node_stack(new NodeStack()),
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 */
DEBUG("+++ Resetting to initial state +++\n");
node_stack->reset_execution();
failed_promise = false;
+ too_many_reads = false;
reset_asserted();
snapshotObject->backTrackBeforeStep(0);
}
*/
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 {
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;
if (resolve_promises(curr))
updated = true;
+ mo_graph->commitChanges();
}
if (updated)
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();
/** @returns whether the current partial trace must be a prefix of a
* feasible trace. */
-
bool ModelChecker::isfeasibleprefix() {
- return promises->size()==0;
+ 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. */
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<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 */
+ 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.
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);
}
std::list<ModelAction *> *list;
list = lazy_sync_with_release->get_safe_ptr(act->get_location());
list->push_back(act);
+ (*lazy_sync_size)++;
}
}
propagate->synchronize_with(act);
}
}
- if (complete)
+ if (complete) {
it = list->erase(it);
- else
+ (*lazy_sync_size)--;
+ } else
it++;
}
projects / model-checker.git / blobdiff