X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=model.cc;fp=model.cc;h=4f2719f338c8afa9ba05d2f0835fd565bd6dfbd2;hb=b8b39c87557325a384faa45d0cae56a6f71f52b1;hp=2c27567954f3618c9a94e3e5640955d5b08b1475;hpb=59eb730e1d19a0825008c40eb521bfc5c29df5f9;p=model-checker.git diff --git a/model.cc b/model.cc index 2c27567..4f2719f 100644 --- a/model.cc +++ b/model.cc @@ -47,6 +47,10 @@ ModelChecker::ModelChecker(struct model_params params) : priv = (struct model_snapshot_members *)calloc(1, sizeof(*priv)); /* First thread created will have id INITIAL_THREAD_ID */ priv->next_thread_id = INITIAL_THREAD_ID; + + /* Initialize a model-checker thread, for special ModelActions */ + model_thread = new Thread(get_next_id()); + thread_map->put(id_to_int(model_thread->get_id()), model_thread); } /** @brief Destructor */ @@ -166,6 +170,10 @@ Thread * ModelChecker::get_next_thread(ModelAction *curr) /* The next node will try to read from a different future value. */ tid = next->get_tid(); node_stack->pop_restofstack(2); + } else if (nextnode->increment_relseq_break()) { + /* The next node will try to resolve a release sequence differently */ + tid = next->get_tid(); + node_stack->pop_restofstack(2); } else { /* Make a different thread execute for next step */ scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid()))); @@ -249,7 +257,7 @@ bool ModelChecker::next_execution() num_feasible_executions++; } - DEBUG("Number of acquires waiting on pending release sequences: %lu\n", + DEBUG("Number of acquires waiting on pending release sequences: %zu\n", pending_rel_seqs->size()); if (isfinalfeasible() || DBG_ENABLED()) @@ -582,6 +590,76 @@ bool ModelChecker::process_thread_action(ModelAction *curr) 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 */ + if (checkDataRaces()) + set_assert(); +} + /** * Initialize the current action by performing one or more of the following * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward @@ -633,6 +711,8 @@ ModelAction * ModelChecker::initialize_curr_action(ModelAction *curr) */ if (newcurr->is_write()) compute_promises(newcurr); + else if (newcurr->is_relseq_fixup()) + compute_relseq_breakwrites(newcurr); } return newcurr; } @@ -721,6 +801,9 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) 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) @@ -781,7 +864,8 @@ void ModelChecker::check_curr_backtracking(ModelAction * curr) { if ((!parnode->backtrack_empty() || !currnode->read_from_empty() || !currnode->future_value_empty() || - !currnode->promise_empty()) + !currnode->promise_empty() || + !currnode->relseq_break_empty()) && (!priv->next_backtrack || *curr > *priv->next_backtrack)) { priv->next_backtrack = curr; @@ -1299,10 +1383,14 @@ bool ModelChecker::release_seq_heads(const ModelAction *rf, bool future_ordered = false; ModelAction *last = get_last_action(int_to_id(i)); - if (last && (rf->happens_before(last) || - get_thread(int_to_id(i))->is_complete())) + Thread *th = get_thread(int_to_id(i)); + if ((last && rf->happens_before(last)) || + !scheduler->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 */ @@ -1691,6 +1779,29 @@ void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) } } +/** + * 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" @@ -1894,7 +2005,7 @@ bool ModelChecker::take_step() { if (has_asserted()) return false; - Thread *curr = thread_current(); + Thread *curr = priv->current_action ? get_thread(priv->current_action) : NULL; if (curr) { if (curr->get_state() == THREAD_READY) { ASSERT(priv->current_action); @@ -1917,6 +2028,26 @@ bool ModelChecker::take_step() { DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1, next ? id_to_int(next->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 || next->is_model_thread()) && + isfinalfeasible() && !unrealizedraces.empty()) { + printf("*** 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); + set_current_action(fixup); + return true; + } + /* next == NULL -> don't take any more steps */ if (!next) return false;