X-Git-Url: http://plrg.eecs.uci.edu/git/?p=model-checker.git;a=blobdiff_plain;f=model.cc;h=7048096ca25e0cbe0ad9928504802de4231c5a18;hp=fab1a5994feb96e6ee22c59e941b7fc9550ff041;hb=875ebf8e11b4bdd702604785837b6b91b748900d;hpb=5fa2efec1354b2781ff0b29460ec8e9b8fa75991 diff --git a/model.cc b/model.cc index fab1a59..7048096 100644 --- a/model.cc +++ b/model.cc @@ -263,10 +263,6 @@ Thread * ModelChecker::get_next_thread(ModelAction *curr) /* The next node will read from a different value. */ tid = next->get_tid(); node_stack->pop_restofstack(2); - } else if (nextnode->increment_future_value()) { - /* 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(); @@ -282,6 +278,8 @@ Thread * ModelChecker::get_next_thread(ModelAction *curr) earliest_diverge = prevnode->get_action(); } } + /* Start the round robin scheduler from this thread id */ + scheduler->set_scheduler_thread(tid); /* The correct sleep set is in the parent node. */ execute_sleep_set(); @@ -313,14 +311,41 @@ void ModelChecker::execute_sleep_set() } } +/** + * @brief Should the current action wake up a given thread? + * + * @param curr The current action + * @param thread The thread that we might wake up + * @return True, if we should wake up the sleeping thread; false otherwise + */ +bool ModelChecker::should_wake_up(const ModelAction *curr, const Thread *thread) const +{ + const ModelAction *asleep = thread->get_pending(); + /* Don't allow partial RMW to wake anyone up */ + if (curr->is_rmwr()) + return false; + /* Synchronizing actions may have been backtracked */ + if (asleep->could_synchronize_with(curr)) + return true; + /* All acquire/release fences and fence-acquire/store-release */ + if (asleep->is_fence() && asleep->is_acquire() && curr->is_release()) + return true; + /* Fence-release + store can awake load-acquire on the same location */ + if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) { + ModelAction *fence_release = get_last_fence_release(curr->get_tid()); + if (fence_release && *(get_last_action(thread->get_id())) < *fence_release) + return true; + } + return false; +} + void ModelChecker::wake_up_sleeping_actions(ModelAction *curr) { for (unsigned int i = 0; i < get_num_threads(); i++) { Thread *thr = get_thread(int_to_id(i)); if (scheduler->is_sleep_set(thr)) { - ModelAction *pending_act = thr->get_pending(); - if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr)) - //Remove this thread from sleep set + if (should_wake_up(curr, thr)) + /* Remove this thread from sleep set */ scheduler->remove_sleep(thr); } } @@ -458,8 +483,10 @@ void ModelChecker::record_stats() stats.num_buggy_executions++; else if (is_complete_execution()) stats.num_complete++; - else + else if (scheduler->all_threads_sleeping()) stats.num_redundant++; + else + ASSERT(false); } /** @brief Print execution stats */ @@ -545,6 +572,18 @@ bool ModelChecker::next_execution() return true; } +/** + * @brief Find the last fence-related backtracking conflict for a ModelAction + * + * This function performs the search for the most recent conflicting action + * against which we should perform backtracking, as affected by fence + * operations. This includes pairs of potentially-synchronizing actions which + * occur due to fence-acquire or fence-release, and hence should be explored in + * the opposite execution order. + * + * @param act The current action + * @return The most recent action which conflicts with act due to fences + */ ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const { /* Only perform release/acquire fence backtracking for stores */ @@ -560,16 +599,22 @@ ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const if (!last_release) return NULL; - std::vector< ModelAction *, ModelAlloc > acquire_fences(get_num_threads(), NULL); - std::vector< ModelAction *, ModelAlloc > prior_loads(get_num_threads(), NULL); - bool found_acquire_fences = false; + /* Skip past the release */ + action_list_t *list = action_trace; + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) + if (*rit == last_release) + break; + ASSERT(rit != list->rend()); + /* Find a prior: * load-acquire * or * load --sb-> fence-acquire */ - action_list_t *list = action_trace; - action_list_t::reverse_iterator rit; - for (rit = list->rbegin(); rit != list->rend(); rit++) { + std::vector< ModelAction *, ModelAlloc > acquire_fences(get_num_threads(), NULL); + std::vector< ModelAction *, ModelAlloc > prior_loads(get_num_threads(), NULL); + bool found_acquire_fences = false; + for ( ; rit != list->rend(); rit++) { ModelAction *prev = *rit; if (act->same_thread(prev)) continue; @@ -600,6 +645,17 @@ ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const return latest_backtrack; } +/** + * @brief Find the last backtracking conflict for a ModelAction + * + * This function performs the search for the most recent conflicting action + * against which we should perform backtracking. This primary includes pairs of + * synchronizing actions which should be explored in the opposite execution + * order. + * + * @param act The current action + * @return The most recent action which conflicts with act + */ ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const { switch (act->get_type()) { @@ -784,42 +840,52 @@ ModelAction * ModelChecker::get_next_backtrack() } /** - * Processes a read or rmw model action. + * Processes a read model action. * @param curr is the read model action to process. - * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw. * @return True if processing this read updates the mo_graph. */ -bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw) +bool ModelChecker::process_read(ModelAction *curr) { + Node *node = curr->get_node(); uint64_t value = VALUE_NONE; bool updated = false; while (true) { - const ModelAction *reads_from = curr->get_node()->get_read_from(); - if (reads_from != NULL) { - mo_graph->startChanges(); - - value = reads_from->get_value(); - bool r_status = false; + switch (node->get_read_from_status()) { + case READ_FROM_PAST: { + const ModelAction *rf = node->get_read_from_past(); + ASSERT(rf); - if (!second_part_of_rmw) { - check_recency(curr, reads_from); - r_status = r_modification_order(curr, reads_from); - } + mo_graph->startChanges(); + value = rf->get_value(); + check_recency(curr, rf); + bool r_status = r_modification_order(curr, rf); - if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) { + if (is_infeasible() && node->increment_read_from()) { mo_graph->rollbackChanges(); priv->too_many_reads = false; continue; } - read_from(curr, reads_from); + read_from(curr, rf); mo_graph->commitChanges(); mo_check_promises(curr, true); updated |= r_status; - } else if (!second_part_of_rmw) { + break; + } + case READ_FROM_PROMISE: { + Promise *promise = curr->get_node()->get_read_from_promise(); + promise->add_reader(curr); + value = promise->get_value(); + curr->set_read_from_promise(promise); + mo_graph->startChanges(); + updated = r_modification_order(curr, promise); + mo_graph->commitChanges(); + break; + } + case READ_FROM_FUTURE: { /* Read from future value */ - struct future_value fv = curr->get_node()->get_future_value(); + struct future_value fv = node->get_future_value(); Promise *promise = new Promise(curr, fv); value = fv.value; curr->set_read_from_promise(promise); @@ -827,6 +893,10 @@ bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw) mo_graph->startChanges(); updated = r_modification_order(curr, promise); mo_graph->commitChanges(); + break; + } + default: + ASSERT(false); } get_thread(curr)->set_return_value(value); return updated; @@ -952,7 +1022,7 @@ void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *read write_thread = write_thread->get_parent(); struct future_value fv = { - writer->get_value(), + writer->get_write_value(), writer->get_seq_number() + params.maxfuturedelay, write_thread->get_id(), }; @@ -1055,7 +1125,7 @@ bool ModelChecker::process_thread_action(ModelAction *curr) 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); + Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr)); add_thread(th); th->set_creation(curr); /* Promises can be satisfied by children */ @@ -1254,8 +1324,9 @@ bool ModelChecker::initialize_curr_action(ModelAction **curr) */ bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf) { + ASSERT(rf); act->set_read_from(rf); - if (rf != NULL && act->is_acquire()) { + if (act->is_acquire()) { rel_heads_list_t release_heads; get_release_seq_heads(act, act, &release_heads); int num_heads = release_heads.size(); @@ -1269,6 +1340,35 @@ bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf) return false; } +/** + * Check promises and eliminate potentially-satisfying threads when a thread is + * blocked (e.g., join, lock). A thread which is waiting on another thread can + * no longer satisfy a promise generated from that thread. + * + * @param blocker The thread on which a thread is waiting + * @param waiting The waiting thread + */ +void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting) +{ + for (unsigned int i = 0; i < promises->size(); i++) { + Promise *promise = (*promises)[i]; + if (!promise->thread_is_available(waiting->get_id())) + continue; + for (unsigned int j = 0; j < promise->get_num_readers(); j++) { + ModelAction *reader = promise->get_reader(j); + if (reader->get_tid() != blocker->get_id()) + continue; + if (promise->eliminate_thread(waiting->get_id())) { + /* Promise has failed */ + priv->failed_promise = true; + } else { + /* Only eliminate the 'waiting' thread once */ + return; + } + } + } +} + /** * @brief Check whether a model action is enabled. * @@ -1292,6 +1392,7 @@ bool ModelChecker::check_action_enabled(ModelAction *curr) { Thread *blocking = (Thread *)curr->get_location(); if (!blocking->is_complete()) { blocking->push_wait_list(curr); + thread_blocking_check_promises(blocking, get_thread(curr)); return false; } } @@ -1337,7 +1438,7 @@ ModelAction * ModelChecker::check_current_action(ModelAction *curr) /* Build may_read_from set for newly-created actions */ if (newly_explored && curr->is_read()) - build_reads_from_past(curr); + build_may_read_from(curr); /* Initialize work_queue with the "current action" work */ work_queue_t work_queue(1, CheckCurrWorkEntry(curr)); @@ -1354,7 +1455,7 @@ ModelAction * ModelChecker::check_current_action(ModelAction *curr) if (process_thread_action(curr)) update_all = true; - if (act->is_read() && process_read(act, second_part_of_rmw)) + if (act->is_read() && !second_part_of_rmw && process_read(act)) update = true; if (act->is_write() && process_write(act)) @@ -1423,7 +1524,6 @@ void ModelChecker::check_curr_backtracking(ModelAction *curr) 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); @@ -1530,7 +1630,7 @@ ModelAction * ModelChecker::process_rmw(ModelAction *act) { void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) { if (params.maxreads != 0) { - if (curr->get_node()->get_read_from_size() <= 1) + if (curr->get_node()->get_read_from_past_size() <= 1) return; //Must make sure that execution is currently feasible... We could //accidentally clear by rolling back @@ -1563,12 +1663,12 @@ void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) if (act->get_reads_from() != rf) return; - if (act->get_node()->get_read_from_size() <= 1) + if (act->get_node()->get_read_from_past_size() <= 1) return; } - for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) { + for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) { /* Get write */ - const ModelAction *write = curr->get_node()->get_read_from_at(i); + const ModelAction *write = curr->get_node()->get_read_from_past(i); /* Need a different write */ if (write == rf) @@ -1586,8 +1686,8 @@ void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf) 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) { + for (int j = 0; j < act->get_node()->get_read_from_past_size(); j++) { + if (act->get_node()->get_read_from_past(j) == write) { foundvalue = true; break; } @@ -1682,13 +1782,13 @@ bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *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; + const ModelAction *prevrf = act->get_reads_from(); + const Promise *prevrf_promise = act->get_reads_from_promise(); + if (prevrf) { + if (!prevrf->equals(rf)) + added = mo_graph->addEdge(prevrf, rf) || added; + } else if (!prevrf_promise->equals(rf)) { + added = mo_graph->addEdge(prevrf_promise, rf) || added; } } break; @@ -2360,15 +2460,17 @@ bool ModelChecker::resolve_promises(ModelAction *write) 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); + for (unsigned int j = 0; j < promise->get_num_readers(); j++) { + ModelAction *read = promise->get_reader(j); + read_from(read, write); + actions_to_check.push_back(read); + } //Make sure the promise's value matches the write's value ASSERT(promise->is_compatible(write)); - mo_graph->resolvePromise(read, write, &mustResolve); + mo_graph->resolvePromise(promise, write, &mustResolve); resolved.push_back(promise); promises->erase(promises->begin() + promise_index); - actions_to_check.push_back(read); haveResolved = true; } else @@ -2403,15 +2505,20 @@ 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()); + if (!promise->is_compatible(curr) || !promise->same_value(curr)) + continue; + + bool satisfy = true; + for (unsigned int j = 0; j < promise->get_num_readers(); j++) { + const ModelAction *act = promise->get_reader(j); + if (act->happens_before(curr) || + act->could_synchronize_with(curr)) { + satisfy = false; + break; + } } + if (satisfy) + curr->get_node()->set_promise(i); } } @@ -2420,13 +2527,17 @@ void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVec { 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; + if (!promise->thread_is_available(tid)) + continue; + for (unsigned int j = 0; j < promise->get_num_readers(); j++) { + const ModelAction *act = promise->get_reader(j); + if ((!old_cv || !old_cv->synchronized_since(act)) && + merge_cv->synchronized_since(act)) { + if (promise->eliminate_thread(tid)) { + /* Promise has failed */ + priv->failed_promise = true; + return; + } } } } @@ -2463,15 +2574,20 @@ void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check) 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)) + if (!promise->same_location(write)) continue; - if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) { - priv->failed_promise = true; - return; + for (unsigned int j = 0; j < promise->get_num_readers(); j++) { + const ModelAction *pread = promise->get_reader(j); + if (!pread->happens_before(act)) + continue; + if (mo_graph->checkPromise(write, promise)) { + priv->failed_promise = true; + return; + } + break; } // Don't do any lookups twice for the same thread @@ -2512,12 +2628,12 @@ void ModelChecker::compute_relseq_breakwrites(ModelAction *curr) /** * 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. + * from, as well as any previously-observed future values that must still be valid. + * * @param curr is the current ModelAction that we are exploring; it must be a * 'read' operation. */ -void ModelChecker::build_reads_from_past(ModelAction *curr) +void ModelChecker::build_may_read_from(ModelAction *curr) { std::vector *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location()); unsigned int i; @@ -2553,7 +2669,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) mo_graph->startChanges(); r_modification_order(curr, act); if (!is_infeasible()) - curr->get_node()->add_read_from(act); + curr->get_node()->add_read_from_past(act); mo_graph->rollbackChanges(); } @@ -2562,8 +2678,23 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) break; } } + + /* Inherit existing, promised future values */ + for (i = 0; i < promises->size(); i++) { + const Promise *promise = (*promises)[i]; + const ModelAction *promise_read = promise->get_reader(0); + if (promise_read->same_var(curr)) { + /* Only add feasible future-values */ + mo_graph->startChanges(); + r_modification_order(curr, promise); + if (!is_infeasible()) + curr->get_node()->add_read_from_promise(promise_read); + mo_graph->rollbackChanges(); + } + } + /* We may find no valid may-read-from only if the execution is doomed */ - if (!curr->get_node()->get_read_from_size()) { + if (!curr->get_node()->read_from_size()) { priv->no_valid_reads = true; set_assert(); } @@ -2571,9 +2702,9 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) 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"); + model_print("Printing read_from_past\n"); + curr->get_node()->print_read_from_past(); + model_print("End printing read_from_past\n"); } } @@ -2634,17 +2765,28 @@ void ModelChecker::dumpGraph(char *filename) const 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()); + ModelAction *act = *it; + if (act->is_read()) { + mo_graph->dot_print_node(file, act); + if (act->get_reads_from()) + mo_graph->dot_print_edge(file, + act->get_reads_from(), + act, + "label=\"rf\", color=red, weight=2"); + else + mo_graph->dot_print_edge(file, + act->get_reads_from_promise(), + act, + "label=\"rf\", color=red"); } - 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()); + if (thread_array[act->get_tid()]) { + mo_graph->dot_print_edge(file, + thread_array[id_to_int(act->get_tid())], + act, + "label=\"sb\", color=blue, weight=400"); } - thread_array[action->get_tid()] = action; + thread_array[act->get_tid()] = act; } fprintf(file, "}\n"); model_free(thread_array); @@ -2664,9 +2806,11 @@ void ModelChecker::print_summary() const #endif model_print("Execution %d:", stats.num_total); - if (isfeasibleprefix()) + if (isfeasibleprefix()) { + if (scheduler->all_threads_sleeping()) + model_print(" SLEEP-SET REDUNDANT"); model_print("\n"); - else + } else print_infeasibility(" INFEASIBLE"); print_list(action_trace); model_print("\n"); @@ -2712,6 +2856,26 @@ Thread * ModelChecker::get_thread(const ModelAction *act) const return get_thread(act->get_tid()); } +/** + * @brief Get a Promise's "promise number" + * + * A "promise number" is an index number that is unique to a promise, valid + * only for a specific snapshot of an execution trace. Promises may come and go + * as they are generated an resolved, so an index only retains meaning for the + * current snapshot. + * + * @param promise The Promise to check + * @return The promise index, if the promise still is valid; otherwise -1 + */ +int ModelChecker::get_promise_number(const Promise *promise) const +{ + for (unsigned int i = 0; i < promises->size(); i++) + if ((*promises)[i] == promise) + return i; + /* Not found */ + return -1; +} + /** * @brief Check if a Thread is currently enabled * @param t The Thread to check @@ -2815,7 +2979,7 @@ void ModelChecker::run() { do { thrd_t user_thread; - Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL); + Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL); add_thread(t); do {