#include "model.h"
#include "action.h"
-#include "tree.h"
+#include "nodestack.h"
#include "schedule.h"
#include "snapshot-interface.h"
-#undef DEBUG
#include "common.h"
+#include "clockvector.h"
+#include "cyclegraph.h"
#define INITIAL_THREAD_ID 0
-class Backtrack {
-public:
- Backtrack(ModelAction *d, action_list_t *t) {
- diverge = d;
- actionTrace = t;
- iter = actionTrace->begin();
- }
- ModelAction * get_diverge() { return diverge; }
- action_list_t * get_trace() { return actionTrace; }
- void advance_state() { iter++; }
- ModelAction * get_state() {
- return iter == actionTrace->end() ? NULL : *iter;
- }
-private:
- ModelAction *diverge;
- action_list_t *actionTrace;
- /* points to position in actionTrace as we replay */
- action_list_t::iterator iter;
-};
-
ModelChecker *model;
-void free_action_list(action_list_t *list)
-{
- action_list_t::iterator it;
- for (it = list->begin(); it != list->end(); it++)
- delete (*it);
- delete list;
-}
-
+/** @brief Constructor */
ModelChecker::ModelChecker()
:
/* Initialize default scheduler */
num_executions(0),
current_action(NULL),
- exploring(NULL),
+ diverge(NULL),
nextThread(THREAD_ID_T_NONE),
action_trace(new action_list_t()),
- rootNode(new TreeNode()),
- currentNode(rootNode)
+ thread_map(new std::map<int, Thread *>),
+ obj_map(new std::map<const void *, action_list_t>()),
+ obj_thrd_map(new std::map<void *, std::vector<action_list_t> >()),
+ thrd_last_action(new std::vector<ModelAction *>(1)),
+ node_stack(new NodeStack()),
+ next_backtrack(NULL),
+ cyclegraph(new CycleGraph())
{
}
+/** @brief Destructor */
ModelChecker::~ModelChecker()
{
- std::map<int, class Thread *, std::less< int >, MyAlloc< std::pair< int, class Thread * > > >::iterator it;
- for (it = thread_map.begin(); it != thread_map.end(); it++)
+ std::map<int, Thread *>::iterator it;
+ for (it = thread_map->begin(); it != thread_map->end(); it++)
delete (*it).second;
- thread_map.clear();
-
- free_action_list(action_trace);
+ delete thread_map;
+ delete obj_thrd_map;
+ delete obj_map;
+ delete action_trace;
+ delete thrd_last_action;
+ delete node_stack;
delete scheduler;
- delete rootNode;
+ delete cyclegraph;
}
+/**
+ * Restores user program to initial state and resets all model-checker data
+ * structures.
+ */
void ModelChecker::reset_to_initial_state()
{
DEBUG("+++ Resetting to initial state +++\n");
- std::map<int, class Thread *, std::less< int >, MyAlloc< std::pair< int, class Thread * > > >::iterator it;
- for (it = thread_map.begin(); it != thread_map.end(); it++)
- delete (*it).second;
- thread_map.clear();
- action_trace = new action_list_t();
- currentNode = rootNode;
+ node_stack->reset_execution();
current_action = NULL;
next_thread_id = INITIAL_THREAD_ID;
used_sequence_numbers = 0;
nextThread = 0;
- /* scheduler reset ? */
+ next_backtrack = NULL;
+ snapshotObject->backTrackBeforeStep(0);
}
+/** @returns a thread ID for a new Thread */
thread_id_t ModelChecker::get_next_id()
{
return next_thread_id++;
}
-int ModelChecker::get_next_seq_num()
+/** @returns the number of user threads created during this execution */
+int ModelChecker::get_num_threads()
+{
+ return next_thread_id;
+}
+
+/** @returns a sequence number for a new ModelAction */
+modelclock_t ModelChecker::get_next_seq_num()
{
return ++used_sequence_numbers;
}
+/**
+ * Performs the "scheduling" for the model-checker. That is, it checks if the
+ * model-checker has selected a "next thread to run" and returns it, if
+ * available. This function should be called from the Scheduler routine, where
+ * the Scheduler falls back to a default scheduling routine if needed.
+ *
+ * @return The next thread chosen by the model-checker. If the model-checker
+ * makes no selection, retuns NULL.
+ */
Thread * ModelChecker::schedule_next_thread()
{
Thread *t;
if (nextThread == THREAD_ID_T_NONE)
return NULL;
- t = thread_map[id_to_int(nextThread)];
+ t = (*thread_map)[id_to_int(nextThread)];
ASSERT(t != NULL);
return t;
}
-/*
- * get_next_replay_thread() - Choose the next thread in the replay sequence
+/**
+ * Choose the next thread in the replay sequence.
*
- * If we've reached the 'diverge' point, then we pick a thread from the
- * backtracking set.
- * Otherwise, we simply return the next thread in the sequence.
+ * 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.
*/
thread_id_t ModelChecker::get_next_replay_thread()
{
thread_id_t tid;
/* Have we completed exploring the preselected path? */
- if (exploring == NULL)
+ if (diverge == NULL)
return THREAD_ID_T_NONE;
/* Else, we are trying to replay an execution */
- exploring->advance_state();
-
- ASSERT(exploring->get_state() != NULL);
-
- next = exploring->get_state();
-
- if (next == exploring->get_diverge()) {
- TreeNode *node = next->get_treenode();
-
- /* Reached divergence point; discard our current 'exploring' */
- DEBUG("*** Discard 'Backtrack' object ***\n");
- tid = node->getNextBacktrack();
- delete exploring;
- exploring = NULL;
+ next = node_stack->get_next()->get_action();
+
+ if (next == diverge) {
+ Node *nextnode = next->get_node();
+ /* Reached divergence point */
+ if (nextnode->increment_read_from()) {
+ /* The next node will read from a different value */
+ tid = next->get_tid();
+ node_stack->pop_restofstack(2);
+ } else {
+ /* Make a different thread execute for next step */
+ Node *node = nextnode->get_parent();
+ tid = node->get_next_backtrack();
+ node_stack->pop_restofstack(1);
+ }
+ DEBUG("*** Divergence point ***\n");
+ diverge = NULL;
} else {
tid = next->get_tid();
}
return tid;
}
+/**
+ * Queries the model-checker for more executions to explore and, if one
+ * exists, resets the model-checker state to execute a new execution.
+ *
+ * @return If there are more executions to explore, return true. Otherwise,
+ * return false.
+ */
bool ModelChecker::next_execution()
{
DBG();
num_executions++;
- print_summary();
- if ((exploring = model->get_next_backtrack()) == NULL)
+
+ if (isfeasible() || DBG_ENABLED())
+ print_summary();
+
+ if ((diverge = model->get_next_backtrack()) == NULL)
return false;
if (DBG_ENABLED()) {
printf("Next execution will diverge at:\n");
- exploring->get_diverge()->print();
- print_list(exploring->get_trace());
+ diverge->print();
}
model->reset_to_initial_state();
action_type type = act->get_type();
switch (type) {
- case THREAD_CREATE:
- case THREAD_YIELD:
- case THREAD_JOIN:
- return NULL;
case ATOMIC_READ:
case ATOMIC_WRITE:
- default:
+ case ATOMIC_RMW:
break;
+ default:
+ return NULL;
}
/* linear search: from most recent to oldest */
+ action_list_t *list = &(*obj_map)[act->get_location()];
action_list_t::reverse_iterator rit;
- for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *prev = *rit;
- if (act->is_dependent(prev))
+ if (act->is_synchronizing(prev))
return prev;
}
return NULL;
void ModelChecker::set_backtracking(ModelAction *act)
{
ModelAction *prev;
- TreeNode *node;
+ Node *node;
Thread *t = get_thread(act->get_tid());
prev = get_last_conflict(act);
if (prev == NULL)
return;
- node = prev->get_treenode();
+ node = prev->get_node()->get_parent();
- while (t && !node->is_enabled(t))
+ while (!node->is_enabled(t))
t = t->get_parent();
/* Check if this has been explored already */
- if (node->hasBeenExplored(t->get_id()))
+ if (node->has_been_explored(t->get_id()))
return;
+
+ /* Cache the latest backtracking point */
+ if (!next_backtrack || *prev > *next_backtrack)
+ next_backtrack = prev;
+
/* If this is a new backtracking point, mark the tree */
- if (node->setBacktrack(t->get_id()) != 0)
+ if (!node->set_backtrack(t->get_id()))
return;
-
DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
prev->get_tid(), t->get_id());
if (DBG_ENABLED()) {
prev->print();
act->print();
}
-
- Backtrack *back = new Backtrack(prev, action_trace);
- backtrack_list.push_back(back);
}
-Backtrack * ModelChecker::get_next_backtrack()
+ModelAction * ModelChecker::get_next_backtrack()
{
- Backtrack *next;
- if (backtrack_list.empty())
- return NULL;
- next = backtrack_list.back();
- backtrack_list.pop_back();
+ ModelAction *next = next_backtrack;
+ next_backtrack = NULL;
return next;
}
void ModelChecker::check_current_action(void)
{
ModelAction *curr = this->current_action;
+ ModelAction *tmp;
current_action = NULL;
if (!curr) {
DEBUG("trying to push NULL action...\n");
return;
}
+ tmp = node_stack->explore_action(curr);
+ if (tmp) {
+ /* Discard duplicate ModelAction; use action from NodeStack */
+ delete curr;
+ curr = tmp;
+ } else {
+ /*
+ * Perform one-time actions when pushing new ModelAction onto
+ * NodeStack
+ */
+ curr->create_cv(get_parent_action(curr->get_tid()));
+ /* Build may_read_from set */
+ if (curr->is_read())
+ build_reads_from_past(curr);
+ }
+
+ /* Assign 'creation' parent */
+ if (curr->get_type() == THREAD_CREATE) {
+ Thread *th = (Thread *)curr->get_location();
+ th->set_creation(curr);
+ }
+
nextThread = get_next_replay_thread();
- curr->set_node(currentNode);
+
+ Node *currnode = curr->get_node();
+ Node *parnode = currnode->get_parent();
+
+ if (!parnode->backtrack_empty()||!currnode->readsfrom_empty())
+ if (!next_backtrack || *curr > *next_backtrack)
+ next_backtrack = curr;
+
set_backtracking(curr);
- currentNode = currentNode->explore_child(curr);
- this->action_trace->push_back(curr);
+
+ /* Assign reads_from values */
+ /* TODO: perform release/acquire synchronization here; include
+ * reads_from as ModelAction member? */
+ Thread *th = get_thread(curr->get_tid());
+ uint64_t value = VALUE_NONE;
+ if (curr->is_read()) {
+ const ModelAction *reads_from = curr->get_node()->get_read_from();
+ value = reads_from->get_value();
+ /* Assign reads_from, perform release/acquire synchronization */
+ curr->read_from(reads_from);
+ r_modification_order(curr,reads_from);
+ } else if (curr->is_write()) {
+ w_modification_order(curr);
+ }
+
+ th->set_return_value(value);
+
+ /* Add action to list last. */
+ add_action_to_lists(curr);
}
-void ModelChecker::print_summary(void)
+bool ModelChecker::isfeasible() {
+ return !cyclegraph->checkForCycles();
+}
+
+void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *rf) {
+ std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[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;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+
+ /* Include at most one act per-thread that "happens before" curr */
+ if (act->happens_before(curr)) {
+ if (act->is_read()) {
+ const ModelAction * prevreadfrom=act->get_reads_from();
+ if (rf!=prevreadfrom)
+ cyclegraph->addEdge(rf, prevreadfrom);
+ } else if (rf!=act) {
+ cyclegraph->addEdge(rf, act);
+ }
+ break;
+ }
+ }
+ }
+}
+
+void ModelChecker::w_modification_order(ModelAction * curr) {
+ std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[curr->get_location()];
+ unsigned int i;
+ 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->get_location());
+ if (last_seq_cst!=NULL)
+ cyclegraph->addEdge(curr, last_seq_cst);
+ }
+
+ /* 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 */
+ if (act->happens_before(curr)) {
+ if (act->is_read()) {
+ cyclegraph->addEdge(curr, act->get_reads_from());
+ } else
+ cyclegraph->addEdge(curr, act);
+ break;
+ }
+ }
+ }
+}
+
+/**
+ * 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)
{
- printf("\n");
- printf("Number of executions: %d\n", num_executions);
- printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
+ int tid = id_to_int(act->get_tid());
+ action_trace->push_back(act);
- scheduler->print();
+ (*obj_map)[act->get_location()].push_back(act);
- print_list(action_trace);
- printf("\n");
+ std::vector<action_list_t> *vec = &(*obj_thrd_map)[act->get_location()];
+ if (tid >= (int)vec->size())
+ vec->resize(next_thread_id);
+ (*vec)[tid].push_back(act);
+
+ if ((int)thrd_last_action->size() <= tid)
+ thrd_last_action->resize(get_num_threads());
+ (*thrd_last_action)[tid] = act;
+}
+
+ModelAction * ModelChecker::get_last_action(thread_id_t tid)
+{
+ int nthreads = get_num_threads();
+ if ((int)thrd_last_action->size() < nthreads)
+ thrd_last_action->resize(nthreads);
+ return (*thrd_last_action)[id_to_int(tid)];
+}
+
+/**
+ * Gets the last memory_order_seq_cst action (in the total global sequence)
+ * performed on a particular object (i.e., memory location).
+ * @param location The object location to check
+ * @return The last seq_cst action performed
+ */
+ModelAction * ModelChecker::get_last_seq_cst(const void *location)
+{
+ action_list_t *list = &(*obj_map)[location];
+ /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++)
+ if ((*rit)->is_write() && (*rit)->is_seqcst())
+ return *rit;
+ return NULL;
+}
+
+ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
+{
+ ModelAction *parent = get_last_action(tid);
+ if (!parent)
+ parent = get_thread(tid)->get_creation();
+ return parent;
+}
+ClockVector * ModelChecker::get_cv(thread_id_t tid) {
+ return get_parent_action(tid)->get_cv();
}
-void ModelChecker::print_list(action_list_t *list)
+/**
+ * Build up an initial set of all past writes that this 'read' action may read
+ * from. This set is determined by the clock vector's "happens before"
+ * relationship.
+ * @param curr is the current ModelAction that we are exploring; it must be a
+ * 'read' operation.
+ */
+void ModelChecker::build_reads_from_past(ModelAction *curr)
+{
+ std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[curr->get_location()];
+ unsigned int i;
+ ASSERT(curr->is_read());
+
+ ModelAction *last_seq_cst = NULL;
+
+ /* Track whether this object has been initialized */
+ bool initialized = false;
+
+ if (curr->is_seqcst()) {
+ last_seq_cst = get_last_seq_cst(curr->get_location());
+ /* We have to at least see the last sequentially consistent write,
+ so we are initialized. */
+ if (last_seq_cst != NULL)
+ initialized = 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;
+
+ /* Only consider 'write' actions */
+ if (!act->is_write())
+ continue;
+
+ /* Don't consider more than one seq_cst write if we are a seq_cst read. */
+ if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
+ DEBUG("Adding action to may_read_from:\n");
+ if (DBG_ENABLED()) {
+ act->print();
+ curr->print();
+ }
+ curr->get_node()->add_read_from(act);
+ }
+
+ /* Include at most one act per-thread that "happens before" curr */
+ if (act->happens_before(curr)) {
+ initialized = true;
+ break;
+ }
+ }
+ }
+
+ if (!initialized) {
+ /* TODO: need a more informative way of reporting errors */
+ printf("ERROR: may read from uninitialized atomic\n");
+ }
+
+ if (DBG_ENABLED() || !initialized) {
+ printf("Reached read action:\n");
+ curr->print();
+ printf("Printing may_read_from\n");
+ curr->get_node()->print_may_read_from();
+ printf("End printing may_read_from\n");
+ }
+
+ ASSERT(initialized);
+}
+
+static void print_list(action_list_t *list)
{
action_list_t::iterator it;
printf("---------------------------------------------------------------------\n");
}
+void ModelChecker::print_summary(void)
+{
+ printf("\n");
+ printf("Number of executions: %d\n", num_executions);
+ printf("Total nodes created: %d\n", node_stack->get_total_nodes());
+
+ scheduler->print();
+
+ if (!isfeasible())
+ printf("INFEASIBLE EXECUTION!\n");
+ print_list(action_trace);
+ printf("\n");
+}
+
int ModelChecker::add_thread(Thread *t)
{
- thread_map[id_to_int(t->get_id())] = t;
+ (*thread_map)[id_to_int(t->get_id())] = t;
scheduler->add_thread(t);
return 0;
}
scheduler->remove_thread(t);
}
+/**
+ * Switch from a user-context to the "master thread" context (a.k.a. system
+ * 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()).
+ * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
+ */
int ModelChecker::switch_to_master(ModelAction *act)
{
Thread *old;
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