- switch (curr->get_type()) {
- case THREAD_CREATE: {
- thrd_t *thrd = (thrd_t *)curr->get_location();
- struct thread_params *params = (struct thread_params *)curr->get_value();
- Thread *th = new Thread(thrd, params->func, params->arg);
- add_thread(th);
- th->set_creation(curr);
- /* Promises can be satisfied by children */
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->thread_is_available(curr->get_tid()))
- promise->add_thread(th->get_id());
- }
- break;
- }
- case THREAD_JOIN: {
- Thread *blocking = curr->get_thread_operand();
- ModelAction *act = get_last_action(blocking->get_id());
- curr->synchronize_with(act);
- updated = true; /* trigger rel-seq checks */
- break;
- }
- case THREAD_FINISH: {
- Thread *th = get_thread(curr);
- while (!th->wait_list_empty()) {
- ModelAction *act = th->pop_wait_list();
- scheduler->wake(get_thread(act));
- }
- th->complete();
- /* Completed thread can't satisfy promises */
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->thread_is_available(th->get_id()))
- if (promise->eliminate_thread(th->get_id()))
- priv->failed_promise = true;
- }
- updated = true; /* trigger rel-seq checks */
- break;
- }
- case THREAD_START: {
- check_promises(curr->get_tid(), NULL, curr->get_cv());
- break;
- }
- default:
- break;
- }
-
- return updated;
-}
-
-/**
- * @brief Process the current action for release sequence fixup activity
- *
- * Performs model-checker release sequence fixups for the current action,
- * forcing a single pending release sequence to break (with a given, potential
- * "loose" write) or to complete (i.e., synchronize). If a pending release
- * sequence forms a complete release sequence, then we must perform the fixup
- * synchronization, mo_graph additions, etc.
- *
- * @param curr The current action; must be a release sequence fixup action
- * @param work_queue The work queue to which to add work items as they are
- * generated
- */
-void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
-{
- const ModelAction *write = curr->get_node()->get_relseq_break();
- struct release_seq *sequence = pending_rel_seqs->back();
- pending_rel_seqs->pop_back();
- ASSERT(sequence);
- ModelAction *acquire = sequence->acquire;
- const ModelAction *rf = sequence->rf;
- const ModelAction *release = sequence->release;
- ASSERT(acquire);
- ASSERT(release);
- ASSERT(rf);
- ASSERT(release->same_thread(rf));
-
- if (write == NULL) {
- /**
- * @todo Forcing a synchronization requires that we set
- * modification order constraints. For instance, we can't allow
- * a fixup sequence in which two separate read-acquire
- * operations read from the same sequence, where the first one
- * synchronizes and the other doesn't. Essentially, we can't
- * allow any writes to insert themselves between 'release' and
- * 'rf'
- */
-
- /* Must synchronize */
- if (!acquire->synchronize_with(release)) {
- set_bad_synchronization();
- return;
- }
- /* Re-check all pending release sequences */
- work_queue->push_back(CheckRelSeqWorkEntry(NULL));
- /* Re-check act for mo_graph edges */
- work_queue->push_back(MOEdgeWorkEntry(acquire));
-
- /* propagate synchronization to later actions */
- action_list_t::reverse_iterator rit = action_trace->rbegin();
- for (; (*rit) != acquire; rit++) {
- ModelAction *propagate = *rit;
- if (acquire->happens_before(propagate)) {
- propagate->synchronize_with(acquire);
- /* Re-check 'propagate' for mo_graph edges */
- work_queue->push_back(MOEdgeWorkEntry(propagate));
- }
- }
- } else {
- /* Break release sequence with new edges:
- * release --mo--> write --mo--> rf */
- mo_graph->addEdge(release, write);
- mo_graph->addEdge(write, rf);
- }
-
- /* See if we have realized a data race */
- checkDataRaces();
-}
-
-/**
- * Initialize the current action by performing one or more of the following
- * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
- * in the NodeStack, manipulating backtracking sets, allocating and
- * initializing clock vectors, and computing the promises to fulfill.
- *
- * @param curr The current action, as passed from the user context; may be
- * freed/invalidated after the execution of this function, with a different
- * action "returned" its place (pass-by-reference)
- * @return True if curr is a newly-explored action; false otherwise
- */
-bool ModelChecker::initialize_curr_action(ModelAction **curr)
-{
- ModelAction *newcurr;
-
- if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
- newcurr = process_rmw(*curr);
- delete *curr;
-
- if (newcurr->is_rmw())
- compute_promises(newcurr);
-
- *curr = newcurr;
- return false;
- }
-
- (*curr)->set_seq_number(get_next_seq_num());
-
- newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
- if (newcurr) {
- /* First restore type and order in case of RMW operation */
- if ((*curr)->is_rmwr())
- newcurr->copy_typeandorder(*curr);
-
- ASSERT((*curr)->get_location() == newcurr->get_location());
- newcurr->copy_from_new(*curr);
-
- /* Discard duplicate ModelAction; use action from NodeStack */
- delete *curr;
-
- /* Always compute new clock vector */
- newcurr->create_cv(get_parent_action(newcurr->get_tid()));
-
- *curr = newcurr;
- return false; /* Action was explored previously */
- } else {
- newcurr = *curr;
-
- /* Always compute new clock vector */
- newcurr->create_cv(get_parent_action(newcurr->get_tid()));
-
- /* Assign most recent release fence */
- newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
-
- /*
- * Perform one-time actions when pushing new ModelAction onto
- * NodeStack
- */
- if (newcurr->is_write())
- compute_promises(newcurr);
- else if (newcurr->is_relseq_fixup())
- compute_relseq_breakwrites(newcurr);
- else if (newcurr->is_wait())
- newcurr->get_node()->set_misc_max(2);
- else if (newcurr->is_notify_one()) {
- newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
- }
- return true; /* This was a new ModelAction */
- }
-}
-
-/**
- * @brief Establish reads-from relation between two actions
- *
- * Perform basic operations involved with establishing a concrete rf relation,
- * including setting the ModelAction data and checking for release sequences.
- *
- * @param act The action that is reading (must be a read)
- * @param rf The action from which we are reading (must be a write)
- *
- * @return True if this read established synchronization
- */
-bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
-{
- act->set_read_from(rf);
- if (rf != NULL && act->is_acquire()) {
- rel_heads_list_t release_heads;
- get_release_seq_heads(act, act, &release_heads);
- int num_heads = release_heads.size();
- for (unsigned int i = 0; i < release_heads.size(); i++)
- if (!act->synchronize_with(release_heads[i])) {
- set_bad_synchronization();
- num_heads--;
- }
- return num_heads > 0;
- }
- return false;
-}
-
-/**
- * @brief Check whether a model action is enabled.
- *
- * Checks whether a lock or join operation would be successful (i.e., is the
- * lock already locked, or is the joined thread already complete). If not, put
- * the action in a waiter list.
- *
- * @param curr is the ModelAction to check whether it is enabled.
- * @return a bool that indicates whether the action is enabled.
- */
-bool ModelChecker::check_action_enabled(ModelAction *curr) {
- if (curr->is_lock()) {
- std::mutex *lock = (std::mutex *)curr->get_location();
- struct std::mutex_state *state = lock->get_state();
- if (state->islocked) {
- //Stick the action in the appropriate waiting queue
- get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
- return false;
- }
- } else if (curr->get_type() == THREAD_JOIN) {
- Thread *blocking = (Thread *)curr->get_location();
- if (!blocking->is_complete()) {
- blocking->push_wait_list(curr);
- return false;
- }
- }
-
- return true;
-}
-
-/**
- * This is the heart of the model checker routine. It performs model-checking
- * actions corresponding to a given "current action." Among other processes, it
- * calculates reads-from relationships, updates synchronization clock vectors,
- * forms a memory_order constraints graph, and handles replay/backtrack
- * execution when running permutations of previously-observed executions.
- *
- * @param curr The current action to process
- * @return The ModelAction that is actually executed; may be different than
- * curr; may be NULL, if the current action is not enabled to run
- */
-ModelAction * ModelChecker::check_current_action(ModelAction *curr)
-{
- ASSERT(curr);
- bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
-
- if (!check_action_enabled(curr)) {
- /* Make the execution look like we chose to run this action
- * much later, when a lock/join can succeed */
- get_thread(curr)->set_pending(curr);
- scheduler->sleep(get_thread(curr));
- return NULL;
- }
-
- bool newly_explored = initialize_curr_action(&curr);
-
- DBG();
- if (DBG_ENABLED())
- curr->print();
-
- wake_up_sleeping_actions(curr);
-
- /* Add the action to lists before any other model-checking tasks */
- if (!second_part_of_rmw)
- add_action_to_lists(curr);
-
- /* Build may_read_from set for newly-created actions */
- if (newly_explored && curr->is_read())
- build_reads_from_past(curr);
-
- /* Initialize work_queue with the "current action" work */
- work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
- while (!work_queue.empty() && !has_asserted()) {
- WorkQueueEntry work = work_queue.front();
- work_queue.pop_front();
-
- switch (work.type) {
- case WORK_CHECK_CURR_ACTION: {
- ModelAction *act = work.action;
- bool update = false; /* update this location's release seq's */
- bool update_all = false; /* update all release seq's */
-
- if (process_thread_action(curr))
- update_all = true;
-
- if (act->is_read() && process_read(act, second_part_of_rmw))
- update = true;
-
- if (act->is_write() && process_write(act))
- update = true;
-
- if (act->is_fence() && process_fence(act))
- update_all = true;
-
- if (act->is_mutex_op() && process_mutex(act))
- update_all = true;
-
- if (act->is_relseq_fixup())
- process_relseq_fixup(curr, &work_queue);
-
- if (update_all)
- work_queue.push_back(CheckRelSeqWorkEntry(NULL));
- else if (update)
- work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
- break;
- }
- case WORK_CHECK_RELEASE_SEQ:
- resolve_release_sequences(work.location, &work_queue);
- break;
- case WORK_CHECK_MO_EDGES: {
- /** @todo Complete verification of work_queue */
- ModelAction *act = work.action;
- bool updated = false;
-
- if (act->is_read()) {
- const ModelAction *rf = act->get_reads_from();
- const Promise *promise = act->get_reads_from_promise();
- if (rf) {
- if (r_modification_order(act, rf))
- updated = true;
- } else if (promise) {
- if (r_modification_order(act, promise))
- updated = true;
- }
- }
- if (act->is_write()) {
- if (w_modification_order(act))
- updated = true;
- }
- mo_graph->commitChanges();
-
- if (updated)
- work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
- break;
- }
- default:
- ASSERT(false);
- break;
- }
- }
-
- check_curr_backtracking(curr);
- set_backtracking(curr);
- return curr;
-}
-
-void ModelChecker::check_curr_backtracking(ModelAction *curr)
-{
- Node *currnode = curr->get_node();
- Node *parnode = currnode->get_parent();
-
- if ((parnode && !parnode->backtrack_empty()) ||
- !currnode->misc_empty() ||
- !currnode->read_from_empty() ||
- !currnode->future_value_empty() ||
- !currnode->promise_empty() ||
- !currnode->relseq_break_empty()) {
- set_latest_backtrack(curr);
- }
-}
-
-bool ModelChecker::promises_expired() const
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->get_expiration() < priv->used_sequence_numbers)
- return true;
- }
- return false;
-}
-
-/**
- * This is the strongest feasibility check available.
- * @return whether the current trace (partial or complete) must be a prefix of
- * a feasible trace.
- */
-bool ModelChecker::isfeasibleprefix() const
-{
- return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
-}
-
-/**
- * Print disagnostic information about an infeasible execution
- * @param prefix A string to prefix the output with; if NULL, then a default
- * message prefix will be provided
- */
-void ModelChecker::print_infeasibility(const char *prefix) const
-{
- char buf[100];
- char *ptr = buf;
- if (mo_graph->checkForCycles())
- ptr += sprintf(ptr, "[mo cycle]");
- if (priv->failed_promise)
- ptr += sprintf(ptr, "[failed promise]");
- if (priv->too_many_reads)
- ptr += sprintf(ptr, "[too many reads]");
- if (priv->no_valid_reads)
- ptr += sprintf(ptr, "[no valid reads-from]");
- if (priv->bad_synchronization)
- ptr += sprintf(ptr, "[bad sw ordering]");
- if (promises_expired())
- ptr += sprintf(ptr, "[promise expired]");
- if (promises->size() != 0)
- ptr += sprintf(ptr, "[unresolved promise]");
- if (ptr != buf)
- model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
-}
-
-/**
- * Returns whether the current completed trace is feasible, except for pending
- * release sequences.
- */
-bool ModelChecker::is_feasible_prefix_ignore_relseq() const
-{
- return !is_infeasible() && promises->size() == 0;
-}
-
-/**
- * Check if the current partial trace is infeasible. Does not check any
- * end-of-execution flags, which might rule out the execution. Thus, this is
- * useful only for ruling an execution as infeasible.
- * @return whether the current partial trace is infeasible.
- */
-bool ModelChecker::is_infeasible() const
-{
- return mo_graph->checkForCycles() ||
- priv->no_valid_reads ||
- priv->failed_promise ||
- priv->too_many_reads ||
- priv->bad_synchronization ||
- promises_expired();
-}
-
-/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
-ModelAction * ModelChecker::process_rmw(ModelAction *act) {
- ModelAction *lastread = get_last_action(act->get_tid());
- lastread->process_rmw(act);
- if (act->is_rmw()) {
- if (lastread->get_reads_from())
- mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
- else
- mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
- mo_graph->commitChanges();
- }
- return lastread;
-}
-
-/**
- * Checks whether a thread has read from the same write for too many times
- * without seeing the effects of a later write.
- *
- * Basic idea:
- * 1) there must a different write that we could read from that would satisfy the modification order,
- * 2) we must have read from the same value in excess of maxreads times, and
- * 3) that other write must have been in the reads_from set for maxreads times.
- *
- * If so, we decide that the execution is no longer feasible.
- */
-void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
-{
- if (params.maxreads != 0) {
- if (curr->get_node()->get_read_from_size() <= 1)
- return;
- //Must make sure that execution is currently feasible... We could
- //accidentally clear by rolling back
- if (is_infeasible())
- return;
- std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- int tid = id_to_int(curr->get_tid());
-
- /* Skip checks */
- if ((int)thrd_lists->size() <= tid)
- return;
- action_list_t *list = &(*thrd_lists)[tid];
-
- action_list_t::reverse_iterator rit = list->rbegin();
- /* Skip past curr */
- for (; (*rit) != curr; rit++)
- ;
- /* go past curr now */
- rit++;
-
- action_list_t::reverse_iterator ritcopy = rit;
- //See if we have enough reads from the same value
- int count = 0;
- for (; count < params.maxreads; rit++, count++) {
- if (rit == list->rend())
- return;
- ModelAction *act = *rit;
- if (!act->is_read())
- return;
-
- if (act->get_reads_from() != rf)
- return;
- if (act->get_node()->get_read_from_size() <= 1)
- return;
- }
- for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
- /* Get write */
- const ModelAction *write = curr->get_node()->get_read_from_at(i);
-
- /* Need a different write */
- if (write == rf)
- continue;
-
- /* Test to see whether this is a feasible write to read from */
- /** NOTE: all members of read-from set should be
- * feasible, so we no longer check it here **/
-
- rit = ritcopy;
-
- bool feasiblewrite = true;
- //new we need to see if this write works for everyone
-
- for (int loop = count; loop > 0; loop--, rit++) {
- ModelAction *act = *rit;
- bool foundvalue = false;
- for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
- if (act->get_node()->get_read_from_at(j) == write) {
- foundvalue = true;
- break;
- }
- }
- if (!foundvalue) {
- feasiblewrite = false;
- break;
- }
- }
- if (feasiblewrite) {
- priv->too_many_reads = true;
- return;
- }
- }
- }
-}
-
-/**
- * Updates the mo_graph with the constraints imposed from the current
- * read.
- *
- * Basic idea is the following: Go through each other thread and find
- * the last action that happened before our read. Two cases:
- *
- * (1) The action is a write => that write must either occur before
- * the write we read from or be the write we read from.
- *
- * (2) The action is a read => the write that that action read from
- * must occur before the write we read from or be the same write.
- *
- * @param curr The current action. Must be a read.
- * @param rf The ModelAction or Promise that curr reads from. Must be a write.
- * @return True if modification order edges were added; false otherwise
- */
-template <typename rf_type>
-bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
-{
- std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- unsigned int i;
- bool added = false;
- ASSERT(curr->is_read());
-
- /* Last SC fence in the current thread */
- ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Last SC fence in thread i */
- ModelAction *last_sc_fence_thread_local = NULL;
- if (int_to_id((int)i) != curr->get_tid())
- last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
-
- /* Last SC fence in thread i, before last SC fence in current thread */
- ModelAction *last_sc_fence_thread_before = NULL;
- if (last_sc_fence_local)
- last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
-
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
-
- if (act->is_write() && !act->equals(rf) && act != curr) {
- /* C++, Section 29.3 statement 5 */
- if (curr->is_seqcst() && last_sc_fence_thread_local &&
- *act < *last_sc_fence_thread_local) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
- /* C++, Section 29.3 statement 4 */
- else if (act->is_seqcst() && last_sc_fence_local &&
- *act < *last_sc_fence_local) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
- /* C++, Section 29.3 statement 6 */
- else if (last_sc_fence_thread_before &&
- *act < *last_sc_fence_thread_before) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
- }
-
- /*
- * Include at most one act per-thread that "happens
- * before" curr. Don't consider reflexively.
- */
- if (act->happens_before(curr) && act != curr) {
- if (act->is_write()) {
- if (!act->equals(rf)) {
- added = mo_graph->addEdge(act, rf) || added;
- }
- } else {
- const ModelAction *prevreadfrom = act->get_reads_from();
- //if the previous read is unresolved, keep going...
- if (prevreadfrom == NULL)
- continue;
-
- if (!prevreadfrom->equals(rf)) {
- added = mo_graph->addEdge(prevreadfrom, rf) || added;
- }
- }
- break;
- }
- }
- }
-
- /*
- * All compatible, thread-exclusive promises must be ordered after any
- * concrete loads from the same thread
- */
- for (unsigned int i = 0; i < promises->size(); i++)
- if ((*promises)[i]->is_compatible_exclusive(curr))
- added = mo_graph->addEdge(rf, (*promises)[i]) || added;
-
- return added;
-}
-
-/**
- * Updates the mo_graph with the constraints imposed from the current write.
- *
- * Basic idea is the following: Go through each other thread and find
- * the lastest action that happened before our write. Two cases:
- *
- * (1) The action is a write => that write must occur before
- * the current write
- *
- * (2) The action is a read => the write that that action read from
- * must occur before the current write.
- *
- * This method also handles two other issues:
- *
- * (I) Sequential Consistency: Making sure that if the current write is
- * seq_cst, that it occurs after the previous seq_cst write.
- *
- * (II) Sending the write back to non-synchronizing reads.
- *
- * @param curr The current action. Must be a write.
- * @return True if modification order edges were added; false otherwise
- */
-bool ModelChecker::w_modification_order(ModelAction *curr)
-{
- std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- unsigned int i;
- bool added = false;
- ASSERT(curr->is_write());
-
- if (curr->is_seqcst()) {
- /* We have to at least see the last sequentially consistent write,
- so we are initialized. */
- ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
- if (last_seq_cst != NULL) {
- added = mo_graph->addEdge(last_seq_cst, curr) || added;
- }
- }
-
- /* Last SC fence in the current thread */
- ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Last SC fence in thread i, before last SC fence in current thread */
- ModelAction *last_sc_fence_thread_before = NULL;
- if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
- last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
-
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
- if (act == curr) {
- /*
- * 1) If RMW and it actually read from something, then we
- * already have all relevant edges, so just skip to next
- * thread.
- *
- * 2) If RMW and it didn't read from anything, we should
- * whatever edge we can get to speed up convergence.
- *
- * 3) If normal write, we need to look at earlier actions, so
- * continue processing list.
- */
- if (curr->is_rmw()) {
- if (curr->get_reads_from() != NULL)
- break;
- else
- continue;
- } else
- continue;
- }
-
- /* C++, Section 29.3 statement 7 */
- if (last_sc_fence_thread_before && act->is_write() &&
- *act < *last_sc_fence_thread_before) {
- added = mo_graph->addEdge(act, curr) || added;
- break;
- }
-
- /*
- * Include at most one act per-thread that "happens
- * before" curr
- */
- if (act->happens_before(curr)) {
- /*
- * Note: if act is RMW, just add edge:
- * act --mo--> curr
- * The following edge should be handled elsewhere:
- * readfrom(act) --mo--> act
- */
- if (act->is_write())
- added = mo_graph->addEdge(act, curr) || added;
- else if (act->is_read()) {
- //if previous read accessed a null, just keep going
- if (act->get_reads_from() == NULL)
- continue;
- added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
- }
- break;
- } else if (act->is_read() && !act->could_synchronize_with(curr) &&
- !act->same_thread(curr)) {
- /* We have an action that:
- (1) did not happen before us
- (2) is a read and we are a write
- (3) cannot synchronize with us
- (4) is in a different thread
- =>
- that read could potentially read from our write. Note that
- these checks are overly conservative at this point, we'll
- do more checks before actually removing the
- pendingfuturevalue.
-
- */
- if (thin_air_constraint_may_allow(curr, act)) {
- if (!is_infeasible())
- futurevalues->push_back(PendingFutureValue(curr, act));
- else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
- add_future_value(curr, act);
- }
- }
- }
- }
-
- /*
- * All compatible, thread-exclusive promises must be ordered after any
- * concrete stores to the same thread, or else they can be merged with
- * this store later
- */
- for (unsigned int i = 0; i < promises->size(); i++)
- if ((*promises)[i]->is_compatible_exclusive(curr))
- added = mo_graph->addEdge(curr, (*promises)[i]) || added;
-
- return added;
-}
-
-/** Arbitrary reads from the future are not allowed. Section 29.3
- * part 9 places some constraints. This method checks one result of constraint
- * constraint. Others require compiler support. */
-bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
-{
- if (!writer->is_rmw())
- return true;
-
- if (!reader->is_rmw())
- return true;
-
- for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
- if (search == reader)
- return false;
- if (search->get_tid() == reader->get_tid() &&
- search->happens_before(reader))
- break;
- }
-
- return true;
-}
-
-/**
- * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
- * some constraints. This method checks one the following constraint (others
- * require compiler support):
- *
- * If X --hb-> Y --mo-> Z, then X should not read from Z.
- */
-bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
-{
- std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
- unsigned int i;
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- const ModelAction *write_after_read = NULL;
-
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
-
- /* Don't disallow due to act == reader */
- if (!reader->happens_before(act) || reader == act)
- break;
- else if (act->is_write())
- write_after_read = act;
- else if (act->is_read() && act->get_reads_from() != NULL)
- write_after_read = act->get_reads_from();
- }
-
- if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
- return false;
- }
- return true;
-}
-
-/**
- * Finds the head(s) of the release sequence(s) containing a given ModelAction.
- * The ModelAction under consideration is expected to be taking part in
- * release/acquire synchronization as an object of the "reads from" relation.
- * Note that this can only provide release sequence support for RMW chains
- * which do not read from the future, as those actions cannot be traced until
- * their "promise" is fulfilled. Similarly, we may not even establish the
- * presence of a release sequence with certainty, as some modification order
- * constraints may be decided further in the future. Thus, this function
- * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
- * and a boolean representing certainty.
- *
- * @param rf The action that might be part of a release sequence. Must be a
- * write.
- * @param release_heads A pass-by-reference style return parameter. After
- * execution of this function, release_heads will contain the heads of all the
- * relevant release sequences, if any exists with certainty
- * @param pending A pass-by-reference style return parameter which is only used
- * when returning false (i.e., uncertain). Returns most information regarding
- * an uncertain release sequence, including any write operations that might
- * break the sequence.
- * @return true, if the ModelChecker is certain that release_heads is complete;
- * false otherwise
- */
-bool ModelChecker::release_seq_heads(const ModelAction *rf,
- rel_heads_list_t *release_heads,
- struct release_seq *pending) const
-{
- /* Only check for release sequences if there are no cycles */
- if (mo_graph->checkForCycles())
- return false;
-
- while (rf) {
- ASSERT(rf->is_write());
-
- if (rf->is_release())
- release_heads->push_back(rf);
- else if (rf->get_last_fence_release())
- release_heads->push_back(rf->get_last_fence_release());
- if (!rf->is_rmw())
- break; /* End of RMW chain */
-
- /** @todo Need to be smarter here... In the linux lock
- * example, this will run to the beginning of the program for
- * every acquire. */
- /** @todo The way to be smarter here is to keep going until 1
- * thread has a release preceded by an acquire and you've seen
- * both. */
-
- /* acq_rel RMW is a sufficient stopping condition */
- if (rf->is_acquire() && rf->is_release())
- return true; /* complete */
-
- rf = rf->get_reads_from();
- };
- if (!rf) {
- /* read from future: need to settle this later */
- pending->rf = NULL;
- return false; /* incomplete */
- }
-
- if (rf->is_release())
- return true; /* complete */
-
- /* else relaxed write
- * - check for fence-release in the same thread (29.8, stmt. 3)
- * - check modification order for contiguous subsequence
- * -> rf must be same thread as release */
-
- const ModelAction *fence_release = rf->get_last_fence_release();
- /* Synchronize with a fence-release unconditionally; we don't need to
- * find any more "contiguous subsequence..." for it */
- if (fence_release)
- release_heads->push_back(fence_release);
-
- int tid = id_to_int(rf->get_tid());
- std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
- action_list_t *list = &(*thrd_lists)[tid];
- action_list_t::const_reverse_iterator rit;
-
- /* Find rf in the thread list */
- rit = std::find(list->rbegin(), list->rend(), rf);
- ASSERT(rit != list->rend());
-
- /* Find the last {write,fence}-release */
- for (; rit != list->rend(); rit++) {
- if (fence_release && *(*rit) < *fence_release)
- break;
- if ((*rit)->is_release())
- break;
- }
- if (rit == list->rend()) {
- /* No write-release in this thread */
- return true; /* complete */
- } else if (fence_release && *(*rit) < *fence_release) {
- /* The fence-release is more recent (and so, "stronger") than
- * the most recent write-release */
- return true; /* complete */
- } /* else, need to establish contiguous release sequence */
- ModelAction *release = *rit;
-
- ASSERT(rf->same_thread(release));
-
- pending->writes.clear();
-
- bool certain = true;
- for (unsigned int i = 0; i < thrd_lists->size(); i++) {
- if (id_to_int(rf->get_tid()) == (int)i)
- continue;
- list = &(*thrd_lists)[i];
-
- /* Can we ensure no future writes from this thread may break
- * the release seq? */
- bool future_ordered = false;
-
- ModelAction *last = get_last_action(int_to_id(i));
- Thread *th = get_thread(int_to_id(i));
- if ((last && rf->happens_before(last)) ||
- !is_enabled(th) ||
- th->is_complete())
- future_ordered = true;
-
- ASSERT(!th->is_model_thread() || future_ordered);
-
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- const ModelAction *act = *rit;
- /* Reach synchronization -> this thread is complete */
- if (act->happens_before(release))
- break;
- if (rf->happens_before(act)) {
- future_ordered = true;
- continue;
- }
-
- /* Only non-RMW writes can break release sequences */
- if (!act->is_write() || act->is_rmw())
- continue;
-
- /* Check modification order */
- if (mo_graph->checkReachable(rf, act)) {
- /* rf --mo--> act */
- future_ordered = true;
- continue;
- }
- if (mo_graph->checkReachable(act, release))
- /* act --mo--> release */
- break;
- if (mo_graph->checkReachable(release, act) &&
- mo_graph->checkReachable(act, rf)) {
- /* release --mo-> act --mo--> rf */
- return true; /* complete */
- }
- /* act may break release sequence */
- pending->writes.push_back(act);
- certain = false;
- }
- if (!future_ordered)
- certain = false; /* This thread is uncertain */
- }
-
- if (certain) {
- release_heads->push_back(release);
- pending->writes.clear();
- } else {
- pending->release = release;
- pending->rf = rf;
- }
- return certain;
-}
-
-/**
- * An interface for getting the release sequence head(s) with which a
- * given ModelAction must synchronize. This function only returns a non-empty
- * result when it can locate a release sequence head with certainty. Otherwise,
- * it may mark the internal state of the ModelChecker so that it will handle
- * the release sequence at a later time, causing @a acquire to update its
- * synchronization at some later point in execution.
- *
- * @param acquire The 'acquire' action that may synchronize with a release
- * sequence
- * @param read The read action that may read from a release sequence; this may
- * be the same as acquire, or else an earlier action in the same thread (i.e.,
- * when 'acquire' is a fence-acquire)
- * @param release_heads A pass-by-reference return parameter. Will be filled
- * with the head(s) of the release sequence(s), if they exists with certainty.
- * @see ModelChecker::release_seq_heads
- */
-void ModelChecker::get_release_seq_heads(ModelAction *acquire,
- ModelAction *read, rel_heads_list_t *release_heads)
-{
- const ModelAction *rf = read->get_reads_from();
- struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
- sequence->acquire = acquire;
- sequence->read = read;
-
- if (!release_seq_heads(rf, release_heads, sequence)) {
- /* add act to 'lazy checking' list */
- pending_rel_seqs->push_back(sequence);
- } else {
- snapshot_free(sequence);
- }
-}
-
-/**
- * Attempt to resolve all stashed operations that might synchronize with a
- * release sequence for a given location. This implements the "lazy" portion of
- * determining whether or not a release sequence was contiguous, since not all
- * modification order information is present at the time an action occurs.
- *
- * @param location The location/object that should be checked for release
- * sequence resolutions. A NULL value means to check all locations.
- * @param work_queue The work queue to which to add work items as they are
- * generated
- * @return True if any updates occurred (new synchronization, new mo_graph
- * edges)
- */
-bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
-{
- bool updated = false;
- std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
- while (it != pending_rel_seqs->end()) {
- struct release_seq *pending = *it;
- ModelAction *acquire = pending->acquire;
- const ModelAction *read = pending->read;
-
- /* Only resolve sequences on the given location, if provided */
- if (location && read->get_location() != location) {
- it++;
- continue;
- }
-
- const ModelAction *rf = read->get_reads_from();
- rel_heads_list_t release_heads;
- bool complete;
- complete = release_seq_heads(rf, &release_heads, pending);
- for (unsigned int i = 0; i < release_heads.size(); i++) {
- if (!acquire->has_synchronized_with(release_heads[i])) {
- if (acquire->synchronize_with(release_heads[i]))
- updated = true;
- else
- set_bad_synchronization();
- }
- }
-
- if (updated) {
- /* Re-check all pending release sequences */
- work_queue->push_back(CheckRelSeqWorkEntry(NULL));
- /* Re-check read-acquire for mo_graph edges */
- if (acquire->is_read())
- work_queue->push_back(MOEdgeWorkEntry(acquire));
-
- /* propagate synchronization to later actions */
- action_list_t::reverse_iterator rit = action_trace->rbegin();
- for (; (*rit) != acquire; rit++) {
- ModelAction *propagate = *rit;
- if (acquire->happens_before(propagate)) {
- propagate->synchronize_with(acquire);
- /* Re-check 'propagate' for mo_graph edges */
- work_queue->push_back(MOEdgeWorkEntry(propagate));
- }
- }
- }
- if (complete) {
- it = pending_rel_seqs->erase(it);
- snapshot_free(pending);
- } else {
- it++;
- }
- }
-
- // If we resolved promises or data races, see if we have realized a data race.
- checkDataRaces();
-
- return updated;
-}
-
-/**
- * Performs various bookkeeping operations for the current ModelAction. For
- * instance, adds action to the per-object, per-thread action vector and to the
- * action trace list of all thread actions.
- *
- * @param act is the ModelAction to add.
- */
-void ModelChecker::add_action_to_lists(ModelAction *act)
-{
- int tid = id_to_int(act->get_tid());
- ModelAction *uninit = NULL;
- int uninit_id = -1;
- action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
- if (list->empty() && act->is_atomic_var()) {
- uninit = new_uninitialized_action(act->get_location());
- uninit_id = id_to_int(uninit->get_tid());
- list->push_back(uninit);
- }
- list->push_back(act);
-
- action_trace->push_back(act);
- if (uninit)
- action_trace->push_front(uninit);
-
- std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
- if (tid >= (int)vec->size())
- vec->resize(priv->next_thread_id);
- (*vec)[tid].push_back(act);
- if (uninit)
- (*vec)[uninit_id].push_front(uninit);
-
- if ((int)thrd_last_action->size() <= tid)
- thrd_last_action->resize(get_num_threads());
- (*thrd_last_action)[tid] = act;
- if (uninit)
- (*thrd_last_action)[uninit_id] = uninit;
-
- if (act->is_fence() && act->is_release()) {
- if ((int)thrd_last_fence_release->size() <= tid)
- thrd_last_fence_release->resize(get_num_threads());
- (*thrd_last_fence_release)[tid] = act;
- }
-
- if (act->is_wait()) {
- void *mutex_loc = (void *) act->get_value();
- get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
-
- std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
- if (tid >= (int)vec->size())
- vec->resize(priv->next_thread_id);
- (*vec)[tid].push_back(act);
- }
-}
-
-/**
- * @brief Get the last action performed by a particular Thread
- * @param tid The thread ID of the Thread in question
- * @return The last action in the thread
- */
-ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
-{
- int threadid = id_to_int(tid);
- if (threadid < (int)thrd_last_action->size())
- return (*thrd_last_action)[id_to_int(tid)];
- else
- return NULL;
-}
-
-/**
- * @brief Get the last fence release performed by a particular Thread
- * @param tid The thread ID of the Thread in question
- * @return The last fence release in the thread, if one exists; NULL otherwise
- */
-ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
-{
- int threadid = id_to_int(tid);
- if (threadid < (int)thrd_last_fence_release->size())
- return (*thrd_last_fence_release)[id_to_int(tid)];
- else
- return NULL;
-}
-
-/**
- * Gets the last memory_order_seq_cst write (in the total global sequence)
- * performed on a particular object (i.e., memory location), not including the
- * current action.
- * @param curr The current ModelAction; also denotes the object location to
- * check
- * @return The last seq_cst write
- */
-ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
-{
- void *location = curr->get_location();
- action_list_t *list = get_safe_ptr_action(obj_map, location);
- /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++)
- if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
- return *rit;
- return NULL;
-}
-
-/**
- * Gets the last memory_order_seq_cst fence (in the total global sequence)
- * performed in a particular thread, prior to a particular fence.
- * @param tid The ID of the thread to check
- * @param before_fence The fence from which to begin the search; if NULL, then
- * search for the most recent fence in the thread.
- * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
- */
-ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
-{
- /* All fences should have NULL location */
- action_list_t *list = get_safe_ptr_action(obj_map, NULL);
- action_list_t::reverse_iterator rit = list->rbegin();
-
- if (before_fence) {
- for (; rit != list->rend(); rit++)
- if (*rit == before_fence)
- break;
-
- ASSERT(*rit == before_fence);
- rit++;
- }
-
- for (; rit != list->rend(); rit++)
- if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
- return *rit;
- return NULL;
-}
-
-/**
- * Gets the last unlock operation performed on a particular mutex (i.e., memory
- * location). This function identifies the mutex according to the current
- * action, which is presumed to perform on the same mutex.
- * @param curr The current ModelAction; also denotes the object location to
- * check
- * @return The last unlock operation
- */
-ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
-{
- void *location = curr->get_location();
- action_list_t *list = get_safe_ptr_action(obj_map, location);
- /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++)
- if ((*rit)->is_unlock() || (*rit)->is_wait())
- return *rit;
- return NULL;
-}
-
-ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
-{
- ModelAction *parent = get_last_action(tid);
- if (!parent)
- parent = get_thread(tid)->get_creation();
- return parent;
-}
-
-/**
- * Returns the clock vector for a given thread.
- * @param tid The thread whose clock vector we want
- * @return Desired clock vector
- */
-ClockVector * ModelChecker::get_cv(thread_id_t tid) const
-{
- return get_parent_action(tid)->get_cv();
-}
-
-/**
- * Resolve a set of Promises with a current write. The set is provided in the
- * Node corresponding to @a write.
- * @param write The ModelAction that is fulfilling Promises
- * @return True if promises were resolved; false otherwise
- */
-bool ModelChecker::resolve_promises(ModelAction *write)
-{
- bool haveResolved = false;
- std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
- promise_list_t mustResolve, resolved;
-
- for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
- Promise *promise = (*promises)[promise_index];
- if (write->get_node()->get_promise(i)) {
- ModelAction *read = promise->get_action();
- read_from(read, write);
- //Make sure the promise's value matches the write's value
- ASSERT(promise->is_compatible(write));
- mo_graph->resolvePromise(read, write, &mustResolve);
-
- resolved.push_back(promise);
- promises->erase(promises->begin() + promise_index);
- actions_to_check.push_back(read);
-
- haveResolved = true;
- } else
- promise_index++;
- }
-
- for (unsigned int i = 0; i < mustResolve.size(); i++) {
- if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
- == resolved.end())
- priv->failed_promise = true;
- }
- for (unsigned int i = 0; i < resolved.size(); i++)
- delete resolved[i];
- //Check whether reading these writes has made threads unable to
- //resolve promises
-
- for (unsigned int i = 0; i < actions_to_check.size(); i++) {
- ModelAction *read = actions_to_check[i];
- mo_check_promises(read, true);
- }
-
- return haveResolved;
-}
-
-/**
- * Compute the set of promises that could potentially be satisfied by this
- * action. Note that the set computation actually appears in the Node, not in
- * ModelChecker.
- * @param curr The ModelAction that may satisfy promises
- */
-void ModelChecker::compute_promises(ModelAction *curr)
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- const ModelAction *act = promise->get_action();
- if (!act->happens_before(curr) &&
- act->is_read() &&
- !act->could_synchronize_with(curr) &&
- !act->same_thread(curr) &&
- act->get_location() == curr->get_location() &&
- promise->get_value() == curr->get_value()) {
- curr->get_node()->set_promise(i, act->is_rmw());
- }
- }
-}
-
-/** Checks promises in response to change in ClockVector Threads. */
-void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- const ModelAction *act = promise->get_action();
- if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
- merge_cv->synchronized_since(act)) {
- if (promise->eliminate_thread(tid)) {
- //Promise has failed
- priv->failed_promise = true;
- return;
- }
- }
- }
-}
-
-void ModelChecker::check_promises_thread_disabled()
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->has_failed()) {
- priv->failed_promise = true;
- return;
- }
- }
-}
-
-/**
- * @brief Checks promises in response to addition to modification order for
- * threads.
- *
- * We test whether threads are still available for satisfying promises after an
- * addition to our modification order constraints. Those that are unavailable
- * are "eliminated". Once all threads are eliminated from satisfying a promise,
- * that promise has failed.
- *
- * @param act The ModelAction which updated the modification order
- * @param is_read_check Should be true if act is a read and we must check for
- * updates to the store from which it read (there is a distinction here for
- * RMW's, which are both a load and a store)
- */
-void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
-{
- const ModelAction *write = is_read_check ? act->get_reads_from() : act;
-
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- const ModelAction *pread = promise->get_action();
-
- // Is this promise on the same location?
- if (!pread->same_var(write))
- continue;
-
- if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
- priv->failed_promise = true;
- return;
- }
-
- // Don't do any lookups twice for the same thread
- if (!promise->thread_is_available(act->get_tid()))
- continue;
-
- if (mo_graph->checkReachable(promise, write)) {
- if (mo_graph->checkPromise(write, promise)) {
- priv->failed_promise = true;
- return;
- }
- }
- }
-}
-
-/**
- * Compute the set of writes that may break the current pending release
- * sequence. This information is extracted from previou release sequence
- * calculations.
- *
- * @param curr The current ModelAction. Must be a release sequence fixup
- * action.
- */
-void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
-{
- if (pending_rel_seqs->empty())
- return;
-
- struct release_seq *pending = pending_rel_seqs->back();
- for (unsigned int i = 0; i < pending->writes.size(); i++) {
- const ModelAction *write = pending->writes[i];
- curr->get_node()->add_relseq_break(write);
- }
-
- /* NULL means don't break the sequence; just synchronize */
- curr->get_node()->add_relseq_break(NULL);
-}
-
-/**
- * Build up an initial set of all past writes that this 'read' action may read
- * from. This set is determined by the clock vector's "happens before"
- * relationship.
- * @param curr is the current ModelAction that we are exploring; it must be a
- * 'read' operation.
- */
-void ModelChecker::build_reads_from_past(ModelAction *curr)
-{
- std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- unsigned int i;
- ASSERT(curr->is_read());
-
- ModelAction *last_sc_write = NULL;
-
- if (curr->is_seqcst())
- last_sc_write = get_last_seq_cst_write(curr);
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
-
- /* Only consider 'write' actions */
- if (!act->is_write() || act == curr)
- continue;
-
- /* Don't consider more than one seq_cst write if we are a seq_cst read. */
- bool allow_read = true;
-
- if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
- allow_read = false;
- else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
- allow_read = false;
-
- if (allow_read) {
- /* Only add feasible reads */
- mo_graph->startChanges();
- r_modification_order(curr, act);
- if (!is_infeasible())
- curr->get_node()->add_read_from(act);
- mo_graph->rollbackChanges();
- }
-
- /* Include at most one act per-thread that "happens before" curr */
- if (act->happens_before(curr))
- break;
- }
- }
- /* We may find no valid may-read-from only if the execution is doomed */
- if (!curr->get_node()->get_read_from_size()) {
- priv->no_valid_reads = true;
- set_assert();
- }
-
- if (DBG_ENABLED()) {
- model_print("Reached read action:\n");
- curr->print();
- model_print("Printing may_read_from\n");
- curr->get_node()->print_may_read_from();
- model_print("End printing may_read_from\n");
- }
-}
-
-bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
-{
- while (true) {
- /* UNINIT actions don't have a Node, and they never sleep */
- if (write->is_uninitialized())
- return true;
- Node *prevnode = write->get_node()->get_parent();
-
- bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
- if (write->is_release() && thread_sleep)
- return true;
- if (!write->is_rmw()) {
- return false;
- }
- if (write->get_reads_from() == NULL)
- return true;
- write = write->get_reads_from();
- }
-}
-
-/**
- * @brief Create a new action representing an uninitialized atomic
- * @param location The memory location of the atomic object
- * @return A pointer to a new ModelAction
- */
-ModelAction * ModelChecker::new_uninitialized_action(void *location) const
-{
- ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
- act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
- act->create_cv(NULL);
- return act;
-}
-
-static void print_list(action_list_t *list)
-{
- action_list_t::iterator it;
-
- model_print("---------------------------------------------------------------------\n");
-
- unsigned int hash = 0;
-
- for (it = list->begin(); it != list->end(); it++) {
- (*it)->print();
- hash = hash^(hash<<3)^((*it)->hash());
- }
- model_print("HASH %u\n", hash);
- model_print("---------------------------------------------------------------------\n");
-}
-
-#if SUPPORT_MOD_ORDER_DUMP
-void ModelChecker::dumpGraph(char *filename) const
-{
- char buffer[200];
- sprintf(buffer, "%s.dot", filename);
- FILE *file = fopen(buffer, "w");
- fprintf(file, "digraph %s {\n", filename);
- mo_graph->dumpNodes(file);
- ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
-
- for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
- ModelAction *action = *it;
- if (action->is_read()) {
- fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
- if (action->get_reads_from() != NULL)
- fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
- }
- if (thread_array[action->get_tid()] != NULL) {
- fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
- }
-
- thread_array[action->get_tid()] = action;
- }
- fprintf(file, "}\n");
- model_free(thread_array);
- fclose(file);
-}
-#endif
-
-/** @brief Prints an execution trace summary. */
-void ModelChecker::print_summary() const
-{
-#if SUPPORT_MOD_ORDER_DUMP
- char buffername[100];
- sprintf(buffername, "exec%04u", stats.num_total);
- mo_graph->dumpGraphToFile(buffername);
- sprintf(buffername, "graph%04u", stats.num_total);
- dumpGraph(buffername);
-#endif
-
- model_print("Execution %d:", stats.num_total);
- if (isfeasibleprefix())
- model_print("\n");
- else
- print_infeasibility(" INFEASIBLE");
- print_list(action_trace);
- model_print("\n");
-}
-
-/**
- * Add a Thread to the system for the first time. Should only be called once
- * per thread.
- * @param t The Thread to add
- */
-void ModelChecker::add_thread(Thread *t)
-{
- thread_map->put(id_to_int(t->get_id()), t);
- scheduler->add_thread(t);
-}
-
-/**
- * Removes a thread from the scheduler.
- * @param the thread to remove.
- */
-void ModelChecker::remove_thread(Thread *t)
-{
- scheduler->remove_thread(t);
-}
-
-/**
- * @brief Get a Thread reference by its ID
- * @param tid The Thread's ID
- * @return A Thread reference
- */
-Thread * ModelChecker::get_thread(thread_id_t tid) const
-{
- return thread_map->get(id_to_int(tid));
-}
-
-/**
- * @brief Get a reference to the Thread in which a ModelAction was executed
- * @param act The ModelAction
- * @return A Thread reference
- */
-Thread * ModelChecker::get_thread(const ModelAction *act) const
-{
- return get_thread(act->get_tid());
-}
-
-/**
- * @brief Check if a Thread is currently enabled
- * @param t The Thread to check
- * @return True if the Thread is currently enabled
- */
-bool ModelChecker::is_enabled(Thread *t) const
-{
- return scheduler->is_enabled(t);
-}
-
-/**
- * @brief Check if a Thread is currently enabled
- * @param tid The ID of the Thread to check
- * @return True if the Thread is currently enabled
- */
-bool ModelChecker::is_enabled(thread_id_t tid) const
-{
- return scheduler->is_enabled(tid);
-}
-
-/**
- * Switch from a user-context to the "master thread" context (a.k.a. system
- * context). This switch is made with the intention of exploring a particular
- * model-checking action (described by a ModelAction object). Must be called
- * from a user-thread context.
- *
- * @param act The current action that will be explored. May be NULL only if
- * trace is exiting via an assertion (see ModelChecker::set_assert and
- * ModelChecker::has_asserted).
- * @return Return the value returned by the current action
- */
-uint64_t ModelChecker::switch_to_master(ModelAction *act)
-{
- DBG();
- Thread *old = thread_current();
- ASSERT(!old->get_pending());
- old->set_pending(act);
- if (Thread::swap(old, &system_context) < 0) {
- perror("swap threads");
- exit(EXIT_FAILURE);
- }
- return old->get_return_value();
-}
-
-/**
- * Takes the next step in the execution, if possible.
- * @param curr The current step to take
- * @return Returns the next Thread to run, if any; NULL if this execution
- * should terminate
- */
-Thread * ModelChecker::take_step(ModelAction *curr)
-{
- Thread *curr_thrd = get_thread(curr);
- ASSERT(curr_thrd->get_state() == THREAD_READY);
-
- curr = check_current_action(curr);
-
- /* Infeasible -> don't take any more steps */
- if (is_infeasible())
- return NULL;
- else if (isfeasibleprefix() && have_bug_reports()) {
- set_assert();
- return NULL;
- }
-
- if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
- return NULL;
-
- if (curr_thrd->is_blocked() || curr_thrd->is_complete())
- scheduler->remove_thread(curr_thrd);
-
- Thread *next_thrd = get_next_thread(curr);
- next_thrd = scheduler->next_thread(next_thrd);
-
- DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
- next_thrd ? id_to_int(next_thrd->get_id()) : -1);
-
- /*
- * Launch end-of-execution release sequence fixups only when there are:
- *
- * (1) no more user threads to run (or when execution replay chooses
- * the 'model_thread')
- * (2) pending release sequences
- * (3) pending assertions (i.e., data races)
- * (4) no pending promises
- */
- if (!pending_rel_seqs->empty() && (!next_thrd || next_thrd->is_model_thread()) &&
- is_feasible_prefix_ignore_relseq() && !unrealizedraces.empty()) {
- model_print("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
- pending_rel_seqs->size());
- ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
- std::memory_order_seq_cst, NULL, VALUE_NONE,
- model_thread);
- model_thread->set_pending(fixup);
- return model_thread;
- }
-
- /* next_thrd == NULL -> don't take any more steps */
- if (!next_thrd)
- return NULL;
-
- return next_thrd;
-}
-
-/** Wrapper to run the user's main function, with appropriate arguments */
-void user_main_wrapper(void *)
-{
- user_main(model->params.argc, model->params.argv);
-}
-
-/** @brief Run ModelChecker for the user program */
-void ModelChecker::run()
-{
- do {
- thrd_t user_thread;
- Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
- add_thread(t);
-
- do {
- for (unsigned int i = 0; i < get_num_threads(); i++) {
- thread_id_t tid = int_to_id(i);
- Thread *thr = get_thread(tid);
- if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
- scheduler->next_thread(thr);
- Thread::swap(&system_context, thr);
- }
- }
-
- /* Catch assertions from prior take_step or from
- * between-ModelAction bugs (e.g., data races) */
- if (has_asserted())
- break;
-
- /* Consume the next action for a Thread */
- ModelAction *curr = t->get_pending();
- t->set_pending(NULL);
- t = take_step(curr);
- } while (t && !t->is_model_thread());
- /** @TODO Re-write release sequence fixups here */
- } while (next_execution());