X-Git-Url: http://plrg.eecs.uci.edu/git/?p=c11tester.git;a=blobdiff_plain;f=model.cc;h=9611f2f615845c926485dd732ce26b026585c085;hp=cde6213ada34c0b3c6a9a5328474ddcf9371a726;hb=1bc8782b55cab0503f1b64529f993f0b9e3a1846;hpb=ddc42efe21d50de5a6a70f82d0e45d5eea29f5fd diff --git a/model.cc b/model.cc index cde6213a..9611f2f6 100644 --- a/model.cc +++ b/model.cc @@ -1,4 +1,5 @@ #include +#include #include "model.h" #include "action.h" @@ -7,46 +8,63 @@ #include "snapshot-interface.h" #include "common.h" #include "clockvector.h" +#include "cyclegraph.h" +#include "promise.h" +#include "datarace.h" #define INITIAL_THREAD_ID 0 ModelChecker *model; /** @brief Constructor */ -ModelChecker::ModelChecker() - : +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), - current_action(NULL), + params(params), 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()), + lazy_sync_with_release(new HashTable, uintptr_t, 4>()), thrd_last_action(new std::vector(1)), node_stack(new NodeStack()), - next_backtrack(NULL) + mo_graph(new CycleGraph()), + 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 */ 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; + + for (unsigned int i = 0; i < promises->size(); i++) + delete (*promises)[i]; + delete promises; + + delete lazy_sync_with_release; + delete thrd_last_action; delete node_stack; delete scheduler; + delete mo_graph; } /** @@ -57,84 +75,90 @@ 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 */ 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 */ int ModelChecker::get_num_threads() { - return next_thread_id; + return priv->next_thread_id; } /** @returns 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 * ModelChecker::get_next_thread(ModelAction *curr) { - Thread *t; - if (nextThread == THREAD_ID_T_NONE) - return NULL; - t = (*thread_map)[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() -{ - ModelAction *next; 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(); + /* 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 */ - next = node_stack->get_next()->get_action(); + ModelAction *next = node_stack->get_next()->get_action(); if (next == diverge) { - Node *node = next->get_node()->get_parent(); - + 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(); } DEBUG("*** ModelChecker chose next thread = %d ***\n", tid); - return tid; + ASSERT(tid != THREAD_ID_T_NONE); + return thread_map->get(id_to_int(tid)); } /** @@ -149,8 +173,11 @@ bool ModelChecker::next_execution() DBG(); num_executions++; - print_summary(); - if ((diverge = model->get_next_backtrack()) == NULL) + + if (isfinalfeasible() || DBG_ENABLED()) + print_summary(); + + if ((diverge = get_next_backtrack()) == NULL) return false; if (DBG_ENABLED()) { @@ -158,7 +185,7 @@ bool ModelChecker::next_execution() diverge->print(); } - model->reset_to_initial_state(); + reset_to_initial_state(); return true; } @@ -167,18 +194,17 @@ 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->get_safe_ptr(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_synchronizing(prev)) return prev; @@ -190,7 +216,7 @@ void ModelChecker::set_backtracking(ModelAction *act) { ModelAction *prev; Node *node; - Thread *t = get_thread(act->get_tid()); + Thread *t = get_thread(act); prev = get_last_conflict(act); if (prev == NULL) @@ -206,8 +232,8 @@ void ModelChecker::set_backtracking(ModelAction *act) return; /* Cache the latest backtracking point */ - if (!next_backtrack || *prev > *next_backtrack) - next_backtrack = prev; + 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())) @@ -220,58 +246,662 @@ 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; - next_backtrack = NULL; + ModelAction *next = priv->next_backtrack; + priv->next_backtrack = NULL; return next; } -void ModelChecker::check_current_action(void) -{ - Node *currnode; +/** + * Processes a read or rmw model action. + * @param curr is the read model action to process. + * @param th is the thread + * @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. + */ - ModelAction *curr = this->current_action; - ModelAction *tmp; - current_action = NULL; - if (!curr) { - DEBUG("trying to push NULL action...\n"); - return; +bool ModelChecker::process_read(ModelAction *curr, Thread * th, bool second_part_of_rmw) { + uint64_t value; + bool updated=false; + while(true) { + 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 (!second_part_of_rmw) { + check_recency(curr,false); + } + + bool r_status=r_modification_order(curr,reads_from); + + if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||!curr->get_node()->future_value_empty())) { + mo_graph->rollbackChanges(); + too_many_reads=false; + continue; + } + + mo_graph->commitChanges(); + updated |= r_status; + } else { + /* 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); + } + th->set_return_value(value); + return updated; } +} - tmp = node_stack->explore_action(curr); - if (tmp) { - /* Discard duplicate ModelAction; use action from NodeStack */ +/** + * 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) +{ + 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 { - /* - * 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); - } - - /* Assign 'creation' parent */ - if (curr->get_type() == THREAD_CREATE) { + 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); + } + } + + /* Thread specific actions */ + switch(curr->get_type()) { + case THREAD_CREATE: { Thread *th = (Thread *)curr->get_location(); th->set_creation(curr); + break; + } + 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); + } + 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); + } + th->complete(); + break; + } + case THREAD_START: { + check_promises(NULL, curr->get_cv()); + break; + } + default: + break; + } + + Thread *th = get_thread(curr); - nextThread = get_next_replay_thread(); + bool updated = false; + if (curr->is_read()) { + updated=process_read(curr, th, second_part_of_rmw); + } + + if (curr->is_write()) { + bool updated_mod_order=w_modification_order(curr); + bool updated_promises=resolve_promises(curr); + updated=updated_mod_order|updated_promises; + + mo_graph->commitChanges(); + th->set_return_value(VALUE_NONE); + } - currnode = curr->get_node()->get_parent(); + if (updated) + resolve_release_sequences(curr->get_location()); - if (!currnode->backtrack_empty()) - if (!next_backtrack || *curr > *next_backtrack) - next_backtrack = curr; + /* Add action to list. */ + if (!second_part_of_rmw) + add_action_to_lists(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()) + && (!priv->next_backtrack || + *curr > *priv->next_backtrack)) { + priv->next_backtrack = curr; + } set_backtracking(curr); - add_action_to_lists(curr); + return get_next_thread(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; +} + +/** @returns 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. */ +bool ModelChecker::isfeasible() { + return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !promises_expired(); +} + +/** 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() && lastread->get_reads_from()!=NULL) { + mo_graph->addRMWEdge(lastread->get_reads_from(), lastread); + mo_graph->commitChanges(); + } + return lastread; +} + +/** + * 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, bool already_added) { + 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++; + } + + 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*/ + 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. + * @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 + */ +bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf) +{ + std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location()); + unsigned int i; + bool added = false; + 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) { + mo_graph->addEdge(prevreadfrom, rf); + added = true; + } + } else if (rf != act) { + mo_graph->addEdge(act, rf); + added = true; + } + break; + } + } + } + + return added; +} + +/** Updates the mo_graph 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->get_safe_ptr(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) + mo_graph->addEdge(rf, postreadfrom); + } else if (rf != lastact) { + mo_graph->addEdge(rf, lastact); + } + break; + } + } +} + +/** + * Updates the mo_graph with the constraints imposed from the current write. + * @param curr The current action. Must be a write. + * @return True if modification order edges were added; false otherwise + */ +bool ModelChecker::w_modification_order(ModelAction *curr) +{ + std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location()); + unsigned int i; + bool added = false; + 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) { + mo_graph->addEdge(last_seq_cst, curr); + added = 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; + + /* Include at most one act per-thread that "happens before" curr */ + if (act->happens_before(curr)) { + /* + * 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()) { + //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) + mo_graph->addEdge(act->get_reads_from(), curr); + added = true; + 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 (isfeasible() && act->get_node()->add_future_value(curr->get_value(), curr->get_seq_number()+params.maxfuturedelay) && + (!priv->next_backtrack || *act > *priv->next_backtrack)) + priv->next_backtrack = act; + } + } + } + + return added; +} + +/** + * Finds the head(s) of the release sequence(s) containing a given ModelAction. + * The ModelAction under consideration is expected to be taking part in + * release/acquire synchronization as an object of the "reads from" relation. + * Note that this can only provide release sequence support for RMW chains + * which do not read from the future, as those actions cannot be traced until + * their "promise" is fulfilled. Similarly, we may not even establish the + * presence of a release sequence with certainty, as some modification order + * constraints may be decided further in the future. Thus, this function + * "returns" two pieces of data: a pass-by-reference vector of @a release_heads + * and a boolean representing certainty. + * + * @todo Finish lazy updating, when promises are fulfilled in the future + * @param rf The action that might be part of a release sequence. Must be a + * write. + * @param release_heads A pass-by-reference style return parameter. After + * execution of this function, release_heads will contain the heads of all the + * relevant release sequences, if any exists + * @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 +{ + ASSERT(rf->is_write()); + if (!rf) { + /* read from future: need to settle this later */ + return false; /* incomplete */ + } + 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. */ + if (rf->is_acquire() && rf->is_release()) + return true; /* complete */ + return release_seq_head(rf->get_reads_from(), release_heads); + } + if (rf->is_release()) + return true; /* complete */ + + /* else relaxed write; check modification order for contiguous subsequence + * -> rf must be same thread as release */ + int tid = id_to_int(rf->get_tid()); + std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location()); + action_list_t *list = &(*thrd_lists)[tid]; + action_list_t::const_reverse_iterator rit; + + /* Find rf in the thread list */ + rit = std::find(list->rbegin(), list->rend(), rf); + ASSERT(rit != list->rend()); + + /* Find the last write/release */ + for (; rit != list->rend(); rit++) + if ((*rit)->is_release()) + break; + if (rit == list->rend()) { + /* No write-release in this thread */ + return true; /* complete */ + } + ModelAction *release = *rit; + + ASSERT(rf->same_thread(release)); + + bool certain = true; + for (unsigned int i = 0; i < thrd_lists->size(); i++) { + 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; + + 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)) { + future_ordered = true; + continue; + } + + /* Check modification order */ + if (mo_graph->checkReachable(rf, act)) { + /* rf --mo--> act */ + future_ordered = true; + continue; + } + if (mo_graph->checkReachable(act, release)) + /* act --mo--> release */ + break; + if (mo_graph->checkReachable(release, act) && + mo_graph->checkReachable(act, rf)) { + /* release --mo-> act --mo--> rf */ + return true; /* complete */ + } + certain = false; + } + if (!future_ordered) + return false; /* This thread is uncertain */ + } + + if (certain) + release_heads->push_back(release); + return certain; +} + +/** + * A public interface for getting the release sequence head(s) with which a + * given ModelAction must synchronize. This function only returns a non-empty + * result when it can locate a release sequence head with certainty. Otherwise, + * it may mark the internal state of the ModelChecker so that it will handle + * the release sequence at a later time, causing @a act to update its + * synchronization at some later point in execution. + * @param act The 'acquire' action that may read from a release sequence + * @param release_heads A pass-by-reference return parameter. Will be filled + * 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) +{ + 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)++; + } +} + +/** + * Attempt to resolve all stashed operations that might synchronize with a + * release sequence for a given location. This implements the "lazy" portion of + * determining whether or not a release sequence was contiguous, since not all + * modification order information is present at the time an action occurs. + * + * @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) + */ +bool ModelChecker::resolve_release_sequences(void *location) +{ + 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()) { + ModelAction *act = *it; + const ModelAction *rf = act->get_reads_from(); + std::vector 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 (updated) { + /* propagate synchronization to later actions */ + action_list_t::reverse_iterator it = action_trace->rbegin(); + while ((*it) != act) { + ModelAction *propagate = *it; + if (act->happens_before(propagate)) + /** @todo new mo_graph edges along with + * this synchronization? */ + propagate->synchronize_with(act); + } + } + if (complete) { + it = list->erase(it); + (*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; } /** @@ -286,9 +916,11 @@ 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)[act->get_location()]; + obj_map->get_safe_ptr(act->get_location())->push_back(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) @@ -304,6 +936,23 @@ ModelAction * ModelChecker::get_last_action(thread_id_t tid) return (*thrd_last_action)[id_to_int(tid)]; } +/** + * 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->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()) + return *rit; + return NULL; +} + ModelAction * ModelChecker::get_parent_action(thread_id_t tid) { ModelAction *parent = get_last_action(tid); @@ -312,10 +961,84 @@ ModelAction * ModelChecker::get_parent_action(thread_id_t tid) return parent; } -ClockVector * ModelChecker::get_cv(thread_id_t tid) { +/** + * 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 a set of Promises with a current write. The set is provided in the + * Node corresponding to @a write. + * @param write The ModelAction that is fulfilling Promises + * @return True if promises were resolved; false otherwise + */ +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); + } + r_modification_order(read, write); + post_r_modification_order(read, write); + promises->erase(promises->begin() + promise_index); + resolved = true; + } else + promise_index++; + } + + return resolved; +} + +/** + * Compute the set of promises that could potentially be satisfied by this + * action. Note that the set computation actually appears in the Node, not in + * ModelChecker. + * @param curr The ModelAction that may satisfy promises + */ +void ModelChecker::compute_promises(ModelAction *curr) +{ + for (unsigned int i = 0; i < promises->size(); i++) { + Promise *promise = (*promises)[i]; + const ModelAction *act = promise->get_action(); + if (!act->happens_before(curr) && + act->is_read() && + !act->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; i < promises->size(); i++) { + Promise *promise = (*promises)[i]; + const ModelAction *act = promise->get_action(); + if ((old_cv == NULL || !old_cv->synchronized_since(act)) && + merge_cv->synchronized_since(act)) { + //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 == get_num_threads()) { + //Promise has failed + failed_promise = true; + return; + } + } + } +} + /** * 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" @@ -325,15 +1048,26 @@ ClockVector * ModelChecker::get_cv(thread_id_t tid) { */ void ModelChecker::build_reads_from_past(ModelAction *curr) { - std::vector *thrd_lists = &(*obj_thrd_map)[curr->get_location()]; + std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(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++) { @@ -343,12 +1077,15 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) if (!act->is_write()) continue; - DEBUG("Adding action to may_read_from:\n"); - if (DBG_ENABLED()) { - act->print(); - curr->print(); + /* 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) { + DEBUG("Adding action to may_read_from:\n"); + if (DBG_ENABLED()) { + act->print(); + curr->print(); + } + curr->get_node()->add_read_from(act); } - curr->get_node()->add_read_from(act); /* Include at most one act per-thread that "happens before" curr */ if (act->happens_before(curr)) { @@ -359,7 +1096,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) } if (!initialized) { - /* TODO: need a more informative way of reporting errors */ + /** @todo Need a more informative way of reporting errors. */ printf("ERROR: may read from uninitialized atomic\n"); } @@ -387,7 +1124,7 @@ static void print_list(action_list_t *list) printf("---------------------------------------------------------------------\n"); } -void ModelChecker::print_summary(void) +void ModelChecker::print_summary() { printf("\n"); printf("Number of executions: %d\n", num_executions); @@ -395,15 +1132,21 @@ void ModelChecker::print_summary(void) scheduler->print(); + if (!isfinalfeasible()) + printf("INFEASIBLE EXECUTION!\n"); print_list(action_trace); printf("\n"); } -int ModelChecker::add_thread(Thread *t) +/** + * Add a Thread to the system for the first time. Should only be called once + * per thread. + * @param t The Thread to add + */ +void 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; } void ModelChecker::remove_thread(Thread *t) @@ -411,13 +1154,65 @@ 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. Must not be NULL. + * @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()); + return Thread::swap(old, &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; + + if (has_asserted()) + return false; + + 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); + } else { + ASSERT(false); + } + } + 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; + /* Return false only if swap fails with an error */ + return (Thread::swap(&system_context, next) == 0); +} + +/** Runs the current execution until threre are no more steps to take. */ +void ModelChecker::finish_execution() { + DBG(); + + while (take_step()); }