#include "promise.h"
#include "datarace.h"
#include "mutex.h"
+#include "threads.h"
#define INITIAL_THREAD_ID 0
/** @brief Constructor */
ModelChecker::ModelChecker(struct model_params params) :
/* Initialize default scheduler */
+ params(params),
scheduler(new Scheduler()),
num_executions(0),
num_feasible_executions(0),
- params(params),
diverge(NULL),
+ 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>()),
obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
promises(new std::vector<Promise *>()),
futurevalues(new std::vector<struct PendingFutureValue>()),
- lazy_sync_with_release(new HashTable<void *, action_list_t, uintptr_t, 4>()),
+ pending_rel_seqs(new std::vector<struct release_seq *>()),
thrd_last_action(new std::vector<ModelAction *>(1)),
node_stack(new NodeStack()),
mo_graph(new CycleGraph()),
failed_promise(false),
too_many_reads(false),
- asserted(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;
-
- lazy_sync_size = &priv->lazy_sync_size;
}
/** @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 (*promises)[i];
delete promises;
- delete lazy_sync_with_release;
+ delete pending_rel_seqs;
delete thrd_last_action;
delete node_stack;
node_stack->reset_execution();
failed_promise = false;
too_many_reads = false;
+ bad_synchronization = false;
reset_asserted();
snapshotObject->backTrackBeforeStep(0);
}
}
/** @return the number of user threads created during this execution */
-int ModelChecker::get_num_threads()
+unsigned int ModelChecker::get_num_threads()
{
return priv->next_thread_id;
}
+/** @return The currently executing Thread. */
+Thread * ModelChecker::get_current_thread()
+{
+ return scheduler->get_current_thread();
+}
+
/** @return a sequence number for a new ModelAction */
modelclock_t ModelChecker::get_next_seq_num()
{
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()) {
/* The next node will try to satisfy a different set of promises. */
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. */
+ scheduler->remove_sleep(thread_map->get(id_to_int(tid)));
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);
+ 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);
+ 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);
+ }
+ }
+ }
+}
+
/**
* Queries the model-checker for more executions to explore and, if one
* exists, resets the model-checker state to execute a new execution.
DBG();
num_executions++;
- if (isfinalfeasible())
+
+ 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: %lu\n",
+ pending_rel_seqs->size());
if (isfinalfeasible() || DBG_ENABLED())
print_summary();
action_list_t::reverse_iterator rit;
for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *prev = *rit;
- if (act->is_synchronizing(prev))
+ if (prev->could_synchronize_with(act))
return prev;
}
break;
return NULL;
}
-/** This method find backtracking points where we should try to
+/** 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)
{
Thread *t = get_thread(act);
int low_tid, high_tid;
if (node->is_enabled(t)) {
- low_tid=id_to_int(act->get_tid());
- high_tid=low_tid+1;
+ low_tid = id_to_int(act->get_tid());
+ high_tid = low_tid+1;
} else {
- low_tid=0;
- high_tid=get_num_threads();
+ 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);
+
+ for(int i = low_tid; i < high_tid; i++) {
+ thread_id_t tid = int_to_id(i);
+
if (!node->is_enabled(tid))
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",
- prev->get_tid(), t->get_id());
+ id_to_int(prev->get_tid()),
+ id_to_int(t->get_id()));
if (DBG_ENABLED()) {
prev->print();
act->print();
bool r_status = false;
if (!second_part_of_rmw) {
- check_recency(curr);
+ check_recency(curr, reads_from);
r_status = r_modification_order(curr, reads_from);
}
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 */
/**
* Processes a lock, trylock, or unlock model action. @param curr is
- * the read model action to process.
+ * 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
*
* 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
*/
-
-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()) {
+bool 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;
+ bool success = !state->islocked;
curr->set_try_lock(success);
if (!success) {
get_thread(curr)->set_return_value(0);
}
//otherwise fall into the lock case
case ATOMIC_LOCK: {
- if (curr->get_cv()->getClock(state->alloc_tid)<=state->alloc_clock) {
+ 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);
+ state->islocked = true;
+ ModelAction *unlock = get_last_unlock(curr);
//synchronize with the previous unlock statement
- if ( unlock != NULL )
+ if (unlock != NULL) {
curr->synchronize_with(unlock);
+ return true;
+ }
break;
}
case ATOMIC_UNLOCK: {
//unlock the lock
- state->islocked=false;
+ state->islocked = false;
//wake up the other threads
- action_list_t * waiters = lock_waiters_map->get_safe_ptr(curr->get_location());
+ 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()));
+ for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
+ scheduler->wake(get_thread(*rit));
}
waiters->clear();
break;
default:
ASSERT(0);
}
+ return false;
}
-
/**
* Process a write ModelAction
* @param curr The ModelAction to process
bool updated_promises = resolve_promises(curr);
if (promises->size() == 0) {
- for (unsigned int i = 0; i<futurevalues->size(); i++) {
+ 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))
}
mo_graph->commitChanges();
+ mo_check_promises(curr->get_tid(), curr);
+
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 *waiting, *blocking;
+ waiting = get_thread(curr);
+ blocking = (Thread *)curr->get_location();
+ if (!blocking->is_complete()) {
+ blocking->push_wait_list(curr);
+ scheduler->sleep(waiting);
+ } else {
+ do_complete_join(curr);
+ 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();
+ Thread *wake = get_thread(act);
+ scheduler->wake(wake);
+ do_complete_join(act);
+ updated = true; /* trigger rel-seq checks */
+ }
+ th->complete();
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_START: {
+ check_promises(curr->get_tid(), NULL, curr->get_cv());
+ break;
+ }
+ default:
+ break;
+ }
+
+ return updated;
+}
+
/**
* Initialize the current action by performing one or more of the following
* actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
if (curr->is_rmwc() || curr->is_rmw()) {
newcurr = process_rmw(curr);
delete curr;
- compute_promises(newcurr);
+
+ 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());
+ 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()));
+ /* 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
*/
- curr->create_cv(get_parent_action(curr->get_tid()));
- if (curr->is_write())
- compute_promises(curr);
+ if (newcurr->is_write())
+ compute_promises(newcurr);
}
return newcurr;
}
* @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();
+ 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
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)) {
- //we'll make the execution look like we chose to run this action
- //much later...when a lock is actually available to relese
+ /* Make the execution look like we chose to run this action
+ * much later, when a lock is actually available to release */
get_current_thread()->set_pending(curr);
- remove_thread(get_current_thread());
+ scheduler->sleep(get_current_thread());
return get_next_thread(NULL);
}
+ wake_up_sleeping_actions(curr);
+
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_reads_from_past(curr);
curr = newcurr;
- /* Thread specific actions */
- switch (curr->get_type()) {
- case THREAD_CREATE: {
- Thread *th = (Thread *)curr->get_location();
- th->set_creation(curr);
- break;
- }
- case THREAD_JOIN: {
- Thread *waiting, *blocking;
- waiting = get_thread(curr);
- blocking = (Thread *)curr->get_location();
- if (!blocking->is_complete()) {
- blocking->push_wait_list(curr);
- scheduler->sleep(waiting);
- } else {
- do_complete_join(curr);
- }
- break;
- }
- case THREAD_FINISH: {
- Thread *th = get_thread(curr);
- while (!th->wait_list_empty()) {
- ModelAction *act = th->pop_wait_list();
- Thread *wake = get_thread(act);
- scheduler->wake(wake);
- do_complete_join(act);
- }
- th->complete();
- break;
- }
- case THREAD_START: {
- check_promises(NULL, curr->get_cv());
- break;
- }
- default:
- break;
- }
-
+ /* 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 updated = false;
+ 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))
- updated = true;
+ update = true;
if (act->is_write() && process_write(act))
- updated = true;
+ update = true;
- if (act->is_mutex_op())
- process_mutex(act);
+ if (act->is_mutex_op() && process_mutex(act))
+ update_all = true;
- if (updated)
+ if (update_all)
+ work_queue.push_back(CheckRelSeqWorkEntry(NULL));
+ else if (update)
work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
break;
}
bool updated = false;
if (act->is_read()) {
- if (r_modification_order(act, act->get_reads_from()))
+ 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()));
}
check_curr_backtracking(curr);
-
set_backtracking(curr);
-
return get_next_thread(curr);
}
/** @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;
+ return promises->size() == 0 && pending_rel_seqs->size() == 0;
}
/** @return whether the current partial trace is feasible. */
bool ModelChecker::isfeasible() {
+ if (DBG_ENABLED() && mo_graph->checkForRMWViolation())
+ DEBUG("Infeasible: RMW violation\n");
+
return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW();
}
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 && !promises_expired();
+ return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !bad_synchronization && !promises_expired();
}
/** Returns whether the current completed trace is feasible. */
/** 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 *lastread = get_last_action(act->get_tid());
lastread->process_rmw(act);
if (act->is_rmw() && lastread->get_reads_from()!=NULL) {
mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
*
* If so, we decide that the execution is no longer feasible.
*/
-void ModelChecker::check_recency(ModelAction *curr) {
+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();
ModelAction *act = *rit;
if (!act->is_read())
return;
- if (act->get_reads_from() != curr->get_reads_from())
+
+ 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==curr->get_reads_from())
+ if (write==rf)
continue;
/* Test to see whether this is a feasible write to read from*/
/**
* Updates the mo_graph with the constraints imposed from the current
- * read.
+ * read.
*
* Basic idea is the following: Go through each other thread and find
* the lastest action that happened before our read. Two cases:
}
} else {
const ModelAction *prevreadfrom = act->get_reads_from();
- if (prevreadfrom != NULL && rf != prevreadfrom) {
+ //if the previous read is unresolved, keep going...
+ if (prevreadfrom == NULL)
+ continue;
+
+ if (rf != prevreadfrom) {
mo_graph->addEdge(prevreadfrom, rf);
added = true;
}
* 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
* @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());
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()) {
+ 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)
mo_graph->addEdge(rf, postreadfrom);
- } else if (rf != lastact) {
- mo_graph->addEdge(rf, lastact);
+ } 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;
}
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.
+ * 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())
- break;
- else
+ if (curr->is_rmw()) {
+ if (curr->get_reads_from()!=NULL)
+ break;
+ else
+ continue;
+ } else
continue;
}
*/
if (act->is_write())
mo_graph->addEdge(act, curr);
- else if (act->is_read() && act->get_reads_from() != NULL)
+ 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
*/
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())) {
+ (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);
}
/** 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;
return true;
for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
- if (search==reader)
+ if (search == reader)
return false;
if (search->get_tid() == reader->get_tid() &&
search->happens_before(reader))
* @todo Finish lazy updating, when promises are fulfilled in the future
* @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
+ * @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
+ * 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_head(const ModelAction *rf, rel_heads_list_t *release_heads) const
+bool ModelChecker::release_seq_heads(const ModelAction *rf,
+ rel_heads_list_t *release_heads,
+ struct release_seq *pending) const
{
- if (!rf) {
- /* read from future: need to settle this later */
- return false; /* incomplete */
- }
+ /* Only check for release sequences if there are no cycles */
+ if (mo_graph->checkForCycles())
+ return false;
- ASSERT(rf->is_write());
+ while (rf) {
+ ASSERT(rf->is_write());
+
+ if (rf->is_release())
+ release_heads->push_back(rf);
+ if (!rf->is_rmw())
+ break; /* End of RMW chain */
- if (rf->is_release())
- release_heads->push_back(rf);
- if (rf->is_rmw()) {
- /* We need a RMW action that is both an acquire and release to stop */
/** @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 */
- return release_seq_head(rf->get_reads_from(), release_heads);
+
+ 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 */
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)
* the release seq? */
bool future_ordered = false;
+ ModelAction *last = get_last_action(int_to_id(i));
+ if (last && (rf->happens_before(last) ||
+ get_thread(int_to_id(i))->is_complete()))
+ 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 */
/* release --mo-> act --mo--> rf */
return true; /* complete */
}
+ /* act may break release sequence */
+ pending->writes.push_back(act);
certain = false;
}
if (!future_ordered)
- return false; /* This thread is uncertain */
+ certain = false; /* This thread is uncertain */
}
- if (certain)
+ if (certain) {
release_heads->push_back(release);
+ pending->writes.clear();
+ } else {
+ pending->release = release;
+ pending->rf = rf;
+ }
return certain;
}
* @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_head
+ * @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();
- bool complete;
- complete = release_seq_head(rf, release_heads);
- if (!complete) {
+ 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 */
- action_list_t *list;
- list = lazy_sync_with_release->get_safe_ptr(act->get_location());
- list->push_back(act);
- (*lazy_sync_size)++;
+ pending_rel_seqs->push_back(sequence);
+ } else {
+ snapshot_free(sequence);
}
}
* modification order information is present at the time an action occurs.
*
* @param location The location/object that should be checked for release
- * sequence resolutions
+ * 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
*/
bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
{
- action_list_t *list;
- list = lazy_sync_with_release->getptr(location);
- if (!list)
- return false;
-
bool updated = false;
- action_list_t::iterator it = list->begin();
- while (it != list->end()) {
- ModelAction *act = *it;
+ std::vector<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_head(rf, &release_heads);
+ 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])) {
- updated = true;
- act->synchronize_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 it = action_trace->rbegin();
- while ((*it) != act) {
- ModelAction *propagate = *it;
+ 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 */
}
}
if (complete) {
- it = list->erase(it);
- (*lazy_sync_size)--;
- } else
+ 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.
(*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 threadid=id_to_int(tid);
- if (threadid<(int)thrd_last_action->size())
+ int threadid = id_to_int(tid);
+ if (threadid < (int)thrd_last_action->size())
return (*thrd_last_action)[id_to_int(tid)];
else
return NULL;
* check
* @return The last seq_cst write
*/
-ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr)
+ModelAction * ModelChecker::get_last_seq_cst(ModelAction *curr) const
{
void *location = curr->get_location();
action_list_t *list = obj_map->get_safe_ptr(location);
}
/**
- * Gets the last unlock operation
- * performed on a particular mutex (i.e., memory location).
+ * 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)
+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) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
+ /* 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())
bool ModelChecker::resolve_promises(ModelAction *write)
{
bool resolved = false;
+ std::vector<thread_id_t> threads_to_check;
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();
- read->read_from(write);
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);
+ //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++;
}
+
+ //Check whether reading these writes has made threads unable to
+ //resolve promises
+
+ for(unsigned int i=0;i<threads_to_check.size();i++)
+ mo_check_promises(threads_to_check[i], write);
+
return resolved;
}
const ModelAction *act = promise->get_action();
if (!act->happens_before(curr) &&
act->is_read() &&
- !act->is_synchronizing(curr) &&
+ !act->could_synchronize_with(curr) &&
!act->same_thread(curr) &&
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)
+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 == 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);
+ }
+ 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;
+ }
+ }
+ }
+}
+
/**
* 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"
continue;
/* Don't consider more than one seq_cst write if we are a seq_cst read. */
- if (!curr->is_seqcst()|| (!act->is_seqcst() && (last_seq_cst==NULL||!act->happens_before(last_seq_cst))) || 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();
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");
#if SUPPORT_MOD_ORDER_DUMP
scheduler->print();
char buffername[100];
- sprintf(buffername, "exec%u",num_executions);
+ sprintf(buffername, "exec%04u", num_executions);
mo_graph->dumpGraphToFile(buffername);
+ sprintf(buffername, "graph%04u", num_executions);
+ dumpGraph(buffername);
#endif
if (!isfinalfeasible())
* 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. Must not be NULL.
+ *
+ * @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)
if (has_asserted())
return false;
- Thread * 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->remove_thread(curr);
} else {
ASSERT(false);
}
}
- Thread * next = scheduler->next_thread(priv->nextThread);
+ 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);
+ DEBUG("(%d, %d)\n", curr ? id_to_int(curr->get_id()) : -1,
+ next ? id_to_int(next->get_id()) : -1);
/* next == NULL -> don't take any more steps */
if (!next)
return false;
- if ( next->get_pending() != NULL ) {
- //restart a pending action
+ 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);
projects / model-checker.git / blobdiff