X-Git-Url: http://plrg.eecs.uci.edu/git/?p=model-checker.git;a=blobdiff_plain;f=model.cc;h=3e54a001a4541b8d5acada69e76c189ff5e82b36;hp=bd4496b14b99915b382afaf075ef4958ae9fbe82;hb=50b95c3747f4fe79b2ab1a1a6fc303224e16e418;hpb=775ba9f4b05d1a09295b0551c5efbd814b8e15aa diff --git a/model.cc b/model.cc index bd4496b..3e54a00 100644 --- a/model.cc +++ b/model.cc @@ -1,4 +1,5 @@ #include +#include #include "model.h" #include "action.h" @@ -9,6 +10,7 @@ #include "clockvector.h" #include "cyclegraph.h" #include "promise.h" +#include "datarace.h" #define INITIAL_THREAD_ID 0 @@ -18,25 +20,28 @@ ModelChecker *model; ModelChecker::ModelChecker(struct model_params params) : /* Initialize default scheduler */ scheduler(new Scheduler()), - /* First thread created will have id INITIAL_THREAD_ID */ - next_thread_id(INITIAL_THREAD_ID), - used_sequence_numbers(0), num_executions(0), params(params), - current_action(NULL), diverge(NULL), - nextThread(THREAD_ID_T_NONE), action_trace(new action_list_t()), thread_map(new HashTable()), obj_map(new HashTable()), 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) + 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 */ @@ -54,6 +59,8 @@ ModelChecker::~ModelChecker() delete (*promises)[i]; delete promises; + delete lazy_sync_with_release; + delete thrd_last_action; delete node_stack; delete scheduler; @@ -68,68 +75,57 @@ 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; -} - -/** - * 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->get(id_to_int(nextThread)); - - ASSERT(t != NULL); - - return t; + return ++priv->used_sequence_numbers; } /** - * Choose the next thread in the replay sequence. + * @brief Choose the next thread to execute. * - * 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. + * 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_id_t ModelChecker::get_next_replay_thread() +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(); + /* Have we completed exploring the preselected path? */ if (diverge == NULL) - return THREAD_ID_T_NONE; + return NULL; /* Else, we are trying to replay an execution */ ModelAction *next = node_stack->get_next()->get_action(); @@ -161,7 +157,8 @@ thread_id_t ModelChecker::get_next_replay_thread() tid = next->get_tid(); } DEBUG("*** ModelChecker chose next thread = %d ***\n", tid); - return tid; + ASSERT(tid != THREAD_ID_T_NONE); + return thread_map->get(id_to_int(tid)); } /** @@ -180,7 +177,7 @@ bool ModelChecker::next_execution() if (isfinalfeasible() || DBG_ENABLED()) print_summary(); - if ((diverge = model->get_next_backtrack()) == NULL) + if ((diverge = get_next_backtrack()) == NULL) return false; if (DBG_ENABLED()) { @@ -188,7 +185,7 @@ bool ModelChecker::next_execution() diverge->print(); } - model->reset_to_initial_state(); + reset_to_initial_state(); return true; } @@ -235,8 +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())) @@ -256,24 +253,75 @@ void ModelChecker::set_backtracking(ModelAction *act) */ ModelAction * ModelChecker::get_next_backtrack() { - ModelAction *next = next_backtrack; - next_backtrack = NULL; + ModelAction *next = priv->next_backtrack; + priv->next_backtrack = NULL; return next; } -void ModelChecker::check_current_action(void) -{ - ModelAction *curr = this->current_action; - bool already_added = false; - this->current_action = NULL; - if (!curr) { - DEBUG("trying to push NULL action...\n"); - return; +/** + * 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. + */ + +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(); + curr->read_from(NULL); + Promise *valuepromise = new Promise(curr, value); + promises->push_back(valuepromise); + } + th->set_return_value(value); + return updated; } +} + +/** + * 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); - already_added = true; + second_part_of_rmw = true; delete curr; curr = tmp; } else { @@ -304,68 +352,87 @@ void ModelChecker::check_current_action(void) } } - /* Assign 'creation' parent */ - if (curr->get_type() == THREAD_CREATE) { + /* Thread specific actions */ + switch(curr->get_type()) { + case THREAD_CREATE: { Thread *th = (Thread *)curr->get_location(); th->set_creation(curr); + break; } - - /* Deal with new thread */ - if (curr->get_type() == THREAD_START) + case THREAD_JOIN: { + Thread *wait, *join; + wait = get_thread(curr->get_tid()); + join = (Thread *)curr->get_location(); + if (!join->is_complete()) + scheduler->wait(wait, join); + break; + } + case THREAD_FINISH: { + Thread *th = get_thread(curr->get_tid()); + while (!th->wait_list_empty()) { + Thread *wake = th->pop_wait_list(); + scheduler->wake(wake); + } + th->complete(); + break; + } + case THREAD_START: { check_promises(NULL, curr->get_cv()); + break; + } + default: + break; + } - /* Assign reads_from values */ Thread *th = get_thread(curr->get_tid()); - uint64_t value = VALUE_NONE; + + bool updated = false; if (curr->is_read()) { - const ModelAction *reads_from = curr->get_node()->get_read_from(); - if (reads_from != NULL) { - value = reads_from->get_value(); - /* Assign reads_from, perform release/acquire synchronization */ - curr->read_from(reads_from); - 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); + updated=process_read(curr, th, second_part_of_rmw); } - th->set_return_value(value); + if (curr->is_write()) { + bool updated_mod_order=w_modification_order(curr); + bool updated_promises=resolve_promises(curr); + updated=updated_mod_order|updated_promises; - /* Add action to list. */ - if (!already_added) - add_action_to_lists(curr); + mo_graph->commitChanges(); + th->set_return_value(VALUE_NONE); + } - /** @todo Is there a better interface for setting the next thread rather - than this field/convoluted approach? Perhaps like just returning - it or something? */ + if (updated) + resolve_release_sequences(curr->get_location()); - /* Do not split atomic actions. */ - if (curr->is_rmwr()) - nextThread = thread_current()->get_id(); - else - nextThread = get_next_replay_thread(); + /* 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()) - if (!next_backtrack || *curr > *next_backtrack) - next_backtrack = curr; + if ((!parnode->backtrack_empty() || + !currnode->read_from_empty() || + !currnode->future_value_empty() || + !currnode->promise_empty()) + && (!priv->next_backtrack || + *curr > *priv->next_backtrack)) { + priv->next_backtrack = curr; + } set_backtracking(curr); + + return get_next_thread(curr); +} + +/** @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; + return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads; } /** Returns whether the current completed trace is feasible. */ @@ -383,14 +450,112 @@ ModelAction * ModelChecker::process_rmw(ModelAction *act) { 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 */ -void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *rf) { +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 */ @@ -405,15 +570,20 @@ void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *r if (act->happens_before(curr)) { if (act->is_read()) { const ModelAction *prevreadfrom = act->get_reads_from(); - if (prevreadfrom != NULL && rf != prevreadfrom) + 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. */ @@ -456,18 +626,23 @@ void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelActio /** * 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 */ -void ModelChecker::w_modification_order(ModelAction * curr) { +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) + if (last_seq_cst != NULL) { mo_graph->addEdge(last_seq_cst, curr); + added = true; + } } /* Iterate over all threads */ @@ -480,10 +655,17 @@ void ModelChecker::w_modification_order(ModelAction * curr) { /* Include at most one act per-thread that "happens before" curr */ if (act->happens_before(curr)) { - if (act->is_read()) - mo_graph->addEdge(act->get_reads_from(), curr); - else + /* + * Note: if act is RMW, just add edge: + * act --mo--> curr + * The following edge should be handled elsewhere: + * readfrom(act) --mo--> act + */ + if (act->is_write()) mo_graph->addEdge(act, curr); + else if (act->is_read() && act->get_reads_from() != NULL) + mo_graph->addEdge(act->get_reads_from(), curr); + added = true; break; } else if (act->is_read() && !act->is_synchronizing(curr) && !act->same_thread(curr)) { @@ -496,11 +678,13 @@ void ModelChecker::w_modification_order(ModelAction * curr) { that read could potentially read from our write. */ if (act->get_node()->add_future_value(curr->get_value()) && - (!next_backtrack || *act > *next_backtrack)) - next_backtrack = act; + (!priv->next_backtrack || *act > *priv->next_backtrack)) + priv->next_backtrack = act; } } } + + return added; } /** @@ -535,7 +719,11 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, if (rf->is_release()) release_heads->push_back(rf); if (rf->is_rmw()) { - if (rf->is_acquire()) + /* We need a RMW action that is both an acquire and release to stop */ + /** @todo Need to be smarter here... In the linux lock + * example, this will run to the beginning of the program for + * every acquire. */ + if (rf->is_acquire() && rf->is_release()) return true; /* complete */ return release_seq_head(rf->get_reads_from(), release_heads); } @@ -550,9 +738,8 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, action_list_t::const_reverse_iterator rit; /* Find rf in the thread list */ - for (rit = list->rbegin(); rit != list->rend(); rit++) - if (*rit == rf) - break; + rit = std::find(list->rbegin(), list->rend(), rf); + ASSERT(rit != list->rend()); /* Find the last write/release */ for (; rit != list->rend(); rit++) @@ -571,6 +758,11 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, if (id_to_int(rf->get_tid()) == (int)i) continue; list = &(*thrd_lists)[i]; + + /* Can we ensure no future writes from this thread may break + * the release seq? */ + bool future_ordered = false; + for (rit = list->rbegin(); rit != list->rend(); rit++) { const ModelAction *act = *rit; if (!act->is_write()) @@ -578,13 +770,17 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, /* Reach synchronization -> this thread is complete */ if (act->happens_before(release)) break; - if (rf->happens_before(act)) + if (rf->happens_before(act)) { + future_ordered = true; continue; + } /* Check modification order */ - if (mo_graph->checkReachable(rf, act)) + if (mo_graph->checkReachable(rf, act)) { /* rf --mo--> act */ + future_ordered = true; continue; + } if (mo_graph->checkReachable(act, release)) /* act --mo--> release */ break; @@ -595,6 +791,8 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, } certain = false; } + if (!future_ordered) + return false; /* This thread is uncertain */ } if (certain) @@ -621,8 +819,70 @@ void ModelChecker::get_release_seq_heads(ModelAction *act, bool complete; complete = release_seq_head(rf, release_heads); if (!complete) { - /** @todo complete lazy checking */ + /* 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; } /** @@ -641,7 +901,7 @@ void ModelChecker::add_action_to_lists(ModelAction *act) std::vector *vec = obj_thrd_map->get_safe_ptr(act->get_location()); if (tid >= (int)vec->size()) - vec->resize(next_thread_id); + vec->resize(priv->next_thread_id); (*vec)[tid].push_back(act); if ((int)thrd_last_action->size() <= tid) @@ -713,6 +973,7 @@ bool ModelChecker::resolve_promises(ModelAction *write) } else promise_index++; } + return resolved; } @@ -747,7 +1008,7 @@ void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv) merge_cv->synchronized_since(act)) { //This thread is no longer able to send values back to satisfy the promise int num_synchronized_threads = promise->increment_threads(); - if (num_synchronized_threads == model->get_num_threads()) { + if (num_synchronized_threads == get_num_threads()) { //Promise has failed failed_promise = true; return; @@ -876,10 +1137,7 @@ void ModelChecker::remove_thread(Thread *t) * context). This switch is made with the intention of exploring a particular * model-checking action (described by a ModelAction object). Must be called * from a user-thread context. - * @param act The current action that will be explored. May be NULL, although - * there is little reason to switch to the model-checker without an action to - * explore (note: act == NULL is sometimes used as a hack to allow a thread to - * yield control without performing any progress; see thrd_join()). + * @param act The current action that will be explored. Must not be NULL. * @return Return status from the 'swap' call (i.e., success/fail, 0/-1) */ int ModelChecker::switch_to_master(ModelAction *act) @@ -898,19 +1156,22 @@ int ModelChecker::switch_to_master(ModelAction *act) bool ModelChecker::take_step() { Thread *curr, *next; + if (has_asserted()) + return false; + curr = thread_current(); if (curr) { if (curr->get_state() == THREAD_READY) { - check_current_action(); - scheduler->add_thread(curr); - } else if (curr->get_state() == THREAD_RUNNING) { - /* Stopped while running; i.e., completed */ - curr->complete(); + ASSERT(priv->current_action); + priv->nextThread = check_current_action(priv->current_action); + priv->current_action = NULL; + if (!curr->is_blocked() && !curr->is_complete()) + scheduler->add_thread(curr); } else { ASSERT(false); } } - next = scheduler->next_thread(); + next = scheduler->next_thread(priv->nextThread); /* Infeasible -> don't take any more steps */ if (!isfeasible())