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;
857 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();
865 value = rf->get_value();
866 check_recency(curr, rf);
867 bool r_status = r_modification_order(curr, rf);
869 if (is_infeasible() && node->increment_read_from()) {
870 mo_graph->rollbackChanges();
871 priv->too_many_reads = false;
876 mo_graph->commitChanges();
877 mo_check_promises(curr, true);
882 case READ_FROM_PROMISE: {
883 Promise *promise = curr->get_node()->get_read_from_promise();
884 promise->add_reader(curr);
885 value = promise->get_value();
886 curr->set_read_from_promise(promise);
887 mo_graph->startChanges();
888 updated = r_modification_order(curr, promise);
889 mo_graph->commitChanges();
892 case READ_FROM_FUTURE: {
893 /* Read from future value */
894 struct future_value fv = node->get_future_value();
895 Promise *promise = new Promise(curr, fv);
897 curr->set_read_from_promise(promise);
898 promises->push_back(promise);
899 mo_graph->startChanges();
900 updated = r_modification_order(curr, promise);
901 mo_graph->commitChanges();
907 get_thread(curr)->set_return_value(value);
913 * Processes a lock, trylock, or unlock model action. @param curr is
914 * the read model action to process.
916 * The try lock operation checks whether the lock is taken. If not,
917 * it falls to the normal lock operation case. If so, it returns
920 * The lock operation has already been checked that it is enabled, so
921 * it just grabs the lock and synchronizes with the previous unlock.
923 * The unlock operation has to re-enable all of the threads that are
924 * waiting on the lock.
926 * @return True if synchronization was updated; false otherwise
928 bool ModelChecker::process_mutex(ModelAction *curr)
930 std::mutex *mutex = NULL;
931 struct std::mutex_state *state = NULL;
933 if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
934 mutex = (std::mutex *)curr->get_location();
935 state = mutex->get_state();
936 } else if (curr->is_wait()) {
937 mutex = (std::mutex *)curr->get_value();
938 state = mutex->get_state();
941 switch (curr->get_type()) {
942 case ATOMIC_TRYLOCK: {
943 bool success = !state->islocked;
944 curr->set_try_lock(success);
946 get_thread(curr)->set_return_value(0);
949 get_thread(curr)->set_return_value(1);
951 //otherwise fall into the lock case
953 if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
954 assert_bug("Lock access before initialization");
955 state->islocked = true;
956 ModelAction *unlock = get_last_unlock(curr);
957 //synchronize with the previous unlock statement
958 if (unlock != NULL) {
959 curr->synchronize_with(unlock);
964 case ATOMIC_UNLOCK: {
966 state->islocked = false;
967 //wake up the other threads
968 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
969 //activate all the waiting threads
970 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
971 scheduler->wake(get_thread(*rit));
978 state->islocked = false;
979 //wake up the other threads
980 action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
981 //activate all the waiting threads
982 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
983 scheduler->wake(get_thread(*rit));
986 //check whether we should go to sleep or not...simulate spurious failures
987 if (curr->get_node()->get_misc() == 0) {
988 get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
990 scheduler->sleep(get_thread(curr));
994 case ATOMIC_NOTIFY_ALL: {
995 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
996 //activate all the waiting threads
997 for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
998 scheduler->wake(get_thread(*rit));
1003 case ATOMIC_NOTIFY_ONE: {
1004 action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
1005 int wakeupthread = curr->get_node()->get_misc();
1006 action_list_t::iterator it = waiters->begin();
1007 advance(it, wakeupthread);
1008 scheduler->wake(get_thread(*it));
1019 void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
1021 /* Do more ambitious checks now that mo is more complete */
1022 if (mo_may_allow(writer, reader)) {
1023 Node *node = reader->get_node();
1025 /* Find an ancestor thread which exists at the time of the reader */
1026 Thread *write_thread = get_thread(writer);
1027 while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
1028 write_thread = write_thread->get_parent();
1030 struct future_value fv = {
1031 writer->get_write_value(),
1032 writer->get_seq_number() + params.maxfuturedelay,
1033 write_thread->get_id(),
1035 if (node->add_future_value(fv))
1036 set_latest_backtrack(reader);
1041 * Process a write ModelAction
1042 * @param curr The ModelAction to process
1043 * @return True if the mo_graph was updated or promises were resolved
1045 bool ModelChecker::process_write(ModelAction *curr)
1047 /* Readers to which we may send our future value */
1048 std::vector< ModelAction *, ModelAlloc<ModelAction *> > send_fv;
1050 bool updated_mod_order = w_modification_order(curr, &send_fv);
1051 int promise_idx = get_promise_to_resolve(curr);
1052 const ModelAction *earliest_promise_reader;
1053 bool updated_promises = false;
1055 if (promise_idx >= 0) {
1056 earliest_promise_reader = (*promises)[promise_idx]->get_reader(0);
1057 updated_promises = resolve_promise(curr, promise_idx);
1059 earliest_promise_reader = NULL;
1061 /* Don't send future values to reads after the Promise we resolve */
1062 for (unsigned int i = 0; i < send_fv.size(); i++) {
1063 ModelAction *read = send_fv[i];
1064 if (!earliest_promise_reader || *read < *earliest_promise_reader)
1065 futurevalues->push_back(PendingFutureValue(curr, read));
1068 if (promises->size() == 0) {
1069 for (unsigned int i = 0; i < futurevalues->size(); i++) {
1070 struct PendingFutureValue pfv = (*futurevalues)[i];
1071 add_future_value(pfv.writer, pfv.act);
1073 futurevalues->clear();
1076 mo_graph->commitChanges();
1077 mo_check_promises(curr, false);
1079 get_thread(curr)->set_return_value(VALUE_NONE);
1080 return updated_mod_order || updated_promises;
1084 * Process a fence ModelAction
1085 * @param curr The ModelAction to process
1086 * @return True if synchronization was updated
1088 bool ModelChecker::process_fence(ModelAction *curr)
1091 * fence-relaxed: no-op
1092 * fence-release: only log the occurence (not in this function), for
1093 * use in later synchronization
1094 * fence-acquire (this function): search for hypothetical release
1097 bool updated = false;
1098 if (curr->is_acquire()) {
1099 action_list_t *list = action_trace;
1100 action_list_t::reverse_iterator rit;
1101 /* Find X : is_read(X) && X --sb-> curr */
1102 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1103 ModelAction *act = *rit;
1106 if (act->get_tid() != curr->get_tid())
1108 /* Stop at the beginning of the thread */
1109 if (act->is_thread_start())
1111 /* Stop once we reach a prior fence-acquire */
1112 if (act->is_fence() && act->is_acquire())
1114 if (!act->is_read())
1116 /* read-acquire will find its own release sequences */
1117 if (act->is_acquire())
1120 /* Establish hypothetical release sequences */
1121 rel_heads_list_t release_heads;
1122 get_release_seq_heads(curr, act, &release_heads);
1123 for (unsigned int i = 0; i < release_heads.size(); i++)
1124 if (!curr->synchronize_with(release_heads[i]))
1125 set_bad_synchronization();
1126 if (release_heads.size() != 0)
1134 * @brief Process the current action for thread-related activity
1136 * Performs current-action processing for a THREAD_* ModelAction. Proccesses
1137 * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
1138 * synchronization, etc. This function is a no-op for non-THREAD actions
1139 * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
1141 * @param curr The current action
1142 * @return True if synchronization was updated or a thread completed
1144 bool ModelChecker::process_thread_action(ModelAction *curr)
1146 bool updated = false;
1148 switch (curr->get_type()) {
1149 case THREAD_CREATE: {
1150 thrd_t *thrd = (thrd_t *)curr->get_location();
1151 struct thread_params *params = (struct thread_params *)curr->get_value();
1152 Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
1154 th->set_creation(curr);
1155 /* Promises can be satisfied by children */
1156 for (unsigned int i = 0; i < promises->size(); i++) {
1157 Promise *promise = (*promises)[i];
1158 if (promise->thread_is_available(curr->get_tid()))
1159 promise->add_thread(th->get_id());
1164 Thread *blocking = curr->get_thread_operand();
1165 ModelAction *act = get_last_action(blocking->get_id());
1166 curr->synchronize_with(act);
1167 updated = true; /* trigger rel-seq checks */
1170 case THREAD_FINISH: {
1171 Thread *th = get_thread(curr);
1172 while (!th->wait_list_empty()) {
1173 ModelAction *act = th->pop_wait_list();
1174 scheduler->wake(get_thread(act));
1177 /* Completed thread can't satisfy promises */
1178 for (unsigned int i = 0; i < promises->size(); i++) {
1179 Promise *promise = (*promises)[i];
1180 if (promise->thread_is_available(th->get_id()))
1181 if (promise->eliminate_thread(th->get_id()))
1182 priv->failed_promise = true;
1184 updated = true; /* trigger rel-seq checks */
1187 case THREAD_START: {
1188 check_promises(curr->get_tid(), NULL, curr->get_cv());
1199 * @brief Process the current action for release sequence fixup activity
1201 * Performs model-checker release sequence fixups for the current action,
1202 * forcing a single pending release sequence to break (with a given, potential
1203 * "loose" write) or to complete (i.e., synchronize). If a pending release
1204 * sequence forms a complete release sequence, then we must perform the fixup
1205 * synchronization, mo_graph additions, etc.
1207 * @param curr The current action; must be a release sequence fixup action
1208 * @param work_queue The work queue to which to add work items as they are
1211 void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
1213 const ModelAction *write = curr->get_node()->get_relseq_break();
1214 struct release_seq *sequence = pending_rel_seqs->back();
1215 pending_rel_seqs->pop_back();
1217 ModelAction *acquire = sequence->acquire;
1218 const ModelAction *rf = sequence->rf;
1219 const ModelAction *release = sequence->release;
1223 ASSERT(release->same_thread(rf));
1225 if (write == NULL) {
1227 * @todo Forcing a synchronization requires that we set
1228 * modification order constraints. For instance, we can't allow
1229 * a fixup sequence in which two separate read-acquire
1230 * operations read from the same sequence, where the first one
1231 * synchronizes and the other doesn't. Essentially, we can't
1232 * allow any writes to insert themselves between 'release' and
1236 /* Must synchronize */
1237 if (!acquire->synchronize_with(release)) {
1238 set_bad_synchronization();
1241 /* Re-check all pending release sequences */
1242 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
1243 /* Re-check act for mo_graph edges */
1244 work_queue->push_back(MOEdgeWorkEntry(acquire));
1246 /* propagate synchronization to later actions */
1247 action_list_t::reverse_iterator rit = action_trace->rbegin();
1248 for (; (*rit) != acquire; rit++) {
1249 ModelAction *propagate = *rit;
1250 if (acquire->happens_before(propagate)) {
1251 propagate->synchronize_with(acquire);
1252 /* Re-check 'propagate' for mo_graph edges */
1253 work_queue->push_back(MOEdgeWorkEntry(propagate));
1257 /* Break release sequence with new edges:
1258 * release --mo--> write --mo--> rf */
1259 mo_graph->addEdge(release, write);
1260 mo_graph->addEdge(write, rf);
1263 /* See if we have realized a data race */
1268 * Initialize the current action by performing one or more of the following
1269 * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
1270 * in the NodeStack, manipulating backtracking sets, allocating and
1271 * initializing clock vectors, and computing the promises to fulfill.
1273 * @param curr The current action, as passed from the user context; may be
1274 * freed/invalidated after the execution of this function, with a different
1275 * action "returned" its place (pass-by-reference)
1276 * @return True if curr is a newly-explored action; false otherwise
1278 bool ModelChecker::initialize_curr_action(ModelAction **curr)
1280 ModelAction *newcurr;
1282 if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
1283 newcurr = process_rmw(*curr);
1286 if (newcurr->is_rmw())
1287 compute_promises(newcurr);
1293 (*curr)->set_seq_number(get_next_seq_num());
1295 newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
1297 /* First restore type and order in case of RMW operation */
1298 if ((*curr)->is_rmwr())
1299 newcurr->copy_typeandorder(*curr);
1301 ASSERT((*curr)->get_location() == newcurr->get_location());
1302 newcurr->copy_from_new(*curr);
1304 /* Discard duplicate ModelAction; use action from NodeStack */
1307 /* Always compute new clock vector */
1308 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1311 return false; /* Action was explored previously */
1315 /* Always compute new clock vector */
1316 newcurr->create_cv(get_parent_action(newcurr->get_tid()));
1318 /* Assign most recent release fence */
1319 newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
1322 * Perform one-time actions when pushing new ModelAction onto
1325 if (newcurr->is_write())
1326 compute_promises(newcurr);
1327 else if (newcurr->is_relseq_fixup())
1328 compute_relseq_breakwrites(newcurr);
1329 else if (newcurr->is_wait())
1330 newcurr->get_node()->set_misc_max(2);
1331 else if (newcurr->is_notify_one()) {
1332 newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
1334 return true; /* This was a new ModelAction */
1339 * @brief Establish reads-from relation between two actions
1341 * Perform basic operations involved with establishing a concrete rf relation,
1342 * including setting the ModelAction data and checking for release sequences.
1344 * @param act The action that is reading (must be a read)
1345 * @param rf The action from which we are reading (must be a write)
1347 * @return True if this read established synchronization
1349 bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
1352 act->set_read_from(rf);
1353 if (act->is_acquire()) {
1354 rel_heads_list_t release_heads;
1355 get_release_seq_heads(act, act, &release_heads);
1356 int num_heads = release_heads.size();
1357 for (unsigned int i = 0; i < release_heads.size(); i++)
1358 if (!act->synchronize_with(release_heads[i])) {
1359 set_bad_synchronization();
1362 return num_heads > 0;
1368 * Check promises and eliminate potentially-satisfying threads when a thread is
1369 * blocked (e.g., join, lock). A thread which is waiting on another thread can
1370 * no longer satisfy a promise generated from that thread.
1372 * @param blocker The thread on which a thread is waiting
1373 * @param waiting The waiting thread
1375 void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
1377 for (unsigned int i = 0; i < promises->size(); i++) {
1378 Promise *promise = (*promises)[i];
1379 if (!promise->thread_is_available(waiting->get_id()))
1381 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
1382 ModelAction *reader = promise->get_reader(j);
1383 if (reader->get_tid() != blocker->get_id())
1385 if (promise->eliminate_thread(waiting->get_id())) {
1386 /* Promise has failed */
1387 priv->failed_promise = true;
1389 /* Only eliminate the 'waiting' thread once */
1397 * @brief Check whether a model action is enabled.
1399 * Checks whether a lock or join operation would be successful (i.e., is the
1400 * lock already locked, or is the joined thread already complete). If not, put
1401 * the action in a waiter list.
1403 * @param curr is the ModelAction to check whether it is enabled.
1404 * @return a bool that indicates whether the action is enabled.
1406 bool ModelChecker::check_action_enabled(ModelAction *curr) {
1407 if (curr->is_lock()) {
1408 std::mutex *lock = (std::mutex *)curr->get_location();
1409 struct std::mutex_state *state = lock->get_state();
1410 if (state->islocked) {
1411 //Stick the action in the appropriate waiting queue
1412 get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
1415 } else if (curr->get_type() == THREAD_JOIN) {
1416 Thread *blocking = (Thread *)curr->get_location();
1417 if (!blocking->is_complete()) {
1418 blocking->push_wait_list(curr);
1419 thread_blocking_check_promises(blocking, get_thread(curr));
1428 * This is the heart of the model checker routine. It performs model-checking
1429 * actions corresponding to a given "current action." Among other processes, it
1430 * calculates reads-from relationships, updates synchronization clock vectors,
1431 * forms a memory_order constraints graph, and handles replay/backtrack
1432 * execution when running permutations of previously-observed executions.
1434 * @param curr The current action to process
1435 * @return The ModelAction that is actually executed; may be different than
1436 * curr; may be NULL, if the current action is not enabled to run
1438 ModelAction * ModelChecker::check_current_action(ModelAction *curr)
1441 bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
1443 if (!check_action_enabled(curr)) {
1444 /* Make the execution look like we chose to run this action
1445 * much later, when a lock/join can succeed */
1446 get_thread(curr)->set_pending(curr);
1447 scheduler->sleep(get_thread(curr));
1451 bool newly_explored = initialize_curr_action(&curr);
1457 wake_up_sleeping_actions(curr);
1459 /* Add the action to lists before any other model-checking tasks */
1460 if (!second_part_of_rmw)
1461 add_action_to_lists(curr);
1463 /* Build may_read_from set for newly-created actions */
1464 if (newly_explored && curr->is_read())
1465 build_may_read_from(curr);
1467 /* Initialize work_queue with the "current action" work */
1468 work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
1469 while (!work_queue.empty() && !has_asserted()) {
1470 WorkQueueEntry work = work_queue.front();
1471 work_queue.pop_front();
1473 switch (work.type) {
1474 case WORK_CHECK_CURR_ACTION: {
1475 ModelAction *act = work.action;
1476 bool update = false; /* update this location's release seq's */
1477 bool update_all = false; /* update all release seq's */
1479 if (process_thread_action(curr))
1482 if (act->is_read() && !second_part_of_rmw && process_read(act))
1485 if (act->is_write() && process_write(act))
1488 if (act->is_fence() && process_fence(act))
1491 if (act->is_mutex_op() && process_mutex(act))
1494 if (act->is_relseq_fixup())
1495 process_relseq_fixup(curr, &work_queue);
1498 work_queue.push_back(CheckRelSeqWorkEntry(NULL));
1500 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1503 case WORK_CHECK_RELEASE_SEQ:
1504 resolve_release_sequences(work.location, &work_queue);
1506 case WORK_CHECK_MO_EDGES: {
1507 /** @todo Complete verification of work_queue */
1508 ModelAction *act = work.action;
1509 bool updated = false;
1511 if (act->is_read()) {
1512 const ModelAction *rf = act->get_reads_from();
1513 const Promise *promise = act->get_reads_from_promise();
1515 if (r_modification_order(act, rf))
1517 } else if (promise) {
1518 if (r_modification_order(act, promise))
1522 if (act->is_write()) {
1523 if (w_modification_order(act, NULL))
1526 mo_graph->commitChanges();
1529 work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
1538 check_curr_backtracking(curr);
1539 set_backtracking(curr);
1543 void ModelChecker::check_curr_backtracking(ModelAction *curr)
1545 Node *currnode = curr->get_node();
1546 Node *parnode = currnode->get_parent();
1548 if ((parnode && !parnode->backtrack_empty()) ||
1549 !currnode->misc_empty() ||
1550 !currnode->read_from_empty() ||
1551 !currnode->promise_empty() ||
1552 !currnode->relseq_break_empty()) {
1553 set_latest_backtrack(curr);
1557 bool ModelChecker::promises_expired() const
1559 for (unsigned int i = 0; i < promises->size(); i++) {
1560 Promise *promise = (*promises)[i];
1561 if (promise->get_expiration() < priv->used_sequence_numbers)
1568 * This is the strongest feasibility check available.
1569 * @return whether the current trace (partial or complete) must be a prefix of
1572 bool ModelChecker::isfeasibleprefix() const
1574 return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
1578 * Print disagnostic information about an infeasible execution
1579 * @param prefix A string to prefix the output with; if NULL, then a default
1580 * message prefix will be provided
1582 void ModelChecker::print_infeasibility(const char *prefix) const
1586 if (mo_graph->checkForCycles())
1587 ptr += sprintf(ptr, "[mo cycle]");
1588 if (priv->failed_promise)
1589 ptr += sprintf(ptr, "[failed promise]");
1590 if (priv->too_many_reads)
1591 ptr += sprintf(ptr, "[too many reads]");
1592 if (priv->no_valid_reads)
1593 ptr += sprintf(ptr, "[no valid reads-from]");
1594 if (priv->bad_synchronization)
1595 ptr += sprintf(ptr, "[bad sw ordering]");
1596 if (promises_expired())
1597 ptr += sprintf(ptr, "[promise expired]");
1598 if (promises->size() != 0)
1599 ptr += sprintf(ptr, "[unresolved promise]");
1601 model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
1605 * Returns whether the current completed trace is feasible, except for pending
1606 * release sequences.
1608 bool ModelChecker::is_feasible_prefix_ignore_relseq() const
1610 return !is_infeasible() && promises->size() == 0;
1614 * Check if the current partial trace is infeasible. Does not check any
1615 * end-of-execution flags, which might rule out the execution. Thus, this is
1616 * useful only for ruling an execution as infeasible.
1617 * @return whether the current partial trace is infeasible.
1619 bool ModelChecker::is_infeasible() const
1621 return mo_graph->checkForCycles() ||
1622 priv->no_valid_reads ||
1623 priv->failed_promise ||
1624 priv->too_many_reads ||
1625 priv->bad_synchronization ||
1629 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
1630 ModelAction * ModelChecker::process_rmw(ModelAction *act) {
1631 ModelAction *lastread = get_last_action(act->get_tid());
1632 lastread->process_rmw(act);
1633 if (act->is_rmw()) {
1634 if (lastread->get_reads_from())
1635 mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
1637 mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
1638 mo_graph->commitChanges();
1644 * Checks whether a thread has read from the same write for too many times
1645 * without seeing the effects of a later write.
1648 * 1) there must a different write that we could read from that would satisfy the modification order,
1649 * 2) we must have read from the same value in excess of maxreads times, and
1650 * 3) that other write must have been in the reads_from set for maxreads times.
1652 * If so, we decide that the execution is no longer feasible.
1654 void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
1656 if (params.maxreads != 0) {
1657 if (curr->get_node()->get_read_from_past_size() <= 1)
1659 //Must make sure that execution is currently feasible... We could
1660 //accidentally clear by rolling back
1661 if (is_infeasible())
1663 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1664 int tid = id_to_int(curr->get_tid());
1667 if ((int)thrd_lists->size() <= tid)
1669 action_list_t *list = &(*thrd_lists)[tid];
1671 action_list_t::reverse_iterator rit = list->rbegin();
1672 /* Skip past curr */
1673 for (; (*rit) != curr; rit++)
1675 /* go past curr now */
1678 action_list_t::reverse_iterator ritcopy = rit;
1679 //See if we have enough reads from the same value
1681 for (; count < params.maxreads; rit++, count++) {
1682 if (rit == list->rend())
1684 ModelAction *act = *rit;
1685 if (!act->is_read())
1688 if (act->get_reads_from() != rf)
1690 if (act->get_node()->get_read_from_past_size() <= 1)
1693 for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
1695 const ModelAction *write = curr->get_node()->get_read_from_past(i);
1697 /* Need a different write */
1701 /* Test to see whether this is a feasible write to read from */
1702 /** NOTE: all members of read-from set should be
1703 * feasible, so we no longer check it here **/
1707 bool feasiblewrite = true;
1708 //new we need to see if this write works for everyone
1710 for (int loop = count; loop > 0; loop--, rit++) {
1711 ModelAction *act = *rit;
1712 bool foundvalue = false;
1713 for (int j = 0; j < act->get_node()->get_read_from_past_size(); j++) {
1714 if (act->get_node()->get_read_from_past(j) == write) {
1720 feasiblewrite = false;
1724 if (feasiblewrite) {
1725 priv->too_many_reads = true;
1733 * Updates the mo_graph with the constraints imposed from the current
1736 * Basic idea is the following: Go through each other thread and find
1737 * the last action that happened before our read. Two cases:
1739 * (1) The action is a write => that write must either occur before
1740 * the write we read from or be the write we read from.
1742 * (2) The action is a read => the write that that action read from
1743 * must occur before the write we read from or be the same write.
1745 * @param curr The current action. Must be a read.
1746 * @param rf The ModelAction or Promise that curr reads from. Must be a write.
1747 * @return True if modification order edges were added; false otherwise
1749 template <typename rf_type>
1750 bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
1752 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1755 ASSERT(curr->is_read());
1757 /* Last SC fence in the current thread */
1758 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1760 /* Iterate over all threads */
1761 for (i = 0; i < thrd_lists->size(); i++) {
1762 /* Last SC fence in thread i */
1763 ModelAction *last_sc_fence_thread_local = NULL;
1764 if (int_to_id((int)i) != curr->get_tid())
1765 last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
1767 /* Last SC fence in thread i, before last SC fence in current thread */
1768 ModelAction *last_sc_fence_thread_before = NULL;
1769 if (last_sc_fence_local)
1770 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1772 /* Iterate over actions in thread, starting from most recent */
1773 action_list_t *list = &(*thrd_lists)[i];
1774 action_list_t::reverse_iterator rit;
1775 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1776 ModelAction *act = *rit;
1778 if (act->is_write() && !act->equals(rf) && act != curr) {
1779 /* C++, Section 29.3 statement 5 */
1780 if (curr->is_seqcst() && last_sc_fence_thread_local &&
1781 *act < *last_sc_fence_thread_local) {
1782 added = mo_graph->addEdge(act, rf) || added;
1785 /* C++, Section 29.3 statement 4 */
1786 else if (act->is_seqcst() && last_sc_fence_local &&
1787 *act < *last_sc_fence_local) {
1788 added = mo_graph->addEdge(act, rf) || added;
1791 /* C++, Section 29.3 statement 6 */
1792 else if (last_sc_fence_thread_before &&
1793 *act < *last_sc_fence_thread_before) {
1794 added = mo_graph->addEdge(act, rf) || added;
1800 * Include at most one act per-thread that "happens
1801 * before" curr. Don't consider reflexively.
1803 if (act->happens_before(curr) && act != curr) {
1804 if (act->is_write()) {
1805 if (!act->equals(rf)) {
1806 added = mo_graph->addEdge(act, rf) || added;
1809 const ModelAction *prevrf = act->get_reads_from();
1810 const Promise *prevrf_promise = act->get_reads_from_promise();
1812 if (!prevrf->equals(rf))
1813 added = mo_graph->addEdge(prevrf, rf) || added;
1814 } else if (!prevrf_promise->equals(rf)) {
1815 added = mo_graph->addEdge(prevrf_promise, rf) || added;
1824 * All compatible, thread-exclusive promises must be ordered after any
1825 * concrete loads from the same thread
1827 for (unsigned int i = 0; i < promises->size(); i++)
1828 if ((*promises)[i]->is_compatible_exclusive(curr))
1829 added = mo_graph->addEdge(rf, (*promises)[i]) || added;
1835 * Updates the mo_graph with the constraints imposed from the current write.
1837 * Basic idea is the following: Go through each other thread and find
1838 * the lastest action that happened before our write. Two cases:
1840 * (1) The action is a write => that write must occur before
1843 * (2) The action is a read => the write that that action read from
1844 * must occur before the current write.
1846 * This method also handles two other issues:
1848 * (I) Sequential Consistency: Making sure that if the current write is
1849 * seq_cst, that it occurs after the previous seq_cst write.
1851 * (II) Sending the write back to non-synchronizing reads.
1853 * @param curr The current action. Must be a write.
1854 * @param send_fv A vector for stashing reads to which we may pass our future
1855 * value. If NULL, then don't record any future values.
1856 * @return True if modification order edges were added; false otherwise
1858 bool ModelChecker::w_modification_order(ModelAction *curr, std::vector< ModelAction *, ModelAlloc<ModelAction *> > *send_fv)
1860 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
1863 ASSERT(curr->is_write());
1865 if (curr->is_seqcst()) {
1866 /* We have to at least see the last sequentially consistent write,
1867 so we are initialized. */
1868 ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
1869 if (last_seq_cst != NULL) {
1870 added = mo_graph->addEdge(last_seq_cst, curr) || added;
1874 /* Last SC fence in the current thread */
1875 ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
1877 /* Iterate over all threads */
1878 for (i = 0; i < thrd_lists->size(); i++) {
1879 /* Last SC fence in thread i, before last SC fence in current thread */
1880 ModelAction *last_sc_fence_thread_before = NULL;
1881 if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
1882 last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
1884 /* Iterate over actions in thread, starting from most recent */
1885 action_list_t *list = &(*thrd_lists)[i];
1886 action_list_t::reverse_iterator rit;
1887 for (rit = list->rbegin(); rit != list->rend(); rit++) {
1888 ModelAction *act = *rit;
1891 * 1) If RMW and it actually read from something, then we
1892 * already have all relevant edges, so just skip to next
1895 * 2) If RMW and it didn't read from anything, we should
1896 * whatever edge we can get to speed up convergence.
1898 * 3) If normal write, we need to look at earlier actions, so
1899 * continue processing list.
1901 if (curr->is_rmw()) {
1902 if (curr->get_reads_from() != NULL)
1910 /* C++, Section 29.3 statement 7 */
1911 if (last_sc_fence_thread_before && act->is_write() &&
1912 *act < *last_sc_fence_thread_before) {
1913 added = mo_graph->addEdge(act, curr) || added;
1918 * Include at most one act per-thread that "happens
1921 if (act->happens_before(curr)) {
1923 * Note: if act is RMW, just add edge:
1925 * The following edge should be handled elsewhere:
1926 * readfrom(act) --mo--> act
1928 if (act->is_write())
1929 added = mo_graph->addEdge(act, curr) || added;
1930 else if (act->is_read()) {
1931 //if previous read accessed a null, just keep going
1932 if (act->get_reads_from() == NULL)
1934 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
1937 } else if (act->is_read() && !act->could_synchronize_with(curr) &&
1938 !act->same_thread(curr)) {
1939 /* We have an action that:
1940 (1) did not happen before us
1941 (2) is a read and we are a write
1942 (3) cannot synchronize with us
1943 (4) is in a different thread
1945 that read could potentially read from our write. Note that
1946 these checks are overly conservative at this point, we'll
1947 do more checks before actually removing the
1951 if (send_fv && thin_air_constraint_may_allow(curr, act)) {
1952 if (!is_infeasible())
1953 send_fv->push_back(act);
1954 else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
1955 add_future_value(curr, act);
1962 * All compatible, thread-exclusive promises must be ordered after any
1963 * concrete stores to the same thread, or else they can be merged with
1966 for (unsigned int i = 0; i < promises->size(); i++)
1967 if ((*promises)[i]->is_compatible_exclusive(curr))
1968 added = mo_graph->addEdge(curr, (*promises)[i]) || added;
1973 /** Arbitrary reads from the future are not allowed. Section 29.3
1974 * part 9 places some constraints. This method checks one result of constraint
1975 * constraint. Others require compiler support. */
1976 bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
1978 if (!writer->is_rmw())
1981 if (!reader->is_rmw())
1984 for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
1985 if (search == reader)
1987 if (search->get_tid() == reader->get_tid() &&
1988 search->happens_before(reader))
1996 * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
1997 * some constraints. This method checks one the following constraint (others
1998 * require compiler support):
2000 * If X --hb-> Y --mo-> Z, then X should not read from Z.
2002 bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
2004 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
2006 /* Iterate over all threads */
2007 for (i = 0; i < thrd_lists->size(); i++) {
2008 const ModelAction *write_after_read = NULL;
2010 /* Iterate over actions in thread, starting from most recent */
2011 action_list_t *list = &(*thrd_lists)[i];
2012 action_list_t::reverse_iterator rit;
2013 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2014 ModelAction *act = *rit;
2016 /* Don't disallow due to act == reader */
2017 if (!reader->happens_before(act) || reader == act)
2019 else if (act->is_write())
2020 write_after_read = act;
2021 else if (act->is_read() && act->get_reads_from() != NULL)
2022 write_after_read = act->get_reads_from();
2025 if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
2032 * Finds the head(s) of the release sequence(s) containing a given ModelAction.
2033 * The ModelAction under consideration is expected to be taking part in
2034 * release/acquire synchronization as an object of the "reads from" relation.
2035 * Note that this can only provide release sequence support for RMW chains
2036 * which do not read from the future, as those actions cannot be traced until
2037 * their "promise" is fulfilled. Similarly, we may not even establish the
2038 * presence of a release sequence with certainty, as some modification order
2039 * constraints may be decided further in the future. Thus, this function
2040 * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
2041 * and a boolean representing certainty.
2043 * @param rf The action that might be part of a release sequence. Must be a
2045 * @param release_heads A pass-by-reference style return parameter. After
2046 * execution of this function, release_heads will contain the heads of all the
2047 * relevant release sequences, if any exists with certainty
2048 * @param pending A pass-by-reference style return parameter which is only used
2049 * when returning false (i.e., uncertain). Returns most information regarding
2050 * an uncertain release sequence, including any write operations that might
2051 * break the sequence.
2052 * @return true, if the ModelChecker is certain that release_heads is complete;
2055 bool ModelChecker::release_seq_heads(const ModelAction *rf,
2056 rel_heads_list_t *release_heads,
2057 struct release_seq *pending) const
2059 /* Only check for release sequences if there are no cycles */
2060 if (mo_graph->checkForCycles())
2063 for ( ; rf != NULL; rf = rf->get_reads_from()) {
2064 ASSERT(rf->is_write());
2066 if (rf->is_release())
2067 release_heads->push_back(rf);
2068 else if (rf->get_last_fence_release())
2069 release_heads->push_back(rf->get_last_fence_release());
2071 break; /* End of RMW chain */
2073 /** @todo Need to be smarter here... In the linux lock
2074 * example, this will run to the beginning of the program for
2076 /** @todo The way to be smarter here is to keep going until 1
2077 * thread has a release preceded by an acquire and you've seen
2080 /* acq_rel RMW is a sufficient stopping condition */
2081 if (rf->is_acquire() && rf->is_release())
2082 return true; /* complete */
2085 /* read from future: need to settle this later */
2087 return false; /* incomplete */
2090 if (rf->is_release())
2091 return true; /* complete */
2093 /* else relaxed write
2094 * - check for fence-release in the same thread (29.8, stmt. 3)
2095 * - check modification order for contiguous subsequence
2096 * -> rf must be same thread as release */
2098 const ModelAction *fence_release = rf->get_last_fence_release();
2099 /* Synchronize with a fence-release unconditionally; we don't need to
2100 * find any more "contiguous subsequence..." for it */
2102 release_heads->push_back(fence_release);
2104 int tid = id_to_int(rf->get_tid());
2105 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
2106 action_list_t *list = &(*thrd_lists)[tid];
2107 action_list_t::const_reverse_iterator rit;
2109 /* Find rf in the thread list */
2110 rit = std::find(list->rbegin(), list->rend(), rf);
2111 ASSERT(rit != list->rend());
2113 /* Find the last {write,fence}-release */
2114 for (; rit != list->rend(); rit++) {
2115 if (fence_release && *(*rit) < *fence_release)
2117 if ((*rit)->is_release())
2120 if (rit == list->rend()) {
2121 /* No write-release in this thread */
2122 return true; /* complete */
2123 } else if (fence_release && *(*rit) < *fence_release) {
2124 /* The fence-release is more recent (and so, "stronger") than
2125 * the most recent write-release */
2126 return true; /* complete */
2127 } /* else, need to establish contiguous release sequence */
2128 ModelAction *release = *rit;
2130 ASSERT(rf->same_thread(release));
2132 pending->writes.clear();
2134 bool certain = true;
2135 for (unsigned int i = 0; i < thrd_lists->size(); i++) {
2136 if (id_to_int(rf->get_tid()) == (int)i)
2138 list = &(*thrd_lists)[i];
2140 /* Can we ensure no future writes from this thread may break
2141 * the release seq? */
2142 bool future_ordered = false;
2144 ModelAction *last = get_last_action(int_to_id(i));
2145 Thread *th = get_thread(int_to_id(i));
2146 if ((last && rf->happens_before(last)) ||
2149 future_ordered = true;
2151 ASSERT(!th->is_model_thread() || future_ordered);
2153 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2154 const ModelAction *act = *rit;
2155 /* Reach synchronization -> this thread is complete */
2156 if (act->happens_before(release))
2158 if (rf->happens_before(act)) {
2159 future_ordered = true;
2163 /* Only non-RMW writes can break release sequences */
2164 if (!act->is_write() || act->is_rmw())
2167 /* Check modification order */
2168 if (mo_graph->checkReachable(rf, act)) {
2169 /* rf --mo--> act */
2170 future_ordered = true;
2173 if (mo_graph->checkReachable(act, release))
2174 /* act --mo--> release */
2176 if (mo_graph->checkReachable(release, act) &&
2177 mo_graph->checkReachable(act, rf)) {
2178 /* release --mo-> act --mo--> rf */
2179 return true; /* complete */
2181 /* act may break release sequence */
2182 pending->writes.push_back(act);
2185 if (!future_ordered)
2186 certain = false; /* This thread is uncertain */
2190 release_heads->push_back(release);
2191 pending->writes.clear();
2193 pending->release = release;
2200 * An interface for getting the release sequence head(s) with which a
2201 * given ModelAction must synchronize. This function only returns a non-empty
2202 * result when it can locate a release sequence head with certainty. Otherwise,
2203 * it may mark the internal state of the ModelChecker so that it will handle
2204 * the release sequence at a later time, causing @a acquire to update its
2205 * synchronization at some later point in execution.
2207 * @param acquire The 'acquire' action that may synchronize with a release
2209 * @param read The read action that may read from a release sequence; this may
2210 * be the same as acquire, or else an earlier action in the same thread (i.e.,
2211 * when 'acquire' is a fence-acquire)
2212 * @param release_heads A pass-by-reference return parameter. Will be filled
2213 * with the head(s) of the release sequence(s), if they exists with certainty.
2214 * @see ModelChecker::release_seq_heads
2216 void ModelChecker::get_release_seq_heads(ModelAction *acquire,
2217 ModelAction *read, rel_heads_list_t *release_heads)
2219 const ModelAction *rf = read->get_reads_from();
2220 struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
2221 sequence->acquire = acquire;
2222 sequence->read = read;
2224 if (!release_seq_heads(rf, release_heads, sequence)) {
2225 /* add act to 'lazy checking' list */
2226 pending_rel_seqs->push_back(sequence);
2228 snapshot_free(sequence);
2233 * Attempt to resolve all stashed operations that might synchronize with a
2234 * release sequence for a given location. This implements the "lazy" portion of
2235 * determining whether or not a release sequence was contiguous, since not all
2236 * modification order information is present at the time an action occurs.
2238 * @param location The location/object that should be checked for release
2239 * sequence resolutions. A NULL value means to check all locations.
2240 * @param work_queue The work queue to which to add work items as they are
2242 * @return True if any updates occurred (new synchronization, new mo_graph
2245 bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
2247 bool updated = false;
2248 std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
2249 while (it != pending_rel_seqs->end()) {
2250 struct release_seq *pending = *it;
2251 ModelAction *acquire = pending->acquire;
2252 const ModelAction *read = pending->read;
2254 /* Only resolve sequences on the given location, if provided */
2255 if (location && read->get_location() != location) {
2260 const ModelAction *rf = read->get_reads_from();
2261 rel_heads_list_t release_heads;
2263 complete = release_seq_heads(rf, &release_heads, pending);
2264 for (unsigned int i = 0; i < release_heads.size(); i++) {
2265 if (!acquire->has_synchronized_with(release_heads[i])) {
2266 if (acquire->synchronize_with(release_heads[i]))
2269 set_bad_synchronization();
2274 /* Re-check all pending release sequences */
2275 work_queue->push_back(CheckRelSeqWorkEntry(NULL));
2276 /* Re-check read-acquire for mo_graph edges */
2277 if (acquire->is_read())
2278 work_queue->push_back(MOEdgeWorkEntry(acquire));
2280 /* propagate synchronization to later actions */
2281 action_list_t::reverse_iterator rit = action_trace->rbegin();
2282 for (; (*rit) != acquire; rit++) {
2283 ModelAction *propagate = *rit;
2284 if (acquire->happens_before(propagate)) {
2285 propagate->synchronize_with(acquire);
2286 /* Re-check 'propagate' for mo_graph edges */
2287 work_queue->push_back(MOEdgeWorkEntry(propagate));
2292 it = pending_rel_seqs->erase(it);
2293 snapshot_free(pending);
2299 // If we resolved promises or data races, see if we have realized a data race.
2306 * Performs various bookkeeping operations for the current ModelAction. For
2307 * instance, adds action to the per-object, per-thread action vector and to the
2308 * action trace list of all thread actions.
2310 * @param act is the ModelAction to add.
2312 void ModelChecker::add_action_to_lists(ModelAction *act)
2314 int tid = id_to_int(act->get_tid());
2315 ModelAction *uninit = NULL;
2317 action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
2318 if (list->empty() && act->is_atomic_var()) {
2319 uninit = new_uninitialized_action(act->get_location());
2320 uninit_id = id_to_int(uninit->get_tid());
2321 list->push_back(uninit);
2323 list->push_back(act);
2325 action_trace->push_back(act);
2327 action_trace->push_front(uninit);
2329 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
2330 if (tid >= (int)vec->size())
2331 vec->resize(priv->next_thread_id);
2332 (*vec)[tid].push_back(act);
2334 (*vec)[uninit_id].push_front(uninit);
2336 if ((int)thrd_last_action->size() <= tid)
2337 thrd_last_action->resize(get_num_threads());
2338 (*thrd_last_action)[tid] = act;
2340 (*thrd_last_action)[uninit_id] = uninit;
2342 if (act->is_fence() && act->is_release()) {
2343 if ((int)thrd_last_fence_release->size() <= tid)
2344 thrd_last_fence_release->resize(get_num_threads());
2345 (*thrd_last_fence_release)[tid] = act;
2348 if (act->is_wait()) {
2349 void *mutex_loc = (void *) act->get_value();
2350 get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
2352 std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
2353 if (tid >= (int)vec->size())
2354 vec->resize(priv->next_thread_id);
2355 (*vec)[tid].push_back(act);
2360 * @brief Get the last action performed by a particular Thread
2361 * @param tid The thread ID of the Thread in question
2362 * @return The last action in the thread
2364 ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
2366 int threadid = id_to_int(tid);
2367 if (threadid < (int)thrd_last_action->size())
2368 return (*thrd_last_action)[id_to_int(tid)];
2374 * @brief Get the last fence release performed by a particular Thread
2375 * @param tid The thread ID of the Thread in question
2376 * @return The last fence release in the thread, if one exists; NULL otherwise
2378 ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
2380 int threadid = id_to_int(tid);
2381 if (threadid < (int)thrd_last_fence_release->size())
2382 return (*thrd_last_fence_release)[id_to_int(tid)];
2388 * Gets the last memory_order_seq_cst write (in the total global sequence)
2389 * performed on a particular object (i.e., memory location), not including the
2391 * @param curr The current ModelAction; also denotes the object location to
2393 * @return The last seq_cst write
2395 ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
2397 void *location = curr->get_location();
2398 action_list_t *list = get_safe_ptr_action(obj_map, location);
2399 /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
2400 action_list_t::reverse_iterator rit;
2401 for (rit = list->rbegin(); rit != list->rend(); rit++)
2402 if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
2408 * Gets the last memory_order_seq_cst fence (in the total global sequence)
2409 * performed in a particular thread, prior to a particular fence.
2410 * @param tid The ID of the thread to check
2411 * @param before_fence The fence from which to begin the search; if NULL, then
2412 * search for the most recent fence in the thread.
2413 * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
2415 ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
2417 /* All fences should have NULL location */
2418 action_list_t *list = get_safe_ptr_action(obj_map, NULL);
2419 action_list_t::reverse_iterator rit = list->rbegin();
2422 for (; rit != list->rend(); rit++)
2423 if (*rit == before_fence)
2426 ASSERT(*rit == before_fence);
2430 for (; rit != list->rend(); rit++)
2431 if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
2437 * Gets the last unlock operation performed on a particular mutex (i.e., memory
2438 * location). This function identifies the mutex according to the current
2439 * action, which is presumed to perform on the same mutex.
2440 * @param curr The current ModelAction; also denotes the object location to
2442 * @return The last unlock operation
2444 ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
2446 void *location = curr->get_location();
2447 action_list_t *list = get_safe_ptr_action(obj_map, location);
2448 /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
2449 action_list_t::reverse_iterator rit;
2450 for (rit = list->rbegin(); rit != list->rend(); rit++)
2451 if ((*rit)->is_unlock() || (*rit)->is_wait())
2456 ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
2458 ModelAction *parent = get_last_action(tid);
2460 parent = get_thread(tid)->get_creation();
2465 * Returns the clock vector for a given thread.
2466 * @param tid The thread whose clock vector we want
2467 * @return Desired clock vector
2469 ClockVector * ModelChecker::get_cv(thread_id_t tid) const
2471 return get_parent_action(tid)->get_cv();
2475 * @brief Find the promise, if any to resolve for the current action
2476 * @param curr The current ModelAction. Should be a write.
2477 * @return The (non-negative) index for the Promise to resolve, if any;
2480 int ModelChecker::get_promise_to_resolve(const ModelAction *curr) const
2482 for (unsigned int i = 0; i < promises->size(); i++)
2483 if (curr->get_node()->get_promise(i))
2489 * Resolve a Promise with a current write.
2490 * @param write The ModelAction that is fulfilling Promises
2491 * @param promise_idx The index corresponding to the promise
2492 * @return True if the Promise was successfully resolved; false otherwise
2494 bool ModelChecker::resolve_promise(ModelAction *write, unsigned int promise_idx)
2496 std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
2497 promise_list_t mustResolve;
2498 Promise *promise = (*promises)[promise_idx];
2500 for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
2501 ModelAction *read = promise->get_reader(i);
2502 read_from(read, write);
2503 actions_to_check.push_back(read);
2505 /* Make sure the promise's value matches the write's value */
2506 ASSERT(promise->is_compatible(write) && promise->same_value(write));
2507 mo_graph->resolvePromise(promise, write, &mustResolve);
2509 promises->erase(promises->begin() + promise_idx);
2511 /** @todo simplify the 'mustResolve' stuff */
2512 ASSERT(mustResolve.size() <= 1);
2514 if (!mustResolve.empty() && mustResolve[0] != promise)
2515 priv->failed_promise = true;
2518 //Check whether reading these writes has made threads unable to
2521 for (unsigned int i = 0; i < actions_to_check.size(); i++) {
2522 ModelAction *read = actions_to_check[i];
2523 mo_check_promises(read, true);
2530 * Compute the set of promises that could potentially be satisfied by this
2531 * action. Note that the set computation actually appears in the Node, not in
2533 * @param curr The ModelAction that may satisfy promises
2535 void ModelChecker::compute_promises(ModelAction *curr)
2537 for (unsigned int i = 0; i < promises->size(); i++) {
2538 Promise *promise = (*promises)[i];
2539 if (!promise->is_compatible(curr) || !promise->same_value(curr))
2542 bool satisfy = true;
2543 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2544 const ModelAction *act = promise->get_reader(j);
2545 if (act->happens_before(curr) ||
2546 act->could_synchronize_with(curr)) {
2552 curr->get_node()->set_promise(i);
2556 /** Checks promises in response to change in ClockVector Threads. */
2557 void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
2559 for (unsigned int i = 0; i < promises->size(); i++) {
2560 Promise *promise = (*promises)[i];
2561 if (!promise->thread_is_available(tid))
2563 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2564 const ModelAction *act = promise->get_reader(j);
2565 if ((!old_cv || !old_cv->synchronized_since(act)) &&
2566 merge_cv->synchronized_since(act)) {
2567 if (promise->eliminate_thread(tid)) {
2568 /* Promise has failed */
2569 priv->failed_promise = true;
2577 void ModelChecker::check_promises_thread_disabled()
2579 for (unsigned int i = 0; i < promises->size(); i++) {
2580 Promise *promise = (*promises)[i];
2581 if (promise->has_failed()) {
2582 priv->failed_promise = true;
2589 * @brief Checks promises in response to addition to modification order for
2592 * We test whether threads are still available for satisfying promises after an
2593 * addition to our modification order constraints. Those that are unavailable
2594 * are "eliminated". Once all threads are eliminated from satisfying a promise,
2595 * that promise has failed.
2597 * @param act The ModelAction which updated the modification order
2598 * @param is_read_check Should be true if act is a read and we must check for
2599 * updates to the store from which it read (there is a distinction here for
2600 * RMW's, which are both a load and a store)
2602 void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
2604 const ModelAction *write = is_read_check ? act->get_reads_from() : act;
2606 for (unsigned int i = 0; i < promises->size(); i++) {
2607 Promise *promise = (*promises)[i];
2609 // Is this promise on the same location?
2610 if (!promise->same_location(write))
2613 for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
2614 const ModelAction *pread = promise->get_reader(j);
2615 if (!pread->happens_before(act))
2617 if (mo_graph->checkPromise(write, promise)) {
2618 priv->failed_promise = true;
2624 // Don't do any lookups twice for the same thread
2625 if (!promise->thread_is_available(act->get_tid()))
2628 if (mo_graph->checkReachable(promise, write)) {
2629 if (mo_graph->checkPromise(write, promise)) {
2630 priv->failed_promise = true;
2638 * Compute the set of writes that may break the current pending release
2639 * sequence. This information is extracted from previou release sequence
2642 * @param curr The current ModelAction. Must be a release sequence fixup
2645 void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
2647 if (pending_rel_seqs->empty())
2650 struct release_seq *pending = pending_rel_seqs->back();
2651 for (unsigned int i = 0; i < pending->writes.size(); i++) {
2652 const ModelAction *write = pending->writes[i];
2653 curr->get_node()->add_relseq_break(write);
2656 /* NULL means don't break the sequence; just synchronize */
2657 curr->get_node()->add_relseq_break(NULL);
2661 * Build up an initial set of all past writes that this 'read' action may read
2662 * from, as well as any previously-observed future values that must still be valid.
2664 * @param curr is the current ModelAction that we are exploring; it must be a
2667 void ModelChecker::build_may_read_from(ModelAction *curr)
2669 std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
2671 ASSERT(curr->is_read());
2673 ModelAction *last_sc_write = NULL;
2675 if (curr->is_seqcst())
2676 last_sc_write = get_last_seq_cst_write(curr);
2678 /* Iterate over all threads */
2679 for (i = 0; i < thrd_lists->size(); i++) {
2680 /* Iterate over actions in thread, starting from most recent */
2681 action_list_t *list = &(*thrd_lists)[i];
2682 action_list_t::reverse_iterator rit;
2683 for (rit = list->rbegin(); rit != list->rend(); rit++) {
2684 ModelAction *act = *rit;
2686 /* Only consider 'write' actions */
2687 if (!act->is_write() || act == curr)
2690 /* Don't consider more than one seq_cst write if we are a seq_cst read. */
2691 bool allow_read = true;
2693 if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
2695 else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
2699 /* Only add feasible reads */
2700 mo_graph->startChanges();
2701 r_modification_order(curr, act);
2702 if (!is_infeasible())
2703 curr->get_node()->add_read_from_past(act);
2704 mo_graph->rollbackChanges();
2707 /* Include at most one act per-thread that "happens before" curr */
2708 if (act->happens_before(curr))
2713 /* Inherit existing, promised future values */
2714 for (i = 0; i < promises->size(); i++) {
2715 const Promise *promise = (*promises)[i];
2716 const ModelAction *promise_read = promise->get_reader(0);
2717 if (promise_read->same_var(curr)) {
2718 /* Only add feasible future-values */
2719 mo_graph->startChanges();
2720 r_modification_order(curr, promise);
2721 if (!is_infeasible())
2722 curr->get_node()->add_read_from_promise(promise_read);
2723 mo_graph->rollbackChanges();
2727 /* We may find no valid may-read-from only if the execution is doomed */
2728 if (!curr->get_node()->read_from_size()) {
2729 priv->no_valid_reads = true;
2733 if (DBG_ENABLED()) {
2734 model_print("Reached read action:\n");
2736 model_print("Printing read_from_past\n");
2737 curr->get_node()->print_read_from_past();
2738 model_print("End printing read_from_past\n");
2742 bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
2744 for ( ; write != NULL; write = write->get_reads_from()) {
2745 /* UNINIT actions don't have a Node, and they never sleep */
2746 if (write->is_uninitialized())
2748 Node *prevnode = write->get_node()->get_parent();
2750 bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
2751 if (write->is_release() && thread_sleep)
2753 if (!write->is_rmw())
2760 * @brief Create a new action representing an uninitialized atomic
2761 * @param location The memory location of the atomic object
2762 * @return A pointer to a new ModelAction
2764 ModelAction * ModelChecker::new_uninitialized_action(void *location) const
2766 ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
2767 act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
2768 act->create_cv(NULL);
2772 static void print_list(action_list_t *list)
2774 action_list_t::iterator it;
2776 model_print("---------------------------------------------------------------------\n");
2778 unsigned int hash = 0;
2780 for (it = list->begin(); it != list->end(); it++) {
2782 hash = hash^(hash<<3)^((*it)->hash());
2784 model_print("HASH %u\n", hash);
2785 model_print("---------------------------------------------------------------------\n");
2788 #if SUPPORT_MOD_ORDER_DUMP
2789 void ModelChecker::dumpGraph(char *filename) const
2792 sprintf(buffer, "%s.dot", filename);
2793 FILE *file = fopen(buffer, "w");
2794 fprintf(file, "digraph %s {\n", filename);
2795 mo_graph->dumpNodes(file);
2796 ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
2798 for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
2799 ModelAction *act = *it;
2800 if (act->is_read()) {
2801 mo_graph->dot_print_node(file, act);
2802 if (act->get_reads_from())
2803 mo_graph->dot_print_edge(file,
2804 act->get_reads_from(),
2806 "label=\"rf\", color=red, weight=2");
2808 mo_graph->dot_print_edge(file,
2809 act->get_reads_from_promise(),
2811 "label=\"rf\", color=red");
2813 if (thread_array[act->get_tid()]) {
2814 mo_graph->dot_print_edge(file,
2815 thread_array[id_to_int(act->get_tid())],
2817 "label=\"sb\", color=blue, weight=400");
2820 thread_array[act->get_tid()] = act;
2822 fprintf(file, "}\n");
2823 model_free(thread_array);
2828 /** @brief Prints an execution trace summary. */
2829 void ModelChecker::print_summary() const
2831 #if SUPPORT_MOD_ORDER_DUMP
2832 char buffername[100];
2833 sprintf(buffername, "exec%04u", stats.num_total);
2834 mo_graph->dumpGraphToFile(buffername);
2835 sprintf(buffername, "graph%04u", stats.num_total);
2836 dumpGraph(buffername);
2839 model_print("Execution %d:", stats.num_total);
2840 if (isfeasibleprefix()) {
2841 if (scheduler->all_threads_sleeping())
2842 model_print(" SLEEP-SET REDUNDANT");
2845 print_infeasibility(" INFEASIBLE");
2846 print_list(action_trace);
2851 * Add a Thread to the system for the first time. Should only be called once
2853 * @param t The Thread to add
2855 void ModelChecker::add_thread(Thread *t)
2857 thread_map->put(id_to_int(t->get_id()), t);
2858 scheduler->add_thread(t);
2862 * Removes a thread from the scheduler.
2863 * @param the thread to remove.
2865 void ModelChecker::remove_thread(Thread *t)
2867 scheduler->remove_thread(t);
2871 * @brief Get a Thread reference by its ID
2872 * @param tid The Thread's ID
2873 * @return A Thread reference
2875 Thread * ModelChecker::get_thread(thread_id_t tid) const
2877 return thread_map->get(id_to_int(tid));
2881 * @brief Get a reference to the Thread in which a ModelAction was executed
2882 * @param act The ModelAction
2883 * @return A Thread reference
2885 Thread * ModelChecker::get_thread(const ModelAction *act) const
2887 return get_thread(act->get_tid());
2891 * @brief Get a Promise's "promise number"
2893 * A "promise number" is an index number that is unique to a promise, valid
2894 * only for a specific snapshot of an execution trace. Promises may come and go
2895 * as they are generated an resolved, so an index only retains meaning for the
2898 * @param promise The Promise to check
2899 * @return The promise index, if the promise still is valid; otherwise -1
2901 int ModelChecker::get_promise_number(const Promise *promise) const
2903 for (unsigned int i = 0; i < promises->size(); i++)
2904 if ((*promises)[i] == promise)
2911 * @brief Check if a Thread is currently enabled
2912 * @param t The Thread to check
2913 * @return True if the Thread is currently enabled
2915 bool ModelChecker::is_enabled(Thread *t) const
2917 return scheduler->is_enabled(t);
2921 * @brief Check if a Thread is currently enabled
2922 * @param tid The ID of the Thread to check
2923 * @return True if the Thread is currently enabled
2925 bool ModelChecker::is_enabled(thread_id_t tid) const
2927 return scheduler->is_enabled(tid);
2931 * Switch from a model-checker context to a user-thread context. This is the
2932 * complement of ModelChecker::switch_to_master and must be called from the
2933 * model-checker context
2935 * @param thread The user-thread to switch to
2937 void ModelChecker::switch_from_master(Thread *thread)
2939 scheduler->set_current_thread(thread);
2940 Thread::swap(&system_context, thread);
2944 * Switch from a user-context to the "master thread" context (a.k.a. system
2945 * context). This switch is made with the intention of exploring a particular
2946 * model-checking action (described by a ModelAction object). Must be called
2947 * from a user-thread context.
2949 * @param act The current action that will be explored. May be NULL only if
2950 * trace is exiting via an assertion (see ModelChecker::set_assert and
2951 * ModelChecker::has_asserted).
2952 * @return Return the value returned by the current action
2954 uint64_t ModelChecker::switch_to_master(ModelAction *act)
2957 Thread *old = thread_current();
2958 ASSERT(!old->get_pending());
2959 old->set_pending(act);
2960 if (Thread::swap(old, &system_context) < 0) {
2961 perror("swap threads");
2964 return old->get_return_value();
2968 * Takes the next step in the execution, if possible.
2969 * @param curr The current step to take
2970 * @return Returns the next Thread to run, if any; NULL if this execution
2973 Thread * ModelChecker::take_step(ModelAction *curr)
2975 Thread *curr_thrd = get_thread(curr);
2976 ASSERT(curr_thrd->get_state() == THREAD_READY);
2978 curr = check_current_action(curr);
2980 /* Infeasible -> don't take any more steps */
2981 if (is_infeasible())
2983 else if (isfeasibleprefix() && have_bug_reports()) {
2988 if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
2991 if (curr_thrd->is_blocked() || curr_thrd->is_complete())
2992 scheduler->remove_thread(curr_thrd);
2994 Thread *next_thrd = get_next_thread(curr);
2996 DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
2997 next_thrd ? id_to_int(next_thrd->get_id()) : -1);
3002 /** Wrapper to run the user's main function, with appropriate arguments */
3003 void user_main_wrapper(void *)
3005 user_main(model->params.argc, model->params.argv);
3008 /** @brief Run ModelChecker for the user program */
3009 void ModelChecker::run()
3013 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
3018 * Stash next pending action(s) for thread(s). There
3019 * should only need to stash one thread's action--the
3020 * thread which just took a step--plus the first step
3021 * for any newly-created thread
3023 for (unsigned int i = 0; i < get_num_threads(); i++) {
3024 thread_id_t tid = int_to_id(i);
3025 Thread *thr = get_thread(tid);
3026 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
3027 switch_from_master(thr);
3031 /* Catch assertions from prior take_step or from
3032 * between-ModelAction bugs (e.g., data races) */
3036 /* Consume the next action for a Thread */
3037 ModelAction *curr = t->get_pending();
3038 t->set_pending(NULL);
3039 t = take_step(curr);
3040 } while (t && !t->is_model_thread());
3043 * Launch end-of-execution release sequence fixups only when
3044 * the execution is otherwise feasible AND there are:
3046 * (1) pending release sequences
3047 * (2) pending assertions that could be invalidated by a change
3048 * in clock vectors (i.e., data races)
3049 * (3) no pending promises
3051 while (!pending_rel_seqs->empty() &&
3052 is_feasible_prefix_ignore_relseq() &&
3053 !unrealizedraces.empty()) {
3054 model_print("*** WARNING: release sequence fixup action "
3055 "(%zu pending release seuqence(s)) ***\n",
3056 pending_rel_seqs->size());
3057 ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
3058 std::memory_order_seq_cst, NULL, VALUE_NONE,
3062 } while (next_execution());
3064 model_print("******* Model-checking complete: *******\n");