#include <stdio.h>
+#include <algorithm>
+#include <mutex>
#include "model.h"
#include "action.h"
#include "clockvector.h"
#include "cyclegraph.h"
#include "promise.h"
+#include "datarace.h"
+#include "threads-model.h"
#define INITIAL_THREAD_ID 0
/** @brief Constructor */
ModelChecker::ModelChecker(struct model_params params) :
/* Initialize default scheduler */
+ params(params),
scheduler(new Scheduler()),
- /* First thread created will have id INITIAL_THREAD_ID */
- next_thread_id(INITIAL_THREAD_ID),
- used_sequence_numbers(0),
num_executions(0),
- params(params),
- current_action(NULL),
+ num_feasible_executions(0),
diverge(NULL),
- nextThread(THREAD_ID_T_NONE),
+ earliest_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>()),
+ condvar_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 *>()),
- thrd_last_action(new std::vector<ModelAction *>(1)),
+ promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
+ futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
+ pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
+ thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
node_stack(new NodeStack()),
- next_backtrack(NULL),
- cyclegraph(new CycleGraph()),
- failed_promise(false)
+ mo_graph(new CycleGraph()),
+ failed_promise(false),
+ too_many_reads(false),
+ asserted(false),
+ bad_synchronization(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;
+
+ /* Initialize a model-checker thread, for special ModelActions */
+ model_thread = new Thread(get_next_id());
+ thread_map->put(id_to_int(model_thread->get_id()), model_thread);
}
/** @brief Destructor */
ModelChecker::~ModelChecker()
{
- for (int i = 0; i < get_num_threads(); i++)
+ for (unsigned int i = 0; i < get_num_threads(); i++)
delete thread_map->get(i);
delete thread_map;
delete obj_thrd_map;
delete obj_map;
+ delete lock_waiters_map;
+ delete condvar_waiters_map;
delete action_trace;
+
+ for (unsigned int i = 0; i < promises->size(); i++)
+ delete (*promises)[i];
+ delete promises;
+
+ delete pending_rel_seqs;
+
delete thrd_last_action;
delete node_stack;
delete scheduler;
- delete cyclegraph;
+ delete mo_graph;
}
/**
{
DEBUG("+++ Resetting to initial state +++\n");
node_stack->reset_execution();
- current_action = NULL;
- next_thread_id = INITIAL_THREAD_ID;
- used_sequence_numbers = 0;
- nextThread = 0;
- next_backtrack = NULL;
failed_promise = false;
+ too_many_reads = false;
+ bad_synchronization = false;
+ reset_asserted();
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 next_thread_id++;
+ return priv->next_thread_id++;
}
-/** @returns the number of user threads created during this execution */
-int ModelChecker::get_num_threads()
+/** @return the number of user threads created during this execution */
+unsigned int ModelChecker::get_num_threads()
{
- return next_thread_id;
+ return priv->next_thread_id;
}
-/** @returns a sequence number for a new ModelAction */
-modelclock_t ModelChecker::get_next_seq_num()
+/** @return The currently executing Thread. */
+Thread * ModelChecker::get_current_thread()
{
- return ++used_sequence_numbers;
+ return scheduler->get_current_thread();
}
-/**
- * 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()
+/** @return a sequence number for a new ModelAction */
+modelclock_t ModelChecker::get_next_seq_num()
{
- Thread *t;
- if (nextThread == THREAD_ID_T_NONE)
- return NULL;
- t = thread_map->get(id_to_int(nextThread));
-
- ASSERT(t != NULL);
+ return ++priv->used_sequence_numbers;
+}
- return t;
+Node * ModelChecker::get_curr_node() {
+ return node_stack->get_head();
}
/**
- * 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_id_t ModelChecker::get_next_replay_thread()
+Thread * ModelChecker::get_next_thread(ModelAction *curr)
{
thread_id_t tid;
+ 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)
- return THREAD_ID_T_NONE;
+ return NULL;
/* Else, we are trying to replay an execution */
- ModelAction * next = node_stack->get_next()->get_action();
+ ModelAction *next = node_stack->get_next()->get_action();
if (next == diverge) {
+ if (earliest_diverge == NULL || *diverge < *earliest_diverge)
+ earliest_diverge=diverge;
+
Node *nextnode = next->get_node();
+ Node *prevnode = nextnode->get_parent();
+ scheduler->update_sleep_set(prevnode);
+
/* Reached divergence point */
- if (nextnode->increment_promise()) {
+ if (nextnode->increment_misc()) {
+ /* The next node will try to satisfy a different misc_index values. */
+ tid = next->get_tid();
+ node_stack->pop_restofstack(2);
+ } else if (nextnode->increment_promise()) {
/* The next node will try to satisfy a different set of promises. */
tid = next->get_tid();
node_stack->pop_restofstack(2);
/* The next node will try to read from a different future value. */
tid = next->get_tid();
node_stack->pop_restofstack(2);
+ } else if (nextnode->increment_relseq_break()) {
+ /* The next node will try to resolve a release sequence differently */
+ 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();
+ scheduler->add_sleep(thread_map->get(id_to_int(next->get_tid())));
+ tid = prevnode->get_next_backtrack();
+ /* Make sure the backtracked thread isn't sleeping. */
node_stack->pop_restofstack(1);
+ if (diverge==earliest_diverge) {
+ earliest_diverge=prevnode->get_action();
+ }
}
+ /* The correct sleep set is in the parent node. */
+ execute_sleep_set();
+
DEBUG("*** Divergence point ***\n");
+
diverge = NULL;
} else {
tid = next->get_tid();
}
- DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
- return tid;
+ DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
+ ASSERT(tid != THREAD_ID_T_NONE);
+ return thread_map->get(id_to_int(tid));
+}
+
+/**
+ * We need to know what the next actions of all threads in the sleep
+ * set will be. This method computes them and stores the actions at
+ * the corresponding thread object's pending action.
+ */
+
+void ModelChecker::execute_sleep_set() {
+ for(unsigned int i=0;i<get_num_threads();i++) {
+ thread_id_t tid=int_to_id(i);
+ Thread *thr=get_thread(tid);
+ if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
+ thr->set_state(THREAD_RUNNING);
+ scheduler->next_thread(thr);
+ Thread::swap(&system_context, thr);
+ priv->current_action->set_sleep_flag();
+ thr->set_pending(priv->current_action);
+ }
+ }
+ priv->current_action = NULL;
+}
+
+void ModelChecker::wake_up_sleeping_actions(ModelAction * curr) {
+ for(unsigned int i=0;i<get_num_threads();i++) {
+ thread_id_t tid=int_to_id(i);
+ Thread *thr=get_thread(tid);
+ if ( scheduler->get_enabled(thr) == THREAD_SLEEP_SET ) {
+ ModelAction *pending_act=thr->get_pending();
+ if (pending_act->could_synchronize_with(curr)) {
+ //Remove this thread from sleep set
+ scheduler->remove_sleep(thr);
+ }
+ }
+ }
}
/**
num_executions++;
- if (isfinalfeasible() || DBG_ENABLED())
+ if (isfinalfeasible()) {
+ printf("Earliest divergence point since last feasible execution:\n");
+ if (earliest_diverge)
+ earliest_diverge->print();
+ else
+ printf("(Not set)\n");
+
+ earliest_diverge = NULL;
+ num_feasible_executions++;
+ }
+
+ DEBUG("Number of acquires waiting on pending release sequences: %zu\n",
+ pending_rel_seqs->size());
+
+
+ if (isfinalfeasible() || (params.bound != 0 && priv->used_sequence_numbers > params.bound ) || DBG_ENABLED() )
print_summary();
- if ((diverge = model->get_next_backtrack()) == NULL)
+ if ((diverge = get_next_backtrack()) == NULL)
return false;
if (DBG_ENABLED()) {
diverge->print();
}
- model->reset_to_initial_state();
+ reset_to_initial_state();
return true;
}
ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
{
- action_type type = act->get_type();
+ 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 (prev->could_synchronize_with(act))
+ return prev;
+ }
+ break;
+ }
+ 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;
+ }
+ case ATOMIC_WAIT: {
+ /* 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;
+ if (!act->same_thread(prev)&&prev->is_notify())
+ return prev;
+ }
+ break;
+ }
- switch (type) {
- case ATOMIC_READ:
- case ATOMIC_WRITE:
- case ATOMIC_RMW:
- break;
- default:
- return NULL;
+ case ATOMIC_NOTIFY_ALL:
+ case ATOMIC_NOTIFY_ONE: {
+ /* 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_wait())
+ return prev;
+ }
+ break;
}
- /* linear search: from most recent to oldest */
- action_list_t *list = obj_map->ensureptr(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;
+ default:
+ break;
}
return NULL;
}
+/** This method finds backtracking points where we should try to
+ * reorder the parameter ModelAction against.
+ *
+ * @param the ModelAction to find backtracking points for.
+ */
void ModelChecker::set_backtracking(ModelAction *act)
{
- ModelAction *prev;
- Node *node;
- Thread *t = get_thread(act->get_tid());
-
- prev = get_last_conflict(act);
+ Thread *t = get_thread(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();
+ Node * node = prev->get_node()->get_parent();
- /* Check if this has been explored already */
- if (node->has_been_explored(t->get_id()))
- return;
-
- /* Cache the latest backtracking point */
- if (!next_backtrack || *prev > *next_backtrack)
- 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();
+ }
- /* 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();
+ for(int i = low_tid; i < high_tid; i++) {
+ thread_id_t tid = int_to_id(i);
+
+ /* Don't backtrack into a point where the thread is disabled or sleeping. */
+ if (node->get_enabled_array()[i]!=THREAD_ENABLED)
+ continue;
+
+ /* Check if this has been explored already */
+ if (node->has_been_explored(tid))
+ continue;
+
+ /* See if fairness allows */
+ if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
+ bool unfair=false;
+ for(int t=0;t<node->get_num_threads();t++) {
+ thread_id_t tother=int_to_id(t);
+ if (node->is_enabled(tother) && node->has_priority(tother)) {
+ unfair=true;
+ break;
+ }
+ }
+ if (unfair)
+ 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",
+ id_to_int(prev->get_tid()),
+ id_to_int(t->get_id()));
+ if (DBG_ENABLED()) {
+ prev->print();
+ act->print();
+ }
}
}
*/
ModelAction * ModelChecker::get_next_backtrack()
{
- ModelAction *next = next_backtrack;
- next_backtrack = NULL;
+ ModelAction *next = priv->next_backtrack;
+ priv->next_backtrack = NULL;
return next;
}
-void ModelChecker::check_current_action(void)
+/**
+ * Processes a read or rmw model action.
+ * @param curr is the read model action to process.
+ * @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, bool second_part_of_rmw)
{
- ModelAction *curr = this->current_action;
- bool already_added = false;
- this->current_action = NULL;
- if (!curr) {
- DEBUG("trying to push NULL action...\n");
- return;
+ uint64_t value;
+ 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();
+ bool r_status = false;
+
+ if (!second_part_of_rmw) {
+ check_recency(curr, reads_from);
+ r_status = r_modification_order(curr, reads_from);
+ }
+
+
+ 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;
+ continue;
+ }
+
+ curr->read_from(reads_from);
+ mo_graph->commitChanges();
+ mo_check_promises(curr->get_tid(), reads_from);
+
+ updated |= r_status;
+ } 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();
+ curr->read_from(NULL);
+ Promise *valuepromise = new Promise(curr, value, expiration);
+ promises->push_back(valuepromise);
+ }
+ get_thread(curr)->set_return_value(value);
+ return updated;
}
+}
- if (curr->is_rmwc() || curr->is_rmw()) {
- ModelAction *tmp = process_rmw(curr);
- already_added = true;
- delete curr;
- curr = tmp;
- } 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);
+/**
+ * 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.
+ *
+ * @return True if synchronization was updated; false otherwise
+ */
+bool ModelChecker::process_mutex(ModelAction *curr) {
+ std::mutex *mutex=NULL;
+ struct std::mutex_state *state=NULL;
+
+ if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
+ mutex = (std::mutex *)curr->get_location();
+ state = mutex->get_state();
+ } else if(curr->is_wait()) {
+ mutex = (std::mutex *)curr->get_value();
+ 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);
+ return true;
+ }
+ 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->wake(get_thread(*rit));
}
+ waiters->clear();
+ break;
}
+ case ATOMIC_WAIT: {
+ //unlock the lock
+ state->islocked = false;
+ //wake up the other threads
+ action_list_t *waiters = lock_waiters_map->get_safe_ptr((void *) curr->get_value());
+ //activate all the waiting threads
+ for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
+ scheduler->wake(get_thread(*rit));
+ }
+ waiters->clear();
+ //check whether we should go to sleep or not...simulate spurious failures
+ if (curr->get_node()->get_misc()==0) {
+ condvar_waiters_map->get_safe_ptr(curr->get_location())->push_back(curr);
+ //disable us
+ scheduler->sleep(get_current_thread());
+ }
+ break;
+ }
+ case ATOMIC_NOTIFY_ALL: {
+ action_list_t *waiters = condvar_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->wake(get_thread(*rit));
+ }
+ waiters->clear();
+ break;
+ }
+ case ATOMIC_NOTIFY_ONE: {
+ action_list_t *waiters = condvar_waiters_map->get_safe_ptr(curr->get_location());
+ int wakeupthread=curr->get_node()->get_misc();
+ action_list_t::iterator it = waiters->begin();
+ advance(it, wakeupthread);
+ scheduler->wake(get_thread(*it));
+ waiters->erase(it);
+ break;
+ }
+
+ default:
+ ASSERT(0);
+ }
+ return false;
+}
+
+/**
+ * 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];
+ //Do more ambitious checks now that mo is more complete
+ if (mo_may_allow(pfv.writer, pfv.act)&&
+ pfv.act->get_node()->add_future_value(pfv.writer->get_value(), pfv.writer->get_seq_number()+params.maxfuturedelay) &&
+ (!priv->next_backtrack || *pfv.act > *priv->next_backtrack))
+ priv->next_backtrack = pfv.act;
+ }
+ futurevalues->resize(0);
+ }
+
+ mo_graph->commitChanges();
+ mo_check_promises(curr->get_tid(), curr);
- /* Assign 'creation' parent */
- if (curr->get_type() == THREAD_CREATE) {
+ get_thread(curr)->set_return_value(VALUE_NONE);
+ return updated_mod_order || updated_promises;
+}
+
+/**
+ * @brief Process the current action for thread-related activity
+ *
+ * Performs current-action processing for a THREAD_* ModelAction. Proccesses
+ * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
+ * synchronization, etc. This function is a no-op for non-THREAD actions
+ * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
+ *
+ * @param curr The current action
+ * @return True if synchronization was updated or a thread completed
+ */
+bool ModelChecker::process_thread_action(ModelAction *curr)
+{
+ bool updated = false;
+
+ switch (curr->get_type()) {
+ case THREAD_CREATE: {
Thread *th = (Thread *)curr->get_location();
th->set_creation(curr);
+ break;
+ }
+ case THREAD_JOIN: {
+ Thread *blocking = (Thread *)curr->get_location();
+ ModelAction *act = get_last_action(blocking->get_id());
+ curr->synchronize_with(act);
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_FINISH: {
+ Thread *th = get_thread(curr);
+ while (!th->wait_list_empty()) {
+ ModelAction *act = th->pop_wait_list();
+ scheduler->wake(get_thread(act));
+ }
+ th->complete();
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_START: {
+ check_promises(curr->get_tid(), NULL, curr->get_cv());
+ break;
+ }
+ default:
+ break;
}
- /* Deal with new thread */
- if (curr->get_type() == THREAD_START)
- check_promises(NULL, curr->get_cv());
+ return updated;
+}
- /* Assign reads_from values */
- 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();
- if (reads_from != NULL) {
- value = reads_from->get_value();
- /* Assign reads_from, perform release/acquire synchronization */
- curr->read_from(reads_from);
- r_modification_order(curr,reads_from);
- } 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);
+/**
+ * @brief Process the current action for release sequence fixup activity
+ *
+ * Performs model-checker release sequence fixups for the current action,
+ * forcing a single pending release sequence to break (with a given, potential
+ * "loose" write) or to complete (i.e., synchronize). If a pending release
+ * sequence forms a complete release sequence, then we must perform the fixup
+ * synchronization, mo_graph additions, etc.
+ *
+ * @param curr The current action; must be a release sequence fixup action
+ * @param work_queue The work queue to which to add work items as they are
+ * generated
+ */
+void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
+{
+ const ModelAction *write = curr->get_node()->get_relseq_break();
+ struct release_seq *sequence = pending_rel_seqs->back();
+ pending_rel_seqs->pop_back();
+ ASSERT(sequence);
+ ModelAction *acquire = sequence->acquire;
+ const ModelAction *rf = sequence->rf;
+ const ModelAction *release = sequence->release;
+ ASSERT(acquire);
+ ASSERT(release);
+ ASSERT(rf);
+ ASSERT(release->same_thread(rf));
+
+ if (write == NULL) {
+ /**
+ * @todo Forcing a synchronization requires that we set
+ * modification order constraints. For instance, we can't allow
+ * a fixup sequence in which two separate read-acquire
+ * operations read from the same sequence, where the first one
+ * synchronizes and the other doesn't. Essentially, we can't
+ * allow any writes to insert themselves between 'release' and
+ * 'rf'
+ */
+
+ /* Must synchronize */
+ if (!acquire->synchronize_with(release)) {
+ set_bad_synchronization();
+ return;
+ }
+ /* Re-check all pending release sequences */
+ work_queue->push_back(CheckRelSeqWorkEntry(NULL));
+ /* Re-check act for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(acquire));
+
+ /* propagate synchronization to later actions */
+ action_list_t::reverse_iterator rit = action_trace->rbegin();
+ for (; (*rit) != acquire; rit++) {
+ ModelAction *propagate = *rit;
+ if (acquire->happens_before(propagate)) {
+ propagate->synchronize_with(acquire);
+ /* Re-check 'propagate' for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(propagate));
+ }
}
- } else if (curr->is_write()) {
- w_modification_order(curr);
- resolve_promises(curr);
+ } else {
+ /* Break release sequence with new edges:
+ * release --mo--> write --mo--> rf */
+ mo_graph->addEdge(release, write);
+ mo_graph->addEdge(write, rf);
}
- th->set_return_value(value);
+ /* See if we have realized a data race */
+ if (checkDataRaces())
+ set_assert();
+}
- /* Add action to list. */
- if (!already_added)
- add_action_to_lists(curr);
+/**
+ * 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;
- /** @todo Is there a better interface for setting the next thread rather
- than this field/convoluted approach? Perhaps like just returning
- it or something? */
+ if (curr->is_rmwc() || curr->is_rmw()) {
+ newcurr = process_rmw(curr);
+ delete curr;
- /* Do not split atomic actions. */
- if (curr->is_rmwr())
- nextThread = thread_current()->get_id();
- else
- nextThread = get_next_replay_thread();
+ if (newcurr->is_rmw())
+ compute_promises(newcurr);
+ return newcurr;
+ }
+
+ curr->set_seq_number(get_next_seq_num());
+
+ 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;
+ /* Always compute new clock vector */
+ newcurr->create_cv(get_parent_action(newcurr->get_tid()));
+ } else {
+ newcurr = curr;
+
+ /* Always compute new clock vector */
+ newcurr->create_cv(get_parent_action(newcurr->get_tid()));
+ /*
+ * Perform one-time actions when pushing new ModelAction onto
+ * NodeStack
+ */
+ if (newcurr->is_write())
+ compute_promises(newcurr);
+ else if (newcurr->is_relseq_fixup())
+ compute_relseq_breakwrites(newcurr);
+ else if (newcurr->is_wait())
+ newcurr->get_node()->set_misc_max(2);
+ else if (newcurr->is_notify_one()) {
+ newcurr->get_node()->set_misc_max(condvar_waiters_map->get_safe_ptr(newcurr->get_location())->size());
+ }
+ }
+ return newcurr;
+}
+
+/**
+ * @brief Check whether a model action is enabled.
+ *
+ * Checks whether a lock or join operation would be successful (i.e., is the
+ * lock already locked, or is the joined thread already complete). If not, put
+ * the action 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;
+ }
+ } else if (curr->get_type() == THREAD_JOIN) {
+ Thread *blocking = (Thread *)curr->get_location();
+ if (!blocking->is_complete()) {
+ blocking->push_wait_list(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
+ * calculates reads-from relationships, updates synchronization clock vectors,
+ * forms a memory_order constraints graph, and handles replay/backtrack
+ * execution when running permutations of previously-observed executions.
+ *
+ * @param curr The current action to process
+ * @return The next Thread that must be executed. May be NULL if ModelChecker
+ * makes no choice (e.g., according to replay execution, combining RMW actions,
+ * etc.)
+ */
+Thread * ModelChecker::check_current_action(ModelAction *curr)
+{
+ ASSERT(curr);
+ bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
+
+ if (!check_action_enabled(curr)) {
+ /* Make the execution look like we chose to run this action
+ * much later, when a lock/join can succeed */
+ get_current_thread()->set_pending(curr);
+ scheduler->sleep(get_current_thread());
+ return get_next_thread(NULL);
+ }
+
+ ModelAction *newcurr = initialize_curr_action(curr);
+
+ wake_up_sleeping_actions(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;
+
+ /* Initialize work_queue with the "current action" work */
+ work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
+ while (!work_queue.empty()) {
+ WorkQueueEntry work = work_queue.front();
+ work_queue.pop_front();
+
+ switch (work.type) {
+ case WORK_CHECK_CURR_ACTION: {
+ ModelAction *act = work.action;
+ bool update = false; /* update this location's release seq's */
+ bool update_all = false; /* update all release seq's */
+
+ if (process_thread_action(curr))
+ update_all = true;
+
+ if (act->is_read() && process_read(act, second_part_of_rmw))
+ update = true;
+
+ if (act->is_write() && process_write(act))
+ update = true;
+
+ if (act->is_mutex_op() && process_mutex(act))
+ update_all = true;
+
+ if (act->is_relseq_fixup())
+ process_relseq_fixup(curr, &work_queue);
+
+ if (update_all)
+ work_queue.push_back(CheckRelSeqWorkEntry(NULL));
+ else if (update)
+ 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()) {
+ const ModelAction *rf = act->get_reads_from();
+ if (rf != NULL && r_modification_order(act, rf))
+ updated = true;
+ }
+ if (act->is_write()) {
+ if (w_modification_order(act))
+ updated = true;
+ }
+ mo_graph->commitChanges();
+
+ 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);
+}
+
+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() || !currnode->promise_empty())
- if (!next_backtrack || *curr > *next_backtrack)
- next_backtrack = curr;
+ if ((!parnode->backtrack_empty() ||
+ !currnode->misc_empty() ||
+ !currnode->read_from_empty() ||
+ !currnode->future_value_empty() ||
+ !currnode->promise_empty() ||
+ !currnode->relseq_break_empty())
+ && (!priv->next_backtrack ||
+ *curr > *priv->next_backtrack)) {
+ priv->next_backtrack = curr;
+ }
+}
- set_backtracking(curr);
+bool ModelChecker::promises_expired() {
+ for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) {
+ Promise *promise = (*promises)[promise_index];
+ if (promise->get_expiration()<priv->used_sequence_numbers) {
+ return true;
+ }
+ }
+ return false;
+}
+
+/** @return whether the current partial trace must be a prefix of a
+ * feasible trace. */
+bool ModelChecker::isfeasibleprefix() {
+ return promises->size() == 0 && pending_rel_seqs->size() == 0;
}
-/** @returns whether the current partial trace is feasible. */
+/** @return whether the current partial trace is feasible. */
bool ModelChecker::isfeasible() {
- return !cyclegraph->checkForCycles() && !failed_promise;
+ if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
+ DEBUG("Infeasible: RMW violation\n");
+
+ 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 (bad_synchronization)
+ DEBUG("Infeasible: bad synchronization ordering\n");
+ if (promises_expired())
+ DEBUG("Infeasible: promises expired\n");
+ }
+ return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !bad_synchronization && !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;
}
/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
-ModelAction * ModelChecker::process_rmw(ModelAction * act) {
- int tid = id_to_int(act->get_tid());
- ModelAction *lastread = get_last_action(tid);
+ModelAction * ModelChecker::process_rmw(ModelAction *act) {
+ ModelAction *lastread = get_last_action(act->get_tid());
lastread->process_rmw(act);
- if (act->is_rmw())
- cyclegraph->addRMWEdge(lastread, lastread->get_reads_from());
+ if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
+ mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
+ mo_graph->commitChanges();
+ }
return lastread;
}
/**
- * Updates the cyclegraph with the constraints imposed from the current read.
+ * 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, const ModelAction *rf) {
+ 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 */
+ 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() != rf)
+ 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==rf)
+ continue;
+
+ /* Test to see whether this is a feasible write to read from*/
+ mo_graph->startChanges();
+ 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.
+ *
+ * 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
*/
-void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *rf) {
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
+bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
+{
+ std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
unsigned int i;
+ bool added = false;
ASSERT(curr->is_read());
/* Iterate over all threads */
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 (prevreadfrom != NULL && rf != prevreadfrom)
- cyclegraph->addEdge(rf, prevreadfrom);
- } else if (rf != act) {
- cyclegraph->addEdge(rf, act);
+ /*
+ * 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 the previous read is unresolved, keep going...
+ if (prevreadfrom == NULL)
+ continue;
+
+ if (rf != prevreadfrom) {
+ mo_graph->addEdge(prevreadfrom, rf);
+ added = true;
+ }
}
break;
}
}
}
+
+ return added;
}
-/** Updates the cyclegraph with the constraints imposed from the
- * current read. */
-void ModelChecker::post_r_modification_order(ModelAction * curr, const ModelAction *rf) {
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
+/** 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());
unsigned int i;
ASSERT(curr->is_read());
action_list_t::reverse_iterator rit;
ModelAction *lastact = NULL;
- /* Find last action that happens after curr */
+ /* Find last action that happens after curr that is either not curr or a rmw */
for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *act = *rit;
- if (curr->happens_before(act)) {
+ if (curr->happens_before(act) && (curr != act || curr->is_rmw())) {
lastact = act;
} else
break;
/* Include at most one act per-thread that "happens before" curr */
if (lastact != NULL) {
- if (lastact->is_read()) {
- const ModelAction * postreadfrom = lastact->get_reads_from();
+ if (lastact==curr) {
+ //Case 1: The resolved read is a RMW, and we need to make sure
+ //that the write portion of the RMW mod order after rf
+
+ mo_graph->addEdge(rf, lastact);
+ } else if (lastact->is_read()) {
+ //Case 2: The resolved read is a normal read and the next
+ //operation is a read, and we need to make sure the value read
+ //is mod ordered after rf
+
+ const ModelAction *postreadfrom = lastact->get_reads_from();
if (postreadfrom != NULL&&rf != postreadfrom)
- cyclegraph->addEdge(postreadfrom, rf);
- } else if (rf != lastact) {
- cyclegraph->addEdge(lastact, rf);
+ mo_graph->addEdge(rf, postreadfrom);
+ } else {
+ //Case 3: The resolved read is a normal read and the next
+ //operation is a write, and we need to make sure that the
+ //write is mod ordered after rf
+ if (lastact!=rf)
+ mo_graph->addEdge(rf, lastact);
}
break;
}
}
/**
- * Updates the cyclegraph with the constraints imposed from the current write.
+ * 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
*/
-void ModelChecker::w_modification_order(ModelAction * curr) {
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
+bool ModelChecker::w_modification_order(ModelAction *curr)
+{
+ std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
unsigned int i;
+ bool added = false;
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);
+ ModelAction *last_seq_cst = get_last_seq_cst(curr);
+ if (last_seq_cst != NULL) {
+ mo_graph->addEdge(last_seq_cst, curr);
+ added = true;
+ }
}
/* Iterate over all threads */
action_list_t::reverse_iterator rit;
for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *act = *rit;
+ if (act == curr) {
+ /*
+ * 1) If RMW and it actually read from something, then we
+ * already have all relevant edges, so just skip to next
+ * thread.
+ *
+ * 2) If RMW and it didn't read from anything, we should
+ * whatever edge we can get to speed up convergence.
+ *
+ * 3) If normal write, we need to look at earlier actions, so
+ * continue processing list.
+ */
+ if (curr->is_rmw()) {
+ if (curr->get_reads_from()!=NULL)
+ break;
+ else
+ continue;
+ } 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)) {
- if (act->is_read())
- cyclegraph->addEdge(curr, act->get_reads_from());
- else
- cyclegraph->addEdge(curr, act);
+ /*
+ * 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()) {
+ //if previous read accessed a null, just keep going
+ if (act->get_reads_from() == NULL)
+ continue;
+ mo_graph->addEdge(act->get_reads_from(), curr);
+ }
+ added = true;
break;
- } else if (act->is_read() && !act->is_synchronizing(curr) &&
+ } else if (act->is_read() && !act->could_synchronize_with(curr) &&
!act->same_thread(curr)) {
/* We have an action that:
(1) did not happen before us
(3) cannot synchronize with us
(4) is in a different thread
=>
- that read could potentially read from our write.
+ that read could potentially read from our write. Note that
+ these checks are overly conservative at this point, we'll
+ do more checks before actually removing the
+ pendingfuturevalue.
+
*/
- if (act->get_node()->add_future_value(curr->get_value()) &&
- (!next_backtrack || *act > *next_backtrack))
- 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,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;
+}
+
+/** 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::mo_may_allow(const ModelAction * writer, const ModelAction *reader) {
+ std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(reader->get_location());
+
+ //Get write that follows reader action
+ action_list_t *list = &(*thrd_lists)[id_to_int(reader->get_tid())];
+ action_list_t::reverse_iterator rit;
+ ModelAction *first_write_after_read=NULL;
+
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+ if (act==reader)
+ break;
+ if (act->is_write())
+ first_write_after_read=act;
+ }
+
+ if (first_write_after_read==NULL)
+ return true;
+
+ return !mo_graph->checkReachable(first_write_after_read, writer);
+}
+
+
+
+/**
+ * Finds the head(s) of the release sequence(s) containing a given ModelAction.
+ * The ModelAction under consideration is expected to be taking part in
+ * release/acquire synchronization as an object of the "reads from" relation.
+ * Note that this can only provide release sequence support for RMW chains
+ * which do not read from the future, as those actions cannot be traced until
+ * their "promise" is fulfilled. Similarly, we may not even establish the
+ * presence of a release sequence with certainty, as some modification order
+ * constraints may be decided further in the future. Thus, this function
+ * "returns" two pieces of data: a pass-by-reference vector of @a release_heads
+ * and a boolean representing certainty.
+ *
+ * @param rf The action that might be part of a release sequence. Must be a
+ * write.
+ * @param release_heads A pass-by-reference style return parameter. After
+ * execution of this function, release_heads will contain the heads of all the
+ * relevant release sequences, if any exists with certainty
+ * @param pending A pass-by-reference style return parameter which is only used
+ * when returning false (i.e., uncertain). Returns most information regarding
+ * an uncertain release sequence, including any write operations that might
+ * break the sequence.
+ * @return true, if the ModelChecker is certain that release_heads is complete;
+ * false otherwise
+ */
+bool ModelChecker::release_seq_heads(const ModelAction *rf,
+ rel_heads_list_t *release_heads,
+ struct release_seq *pending) const
+{
+ /* Only check for release sequences if there are no cycles */
+ if (mo_graph->checkForCycles())
+ return false;
+
+ while (rf) {
+ ASSERT(rf->is_write());
+
+ if (rf->is_release())
+ release_heads->push_back(rf);
+ if (!rf->is_rmw())
+ break; /* End of RMW chain */
+
+ /** @todo Need to be smarter here... In the linux lock
+ * example, this will run to the beginning of the program for
+ * every acquire. */
+ /** @todo The way to be smarter here is to keep going until 1
+ * thread has a release preceded by an acquire and you've seen
+ * both. */
+
+ /* acq_rel RMW is a sufficient stopping condition */
+ if (rf->is_acquire() && rf->is_release())
+ return true; /* complete */
+
+ rf = rf->get_reads_from();
+ };
+ if (!rf) {
+ /* read from future: need to settle this later */
+ pending->rf = NULL;
+ return false; /* incomplete */
+ }
+
+ if (rf->is_release())
+ return true; /* complete */
+
+ /* else relaxed write; check modification order for contiguous subsequence
+ * -> rf must be same thread as release */
+ int tid = id_to_int(rf->get_tid());
+ std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
+ action_list_t *list = &(*thrd_lists)[tid];
+ action_list_t::const_reverse_iterator rit;
+
+ /* Find rf in the thread list */
+ rit = std::find(list->rbegin(), list->rend(), rf);
+ ASSERT(rit != list->rend());
+
+ /* Find the last write/release */
+ for (; rit != list->rend(); rit++)
+ if ((*rit)->is_release())
+ break;
+ if (rit == list->rend()) {
+ /* No write-release in this thread */
+ return true; /* complete */
+ }
+ ModelAction *release = *rit;
+
+ ASSERT(rf->same_thread(release));
+
+ pending->writes.clear();
+
+ bool certain = true;
+ for (unsigned int i = 0; i < thrd_lists->size(); i++) {
+ if (id_to_int(rf->get_tid()) == (int)i)
+ continue;
+ list = &(*thrd_lists)[i];
+
+ /* Can we ensure no future writes from this thread may break
+ * the release seq? */
+ bool future_ordered = false;
+
+ ModelAction *last = get_last_action(int_to_id(i));
+ Thread *th = get_thread(int_to_id(i));
+ if ((last && rf->happens_before(last)) ||
+ !scheduler->is_enabled(th) ||
+ th->is_complete())
+ future_ordered = true;
+
+ ASSERT(!th->is_model_thread() || future_ordered);
+
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ const ModelAction *act = *rit;
+ /* Reach synchronization -> this thread is complete */
+ if (act->happens_before(release))
+ break;
+ if (rf->happens_before(act)) {
+ future_ordered = true;
+ continue;
+ }
+
+ /* Only non-RMW writes can break release sequences */
+ if (!act->is_write() || act->is_rmw())
+ continue;
+
+ /* Check modification order */
+ if (mo_graph->checkReachable(rf, act)) {
+ /* rf --mo--> act */
+ future_ordered = true;
+ continue;
+ }
+ if (mo_graph->checkReachable(act, release))
+ /* act --mo--> release */
+ break;
+ if (mo_graph->checkReachable(release, act) &&
+ mo_graph->checkReachable(act, rf)) {
+ /* release --mo-> act --mo--> rf */
+ return true; /* complete */
+ }
+ /* act may break release sequence */
+ pending->writes.push_back(act);
+ certain = false;
+ }
+ if (!future_ordered)
+ certain = false; /* This thread is uncertain */
+ }
+
+ if (certain) {
+ release_heads->push_back(release);
+ pending->writes.clear();
+ } else {
+ pending->release = release;
+ pending->rf = rf;
+ }
+ return certain;
+}
+
+/**
+ * A public interface for getting the release sequence head(s) with which a
+ * given ModelAction must synchronize. This function only returns a non-empty
+ * result when it can locate a release sequence head with certainty. Otherwise,
+ * it may mark the internal state of the ModelChecker so that it will handle
+ * the release sequence at a later time, causing @a act to update its
+ * synchronization at some later point in execution.
+ * @param act The 'acquire' action that may read from a release sequence
+ * @param release_heads A pass-by-reference return parameter. Will be filled
+ * with the head(s) of the release sequence(s), if they exists with certainty.
+ * @see ModelChecker::release_seq_heads
+ */
+void ModelChecker::get_release_seq_heads(ModelAction *act, rel_heads_list_t *release_heads)
+{
+ const ModelAction *rf = act->get_reads_from();
+ struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
+ sequence->acquire = act;
+
+ if (!release_seq_heads(rf, release_heads, sequence)) {
+ /* add act to 'lazy checking' list */
+ pending_rel_seqs->push_back(sequence);
+ } else {
+ snapshot_free(sequence);
+ }
+}
+
+/**
+ * Attempt to resolve all stashed operations that might synchronize with a
+ * release sequence for a given location. This implements the "lazy" portion of
+ * determining whether or not a release sequence was contiguous, since not all
+ * modification order information is present at the time an action occurs.
+ *
+ * @param location The location/object that should be checked for release
+ * sequence resolutions. A NULL value means to check all locations.
+ * @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, work_queue_t *work_queue)
+{
+ bool updated = false;
+ std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
+ while (it != pending_rel_seqs->end()) {
+ struct release_seq *pending = *it;
+ ModelAction *act = pending->acquire;
+
+ /* Only resolve sequences on the given location, if provided */
+ if (location && act->get_location() != location) {
+ it++;
+ continue;
+ }
+
+ const ModelAction *rf = act->get_reads_from();
+ rel_heads_list_t release_heads;
+ bool complete;
+ complete = release_seq_heads(rf, &release_heads, pending);
+ for (unsigned int i = 0; i < release_heads.size(); i++) {
+ if (!act->has_synchronized_with(release_heads[i])) {
+ if (act->synchronize_with(release_heads[i]))
+ updated = true;
+ else
+ set_bad_synchronization();
+ }
+ }
+
+ if (updated) {
+ /* Re-check all pending release sequences */
+ work_queue->push_back(CheckRelSeqWorkEntry(NULL));
+ /* Re-check act for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(act));
+
+ /* propagate synchronization to later actions */
+ action_list_t::reverse_iterator rit = action_trace->rbegin();
+ for (; (*rit) != act; rit++) {
+ ModelAction *propagate = *rit;
+ if (act->happens_before(propagate)) {
+ propagate->synchronize_with(act);
+ /* Re-check 'propagate' for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(propagate));
+ }
+ }
+ }
+ if (complete) {
+ it = pending_rel_seqs->erase(it);
+ snapshot_free(pending);
+ } else {
+ it++;
+ }
+ }
+
+ // If we resolved promises or data races, see if we have realized a data race.
+ if (checkDataRaces()) {
+ set_assert();
+ }
+
+ return updated;
}
/**
int tid = id_to_int(act->get_tid());
action_trace->push_back(act);
- obj_map->ensureptr(act->get_location())->push_back(act);
+ obj_map->get_safe_ptr(act->get_location())->push_back(act);
- std::vector<action_list_t> *vec = obj_thrd_map->ensureptr(act->get_location());
+ std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
if (tid >= (int)vec->size())
- vec->resize(next_thread_id);
+ vec->resize(priv->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;
+
+ if (act->is_wait()) {
+ void *mutex_loc=(void *) act->get_value();
+ obj_map->get_safe_ptr(mutex_loc)->push_back(act);
+
+ std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(mutex_loc);
+ if (tid >= (int)vec->size())
+ vec->resize(priv->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)
+/**
+ * @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
{
- action_list_t *list = obj_map->ensureptr(location);
+ 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() || (*rit)->is_wait())
return *rit;
return NULL;
}
* @param tid The thread whose clock vector we want
* @return Desired clock vector
*/
-ClockVector * ModelChecker::get_cv(thread_id_t tid) {
+ClockVector * ModelChecker::get_cv(thread_id_t tid)
+{
return get_parent_action(tid)->get_cv();
}
+/**
+ * Resolve a set of Promises with a current write. The set is provided in the
+ * Node corresponding to @a write.
+ * @param write The ModelAction that is fulfilling Promises
+ * @return True if promises were resolved; false otherwise
+ */
+bool ModelChecker::resolve_promises(ModelAction *write)
+{
+ bool resolved = false;
+ std::vector< thread_id_t, ModelAlloc<thread_id_t> > threads_to_check;
-/** Resolve the given promises. */
-
-void ModelChecker::resolve_promises(ModelAction *write) {
- for (unsigned int i = 0, promise_index = 0;promise_index<promises->size(); i++) {
- Promise * promise = (*promises)[promise_index];
+ 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)) {
- ModelAction * read = promise->get_action();
+ ModelAction *read = promise->get_action();
+ if (read->is_rmw()) {
+ mo_graph->addRMWEdge(write, read);
+ }
read->read_from(write);
+ //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);
+ //Make sure the promise's value matches the write's value
+ ASSERT(promise->get_value() == write->get_value());
+ delete(promise);
+
+ promises->erase(promises->begin() + promise_index);
+ threads_to_check.push_back(read->get_tid());
+
+ resolved = true;
} else
promise_index++;
}
-}
-/** Compute the set of promises that could potentially be satisfied by
- * this action. */
+ //Check whether reading these writes has made threads unable to
+ //resolve promises
-void ModelChecker::compute_promises(ModelAction *curr) {
- for (unsigned int i = 0;i<promises->size();i++) {
- Promise * promise = (*promises)[i];
- const ModelAction * act = promise->get_action();
- if (!act->happens_before(curr)&&
- act->is_read()&&
- !act->is_synchronizing(curr)&&
- !act->same_thread(curr)&&
+ for(unsigned int i=0;i<threads_to_check.size();i++)
+ mo_check_promises(threads_to_check[i], write);
+
+ return resolved;
+}
+
+/**
+ * Compute the set of promises that could potentially be satisfied by this
+ * action. Note that the set computation actually appears in the Node, not in
+ * ModelChecker.
+ * @param curr The ModelAction that may satisfy promises
+ */
+void ModelChecker::compute_promises(ModelAction *curr)
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ const ModelAction *act = promise->get_action();
+ if (!act->happens_before(curr) &&
+ act->is_read() &&
+ !act->could_synchronize_with(curr) &&
+ !act->same_thread(curr) &&
+ act->get_location() == curr->get_location() &&
promise->get_value() == curr->get_value()) {
curr->get_node()->set_promise(i);
}
}
/** Checks promises in response to change in ClockVector Threads. */
-
-void ModelChecker::check_promises(ClockVector *old_cv, ClockVector * merge_cv) {
- for (unsigned int i = 0;i<promises->size();i++) {
- Promise * promise = (*promises)[i];
- const ModelAction * act = promise->get_action();
- if ((old_cv == NULL||!old_cv->synchronized_since(act))&&
+void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ const ModelAction *act = promise->get_action();
+ if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
merge_cv->synchronized_since(act)) {
- //This thread is no longer able to send values back to satisfy the promise
- int num_synchronized_threads = promise->increment_threads();
- if (num_synchronized_threads == model->get_num_threads()) {
+ if (promise->increment_threads(tid)) {
//Promise has failed
failed_promise = true;
return;
}
}
+/** Checks promises in response to addition to modification order for threads.
+ * Definitions:
+ * pthread is the thread that performed the read that created the promise
+ *
+ * pread is the read that created the promise
+ *
+ * pwrite is either the first write to same location as pread by
+ * pthread that is sequenced after pread or the value read by the
+ * first read to the same lcoation as pread by pthread that is
+ * sequenced after pread..
+ *
+ * 1. If tid=pthread, then we check what other threads are reachable
+ * through the mode order starting with pwrite. Those threads cannot
+ * perform a write that will resolve the promise due to modification
+ * order constraints.
+ *
+ * 2. If the tid is not pthread, we check whether pwrite can reach the
+ * action write through the modification order. If so, that thread
+ * cannot perform a future write that will resolve the promise due to
+ * modificatin order constraints.
+ *
+ * @parem tid The thread that either read from the model action
+ * write, or actually did the model action write.
+ *
+ * @parem write The ModelAction representing the relevant write.
+ */
+
+void ModelChecker::mo_check_promises(thread_id_t tid, const ModelAction *write) {
+ void * location = write->get_location();
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ const ModelAction *act = promise->get_action();
+
+ //Is this promise on the same location?
+ if ( act->get_location() != location )
+ continue;
+
+ //same thread as the promise
+ if ( act->get_tid()==tid ) {
+
+ //do we have a pwrite for the promise, if not, set it
+ if (promise->get_write() == NULL ) {
+ promise->set_write(write);
+ //The pwrite cannot happen before the promise
+ if (write->happens_before(act) && (write != act)) {
+ failed_promise = true;
+ return;
+ }
+ }
+ if (mo_graph->checkPromise(write, promise)) {
+ failed_promise = true;
+ return;
+ }
+ }
+
+ //Don't do any lookups twice for the same thread
+ if (promise->has_sync_thread(tid))
+ continue;
+
+ if (mo_graph->checkReachable(promise->get_write(), write)) {
+ if (promise->increment_threads(tid)) {
+ failed_promise = true;
+ return;
+ }
+ }
+ }
+}
+
+/**
+ * Compute the set of writes that may break the current pending release
+ * sequence. This information is extracted from previou release sequence
+ * calculations.
+ *
+ * @param curr The current ModelAction. Must be a release sequence fixup
+ * action.
+ */
+void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
+{
+ if (pending_rel_seqs->empty())
+ return;
+
+ struct release_seq *pending = pending_rel_seqs->back();
+ for (unsigned int i = 0; i < pending->writes.size(); i++) {
+ const ModelAction *write = pending->writes[i];
+ curr->get_node()->add_relseq_break(write);
+ }
+
+ /* NULL means don't break the sequence; just synchronize */
+ curr->get_node()->add_relseq_break(NULL);
+}
+
/**
* 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"
*/
void ModelChecker::build_reads_from_past(ModelAction *curr)
{
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->ensureptr(curr->get_location());
+ std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
unsigned int i;
ASSERT(curr->is_read());
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. */
- if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
+ if (!curr->is_seqcst() || (!act->is_seqcst() && (last_seq_cst == NULL || !act->happens_before(last_seq_cst))) || 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);
+
+ if (curr->get_sleep_flag() && ! curr->is_seqcst()) {
+ if (sleep_can_read_from(curr, act))
+ curr->get_node()->add_read_from(act);
+ } else
+ curr->get_node()->add_read_from(act);
}
/* Include at most one act per-thread that "happens before" curr */
if (!initialized) {
/** @todo Need a more informative way of reporting errors. */
printf("ERROR: may read from uninitialized atomic\n");
+ set_assert();
}
if (DBG_ENABLED() || !initialized) {
curr->get_node()->print_may_read_from();
printf("End printing may_read_from\n");
}
+}
- ASSERT(initialized);
+bool ModelChecker::sleep_can_read_from(ModelAction * curr, const ModelAction *write) {
+ while(true) {
+ Node *prevnode=write->get_node()->get_parent();
+ bool thread_sleep=prevnode->get_enabled_array()[id_to_int(curr->get_tid())]==THREAD_SLEEP_SET;
+ if (write->is_release()&&thread_sleep)
+ return true;
+ if (!write->is_rmw()) {
+ return false;
+ }
+ if (write->get_reads_from()==NULL)
+ return true;
+ write=write->get_reads_from();
+ }
}
static void print_list(action_list_t *list)
printf("---------------------------------------------------------------------\n");
printf("Trace:\n");
-
+ unsigned int hash=0;
+
for (it = list->begin(); it != list->end(); it++) {
(*it)->print();
+ hash=hash^(hash<<3)^((*it)->hash());
}
+ printf("HASH %u\n", hash);
printf("---------------------------------------------------------------------\n");
}
+#if SUPPORT_MOD_ORDER_DUMP
+void ModelChecker::dumpGraph(char *filename) {
+ char buffer[200];
+ sprintf(buffer, "%s.dot",filename);
+ FILE *file=fopen(buffer, "w");
+ fprintf(file, "digraph %s {\n",filename);
+ mo_graph->dumpNodes(file);
+ ModelAction ** thread_array=(ModelAction **)model_calloc(1, sizeof(ModelAction *)*get_num_threads());
+
+ for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
+ ModelAction *action=*it;
+ if (action->is_read()) {
+ fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(),action->get_seq_number(), action->get_tid());
+ if (action->get_reads_from()!=NULL)
+ fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
+ }
+ if (thread_array[action->get_tid()] != NULL) {
+ fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
+ }
+
+ thread_array[action->get_tid()]=action;
+ }
+ fprintf(file,"}\n");
+ model_free(thread_array);
+ fclose(file);
+}
+#endif
+
void ModelChecker::print_summary()
{
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);
+ sprintf(buffername, "graph%04u", num_executions);
+ dumpGraph(buffername);
+#endif
if (!isfinalfeasible())
printf("INFEASIBLE EXECUTION!\n");
scheduler->add_thread(t);
}
+/**
+ * Removes a thread from the scheduler.
+ * @param the thread to remove.
+ */
void ModelChecker::remove_thread(Thread *t)
{
scheduler->remove_thread(t);
}
+/**
+ * @brief Get a Thread reference by its ID
+ * @param tid The Thread's ID
+ * @return A Thread reference
+ */
+Thread * ModelChecker::get_thread(thread_id_t tid) const
+{
+ return thread_map->get(id_to_int(tid));
+}
+
+/**
+ * @brief Get a reference to the Thread in which a ModelAction was executed
+ * @param act The ModelAction
+ * @return A Thread reference
+ */
+Thread * ModelChecker::get_thread(ModelAction *act) const
+{
+ return get_thread(act->get_tid());
+}
+
/**
* 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()).
+ *
+ * @param act The current action that will be explored. May be NULL only if
+ * trace is exiting via an assertion (see ModelChecker::set_assert and
+ * ModelChecker::has_asserted).
* @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
*/
int ModelChecker::switch_to_master(ModelAction *act)
{
DBG();
- Thread * old = thread_current();
+ Thread *old = thread_current();
set_current_action(act);
old->set_state(THREAD_READY);
return Thread::swap(old, &system_context);
* @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 = priv->current_action ? get_thread(priv->current_action) : NULL;
if (curr) {
if (curr->get_state() == THREAD_READY) {
- check_current_action();
- scheduler->add_thread(curr);
- } else if (curr->get_state() == THREAD_RUNNING) {
- /* Stopped while running; i.e., completed */
- curr->complete();
+ ASSERT(priv->current_action);
+
+ priv->nextThread = check_current_action(priv->current_action);
+ priv->current_action = NULL;
+
+ if (curr->is_blocked() || curr->is_complete())
+ scheduler->remove_thread(curr);
} else {
ASSERT(false);
}
}
- next = scheduler->next_thread();
+ Thread *next = scheduler->next_thread(priv->nextThread);
/* Infeasible -> don't take any more steps */
if (!isfeasible())
return false;
- if (next)
- next->set_state(THREAD_RUNNING);
- DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
+ if (params.bound != 0) {
+ if (priv->used_sequence_numbers > params.bound) {
+ return false;
+ }
+ }
+
+ DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
+ next ? id_to_int(next->get_id()) : -1);
+
+ /*
+ * Launch end-of-execution release sequence fixups only when there are:
+ *
+ * (1) no more user threads to run (or when execution replay chooses
+ * the 'model_thread')
+ * (2) pending release sequences
+ * (3) pending assertions (i.e., data races)
+ * (4) no pending promises
+ */
+ if (!pending_rel_seqs->empty() && (!next || next->is_model_thread()) &&
+ isfinalfeasible() && !unrealizedraces.empty()) {
+ printf("*** WARNING: release sequence fixup action (%zu pending release seuqences) ***\n",
+ pending_rel_seqs->size());
+ ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
+ std::memory_order_seq_cst, NULL, VALUE_NONE,
+ model_thread);
+ set_current_action(fixup);
+ return true;
+ }
/* next == NULL -> don't take any more steps */
if (!next)
return false;
+
+ next->set_state(THREAD_RUNNING);
+
+ 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);
}