249 rel_heads_list_t release_heads;
2251 complete = release_seq_heads(rf, &release_heads, pending);
2252 for (unsigned int i = 0; i < release_heads.size(); i++) {
2253 if (!acquire->has_synchronized_with(release_heads[i])) {
2254 if (acquire->synchronize_with(release_heads[i]))
2257 set_bad_synchronization();
2262 /* Re-check all pending release sequences */
2263 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2264 /* Re-check read-acquire for mo_graph edges */
2265 if (acquire->is_read())
2266 work_queue->push_back(MOEdgeWorkEntry(acquire));
2268 /* propagate synchronization to later actions */
2269 action_list_t::reverse_iterator rit = action_trace->rbegin();
2270 for (; (*rit) != acquire; rit++) {
2271 ModelAction *propagate = *rit;
2272 if (acquire->happens_before(propagate)) {
2273 propagate->synchronize_with(acquire);
2274 /* Re-check 'propagate' for mo_graph edges */
2275 work_queue->push_back(MOEdgeWorkEntry(propagate));
2280 it = pending_rel_seqs->erase(it);
2281 snapshot_free(pending);
2287 // If we resolved promises or data races, see if we have realized a data race.
2294 * Performs various bookkeeping operations for the current ModelAction. For
2295 * instance, adds action to the per-object, per-thread action vector and to the
2296 * action trace list of all thread actions.
2298 * @param act is the ModelAction to add.
2300 void ModelChecker::add_action_to_lists(ModelAction *act)
2302 int tid = id_to_int(act->get_tid());
2303 ModelAction *uninit = NULL;
2305 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2306 if (list->empty() && act->is_atomic_var()) {
2307 uninit = new_uninitialized_action(act->get_location());
2308 uninit_id = id_to_int(uninit->get_tid());
2309 list->push_back(uninit);
2311 list->push_back(act);
2313 action_trace->push_back(act);
2315 action_trace->push_front(uninit);
2317 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2318 if (tid >= (int)vec->size())
2319 vec->resize(priv->next_thread_id);
2320 (*vec)[tid].push_back(act);
2322 (*vec)[uninit_id].push_front(uninit);
2324 if ((int)thrd_last_action->size() <= tid)
2325 thrd_last_action->resize(get_num_threads());
2326 (*thrd_last_action)[tid] = act;
2328 (*thrd_last_action)[uninit_id] = uninit;
2330 if (act->is_fence() && act->is_release()) {
2331 if ((int)thrd_last_fence_release->size() <= tid)
2332 thrd_last_fence_release->resize(get_num_threads());
2333 (*thrd_last_fence_release)[tid] = act;
2336 if (act->is_wait()) {
2337 void *mutex_loc = (void *) act->get_value();
2338 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2340 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2341 if (tid >= (int)vec->size())
2342 vec->resize(priv->next_thread_id);
2343 (*vec)[tid].push_back(act);
2348 * @brief Get the last action performed by a particular Thread
2349 * @param tid The thread ID of the Thread in question
2350 * @return The last action in the thread
2352 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2354 int threadid = id_to_int(tid);
2355 if (threadid < (int)thrd_last_action->size())
2356 return (*thrd_last_action)[id_to_int(tid)];
2362 * @brief Get the last fence release performed by a particular Thread
2363 * @param tid The thread ID of the Thread in question
2364 * @return The last fence release in the thread, if one exists; NULL otherwise
2366 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2368 int threadid = id_to_int(tid);
2369 if (threadid < (int)thrd_last_fence_release->size())
2370 return (*thrd_last_fence_release)[id_to_int(tid)];
2376 * Gets the last memory_order_seq_cst write (in the total global sequence)
2377 * performed on a particular object (i.e., memory location), not including the
2379 * @param curr The current ModelAction; also denotes the object location to
2381 * @return The last seq_cst write
2383 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2385 void *location = curr->get_location();
2386 action_list_t *list = get_safe_ptr_action(obj_map, location);
2387 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2388 action_list_t::reverse_iterator rit;
2389 for (rit = list->rbegin(); rit != list->rend(); rit++)
2390 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2396 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2397 * performed in a particular thread, prior to a particular fence.
2398 * @param tid The ID of the thread to check
2399 * @param before_fence The fence from which to begin the search; if NULL, then
2400 * search for the most recent fence in the thread.
2401 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2403 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2405 /* All fences should have NULL location */
2406 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2407 action_list_t::reverse_iterator rit = list->rbegin();
2410 for (; rit != list->rend(); rit++)
2411 if (*rit == before_fence)
2414 ASSERT(*rit == before_fence);
2418 for (; rit != list->rend(); rit++)
2419 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2425 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2426 * location). This function identifies the mutex according to the current
2427 * action, which is presumed to perform on the same mutex.
2428 * @param curr The current ModelAction; also denotes the object location to
2430 * @return The last unlock operation
2432 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2434 void *location = curr->get_location();
2435 action_list_t *list = get_safe_ptr_action(obj_map, location);
2436 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2437 action_list_t::reverse_iterator rit;
2438 for (rit = list->rbegin(); rit != list->rend(); rit++)
2439 if ((*rit)->is_unlock() || (*rit)->is_wait())
2444 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2446 ModelAction *parent = get_last_action(tid);
2448 parent = get_thread(tid)->get_creation();
2453 * Returns the clock vector for a given thread.
2454 * @param tid The thread whose clock vector we want
2455 * @return Desired clock vector
2457 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2459 return get_parent_action(tid)->get_cv();
2463 * @brief Find the promise, if any to resolve for the current action
2464 * @param curr The current ModelAction. Should be a write.
2465 * @return The (non-negative) index for the Promise to resolve, if any;
2468 int ModelChecker::get_promise_to_resolve(const ModelAction *curr) const
2470 for (unsigned int i = 0; i < promises->size(); i++)
2471 if (curr->get_node()->get_promise(i))
2477 * Resolve a Promise with a current write.
2478 * @param write The ModelAction that is fulfilling Promises
2479 * @param promise_idx The index corresponding to the promise
2480 * @return True if the Promise was successfully resolved; false otherwise
2482 bool ModelChecker::resolve_promise(ModelAction *write, unsigned int promise_idx)
2484 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2485 promise_list_t mustResolve;
2486 Promise *promise = (*promises)[promise_idx];
2488 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2489 ModelAction *read = promise->get_reader(i);
2490 read_from(read, write);
2491 actions_to_check.push_back(read);
2493 /* Make sure the promise's value matches the write's value */
2494 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2495 mo_graph->resolvePromise(promise, write, &mustResolve);
2497 promises->erase(promises->begin() + promise_idx);
2499 /** @todo simplify the 'mustResolve' stuff */
2500 ASSERT(mustResolve.size() <= 1);
2502 if (!mustResolve.empty() && mustResolve[0] != promise)
2503 priv->failed_promise = true;
2506 //Check whether reading these writes has made threads unable to
2509 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2510 ModelAction *read = actions_to_check[i];
2511 mo_check_promises(read, true);
2518 * Compute the set of promises that could potentially be satisfied by this
2519 * action. Note that the set computation actually appears in the Node, not in
2521 * @param curr The ModelAction that may satisfy promises
2523 void ModelChecker::compute_promises(ModelAction *curr)
2525 for (unsigned int i = 0; i < promises->size(); i++) {
2526 Promise *promise = (*promises)[i];
2527 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2530 bool satisfy = true;
2531 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2532 const ModelAction *act = promise->get_reader(j);
2533 if (act->happens_before(curr) ||
2534 act->could_synchronize_with(curr)) {
2540 curr->get_node()->set_promise(i);
2544 /** Checks promises in response to change in ClockVector Threads. */
2545 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2547 for (unsigned int i = 0; i < promises->size(); i++) {
2548 Promise *promise = (*promises)[i];
2549 if (!promise->thread_is_available(tid))
2551 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2552 const ModelAction *act = promise->get_reader(j);
2553 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2554 merge_cv->synchronized_since(act)) {
2555 if (promise->eliminate_thread(tid)) {
2556 /* Promise has failed */
2557 priv->failed_promise = true;
2565 void ModelChecker::check_promises_thread_disabled()
2567 for (unsigned int i = 0; i < promises->size(); i++) {
2568 Promise *promise = (*promises)[i];
2569 if (promise->has_failed()) {
2570 priv->failed_promise = true;
2577 * @brief Checks promises in response to addition to modification order for
2580 * We test whether threads are still available for satisfying promises after an
2581 * addition to our modification order constraints. Those that are unavailable
2582 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2583 * that promise has failed.
2585 * @param act The ModelAction which updated the modification order
2586 * @param is_read_check Should be true if act is a read and we must check for
2587 * updates to the store from which it read (there is a distinction here for
2588 * RMW's, which are both a load and a store)
2590 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2592 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2594 for (unsigned int i = 0; i < promises->size(); i++) {
2595 Promise *promise = (*promises)[i];
2597 // Is this promise on the same location?
2598 if (!promise->same_location(write))
2601 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2602 const ModelAction *pread = promise->get_reader(j);
2603 if (!pread->happens_before(act))
2605 if (mo_graph->checkPromise(write, promise)) {
2606 priv->failed_promise = true;
2612 // Don't do any lookups twice for the same thread
2613 if (!promise->thread_is_available(act->get_tid()))
2616 if (mo_graph->checkReachable(promise, write)) {
2617 if (mo_graph->checkPromise(write, promise)) {
2618 priv->failed_promise = true;
2626 * Compute the set of writes that may break the current pending release
2627 * sequence. This information is extracted from previou release sequence
2630 * @param curr The current ModelAction. Must be a release sequence fixup
2633 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2635 if (pending_rel_seqs->empty())
2638 struct release_seq *pending = pending_rel_seqs->back();
2639 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2640 const ModelAction *write = pending->writes[i];
2641 curr->get_node()->add_relseq_break(write);
2644 /* NULL means don't break the sequence; just synchronize */
2645 curr->get_node()->add_relseq_break(NULL);
2649 * Build up an initial set of all past writes that this 'read' action may read
2650 * from, as well as any previously-observed future values that must still be valid.
2652 * @param curr is the current ModelAction that we are exploring; it must be a
2655 void ModelChecker::build_may_read_from(ModelAction *curr)
2657 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2659 ASSERT(curr->is_read());
2661 ModelAction *last_sc_write = NULL;
2663 if (curr->is_seqcst())
2664 last_sc_write = get_last_seq_cst_write(curr);
2666 /* Iterate over all threads */
2667 for (i = 0; i < thrd_lists->size(); i++) {
2668 /* Iterate over actions in thread, starting from most recent */
2669 action_list_t *list = &(*thrd_lists)[i];
2670 action_list_t::reverse_iterator rit;
2671 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2672 ModelAction *act = *rit;
2674 /* Only consider 'write' actions */
2675 if (!act->is_write() || act == curr)
2678 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2679 bool allow_read = true;
2681 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2683 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2687 /* Only add feasible reads */
2688 mo_graph->startChanges();
2689 r_modification_order(curr, act);
2690 if (!is_infeasible())
2691 curr->get_node()->add_read_from_past(act);
2692 mo_graph->rollbackChanges();
2695 /* Include at most one act per-thread that "happens before" curr */
2696 if (act->happens_before(curr))
2701 /* Inherit existing, promised future values */
2702 for (i = 0; i < promises->size(); i++) {
2703 const Promise *promise = (*promises)[i];
2704 const ModelAction *promise_read = promise->get_reader(0);
2705 if (promise_read->same_var(curr)) {
2706 /* Only add feasible future-values */
2707 mo_graph->startChanges();
2708 r_modification_order(curr, promise);
2709 if (!is_infeasible())
2710 curr->get_node()->add_read_from_promise(promise_read);
2711 mo_graph->rollbackChanges();
2715 /* We may find no valid may-read-from only if the execution is doomed */
2716 if (!curr->get_node()->read_from_size()) {
2717 priv->no_valid_reads = true;
2721 if (DBG_ENABLED()) {
2722 model_print("Reached read action:\n");
2724 model_print("Printing read_from_past\n");
2725 curr->get_node()->print_read_from_past();
2726 model_print("End printing read_from_past\n");
2730 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2732 for ( ; write != NULL; write = write->get_reads_from()) {
2733 /* UNINIT actions don't have a Node, and they never sleep */
2734 if (write->is_uninitialized())
2736 Node *prevnode = write->get_node()->get_parent();
2738 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2739 if (write->is_release() && thread_sleep)
2741 if (!write->is_rmw())
2748 * @brief Create a new action representing an uninitialized atomic
2749 * @param location The memory location of the atomic object
2750 * @return A pointer to a new ModelAction
2752 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2754 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2755 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2756 act->create_cv(NULL);
2760 static void print_list(action_list_t *list)
2762 action_list_t::iterator it;
2764 model_print("---------------------------------------------------------------------\n");
2766 unsigned int hash = 0;
2768 for (it = list->begin(); it != list->end(); it++) {
2770 hash = hash^(hash<<3)^((*it)->hash());
2772 model_print("HASH %u\n", hash);
2773 model_print("---------------------------------------------------------------------\n");
2776 #if SUPPORT_MOD_ORDER_DUMP
2777 void ModelChecker::dumpGraph(char *filename) const
2780 sprintf(buffer, "%s.dot", filename);
2781 FILE *file = fopen(buffer, "w");
2782 fprintf(file, "digraph %s {\n", filename);
2783 mo_graph->dumpNodes(file);
2784 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2786 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2787 ModelAction *act = *it;
2788 if (act->is_read()) {
2789 mo_graph->dot_print_node(file, act);
2790 if (act->get_reads_from())
2791 mo_graph->dot_print_edge(file,
2792 act->get_reads_from(),
2794 "label=\"rf\", color=red, weight=2");
2796 mo_graph->dot_print_edge(file,
2797 act->get_reads_from_promise(),
2799 "label=\"rf\", color=red");
2801 if (thread_array[act->get_tid()]) {
2802 mo_graph->dot_print_edge(file,
2803 thread_array[id_to_int(act->get_tid())],
2805 "label=\"sb\", color=blue, weight=400");
2808 thread_array[act->get_tid()] = act;
2810 fprintf(file, "}\n");
2811 model_free(thread_array);
2816 /** @brief Prints an execution trace summary. */
2817 void ModelChecker::print_summary() const
2819 #if SUPPORT_MOD_ORDER_DUMP
2820 char buffername[100];
2821 sprintf(buffername, "exec%04u", stats.num_total);
2822 mo_graph->dumpGraphToFile(buffername);
2823 sprintf(buffername, "graph%04u", stats.num_total);
2824 dumpGraph(buffername);
2827 model_print("Execution %d:", stats.num_total);
2828 if (isfeasibleprefix()) {
2829 if (scheduler->all_threads_sleeping())
2830 model_print(" SLEEP-SET REDUNDANT");
2833 print_infeasibility(" INFEASIBLE");
2834 print_list(action_trace);
2839 * Add a Thread to the system for the first time. Should only be called once
2841 * @param t The Thread to add
2843 void ModelChecker::add_thread(Thread *t)
2845 thread_map->put(id_to_int(t->get_id()), t);
2846 scheduler->add_thread(t);
2850 * Removes a thread from the scheduler.
2851 * @param the thread to remove.
2853 void ModelChecker::remove_thread(Thread *t)
2855 scheduler->remove_thread(t);
2859 * @brief Get a Thread reference by its ID
2860 * @param tid The Thread's ID
2861 * @return A Thread reference
2863 Thread * ModelChecker::get_thread(thread_id_t tid) const
2865 return thread_map->get(id_to_int(tid));
2869 * @brief Get a reference to the Thread in which a ModelAction was executed
2870 * @param act The ModelAction
2871 * @return A Thread reference
2873 Thread * ModelChecker::get_thread(const ModelAction *act) const
2875 return get_thread(act->get_tid());
2879 * @brief Get a Promise's "promise number"
2881 * A "promise number" is an index number that is unique to a promise, valid
2882 * only for a specific snapshot of an execution trace. Promises may come and go
2883 * as they are generated an resolved, so an index only retains meaning for the
2886 * @param promise The Promise to check
2887 * @return The promise index, if the promise still is valid; otherwise -1
2889 int ModelChecker::get_promise_number(const Promise *promise) const
2891 for (unsigned int i = 0; i < promises->size(); i++)
2892 if ((*promises)[i] == promise)
2899 * @brief Check if a Thread is currently enabled
2900 * @param t The Thread to check
2901 * @return True if the Thread is currently enabled
2903 bool ModelChecker::is_enabled(Thread *t) const
2905 return scheduler->is_enabled(t);
2909 * @brief Check if a Thread is currently enabled
2910 * @param tid The ID of the Thread to check
2911 * @return True if the Thread is currently enabled
2913 bool ModelChecker::is_enabled(thread_id_t tid) const
2915 return scheduler->is_enabled(tid);
2919 * Switch from a model-checker context to a user-thread context. This is the
2920 * complement of ModelChecker::switch_to_master and must be called from the
2921 * model-checker context
2923 * @param thread The user-thread to switch to
2925 void ModelChecker::switch_from_master(Thread *thread)
2927 scheduler->set_current_thread(thread);
2928 Thread::swap(&system_context, thread);
2932 * Switch from a user-context to the "master thread" context (a.k.a. system
2933 * context). This switch is made with the intention of exploring a particular
2934 * model-checking action (described by a ModelAction object). Must be called
2935 * from a user-thread context.
2937 * @param act The current action that will be explored. May be NULL only if
2938 * trace is exiting via an assertion (see ModelChecker::set_assert and
2939 * ModelChecker::has_asserted).
2940 * @return Return the value returned by the current action
2942 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2945 Thread *old = thread_current();
2946 ASSERT(!old->get_pending());
2947 old->set_pending(act);
2948 if (Thread::swap(old, &system_context) < 0) {
2949 perror("swap threads");
2952 return old->get_return_value();
2956 * Takes the next step in the execution, if possible.
2957 * @param curr The current step to take
2958 * @return Returns the next Thread to run, if any; NULL if this execution
2961 Thread * ModelChecker::take_step(ModelAction *curr)
2963 Thread *curr_thrd = get_thread(curr);
2964 ASSERT(curr_thrd->get_state() == THREAD_READY);
2966 curr = check_current_action(curr);
2968 /* Infeasible -> don't take any more steps */
2969 if (is_infeasible())
2971 else if (isfeasibleprefix() && have_bug_reports()) {
2976 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2979 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2980 scheduler->remove_thread(curr_thrd);
2982 Thread *next_thrd = get_next_thread(curr);
2984 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2985 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2990 /** Wrapper to run the user's main function, with appropriate arguments */
2991 void user_main_wrapper(void *)
2993 user_main(model->params.argc, model->params.argv);
2996 /** @brief Run ModelChecker for the user program */
2997 void ModelChecker::run()
3001 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
3006 * Stash next pending action(s) for thread(s). There
3007 * should only need to stash one thread's action--the
3008 * thread which just took a step--plus the first step
3009 * for any newly-created thread
3011 for (unsigned int i = 0; i < get_num_threads(); i++) {
3012 thread_id_t tid = int_to_id(i);
3013 Thread *thr = get_thread(tid);
3014 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
3015 switch_from_master(thr);
3019 /* Catch assertions from prior take_step or from
3020 * between-ModelAction bugs (e.g., data races) */
3024 /* Consume the next action for a Thread */
3025 ModelAction *curr = t->get_pending();
3026 t->set_pending(NULL);
3027 t = take_step(curr);
3028 } while (t && !t->is_model_thread());
3031 * Launch end-of-execution release sequence fixups only when
3032 * the execution is otherwise feasible AND there are:
3034 * (1) pending release sequences
3035 * (2) pending assertions that could be invalidated by a change
3036 * in clock vectors (i.e., data races)
3037 * (3) no pending promises
3039 while (!pending_rel_seqs->empty() &&
3040 is_feasible_prefix_ignore_relseq() &&
3041 !unrealizedraces.empty()) {
3042 model_print("*** WARNING: release sequence fixup action "
3043 "(%zu pending release seuqence(s)) ***\n",
3044 pending_rel_seqs->size());
3045 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
3046 std::memory_order_seq_cst, NULL, VALUE_NONE,
3050 } while (next_execution());
3052 model_print("******* Model-checking complete: *******\n");