#include "snapshot-interface.h"
#include "common.h"
#include "clockvector.h"
+#include "cyclegraph.h"
+#include "promise.h"
#define INITIAL_THREAD_ID 0
ModelChecker *model;
/** @brief Constructor */
-ModelChecker::ModelChecker()
- :
+ModelChecker::ModelChecker(struct model_params params) :
/* Initialize default scheduler */
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),
diverge(NULL),
- nextThread(THREAD_ID_T_NONE),
+ nextThread(NULL),
action_trace(new action_list_t()),
- thread_map(new std::map<int, Thread *>),
- obj_map(new std::map<const void *, action_list_t>()),
- obj_thrd_map(new std::map<void *, std::vector<action_list_t> >()),
+ 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 *>()),
+ lazy_sync_with_release(new HashTable<void *, std::list<ModelAction *>, uintptr_t, 4>()),
thrd_last_action(new std::vector<ModelAction *>(1)),
node_stack(new NodeStack()),
- next_backtrack(NULL)
+ next_backtrack(NULL),
+ mo_graph(new CycleGraph()),
+ failed_promise(false)
{
}
/** @brief Destructor */
ModelChecker::~ModelChecker()
{
- std::map<int, Thread *>::iterator it;
- for (it = thread_map->begin(); it != thread_map->end(); it++)
- delete (*it).second;
+ for (int i = 0; i < get_num_threads(); i++)
+ delete thread_map->get(i);
delete thread_map;
delete obj_thrd_map;
delete obj_map;
delete action_trace;
+
+ for (unsigned int i = 0; i < promises->size(); i++)
+ delete (*promises)[i];
+ delete promises;
+
+ delete lazy_sync_with_release;
+
delete thrd_last_action;
delete node_stack;
delete scheduler;
+ delete mo_graph;
}
/**
current_action = NULL;
next_thread_id = INITIAL_THREAD_ID;
used_sequence_numbers = 0;
- nextThread = 0;
+ nextThread = NULL;
next_backtrack = NULL;
+ failed_promise = false;
snapshotObject->backTrackBeforeStep(0);
}
return ++used_sequence_numbers;
}
-/**
- * Performs the "scheduling" for the model-checker. That is, it checks if the
- * model-checker has selected a "next thread to run" and returns it, if
- * available. This function should be called from the Scheduler routine, where
- * the Scheduler falls back to a default scheduling routine if needed.
- *
- * @return The next thread chosen by the model-checker. If the model-checker
- * makes no selection, retuns NULL.
- */
-Thread * ModelChecker::schedule_next_thread()
-{
- Thread *t;
- if (nextThread == THREAD_ID_T_NONE)
- return NULL;
- t = (*thread_map)[id_to_int(nextThread)];
-
- ASSERT(t != NULL);
-
- return t;
-}
-
/**
* Choose the next thread in the replay sequence.
*
* from the backtracking set. Otherwise, simply returns the next thread in the
* sequence that is being replayed.
*/
-thread_id_t ModelChecker::get_next_replay_thread()
+Thread * ModelChecker::get_next_replay_thread()
{
- ModelAction *next;
thread_id_t tid;
/* 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 */
- next = node_stack->get_next()->get_action();
+ ModelAction *next = node_stack->get_next()->get_action();
if (next == diverge) {
- Node *node = next->get_node()->get_parent();
-
+ Node *nextnode = next->get_node();
/* Reached divergence point */
+ 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);
+ } else if (nextnode->increment_read_from()) {
+ /* The next node will read from a different value. */
+ tid = next->get_tid();
+ node_stack->pop_restofstack(2);
+ } else if (nextnode->increment_future_value()) {
+ /* The next node will try to read from a different future value. */
+ tid = next->get_tid();
+ node_stack->pop_restofstack(2);
+ } else {
+ /* Make a different thread execute for next step */
+ Node *node = nextnode->get_parent();
+ tid = node->get_next_backtrack();
+ node_stack->pop_restofstack(1);
+ }
DEBUG("*** Divergence point ***\n");
- tid = node->get_next_backtrack();
diverge = NULL;
} else {
tid = next->get_tid();
}
DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
- return tid;
+ ASSERT(tid != THREAD_ID_T_NONE);
+ return thread_map->get(id_to_int(tid));
}
/**
DBG();
num_executions++;
- print_summary();
+
+ if (isfinalfeasible() || DBG_ENABLED())
+ print_summary();
+
if ((diverge = model->get_next_backtrack()) == NULL)
return false;
return NULL;
}
/* 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 = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *prev = *rit;
if (act->is_synchronizing(prev))
return prev;
}
}
+/**
+ * Returns last backtracking point. The model checker will explore a different
+ * path for this point in the next execution.
+ * @return The ModelAction at which the next execution should diverge.
+ */
ModelAction * ModelChecker::get_next_backtrack()
{
ModelAction *next = next_backtrack;
void ModelChecker::check_current_action(void)
{
- Node *currnode;
-
ModelAction *curr = this->current_action;
- ModelAction *tmp;
- current_action = NULL;
+ bool already_added = false;
+ this->current_action = NULL;
if (!curr) {
DEBUG("trying to push NULL action...\n");
return;
}
- tmp = node_stack->explore_action(curr);
- if (tmp) {
- /* Discard duplicate ModelAction; use action from NodeStack */
+ if (curr->is_rmwc() || curr->is_rmw()) {
+ ModelAction *tmp = process_rmw(curr);
+ already_added = true;
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);
+ 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);
+ }
}
/* Assign 'creation' parent */
th->set_creation(curr);
}
- nextThread = get_next_replay_thread();
+ /* Deal with new thread */
+ if (curr->get_type() == THREAD_START)
+ check_promises(NULL, curr->get_cv());
+
+ /* Assign reads_from values */
+ Thread *th = get_thread(curr->get_tid());
+ uint64_t value = VALUE_NONE;
+ bool updated = false;
+ 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);
+ if (r_modification_order(curr,reads_from))
+ updated = true;
+ } 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);
+ }
+ } else if (curr->is_write()) {
+ if (w_modification_order(curr))
+ updated = true;;
+ if (resolve_promises(curr))
+ updated = true;
+ }
+
+ if (updated)
+ resolve_release_sequences(curr->get_location());
+
+ th->set_return_value(value);
+
+ /* Add action to list. */
+ if (!already_added)
+ add_action_to_lists(curr);
- currnode = curr->get_node()->get_parent();
+ /** @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 (!currnode->backtrack_empty())
+ /* Do not split atomic actions. */
+ if (curr->is_rmwr())
+ nextThread = thread_current();
+ else
+ nextThread = get_next_replay_thread();
+
+ 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;
set_backtracking(curr);
+}
- add_action_to_lists(curr);
+/** @returns whether the current partial trace is feasible. */
+bool ModelChecker::isfeasible() {
+ return !mo_graph->checkForCycles() && !failed_promise;
+}
- /* Assign reads_from values */
- /* TODO: perform release/acquire synchronization here; include
- * reads_from as ModelAction member? */
- Thread *th = get_thread(curr->get_tid());
- int value = VALUE_NONE;
- if (curr->is_read()) {
- const ModelAction *reads_from = curr->get_node()->get_next_read_from();
- value = reads_from->get_value();
- /* Assign reads_from, perform release/acquire synchronization */
- curr->read_from(reads_from);
+/** Returns whether the current completed trace is feasible. */
+bool ModelChecker::isfinalfeasible() {
+ 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);
+ lastread->process_rmw(act);
+ if (act->is_rmw())
+ mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
+ return lastread;
+}
+
+/**
+ * Updates the mo_graph with the constraints imposed from the current read.
+ * @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
+ */
+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 (i = 0; i < thrd_lists->size(); i++) {
+ /* Iterate over actions in thread, starting from most recent */
+ action_list_t *list = &(*thrd_lists)[i];
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+
+ /* Include at most one act per-thread that "happens before" curr */
+ if (act->happens_before(curr)) {
+ if (act->is_read()) {
+ const ModelAction *prevreadfrom = act->get_reads_from();
+ if (prevreadfrom != NULL && rf != prevreadfrom) {
+ mo_graph->addEdge(prevreadfrom, rf);
+ added = true;
+ }
+ } else if (rf != act) {
+ mo_graph->addEdge(act, rf);
+ added = true;
+ }
+ break;
+ }
+ }
}
- th->set_return_value(value);
+
+ return added;
+}
+
+/** Updates the mo_graph 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->get_safe_ptr(curr->get_location());
+ unsigned int i;
+ ASSERT(curr->is_read());
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Iterate over actions in thread, starting from most recent */
+ action_list_t *list = &(*thrd_lists)[i];
+ action_list_t::reverse_iterator rit;
+ ModelAction *lastact = NULL;
+
+ /* Find last action that happens after curr */
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+ if (curr->happens_before(act)) {
+ 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 (postreadfrom != NULL&&rf != postreadfrom)
+ mo_graph->addEdge(rf, postreadfrom);
+ } else if (rf != lastact) {
+ mo_graph->addEdge(rf, lastact);
+ }
+ break;
+ }
+ }
+}
+
+/**
+ * Updates the mo_graph with the constraints imposed from the current write.
+ * @param curr The current action. Must be a write.
+ * @return True if modification order edges were added; false otherwise
+ */
+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) {
+ mo_graph->addEdge(last_seq_cst, curr);
+ added = true;
+ }
+ }
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Iterate over actions in thread, starting from most recent */
+ action_list_t *list = &(*thrd_lists)[i];
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+
+ /* Include at most one act per-thread that "happens before" curr */
+ if (act->happens_before(curr)) {
+ if (act->is_read())
+ mo_graph->addEdge(act->get_reads_from(), curr);
+ else
+ mo_graph->addEdge(act, curr);
+ added = true;
+ break;
+ } else if (act->is_read() && !act->is_synchronizing(curr) &&
+ !act->same_thread(curr)) {
+ /* We have an action that:
+ (1) did not happen before us
+ (2) is a read and we are a write
+ (3) cannot synchronize with us
+ (4) is in a different thread
+ =>
+ that read could potentially read from our write.
+ */
+ if (act->get_node()->add_future_value(curr->get_value()) &&
+ (!next_backtrack || *act > *next_backtrack))
+ next_backtrack = act;
+ }
+ }
+ }
+
+ return added;
+}
+
+/**
+ * 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.
+ *
+ * @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
+ * execution of this function, release_heads will contain the heads of all the
+ * relevant release sequences, if any exists
+ * @return true, if the ModelChecker is certain that release_heads is complete;
+ * false otherwise
+ */
+bool ModelChecker::release_seq_head(const ModelAction *rf,
+ std::vector<const ModelAction *> *release_heads) const
+{
+ ASSERT(rf->is_write());
+ if (!rf) {
+ /* read from future: need to settle this later */
+ return false; /* incomplete */
+ }
+ if (rf->is_release())
+ release_heads->push_back(rf);
+ if (rf->is_rmw()) {
+ if (rf->is_acquire())
+ return true; /* complete */
+ return release_seq_head(rf->get_reads_from(), release_heads);
+ }
+ 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 */
+ for (rit = list->rbegin(); rit != list->rend(); rit++)
+ if (*rit == rf)
+ break;
+
+ /* 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));
+
+ 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];
+ 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;
+ if (rf->happens_before(act))
+ continue;
+
+ /* Check modification order */
+ if (mo_graph->checkReachable(rf, act))
+ /* rf --mo--> act */
+ 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 */
+ }
+ certain = false;
+ }
+ }
+
+ if (certain)
+ release_heads->push_back(release);
+ 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_head
+ */
+void ModelChecker::get_release_seq_heads(ModelAction *act,
+ std::vector<const ModelAction *> *release_heads)
+{
+ const ModelAction *rf = act->get_reads_from();
+ bool complete;
+ complete = release_seq_head(rf, release_heads);
+ if (!complete) {
+ /* add act to 'lazy checking' list */
+ std::list<ModelAction *> *list;
+ list = lazy_sync_with_release->get_safe_ptr(act->get_location());
+ list->push_back(act);
+ }
+}
+
+/**
+ * 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
+ * @return True if any updates occurred (new synchronization, new mo_graph edges)
+ */
+bool ModelChecker::resolve_release_sequences(void *location)
+{
+ std::list<ModelAction *> *list;
+ list = lazy_sync_with_release->getptr(location);
+ if (!list)
+ return false;
+
+ bool updated = false;
+ std::list<ModelAction *>::iterator it = list->begin();
+ while (it != list->end()) {
+ ModelAction *act = *it;
+ const ModelAction *rf = act->get_reads_from();
+ std::vector<const ModelAction *> release_heads;
+ bool complete;
+ complete = release_seq_head(rf, &release_heads);
+ 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 (updated) {
+ /* propagate synchronization to later actions */
+ action_list_t::reverse_iterator it = action_trace->rbegin();
+ while ((*it) != act) {
+ ModelAction *propagate = *it;
+ if (act->happens_before(propagate))
+ /** @todo new mo_graph edges along with
+ * this synchronization? */
+ propagate->synchronize_with(act);
+ }
+ }
+ if (complete)
+ it = list->erase(it);
+ else
+ it++;
+ }
+
+ return updated;
}
/**
int tid = id_to_int(act->get_tid());
action_trace->push_back(act);
- (*obj_map)[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)[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)[tid].push_back(act);
return (*thrd_last_action)[id_to_int(tid)];
}
+/**
+ * Gets the last memory_order_seq_cst action (in the total global sequence)
+ * performed on a particular object (i.e., memory location).
+ * @param location The object location to check
+ * @return The last seq_cst action performed
+ */
+ModelAction * ModelChecker::get_last_seq_cst(const void *location)
+{
+ action_list_t *list = obj_map->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())
+ return *rit;
+ return NULL;
+}
+
ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
{
ModelAction *parent = get_last_action(tid);
return parent;
}
-ClockVector * ModelChecker::get_cv(thread_id_t tid) {
+/**
+ * Returns the clock vector for a given thread.
+ * @param tid The thread whose clock vector we want
+ * @return Desired clock vector
+ */
+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;
+ 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);
+ r_modification_order(read, write);
+ post_r_modification_order(read, write);
+ promises->erase(promises->begin() + promise_index);
+ resolved = true;
+ } else
+ promise_index++;
+ }
+ 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->is_synchronizing(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)
+{
+ 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()) {
+ //Promise has failed
+ 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"
*/
void ModelChecker::build_reads_from_past(ModelAction *curr)
{
- std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[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());
+ ModelAction *last_seq_cst = NULL;
+
/* Track whether this object has been initialized */
bool initialized = false;
+ if (curr->is_seqcst()) {
+ last_seq_cst = get_last_seq_cst(curr->get_location());
+ /* We have to at least see the last sequentially consistent write,
+ so we are initialized. */
+ if (last_seq_cst != NULL)
+ initialized = true;
+ }
+
+ /* Iterate over all threads */
for (i = 0; i < thrd_lists->size(); i++) {
+ /* Iterate over actions in thread, starting from most recent */
action_list_t *list = &(*thrd_lists)[i];
action_list_t::reverse_iterator rit;
for (rit = list->rbegin(); rit != list->rend(); rit++) {
if (!act->is_write())
continue;
- DEBUG("Adding action to may_read_from:\n");
- if (DBG_ENABLED()) {
- act->print();
- curr->print();
+ /* Don't consider more than one seq_cst write if we are a seq_cst read. */
+ if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
+ DEBUG("Adding action to may_read_from:\n");
+ if (DBG_ENABLED()) {
+ act->print();
+ curr->print();
+ }
+ curr->get_node()->add_read_from(act);
}
- curr->get_node()->add_read_from(act);
/* Include at most one act per-thread that "happens before" curr */
if (act->happens_before(curr)) {
}
if (!initialized) {
- /* TODO: need a more informative way of reporting errors */
+ /** @todo Need a more informative way of reporting errors. */
printf("ERROR: may read from uninitialized atomic\n");
}
printf("---------------------------------------------------------------------\n");
}
-void ModelChecker::print_summary(void)
+void ModelChecker::print_summary()
{
printf("\n");
printf("Number of executions: %d\n", num_executions);
scheduler->print();
+ if (!isfinalfeasible())
+ printf("INFEASIBLE EXECUTION!\n");
print_list(action_trace);
printf("\n");
}
-int ModelChecker::add_thread(Thread *t)
+/**
+ * Add a Thread to the system for the first time. Should only be called once
+ * per thread.
+ * @param t The Thread to add
+ */
+void ModelChecker::add_thread(Thread *t)
{
- (*thread_map)[id_to_int(t->get_id())] = t;
+ thread_map->put(id_to_int(t->get_id()), t);
scheduler->add_thread(t);
- return 0;
}
void ModelChecker::remove_thread(Thread *t)
scheduler->remove_thread(t);
}
+/**
+ * Switch from a user-context to the "master thread" context (a.k.a. system
+ * context). This switch is made with the intention of exploring a particular
+ * model-checking action (described by a ModelAction object). Must be called
+ * from a user-thread context.
+ * @param act The current action that will be explored. May be NULL, although
+ * there is little reason to switch to the model-checker without an action to
+ * explore (note: act == NULL is sometimes used as a hack to allow a thread to
+ * yield control without performing any progress; see thrd_join()).
+ * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
+ */
int ModelChecker::switch_to_master(ModelAction *act)
{
- Thread *old;
-
DBG();
- old = thread_current();
+ Thread *old = thread_current();
set_current_action(act);
old->set_state(THREAD_READY);
- return Thread::swap(old, get_system_context());
+ return Thread::swap(old, &system_context);
+}
+
+/**
+ * Takes the next step in the execution, if possible.
+ * @return Returns true (success) if a step was taken and false otherwise.
+ */
+bool ModelChecker::take_step() {
+ Thread *curr, *next;
+
+ curr = thread_current();
+ 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();
+ } else {
+ ASSERT(false);
+ }
+ }
+ next = scheduler->next_thread(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);
+
+ /* next == NULL -> don't take any more steps */
+ if (!next)
+ return false;
+ /* Return false only if swap fails with an error */
+ return (Thread::swap(&system_context, next) == 0);
+}
+
+/** Runs the current execution until threre are no more steps to take. */
+void ModelChecker::finish_execution() {
+ DBG();
+
+ while (take_step());
}