}
/**
- * 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 * 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 NULL;
return next;
}
+/**
+ * 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
}
}
- /* 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);
- } else if (curr->get_type() == THREAD_JOIN) {
+ break;
+ }
+ 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);
- } else if (curr->get_type() == THREAD_FINISH) {
+ 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;
}
-
- /* Deal with new thread */
- if (curr->get_type() == THREAD_START)
+ 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()) {
- 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);
+ updated=process_read(curr, th, second_part_of_rmw);
+ }
- 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;
- }
+ if (curr->is_write()) {
+ bool updated_mod_order=w_modification_order(curr);
+ bool updated_promises=resolve_promises(curr);
+ updated=updated_mod_order|updated_promises;
- 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();
+ th->set_return_value(VALUE_NONE);
}
if (updated)
resolve_release_sequences(curr->get_location());
- th->set_return_value(value);
-
/* 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 (!priv->next_backtrack || *curr > *priv->next_backtrack)
- priv->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);
- /* 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();
+ return get_next_thread(curr);
}
/** @returns whether the current partial trace must be a prefix of a
/* 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) &&
projects / model-checker.git / blobdiff