X-Git-Url: http://plrg.eecs.uci.edu/git/?p=model-checker.git;a=blobdiff_plain;f=model.cc;h=964e83fbd623270628ec1b078b2e9d81c9d136c0;hp=86d28ec0bfc4119b16f0c5c0eba62c34d05ea3d5;hb=b7a6b3c7fb66628a4b14af804418dbfff4072e95;hpb=5734b17b928d722e2c6a37c4e152c0dcbf58175d diff --git a/model.cc b/model.cc index 86d28ec..964e83f 100644 --- a/model.cc +++ b/model.cc @@ -6,44 +6,59 @@ #include "schedule.h" #include "snapshot-interface.h" #include "common.h" +#include "clockvector.h" +#include "cyclegraph.h" +#include "promise.h" #define INITIAL_THREAD_ID 0 ModelChecker *model; -ModelChecker::ModelChecker() - : +/** @brief Constructor */ +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), + params(params), current_action(NULL), diverge(NULL), nextThread(THREAD_ID_T_NONE), action_trace(new action_list_t()), - thread_map(new std::map), - obj_thrd_map(new std::map >()), + thread_map(new HashTable()), + obj_map(new HashTable()), + obj_thrd_map(new HashTable, uintptr_t, 4 >()), + promises(new std::vector()), + thrd_last_action(new std::vector(1)), node_stack(new NodeStack()), - next_backtrack(NULL) + next_backtrack(NULL), + cyclegraph(new CycleGraph()), + failed_promise(false) { } +/** @brief Destructor */ ModelChecker::~ModelChecker() { - std::map::iterator it; - for (it = thread_map->begin(); it != thread_map->end(); it++) - delete (*it).second; + for (int i = 0; i < get_num_threads(); i++) + delete thread_map->get(i); delete thread_map; delete obj_thrd_map; + delete obj_map; delete action_trace; + delete thrd_last_action; delete node_stack; delete scheduler; + delete cyclegraph; } +/** + * Restores user program to initial state and resets all model-checker data + * structures. + */ void ModelChecker::reset_to_initial_state() { DEBUG("+++ Resetting to initial state +++\n"); @@ -53,46 +68,58 @@ void ModelChecker::reset_to_initial_state() used_sequence_numbers = 0; nextThread = 0; next_backtrack = NULL; + failed_promise = false; snapshotObject->backTrackBeforeStep(0); } +/** @returns a thread ID for a new Thread */ thread_id_t ModelChecker::get_next_id() { return next_thread_id++; } +/** @returns the number of user threads created during this execution */ int ModelChecker::get_num_threads() { return next_thread_id; } -int ModelChecker::get_next_seq_num() +/** @returns a sequence number for a new ModelAction */ +modelclock_t ModelChecker::get_next_seq_num() { return ++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. + * + * @return The next thread chosen by the model-checker. If the model-checker + * makes no selection, retuns NULL. + */ Thread * ModelChecker::schedule_next_thread() { Thread *t; if (nextThread == THREAD_ID_T_NONE) return NULL; - t = (*thread_map)[id_to_int(nextThread)]; + t = thread_map->get(id_to_int(nextThread)); ASSERT(t != NULL); return t; } -/* - * get_next_replay_thread() - Choose the next thread in the replay sequence +/** + * Choose the next thread in the replay sequence. * - * If we've reached the 'diverge' point, then we pick a thread from the - * backtracking set. - * Otherwise, we simply return the next thread in the 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() { - ModelAction *next; thread_id_t tid; /* Have we completed exploring the preselected path? */ @@ -100,14 +127,30 @@ thread_id_t ModelChecker::get_next_replay_thread() return THREAD_ID_T_NONE; /* Else, we are trying to replay an execution */ - next = node_stack->get_next()->get_action(); + ModelAction * next = node_stack->get_next()->get_action(); if (next == diverge) { - Node *node = next->get_node(); - + Node *nextnode = next->get_node(); /* Reached divergence point */ + if (nextnode->increment_promise()) { + /* The next node will try to satisfy a different set of promises. */ + tid = next->get_tid(); + node_stack->pop_restofstack(2); + } else if (nextnode->increment_read_from()) { + /* The next node will read from a different value. */ + tid = next->get_tid(); + node_stack->pop_restofstack(2); + } else if (nextnode->increment_future_value()) { + /* The next node will try to read from a different future value. */ + tid = next->get_tid(); + node_stack->pop_restofstack(2); + } else { + /* Make a different thread execute for next step */ + Node *node = nextnode->get_parent(); + tid = node->get_next_backtrack(); + node_stack->pop_restofstack(1); + } DEBUG("*** Divergence point ***\n"); - tid = node->get_next_backtrack(); diverge = NULL; } else { tid = next->get_tid(); @@ -116,12 +159,22 @@ thread_id_t ModelChecker::get_next_replay_thread() return tid; } +/** + * Queries the model-checker for more executions to explore and, if one + * exists, resets the model-checker state to execute a new execution. + * + * @return If there are more executions to explore, return true. Otherwise, + * return false. + */ bool ModelChecker::next_execution() { DBG(); num_executions++; - print_summary(); + + if (isfinalfeasible() || DBG_ENABLED()) + print_summary(); + if ((diverge = model->get_next_backtrack()) == NULL) return false; @@ -139,20 +192,19 @@ ModelAction * ModelChecker::get_last_conflict(ModelAction *act) action_type type = act->get_type(); switch (type) { - case THREAD_CREATE: - case THREAD_YIELD: - case THREAD_JOIN: - return NULL; case ATOMIC_READ: case ATOMIC_WRITE: - default: + case ATOMIC_RMW: break; + default: + return NULL; } /* linear search: from most recent to oldest */ + action_list_t *list = obj_map->ensureptr(act->get_location()); action_list_t::reverse_iterator rit; - for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) { + for (rit = list->rbegin(); rit != list->rend(); rit++) { ModelAction *prev = *rit; - if (act->is_dependent(prev)) + if (act->is_synchronizing(prev)) return prev; } return NULL; @@ -168,7 +220,7 @@ void ModelChecker::set_backtracking(ModelAction *act) if (prev == NULL) return; - node = prev->get_node(); + node = prev->get_node()->get_parent(); while (!node->is_enabled(t)) t = t->get_parent(); @@ -177,6 +229,7 @@ void ModelChecker::set_backtracking(ModelAction *act) if (node->has_been_explored(t->get_id())) return; + /* Cache the latest backtracking point */ if (!next_backtrack || *prev > *next_backtrack) next_backtrack = prev; @@ -191,6 +244,11 @@ void ModelChecker::set_backtracking(ModelAction *act) } } +/** + * Returns last backtracking point. The model checker will explore a different + * path for this point in the next execution. + * @return The ModelAction at which the next execution should diverge. + */ ModelAction * ModelChecker::get_next_backtrack() { ModelAction *next = next_backtrack; @@ -200,46 +258,438 @@ ModelAction * ModelChecker::get_next_backtrack() void ModelChecker::check_current_action(void) { - Node *currnode; - ModelAction *curr = this->current_action; - current_action = NULL; + bool already_added = false; + this->current_action = NULL; if (!curr) { DEBUG("trying to push NULL action...\n"); return; } - curr = node_stack->explore_action(curr); - nextThread = get_next_replay_thread(); + if (curr->is_rmwc() || curr->is_rmw()) { + ModelAction *tmp = process_rmw(curr); + already_added = true; + delete curr; + curr = tmp; + } 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); + } + } + + /* Assign 'creation' parent */ + if (curr->get_type() == THREAD_CREATE) { + Thread *th = (Thread *)curr->get_location(); + th->set_creation(curr); + } + + /* Deal with new thread */ + if (curr->get_type() == THREAD_START) + check_promises(NULL, curr->get_cv()); + + /* Assign reads_from values */ + Thread *th = get_thread(curr->get_tid()); + uint64_t value = VALUE_NONE; + 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); + r_modification_order(curr,reads_from); + } 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); + } + } else if (curr->is_write()) { + w_modification_order(curr); + resolve_promises(curr); + } + + th->set_return_value(value); - currnode = curr->get_node(); + /* Add action to list. */ + if (!already_added) + add_action_to_lists(curr); - if (!currnode->backtrack_empty()) + /** @todo Is there a better interface for setting the next thread rather + than this field/convoluted approach? Perhaps like just returning + it or something? */ + + /* Do not split atomic actions. */ + if (curr->is_rmwr()) + nextThread = thread_current()->get_id(); + else + nextThread = get_next_replay_thread(); + + 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; set_backtracking(curr); - this->action_trace->push_back(curr); +} + +/** @returns whether the current partial trace is feasible. */ +bool ModelChecker::isfeasible() { + return !cyclegraph->checkForCycles() && !failed_promise; +} + +/** Returns whether the current completed trace is feasible. */ +bool ModelChecker::isfinalfeasible() { + return isfeasible() && promises->size() == 0; +} + +/** Close out a RMWR by converting previous RMWR into a RMW or READ. */ +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()) + cyclegraph->addRMWEdge(lastread, lastread->get_reads_from()); + return lastread; +} + +/** + * Updates the cyclegraph with the constraints imposed from the current read. + * @param curr The current action. Must be a read. + * @param rf The action that curr reads from. Must be a write. + */ +void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *rf) { + std::vector *thrd_lists = obj_thrd_map->ensureptr(curr->get_location()); + unsigned int i; + ASSERT(curr->is_read()); + + /* Iterate over all threads */ + for (i = 0; i < thrd_lists->size(); i++) { + /* Iterate over actions in thread, starting from most recent */ + action_list_t *list = &(*thrd_lists)[i]; + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *act = *rit; + + /* Include at most one act per-thread that "happens before" curr */ + if (act->happens_before(curr)) { + if (act->is_read()) { + const ModelAction * prevreadfrom = act->get_reads_from(); + if (prevreadfrom != NULL && rf != prevreadfrom) + cyclegraph->addEdge(rf, prevreadfrom); + } else if (rf != act) { + cyclegraph->addEdge(rf, act); + } + break; + } + } + } +} + +/** Updates the cyclegraph with the constraints imposed from the + * current read. */ +void ModelChecker::post_r_modification_order(ModelAction * curr, const ModelAction *rf) { + std::vector *thrd_lists = obj_thrd_map->ensureptr(curr->get_location()); + unsigned int i; + ASSERT(curr->is_read()); + + /* Iterate over all threads */ + for (i = 0; i < thrd_lists->size(); i++) { + /* Iterate over actions in thread, starting from most recent */ + action_list_t *list = &(*thrd_lists)[i]; + action_list_t::reverse_iterator rit; + ModelAction *lastact = NULL; + + /* Find last action that happens after curr */ + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *act = *rit; + if (curr->happens_before(act)) { + lastact = act; + } else + break; + } + + /* Include at most one act per-thread that "happens before" curr */ + if (lastact != NULL) { + if (lastact->is_read()) { + const ModelAction * postreadfrom = lastact->get_reads_from(); + if (postreadfrom != NULL&&rf != postreadfrom) + cyclegraph->addEdge(postreadfrom, rf); + } else if (rf != lastact) { + cyclegraph->addEdge(lastact, rf); + } + break; + } + } +} + +/** + * Updates the cyclegraph with the constraints imposed from the current write. + * @param curr The current action. Must be a write. + */ +void ModelChecker::w_modification_order(ModelAction * curr) { + std::vector *thrd_lists = obj_thrd_map->ensureptr(curr->get_location()); + unsigned int i; + ASSERT(curr->is_write()); + + if (curr->is_seqcst()) { + /* We have to at least see the last sequentially consistent write, + so we are initialized. */ + ModelAction * last_seq_cst = get_last_seq_cst(curr->get_location()); + if (last_seq_cst != NULL) + cyclegraph->addEdge(curr, last_seq_cst); + } + + /* Iterate over all threads */ + for (i = 0; i < thrd_lists->size(); i++) { + /* Iterate over actions in thread, starting from most recent */ + action_list_t *list = &(*thrd_lists)[i]; + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *act = *rit; + + /* Include at most one act per-thread that "happens before" curr */ + if (act->happens_before(curr)) { + if (act->is_read()) + cyclegraph->addEdge(curr, act->get_reads_from()); + else + cyclegraph->addEdge(curr, act); + break; + } else if (act->is_read() && !act->is_synchronizing(curr) && + !act->same_thread(curr)) { + /* We have an action that: + (1) did not happen before us + (2) is a read and we are a write + (3) cannot synchronize with us + (4) is in a different thread + => + that read could potentially read from our write. + */ + if (act->get_node()->add_future_value(curr->get_value()) && + (!next_backtrack || *act > *next_backtrack)) + next_backtrack = act; + } + } + } +} + +/** + * Performs various bookkeeping operations for the current ModelAction. For + * instance, adds action to the per-object, per-thread action vector and to the + * action trace list of all thread actions. + * + * @param act is the ModelAction to add. + */ +void ModelChecker::add_action_to_lists(ModelAction *act) +{ + int tid = id_to_int(act->get_tid()); + action_trace->push_back(act); - std::vector *vec = &(*obj_thrd_map)[curr->get_location()]; - if (id_to_int(curr->get_tid()) >= (int)vec->size()) + obj_map->ensureptr(act->get_location())->push_back(act); + + std::vector *vec = obj_thrd_map->ensureptr(act->get_location()); + if (tid >= (int)vec->size()) vec->resize(next_thread_id); - (*vec)[id_to_int(curr->get_tid())].push_back(curr); + (*vec)[tid].push_back(act); + + if ((int)thrd_last_action->size() <= tid) + thrd_last_action->resize(get_num_threads()); + (*thrd_last_action)[tid] = act; } -void ModelChecker::print_summary(void) +ModelAction * ModelChecker::get_last_action(thread_id_t tid) { - printf("\n"); - printf("Number of executions: %d\n", num_executions); - printf("Total nodes created: %d\n", Node::get_total_nodes()); + 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)]; +} - scheduler->print(); +/** + * 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 + */ +ModelAction * ModelChecker::get_last_seq_cst(const void *location) +{ + action_list_t *list = obj_map->ensureptr(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()) + return *rit; + return NULL; +} - print_list(action_trace); - printf("\n"); +ModelAction * ModelChecker::get_parent_action(thread_id_t tid) +{ + ModelAction *parent = get_last_action(tid); + if (!parent) + parent = get_thread(tid)->get_creation(); + return parent; +} + +/** + * Returns the clock vector for a given thread. + * @param tid The thread whose clock vector we want + * @return Desired clock vector + */ +ClockVector * ModelChecker::get_cv(thread_id_t tid) { + return get_parent_action(tid)->get_cv(); +} + + +/** Resolve the given promises. */ + +void ModelChecker::resolve_promises(ModelAction *write) { + for (unsigned int i = 0, promise_index = 0;promise_indexsize(); i++) { + Promise * promise = (*promises)[promise_index]; + if (write->get_node()->get_promise(i)) { + ModelAction * read = promise->get_action(); + read->read_from(write); + r_modification_order(read, write); + post_r_modification_order(read, write); + promises->erase(promises->begin()+promise_index); + } else + promise_index++; + } +} + +/** Compute the set of promises that could potentially be satisfied by + * this action. */ + +void ModelChecker::compute_promises(ModelAction *curr) { + for (unsigned int i = 0;isize();i++) { + Promise * promise = (*promises)[i]; + const ModelAction * act = promise->get_action(); + if (!act->happens_before(curr)&& + act->is_read()&& + !act->is_synchronizing(curr)&& + !act->same_thread(curr)&& + promise->get_value() == curr->get_value()) { + curr->get_node()->set_promise(i); + } + } +} + +/** Checks promises in response to change in ClockVector Threads. */ + +void ModelChecker::check_promises(ClockVector *old_cv, ClockVector * merge_cv) { + for (unsigned int i = 0;isize();i++) { + Promise * promise = (*promises)[i]; + const ModelAction * act = promise->get_action(); + if ((old_cv == NULL||!old_cv->synchronized_since(act))&& + merge_cv->synchronized_since(act)) { + //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()) { + //Promise has failed + failed_promise = true; + return; + } + } + } } -void ModelChecker::print_list(action_list_t *list) +/** + * Build up an initial set of all past writes that this 'read' action may read + * from. This set is determined by the clock vector's "happens before" + * relationship. + * @param curr is the current ModelAction that we are exploring; it must be a + * 'read' operation. + */ +void ModelChecker::build_reads_from_past(ModelAction *curr) +{ + std::vector *thrd_lists = obj_thrd_map->ensureptr(curr->get_location()); + unsigned int i; + ASSERT(curr->is_read()); + + ModelAction *last_seq_cst = NULL; + + /* Track whether this object has been initialized */ + bool initialized = false; + + if (curr->is_seqcst()) { + last_seq_cst = get_last_seq_cst(curr->get_location()); + /* We have to at least see the last sequentially consistent write, + so we are initialized. */ + if (last_seq_cst != NULL) + initialized = true; + } + + /* Iterate over all threads */ + for (i = 0; i < thrd_lists->size(); i++) { + /* Iterate over actions in thread, starting from most recent */ + action_list_t *list = &(*thrd_lists)[i]; + action_list_t::reverse_iterator rit; + for (rit = list->rbegin(); rit != list->rend(); rit++) { + ModelAction *act = *rit; + + /* Only consider 'write' actions */ + if (!act->is_write()) + 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) { + DEBUG("Adding action to may_read_from:\n"); + if (DBG_ENABLED()) { + act->print(); + curr->print(); + } + curr->get_node()->add_read_from(act); + } + + /* Include at most one act per-thread that "happens before" curr */ + if (act->happens_before(curr)) { + initialized = true; + break; + } + } + } + + if (!initialized) { + /** @todo Need a more informative way of reporting errors. */ + printf("ERROR: may read from uninitialized atomic\n"); + } + + if (DBG_ENABLED() || !initialized) { + printf("Reached read action:\n"); + curr->print(); + printf("Printing may_read_from\n"); + curr->get_node()->print_may_read_from(); + printf("End printing may_read_from\n"); + } + + ASSERT(initialized); +} + +static void print_list(action_list_t *list) { action_list_t::iterator it; @@ -252,9 +702,23 @@ void ModelChecker::print_list(action_list_t *list) printf("---------------------------------------------------------------------\n"); } +void ModelChecker::print_summary() +{ + printf("\n"); + printf("Number of executions: %d\n", num_executions); + printf("Total nodes created: %d\n", node_stack->get_total_nodes()); + + scheduler->print(); + + if (!isfinalfeasible()) + printf("INFEASIBLE EXECUTION!\n"); + print_list(action_trace); + printf("\n"); +} + int ModelChecker::add_thread(Thread *t) { - (*thread_map)[id_to_int(t->get_id())] = t; + thread_map->put(id_to_int(t->get_id()), t); scheduler->add_thread(t); return 0; } @@ -264,13 +728,65 @@ void ModelChecker::remove_thread(Thread *t) scheduler->remove_thread(t); } +/** + * Switch from a user-context to the "master thread" context (a.k.a. system + * context). This switch is made with the intention of exploring a particular + * model-checking action (described by a ModelAction object). Must be called + * from a user-thread context. + * @param act The current action that will be explored. May be NULL, 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()). + * @return Return status from the 'swap' call (i.e., success/fail, 0/-1) + */ int ModelChecker::switch_to_master(ModelAction *act) { - Thread *old; - DBG(); - old = thread_current(); + Thread * old = thread_current(); set_current_action(act); old->set_state(THREAD_READY); return Thread::swap(old, get_system_context()); } + +/** + * Takes the next step in the execution, if possible. + * @return Returns true (success) if a step was taken and false otherwise. + */ +bool ModelChecker::take_step() { + Thread *curr, *next; + + 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(); + } else { + ASSERT(false); + } + } + next = scheduler->next_thread(); + + /* 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; + /* Return false only if swap fails with an error */ + return (Thread::swap(get_system_context(), next) == 0); +} + +/** Runs the current execution until threre are no more steps to take. */ +void ModelChecker::finish_execution() { + DBG(); + + while (take_step()); +}