X-Git-Url: http://plrg.eecs.uci.edu/git/?p=model-checker.git;a=blobdiff_plain;f=model.cc;h=b5a29dd5ff16d6f430c5e6771bbc5c495e8c47d5;hp=ec953ef1f2d1a74eae62b1d04e4f288d531458ce;hb=d4b8c4bcfb145de476c9473d80653a8849f295ed;hpb=21d42a641226da15d191e45d6a8b92b160aeb07d diff --git a/model.cc b/model.cc index ec953ef..b5a29dd 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 @@ -18,14 +20,9 @@ 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(NULL), action_trace(new action_list_t()), thread_map(new HashTable()), obj_map(new HashTable()), @@ -34,10 +31,17 @@ ModelChecker::ModelChecker(struct model_params params) : 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 */ @@ -71,31 +75,28 @@ 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 = NULL; - 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; } /** @@ -163,7 +164,7 @@ 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()) { @@ -171,7 +172,7 @@ bool ModelChecker::next_execution() diverge->print(); } - model->reset_to_initial_state(); + reset_to_initial_state(); return true; } @@ -218,8 +219,8 @@ 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())) @@ -239,8 +240,8 @@ 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; } @@ -258,13 +259,13 @@ ModelAction * ModelChecker::get_next_backtrack() */ Thread * ModelChecker::check_current_action(ModelAction *curr) { - bool already_added = false; + 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 { @@ -299,6 +300,19 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) if (curr->get_type() == THREAD_CREATE) { Thread *th = (Thread *)curr->get_location(); th->set_creation(curr); + } else if (curr->get_type() == THREAD_JOIN) { + Thread *wait, *join; + wait = get_thread(curr->get_tid()); + join = (Thread *)curr->get_location(); + if (!join->is_complete()) + scheduler->wait(wait, join); + } else if (curr->get_type() == 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(); } /* Deal with new thread */ @@ -310,25 +324,40 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) uint64_t value = VALUE_NONE; bool updated = false; if (curr->is_read()) { - const ModelAction *reads_from = curr->get_node()->get_read_from(); - if (reads_from != NULL) { - value = reads_from->get_value(); - /* Assign reads_from, perform release/acquire synchronization */ - curr->read_from(reads_from); - if (r_modification_order(curr,reads_from)) - updated = true; - } else { - /* Read from future value */ - value = curr->get_node()->get_future_value(); - curr->read_from(NULL); - Promise *valuepromise = new Promise(curr, value); - promises->push_back(valuepromise); + 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); + } + break; } } else if (curr->is_write()) { if (w_modification_order(curr)) - updated = true;; + updated = true; if (resolve_promises(curr)) updated = true; + mo_graph->commitChanges(); } if (updated) @@ -337,7 +366,7 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) th->set_return_value(value); /* Add action to list. */ - if (!already_added) + if (!second_part_of_rmw) add_action_to_lists(curr); Node *currnode = curr->get_node(); @@ -345,21 +374,30 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) 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 (!priv->next_backtrack || *curr > *priv->next_backtrack) + priv->next_backtrack = curr; set_backtracking(curr); /* 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(); else return get_next_replay_thread(); } +/** @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. */ @@ -377,6 +415,56 @@ ModelAction * ModelChecker::process_rmw(ModelAction *act) { return lastread; } +/** + * Checks whether a thread has read from the same write for too many times. + * @todo This may be more subtle than this code segment addresses at this + * point... Potential problems to ponder and fix: + * (1) What if the reads_from set keeps changing such that there is no common + * write? + * (2) What if the problem is that the other writes would break modification + * order. + */ +void ModelChecker::check_recency(ModelAction *curr, bool already_added) { + if (params.maxreads != 0) { + if (curr->get_node()->get_read_from_size() <= 1) + 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++; + } + + int count=0; + for (; rit != list->rend(); rit++) { + 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; + count++; + if (count >= params.maxreads) { + /* We've read from the same write for too many times */ + too_many_reads = true; + } + } + } +} + /** * Updates the mo_graph with the constraints imposed from the current read. * @param curr The current action. Must be a read. @@ -504,8 +592,8 @@ bool ModelChecker::w_modification_order(ModelAction *curr) that read could potentially read from our write. */ if (act->get_node()->add_future_value(curr->get_value()) && - (!next_backtrack || *act > *next_backtrack)) - next_backtrack = act; + (!priv->next_backtrack || *act > *priv->next_backtrack)) + priv->next_backtrack = act; } } } @@ -545,7 +633,11 @@ 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); } @@ -560,9 +652,8 @@ 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++) @@ -581,6 +672,11 @@ 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()) @@ -588,13 +684,17 @@ 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; @@ -605,6 +705,8 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, } certain = false; } + if (!future_ordered) + return false; /* This thread is uncertain */ } if (certain) @@ -635,6 +737,7 @@ void ModelChecker::get_release_seq_heads(ModelAction *act, std::list *list; list = lazy_sync_with_release->get_safe_ptr(act->get_location()); list->push_back(act); + (*lazy_sync_size)++; } } @@ -681,12 +784,18 @@ bool ModelChecker::resolve_release_sequences(void *location) propagate->synchronize_with(act); } } - if (complete) + if (complete) { it = list->erase(it); - else + (*lazy_sync_size)--; + } else it++; } + // If we resolved promises or data races, see if we have realized a data race. + if (checkDataRaces()) { + set_assert(); + } + return updated; } @@ -706,7 +815,7 @@ 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) @@ -778,6 +887,7 @@ bool ModelChecker::resolve_promises(ModelAction *write) } else promise_index++; } + return resolved; } @@ -812,7 +922,7 @@ 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; @@ -941,10 +1051,7 @@ 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) @@ -963,22 +1070,22 @@ 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) { - if (current_action) { - nextThread = check_current_action(current_action); - current_action = NULL; - } - 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(nextThread); + next = scheduler->next_thread(priv->nextThread); /* Infeasible -> don't take any more steps */ if (!isfeasible())