10 #include "snapshot-interface.h"
12 #include "clockvector.h"
13 #include "cyclegraph.h"
16 #include "threads-model.h"
19 #define INITIAL_THREAD_ID 0
24 bug_message(const char *str) {
25 const char *fmt = " [BUG] %s\n";
26 msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
27 sprintf(msg, fmt, str);
29 ~bug_message() { if (msg) snapshot_free(msg); }
32 void print() { model_print("%s", msg); }
38 * Structure for holding small ModelChecker members that should be snapshotted
40 struct model_snapshot_members {
41 model_snapshot_members() :
42 /* First thread created will have id INITIAL_THREAD_ID */
43 next_thread_id(INITIAL_THREAD_ID),
44 used_sequence_numbers(0),
48 failed_promise(false),
49 too_many_reads(false),
50 no_valid_reads(false),
51 bad_synchronization(false),
55 ~model_snapshot_members() {
56 for (unsigned int i = 0; i < bugs.size(); i++)
61 unsigned int next_thread_id;
62 modelclock_t used_sequence_numbers;
63 ModelAction *next_backtrack;
64 std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
65 struct execution_stats stats;
69 /** @brief Incorrectly-ordered synchronization was made */
70 bool bad_synchronization;
76 /** @brief Constructor */
77 ModelChecker::ModelChecker(struct model_params params) :
78 /* Initialize default scheduler */
80 scheduler(new Scheduler()),
82 earliest_diverge(NULL),
83 action_trace(new action_list_t()),
84 thread_map(new HashTable<int, Thread *, int>()),
85 obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
86 lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
87 condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
88 obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
89 promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
90 futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
91 pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
92 thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
93 thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
94 node_stack(new NodeStack()),
95 priv(new struct model_snapshot_members()),
96 mo_graph(new CycleGraph())
98 /* Initialize a model-checker thread, for special ModelActions */
99 model_thread = new Thread(get_next_id());
100 thread_map->put(id_to_int(model_thread->get_id()), model_thread);
103 /** @brief Destructor */
104 ModelChecker::~ModelChecker()
106 for (unsigned int i = 0; i < get_num_threads(); i++)
107 delete thread_map->get(i);
112 delete lock_waiters_map;
113 delete condvar_waiters_map;
116 for (unsigned int i = 0; i < promises->size(); i++)
117 delete (*promises)[i];
120 delete pending_rel_seqs;
122 delete thrd_last_action;
123 delete thrd_last_fence_release;
130 static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
132 action_list_t *tmp = hash->get(ptr);
134 tmp = new action_list_t();
140 static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
142 std::vector<action_list_t> *tmp = hash->get(ptr);
144 tmp = new std::vector<action_list_t>();
151 * Restores user program to initial state and resets all model-checker data
154 void ModelChecker::reset_to_initial_state()
156 DEBUG("+++ Resetting to initial state +++\n");
157 node_stack->reset_execution();
159 /* Print all model-checker output before rollback */
163 * FIXME: if we utilize partial rollback, we will need to free only
164 * those pending actions which were NOT pending before the rollback
167 for (unsigned int i = 0; i < get_num_threads(); i++)
168 delete get_thread(int_to_id(i))->get_pending();
170 snapshot_backtrack_before(0);
173 /** @return a thread ID for a new Thread */
174 thread_id_t ModelChecker::get_next_id()
176 return priv->next_thread_id++;
179 /** @return the number of user threads created during this execution */
180 unsigned int ModelChecker::get_num_threads() const
182 return priv->next_thread_id;
186 * Must be called from user-thread context (e.g., through the global
187 * thread_current() interface)
189 * @return The currently executing Thread.
191 Thread * ModelChecker::get_current_thread() const
193 return scheduler->get_current_thread();
196 /** @return a sequence number for a new ModelAction */
197 modelclock_t ModelChecker::get_next_seq_num()
199 return ++priv->used_sequence_numbers;
202 Node * ModelChecker::get_curr_node() const
204 return node_stack->get_head();
208 * @brief Choose the next thread to execute.
210 * This function chooses the next thread that should execute. It can force the
211 * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
212 * followed by a THREAD_START, or it can enforce execution replay/backtracking.
213 * The model-checker may have no preference regarding the next thread (i.e.,
214 * when exploring a new execution ordering), in which case we defer to the
217 * @param curr Optional: The current ModelAction. Only used if non-NULL and it
218 * might guide the choice of next thread (i.e., THREAD_CREATE should be
219 * followed by THREAD_START, or ATOMIC_RMWR followed by ATOMIC_{RMW,RMWC})
220 * @return The next chosen thread to run, if any exist. Or else if no threads
221 * remain to be executed, return NULL.
223 Thread * ModelChecker::get_next_thread(ModelAction *curr)
228 /* Do not split atomic actions. */
230 return get_thread(curr);
231 else if (curr->get_type() == THREAD_CREATE)
232 return curr->get_thread_operand();
236 * Have we completed exploring the preselected path? Then let the
240 return scheduler->select_next_thread();
242 /* Else, we are trying to replay an execution */
243 ModelAction *next = node_stack->get_next()->get_action();
245 if (next == diverge) {
246 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
247 earliest_diverge = diverge;
249 Node *nextnode = next->get_node();
250 Node *prevnode = nextnode->get_parent();
251 scheduler->update_sleep_set(prevnode);
253 /* Reached divergence point */
254 if (nextnode->increment_misc()) {
255 /* The next node will try to satisfy a different misc_index values. */
256 tid = next->get_tid();
257 node_stack->pop_restofstack(2);
258 } else if (nextnode->increment_promise()) {
259 /* The next node will try to satisfy a different set of promises. */
260 tid = next->get_tid();
261 node_stack->pop_restofstack(2);
262 } else if (nextnode->increment_read_from()) {
263 /* The next node will read from a different value. */
264 tid = next->get_tid();
265 node_stack->pop_restofstack(2);
266 } else if (nextnode->increment_relseq_break()) {
267 /* The next node will try to resolve a release sequence differently */
268 tid = next->get_tid();
269 node_stack->pop_restofstack(2);
272 /* Make a different thread execute for next step */
273 scheduler->add_sleep(get_thread(next->get_tid()));
274 tid = prevnode->get_next_backtrack();
275 /* Make sure the backtracked thread isn't sleeping. */
276 node_stack->pop_restofstack(1);
277 if (diverge == earliest_diverge) {
278 earliest_diverge = prevnode->get_action();
281 /* Start the round robin scheduler from this thread id */
282 scheduler->set_scheduler_thread(tid);
283 /* The correct sleep set is in the parent node. */
286 DEBUG("*** Divergence point ***\n");
290 tid = next->get_tid();
292 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
293 ASSERT(tid != THREAD_ID_T_NONE);
294 return thread_map->get(id_to_int(tid));
298 * We need to know what the next actions of all threads in the sleep
299 * set will be. This method computes them and stores the actions at
300 * the corresponding thread object's pending action.
303 void ModelChecker::execute_sleep_set()
305 for (unsigned int i = 0; i < get_num_threads(); i++) {
306 thread_id_t tid = int_to_id(i);
307 Thread *thr = get_thread(tid);
308 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
309 thr->get_pending()->set_sleep_flag();
315 * @brief Should the current action wake up a given thread?
317 * @param curr The current action
318 * @param thread The thread that we might wake up
319 * @return True, if we should wake up the sleeping thread; false otherwise
321 bool ModelChecker::should_wake_up(const ModelAction *curr, const Thread *thread) const
323 const ModelAction *asleep = thread->get_pending();
324 /* Don't allow partial RMW to wake anyone up */
327 /* Synchronizing actions may have been backtracked */
328 if (asleep->could_synchronize_with(curr))
330 /* All acquire/release fences and fence-acquire/store-release */
331 if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
333 /* Fence-release + store can awake load-acquire on the same location */
334 if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
335 ModelAction *fence_release = get_last_fence_release(curr->get_tid());
336 if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
342 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
344 for (unsigned int i = 0; i < get_num_threads(); i++) {
345 Thread *thr = get_thread(int_to_id(i));
346 if (scheduler->is_sleep_set(thr)) {
347 if (should_wake_up(curr, thr))
348 /* Remove this thread from sleep set */
349 scheduler->remove_sleep(thr);
354 /** @brief Alert the model-checker that an incorrectly-ordered
355 * synchronization was made */
356 void ModelChecker::set_bad_synchronization()
358 priv->bad_synchronization = true;
362 * Check whether the current trace has triggered an assertion which should halt
365 * @return True, if the execution should be aborted; false otherwise
367 bool ModelChecker::has_asserted() const
369 return priv->asserted;
373 * Trigger a trace assertion which should cause this execution to be halted.
374 * This can be due to a detected bug or due to an infeasibility that should
377 void ModelChecker::set_assert()
379 priv->asserted = true;
383 * Check if we are in a deadlock. Should only be called at the end of an
384 * execution, although it should not give false positives in the middle of an
385 * execution (there should be some ENABLED thread).
387 * @return True if program is in a deadlock; false otherwise
389 bool ModelChecker::is_deadlocked() const
391 bool blocking_threads = false;
392 for (unsigned int i = 0; i < get_num_threads(); i++) {
393 thread_id_t tid = int_to_id(i);
396 Thread *t = get_thread(tid);
397 if (!t->is_model_thread() && t->get_pending())
398 blocking_threads = true;
400 return blocking_threads;
404 * Check if this is a complete execution. That is, have all thread completed
405 * execution (rather than exiting because sleep sets have forced a redundant
408 * @return True if the execution is complete.
410 bool ModelChecker::is_complete_execution() const
412 for (unsigned int i = 0; i < get_num_threads(); i++)
413 if (is_enabled(int_to_id(i)))
419 * @brief Assert a bug in the executing program.
421 * Use this function to assert any sort of bug in the user program. If the
422 * current trace is feasible (actually, a prefix of some feasible execution),
423 * then this execution will be aborted, printing the appropriate message. If
424 * the current trace is not yet feasible, the error message will be stashed and
425 * printed if the execution ever becomes feasible.
427 * @param msg Descriptive message for the bug (do not include newline char)
428 * @return True if bug is immediately-feasible
430 bool ModelChecker::assert_bug(const char *msg)
432 priv->bugs.push_back(new bug_message(msg));
434 if (isfeasibleprefix()) {
442 * @brief Assert a bug in the executing program, asserted by a user thread
443 * @see ModelChecker::assert_bug
444 * @param msg Descriptive message for the bug (do not include newline char)
446 void ModelChecker::assert_user_bug(const char *msg)
448 /* If feasible bug, bail out now */
450 switch_to_master(NULL);
453 /** @return True, if any bugs have been reported for this execution */
454 bool ModelChecker::have_bug_reports() const
456 return priv->bugs.size() != 0;
459 /** @brief Print bug report listing for this execution (if any bugs exist) */
460 void ModelChecker::print_bugs() const
462 if (have_bug_reports()) {
463 model_print("Bug report: %zu bug%s detected\n",
465 priv->bugs.size() > 1 ? "s" : "");
466 for (unsigned int i = 0; i < priv->bugs.size(); i++)
467 priv->bugs[i]->print();
472 * @brief Record end-of-execution stats
474 * Must be run when exiting an execution. Records various stats.
475 * @see struct execution_stats
477 void ModelChecker::record_stats()
480 if (!isfeasibleprefix())
481 stats.num_infeasible++;
482 else if (have_bug_reports())
483 stats.num_buggy_executions++;
484 else if (is_complete_execution())
485 stats.num_complete++;
487 stats.num_redundant++;
490 /** @brief Print execution stats */
491 void ModelChecker::print_stats() const
493 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
494 model_print("Number of redundant executions: %d\n", stats.num_redundant);
495 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
496 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
497 model_print("Total executions: %d\n", stats.num_total);
498 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
502 * @brief End-of-exeuction print
503 * @param printbugs Should any existing bugs be printed?
505 void ModelChecker::print_execution(bool printbugs) const
507 print_program_output();
509 if (DBG_ENABLED() || params.verbose) {
510 model_print("Earliest divergence point since last feasible execution:\n");
511 if (earliest_diverge)
512 earliest_diverge->print();
514 model_print("(Not set)\n");
520 /* Don't print invalid bugs */
529 * Queries the model-checker for more executions to explore and, if one
530 * exists, resets the model-checker state to execute a new execution.
532 * @return If there are more executions to explore, return true. Otherwise,
535 bool ModelChecker::next_execution()
538 /* Is this execution a feasible execution that's worth bug-checking? */
539 bool complete = isfeasibleprefix() && (is_complete_execution() ||
542 /* End-of-execution bug checks */
545 assert_bug("Deadlock detected");
553 if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
554 print_execution(complete);
556 clear_program_output();
559 earliest_diverge = NULL;
561 if ((diverge = get_next_backtrack()) == NULL)
565 model_print("Next execution will diverge at:\n");
569 reset_to_initial_state();
574 * @brief Find the last fence-related backtracking conflict for a ModelAction
576 * This function performs the search for the most recent conflicting action
577 * against which we should perform backtracking, as affected by fence
578 * operations. This includes pairs of potentially-synchronizing actions which
579 * occur due to fence-acquire or fence-release, and hence should be explored in
580 * the opposite execution order.
582 * @param act The current action
583 * @return The most recent action which conflicts with act due to fences
585 ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const
587 /* Only perform release/acquire fence backtracking for stores */
588 if (!act->is_write())
591 /* Find a fence-release (or, act is a release) */
592 ModelAction *last_release;
593 if (act->is_release())
596 last_release = get_last_fence_release(act->get_tid());
600 /* Skip past the release */
601 action_list_t *list = action_trace;
602 action_list_t::reverse_iterator rit;
603 for (rit = list->rbegin(); rit != list->rend(); rit++)
604 if (*rit == last_release)
606 ASSERT(rit != list->rend());
611 * load --sb-> fence-acquire */
612 std::vector< ModelAction *, ModelAlloc<ModelAction *> > acquire_fences(get_num_threads(), NULL);
613 std::vector< ModelAction *, ModelAlloc<ModelAction *> > prior_loads(get_num_threads(), NULL);
614 bool found_acquire_fences = false;
615 for ( ; rit != list->rend(); rit++) {
616 ModelAction *prev = *rit;
617 if (act->same_thread(prev))
620 int tid = id_to_int(prev->get_tid());
622 if (prev->is_read() && act->same_var(prev)) {
623 if (prev->is_acquire()) {
624 /* Found most recent load-acquire, don't need
625 * to search for more fences */
626 if (!found_acquire_fences)
629 prior_loads[tid] = prev;
632 if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
633 found_acquire_fences = true;
634 acquire_fences[tid] = prev;
638 ModelAction *latest_backtrack = NULL;
639 for (unsigned int i = 0; i < acquire_fences.size(); i++)
640 if (acquire_fences[i] && prior_loads[i])
641 if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
642 latest_backtrack = acquire_fences[i];
643 return latest_backtrack;
647 * @brief Find the last backtracking conflict for a ModelAction
649 * This function performs the search for the most recent conflicting action
650 * against which we should perform backtracking. This primary includes pairs of
651 * synchronizing actions which should be explored in the opposite execution
654 * @param act The current action
655 * @return The most recent action which conflicts with act
657 ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const
659 switch (act->get_type()) {
660 /* case ATOMIC_FENCE: fences don't directly cause backtracking */
664 ModelAction *ret = NULL;
666 /* linear search: from most recent to oldest */
667 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
668 action_list_t::reverse_iterator rit;
669 for (rit = list->rbegin(); rit != list->rend(); rit++) {
670 ModelAction *prev = *rit;
671 if (prev->could_synchronize_with(act)) {
677 ModelAction *ret2 = get_last_fence_conflict(act);
687 case ATOMIC_TRYLOCK: {
688 /* linear search: from most recent to oldest */
689 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
690 action_list_t::reverse_iterator rit;
691 for (rit = list->rbegin(); rit != list->rend(); rit++) {
692 ModelAction *prev = *rit;
693 if (act->is_conflicting_lock(prev))
698 case ATOMIC_UNLOCK: {
699 /* linear search: from most recent to oldest */
700 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
701 action_list_t::reverse_iterator rit;
702 for (rit = list->rbegin(); rit != list->rend(); rit++) {
703 ModelAction *prev = *rit;
704 if (!act->same_thread(prev) && prev->is_failed_trylock())
710 /* linear search: from most recent to oldest */
711 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
712 action_list_t::reverse_iterator rit;
713 for (rit = list->rbegin(); rit != list->rend(); rit++) {
714 ModelAction *prev = *rit;
715 if (!act->same_thread(prev) && prev->is_failed_trylock())
717 if (!act->same_thread(prev) && prev->is_notify())
723 case ATOMIC_NOTIFY_ALL:
724 case ATOMIC_NOTIFY_ONE: {
725 /* linear search: from most recent to oldest */
726 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
727 action_list_t::reverse_iterator rit;
728 for (rit = list->rbegin(); rit != list->rend(); rit++) {
729 ModelAction *prev = *rit;
730 if (!act->same_thread(prev) && prev->is_wait())
741 /** This method finds backtracking points where we should try to
742 * reorder the parameter ModelAction against.
744 * @param the ModelAction to find backtracking points for.
746 void ModelChecker::set_backtracking(ModelAction *act)
748 Thread *t = get_thread(act);
749 ModelAction *prev = get_last_conflict(act);
753 Node *node = prev->get_node()->get_parent();
755 int low_tid, high_tid;
756 if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
757 low_tid = id_to_int(act->get_tid());
758 high_tid = low_tid + 1;
761 high_tid = get_num_threads();
764 for (int i = low_tid; i < high_tid; i++) {
765 thread_id_t tid = int_to_id(i);
767 /* Make sure this thread can be enabled here. */
768 if (i >= node->get_num_threads())
771 /* Don't backtrack into a point where the thread is disabled or sleeping. */
772 if (node->enabled_status(tid) != THREAD_ENABLED)
775 /* Check if this has been explored already */
776 if (node->has_been_explored(tid))
779 /* See if fairness allows */
780 if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
782 for (int t = 0; t < node->get_num_threads(); t++) {
783 thread_id_t tother = int_to_id(t);
784 if (node->is_enabled(tother) && node->has_priority(tother)) {
792 /* Cache the latest backtracking point */
793 set_latest_backtrack(prev);
795 /* If this is a new backtracking point, mark the tree */
796 if (!node->set_backtrack(tid))
798 DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
799 id_to_int(prev->get_tid()),
800 id_to_int(t->get_id()));
809 * @brief Cache the a backtracking point as the "most recent", if eligible
811 * Note that this does not prepare the NodeStack for this backtracking
812 * operation, it only caches the action on a per-execution basis
814 * @param act The operation at which we should explore a different next action
815 * (i.e., backtracking point)
816 * @return True, if this action is now the most recent backtracking point;
819 bool ModelChecker::set_latest_backtrack(ModelAction *act)
821 if (!priv->next_backtrack || *act > *priv->next_backtrack) {
822 priv->next_backtrack = act;
829 * Returns last backtracking point. The model checker will explore a different
830 * path for this point in the next execution.
831 * @return The ModelAction at which the next execution should diverge.
833 ModelAction * ModelChecker::get_next_backtrack()
835 ModelAction *next = priv->next_backtrack;
836 priv->next_backtrack = NULL;
841 * Processes a read model action.
842 * @param curr is the read model action to process.
843 * @return True if processing this read updates the mo_graph.
845 bool ModelChecker::process_read(ModelAction *curr)
847 Node *node = curr->get_node();
848 uint64_t value = VALUE_NONE;
849 bool updated = false;
851 switch (node->get_read_from_status()) {
852 case READ_FROM_PAST: {
853 const ModelAction *rf = node->get_read_from_past();
856 mo_graph->startChanges();
857 value = rf->get_value();
858 check_recency(curr, rf);
859 bool r_status = r_modification_order(curr, rf);
861 if (is_infeasible() && node->increment_read_from()) {
862 mo_graph->rollbackChanges();
863 priv->too_many_reads = false;
868 mo_graph->commitChanges();
869 mo_check_promises(curr, true);
874 case READ_FROM_PROMISE: {
875 Promise *promise = curr->get_node()->get_read_from_promise();
876 promise->add_reader(curr);
877 value = promise->get_value();
878 curr->set_read_from_promise(promise);
879 mo_graph->startChanges();
880 updated = r_modification_order(curr, promise);
881 mo_graph->commitChanges();
884 case READ_FROM_FUTURE: {
885 /* Read from future value */
886 struct future_value fv = node->get_future_value();
887 Promise *promise = new Promise(curr, fv);
889 curr->set_read_from_promise(promise);
890 promises->push_back(promise);
891 mo_graph->startChanges();
892 updated = r_modification_order(curr, promise);
893 mo_graph->commitChanges();
899 get_thread(curr)->set_return_value(value);
905 * Processes a lock, trylock, or unlock model action. @param curr is
906 * the read model action to process.
908 * The try lock operation checks whether the lock is taken. If not,
909 * it falls to the normal lock operation case. If so, it returns
912 * The lock operation has already been checked that it is enabled, so
913 * it just grabs the lock and synchronizes with the previous unlock.
915 * The unlock operation has to re-enable all of the threads that are
916 * waiting on the lock.
918 * @return True if synchronization was updated; false otherwise
920 bool ModelChecker::process_mutex(ModelAction *curr)
922 std::mutex *mutex = NULL;
923 struct std::mutex_state *state = NULL;
925 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
926 mutex = (std::mutex *)curr->get_location();
927 state = mutex->get_state();
928 } else if (curr->is_wait()) {
929 mutex = (std::mutex *)curr->get_value();
930 state = mutex->get_state();
933 switch (curr->get_type()) {
934 case ATOMIC_TRYLOCK: {
935 bool success = !state->islocked;
936 curr->set_try_lock(success);
938 get_thread(curr)->set_return_value(0);
941 get_thread(curr)->set_return_value(1);
943 //otherwise fall into the lock case
945 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
946 assert_bug("Lock access before initialization");
947 state->islocked = true;
948 ModelAction *unlock = get_last_unlock(curr);
949 //synchronize with the previous unlock statement
950 if (unlock != NULL) {
951 curr->synchronize_with(unlock);
956 case ATOMIC_UNLOCK: {
958 state->islocked = false;
959 //wake up the other threads
960 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
961 //activate all the waiting threads
962 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
963 scheduler->wake(get_thread(*rit));
970 state->islocked = false;
971 //wake up the other threads
972 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
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));
978 //check whether we should go to sleep or not...simulate spurious failures
979 if (curr->get_node()->get_misc() == 0) {
980 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
982 scheduler->sleep(get_thread(curr));
986 case ATOMIC_NOTIFY_ALL: {
987 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
988 //activate all the waiting threads
989 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
990 scheduler->wake(get_thread(*rit));
995 case ATOMIC_NOTIFY_ONE: {
996 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
997 int wakeupthread = curr->get_node()->get_misc();
998 action_list_t::iterator it = waiters->begin();
999 advance(it, wakeupthread);
1000 scheduler->wake(get_thread(*it));
1011 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
1013 /* Do more ambitious checks now that mo is more complete */
1014 if (mo_may_allow(writer, reader)) {
1015 Node *node = reader->get_node();
1017 /* Find an ancestor thread which exists at the time of the reader */
1018 Thread *write_thread = get_thread(writer);
1019 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
1020 write_thread = write_thread->get_parent();
1022 struct future_value fv = {
1023 writer->get_value(),
1024 writer->get_seq_number() + params.maxfuturedelay,
1025 write_thread->get_id(),
1027 if (node->add_future_value(fv))
1028 set_latest_backtrack(reader);
1033 * Process a write ModelAction
1034 * @param curr The ModelAction to process
1035 * @return True if the mo_graph was updated or promises were resolved
1037 bool ModelChecker::process_write(ModelAction *curr)
1039 bool updated_mod_order = w_modification_order(curr);
1040 bool updated_promises = resolve_promises(curr);
1042 if (promises->size() == 0) {
1043 for (unsigned int i = 0; i < futurevalues->size(); i++) {
1044 struct PendingFutureValue pfv = (*futurevalues)[i];
1045 add_future_value(pfv.writer, pfv.act);
1047 futurevalues->clear();
1050 mo_graph->commitChanges();
1051 mo_check_promises(curr, false);
1053 get_thread(curr)->set_return_value(VALUE_NONE);
1054 return updated_mod_order || updated_promises;
1058 * Process a fence ModelAction
1059 * @param curr The ModelAction to process
1060 * @return True if synchronization was updated
1062 bool ModelChecker::process_fence(ModelAction *curr)
1065 * fence-relaxed: no-op
1066 * fence-release: only log the occurence (not in this function), for
1067 * use in later synchronization
1068 * fence-acquire (this function): search for hypothetical release
1071 bool updated = false;
1072 if (curr->is_acquire()) {
1073 action_list_t *list = action_trace;
1074 action_list_t::reverse_iterator rit;
1075 /* Find X : is_read(X) && X --sb-> curr */
1076 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1077 ModelAction *act = *rit;
1080 if (act->get_tid() != curr->get_tid())
1082 /* Stop at the beginning of the thread */
1083 if (act->is_thread_start())
1085 /* Stop once we reach a prior fence-acquire */
1086 if (act->is_fence() && act->is_acquire())
1088 if (!act->is_read())
1090 /* read-acquire will find its own release sequences */
1091 if (act->is_acquire())
1094 /* Establish hypothetical release sequences */
1095 rel_heads_list_t release_heads;
1096 get_release_seq_heads(curr, act, &release_heads);
1097 for (unsigned int i = 0; i < release_heads.size(); i++)
1098 if (!curr->synchronize_with(release_heads[i]))
1099 set_bad_synchronization();
1100 if (release_heads.size() != 0)
1108 * @brief Process the current action for thread-related activity
1110 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1111 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1112 * synchronization, etc. This function is a no-op for non-THREAD actions
1113 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1115 * @param curr The current action
1116 * @return True if synchronization was updated or a thread completed
1118 bool ModelChecker::process_thread_action(ModelAction *curr)
1120 bool updated = false;
1122 switch (curr->get_type()) {
1123 case THREAD_CREATE: {
1124 thrd_t *thrd = (thrd_t *)curr->get_location();
1125 struct thread_params *params = (struct thread_params *)curr->get_value();
1126 Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
1128 th->set_creation(curr);
1129 /* Promises can be satisfied by children */
1130 for (unsigned int i = 0; i < promises->size(); i++) {
1131 Promise *promise = (*promises)[i];
1132 if (promise->thread_is_available(curr->get_tid()))
1133 promise->add_thread(th->get_id());
1138 Thread *blocking = curr->get_thread_operand();
1139 ModelAction *act = get_last_action(blocking->get_id());
1140 curr->synchronize_with(act);
1141 updated = true; /* trigger rel-seq checks */
1144 case THREAD_FINISH: {
1145 Thread *th = get_thread(curr);
1146 while (!th->wait_list_empty()) {
1147 ModelAction *act = th->pop_wait_list();
1148 scheduler->wake(get_thread(act));
1151 /* Completed thread can't satisfy promises */
1152 for (unsigned int i = 0; i < promises->size(); i++) {
1153 Promise *promise = (*promises)[i];
1154 if (promise->thread_is_available(th->get_id()))
1155 if (promise->eliminate_thread(th->get_id()))
1156 priv->failed_promise = true;
1158 updated = true; /* trigger rel-seq checks */
1161 case THREAD_START: {
1162 check_promises(curr->get_tid(), NULL, curr->get_cv());
1173 * @brief Process the current action for release sequence fixup activity
1175 * Performs model-checker release sequence fixups for the current action,
1176 * forcing a single pending release sequence to break (with a given, potential
1177 * "loose" write) or to complete (i.e., synchronize). If a pending release
1178 * sequence forms a complete release sequence, then we must perform the fixup
1179 * synchronization, mo_graph additions, etc.
1181 * @param curr The current action; must be a release sequence fixup action
1182 * @param work_queue The work queue to which to add work items as they are
1185 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1187 const ModelAction *write = curr->get_node()->get_relseq_break();
1188 struct release_seq *sequence = pending_rel_seqs->back();
1189 pending_rel_seqs->pop_back();
1191 ModelAction *acquire = sequence->acquire;
1192 const ModelAction *rf = sequence->rf;
1193 const ModelAction *release = sequence->release;
1197 ASSERT(release->same_thread(rf));
1199 if (write == NULL) {
1201 * @todo Forcing a synchronization requires that we set
1202 * modification order constraints. For instance, we can't allow
1203 * a fixup sequence in which two separate read-acquire
1204 * operations read from the same sequence, where the first one
1205 * synchronizes and the other doesn't. Essentially, we can't
1206 * allow any writes to insert themselves between 'release' and
1210 /* Must synchronize */
1211 if (!acquire->synchronize_with(release)) {
1212 set_bad_synchronization();
1215 /* Re-check all pending release sequences */
1216 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1217 /* Re-check act for mo_graph edges */
1218 work_queue->push_back(MOEdgeWorkEntry(acquire));
1220 /* propagate synchronization to later actions */
1221 action_list_t::reverse_iterator rit = action_trace->rbegin();
1222 for (; (*rit) != acquire; rit++) {
1223 ModelAction *propagate = *rit;
1224 if (acquire->happens_before(propagate)) {
1225 propagate->synchronize_with(acquire);
1226 /* Re-check 'propagate' for mo_graph edges */
1227 work_queue->push_back(MOEdgeWorkEntry(propagate));
1231 /* Break release sequence with new edges:
1232 * release --mo--> write --mo--> rf */
1233 mo_graph->addEdge(release, write);
1234 mo_graph->addEdge(write, rf);
1237 /* See if we have realized a data race */
1242 * Initialize the current action by performing one or more of the following
1243 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1244 * in the NodeStack, manipulating backtracking sets, allocating and
1245 * initializing clock vectors, and computing the promises to fulfill.
1247 * @param curr The current action, as passed from the user context; may be
1248 * freed/invalidated after the execution of this function, with a different
1249 * action "returned" its place (pass-by-reference)
1250 * @return True if curr is a newly-explored action; false otherwise
1252 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1254 ModelAction *newcurr;
1256 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1257 newcurr = process_rmw(*curr);
1260 if (newcurr->is_rmw())
1261 compute_promises(newcurr);
1267 (*curr)->set_seq_number(get_next_seq_num());
1269 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1271 /* First restore type and order in case of RMW operation */
1272 if ((*curr)->is_rmwr())
1273 newcurr->copy_typeandorder(*curr);
1275 ASSERT((*curr)->get_location() == newcurr->get_location());
1276 newcurr->copy_from_new(*curr);
1278 /* Discard duplicate ModelAction; use action from NodeStack */
1281 /* Always compute new clock vector */
1282 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1285 return false; /* Action was explored previously */
1289 /* Always compute new clock vector */
1290 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1292 /* Assign most recent release fence */
1293 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1296 * Perform one-time actions when pushing new ModelAction onto
1299 if (newcurr->is_write())
1300 compute_promises(newcurr);
1301 else if (newcurr->is_relseq_fixup())
1302 compute_relseq_breakwrites(newcurr);
1303 else if (newcurr->is_wait())
1304 newcurr->get_node()->set_misc_max(2);
1305 else if (newcurr->is_notify_one()) {
1306 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1308 return true; /* This was a new ModelAction */
1313 * @brief Establish reads-from relation between two actions
1315 * Perform basic operations involved with establishing a concrete rf relation,
1316 * including setting the ModelAction data and checking for release sequences.
1318 * @param act The action that is reading (must be a read)
1319 * @param rf The action from which we are reading (must be a write)
1321 * @return True if this read established synchronization
1323 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1325 act->set_read_from(rf);
1326 if (rf != NULL && act->is_acquire()) {
1327 rel_heads_list_t release_heads;
1328 get_release_seq_heads(act, act, &release_heads);
1329 int num_heads = release_heads.size();
1330 for (unsigned int i = 0; i < release_heads.size(); i++)
1331 if (!act->synchronize_with(release_heads[i])) {
1332 set_bad_synchronization();
1335 return num_heads > 0;
1341 * Check promises and eliminate potentially-satisfying threads when a thread is
1342 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1343 * no longer satisfy a promise generated from that thread.
1345 * @param blocker The thread on which a thread is waiting
1346 * @param waiting The waiting thread
1348 void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1350 for (unsigned int i = 0; i < promises->size(); i++) {
1351 Promise *promise = (*promises)[i];
1352 if (!promise->thread_is_available(waiting->get_id()))
1354 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1355 ModelAction *reader = promise->get_reader(j);
1356 if (reader->get_tid() != blocker->get_id())
1358 if (promise->eliminate_thread(waiting->get_id())) {
1359 /* Promise has failed */
1360 priv->failed_promise = true;
1362 /* Only eliminate the 'waiting' thread once */
1370 * @brief Check whether a model action is enabled.
1372 * Checks whether a lock or join operation would be successful (i.e., is the
1373 * lock already locked, or is the joined thread already complete). If not, put
1374 * the action in a waiter list.
1376 * @param curr is the ModelAction to check whether it is enabled.
1377 * @return a bool that indicates whether the action is enabled.
1379 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1380 if (curr->is_lock()) {
1381 std::mutex *lock = (std::mutex *)curr->get_location();
1382 struct std::mutex_state *state = lock->get_state();
1383 if (state->islocked) {
1384 //Stick the action in the appropriate waiting queue
1385 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1388 } else if (curr->get_type() == THREAD_JOIN) {
1389 Thread *blocking = (Thread *)curr->get_location();
1390 if (!blocking->is_complete()) {
1391 blocking->push_wait_list(curr);
1392 thread_blocking_check_promises(blocking, get_thread(curr));
1401 * This is the heart of the model checker routine. It performs model-checking
1402 * actions corresponding to a given "current action." Among other processes, it
1403 * calculates reads-from relationships, updates synchronization clock vectors,
1404 * forms a memory_order constraints graph, and handles replay/backtrack
1405 * execution when running permutations of previously-observed executions.
1407 * @param curr The current action to process
1408 * @return The ModelAction that is actually executed; may be different than
1409 * curr; may be NULL, if the current action is not enabled to run
1411 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1414 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1416 if (!check_action_enabled(curr)) {
1417 /* Make the execution look like we chose to run this action
1418 * much later, when a lock/join can succeed */
1419 get_thread(curr)->set_pending(curr);
1420 scheduler->sleep(get_thread(curr));
1424 bool newly_explored = initialize_curr_action(&curr);
1430 wake_up_sleeping_actions(curr);
1432 /* Add the action to lists before any other model-checking tasks */
1433 if (!second_part_of_rmw)
1434 add_action_to_lists(curr);
1436 /* Build may_read_from set for newly-created actions */
1437 if (newly_explored && curr->is_read())
1438 build_may_read_from(curr);
1440 /* Initialize work_queue with the "current action" work */
1441 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1442 while (!work_queue.empty() && !has_asserted()) {
1443 WorkQueueEntry work = work_queue.front();
1444 work_queue.pop_front();
1446 switch (work.type) {
1447 case WORK_CHECK_CURR_ACTION: {
1448 ModelAction *act = work.action;
1449 bool update = false; /* update this location's release seq's */
1450 bool update_all = false; /* update all release seq's */
1452 if (process_thread_action(curr))
1455 if (act->is_read() && !second_part_of_rmw && process_read(act))
1458 if (act->is_write() && process_write(act))
1461 if (act->is_fence() && process_fence(act))
1464 if (act->is_mutex_op() && process_mutex(act))
1467 if (act->is_relseq_fixup())
1468 process_relseq_fixup(curr, &work_queue);
1471 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1473 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1476 case WORK_CHECK_RELEASE_SEQ:
1477 resolve_release_sequences(work.location, &work_queue);
1479 case WORK_CHECK_MO_EDGES: {
1480 /** @todo Complete verification of work_queue */
1481 ModelAction *act = work.action;
1482 bool updated = false;
1484 if (act->is_read()) {
1485 const ModelAction *rf = act->get_reads_from();
1486 const Promise *promise = act->get_reads_from_promise();
1488 if (r_modification_order(act, rf))
1490 } else if (promise) {
1491 if (r_modification_order(act, promise))
1495 if (act->is_write()) {
1496 if (w_modification_order(act))
1499 mo_graph->commitChanges();
1502 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1511 check_curr_backtracking(curr);
1512 set_backtracking(curr);
1516 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1518 Node *currnode = curr->get_node();
1519 Node *parnode = currnode->get_parent();
1521 if ((parnode && !parnode->backtrack_empty()) ||
1522 !currnode->misc_empty() ||
1523 !currnode->read_from_empty() ||
1524 !currnode->promise_empty() ||
1525 !currnode->relseq_break_empty()) {
1526 set_latest_backtrack(curr);
1530 bool ModelChecker::promises_expired() const
1532 for (unsigned int i = 0; i < promises->size(); i++) {
1533 Promise *promise = (*promises)[i];
1534 if (promise->get_expiration() < priv->used_sequence_numbers)
1541 * This is the strongest feasibility check available.
1542 * @return whether the current trace (partial or complete) must be a prefix of
1545 bool ModelChecker::isfeasibleprefix() const
1547 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1551 * Print disagnostic information about an infeasible execution
1552 * @param prefix A string to prefix the output with; if NULL, then a default
1553 * message prefix will be provided
1555 void ModelChecker::print_infeasibility(const char *prefix) const
1559 if (mo_graph->checkForCycles())
1560 ptr += sprintf(ptr, "[mo cycle]");
1561 if (priv->failed_promise)
1562 ptr += sprintf(ptr, "[failed promise]");
1563 if (priv->too_many_reads)
1564 ptr += sprintf(ptr, "[too many reads]");
1565 if (priv->no_valid_reads)
1566 ptr += sprintf(ptr, "[no valid reads-from]");
1567 if (priv->bad_synchronization)
1568 ptr += sprintf(ptr, "[bad sw ordering]");
1569 if (promises_expired())
1570 ptr += sprintf(ptr, "[promise expired]");
1571 if (promises->size() != 0)
1572 ptr += sprintf(ptr, "[unresolved promise]");
1574 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1578 * Returns whether the current completed trace is feasible, except for pending
1579 * release sequences.
1581 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1583 return !is_infeasible() && promises->size() == 0;
1587 * Check if the current partial trace is infeasible. Does not check any
1588 * end-of-execution flags, which might rule out the execution. Thus, this is
1589 * useful only for ruling an execution as infeasible.
1590 * @return whether the current partial trace is infeasible.
1592 bool ModelChecker::is_infeasible() const
1594 return mo_graph->checkForCycles() ||
1595 priv->no_valid_reads ||
1596 priv->failed_promise ||
1597 priv->too_many_reads ||
1598 priv->bad_synchronization ||
1602 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1603 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1604 ModelAction *lastread = get_last_action(act->get_tid());
1605 lastread->process_rmw(act);
1606 if (act->is_rmw()) {
1607 if (lastread->get_reads_from())
1608 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1610 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1611 mo_graph->commitChanges();
1617 * Checks whether a thread has read from the same write for too many times
1618 * without seeing the effects of a later write.
1621 * 1) there must a different write that we could read from that would satisfy the modification order,
1622 * 2) we must have read from the same value in excess of maxreads times, and
1623 * 3) that other write must have been in the reads_from set for maxreads times.
1625 * If so, we decide that the execution is no longer feasible.
1627 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1629 if (params.maxreads != 0) {
1630 if (curr->get_node()->get_read_from_past_size() <= 1)
1632 //Must make sure that execution is currently feasible... We could
1633 //accidentally clear by rolling back
1634 if (is_infeasible())
1636 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1637 int tid = id_to_int(curr->get_tid());
1640 if ((int)thrd_lists->size() <= tid)
1642 action_list_t *list = &(*thrd_lists)[tid];
1644 action_list_t::reverse_iterator rit = list->rbegin();
1645 /* Skip past curr */
1646 for (; (*rit) != curr; rit++)
1648 /* go past curr now */
1651 action_list_t::reverse_iterator ritcopy = rit;
1652 //See if we have enough reads from the same value
1654 for (; count < params.maxreads; rit++, count++) {
1655 if (rit == list->rend())
1657 ModelAction *act = *rit;
1658 if (!act->is_read())
1661 if (act->get_reads_from() != rf)
1663 if (act->get_node()->get_read_from_past_size() <= 1)
1666 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1668 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1670 /* Need a different write */
1674 /* Test to see whether this is a feasible write to read from */
1675 /** NOTE: all members of read-from set should be
1676 * feasible, so we no longer check it here **/
1680 bool feasiblewrite = true;
1681 //new we need to see if this write works for everyone
1683 for (int loop = count; loop > 0; loop--, rit++) {
1684 ModelAction *act = *rit;
1685 bool foundvalue = false;
1686 for (int j = 0; j < act->get_node()->get_read_from_past_size(); j++) {
1687 if (act->get_node()->get_read_from_past(j) == write) {
1693 feasiblewrite = false;
1697 if (feasiblewrite) {
1698 priv->too_many_reads = true;
1706 * Updates the mo_graph with the constraints imposed from the current
1709 * Basic idea is the following: Go through each other thread and find
1710 * the last action that happened before our read. Two cases:
1712 * (1) The action is a write => that write must either occur before
1713 * the write we read from or be the write we read from.
1715 * (2) The action is a read => the write that that action read from
1716 * must occur before the write we read from or be the same write.
1718 * @param curr The current action. Must be a read.
1719 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1720 * @return True if modification order edges were added; false otherwise
1722 template <typename rf_type>
1723 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1725 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1728 ASSERT(curr->is_read());
1730 /* Last SC fence in the current thread */
1731 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1733 /* Iterate over all threads */
1734 for (i = 0; i < thrd_lists->size(); i++) {
1735 /* Last SC fence in thread i */
1736 ModelAction *last_sc_fence_thread_local = NULL;
1737 if (int_to_id((int)i) != curr->get_tid())
1738 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1740 /* Last SC fence in thread i, before last SC fence in current thread */
1741 ModelAction *last_sc_fence_thread_before = NULL;
1742 if (last_sc_fence_local)
1743 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1745 /* Iterate over actions in thread, starting from most recent */
1746 action_list_t *list = &(*thrd_lists)[i];
1747 action_list_t::reverse_iterator rit;
1748 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1749 ModelAction *act = *rit;
1751 if (act->is_write() && !act->equals(rf) && act != curr) {
1752 /* C++, Section 29.3 statement 5 */
1753 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1754 *act < *last_sc_fence_thread_local) {
1755 added = mo_graph->addEdge(act, rf) || added;
1758 /* C++, Section 29.3 statement 4 */
1759 else if (act->is_seqcst() && last_sc_fence_local &&
1760 *act < *last_sc_fence_local) {
1761 added = mo_graph->addEdge(act, rf) || added;
1764 /* C++, Section 29.3 statement 6 */
1765 else if (last_sc_fence_thread_before &&
1766 *act < *last_sc_fence_thread_before) {
1767 added = mo_graph->addEdge(act, rf) || added;
1773 * Include at most one act per-thread that "happens
1774 * before" curr. Don't consider reflexively.
1776 if (act->happens_before(curr) && act != curr) {
1777 if (act->is_write()) {
1778 if (!act->equals(rf)) {
1779 added = mo_graph->addEdge(act, rf) || added;
1782 const ModelAction *prevrf = act->get_reads_from();
1783 const Promise *prevrf_promise = act->get_reads_from_promise();
1785 if (!prevrf->equals(rf))
1786 added = mo_graph->addEdge(prevrf, rf) || added;
1787 } else if (!prevrf_promise->equals(rf)) {
1788 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1797 * All compatible, thread-exclusive promises must be ordered after any
1798 * concrete loads from the same thread
1800 for (unsigned int i = 0; i < promises->size(); i++)
1801 if ((*promises)[i]->is_compatible_exclusive(curr))
1802 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1808 * Updates the mo_graph with the constraints imposed from the current write.
1810 * Basic idea is the following: Go through each other thread and find
1811 * the lastest action that happened before our write. Two cases:
1813 * (1) The action is a write => that write must occur before
1816 * (2) The action is a read => the write that that action read from
1817 * must occur before the current write.
1819 * This method also handles two other issues:
1821 * (I) Sequential Consistency: Making sure that if the current write is
1822 * seq_cst, that it occurs after the previous seq_cst write.
1824 * (II) Sending the write back to non-synchronizing reads.
1826 * @param curr The current action. Must be a write.
1827 * @return True if modification order edges were added; false otherwise
1829 bool ModelChecker::w_modification_order(ModelAction *curr)
1831 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1834 ASSERT(curr->is_write());
1836 if (curr->is_seqcst()) {
1837 /* We have to at least see the last sequentially consistent write,
1838 so we are initialized. */
1839 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1840 if (last_seq_cst != NULL) {
1841 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1845 /* Last SC fence in the current thread */
1846 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1848 /* Iterate over all threads */
1849 for (i = 0; i < thrd_lists->size(); i++) {
1850 /* Last SC fence in thread i, before last SC fence in current thread */
1851 ModelAction *last_sc_fence_thread_before = NULL;
1852 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1853 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1855 /* Iterate over actions in thread, starting from most recent */
1856 action_list_t *list = &(*thrd_lists)[i];
1857 action_list_t::reverse_iterator rit;
1858 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1859 ModelAction *act = *rit;
1862 * 1) If RMW and it actually read from something, then we
1863 * already have all relevant edges, so just skip to next
1866 * 2) If RMW and it didn't read from anything, we should
1867 * whatever edge we can get to speed up convergence.
1869 * 3) If normal write, we need to look at earlier actions, so
1870 * continue processing list.
1872 if (curr->is_rmw()) {
1873 if (curr->get_reads_from() != NULL)
1881 /* C++, Section 29.3 statement 7 */
1882 if (last_sc_fence_thread_before && act->is_write() &&
1883 *act < *last_sc_fence_thread_before) {
1884 added = mo_graph->addEdge(act, curr) || added;
1889 * Include at most one act per-thread that "happens
1892 if (act->happens_before(curr)) {
1894 * Note: if act is RMW, just add edge:
1896 * The following edge should be handled elsewhere:
1897 * readfrom(act) --mo--> act
1899 if (act->is_write())
1900 added = mo_graph->addEdge(act, curr) || added;
1901 else if (act->is_read()) {
1902 //if previous read accessed a null, just keep going
1903 if (act->get_reads_from() == NULL)
1905 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1908 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1909 !act->same_thread(curr)) {
1910 /* We have an action that:
1911 (1) did not happen before us
1912 (2) is a read and we are a write
1913 (3) cannot synchronize with us
1914 (4) is in a different thread
1916 that read could potentially read from our write. Note that
1917 these checks are overly conservative at this point, we'll
1918 do more checks before actually removing the
1922 if (thin_air_constraint_may_allow(curr, act)) {
1923 if (!is_infeasible())
1924 futurevalues->push_back(PendingFutureValue(curr, act));
1925 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1926 add_future_value(curr, act);
1933 * All compatible, thread-exclusive promises must be ordered after any
1934 * concrete stores to the same thread, or else they can be merged with
1937 for (unsigned int i = 0; i < promises->size(); i++)
1938 if ((*promises)[i]->is_compatible_exclusive(curr))
1939 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1944 /** Arbitrary reads from the future are not allowed. Section 29.3
1945 * part 9 places some constraints. This method checks one result of constraint
1946 * constraint. Others require compiler support. */
1947 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1949 if (!writer->is_rmw())
1952 if (!reader->is_rmw())
1955 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1956 if (search == reader)
1958 if (search->get_tid() == reader->get_tid() &&
1959 search->happens_before(reader))
1967 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1968 * some constraints. This method checks one the following constraint (others
1969 * require compiler support):
1971 * If X --hb-> Y --mo-> Z, then X should not read from Z.
1973 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
1975 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
1977 /* Iterate over all threads */
1978 for (i = 0; i < thrd_lists->size(); i++) {
1979 const ModelAction *write_after_read = NULL;
1981 /* Iterate over actions in thread, starting from most recent */
1982 action_list_t *list = &(*thrd_lists)[i];
1983 action_list_t::reverse_iterator rit;
1984 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1985 ModelAction *act = *rit;
1987 /* Don't disallow due to act == reader */
1988 if (!reader->happens_before(act) || reader == act)
1990 else if (act->is_write())
1991 write_after_read = act;
1992 else if (act->is_read() && act->get_reads_from() != NULL)
1993 write_after_read = act->get_reads_from();
1996 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
2003 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
2004 * The ModelAction under consideration is expected to be taking part in
2005 * release/acquire synchronization as an object of the "reads from" relation.
2006 * Note that this can only provide release sequence support for RMW chains
2007 * which do not read from the future, as those actions cannot be traced until
2008 * their "promise" is fulfilled. Similarly, we may not even establish the
2009 * presence of a release sequence with certainty, as some modification order
2010 * constraints may be decided further in the future. Thus, this function
2011 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
2012 * and a boolean representing certainty.
2014 * @param rf The action that might be part of a release sequence. Must be a
2016 * @param release_heads A pass-by-reference style return parameter. After
2017 * execution of this function, release_heads will contain the heads of all the
2018 * relevant release sequences, if any exists with certainty
2019 * @param pending A pass-by-reference style return parameter which is only used
2020 * when returning false (i.e., uncertain). Returns most information regarding
2021 * an uncertain release sequence, including any write operations that might
2022 * break the sequence.
2023 * @return true, if the ModelChecker is certain that release_heads is complete;
2026 bool ModelChecker::release_seq_heads(const ModelAction *rf,
2027 rel_heads_list_t *release_heads,
2028 struct release_seq *pending) const
2030 /* Only check for release sequences if there are no cycles */
2031 if (mo_graph->checkForCycles())
2034 for ( ; rf != NULL; rf = rf->get_reads_from()) {
2035 ASSERT(rf->is_write());
2037 if (rf->is_release())
2038 release_heads->push_back(rf);
2039 else if (rf->get_last_fence_release())
2040 release_heads->push_back(rf->get_last_fence_release());
2042 break; /* End of RMW chain */
2044 /** @todo Need to be smarter here... In the linux lock
2045 * example, this will run to the beginning of the program for
2047 /** @todo The way to be smarter here is to keep going until 1
2048 * thread has a release preceded by an acquire and you've seen
2051 /* acq_rel RMW is a sufficient stopping condition */
2052 if (rf->is_acquire() && rf->is_release())
2053 return true; /* complete */
2056 /* read from future: need to settle this later */
2058 return false; /* incomplete */
2061 if (rf->is_release())
2062 return true; /* complete */
2064 /* else relaxed write
2065 * - check for fence-release in the same thread (29.8, stmt. 3)
2066 * - check modification order for contiguous subsequence
2067 * -> rf must be same thread as release */
2069 const ModelAction *fence_release = rf->get_last_fence_release();
2070 /* Synchronize with a fence-release unconditionally; we don't need to
2071 * find any more "contiguous subsequence..." for it */
2073 release_heads->push_back(fence_release);
2075 int tid = id_to_int(rf->get_tid());
2076 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
2077 action_list_t *list = &(*thrd_lists)[tid];
2078 action_list_t::const_reverse_iterator rit;
2080 /* Find rf in the thread list */
2081 rit = std::find(list->rbegin(), list->rend(), rf);
2082 ASSERT(rit != list->rend());
2084 /* Find the last {write,fence}-release */
2085 for (; rit != list->rend(); rit++) {
2086 if (fence_release && *(*rit) < *fence_release)
2088 if ((*rit)->is_release())
2091 if (rit == list->rend()) {
2092 /* No write-release in this thread */
2093 return true; /* complete */
2094 } else if (fence_release && *(*rit) < *fence_release) {
2095 /* The fence-release is more recent (and so, "stronger") than
2096 * the most recent write-release */
2097 return true; /* complete */
2098 } /* else, need to establish contiguous release sequence */
2099 ModelAction *release = *rit;
2101 ASSERT(rf->same_thread(release));
2103 pending->writes.clear();
2105 bool certain = true;
2106 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2107 if (id_to_int(rf->get_tid()) == (int)i)
2109 list = &(*thrd_lists)[i];
2111 /* Can we ensure no future writes from this thread may break
2112 * the release seq? */
2113 bool future_ordered = false;
2115 ModelAction *last = get_last_action(int_to_id(i));
2116 Thread *th = get_thread(int_to_id(i));
2117 if ((last && rf->happens_before(last)) ||
2120 future_ordered = true;
2122 ASSERT(!th->is_model_thread() || future_ordered);
2124 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2125 const ModelAction *act = *rit;
2126 /* Reach synchronization -> this thread is complete */
2127 if (act->happens_before(release))
2129 if (rf->happens_before(act)) {
2130 future_ordered = true;
2134 /* Only non-RMW writes can break release sequences */
2135 if (!act->is_write() || act->is_rmw())
2138 /* Check modification order */
2139 if (mo_graph->checkReachable(rf, act)) {
2140 /* rf --mo--> act */
2141 future_ordered = true;
2144 if (mo_graph->checkReachable(act, release))
2145 /* act --mo--> release */
2147 if (mo_graph->checkReachable(release, act) &&
2148 mo_graph->checkReachable(act, rf)) {
2149 /* release --mo-> act --mo--> rf */
2150 return true; /* complete */
2152 /* act may break release sequence */
2153 pending->writes.push_back(act);
2156 if (!future_ordered)
2157 certain = false; /* This thread is uncertain */
2161 release_heads->push_back(release);
2162 pending->writes.clear();
2164 pending->release = release;
2171 * An interface for getting the release sequence head(s) with which a
2172 * given ModelAction must synchronize. This function only returns a non-empty
2173 * result when it can locate a release sequence head with certainty. Otherwise,
2174 * it may mark the internal state of the ModelChecker so that it will handle
2175 * the release sequence at a later time, causing @a acquire to update its
2176 * synchronization at some later point in execution.
2178 * @param acquire The 'acquire' action that may synchronize with a release
2180 * @param read The read action that may read from a release sequence; this may
2181 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2182 * when 'acquire' is a fence-acquire)
2183 * @param release_heads A pass-by-reference return parameter. Will be filled
2184 * with the head(s) of the release sequence(s), if they exists with certainty.
2185 * @see ModelChecker::release_seq_heads
2187 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2188 ModelAction *read, rel_heads_list_t *release_heads)
2190 const ModelAction *rf = read->get_reads_from();
2191 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2192 sequence->acquire = acquire;
2193 sequence->read = read;
2195 if (!release_seq_heads(rf, release_heads, sequence)) {
2196 /* add act to 'lazy checking' list */
2197 pending_rel_seqs->push_back(sequence);
2199 snapshot_free(sequence);
2204 * Attempt to resolve all stashed operations that might synchronize with a
2205 * release sequence for a given location. This implements the "lazy" portion of
2206 * determining whether or not a release sequence was contiguous, since not all
2207 * modification order information is present at the time an action occurs.
2209 * @param location The location/object that should be checked for release
2210 * sequence resolutions. A NULL value means to check all locations.
2211 * @param work_queue The work queue to which to add work items as they are
2213 * @return True if any updates occurred (new synchronization, new mo_graph
2216 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2218 bool updated = false;
2219 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2220 while (it != pending_rel_seqs->end()) {
2221 struct release_seq *pending = *it;
2222 ModelAction *acquire = pending->acquire;
2223 const ModelAction *read = pending->read;
2225 /* Only resolve sequences on the given location, if provided */
2226 if (location && read->get_location() != location) {
2231 const ModelAction *rf = read->get_reads_from();
2232 rel_heads_list_t release_heads;
2234 complete = release_seq_heads(rf, &release_heads, pending);
2235 for (unsigned int i = 0; i < release_heads.size(); i++) {
2236 if (!acquire->has_synchronized_with(release_heads[i])) {
2237 if (acquire->synchronize_with(release_heads[i]))
2240 set_bad_synchronization();
2245 /* Re-check all pending release sequences */
2246 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2247 /* Re-check read-acquire for mo_graph edges */
2248 if (acquire->is_read())
2249 work_queue->push_back(MOEdgeWorkEntry(acquire));
2251 /* propagate synchronization to later actions */
2252 action_list_t::reverse_iterator rit = action_trace->rbegin();
2253 for (; (*rit) != acquire; rit++) {
2254 ModelAction *propagate = *rit;
2255 if (acquire->happens_before(propagate)) {
2256 propagate->synchronize_with(acquire);
2257 /* Re-check 'propagate' for mo_graph edges */
2258 work_queue->push_back(MOEdgeWorkEntry(propagate));
2263 it = pending_rel_seqs->erase(it);
2264 snapshot_free(pending);
2270 // If we resolved promises or data races, see if we have realized a data race.
2277 * Performs various bookkeeping operations for the current ModelAction. For
2278 * instance, adds action to the per-object, per-thread action vector and to the
2279 * action trace list of all thread actions.
2281 * @param act is the ModelAction to add.
2283 void ModelChecker::add_action_to_lists(ModelAction *act)
2285 int tid = id_to_int(act->get_tid());
2286 ModelAction *uninit = NULL;
2288 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2289 if (list->empty() && act->is_atomic_var()) {
2290 uninit = new_uninitialized_action(act->get_location());
2291 uninit_id = id_to_int(uninit->get_tid());
2292 list->push_back(uninit);
2294 list->push_back(act);
2296 action_trace->push_back(act);
2298 action_trace->push_front(uninit);
2300 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2301 if (tid >= (int)vec->size())
2302 vec->resize(priv->next_thread_id);
2303 (*vec)[tid].push_back(act);
2305 (*vec)[uninit_id].push_front(uninit);
2307 if ((int)thrd_last_action->size() <= tid)
2308 thrd_last_action->resize(get_num_threads());
2309 (*thrd_last_action)[tid] = act;
2311 (*thrd_last_action)[uninit_id] = uninit;
2313 if (act->is_fence() && act->is_release()) {
2314 if ((int)thrd_last_fence_release->size() <= tid)
2315 thrd_last_fence_release->resize(get_num_threads());
2316 (*thrd_last_fence_release)[tid] = act;
2319 if (act->is_wait()) {
2320 void *mutex_loc = (void *) act->get_value();
2321 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2323 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2324 if (tid >= (int)vec->size())
2325 vec->resize(priv->next_thread_id);
2326 (*vec)[tid].push_back(act);
2331 * @brief Get the last action performed by a particular Thread
2332 * @param tid The thread ID of the Thread in question
2333 * @return The last action in the thread
2335 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2337 int threadid = id_to_int(tid);
2338 if (threadid < (int)thrd_last_action->size())
2339 return (*thrd_last_action)[id_to_int(tid)];
2345 * @brief Get the last fence release performed by a particular Thread
2346 * @param tid The thread ID of the Thread in question
2347 * @return The last fence release in the thread, if one exists; NULL otherwise
2349 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2351 int threadid = id_to_int(tid);
2352 if (threadid < (int)thrd_last_fence_release->size())
2353 return (*thrd_last_fence_release)[id_to_int(tid)];
2359 * Gets the last memory_order_seq_cst write (in the total global sequence)
2360 * performed on a particular object (i.e., memory location), not including the
2362 * @param curr The current ModelAction; also denotes the object location to
2364 * @return The last seq_cst write
2366 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2368 void *location = curr->get_location();
2369 action_list_t *list = get_safe_ptr_action(obj_map, location);
2370 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2371 action_list_t::reverse_iterator rit;
2372 for (rit = list->rbegin(); rit != list->rend(); rit++)
2373 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2379 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2380 * performed in a particular thread, prior to a particular fence.
2381 * @param tid The ID of the thread to check
2382 * @param before_fence The fence from which to begin the search; if NULL, then
2383 * search for the most recent fence in the thread.
2384 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2386 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2388 /* All fences should have NULL location */
2389 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2390 action_list_t::reverse_iterator rit = list->rbegin();
2393 for (; rit != list->rend(); rit++)
2394 if (*rit == before_fence)
2397 ASSERT(*rit == before_fence);
2401 for (; rit != list->rend(); rit++)
2402 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2408 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2409 * location). This function identifies the mutex according to the current
2410 * action, which is presumed to perform on the same mutex.
2411 * @param curr The current ModelAction; also denotes the object location to
2413 * @return The last unlock operation
2415 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2417 void *location = curr->get_location();
2418 action_list_t *list = get_safe_ptr_action(obj_map, location);
2419 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2420 action_list_t::reverse_iterator rit;
2421 for (rit = list->rbegin(); rit != list->rend(); rit++)
2422 if ((*rit)->is_unlock() || (*rit)->is_wait())
2427 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2429 ModelAction *parent = get_last_action(tid);
2431 parent = get_thread(tid)->get_creation();
2436 * Returns the clock vector for a given thread.
2437 * @param tid The thread whose clock vector we want
2438 * @return Desired clock vector
2440 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2442 return get_parent_action(tid)->get_cv();
2446 * Resolve a set of Promises with a current write. The set is provided in the
2447 * Node corresponding to @a write.
2448 * @param write The ModelAction that is fulfilling Promises
2449 * @return True if promises were resolved; false otherwise
2451 bool ModelChecker::resolve_promises(ModelAction *write)
2453 bool haveResolved = false;
2454 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2455 promise_list_t mustResolve, resolved;
2457 for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
2458 Promise *promise = (*promises)[promise_index];
2459 if (write->get_node()->get_promise(i)) {
2460 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2461 ModelAction *read = promise->get_reader(j);
2462 read_from(read, write);
2463 actions_to_check.push_back(read);
2465 //Make sure the promise's value matches the write's value
2466 ASSERT(promise->is_compatible(write));
2467 mo_graph->resolvePromise(promise, write, &mustResolve);
2469 resolved.push_back(promise);
2470 promises->erase(promises->begin() + promise_index);
2472 haveResolved = true;
2477 for (unsigned int i = 0; i < mustResolve.size(); i++) {
2478 if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
2480 priv->failed_promise = true;
2482 for (unsigned int i = 0; i < resolved.size(); i++)
2484 //Check whether reading these writes has made threads unable to
2487 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2488 ModelAction *read = actions_to_check[i];
2489 mo_check_promises(read, true);
2492 return haveResolved;
2496 * Compute the set of promises that could potentially be satisfied by this
2497 * action. Note that the set computation actually appears in the Node, not in
2499 * @param curr The ModelAction that may satisfy promises
2501 void ModelChecker::compute_promises(ModelAction *curr)
2503 for (unsigned int i = 0; i < promises->size(); i++) {
2504 Promise *promise = (*promises)[i];
2505 if (!promise->is_compatible(curr) || promise->get_value() != curr->get_value())
2508 bool satisfy = true;
2509 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2510 const ModelAction *act = promise->get_reader(j);
2511 if (act->happens_before(curr) ||
2512 act->could_synchronize_with(curr)) {
2518 curr->get_node()->set_promise(i);
2522 /** Checks promises in response to change in ClockVector Threads. */
2523 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2525 for (unsigned int i = 0; i < promises->size(); i++) {
2526 Promise *promise = (*promises)[i];
2527 if (!promise->thread_is_available(tid))
2529 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2530 const ModelAction *act = promise->get_reader(j);
2531 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2532 merge_cv->synchronized_since(act)) {
2533 if (promise->eliminate_thread(tid)) {
2534 /* Promise has failed */
2535 priv->failed_promise = true;
2543 void ModelChecker::check_promises_thread_disabled()
2545 for (unsigned int i = 0; i < promises->size(); i++) {
2546 Promise *promise = (*promises)[i];
2547 if (promise->has_failed()) {
2548 priv->failed_promise = true;
2555 * @brief Checks promises in response to addition to modification order for
2558 * We test whether threads are still available for satisfying promises after an
2559 * addition to our modification order constraints. Those that are unavailable
2560 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2561 * that promise has failed.
2563 * @param act The ModelAction which updated the modification order
2564 * @param is_read_check Should be true if act is a read and we must check for
2565 * updates to the store from which it read (there is a distinction here for
2566 * RMW's, which are both a load and a store)
2568 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2570 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2572 for (unsigned int i = 0; i < promises->size(); i++) {
2573 Promise *promise = (*promises)[i];
2575 // Is this promise on the same location?
2576 if (promise->get_value() != write->get_value())
2579 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2580 const ModelAction *pread = promise->get_reader(j);
2581 if (!pread->happens_before(act))
2583 if (mo_graph->checkPromise(write, promise)) {
2584 priv->failed_promise = true;
2590 // Don't do any lookups twice for the same thread
2591 if (!promise->thread_is_available(act->get_tid()))
2594 if (mo_graph->checkReachable(promise, write)) {
2595 if (mo_graph->checkPromise(write, promise)) {
2596 priv->failed_promise = true;
2604 * Compute the set of writes that may break the current pending release
2605 * sequence. This information is extracted from previou release sequence
2608 * @param curr The current ModelAction. Must be a release sequence fixup
2611 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2613 if (pending_rel_seqs->empty())
2616 struct release_seq *pending = pending_rel_seqs->back();
2617 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2618 const ModelAction *write = pending->writes[i];
2619 curr->get_node()->add_relseq_break(write);
2622 /* NULL means don't break the sequence; just synchronize */
2623 curr->get_node()->add_relseq_break(NULL);
2627 * Build up an initial set of all past writes that this 'read' action may read
2628 * from, as well as any previously-observed future values that must still be valid.
2630 * @param curr is the current ModelAction that we are exploring; it must be a
2633 void ModelChecker::build_may_read_from(ModelAction *curr)
2635 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2637 ASSERT(curr->is_read());
2639 ModelAction *last_sc_write = NULL;
2641 if (curr->is_seqcst())
2642 last_sc_write = get_last_seq_cst_write(curr);
2644 /* Iterate over all threads */
2645 for (i = 0; i < thrd_lists->size(); i++) {
2646 /* Iterate over actions in thread, starting from most recent */
2647 action_list_t *list = &(*thrd_lists)[i];
2648 action_list_t::reverse_iterator rit;
2649 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2650 ModelAction *act = *rit;
2652 /* Only consider 'write' actions */
2653 if (!act->is_write() || act == curr)
2656 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2657 bool allow_read = true;
2659 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2661 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2665 /* Only add feasible reads */
2666 mo_graph->startChanges();
2667 r_modification_order(curr, act);
2668 if (!is_infeasible())
2669 curr->get_node()->add_read_from_past(act);
2670 mo_graph->rollbackChanges();
2673 /* Include at most one act per-thread that "happens before" curr */
2674 if (act->happens_before(curr))
2679 /* Inherit existing, promised future values */
2680 for (i = 0; i < promises->size(); i++) {
2681 const Promise *promise = (*promises)[i];
2682 const ModelAction *promise_read = promise->get_reader(0);
2683 if (promise_read->same_var(curr)) {
2684 /* Only add feasible future-values */
2685 mo_graph->startChanges();
2686 r_modification_order(curr, promise);
2687 if (!is_infeasible())
2688 curr->get_node()->add_read_from_promise(promise_read);
2689 mo_graph->rollbackChanges();
2693 /* We may find no valid may-read-from only if the execution is doomed */
2694 if (!curr->get_node()->read_from_size()) {
2695 priv->no_valid_reads = true;
2699 if (DBG_ENABLED()) {
2700 model_print("Reached read action:\n");
2702 model_print("Printing read_from_past\n");
2703 curr->get_node()->print_read_from_past();
2704 model_print("End printing read_from_past\n");
2708 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2710 for ( ; write != NULL; write = write->get_reads_from()) {
2711 /* UNINIT actions don't have a Node, and they never sleep */
2712 if (write->is_uninitialized())
2714 Node *prevnode = write->get_node()->get_parent();
2716 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2717 if (write->is_release() && thread_sleep)
2719 if (!write->is_rmw())
2726 * @brief Create a new action representing an uninitialized atomic
2727 * @param location The memory location of the atomic object
2728 * @return A pointer to a new ModelAction
2730 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2732 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2733 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2734 act->create_cv(NULL);
2738 static void print_list(action_list_t *list)
2740 action_list_t::iterator it;
2742 model_print("---------------------------------------------------------------------\n");
2744 unsigned int hash = 0;
2746 for (it = list->begin(); it != list->end(); it++) {
2748 hash = hash^(hash<<3)^((*it)->hash());
2750 model_print("HASH %u\n", hash);
2751 model_print("---------------------------------------------------------------------\n");
2754 #if SUPPORT_MOD_ORDER_DUMP
2755 void ModelChecker::dumpGraph(char *filename) const
2758 sprintf(buffer, "%s.dot", filename);
2759 FILE *file = fopen(buffer, "w");
2760 fprintf(file, "digraph %s {\n", filename);
2761 mo_graph->dumpNodes(file);
2762 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2764 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2765 ModelAction *action = *it;
2766 if (action->is_read()) {
2767 fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
2768 if (action->get_reads_from() != NULL)
2769 fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
2771 if (thread_array[action->get_tid()] != NULL) {
2772 fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
2775 thread_array[action->get_tid()] = action;
2777 fprintf(file, "}\n");
2778 model_free(thread_array);
2783 /** @brief Prints an execution trace summary. */
2784 void ModelChecker::print_summary() const
2786 #if SUPPORT_MOD_ORDER_DUMP
2787 char buffername[100];
2788 sprintf(buffername, "exec%04u", stats.num_total);
2789 mo_graph->dumpGraphToFile(buffername);
2790 sprintf(buffername, "graph%04u", stats.num_total);
2791 dumpGraph(buffername);
2794 model_print("Execution %d:", stats.num_total);
2795 if (isfeasibleprefix())
2798 print_infeasibility(" INFEASIBLE");
2799 print_list(action_trace);
2804 * Add a Thread to the system for the first time. Should only be called once
2806 * @param t The Thread to add
2808 void ModelChecker::add_thread(Thread *t)
2810 thread_map->put(id_to_int(t->get_id()), t);
2811 scheduler->add_thread(t);
2815 * Removes a thread from the scheduler.
2816 * @param the thread to remove.
2818 void ModelChecker::remove_thread(Thread *t)
2820 scheduler->remove_thread(t);
2824 * @brief Get a Thread reference by its ID
2825 * @param tid The Thread's ID
2826 * @return A Thread reference
2828 Thread * ModelChecker::get_thread(thread_id_t tid) const
2830 return thread_map->get(id_to_int(tid));
2834 * @brief Get a reference to the Thread in which a ModelAction was executed
2835 * @param act The ModelAction
2836 * @return A Thread reference
2838 Thread * ModelChecker::get_thread(const ModelAction *act) const
2840 return get_thread(act->get_tid());
2844 * @brief Check if a Thread is currently enabled
2845 * @param t The Thread to check
2846 * @return True if the Thread is currently enabled
2848 bool ModelChecker::is_enabled(Thread *t) const
2850 return scheduler->is_enabled(t);
2854 * @brief Check if a Thread is currently enabled
2855 * @param tid The ID of the Thread to check
2856 * @return True if the Thread is currently enabled
2858 bool ModelChecker::is_enabled(thread_id_t tid) const
2860 return scheduler->is_enabled(tid);
2864 * Switch from a model-checker context to a user-thread context. This is the
2865 * complement of ModelChecker::switch_to_master and must be called from the
2866 * model-checker context
2868 * @param thread The user-thread to switch to
2870 void ModelChecker::switch_from_master(Thread *thread)
2872 scheduler->set_current_thread(thread);
2873 Thread::swap(&system_context, thread);
2877 * Switch from a user-context to the "master thread" context (a.k.a. system
2878 * context). This switch is made with the intention of exploring a particular
2879 * model-checking action (described by a ModelAction object). Must be called
2880 * from a user-thread context.
2882 * @param act The current action that will be explored. May be NULL only if
2883 * trace is exiting via an assertion (see ModelChecker::set_assert and
2884 * ModelChecker::has_asserted).
2885 * @return Return the value returned by the current action
2887 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2890 Thread *old = thread_current();
2891 ASSERT(!old->get_pending());
2892 old->set_pending(act);
2893 if (Thread::swap(old, &system_context) < 0) {
2894 perror("swap threads");
2897 return old->get_return_value();
2901 * Takes the next step in the execution, if possible.
2902 * @param curr The current step to take
2903 * @return Returns the next Thread to run, if any; NULL if this execution
2906 Thread * ModelChecker::take_step(ModelAction *curr)
2908 Thread *curr_thrd = get_thread(curr);
2909 ASSERT(curr_thrd->get_state() == THREAD_READY);
2911 curr = check_current_action(curr);
2913 /* Infeasible -> don't take any more steps */
2914 if (is_infeasible())
2916 else if (isfeasibleprefix() && have_bug_reports()) {
2921 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2924 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2925 scheduler->remove_thread(curr_thrd);
2927 Thread *next_thrd = get_next_thread(curr);
2929 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2930 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
2935 /** Wrapper to run the user's main function, with appropriate arguments */
2936 void user_main_wrapper(void *)
2938 user_main(model->params.argc, model->params.argv);
2941 /** @brief Run ModelChecker for the user program */
2942 void ModelChecker::run()
2946 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
2951 * Stash next pending action(s) for thread(s). There
2952 * should only need to stash one thread's action--the
2953 * thread which just took a step--plus the first step
2954 * for any newly-created thread
2956 for (unsigned int i = 0; i < get_num_threads(); i++) {
2957 thread_id_t tid = int_to_id(i);
2958 Thread *thr = get_thread(tid);
2959 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
2960 switch_from_master(thr);
2964 /* Catch assertions from prior take_step or from
2965 * between-ModelAction bugs (e.g., data races) */
2969 /* Consume the next action for a Thread */
2970 ModelAction *curr = t->get_pending();
2971 t->set_pending(NULL);
2972 t = take_step(curr);
2973 } while (t && !t->is_model_thread());
2976 * Launch end-of-execution release sequence fixups only when
2977 * the execution is otherwise feasible AND there are:
2979 * (1) pending release sequences
2980 * (2) pending assertions that could be invalidated by a change
2981 * in clock vectors (i.e., data races)
2982 * (3) no pending promises
2984 while (!pending_rel_seqs->empty() &&
2985 is_feasible_prefix_ignore_relseq() &&
2986 !unrealizedraces.empty()) {
2987 model_print("*** WARNING: release sequence fixup action "
2988 "(%zu pending release seuqence(s)) ***\n",
2989 pending_rel_seqs->size());
2990 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
2991 std::memory_order_seq_cst, NULL, VALUE_NONE,
2995 } while (next_execution());
2997 model_print("******* Model-checking complete: *******\n");