*/
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();
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<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++;
+ }
+
+ 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;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==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;j<act->get_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.
projects / c11tester.git / blobdiff