X-Git-Url: http://plrg.eecs.uci.edu/git/?p=c11tester.git;a=blobdiff_plain;f=model.cc;h=0283911b6eea07e57c7b7266fe3c80fc2d755595;hp=6ded3f5d0ee1edeeb5f7b5e711a8f91396fd9523;hb=e2b556e7bb8b156ff1fe75e5d4c254bb3fc240c6;hpb=802e014ba228bb6bc689ff1d31e8423097be9826 diff --git a/model.cc b/model.cc index 6ded3f5d..0283911b 100644 --- a/model.cc +++ b/model.cc @@ -1,4 +1,5 @@ #include +#include #include "model.h" #include "action.h" @@ -9,6 +10,8 @@ #include "clockvector.h" #include "cyclegraph.h" #include "promise.h" +#include "datarace.h" +#include "mutex.h" #define INITIAL_THREAD_ID 0 @@ -18,26 +21,31 @@ ModelChecker *model; ModelChecker::ModelChecker(struct model_params params) : /* Initialize default scheduler */ scheduler(new Scheduler()), - /* First thread created will have id INITIAL_THREAD_ID */ - next_thread_id(INITIAL_THREAD_ID), - used_sequence_numbers(0), num_executions(0), + num_feasible_executions(0), params(params), - current_action(NULL), diverge(NULL), - nextThread(THREAD_ID_T_NONE), action_trace(new action_list_t()), thread_map(new HashTable()), obj_map(new HashTable()), + lock_waiters_map(new HashTable()), obj_thrd_map(new HashTable, uintptr_t, 4 >()), promises(new std::vector()), - lazy_sync_with_release(new HashTable, uintptr_t, 4>()), + futurevalues(new std::vector()), + lazy_sync_with_release(new HashTable()), thrd_last_action(new std::vector(1)), node_stack(new NodeStack()), - next_backtrack(NULL), mo_graph(new CycleGraph()), - failed_promise(false) + failed_promise(false), + too_many_reads(false), + asserted(false) { + /* Allocate this "size" on the snapshotting heap */ + 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; + + lazy_sync_size = &priv->lazy_sync_size; } /** @brief Destructor */ @@ -49,6 +57,7 @@ ModelChecker::~ModelChecker() delete obj_thrd_map; delete obj_map; + delete lock_waiters_map; delete action_trace; for (unsigned int i = 0; i < promises->size(); i++) @@ -71,68 +80,59 @@ void ModelChecker::reset_to_initial_state() { DEBUG("+++ Resetting to initial state +++\n"); node_stack->reset_execution(); - current_action = NULL; - next_thread_id = INITIAL_THREAD_ID; - used_sequence_numbers = 0; - nextThread = 0; - next_backtrack = NULL; failed_promise = false; + too_many_reads = false; + reset_asserted(); snapshotObject->backTrackBeforeStep(0); } -/** @returns a thread ID for a new Thread */ +/** @return a thread ID for a new Thread */ thread_id_t ModelChecker::get_next_id() { - return next_thread_id++; + return priv->next_thread_id++; } -/** @returns the number of user threads created during this execution */ +/** @return the number of user threads created during this execution */ int ModelChecker::get_num_threads() { - return next_thread_id; + return priv->next_thread_id; } -/** @returns a sequence number for a new ModelAction */ +/** @return a sequence number for a new ModelAction */ modelclock_t ModelChecker::get_next_seq_num() { - return ++used_sequence_numbers; + return ++priv->used_sequence_numbers; } /** - * Performs the "scheduling" for the model-checker. That is, it checks if the - * model-checker has selected a "next thread to run" and returns it, if - * available. This function should be called from the Scheduler routine, where - * the Scheduler falls back to a default scheduling routine if needed. + * @brief Choose the next thread to execute. * - * @return The next thread chosen by the model-checker. If the model-checker - * makes no selection, retuns NULL. + * This function chooses the next thread that should execute. It can force the + * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be + * followed by a THREAD_START, or it can enforce execution replay/backtracking. + * The model-checker may have no preference regarding the next thread (i.e., + * when exploring a new execution ordering), in which case this will return + * NULL. + * @param curr The current ModelAction. This action might guide the choice of + * next thread. + * @return The next thread to run. If the model-checker has no preference, NULL. */ -Thread * ModelChecker::schedule_next_thread() -{ - Thread *t; - if (nextThread == THREAD_ID_T_NONE) - return NULL; - t = thread_map->get(id_to_int(nextThread)); - - ASSERT(t != NULL); - - return t; -} - -/** - * Choose the next thread in the replay sequence. - * - * If the replay sequence has reached the 'diverge' point, returns a thread - * from the backtracking set. Otherwise, simply returns the next thread in the - * sequence that is being replayed. - */ -thread_id_t ModelChecker::get_next_replay_thread() +Thread * ModelChecker::get_next_thread(ModelAction *curr) { thread_id_t tid; + if (curr!=NULL) { + /* Do not split atomic actions. */ + if (curr->is_rmwr()) + return thread_current(); + /* The THREAD_CREATE action points to the created Thread */ + else if (curr->get_type() == THREAD_CREATE) + return (Thread *)curr->get_location(); + } + /* Have we completed exploring the preselected path? */ if (diverge == NULL) - return THREAD_ID_T_NONE; + return NULL; /* Else, we are trying to replay an execution */ ModelAction *next = node_stack->get_next()->get_action(); @@ -164,7 +164,8 @@ thread_id_t ModelChecker::get_next_replay_thread() tid = next->get_tid(); } DEBUG("*** ModelChecker chose next thread = %d ***\n", tid); - return tid; + ASSERT(tid != THREAD_ID_T_NONE); + return thread_map->get(id_to_int(tid)); } /** @@ -179,11 +180,13 @@ bool ModelChecker::next_execution() DBG(); num_executions++; + if (isfinalfeasible()) + num_feasible_executions++; if (isfinalfeasible() || DBG_ENABLED()) print_summary(); - if ((diverge = model->get_next_backtrack()) == NULL) + if ((diverge = get_next_backtrack()) == NULL) return false; if (DBG_ENABLED()) { @@ -191,64 +194,102 @@ bool ModelChecker::next_execution() diverge->print(); } - model->reset_to_initial_state(); + reset_to_initial_state(); return true; } ModelAction * ModelChecker::get_last_conflict(ModelAction *act) { - action_type type = act->get_type(); - - switch (type) { - case ATOMIC_READ: - case ATOMIC_WRITE: - case ATOMIC_RMW: - break; - default: - return NULL; + switch (act->get_type()) { + case ATOMIC_READ: + case ATOMIC_WRITE: + case ATOMIC_RMW: { + /* linear search: from most recent to oldest */ + action_list_t *list = obj_map->get_safe_ptr(act->get_location()); + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *prev = *rit; + if (act->is_synchronizing(prev)) + return prev; + } + break; } - /* linear search: from most recent to oldest */ - action_list_t *list = obj_map->get_safe_ptr(act->get_location()); - action_list_t::reverse_iterator rit; - for (rit = list->rbegin(); rit != list->rend(); rit++) { - ModelAction *prev = *rit; - if (act->is_synchronizing(prev)) - return prev; + case ATOMIC_LOCK: + case ATOMIC_TRYLOCK: { + /* linear search: from most recent to oldest */ + action_list_t *list = obj_map->get_safe_ptr(act->get_location()); + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *prev = *rit; + if (act->is_conflicting_lock(prev)) + return prev; + } + break; + } + case ATOMIC_UNLOCK: { + /* linear search: from most recent to oldest */ + action_list_t *list = obj_map->get_safe_ptr(act->get_location()); + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *prev = *rit; + if (!act->same_thread(prev)&&prev->is_failed_trylock()) + return prev; + } + break; + } + default: + break; } return NULL; } +/** This method find backtracking points where we should try to + * reorder the parameter ModelAction against. + * + * @param the ModelAction to find backtracking points for. + */ + + void ModelChecker::set_backtracking(ModelAction *act) { - ModelAction *prev; - Node *node; - Thread *t = get_thread(act->get_tid()); - - prev = get_last_conflict(act); + Thread *t = get_thread(act); + ModelAction * prev = get_last_conflict(act); if (prev == NULL) return; - node = prev->get_node()->get_parent(); + Node * node = prev->get_node()->get_parent(); + + int low_tid, high_tid; + if (node->is_enabled(t)) { + low_tid = id_to_int(act->get_tid()); + high_tid = low_tid+1; + } else { + low_tid = 0; + high_tid = get_num_threads(); + } - while (!node->is_enabled(t)) - t = t->get_parent(); + for(int i = low_tid; i < high_tid; i++) { + thread_id_t tid = int_to_id(i); + if (!node->is_enabled(tid)) + continue; - /* Check if this has been explored already */ - if (node->has_been_explored(t->get_id())) - return; + /* Check if this has been explored already */ + if (node->has_been_explored(tid)) + continue; - /* Cache the latest backtracking point */ - if (!next_backtrack || *prev > *next_backtrack) - next_backtrack = prev; + /* Cache the latest backtracking point */ + if (!priv->next_backtrack || *prev > *priv->next_backtrack) + priv->next_backtrack = prev; - /* If this is a new backtracking point, mark the tree */ - if (!node->set_backtrack(t->get_id())) - return; - DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n", - prev->get_tid(), t->get_id()); - if (DBG_ENABLED()) { - prev->print(); - act->print(); + /* If this is a new backtracking point, mark the tree */ + if (!node->set_backtrack(tid)) + continue; + DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n", + prev->get_tid(), t->get_id()); + if (DBG_ENABLED()) { + prev->print(); + act->print(); + } } } @@ -259,127 +300,412 @@ void ModelChecker::set_backtracking(ModelAction *act) */ ModelAction * ModelChecker::get_next_backtrack() { - ModelAction *next = next_backtrack; - next_backtrack = NULL; + ModelAction *next = priv->next_backtrack; + priv->next_backtrack = NULL; return next; } -void ModelChecker::check_current_action(void) +/** + * Processes a read or rmw 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) { - ModelAction *curr = this->current_action; - bool already_added = false; - this->current_action = NULL; - if (!curr) { - DEBUG("trying to push NULL action...\n"); - return; + uint64_t value; + 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; + + if (!second_part_of_rmw) { + check_recency(curr); + r_status = r_modification_order(curr, reads_from); + } + + + if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) { + mo_graph->rollbackChanges(); + too_many_reads = false; + continue; + } + + curr->read_from(reads_from); + mo_graph->commitChanges(); + updated |= r_status; + } else if (!second_part_of_rmw) { + /* Read from future value */ + value = curr->get_node()->get_future_value(); + modelclock_t expiration = curr->get_node()->get_future_value_expiration(); + curr->read_from(NULL); + Promise *valuepromise = new Promise(curr, value, expiration); + promises->push_back(valuepromise); + } + get_thread(curr)->set_return_value(value); + return updated; + } +} + +/** + * Processes a lock, trylock, or unlock model action. @param curr is + * the read model action to process. + * + * The try lock operation checks whether the lock is taken. If not, + * it falls to the normal lock operation case. If so, it returns + * fail. + * + * The lock operation has already been checked that it is enabled, so + * it just grabs the lock and synchronizes with the previous unlock. + * + * The unlock operation has to re-enable all of the threads that are + * waiting on the lock. + */ +void ModelChecker::process_mutex(ModelAction *curr) { + std::mutex *mutex = (std::mutex *)curr->get_location(); + struct std::mutex_state *state = mutex->get_state(); + switch (curr->get_type()) { + case ATOMIC_TRYLOCK: { + bool success = !state->islocked; + curr->set_try_lock(success); + if (!success) { + get_thread(curr)->set_return_value(0); + break; + } + get_thread(curr)->set_return_value(1); + } + //otherwise fall into the lock case + case ATOMIC_LOCK: { + if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock) { + printf("Lock access before initialization\n"); + set_assert(); + } + state->islocked = true; + ModelAction *unlock = get_last_unlock(curr); + //synchronize with the previous unlock statement + if (unlock != NULL) + curr->synchronize_with(unlock); + break; + } + case ATOMIC_UNLOCK: { + //unlock the lock + state->islocked = false; + //wake up the other threads + action_list_t *waiters = lock_waiters_map->get_safe_ptr(curr->get_location()); + //activate all the waiting threads + for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) { + scheduler->add_thread(get_thread((*rit)->get_tid())); + } + waiters->clear(); + break; + } + default: + ASSERT(0); } +} + +/** + * Process a write ModelAction + * @param curr The ModelAction to process + * @return True if the mo_graph was updated or promises were resolved + */ +bool ModelChecker::process_write(ModelAction *curr) +{ + bool updated_mod_order = w_modification_order(curr); + bool updated_promises = resolve_promises(curr); + + if (promises->size() == 0) { + for (unsigned int i = 0; i < futurevalues->size(); i++) { + struct PendingFutureValue pfv = (*futurevalues)[i]; + if (pfv.act->get_node()->add_future_value(pfv.value, pfv.expiration) && + (!priv->next_backtrack || *pfv.act > *priv->next_backtrack)) + priv->next_backtrack = pfv.act; + } + futurevalues->resize(0); + } + + mo_graph->commitChanges(); + get_thread(curr)->set_return_value(VALUE_NONE); + return updated_mod_order || updated_promises; +} + +/** + * 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 + * @return The current action, as processed by the ModelChecker. Is only the + * same as the parameter @a curr if this is a newly-explored action. + */ +ModelAction * ModelChecker::initialize_curr_action(ModelAction *curr) +{ + ModelAction *newcurr; if (curr->is_rmwc() || curr->is_rmw()) { - ModelAction *tmp = process_rmw(curr); - already_added = true; + newcurr = process_rmw(curr); delete curr; - curr = tmp; + compute_promises(newcurr); + return newcurr; + } + + newcurr = node_stack->explore_action(curr, scheduler->get_enabled()); + 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; + + /* If we have diverged, we need to reset the clock vector. */ + if (diverge == NULL) + newcurr->create_cv(get_parent_action(newcurr->get_tid())); } else { - ModelAction *tmp = node_stack->explore_action(curr); - if (tmp) { - /* Discard duplicate ModelAction; use action from NodeStack */ - /* First restore type and order in case of RMW operation */ - if (curr->is_rmwr()) - tmp->copy_typeandorder(curr); - - /* If we have diverged, we need to reset the clock vector. */ - if (diverge == NULL) - tmp->create_cv(get_parent_action(tmp->get_tid())); - - delete curr; - curr = tmp; - } else { - /* - * Perform one-time actions when pushing new ModelAction onto - * NodeStack - */ - curr->create_cv(get_parent_action(curr->get_tid())); - /* Build may_read_from set */ - if (curr->is_read()) - build_reads_from_past(curr); - if (curr->is_write()) - compute_promises(curr); + newcurr = curr; + /* + * Perform one-time actions when pushing new ModelAction onto + * NodeStack + */ + curr->create_cv(get_parent_action(curr->get_tid())); + if (curr->is_write()) + compute_promises(curr); + } + return newcurr; +} + +/** + * This method checks whether a model action is enabled at the given point. + * At this point, it checks whether a lock operation would be successful at this point. + * If not, it puts the thread 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 + lock_waiters_map->get_safe_ptr(curr->get_location())->push_back(curr); + return false; } } - /* Assign 'creation' parent */ - if (curr->get_type() == THREAD_CREATE) { + 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 next Thread that must be executed. May be NULL if ModelChecker + * makes no choice (e.g., according to replay execution, combining RMW actions, + * etc.) + */ +Thread * ModelChecker::check_current_action(ModelAction *curr) +{ + ASSERT(curr); + + bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw(); + + if (!check_action_enabled(curr)) { + //we'll make the execution look like we chose to run this action + //much later...when a lock is actually available to relese + get_current_thread()->set_pending(curr); + remove_thread(get_current_thread()); + return get_next_thread(NULL); + } + + ModelAction *newcurr = initialize_curr_action(curr); + + /* Add the action to lists before any other model-checking tasks */ + if (!second_part_of_rmw) + add_action_to_lists(newcurr); + + /* Build may_read_from set for newly-created actions */ + if (curr == newcurr && curr->is_read()) + build_reads_from_past(curr); + curr = newcurr; + + /* Thread specific actions */ + switch (curr->get_type()) { + case THREAD_CREATE: { Thread *th = (Thread *)curr->get_location(); th->set_creation(curr); + break; } - - /* Deal with new thread */ - if (curr->get_type() == THREAD_START) + case THREAD_JOIN: { + Thread *waiting, *blocking; + waiting = get_thread(curr); + blocking = (Thread *)curr->get_location(); + if (!blocking->is_complete()) { + blocking->push_wait_list(curr); + scheduler->sleep(waiting); + } else { + do_complete_join(curr); + } + break; + } + case THREAD_FINISH: { + Thread *th = get_thread(curr); + while (!th->wait_list_empty()) { + ModelAction *act = th->pop_wait_list(); + Thread *wake = get_thread(act); + scheduler->wake(wake); + do_complete_join(act); + } + th->complete(); + break; + } + case THREAD_START: { check_promises(NULL, curr->get_cv()); + break; + } + default: + break; + } - /* Assign reads_from values */ - Thread *th = get_thread(curr->get_tid()); - uint64_t value = VALUE_NONE; - bool updated = false; - if (curr->is_read()) { - const ModelAction *reads_from = curr->get_node()->get_read_from(); - if (reads_from != NULL) { - value = reads_from->get_value(); - /* Assign reads_from, perform release/acquire synchronization */ - curr->read_from(reads_from); - if (r_modification_order(curr,reads_from)) + work_queue_t work_queue(1, CheckCurrWorkEntry(curr)); + + while (!work_queue.empty()) { + WorkQueueEntry work = work_queue.front(); + work_queue.pop_front(); + + switch (work.type) { + case WORK_CHECK_CURR_ACTION: { + ModelAction *act = work.action; + bool updated = false; + if (act->is_read() && process_read(act, second_part_of_rmw)) updated = true; - } else { - /* Read from future value */ - value = curr->get_node()->get_future_value(); - curr->read_from(NULL); - Promise *valuepromise = new Promise(curr, value); - promises->push_back(valuepromise); + + if (act->is_write() && process_write(act)) + updated = true; + + if (act->is_mutex_op()) + process_mutex(act); + + if (updated) + work_queue.push_back(CheckRelSeqWorkEntry(act->get_location())); + break; } - } else if (curr->is_write()) { - if (w_modification_order(curr)) - updated = true;; - if (resolve_promises(curr)) - updated = true; - } + 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()) { + if (r_modification_order(act, act->get_reads_from())) + updated = true; + } + if (act->is_write()) { + if (w_modification_order(act)) + updated = true; + } - if (updated) - resolve_release_sequences(curr->get_location()); + if (updated) + work_queue.push_back(CheckRelSeqWorkEntry(act->get_location())); + break; + } + default: + ASSERT(false); + break; + } + } - th->set_return_value(value); + check_curr_backtracking(curr); - /* Add action to list. */ - if (!already_added) - add_action_to_lists(curr); + set_backtracking(curr); - /** @todo Is there a better interface for setting the next thread rather - than this field/convoluted approach? Perhaps like just returning - it or something? */ + return get_next_thread(curr); +} - /* Do not split atomic actions. */ - if (curr->is_rmwr()) - nextThread = thread_current()->get_id(); - else - nextThread = get_next_replay_thread(); +/** + * Complete a THREAD_JOIN operation, by synchronizing with the THREAD_FINISH + * operation from the Thread it is joining with. Must be called after the + * completion of the Thread in question. + * @param join The THREAD_JOIN action + */ +void ModelChecker::do_complete_join(ModelAction *join) +{ + Thread *blocking = (Thread *)join->get_location(); + ModelAction *act = get_last_action(blocking->get_id()); + join->synchronize_with(act); +} +void ModelChecker::check_curr_backtracking(ModelAction * curr) { Node *currnode = curr->get_node(); Node *parnode = currnode->get_parent(); - if (!parnode->backtrack_empty() || !currnode->read_from_empty() || - !currnode->future_value_empty() || !currnode->promise_empty()) - if (!next_backtrack || *curr > *next_backtrack) - next_backtrack = curr; + if ((!parnode->backtrack_empty() || + !currnode->read_from_empty() || + !currnode->future_value_empty() || + !currnode->promise_empty()) + && (!priv->next_backtrack || + *curr > *priv->next_backtrack)) { + priv->next_backtrack = curr; + } +} - set_backtracking(curr); +bool ModelChecker::promises_expired() { + for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) { + Promise *promise = (*promises)[promise_index]; + if (promise->get_expiration()used_sequence_numbers) { + return true; + } + } + return false; +} + +/** @return whether the current partial trace must be a prefix of a + * feasible trace. */ +bool ModelChecker::isfeasibleprefix() { + return promises->size() == 0 && *lazy_sync_size == 0; } -/** @returns whether the current partial trace is feasible. */ +/** @return whether the current partial trace is feasible. */ bool ModelChecker::isfeasible() { - return !mo_graph->checkForCycles() && !failed_promise; + return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW(); +} + +/** @return whether the current partial trace is feasible other than + * multiple RMW reading from the same store. */ +bool ModelChecker::isfeasibleotherthanRMW() { + if (DBG_ENABLED()) { + if (mo_graph->checkForCycles()) + DEBUG("Infeasible: modification order cycles\n"); + if (failed_promise) + DEBUG("Infeasible: failed promise\n"); + if (too_many_reads) + DEBUG("Infeasible: too many reads\n"); + if (promises_expired()) + DEBUG("Infeasible: promises expired\n"); + } + return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !promises_expired(); } /** Returns whether the current completed trace is feasible. */ bool ModelChecker::isfinalfeasible() { + if (DBG_ENABLED() && promises->size() != 0) + DEBUG("Infeasible: unrevolved promises\n"); + return isfeasible() && promises->size() == 0; } @@ -388,13 +714,120 @@ ModelAction * ModelChecker::process_rmw(ModelAction *act) { int tid = id_to_int(act->get_tid()); ModelAction *lastread = get_last_action(tid); lastread->process_rmw(act); - if (act->is_rmw()) + if (act->is_rmw() && lastread->get_reads_from()!=NULL) { mo_graph->addRMWEdge(lastread->get_reads_from(), lastread); + mo_graph->commitChanges(); + } return lastread; } /** - * Updates the mo_graph with the constraints imposed from the current read. + * 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) { + 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 (!isfeasible()) + return; + + std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(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() != curr->get_reads_from()) + return; + if (act->get_node()->get_read_from_size() <= 1) + return; + } + + for (int i = 0; iget_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==curr->get_reads_from()) + continue; + + /* Test to see whether this is a feasible write to read from*/ + mo_graph->startChanges(); + r_modification_order(curr, write); + bool feasiblereadfrom = isfeasible(); + mo_graph->rollbackChanges(); + + if (!feasiblereadfrom) + continue; + 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; jget_node()->get_read_from_size(); j++) { + if (act->get_node()->get_read_from_at(i)==write) { + foundvalue = true; + break; + } + } + if (!foundvalue) { + feasiblewrite = false; + break; + } + } + if (feasiblewrite) { + 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 lastest 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 action that curr reads from. Must be a write. * @return True if modification order edges were added; false otherwise @@ -414,17 +847,22 @@ bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf for (rit = list->rbegin(); rit != list->rend(); rit++) { ModelAction *act = *rit; - /* Include at most one act per-thread that "happens before" curr */ - if (act->happens_before(curr)) { - if (act->is_read()) { + /* + * 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 (rf != act) { + mo_graph->addEdge(act, rf); + added = true; + } + } else { const ModelAction *prevreadfrom = act->get_reads_from(); if (prevreadfrom != NULL && rf != prevreadfrom) { mo_graph->addEdge(prevreadfrom, rf); added = true; } - } else if (rf != act) { - mo_graph->addEdge(act, rf); - added = true; } break; } @@ -434,7 +872,22 @@ bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf return added; } -/** Updates the mo_graph with the constraints imposed from the current read. */ +/** This method fixes up the modification order when we resolve a + * promises. The basic problem is that actions that occur after the + * read curr could not property add items to the modification order + * for our read. + * + * So for each thread, we find the earliest item that happens after + * the read curr. This is the item we have to fix up with additional + * constraints. If that action is write, we add a MO edge between + * the Action rf and that action. If the action is a read, we add a + * MO edge between the Action rf, and whatever the read accessed. + * + * @param curr is the read ModelAction that we are fixing up MO edges for. + * @param rf is the write ModelAction that curr reads from. + * + */ + void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf) { std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location()); @@ -473,6 +926,23 @@ void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelActio /** * 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 */ @@ -486,7 +956,7 @@ bool ModelChecker::w_modification_order(ModelAction *curr) 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(curr->get_location()); + ModelAction *last_seq_cst = get_last_seq_cst(curr); if (last_seq_cst != NULL) { mo_graph->addEdge(last_seq_cst, curr); added = true; @@ -500,13 +970,34 @@ bool ModelChecker::w_modification_order(ModelAction *curr) action_list_t::reverse_iterator rit; for (rit = list->rbegin(); rit != list->rend(); rit++) { ModelAction *act = *rit; + if (act == curr) { + /* + * If RMW, we already have all relevant edges, + * so just skip to next thread. + * If normal write, we need to look at earlier + * actions, so continue processing list. + */ + if (curr->is_rmw()) + break; + else + continue; + } - /* Include at most one act per-thread that "happens before" curr */ + /* + * Include at most one act per-thread that "happens + * before" curr + */ if (act->happens_before(curr)) { - if (act->is_read()) - mo_graph->addEdge(act->get_reads_from(), curr); - else + /* + * 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()) mo_graph->addEdge(act, curr); + else if (act->is_read() && act->get_reads_from() != NULL) + mo_graph->addEdge(act->get_reads_from(), curr); added = true; break; } else if (act->is_read() && !act->is_synchronizing(curr) && @@ -519,9 +1010,13 @@ bool ModelChecker::w_modification_order(ModelAction *curr) => that read could potentially read from our write. */ - if (act->get_node()->add_future_value(curr->get_value()) && - (!next_backtrack || *act > *next_backtrack)) - next_backtrack = act; + if (thin_air_constraint_may_allow(curr, act)) { + if (isfeasible() || + (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && isfeasibleotherthanRMW())) { + struct PendingFutureValue pfv = {curr->get_value(),curr->get_seq_number()+params.maxfuturedelay,act}; + futurevalues->push_back(pfv); + } + } } } } @@ -529,6 +1024,28 @@ bool ModelChecker::w_modification_order(ModelAction *curr) 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; +} + /** * Finds the head(s) of the release sequence(s) containing a given ModelAction. * The ModelAction under consideration is expected to be taking part in @@ -550,18 +1067,23 @@ bool ModelChecker::w_modification_order(ModelAction *curr) * @return true, if the ModelChecker is certain that release_heads is complete; * false otherwise */ -bool ModelChecker::release_seq_head(const ModelAction *rf, - std::vector *release_heads) const +bool ModelChecker::release_seq_head(const ModelAction *rf, rel_heads_list_t *release_heads) const { - ASSERT(rf->is_write()); if (!rf) { /* read from future: need to settle this later */ return false; /* incomplete */ } + + ASSERT(rf->is_write()); + if (rf->is_release()) release_heads->push_back(rf); if (rf->is_rmw()) { - if (rf->is_acquire()) + /* We need a RMW action that is both an acquire and release to stop */ + /** @todo Need to be smarter here... In the linux lock + * example, this will run to the beginning of the program for + * every acquire. */ + if (rf->is_acquire() && rf->is_release()) return true; /* complete */ return release_seq_head(rf->get_reads_from(), release_heads); } @@ -576,9 +1098,8 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, action_list_t::const_reverse_iterator rit; /* Find rf in the thread list */ - for (rit = list->rbegin(); rit != list->rend(); rit++) - if (*rit == rf) - break; + rit = std::find(list->rbegin(), list->rend(), rf); + ASSERT(rit != list->rend()); /* Find the last write/release */ for (; rit != list->rend(); rit++) @@ -597,20 +1118,35 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, 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)); + if (last && rf->happens_before(last)) + future_ordered = true; + for (rit = list->rbegin(); rit != list->rend(); rit++) { const ModelAction *act = *rit; - if (!act->is_write()) - continue; /* Reach synchronization -> this thread is complete */ if (act->happens_before(release)) break; - if (rf->happens_before(act)) + if (rf->happens_before(act)) { + future_ordered = true; + continue; + } + + /* Only writes can break release sequences */ + if (!act->is_write()) continue; /* Check modification order */ - if (mo_graph->checkReachable(rf, act)) + if (mo_graph->checkReachable(rf, act)) { /* rf --mo--> act */ + future_ordered = true; continue; + } if (mo_graph->checkReachable(act, release)) /* act --mo--> release */ break; @@ -621,6 +1157,8 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, } certain = false; } + if (!future_ordered) + return false; /* This thread is uncertain */ } if (certain) @@ -640,17 +1178,17 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, * with the head(s) of the release sequence(s), if they exists with certainty. * @see ModelChecker::release_seq_head */ -void ModelChecker::get_release_seq_heads(ModelAction *act, - std::vector *release_heads) +void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads) { const ModelAction *rf = act->get_reads_from(); bool complete; complete = release_seq_head(rf, release_heads); if (!complete) { /* add act to 'lazy checking' list */ - std::list *list; + action_list_t *list; list = lazy_sync_with_release->get_safe_ptr(act->get_location()); list->push_back(act); + (*lazy_sync_size)++; } } @@ -662,21 +1200,24 @@ void ModelChecker::get_release_seq_heads(ModelAction *act, * * @param location The location/object that should be checked for release * sequence resolutions - * @return True if any updates occurred (new synchronization, new mo_graph edges) + * @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) +bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue) { - std::list *list; + action_list_t *list; list = lazy_sync_with_release->getptr(location); if (!list) return false; bool updated = false; - std::list::iterator it = list->begin(); + action_list_t::iterator it = list->begin(); while (it != list->end()) { ModelAction *act = *it; const ModelAction *rf = act->get_reads_from(); - std::vector release_heads; + rel_heads_list_t release_heads; bool complete; complete = release_seq_head(rf, &release_heads); for (unsigned int i = 0; i < release_heads.size(); i++) { @@ -687,22 +1228,32 @@ bool ModelChecker::resolve_release_sequences(void *location) } if (updated) { + /* Re-check act for mo_graph edges */ + work_queue->push_back(MOEdgeWorkEntry(act)); + /* propagate synchronization to later actions */ action_list_t::reverse_iterator it = action_trace->rbegin(); - while ((*it) != act) { + for (; (*it) != act; it++) { ModelAction *propagate = *it; - if (act->happens_before(propagate)) - /** @todo new mo_graph edges along with - * this synchronization? */ + if (act->happens_before(propagate)) { propagate->synchronize_with(act); + /* Re-check 'propagate' for mo_graph edges */ + work_queue->push_back(MOEdgeWorkEntry(propagate)); + } } } - if (complete) + if (complete) { it = list->erase(it); - else + (*lazy_sync_size)--; + } else it++; } + // If we resolved promises or data races, see if we have realized a data race. + if (checkDataRaces()) { + set_assert(); + } + return updated; } @@ -722,7 +1273,7 @@ void ModelChecker::add_action_to_lists(ModelAction *act) std::vector *vec = obj_thrd_map->get_safe_ptr(act->get_location()); if (tid >= (int)vec->size()) - vec->resize(next_thread_id); + vec->resize(priv->next_thread_id); (*vec)[tid].push_back(act); if ((int)thrd_last_action->size() <= tid) @@ -730,27 +1281,56 @@ void ModelChecker::add_action_to_lists(ModelAction *act) (*thrd_last_action)[tid] = act; } -ModelAction * ModelChecker::get_last_action(thread_id_t tid) +/** + * @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 nthreads = get_num_threads(); - if ((int)thrd_last_action->size() < nthreads) - thrd_last_action->resize(nthreads); - return (*thrd_last_action)[id_to_int(tid)]; + int threadid = id_to_int(tid); + if (threadid < (int)thrd_last_action->size()) + return (*thrd_last_action)[id_to_int(tid)]; + else + return NULL; } /** - * Gets the last memory_order_seq_cst action (in the total global sequence) - * performed on a particular object (i.e., memory location). - * @param location The object location to check - * @return The last seq_cst action performed + * 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(const void *location) +ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const { + void *location = curr->get_location(); action_list_t *list = obj_map->get_safe_ptr(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()) + if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr) + 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 = obj_map->get_safe_ptr(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()) return *rit; return NULL; } @@ -782,12 +1362,20 @@ ClockVector * ModelChecker::get_cv(thread_id_t tid) bool ModelChecker::resolve_promises(ModelAction *write) { bool resolved = false; + 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->read_from(write); + if (read->is_rmw()) { + mo_graph->addRMWEdge(write, read); + } + //First fix up the modification order for actions that happened + //before the read r_modification_order(read, write); + //Next fix up the modification order for actions that happened + //after the read. post_r_modification_order(read, write); promises->erase(promises->begin() + promise_index); resolved = true; @@ -828,7 +1416,7 @@ void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv) merge_cv->synchronized_since(act)) { //This thread is no longer able to send values back to satisfy the promise int num_synchronized_threads = promise->increment_threads(); - if (num_synchronized_threads == model->get_num_threads()) { + if (num_synchronized_threads == get_num_threads()) { //Promise has failed failed_promise = true; return; @@ -856,7 +1444,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) bool initialized = false; if (curr->is_seqcst()) { - last_seq_cst = get_last_seq_cst(curr->get_location()); + last_seq_cst = get_last_seq_cst(curr); /* We have to at least see the last sequentially consistent write, so we are initialized. */ if (last_seq_cst != NULL) @@ -872,11 +1460,11 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) ModelAction *act = *rit; /* Only consider 'write' actions */ - if (!act->is_write()) + if (!act->is_write() || act == curr) continue; /* Don't consider more than one seq_cst write if we are a seq_cst read. */ - if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) { + if (!curr->is_seqcst() || (!act->is_seqcst() && (last_seq_cst == NULL || !act->happens_before(last_seq_cst))) || act == last_seq_cst) { DEBUG("Adding action to may_read_from:\n"); if (DBG_ENABLED()) { act->print(); @@ -926,9 +1514,15 @@ void ModelChecker::print_summary() { printf("\n"); printf("Number of executions: %d\n", num_executions); + printf("Number of feasible executions: %d\n", num_feasible_executions); printf("Total nodes created: %d\n", node_stack->get_total_nodes()); +#if SUPPORT_MOD_ORDER_DUMP scheduler->print(); + char buffername[100]; + sprintf(buffername, "exec%04u", num_executions); + mo_graph->dumpGraphToFile(buffername); +#endif if (!isfinalfeasible()) printf("INFEASIBLE EXECUTION!\n"); @@ -947,6 +1541,11 @@ void ModelChecker::add_thread(Thread *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); @@ -957,10 +1556,7 @@ void ModelChecker::remove_thread(Thread *t) * 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, although - * there is little reason to switch to the model-checker without an action to - * explore (note: act == NULL is sometimes used as a hack to allow a thread to - * yield control without performing any progress; see thrd_join()). + * @param act The current action that will be explored. Must not be NULL. * @return Return status from the 'swap' call (i.e., success/fail, 0/-1) */ int ModelChecker::switch_to_master(ModelAction *act) @@ -977,21 +1573,23 @@ int ModelChecker::switch_to_master(ModelAction *act) * @return Returns true (success) if a step was taken and false otherwise. */ bool ModelChecker::take_step() { - Thread *curr, *next; + if (has_asserted()) + return false; - curr = thread_current(); + Thread * curr = thread_current(); if (curr) { if (curr->get_state() == THREAD_READY) { - check_current_action(); - scheduler->add_thread(curr); - } else if (curr->get_state() == THREAD_RUNNING) { - /* Stopped while running; i.e., completed */ - curr->complete(); + ASSERT(priv->current_action); + + priv->nextThread = check_current_action(priv->current_action); + priv->current_action = NULL; + if (curr->is_blocked() || curr->is_complete()) + scheduler->remove_thread(curr); } else { ASSERT(false); } } - next = scheduler->next_thread(); + Thread * next = scheduler->next_thread(priv->nextThread); /* Infeasible -> don't take any more steps */ if (!isfeasible()) @@ -1004,6 +1602,15 @@ bool ModelChecker::take_step() { /* next == NULL -> don't take any more steps */ if (!next) return false; + + if ( next->get_pending() != NULL ) { + //restart a pending action + set_current_action(next->get_pending()); + next->set_pending(NULL); + next->set_state(THREAD_READY); + return true; + } + /* Return false only if swap fails with an error */ return (Thread::swap(&system_context, next) == 0); }