#include "cyclegraph.h"
#include "promise.h"
#include "datarace.h"
+#include "mutex.h"
#define INITIAL_THREAD_ID 0
/* Initialize default scheduler */
scheduler(new Scheduler()),
num_executions(0),
+ num_feasible_executions(0),
params(params),
diverge(NULL),
action_trace(new action_list_t()),
thread_map(new HashTable<int, Thread *, int>()),
obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
+ lock_waiters_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
promises(new std::vector<Promise *>()),
- lazy_sync_with_release(new HashTable<void *, std::list<ModelAction *>, uintptr_t, 4>()),
+ futurevalues(new std::vector<struct PendingFutureValue>()),
+ lazy_sync_with_release(new HashTable<void *, action_list_t, uintptr_t, 4>()),
thrd_last_action(new std::vector<ModelAction *>(1)),
node_stack(new NodeStack()),
mo_graph(new CycleGraph()),
delete obj_thrd_map;
delete obj_map;
+ delete lock_waiters_map;
delete action_trace;
for (unsigned int i = 0; i < promises->size(); i++)
snapshotObject->backTrackBeforeStep(0);
}
-/** @returns a thread ID for a new Thread */
+/** @return a thread ID for a new Thread */
thread_id_t ModelChecker::get_next_id()
{
return priv->next_thread_id++;
}
-/** @returns the number of user threads created during this execution */
+/** @return the number of user threads created during this execution */
int ModelChecker::get_num_threads()
{
return priv->next_thread_id;
}
-/** @returns a sequence number for a new ModelAction */
+/** @return a sequence number for a new ModelAction */
modelclock_t ModelChecker::get_next_seq_num()
{
return ++priv->used_sequence_numbers;
{
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();
+ if (curr!=NULL) {
+ /* 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)
DBG();
num_executions++;
+ if (isfinalfeasible())
+ num_feasible_executions++;
if (isfinalfeasible() || DBG_ENABLED())
print_summary();
ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
{
- action_type type = act->get_type();
-
- switch (type) {
- case ATOMIC_READ:
- case ATOMIC_WRITE:
- case ATOMIC_RMW:
- break;
- default:
- return NULL;
+ switch (act->get_type()) {
+ case ATOMIC_READ:
+ case ATOMIC_WRITE:
+ case ATOMIC_RMW: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = obj_map->get_safe_ptr(act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (act->is_synchronizing(prev))
+ return prev;
+ }
+ break;
}
- /* linear search: from most recent to oldest */
- action_list_t *list = obj_map->get_safe_ptr(act->get_location());
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *prev = *rit;
- if (act->is_synchronizing(prev))
- return prev;
+ case ATOMIC_LOCK:
+ case ATOMIC_TRYLOCK: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = obj_map->get_safe_ptr(act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (act->is_conflicting_lock(prev))
+ return prev;
+ }
+ break;
+ }
+ case ATOMIC_UNLOCK: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = obj_map->get_safe_ptr(act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (!act->same_thread(prev)&&prev->is_failed_trylock())
+ return prev;
+ }
+ break;
+ }
+ default:
+ break;
}
return NULL;
}
void ModelChecker::set_backtracking(ModelAction *act)
{
- ModelAction *prev;
- Node *node;
Thread *t = get_thread(act);
-
- prev = get_last_conflict(act);
+ ModelAction * prev = get_last_conflict(act);
if (prev == NULL)
return;
- node = prev->get_node()->get_parent();
-
- while (!node->is_enabled(t))
- t = t->get_parent();
-
- /* Check if this has been explored already */
- if (node->has_been_explored(t->get_id()))
- return;
+ Node * node = prev->get_node()->get_parent();
- /* Cache the latest backtracking point */
- if (!priv->next_backtrack || *prev > *priv->next_backtrack)
- priv->next_backtrack = prev;
+ int low_tid, high_tid;
+ if (node->is_enabled(t)) {
+ low_tid=id_to_int(act->get_tid());
+ high_tid=low_tid+1;
+ } else {
+ low_tid=0;
+ high_tid=get_num_threads();
+ }
+
+ for(int i=low_tid;i<high_tid;i++) {
+ thread_id_t tid=int_to_id(i);
+ if (!node->is_enabled(tid))
+ continue;
- /* If this is a new backtracking point, mark the tree */
- 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();
+ /* Check if this has been explored already */
+ if (node->has_been_explored(tid))
+ continue;
+
+ /* Cache the latest backtracking point */
+ if (!priv->next_backtrack || *prev > *priv->next_backtrack)
+ priv->next_backtrack = prev;
+
+ /* If this is a new backtracking point, mark the tree */
+ if (!node->set_backtrack(tid))
+ continue;
+ DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
+ prev->get_tid(), t->get_id());
+ if (DBG_ENABLED()) {
+ prev->print();
+ act->print();
+ }
}
}
/**
* 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) {
+bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
+{
uint64_t value;
- bool updated=false;
- while(true) {
+ bool updated = false;
+ while (true) {
const ModelAction *reads_from = curr->get_node()->get_read_from();
if (reads_from != NULL) {
mo_graph->startChanges();
value = reads_from->get_value();
- /* Assign reads_from, perform release/acquire synchronization */
- curr->read_from(reads_from);
+ bool r_status = false;
+
if (!second_part_of_rmw) {
- check_recency(curr,false);
+ check_recency(curr);
+ r_status = r_modification_order(curr, reads_from);
}
- 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())) {
+ if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) {
mo_graph->rollbackChanges();
- too_many_reads=false;
+ too_many_reads = false;
continue;
}
+ curr->read_from(reads_from);
mo_graph->commitChanges();
updated |= r_status;
- } else {
+ } else if (!second_part_of_rmw) {
/* Read from future value */
value = curr->get_node()->get_future_value();
modelclock_t expiration = curr->get_node()->get_future_value_expiration();
Promise *valuepromise = new Promise(curr, value, expiration);
promises->push_back(valuepromise);
}
- th->set_return_value(value);
+ get_thread(curr)->set_return_value(value);
return updated;
}
}
+/**
+ * Processes a lock, trylock, or unlock model action. @param curr is
+ * the read model action to process.
+ *
+ * The try lock operation checks whether the lock is taken. If not,
+ * it falls to the normal lock operation case. If so, it returns
+ * fail.
+ *
+ * The lock operation has already been checked that it is enabled, so
+ * it just grabs the lock and synchronizes with the previous unlock.
+ *
+ * The unlock operation has to re-enable all of the threads that are
+ * waiting on the lock.
+ */
+
+void ModelChecker::process_mutex(ModelAction *curr) {
+ std::mutex * mutex=(std::mutex *) curr->get_location();
+ struct std::mutex_state * state=mutex->get_state();
+ switch(curr->get_type()) {
+ case ATOMIC_TRYLOCK: {
+ bool success=!state->islocked;
+ curr->set_try_lock(success);
+ if (!success) {
+ get_thread(curr)->set_return_value(0);
+ break;
+ }
+ get_thread(curr)->set_return_value(1);
+ }
+ //otherwise fall into the lock case
+ case ATOMIC_LOCK: {
+ if (curr->get_cv()->getClock(state->alloc_tid)<=state->alloc_clock) {
+ printf("Lock access before initialization\n");
+ set_assert();
+ }
+ state->islocked=true;
+ ModelAction *unlock=get_last_unlock(curr);
+ //synchronize with the previous unlock statement
+ if ( unlock != NULL )
+ curr->synchronize_with(unlock);
+ break;
+ }
+ case ATOMIC_UNLOCK: {
+ //unlock the lock
+ state->islocked=false;
+ //wake up the other threads
+ action_list_t * waiters = lock_waiters_map->get_safe_ptr(curr->get_location());
+ //activate all the waiting threads
+ for(action_list_t::iterator rit = waiters->begin(); rit!=waiters->end(); rit++) {
+ scheduler->add_thread(get_thread((*rit)->get_tid()));
+ }
+ waiters->clear();
+ break;
+ }
+ default:
+ ASSERT(0);
+ }
+}
+
+
+/**
+ * Process a write ModelAction
+ * @param curr The ModelAction to process
+ * @return True if the mo_graph was updated or promises were resolved
+ */
+bool ModelChecker::process_write(ModelAction *curr)
+{
+ bool updated_mod_order = w_modification_order(curr);
+ bool updated_promises = resolve_promises(curr);
+
+ if (promises->size() == 0) {
+ for (unsigned int i = 0; i<futurevalues->size(); i++) {
+ struct PendingFutureValue pfv = (*futurevalues)[i];
+ if (pfv.act->get_node()->add_future_value(pfv.value, pfv.expiration) &&
+ (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
+ priv->next_backtrack = pfv.act;
+ }
+ futurevalues->resize(0);
+ }
+
+ mo_graph->commitChanges();
+ get_thread(curr)->set_return_value(VALUE_NONE);
+ return updated_mod_order || updated_promises;
+}
+
+/**
+ * Initialize the current action by performing one or more of the following
+ * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
+ * in the NodeStack, manipulating backtracking sets, allocating and
+ * initializing clock vectors, and computing the promises to fulfill.
+ *
+ * @param curr The current action, as passed from the user context; may be
+ * freed/invalidated after the execution of this function
+ * @return The current action, as processed by the ModelChecker. Is only the
+ * same as the parameter @a curr if this is a newly-explored action.
+ */
+ModelAction * ModelChecker::initialize_curr_action(ModelAction *curr)
+{
+ ModelAction *newcurr;
+
+ if (curr->is_rmwc() || curr->is_rmw()) {
+ newcurr = process_rmw(curr);
+ delete curr;
+ compute_promises(newcurr);
+ return newcurr;
+ }
+
+ newcurr = node_stack->explore_action(curr, scheduler->get_enabled());
+ if (newcurr) {
+ /* First restore type and order in case of RMW operation */
+ if (curr->is_rmwr())
+ newcurr->copy_typeandorder(curr);
+
+ ASSERT(curr->get_location()==newcurr->get_location());
+ newcurr->copy_from_new(curr);
+
+ /* Discard duplicate ModelAction; use action from NodeStack */
+ delete curr;
+
+ /* If we have diverged, we need to reset the clock vector. */
+ if (diverge == NULL)
+ newcurr->create_cv(get_parent_action(newcurr->get_tid()));
+ } else {
+ newcurr = curr;
+ /*
+ * Perform one-time actions when pushing new ModelAction onto
+ * NodeStack
+ */
+ curr->create_cv(get_parent_action(curr->get_tid()));
+ if (curr->is_write())
+ compute_promises(curr);
+ }
+ return newcurr;
+}
+
+/**
+ * This method checks whether a model action is enabled at the given point.
+ * At this point, it checks whether a lock operation would be successful at this point.
+ * If not, it puts the thread in a waiter list.
+ * @param curr is the ModelAction to check whether it is enabled.
+ * @return a bool that indicates whether the action is enabled.
+ */
+
+bool ModelChecker::check_action_enabled(ModelAction *curr) {
+ if (curr->is_lock()) {
+ std::mutex * lock=(std::mutex *) curr->get_location();
+ struct std::mutex_state * state = lock->get_state();
+ if (state->islocked) {
+ //Stick the action in the appropriate waiting queue
+ lock_waiters_map->get_safe_ptr(curr->get_location())->push_back(curr);
+ return false;
+ }
+ }
+
+ return true;
+}
+
/**
* This is the heart of the model checker routine. It performs model-checking
* actions corresponding to a given "current action." Among other processes, it
*/
Thread * ModelChecker::check_current_action(ModelAction *curr)
{
- bool second_part_of_rmw = false;
-
ASSERT(curr);
- if (curr->is_rmwc() || curr->is_rmw()) {
- ModelAction *tmp = process_rmw(curr);
- second_part_of_rmw = true;
- delete curr;
- curr = tmp;
- compute_promises(curr);
- } else {
- ModelAction *tmp = node_stack->explore_action(curr);
- if (tmp) {
- /* Discard duplicate ModelAction; use action from NodeStack */
- /* First restore type and order in case of RMW operation */
- if (curr->is_rmwr())
- tmp->copy_typeandorder(curr);
-
- /* If we have diverged, we need to reset the clock vector. */
- if (diverge == NULL)
- tmp->create_cv(get_parent_action(tmp->get_tid()));
-
- 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);
- if (curr->is_write())
- compute_promises(curr);
- }
+ bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
+
+ if (!check_action_enabled(curr)) {
+ //we'll make the execution look like we chose to run this action
+ //much later...when a lock is actually available to relese
+ get_current_thread()->set_pending(curr);
+ remove_thread(get_current_thread());
+ return get_next_thread(NULL);
}
+ ModelAction *newcurr = initialize_curr_action(curr);
+
+ /* Add the action to lists before any other model-checking tasks */
+ if (!second_part_of_rmw)
+ add_action_to_lists(newcurr);
+
+ /* Build may_read_from set for newly-created actions */
+ if (curr == newcurr && curr->is_read())
+ build_reads_from_past(curr);
+ curr = newcurr;
+
/* Thread specific actions */
- switch(curr->get_type()) {
+ switch (curr->get_type()) {
case THREAD_CREATE: {
Thread *th = (Thread *)curr->get_location();
th->set_creation(curr);
if (!blocking->is_complete()) {
blocking->push_wait_list(curr);
scheduler->sleep(waiting);
+ } else {
+ do_complete_join(curr);
}
break;
}
ModelAction *act = th->pop_wait_list();
Thread *wake = get_thread(act);
scheduler->wake(wake);
+ do_complete_join(act);
}
th->complete();
break;
break;
}
- Thread *th = get_thread(curr);
+ work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
- bool updated = false;
- if (curr->is_read()) {
- updated=process_read(curr, th, second_part_of_rmw);
- }
+ while (!work_queue.empty()) {
+ WorkQueueEntry work = work_queue.front();
+ work_queue.pop_front();
- if (curr->is_write()) {
- bool updated_mod_order=w_modification_order(curr);
- bool updated_promises=resolve_promises(curr);
- updated=updated_mod_order|updated_promises;
+ switch (work.type) {
+ case WORK_CHECK_CURR_ACTION: {
+ ModelAction *act = work.action;
+ bool updated = false;
+ if (act->is_read() && process_read(act, second_part_of_rmw))
+ updated = true;
- mo_graph->commitChanges();
- th->set_return_value(VALUE_NONE);
- }
+ if (act->is_write() && process_write(act))
+ updated = true;
- if (updated)
- resolve_release_sequences(curr->get_location());
+ if (act->is_mutex_op())
+ process_mutex(act);
- /* Add action to list. */
- if (!second_part_of_rmw)
- add_action_to_lists(curr);
+ if (updated)
+ work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
+ break;
+ }
+ case WORK_CHECK_RELEASE_SEQ:
+ resolve_release_sequences(work.location, &work_queue);
+ break;
+ case WORK_CHECK_MO_EDGES: {
+ /** @todo Complete verification of work_queue */
+ ModelAction *act = work.action;
+ bool updated = false;
+
+ if (act->is_read()) {
+ if (r_modification_order(act, act->get_reads_from()))
+ updated = true;
+ }
+ if (act->is_write()) {
+ if (w_modification_order(act))
+ updated = true;
+ }
+
+ if (updated)
+ work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
+ break;
+ }
+ default:
+ ASSERT(false);
+ break;
+ }
+ }
check_curr_backtracking(curr);
-
+
set_backtracking(curr);
return get_next_thread(curr);
}
+/**
+ * Complete a THREAD_JOIN operation, by synchronizing with the THREAD_FINISH
+ * operation from the Thread it is joining with. Must be called after the
+ * completion of the Thread in question.
+ * @param join The THREAD_JOIN action
+ */
+void ModelChecker::do_complete_join(ModelAction *join)
+{
+ Thread *blocking = (Thread *)join->get_location();
+ ModelAction *act = get_last_action(blocking->get_id());
+ join->synchronize_with(act);
+}
+
void ModelChecker::check_curr_backtracking(ModelAction * curr) {
Node *currnode = curr->get_node();
Node *parnode = currnode->get_parent();
-
+
if ((!parnode->backtrack_empty() ||
!currnode->read_from_empty() ||
!currnode->future_value_empty() ||
}
}
-
bool ModelChecker::promises_expired() {
for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
Promise *promise = (*promises)[promise_index];
return false;
}
-/** @returns whether the current partial trace must be a prefix of a
+/** @return whether the current partial trace must be a prefix of a
* feasible trace. */
bool ModelChecker::isfeasibleprefix() {
return promises->size() == 0 && *lazy_sync_size == 0;
}
-/** @returns whether the current partial trace is feasible. */
+/** @return whether the current partial trace is feasible. */
bool ModelChecker::isfeasible() {
+ 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 (promises_expired())
+ DEBUG("Infeasible: promises expired\n");
+ }
return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !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;
}
*
* If so, we decide that the execution is no longer feasible.
*/
-void ModelChecker::check_recency(ModelAction *curr, bool already_added) {
+void ModelChecker::check_recency(ModelAction *curr) {
if (params.maxreads != 0) {
if (curr->get_node()->get_read_from_size() <= 1)
return;
action_list_t::reverse_iterator rit = list->rbegin();
/* Skip past curr */
- if (already_added) {
- for (; (*rit) != curr; rit++)
- ;
- /* go past curr now */
- rit++;
- }
+ for (; (*rit) != curr; rit++)
+ ;
+ /* go past curr now */
+ rit++;
- action_list_t::reverse_iterator ritcopy=rit;
+ action_list_t::reverse_iterator ritcopy = rit;
//See if we have enough reads from the same value
- int count=0;
+ int count = 0;
for (; count < params.maxreads; rit++,count++) {
if (rit==list->rend())
return;
return;
}
- for (int i=0;i<curr->get_node()->get_read_from_size();i++) {
+ 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);
+ 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*/
mo_graph->startChanges();
r_modification_order(curr, write);
- bool feasiblereadfrom=isfeasible();
+ bool feasiblereadfrom = isfeasible();
mo_graph->rollbackChanges();
if (!feasiblereadfrom)
continue;
- rit=ritcopy;
+ rit = ritcopy;
- bool feasiblewrite=true;
+ bool feasiblewrite = true;
//new we need to see if this write works for everyone
- for (int loop=count;loop>0;loop--,rit++) {
+ 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++) {
+ 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;
+ foundvalue = true;
break;
}
}
if (!foundvalue) {
- feasiblewrite=false;
+ feasiblewrite = false;
break;
}
}
}
/**
- * Updates the mo_graph with the constraints imposed from the current read.
+ * 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
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()) {
+ /*
+ * 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 (prevreadfrom != NULL && rf != prevreadfrom) {
mo_graph->addEdge(prevreadfrom, rf);
added = true;
}
- } else if (rf != act) {
- mo_graph->addEdge(act, rf);
- added = true;
}
break;
}
return added;
}
-/** Updates the mo_graph with the constraints imposed from the current read. */
+/** 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());
/**
* 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
*/
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());
+ ModelAction *last_seq_cst = get_last_seq_cst(curr);
if (last_seq_cst != NULL) {
mo_graph->addEdge(last_seq_cst, curr);
added = true;
action_list_t::reverse_iterator rit;
for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *act = *rit;
+ if (act == curr) {
+ /*
+ * If RMW, we already have all relevant edges,
+ * so just skip to next thread.
+ * If normal write, we need to look at earlier
+ * actions, so continue processing list.
+ */
+ if (curr->is_rmw())
+ break;
+ else
+ continue;
+ }
- /* Include at most one act per-thread that "happens before" curr */
+ /*
+ * Include at most one act per-thread that "happens
+ * before" curr
+ */
if (act->happens_before(curr)) {
/*
* Note: if act is RMW, just add edge:
* The following edge should be handled elsewhere:
* readfrom(act) --mo--> act
*/
- if (act->is_write()) {
- //RMW shouldn't have an edge to themselves
- if (act!=curr)
- mo_graph->addEdge(act, curr);
- } else if (act->is_read() && act->get_reads_from() != NULL)
+ 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;
=>
that read could potentially read from our write.
*/
- if (isfeasible() && act->get_node()->add_future_value(curr->get_value(), curr->get_seq_number()+params.maxfuturedelay) &&
- (!priv->next_backtrack || *act > *priv->next_backtrack))
- priv->next_backtrack = act;
+ 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->get_value(),curr->get_seq_number()+params.maxfuturedelay,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;
+}
+
/**
* Finds the head(s) of the release sequence(s) containing a given ModelAction.
* The ModelAction under consideration is expected to be taking part in
* @return true, if the ModelChecker is certain that release_heads is complete;
* false otherwise
*/
-bool ModelChecker::release_seq_head(const ModelAction *rf,
- std::vector<const ModelAction *> *release_heads) const
+bool ModelChecker::release_seq_head(const ModelAction *rf, rel_heads_list_t *release_heads) const
{
- ASSERT(rf->is_write());
if (!rf) {
/* read from future: need to settle this later */
return false; /* incomplete */
}
+
+ ASSERT(rf->is_write());
+
if (rf->is_release())
release_heads->push_back(rf);
if (rf->is_rmw()) {
* the release seq? */
bool future_ordered = false;
+ ModelAction *last = get_last_action(int_to_id(i));
+ if (last && rf->happens_before(last))
+ future_ordered = true;
+
for (rit = list->rbegin(); rit != list->rend(); rit++) {
const ModelAction *act = *rit;
- if (!act->is_write())
- continue;
/* Reach synchronization -> this thread is complete */
if (act->happens_before(release))
break;
continue;
}
+ /* Only writes can break release sequences */
+ if (!act->is_write())
+ continue;
+
/* Check modification order */
if (mo_graph->checkReachable(rf, act)) {
/* rf --mo--> act */
* with the head(s) of the release sequence(s), if they exists with certainty.
* @see ModelChecker::release_seq_head
*/
-void ModelChecker::get_release_seq_heads(ModelAction *act,
- std::vector<const ModelAction *> *release_heads)
+void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
{
const ModelAction *rf = act->get_reads_from();
bool complete;
complete = release_seq_head(rf, release_heads);
if (!complete) {
/* add act to 'lazy checking' list */
- std::list<ModelAction *> *list;
+ action_list_t *list;
list = lazy_sync_with_release->get_safe_ptr(act->get_location());
list->push_back(act);
(*lazy_sync_size)++;
*
* @param location The location/object that should be checked for release
* sequence resolutions
- * @return True if any updates occurred (new synchronization, new mo_graph edges)
+ * @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)
+bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
{
- std::list<ModelAction *> *list;
+ action_list_t *list;
list = lazy_sync_with_release->getptr(location);
if (!list)
return false;
bool updated = false;
- std::list<ModelAction *>::iterator it = list->begin();
+ action_list_t::iterator it = list->begin();
while (it != list->end()) {
ModelAction *act = *it;
const ModelAction *rf = act->get_reads_from();
- std::vector<const ModelAction *> release_heads;
+ rel_heads_list_t release_heads;
bool complete;
complete = release_seq_head(rf, &release_heads);
for (unsigned int i = 0; i < release_heads.size(); i++) {
}
if (updated) {
+ /* Re-check act for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(act));
+
/* propagate synchronization to later actions */
action_list_t::reverse_iterator it = action_trace->rbegin();
while ((*it) != act) {
ModelAction *propagate = *it;
- if (act->happens_before(propagate))
- /** @todo new mo_graph edges along with
- * this synchronization? */
+ if (act->happens_before(propagate)) {
propagate->synchronize_with(act);
+ /* Re-check 'propagate' for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(propagate));
+ }
}
}
if (complete) {
(*thrd_last_action)[tid] = act;
}
-ModelAction * ModelChecker::get_last_action(thread_id_t tid)
+/**
+ * @brief Get the last action performed by a particular Thread
+ * @param tid The thread ID of the Thread in question
+ * @return The last action in the thread
+ */
+ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
{
- 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)];
+ int threadid = id_to_int(tid);
+ if (threadid < (int)thrd_last_action->size())
+ return (*thrd_last_action)[id_to_int(tid)];
+ else
+ return NULL;
}
/**
- * 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
+ * Gets the last memory_order_seq_cst write (in the total global sequence)
+ * performed on a particular object (i.e., memory location), not including the
+ * current action.
+ * @param curr The current ModelAction; also denotes the object location to
+ * check
+ * @return The last seq_cst write
*/
-ModelAction * ModelChecker::get_last_seq_cst(const void *location)
+ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const
{
+ void *location = curr->get_location();
action_list_t *list = obj_map->get_safe_ptr(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())
+ if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
+ return *rit;
+ return NULL;
+}
+
+/**
+ * Gets the last unlock operation performed on a particular mutex (i.e., memory
+ * location). This function identifies the mutex according to the current
+ * action, which is presumed to perform on the same mutex.
+ * @param curr The current ModelAction; also denotes the object location to
+ * check
+ * @return The last unlock operation
+ */
+ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
+{
+ void *location = curr->get_location();
+ action_list_t *list = obj_map->get_safe_ptr(location);
+ /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++)
+ if ((*rit)->is_unlock())
return *rit;
return NULL;
}
bool ModelChecker::resolve_promises(ModelAction *write)
{
bool resolved = false;
+
for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
Promise *promise = (*promises)[promise_index];
if (write->get_node()->get_promise(i)) {
if (read->is_rmw()) {
mo_graph->addRMWEdge(write, read);
}
+ //First fix up the modification order for actions that happened
+ //before the read
r_modification_order(read, write);
+ //Next fix up the modification order for actions that happened
+ //after the read.
post_r_modification_order(read, write);
promises->erase(promises->begin() + promise_index);
resolved = true;
} else
promise_index++;
}
-
return resolved;
}
bool initialized = false;
if (curr->is_seqcst()) {
- last_seq_cst = get_last_seq_cst(curr->get_location());
+ last_seq_cst = get_last_seq_cst(curr);
/* We have to at least see the last sequentially consistent write,
so we are initialized. */
if (last_seq_cst != NULL)
ModelAction *act = *rit;
/* Only consider 'write' actions */
- if (!act->is_write())
+ if (!act->is_write() || act == curr)
continue;
/* Don't consider more than one seq_cst write if we are a seq_cst read. */
{
printf("\n");
printf("Number of executions: %d\n", num_executions);
+ printf("Number of feasible executions: %d\n", num_feasible_executions);
printf("Total nodes created: %d\n", node_stack->get_total_nodes());
+#if SUPPORT_MOD_ORDER_DUMP
scheduler->print();
+ char buffername[100];
+ sprintf(buffername, "exec%04u", num_executions);
+ mo_graph->dumpGraphToFile(buffername);
+#endif
if (!isfinalfeasible())
printf("INFEASIBLE EXECUTION!\n");
* @return Returns true (success) if a step was taken and false otherwise.
*/
bool ModelChecker::take_step() {
- Thread *curr, *next;
-
if (has_asserted())
return false;
- curr = thread_current();
+ Thread * curr = thread_current();
if (curr) {
if (curr->get_state() == THREAD_READY) {
ASSERT(priv->current_action);
+
priv->nextThread = check_current_action(priv->current_action);
priv->current_action = NULL;
- if (!curr->is_blocked() && !curr->is_complete())
- scheduler->add_thread(curr);
+ if (curr->is_blocked() || curr->is_complete())
+ scheduler->remove_thread(curr);
} else {
ASSERT(false);
}
}
- next = scheduler->next_thread(priv->nextThread);
+ Thread * next = scheduler->next_thread(priv->nextThread);
/* Infeasible -> don't take any more steps */
if (!isfeasible())
/* next == NULL -> don't take any more steps */
if (!next)
return false;
+
+ if ( next->get_pending() != NULL ) {
+ //restart a pending action
+ set_current_action(next->get_pending());
+ next->set_pending(NULL);
+ next->set_state(THREAD_READY);
+ return true;
+ }
+
/* Return false only if swap fails with an error */
return (Thread::swap(&system_context, next) == 0);
}
projects / c11tester.git / blobdiff