X-Git-Url: http://plrg.eecs.uci.edu/git/?p=model-checker.git;a=blobdiff_plain;f=model.cc;h=8d8944d71ab27e59af1108e2a66debd3d6999596;hp=ede3797b7f4933f1c16f0a054d8b558ef63baff1;hb=ec80014245d22f726e4d66a89b6bd6d293db177c;hpb=160c85908774dfffc19dc1b02f4f845a14c056af diff --git a/model.cc b/model.cc index ede3797..8d8944d 100644 --- a/model.cc +++ b/model.cc @@ -11,6 +11,8 @@ #include "cyclegraph.h" #include "promise.h" #include "datarace.h" +#include "mutex.h" +#include "threads.h" #define INITIAL_THREAD_ID 0 @@ -19,31 +21,32 @@ ModelChecker *model; /** @brief Constructor */ ModelChecker::ModelChecker(struct model_params params) : /* Initialize default scheduler */ + params(params), scheduler(new Scheduler()), num_executions(0), num_feasible_executions(0), - params(params), diverge(NULL), + earliest_diverge(NULL), 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()), futurevalues(new std::vector()), - lazy_sync_with_release(new HashTable, uintptr_t, 4>()), + pending_acq_rel_seq(new std::vector()), thrd_last_action(new std::vector(1)), node_stack(new NodeStack()), mo_graph(new CycleGraph()), failed_promise(false), too_many_reads(false), - asserted(false) + asserted(false), + bad_synchronization(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 */ @@ -55,13 +58,14 @@ 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++) delete (*promises)[i]; delete promises; - delete lazy_sync_with_release; + delete pending_acq_rel_seq; delete thrd_last_action; delete node_stack; @@ -79,23 +83,30 @@ void ModelChecker::reset_to_initial_state() node_stack->reset_execution(); failed_promise = false; too_many_reads = false; + bad_synchronization = 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 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 priv->next_thread_id; } -/** @returns a sequence number for a new ModelAction */ +/** @return The currently executing Thread. */ +Thread * ModelChecker::get_current_thread() +{ + return scheduler->get_current_thread(); +} + +/** @return a sequence number for a new ModelAction */ modelclock_t ModelChecker::get_next_seq_num() { return ++priv->used_sequence_numbers; @@ -118,12 +129,14 @@ Thread * ModelChecker::get_next_thread(ModelAction *curr) { thread_id_t tid; - /* 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(); + 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) @@ -133,6 +146,9 @@ Thread * ModelChecker::get_next_thread(ModelAction *curr) ModelAction *next = node_stack->get_next()->get_action(); if (next == diverge) { + if (earliest_diverge == NULL || *diverge < *earliest_diverge) + earliest_diverge=diverge; + Node *nextnode = next->get_node(); /* Reached divergence point */ if (nextnode->increment_promise()) { @@ -152,8 +168,12 @@ Thread * ModelChecker::get_next_thread(ModelAction *curr) Node *node = nextnode->get_parent(); tid = node->get_next_backtrack(); node_stack->pop_restofstack(1); + if (diverge==earliest_diverge) { + earliest_diverge=node->get_action(); + } } DEBUG("*** Divergence point ***\n"); + diverge = NULL; } else { tid = next->get_tid(); @@ -175,8 +195,20 @@ bool ModelChecker::next_execution() DBG(); num_executions++; - if (isfinalfeasible()) + + if (isfinalfeasible()) { + printf("Earliest divergence point since last feasible execution:\n"); + if (earliest_diverge) + earliest_diverge->print(false); + else + printf("(Not set)\n"); + + earliest_diverge = NULL; num_feasible_executions++; + } + + DEBUG("Number of acquires waiting on pending release sequences: %lu\n", + pending_acq_rel_seq->size()); if (isfinalfeasible() || DBG_ENABLED()) print_summary(); @@ -195,58 +227,108 @@ bool ModelChecker::next_execution() 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); - - prev = get_last_conflict(act); + ModelAction * prev = get_last_conflict(act); if (prev == NULL) return; - node = prev->get_node()->get_parent(); + Node * node = prev->get_node()->get_parent(); - while (!node->is_enabled(t)) - t = t->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(); + } - /* Check if this has been explored already */ - if (node->has_been_explored(t->get_id())) - return; + for(int i = low_tid; i < high_tid; i++) { + thread_id_t tid = int_to_id(i); + if (!node->is_enabled(tid)) + continue; - /* Cache the latest backtracking point */ - if (!priv->next_backtrack || *prev > *priv->next_backtrack) - priv->next_backtrack = prev; + /* Check if this has been explored already */ + if (node->has_been_explored(tid)) + continue; - /* 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(); + /* See if fairness allows */ + if (model->params.fairwindow != 0 && !node->has_priority(tid)) { + bool unfair=false; + for(int t=0;tget_num_threads();t++) { + thread_id_t tother=int_to_id(t); + if (node->is_enabled(tother) && node->has_priority(tother)) { + unfair=true; + break; + } + } + if (unfair) + continue; + } + + /* 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(tid)) + continue; + DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n", + prev->get_tid(), t->get_id()); + if (DBG_ENABLED()) { + prev->print(); + act->print(); + } } } @@ -281,7 +363,7 @@ bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw) bool r_status = false; if (!second_part_of_rmw) { - check_recency(curr,false); + check_recency(curr, reads_from); r_status = r_modification_order(curr, reads_from); } @@ -308,6 +390,68 @@ bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw) } } +/** + * 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. + * + * @return True if synchronization was updated; false otherwise + */ +bool 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); + return true; + } + 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->wake(get_thread(*rit)); + } + waiters->clear(); + break; + } + default: + ASSERT(0); + } + return false; +} + /** * Process a write ModelAction * @param curr The ModelAction to process @@ -319,7 +463,7 @@ bool ModelChecker::process_write(ModelAction *curr) bool updated_promises = resolve_promises(curr); if (promises->size() == 0) { - for (unsigned int i = 0; isize(); i++) { + 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)) @@ -334,58 +478,20 @@ bool ModelChecker::process_write(ModelAction *curr) } /** - * 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. + * @brief Process the current action for thread-related activity * - * @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.) + * Performs current-action processing for a THREAD_* ModelAction. Proccesses + * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN + * synchronization, etc. This function is a no-op for non-THREAD actions + * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.) + * + * @param curr The current action + * @return True if synchronization was updated or a thread completed */ -Thread * ModelChecker::check_current_action(ModelAction *curr) +bool ModelChecker::process_thread_action(ModelAction *curr) { - bool second_part_of_rmw = false; - - ASSERT(curr); - - if (curr->is_rmwc() || curr->is_rmw()) { - ModelAction *tmp = process_rmw(curr); - second_part_of_rmw = true; - delete curr; - curr = tmp; - compute_promises(curr); - } else { - ModelAction *tmp = node_stack->explore_action(curr, NULL); - 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); - } - } + bool updated = false; - /* Thread specific actions */ switch (curr->get_type()) { case THREAD_CREATE: { Thread *th = (Thread *)curr->get_location(); @@ -399,6 +505,9 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) if (!blocking->is_complete()) { blocking->push_wait_list(curr); scheduler->sleep(waiting); + } else { + do_complete_join(curr); + updated = true; /* trigger rel-seq checks */ } break; } @@ -408,8 +517,11 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) ModelAction *act = th->pop_wait_list(); Thread *wake = get_thread(act); scheduler->wake(wake); + do_complete_join(act); + updated = true; /* trigger rel-seq checks */ } th->complete(); + updated = true; /* trigger rel-seq checks */ break; } case THREAD_START: { @@ -420,6 +532,123 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) break; } + return updated; +} + +/** + * 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()) { + newcurr = process_rmw(curr); + delete curr; + + if (newcurr->is_rmw()) + compute_promises(newcurr); + return newcurr; + } + + curr->set_seq_number(get_next_seq_num()); + + 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; + + /* Always compute new clock vector */ + newcurr->create_cv(get_parent_action(newcurr->get_tid())); + } else { + newcurr = curr; + + /* Always compute new clock vector */ + newcurr->create_cv(get_parent_action(newcurr->get_tid())); + /* + * Perform one-time actions when pushing new ModelAction onto + * NodeStack + */ + if (newcurr->is_write()) + compute_promises(newcurr); + } + 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; + } + } + + 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)) { + /* Make the execution look like we chose to run this action + * much later, when a lock is actually available to release */ + get_current_thread()->set_pending(curr); + scheduler->sleep(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; + + /* Initialize work_queue with the "current action" work */ work_queue_t work_queue(1, CheckCurrWorkEntry(curr)); while (!work_queue.empty()) { @@ -429,32 +658,56 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) switch (work.type) { case WORK_CHECK_CURR_ACTION: { ModelAction *act = work.action; - bool updated = false; + 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)) - updated = true; + update = true; if (act->is_write() && process_write(act)) - updated = true; + update = true; - if (updated) + if (act->is_mutex_op() && process_mutex(act)) + update_all = true; + + 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 Perform follow-up mo_graph checks */ + 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(); + if (rf != NULL && r_modification_order(act, rf)) + 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; } } - /* Add action to list. */ - if (!second_part_of_rmw) - add_action_to_lists(curr); - check_curr_backtracking(curr); set_backtracking(curr); @@ -462,6 +715,19 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) return get_next_thread(curr); } +/** + * 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(); @@ -486,25 +752,43 @@ bool ModelChecker::promises_expired() { return false; } -/** @returns whether the current partial trace must be a prefix of a +/** @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; + return promises->size() == 0 && pending_acq_rel_seq->size() == 0; } -/** @returns whether the current partial trace is feasible. */ +/** @return whether the current partial trace is feasible. */ bool ModelChecker::isfeasible() { + if (DBG_ENABLED() && mo_graph->checkForRMWViolation()) + DEBUG("Infeasible: RMW violation\n"); + return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW(); } -/** @returns whether the current partial trace is feasible other than +/** @return whether the current partial trace is feasible other than * multiple RMW reading from the same store. */ bool ModelChecker::isfeasibleotherthanRMW() { - return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !promises_expired(); + 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 (bad_synchronization) + DEBUG("Infeasible: bad synchronization ordering\n"); + if (promises_expired()) + DEBUG("Infeasible: promises expired\n"); + } + return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !bad_synchronization && !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; } @@ -531,33 +815,29 @@ ModelAction * ModelChecker::process_rmw(ModelAction *act) { * * If so, we decide that the execution is no longer feasible. */ -void ModelChecker::check_recency(ModelAction *curr, bool already_added) { +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 (!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 */ - if (already_added) { - for (; (*rit) != curr; rit++) - ; - /* go past curr now */ - rit++; - } + 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 @@ -568,17 +848,18 @@ void ModelChecker::check_recency(ModelAction *curr, bool already_added) { ModelAction *act = *rit; if (!act->is_read()) return; - if (act->get_reads_from() != curr->get_reads_from()) + + if (act->get_reads_from() != rf) 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()) + if (write==rf) continue; /* Test to see whether this is a feasible write to read from*/ @@ -618,7 +899,7 @@ void ModelChecker::check_recency(ModelAction *curr, bool already_added) { /** * Updates the mo_graph with the constraints imposed from the current - * read. + * read. * * Basic idea is the following: Go through each other thread and find * the lastest action that happened before our read. Two cases: @@ -648,21 +929,27 @@ 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)) { + /* + * 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 && act != curr) { + if (rf != act) { mo_graph->addEdge(act, rf); added = true; } } else { const ModelAction *prevreadfrom = act->get_reads_from(); - if (prevreadfrom != NULL && rf != prevreadfrom) { + //if the previous read is unresolved, keep going... + if (prevreadfrom == NULL) + continue; + + if (rf != prevreadfrom) { mo_graph->addEdge(prevreadfrom, rf); added = true; } } - break; } } @@ -675,7 +962,7 @@ bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf * 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 @@ -686,7 +973,6 @@ bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf * @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()); @@ -700,10 +986,10 @@ void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelActio action_list_t::reverse_iterator rit; ModelAction *lastact = NULL; - /* Find last action that happens after curr */ + /* Find last action that happens after curr that is either not curr or a rmw */ for (rit = list->rbegin(); rit != list->rend(); rit++) { ModelAction *act = *rit; - if (curr->happens_before(act)) { + if (curr->happens_before(act) && (curr != act || curr->is_rmw())) { lastact = act; } else break; @@ -711,12 +997,25 @@ void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelActio /* Include at most one act per-thread that "happens before" curr */ if (lastact != NULL) { - if (lastact->is_read()) { + if (lastact==curr) { + //Case 1: The resolved read is a RMW, and we need to make sure + //that the write portion of the RMW mod order after rf + + mo_graph->addEdge(rf, lastact); + } else if (lastact->is_read()) { + //Case 2: The resolved read is a normal read and the next + //operation is a read, and we need to make sure the value read + //is mod ordered after rf + const ModelAction *postreadfrom = lastact->get_reads_from(); if (postreadfrom != NULL&&rf != postreadfrom) mo_graph->addEdge(rf, postreadfrom); - } else if (rf != lastact) { - mo_graph->addEdge(rf, lastact); + } else { + //Case 3: The resolved read is a normal read and the next + //operation is a write, and we need to make sure that the + //write is mod ordered after rf + if (lastact!=rf) + mo_graph->addEdge(rf, lastact); } break; } @@ -755,7 +1054,7 @@ 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; @@ -769,8 +1068,31 @@ 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) { + /* + * 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; + } - /* 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)) { /* * Note: if act is RMW, just add edge: @@ -778,12 +1100,14 @@ bool ModelChecker::w_modification_order(ModelAction *curr) * The following edge should be handled elsewhere: * readfrom(act) --mo--> act */ - if (act->is_write()) { - //RMW shouldn't have an edge to themselves - if (act!=curr) - mo_graph->addEdge(act, curr); - } else if (act->is_read() && act->get_reads_from() != NULL) + if (act->is_write()) + mo_graph->addEdge(act, curr); + else if (act->is_read()) { + //if previous read accessed a null, just keep going + if (act->get_reads_from() == NULL) + continue; mo_graph->addEdge(act->get_reads_from(), curr); + } added = true; break; } else if (act->is_read() && !act->is_synchronizing(curr) && @@ -798,7 +1122,7 @@ bool ModelChecker::w_modification_order(ModelAction *curr) */ 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())) { + (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); } @@ -813,7 +1137,6 @@ bool ModelChecker::w_modification_order(ModelAction *curr) /** 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; @@ -822,7 +1145,7 @@ bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, con return true; for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) { - if (search==reader) + if (search == reader) return false; if (search->get_tid() == reader->get_tid() && search->happens_before(reader)) @@ -853,27 +1176,38 @@ bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, con * @return true, if the ModelChecker is certain that release_heads is complete; * false otherwise */ -bool ModelChecker::release_seq_head(const ModelAction *rf, - std::vector< const ModelAction *, MyAlloc > *release_heads) const +bool ModelChecker::release_seq_head(const ModelAction *rf, rel_heads_list_t *release_heads) const { - if (!rf) { - /* read from future: need to settle this later */ - return false; /* incomplete */ - } + /* Only check for release sequences if there are no cycles */ + if (mo_graph->checkForCycles()) + return false; - ASSERT(rf->is_write()); + while (rf) { + ASSERT(rf->is_write()); + + if (rf->is_release()) + release_heads->push_back(rf); + if (!rf->is_rmw()) + break; /* End of RMW chain */ - if (rf->is_release()) - release_heads->push_back(rf); - if (rf->is_rmw()) { - /* 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. */ + /** @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 */ - return release_seq_head(rf->get_reads_from(), release_heads); + + rf = rf->get_reads_from(); + }; + if (!rf) { + /* read from future: need to settle this later */ + return false; /* incomplete */ } + if (rf->is_release()) return true; /* complete */ @@ -910,10 +1244,13 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, * the release seq? */ bool future_ordered = false; + ModelAction *last = get_last_action(int_to_id(i)); + if (last && (rf->happens_before(last) || + last->get_type() == THREAD_FINISH)) + 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; @@ -922,6 +1259,10 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, continue; } + /* Only writes can break release sequences */ + if (!act->is_write()) + continue; + /* Check modification order */ if (mo_graph->checkReachable(rf, act)) { /* rf --mo--> act */ @@ -959,18 +1300,14 @@ 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< const ModelAction *, MyAlloc > *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; - list = lazy_sync_with_release->get_safe_ptr(act->get_location()); - list->push_back(act); - (*lazy_sync_size)++; + pending_acq_rel_seq->push_back(act); } } @@ -981,7 +1318,7 @@ void ModelChecker::get_release_seq_heads(ModelAction *act, * modification order information is present at the time an action occurs. * * @param location The location/object that should be checked for release - * sequence resolutions + * 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 @@ -989,34 +1326,40 @@ void ModelChecker::get_release_seq_heads(ModelAction *act, */ bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue) { - std::list *list; - list = lazy_sync_with_release->getptr(location); - if (!list) - return false; - bool updated = false; - std::list::iterator it = list->begin(); - while (it != list->end()) { + std::vector::iterator it = pending_acq_rel_seq->begin(); + while (it != pending_acq_rel_seq->end()) { ModelAction *act = *it; + + /* Only resolve sequences on the given location, if provided */ + if (location && act->get_location() != location) { + it++; + continue; + } + const ModelAction *rf = act->get_reads_from(); - std::vector< const ModelAction *, MyAlloc > 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++) { if (!act->has_synchronized_with(release_heads[i])) { - updated = true; - act->synchronize_with(release_heads[i]); + if (act->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 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) { - ModelAction *propagate = *it; + action_list_t::reverse_iterator rit = action_trace->rbegin(); + for (; (*rit) != act; rit++) { + ModelAction *propagate = *rit; if (act->happens_before(propagate)) { propagate->synchronize_with(act); /* Re-check 'propagate' for mo_graph edges */ @@ -1024,10 +1367,9 @@ bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_ } } } - if (complete) { - it = list->erase(it); - (*lazy_sync_size)--; - } else + if (complete) + it = pending_acq_rel_seq->erase(it); + else it++; } @@ -1063,27 +1405,56 @@ 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; } @@ -1120,16 +1491,20 @@ bool ModelChecker::resolve_promises(ModelAction *write) 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); } + read->read_from(write); //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); + //Make sure the promise's value matches the write's value + ASSERT(promise->get_value() == write->get_value()); + + delete(promise); promises->erase(promises->begin() + promise_index); resolved = true; } else @@ -1197,7 +1572,7 @@ 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) @@ -1213,11 +1588,11 @@ 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 (!curr->is_seqcst()|| (!act->is_seqcst() && (last_seq_cst==NULL||!act->happens_before(last_seq_cst))) || 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(); @@ -1263,6 +1638,34 @@ static void print_list(action_list_t *list) printf("---------------------------------------------------------------------\n"); } +#if SUPPORT_MOD_ORDER_DUMP +void ModelChecker::dumpGraph(char *filename) { + 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=\"%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 + void ModelChecker::print_summary() { printf("\n"); @@ -1273,8 +1676,10 @@ void ModelChecker::print_summary() #if SUPPORT_MOD_ORDER_DUMP scheduler->print(); char buffername[100]; - sprintf(buffername, "exec%u",num_executions); + sprintf(buffername, "exec%04u", num_executions); mo_graph->dumpGraphToFile(buffername); + sprintf(buffername, "graph%04u", num_executions); + dumpGraph(buffername); #endif if (!isfinalfeasible()) @@ -1294,17 +1699,44 @@ 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); } +/** + * @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(ModelAction *act) const +{ + return get_thread(act->get_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. Must not be NULL. + * + * @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 status from the 'swap' call (i.e., success/fail, 0/-1) */ int ModelChecker::switch_to_master(ModelAction *act) @@ -1321,37 +1753,45 @@ 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) { ASSERT(priv->current_action); priv->nextThread = check_current_action(priv->current_action); priv->current_action = NULL; - if (!curr->is_blocked() && !curr->is_complete()) - scheduler->add_thread(curr); + + if (curr->is_blocked() || curr->is_complete()) + scheduler->remove_thread(curr); } else { ASSERT(false); } } - next = scheduler->next_thread(priv->nextThread); + Thread *next = scheduler->next_thread(priv->nextThread); /* Infeasible -> don't take any more steps */ if (!isfeasible()) return false; - if (next) - next->set_state(THREAD_RUNNING); DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1); /* next == NULL -> don't take any more steps */ if (!next) return false; + + next->set_state(THREAD_RUNNING); + + 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); }