-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()<priv->used_sequence_numbers) {
- return true;
- }
- }
- return false;
-}
-
-/** @return whether the current partial trace must be a prefix of a
- * feasible trace. */
-bool ModelChecker::isfeasibleprefix() {
- return promises->size() == 0 && pending_rel_seqs->size() == 0 && isfeasible();
-}
-
-/** @return whether the current partial trace is feasible. */
-bool ModelChecker::isfeasible() {
- if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
- DEBUG("Infeasible: RMW violation\n");
-
- return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW();
-}
-
-/** @return whether the current partial trace is feasible other than
- * multiple RMW reading from the same store. */
-bool ModelChecker::isfeasibleotherthanRMW() {
- if (DBG_ENABLED()) {
- if (mo_graph->checkForCycles())
- DEBUG("Infeasible: modification order cycles\n");
- if (failed_promise)
- DEBUG("Infeasible: failed promise\n");
- if (too_many_reads)
- DEBUG("Infeasible: too many reads\n");
- if (bad_synchronization)
- DEBUG("Infeasible: bad synchronization ordering\n");
- if (promises_expired())
- DEBUG("Infeasible: promises expired\n");
- }
- return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !bad_synchronization && !promises_expired();
-}
-
-/** Returns whether the current completed trace is feasible. */
-bool ModelChecker::isfinalfeasible() {
- if (DBG_ENABLED() && promises->size() != 0)
- DEBUG("Infeasible: unrevolved promises\n");
-
- return isfeasible() && promises->size() == 0;
-}
-
-/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
-ModelAction * ModelChecker::process_rmw(ModelAction *act) {
- ModelAction *lastread = get_last_action(act->get_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, const ModelAction *rf) {
- if (params.maxreads != 0) {
-
- if (curr->get_node()->get_read_from_size() <= 1)
- return;
- //Must make sure that execution is currently feasible... We could
- //accidentally clear by rolling back
- if (!isfeasible())
- return;
- std::vector<action_list_t> *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 */
- 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() != rf)
- return;
- if (act->get_node()->get_read_from_size() <= 1)
- return;
- }
- for (int i = 0; i<curr->get_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==rf)
- continue;
-
- /* Test to see whether this is a feasible write to read from*/
- mo_graph->startChanges();
- 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; j<act->get_node()->get_read_from_size(); j++) {
- if (act->get_node()->get_read_from_at(j)==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.
- *
- * Basic idea is the following: Go through each other thread and find
- * the lastest action that happened before our read. Two cases:
- *
- * (1) The action is a write => that write must either occur before
- * the write we read from or be the write we read from.
- *
- * (2) The action is a read => the write that that action read from
- * must occur before the write we read from or be the same write.
- *
- * @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<action_list_t> *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. Don't consider reflexively.
- */
- if (act->happens_before(curr) && act != curr) {
- if (act->is_write()) {
- if (rf != act) {
- mo_graph->addEdge(act, rf);
- added = true;
- }
- } else {
- const ModelAction *prevreadfrom = act->get_reads_from();
- //if the previous read is unresolved, keep going...
- if (prevreadfrom == NULL)
- continue;
-
- if (rf != prevreadfrom) {
- mo_graph->addEdge(prevreadfrom, rf);
- added = true;
- }
- }
- break;
- }
- }
- }
-
- return added;
-}
-
-/** This method fixes up the modification order when we resolve a
- * promises. The basic problem is that actions that occur after the
- * read curr could not property add items to the modification order
- * for our read.
- *
- * So for each thread, we find the earliest item that happens after
- * the read curr. This is the item we have to fix up with additional
- * constraints. If that action is write, we add a MO edge between
- * the Action rf and that action. If the action is a read, we add a
- * MO edge between the Action rf, and whatever the read accessed.
- *
- * @param curr is the read ModelAction that we are fixing up MO edges for.
- * @param rf is the write ModelAction that curr reads from.
- *
- */
-void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
-{
- std::vector<action_list_t> *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 that is either not curr or a rmw */
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
- if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
- lastact = act;
- } else
- break;
- }
-
- /* Include at most one act per-thread that "happens before" curr */
- if (lastact != NULL) {
- if (lastact==curr) {
- //Case 1: The resolved read is a RMW, and we need to make sure
- //that the write portion of the RMW mod order after rf
-
- mo_graph->addEdge(rf, lastact);
- } else if (lastact->is_read()) {
- //Case 2: The resolved read is a normal read and the next
- //operation is a read, and we need to make sure the value read
- //is mod ordered after rf
-
- const ModelAction *postreadfrom = lastact->get_reads_from();
- if (postreadfrom != NULL&&rf != postreadfrom)
- mo_graph->addEdge(rf, postreadfrom);
- } else {
- //Case 3: The resolved read is a normal read and the next
- //operation is a write, and we need to make sure that the
- //write is mod ordered after rf
- if (lastact!=rf)
- mo_graph->addEdge(rf, lastact);
- }
- break;
- }
- }
-}
-
-/**
- * Updates the mo_graph with the constraints imposed from the current write.
- *
- * Basic idea is the following: Go through each other thread and find
- * the lastest action that happened before our write. Two cases:
- *
- * (1) The action is a write => that write must occur before
- * the current write
- *
- * (2) The action is a read => the write that that action read from
- * must occur before the current write.
- *
- * This method also handles two other issues:
- *
- * (I) Sequential Consistency: Making sure that if the current write is
- * seq_cst, that it occurs after the previous seq_cst write.
- *
- * (II) Sending the write back to non-synchronizing reads.
- *
- * @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<action_list_t> *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);
- 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;
- if (act == curr) {
- /*
- * 1) If RMW and it actually read from something, then we
- * already have all relevant edges, so just skip to next
- * thread.
- *
- * 2) If RMW and it didn't read from anything, we should
- * whatever edge we can get to speed up convergence.
- *
- * 3) If normal write, we need to look at earlier actions, so
- * continue processing list.
- */
- if (curr->is_rmw()) {
- if (curr->get_reads_from()!=NULL)
- break;
- else
- continue;
- } else
- continue;
- }
-
- /*
- * Include at most one act per-thread that "happens
- * before" curr
- */
- 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())
- mo_graph->addEdge(act, curr);
- else if (act->is_read()) {
- //if previous read accessed a null, just keep going
- if (act->get_reads_from() == NULL)
- continue;
- mo_graph->addEdge(act->get_reads_from(), curr);
- }
- added = true;
- break;
- } else if (act->is_read() && !act->could_synchronize_with(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. Note that
- these checks are overly conservative at this point, we'll
- do more checks before actually removing the
- pendingfuturevalue.
-
- */
- if (thin_air_constraint_may_allow(curr, act)) {
- if (isfeasible() ||
- (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() == act->get_reads_from() && isfeasibleotherthanRMW())) {
- struct PendingFutureValue pfv = {curr,act};
- futurevalues->push_back(pfv);
- }
- }
- }
- }
- }
-
- return added;
-}
-
-/** Arbitrary reads from the future are not allowed. Section 29.3
- * part 9 places some constraints. This method checks one result of constraint
- * constraint. Others require compiler support. */
-bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) {
- if (!writer->is_rmw())
- return true;
-
- if (!reader->is_rmw())
- return true;
-
- for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
- if (search == reader)
- return false;
- if (search->get_tid() == reader->get_tid() &&
- search->happens_before(reader))
- break;
- }
-
- return true;
-}
-
-/**
- * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
- * some constraints. This method checks one the following constraint (others
- * require compiler support):
- *
- * If X --hb-> Y --mo-> Z, then X should not read from Z.
- */
-bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
-{
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(reader->get_location());
- unsigned int i;
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- const ModelAction *write_after_read = NULL;
-
- /* 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;
-
- if (!reader->happens_before(act))
- break;
- else if (act->is_write())
- write_after_read = act;
- else if (act->is_read()&&act->get_reads_from()!=NULL&&act!=reader) {
- write_after_read = act->get_reads_from();
- }
- }
-
- if (write_after_read && write_after_read!=writer && mo_graph->checkReachable(write_after_read, writer))
- return false;
- }
- return true;
-}
-
-/**
- * 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.
- *
- * @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 with certainty
- * @param pending A pass-by-reference style return parameter which is only used
- * when returning false (i.e., uncertain). Returns most information regarding
- * an uncertain release sequence, including any write operations that might
- * break the sequence.
- * @return true, if the ModelChecker is certain that release_heads is complete;
- * false otherwise
- */
-bool ModelChecker::release_seq_heads(const ModelAction *rf,
- rel_heads_list_t *release_heads,
- struct release_seq *pending) const
-{
- /* Only check for release sequences if there are no cycles */
- if (mo_graph->checkForCycles())
- return false;
-
- while (rf) {
- ASSERT(rf->is_write());
-
- if (rf->is_release())
- release_heads->push_back(rf);
- if (!rf->is_rmw())
- break; /* End of RMW chain */
-
- /** @todo Need to be smarter here... In the linux lock
- * example, this will run to the beginning of the program for
- * every acquire. */
- /** @todo The way to be smarter here is to keep going until 1
- * thread has a release preceded by an acquire and you've seen
- * both. */
-
- /* acq_rel RMW is a sufficient stopping condition */
- if (rf->is_acquire() && rf->is_release())
- return true; /* complete */
-
- rf = rf->get_reads_from();
- };
- if (!rf) {
- /* read from future: need to settle this later */
- pending->rf = NULL;
- return false; /* incomplete */
- }
-
- 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<action_list_t> *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));
-
- pending->writes.clear();
-
- 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;
-
- ModelAction *last = get_last_action(int_to_id(i));
- Thread *th = get_thread(int_to_id(i));
- if ((last && rf->happens_before(last)) ||
- !scheduler->is_enabled(th) ||
- th->is_complete())
- future_ordered = true;
-
- ASSERT(!th->is_model_thread() || future_ordered);
-
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- const ModelAction *act = *rit;
- /* Reach synchronization -> this thread is complete */
- if (act->happens_before(release))
- break;
- if (rf->happens_before(act)) {
- future_ordered = true;
- continue;
- }
-
- /* Only non-RMW writes can break release sequences */
- if (!act->is_write() || act->is_rmw())
- 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 */
- }
- /* act may break release sequence */
- pending->writes.push_back(act);
- certain = false;
- }
- if (!future_ordered)
- certain = false; /* This thread is uncertain */
- }
-
- if (certain) {
- release_heads->push_back(release);
- pending->writes.clear();
- } else {
- pending->release = release;
- pending->rf = rf;
- }
- 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_heads
- */
-void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
-{
- const ModelAction *rf = act->get_reads_from();
- struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
- sequence->acquire = act;
-
- if (!release_seq_heads(rf, release_heads, sequence)) {
- /* add act to 'lazy checking' list */
- pending_rel_seqs->push_back(sequence);
- } else {
- snapshot_free(sequence);
- }
-}
-
-/**
- * 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. A NULL value means to check all locations.
- * @param work_queue The work queue to which to add work items as they are
- * generated
- * @return True if any updates occurred (new synchronization, new mo_graph
- * edges)
- */
-bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
-{
- bool updated = false;
- std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
- while (it != pending_rel_seqs->end()) {
- struct release_seq *pending = *it;
- ModelAction *act = pending->acquire;
-
- /* Only resolve sequences on the given location, if provided */
- if (location && act->get_location() != location) {
- it++;
- continue;
- }
-
- const ModelAction *rf = act->get_reads_from();
- rel_heads_list_t release_heads;
- bool complete;
- complete = release_seq_heads(rf, &release_heads, pending);
- for (unsigned int i = 0; i < release_heads.size(); i++) {
- if (!act->has_synchronized_with(release_heads[i])) {
- if (act->synchronize_with(release_heads[i]))
- updated = true;
- else
- set_bad_synchronization();
- }
- }
-
- if (updated) {
- /* Re-check all pending release sequences */
- work_queue->push_back(CheckRelSeqWorkEntry(NULL));
- /* Re-check act for mo_graph edges */
- work_queue->push_back(MOEdgeWorkEntry(act));
-
- /* propagate synchronization to later actions */
- action_list_t::reverse_iterator rit = action_trace->rbegin();
- for (; (*rit) != act; rit++) {
- ModelAction *propagate = *rit;
- if (act->happens_before(propagate)) {
- propagate->synchronize_with(act);
- /* Re-check 'propagate' for mo_graph edges */
- work_queue->push_back(MOEdgeWorkEntry(propagate));
- }
- }
- }
- if (complete) {
- it = pending_rel_seqs->erase(it);
- snapshot_free(pending);
- } else {
- it++;
- }
- }
-
- // If we resolved promises or data races, see if we have realized a data race.
- if (checkDataRaces()) {
- set_assert();
- }
-
- return updated;
-}
-
-/**
- * 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);
-
- obj_map->get_safe_ptr(act->get_location())->push_back(act);