nodestack.o clockvector.o main.o snapshot-interface.o cyclegraph.o \
datarace.o impatomic.o cmodelint.o \
snapshot.o malloc.o mymemory.o common.o mutex.o promise.o conditionvariable.o \
- context.o scanalysis.o
+ context.o scanalysis.o execution.o
CPPFLAGS += -Iinclude -I.
LDFLAGS = -ldl -lrt -rdynamic
--- /dev/null
+#include <stdio.h>
+#include <algorithm>
+#include <mutex>
+#include <new>
+#include <stdarg.h>
+
+#include "execution.h"
+#include "model.h"
+#include "action.h"
+#include "nodestack.h"
+#include "schedule.h"
+#include "snapshot-interface.h"
+#include "common.h"
+#include "clockvector.h"
+#include "cyclegraph.h"
+#include "promise.h"
+#include "datarace.h"
+#include "threads-model.h"
+#include "output.h"
+#include "bugmessage.h"
+
+#define INITIAL_THREAD_ID 0
+
+/**
+ * Structure for holding small ModelChecker members that should be snapshotted
+ */
+struct model_snapshot_members {
+ model_snapshot_members() :
+ /* First thread created will have id INITIAL_THREAD_ID */
+ next_thread_id(INITIAL_THREAD_ID),
+ used_sequence_numbers(0),
+ next_backtrack(NULL),
+ bugs(),
+ stats(),
+ failed_promise(false),
+ too_many_reads(false),
+ no_valid_reads(false),
+ bad_synchronization(false),
+ asserted(false)
+ { }
+
+ ~model_snapshot_members() {
+ for (unsigned int i = 0; i < bugs.size(); i++)
+ delete bugs[i];
+ bugs.clear();
+ }
+
+ unsigned int next_thread_id;
+ modelclock_t used_sequence_numbers;
+ ModelAction *next_backtrack;
+ SnapVector<bug_message *> bugs;
+ struct execution_stats stats;
+ bool failed_promise;
+ bool too_many_reads;
+ bool no_valid_reads;
+ /** @brief Incorrectly-ordered synchronization was made */
+ bool bad_synchronization;
+ bool asserted;
+
+ SNAPSHOTALLOC
+};
+
+/** @brief Constructor */
+ModelExecution::ModelExecution(struct model_params *params, Scheduler *scheduler, NodeStack *node_stack) :
+ params(params),
+ scheduler(scheduler),
+ 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>()),
+ condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
+ obj_thrd_map(new HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4 >()),
+ promises(new SnapVector<Promise *>()),
+ futurevalues(new SnapVector<struct PendingFutureValue>()),
+ pending_rel_seqs(new SnapVector<struct release_seq *>()),
+ thrd_last_action(new SnapVector<ModelAction *>(1)),
+ thrd_last_fence_release(new SnapVector<ModelAction *>()),
+ node_stack(node_stack),
+ priv(new struct model_snapshot_members()),
+ mo_graph(new CycleGraph()),
+ execution_number(1)
+{
+ /* 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 */
+ModelExecution::~ModelExecution()
+{
+ 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 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 thrd_last_fence_release;
+ delete mo_graph;
+ delete priv;
+}
+
+static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
+{
+ action_list_t *tmp = hash->get(ptr);
+ if (tmp == NULL) {
+ tmp = new action_list_t();
+ hash->put(ptr, tmp);
+ }
+ return tmp;
+}
+
+static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
+{
+ SnapVector<action_list_t> *tmp = hash->get(ptr);
+ if (tmp == NULL) {
+ tmp = new SnapVector<action_list_t>();
+ hash->put(ptr, tmp);
+ }
+ return tmp;
+}
+
+action_list_t * ModelExecution::get_actions_on_obj(void * obj, thread_id_t tid) {
+ SnapVector<action_list_t> *wrv=obj_thrd_map->get(obj);
+ if (wrv==NULL)
+ return NULL;
+ unsigned int thread=id_to_int(tid);
+ if (thread < wrv->size())
+ return &(*wrv)[thread];
+ else
+ return NULL;
+}
+
+/** @return a thread ID for a new Thread */
+thread_id_t ModelExecution::get_next_id()
+{
+ return priv->next_thread_id++;
+}
+
+/** @return the number of user threads created during this execution */
+unsigned int ModelExecution::get_num_threads() const
+{
+ return priv->next_thread_id;
+}
+
+/** @return a sequence number for a new ModelAction */
+modelclock_t ModelExecution::get_next_seq_num()
+{
+ return ++priv->used_sequence_numbers;
+}
+
+/**
+ * @brief Should the current action wake up a given thread?
+ *
+ * @param curr The current action
+ * @param thread The thread that we might wake up
+ * @return True, if we should wake up the sleeping thread; false otherwise
+ */
+bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *thread) const
+{
+ const ModelAction *asleep = thread->get_pending();
+ /* Don't allow partial RMW to wake anyone up */
+ if (curr->is_rmwr())
+ return false;
+ /* Synchronizing actions may have been backtracked */
+ if (asleep->could_synchronize_with(curr))
+ return true;
+ /* All acquire/release fences and fence-acquire/store-release */
+ if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
+ return true;
+ /* Fence-release + store can awake load-acquire on the same location */
+ if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
+ ModelAction *fence_release = get_last_fence_release(curr->get_tid());
+ if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
+ return true;
+ }
+ return false;
+}
+
+void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
+{
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ Thread *thr = get_thread(int_to_id(i));
+ if (scheduler->is_sleep_set(thr)) {
+ if (should_wake_up(curr, thr))
+ /* Remove this thread from sleep set */
+ scheduler->remove_sleep(thr);
+ }
+ }
+}
+
+/** @brief Alert the model-checker that an incorrectly-ordered
+ * synchronization was made */
+void ModelExecution::set_bad_synchronization()
+{
+ priv->bad_synchronization = true;
+}
+
+bool ModelExecution::assert_bug(const char *msg)
+{
+ priv->bugs.push_back(new bug_message(msg));
+
+ if (isfeasibleprefix()) {
+ set_assert();
+ return true;
+ }
+ return false;
+}
+
+/** @return True, if any bugs have been reported for this execution */
+bool ModelExecution::have_bug_reports() const
+{
+ return priv->bugs.size() != 0;
+}
+
+SnapVector<bug_message *> * ModelExecution::get_bugs() const
+{
+ return &priv->bugs;
+}
+
+/**
+ * Check whether the current trace has triggered an assertion which should halt
+ * its execution.
+ *
+ * @return True, if the execution should be aborted; false otherwise
+ */
+bool ModelExecution::has_asserted() const
+{
+ return priv->asserted;
+}
+
+/**
+ * Trigger a trace assertion which should cause this execution to be halted.
+ * This can be due to a detected bug or due to an infeasibility that should
+ * halt ASAP.
+ */
+void ModelExecution::set_assert()
+{
+ priv->asserted = true;
+}
+
+/**
+ * Check if we are in a deadlock. Should only be called at the end of an
+ * execution, although it should not give false positives in the middle of an
+ * execution (there should be some ENABLED thread).
+ *
+ * @return True if program is in a deadlock; false otherwise
+ */
+bool ModelExecution::is_deadlocked() const
+{
+ bool blocking_threads = false;
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ thread_id_t tid = int_to_id(i);
+ if (is_enabled(tid))
+ return false;
+ Thread *t = get_thread(tid);
+ if (!t->is_model_thread() && t->get_pending())
+ blocking_threads = true;
+ }
+ return blocking_threads;
+}
+
+/**
+ * Check if this is a complete execution. That is, have all thread completed
+ * execution (rather than exiting because sleep sets have forced a redundant
+ * execution).
+ *
+ * @return True if the execution is complete.
+ */
+bool ModelExecution::is_complete_execution() const
+{
+ for (unsigned int i = 0; i < get_num_threads(); i++)
+ if (is_enabled(int_to_id(i)))
+ return false;
+ return true;
+}
+
+/**
+ * @brief Find the last fence-related backtracking conflict for a ModelAction
+ *
+ * This function performs the search for the most recent conflicting action
+ * against which we should perform backtracking, as affected by fence
+ * operations. This includes pairs of potentially-synchronizing actions which
+ * occur due to fence-acquire or fence-release, and hence should be explored in
+ * the opposite execution order.
+ *
+ * @param act The current action
+ * @return The most recent action which conflicts with act due to fences
+ */
+ModelAction * ModelExecution::get_last_fence_conflict(ModelAction *act) const
+{
+ /* Only perform release/acquire fence backtracking for stores */
+ if (!act->is_write())
+ return NULL;
+
+ /* Find a fence-release (or, act is a release) */
+ ModelAction *last_release;
+ if (act->is_release())
+ last_release = act;
+ else
+ last_release = get_last_fence_release(act->get_tid());
+ if (!last_release)
+ return NULL;
+
+ /* Skip past the release */
+ action_list_t *list = action_trace;
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++)
+ if (*rit == last_release)
+ break;
+ ASSERT(rit != list->rend());
+
+ /* Find a prior:
+ * load-acquire
+ * or
+ * load --sb-> fence-acquire */
+ ModelVector<ModelAction *> acquire_fences(get_num_threads(), NULL);
+ ModelVector<ModelAction *> prior_loads(get_num_threads(), NULL);
+ bool found_acquire_fences = false;
+ for ( ; rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (act->same_thread(prev))
+ continue;
+
+ int tid = id_to_int(prev->get_tid());
+
+ if (prev->is_read() && act->same_var(prev)) {
+ if (prev->is_acquire()) {
+ /* Found most recent load-acquire, don't need
+ * to search for more fences */
+ if (!found_acquire_fences)
+ return NULL;
+ } else {
+ prior_loads[tid] = prev;
+ }
+ }
+ if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
+ found_acquire_fences = true;
+ acquire_fences[tid] = prev;
+ }
+ }
+
+ ModelAction *latest_backtrack = NULL;
+ for (unsigned int i = 0; i < acquire_fences.size(); i++)
+ if (acquire_fences[i] && prior_loads[i])
+ if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
+ latest_backtrack = acquire_fences[i];
+ return latest_backtrack;
+}
+
+/**
+ * @brief Find the last backtracking conflict for a ModelAction
+ *
+ * This function performs the search for the most recent conflicting action
+ * against which we should perform backtracking. This primary includes pairs of
+ * synchronizing actions which should be explored in the opposite execution
+ * order.
+ *
+ * @param act The current action
+ * @return The most recent action which conflicts with act
+ */
+ModelAction * ModelExecution::get_last_conflict(ModelAction *act) const
+{
+ switch (act->get_type()) {
+ /* case ATOMIC_FENCE: fences don't directly cause backtracking */
+ case ATOMIC_READ:
+ case ATOMIC_WRITE:
+ case ATOMIC_RMW: {
+ ModelAction *ret = NULL;
+
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, 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)) {
+ ret = prev;
+ break;
+ }
+ }
+
+ ModelAction *ret2 = get_last_fence_conflict(act);
+ if (!ret2)
+ return ret;
+ if (!ret)
+ return ret2;
+ if (*ret < *ret2)
+ return ret2;
+ return ret;
+ }
+ case ATOMIC_LOCK:
+ case ATOMIC_TRYLOCK: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, 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 = get_safe_ptr_action(obj_map, 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 = get_safe_ptr_action(obj_map, 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;
+ }
+
+ case ATOMIC_NOTIFY_ALL:
+ case ATOMIC_NOTIFY_ONE: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, 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;
+ }
+ 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 ModelExecution::set_backtracking(ModelAction *act)
+{
+ Thread *t = get_thread(act);
+ ModelAction *prev = get_last_conflict(act);
+ if (prev == NULL)
+ return;
+
+ Node *node = prev->get_node()->get_parent();
+
+ /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
+ int low_tid, high_tid;
+ if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
+ low_tid = id_to_int(act->get_tid());
+ high_tid = low_tid + 1;
+ } else {
+ low_tid = 0;
+ high_tid = get_num_threads();
+ }
+
+ for (int i = low_tid; i < high_tid; i++) {
+ thread_id_t tid = int_to_id(i);
+
+ /* Make sure this thread can be enabled here. */
+ if (i >= node->get_num_threads())
+ break;
+
+ /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
+ /* Don't backtrack into a point where the thread is disabled or sleeping. */
+ if (node->enabled_status(tid) != THREAD_ENABLED)
+ continue;
+
+ /* Check if this has been explored already */
+ if (node->has_been_explored(tid))
+ continue;
+
+ /* See if fairness allows */
+ if (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;
+ }
+
+ /* See if CHESS-like yield fairness allows */
+ if (params->yieldon) {
+ 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_over(tid, tother)) {
+ unfair = true;
+ break;
+ }
+ }
+ if (unfair)
+ continue;
+ }
+
+ /* Cache the latest backtracking point */
+ set_latest_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();
+ }
+ }
+}
+
+/**
+ * @brief Cache the a backtracking point as the "most recent", if eligible
+ *
+ * Note that this does not prepare the NodeStack for this backtracking
+ * operation, it only caches the action on a per-execution basis
+ *
+ * @param act The operation at which we should explore a different next action
+ * (i.e., backtracking point)
+ * @return True, if this action is now the most recent backtracking point;
+ * false otherwise
+ */
+bool ModelExecution::set_latest_backtrack(ModelAction *act)
+{
+ if (!priv->next_backtrack || *act > *priv->next_backtrack) {
+ priv->next_backtrack = act;
+ return true;
+ }
+ return false;
+}
+
+/**
+ * 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 * ModelExecution::get_next_backtrack()
+{
+ ModelAction *next = priv->next_backtrack;
+ priv->next_backtrack = NULL;
+ return next;
+}
+
+/**
+ * Processes a read model action.
+ * @param curr is the read model action to process.
+ * @return True if processing this read updates the mo_graph.
+ */
+bool ModelExecution::process_read(ModelAction *curr)
+{
+ Node *node = curr->get_node();
+ while (true) {
+ bool updated = false;
+ switch (node->get_read_from_status()) {
+ case READ_FROM_PAST: {
+ const ModelAction *rf = node->get_read_from_past();
+ ASSERT(rf);
+
+ mo_graph->startChanges();
+
+ ASSERT(!is_infeasible());
+ if (!check_recency(curr, rf)) {
+ if (node->increment_read_from()) {
+ mo_graph->rollbackChanges();
+ continue;
+ } else {
+ priv->too_many_reads = true;
+ }
+ }
+
+ updated = r_modification_order(curr, rf);
+ read_from(curr, rf);
+ mo_graph->commitChanges();
+ mo_check_promises(curr, true);
+ break;
+ }
+ case READ_FROM_PROMISE: {
+ Promise *promise = curr->get_node()->get_read_from_promise();
+ if (promise->add_reader(curr))
+ priv->failed_promise = true;
+ curr->set_read_from_promise(promise);
+ mo_graph->startChanges();
+ if (!check_recency(curr, promise))
+ priv->too_many_reads = true;
+ updated = r_modification_order(curr, promise);
+ mo_graph->commitChanges();
+ break;
+ }
+ case READ_FROM_FUTURE: {
+ /* Read from future value */
+ struct future_value fv = node->get_future_value();
+ Promise *promise = new Promise(curr, fv);
+ curr->set_read_from_promise(promise);
+ promises->push_back(promise);
+ mo_graph->startChanges();
+ updated = r_modification_order(curr, promise);
+ mo_graph->commitChanges();
+ break;
+ }
+ default:
+ ASSERT(false);
+ }
+ get_thread(curr)->set_return_value(curr->get_return_value());
+ return updated;
+ }
+}
+
+/**
+ * Processes a lock, trylock, or unlock model action. @param curr is
+ * the read model action to process.
+ *
+ * The try lock operation checks whether the lock is taken. If not,
+ * it falls to the normal lock operation case. If so, it returns
+ * fail.
+ *
+ * The lock operation has already been checked that it is enabled, so
+ * it just grabs the lock and synchronizes with the previous unlock.
+ *
+ * The unlock operation has to re-enable all of the threads that are
+ * waiting on the lock.
+ *
+ * @return True if synchronization was updated; false otherwise
+ */
+bool ModelExecution::process_mutex(ModelAction *curr)
+{
+ std::mutex *mutex = curr->get_mutex();
+ struct std::mutex_state *state = NULL;
+
+ if (mutex)
+ state = mutex->get_state();
+
+ switch (curr->get_type()) {
+ case ATOMIC_TRYLOCK: {
+ bool success = !state->locked;
+ 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)
+ assert_bug("Lock access before initialization");
+ state->locked = get_thread(curr);
+ ModelAction *unlock = get_last_unlock(curr);
+ //synchronize with the previous unlock statement
+ if (unlock != NULL) {
+ synchronize(unlock, curr);
+ return true;
+ }
+ break;
+ }
+ case ATOMIC_WAIT:
+ case ATOMIC_UNLOCK: {
+ /* wake up the other threads */
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ Thread *t = get_thread(int_to_id(i));
+ Thread *curr_thrd = get_thread(curr);
+ if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
+ scheduler->wake(t);
+ }
+
+ /* unlock the lock - after checking who was waiting on it */
+ state->locked = NULL;
+
+ if (!curr->is_wait())
+ break; /* The rest is only for ATOMIC_WAIT */
+
+ /* Should we go to sleep? (simulate spurious failures) */
+ if (curr->get_node()->get_misc() == 0) {
+ get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
+ /* disable us */
+ scheduler->sleep(get_thread(curr));
+ }
+ break;
+ }
+ case ATOMIC_NOTIFY_ALL: {
+ action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, 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 = get_safe_ptr_action(condvar_waiters_map, 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;
+}
+
+/**
+ * @brief Check if the current pending promises allow a future value to be sent
+ *
+ * If one of the following is true:
+ * (a) there are no pending promises
+ * (b) the reader and writer do not cross any promises
+ * Then, it is safe to pass a future value back now.
+ *
+ * Otherwise, we must save the pending future value until (a) or (b) is true
+ *
+ * @param writer The operation which sends the future value. Must be a write.
+ * @param reader The operation which will observe the value. Must be a read.
+ * @return True if the future value can be sent now; false if it must wait.
+ */
+bool ModelExecution::promises_may_allow(const ModelAction *writer,
+ const ModelAction *reader) const
+{
+ if (promises->empty())
+ return true;
+ for(int i=promises->size()-1;i>=0;i--) {
+ ModelAction *pr=(*promises)[i]->get_reader(0);
+ //reader is after promise...doesn't cross any promise
+ if (*reader > *pr)
+ return true;
+ //writer is after promise, reader before...bad...
+ if (*writer > *pr)
+ return false;
+ }
+ return true;
+}
+
+/**
+ * @brief Add a future value to a reader
+ *
+ * This function performs a few additional checks to ensure that the future
+ * value can be feasibly observed by the reader
+ *
+ * @param writer The operation whose value is sent. Must be a write.
+ * @param reader The read operation which may read the future value. Must be a read.
+ */
+void ModelExecution::add_future_value(const ModelAction *writer, ModelAction *reader)
+{
+ /* Do more ambitious checks now that mo is more complete */
+ if (!mo_may_allow(writer, reader))
+ return;
+
+ Node *node = reader->get_node();
+
+ /* Find an ancestor thread which exists at the time of the reader */
+ Thread *write_thread = get_thread(writer);
+ while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
+ write_thread = write_thread->get_parent();
+
+ struct future_value fv = {
+ writer->get_write_value(),
+ writer->get_seq_number() + params->maxfuturedelay,
+ write_thread->get_id(),
+ };
+ if (node->add_future_value(fv))
+ set_latest_backtrack(reader);
+}
+
+/**
+ * Process a write ModelAction
+ * @param curr The ModelAction to process
+ * @return True if the mo_graph was updated or promises were resolved
+ */
+bool ModelExecution::process_write(ModelAction *curr)
+{
+ /* Readers to which we may send our future value */
+ ModelVector<ModelAction *> send_fv;
+
+ const ModelAction *earliest_promise_reader;
+ bool updated_promises = false;
+
+ bool updated_mod_order = w_modification_order(curr, &send_fv);
+ Promise *promise = pop_promise_to_resolve(curr);
+
+ if (promise) {
+ earliest_promise_reader = promise->get_reader(0);
+ updated_promises = resolve_promise(curr, promise);
+ } else
+ earliest_promise_reader = NULL;
+
+ for (unsigned int i = 0; i < send_fv.size(); i++) {
+ ModelAction *read = send_fv[i];
+
+ /* Don't send future values to reads after the Promise we resolve */
+ if (!earliest_promise_reader || *read < *earliest_promise_reader) {
+ /* Check if future value can be sent immediately */
+ if (promises_may_allow(curr, read)) {
+ add_future_value(curr, read);
+ } else {
+ futurevalues->push_back(PendingFutureValue(curr, read));
+ }
+ }
+ }
+
+ /* Check the pending future values */
+ for (int i = (int)futurevalues->size() - 1; i >= 0; i--) {
+ struct PendingFutureValue pfv = (*futurevalues)[i];
+ if (promises_may_allow(pfv.writer, pfv.reader)) {
+ add_future_value(pfv.writer, pfv.reader);
+ futurevalues->erase(futurevalues->begin() + i);
+ }
+ }
+
+ mo_graph->commitChanges();
+ mo_check_promises(curr, false);
+
+ get_thread(curr)->set_return_value(VALUE_NONE);
+ return updated_mod_order || updated_promises;
+}
+
+/**
+ * Process a fence ModelAction
+ * @param curr The ModelAction to process
+ * @return True if synchronization was updated
+ */
+bool ModelExecution::process_fence(ModelAction *curr)
+{
+ /*
+ * fence-relaxed: no-op
+ * fence-release: only log the occurence (not in this function), for
+ * use in later synchronization
+ * fence-acquire (this function): search for hypothetical release
+ * sequences
+ * fence-seq-cst: MO constraints formed in {r,w}_modification_order
+ */
+ bool updated = false;
+ if (curr->is_acquire()) {
+ action_list_t *list = action_trace;
+ action_list_t::reverse_iterator rit;
+ /* Find X : is_read(X) && X --sb-> curr */
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+ if (act == curr)
+ continue;
+ if (act->get_tid() != curr->get_tid())
+ continue;
+ /* Stop at the beginning of the thread */
+ if (act->is_thread_start())
+ break;
+ /* Stop once we reach a prior fence-acquire */
+ if (act->is_fence() && act->is_acquire())
+ break;
+ if (!act->is_read())
+ continue;
+ /* read-acquire will find its own release sequences */
+ if (act->is_acquire())
+ continue;
+
+ /* Establish hypothetical release sequences */
+ rel_heads_list_t release_heads;
+ get_release_seq_heads(curr, act, &release_heads);
+ for (unsigned int i = 0; i < release_heads.size(); i++)
+ synchronize(release_heads[i], curr);
+ if (release_heads.size() != 0)
+ updated = true;
+ }
+ }
+ return updated;
+}
+
+/**
+ * @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 ModelExecution::process_thread_action(ModelAction *curr)
+{
+ bool updated = false;
+
+ switch (curr->get_type()) {
+ case THREAD_CREATE: {
+ thrd_t *thrd = (thrd_t *)curr->get_location();
+ struct thread_params *params = (struct thread_params *)curr->get_value();
+ Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
+ add_thread(th);
+ th->set_creation(curr);
+ /* Promises can be satisfied by children */
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->thread_is_available(curr->get_tid()))
+ promise->add_thread(th->get_id());
+ }
+ break;
+ }
+ case THREAD_JOIN: {
+ Thread *blocking = curr->get_thread_operand();
+ ModelAction *act = get_last_action(blocking->get_id());
+ synchronize(act, curr);
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_FINISH: {
+ Thread *th = get_thread(curr);
+ /* Wake up any joining threads */
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ Thread *waiting = get_thread(int_to_id(i));
+ if (waiting->waiting_on() == th &&
+ waiting->get_pending()->is_thread_join())
+ scheduler->wake(waiting);
+ }
+ th->complete();
+ /* Completed thread can't satisfy promises */
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->thread_is_available(th->get_id()))
+ if (promise->eliminate_thread(th->get_id()))
+ priv->failed_promise = true;
+ }
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_START: {
+ check_promises(curr->get_tid(), NULL, curr->get_cv());
+ break;
+ }
+ default:
+ break;
+ }
+
+ return updated;
+}
+
+/**
+ * @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 ModelExecution::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 (!synchronize(release, acquire))
+ 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)) {
+ synchronize(acquire, propagate);
+ /* Re-check 'propagate' for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(propagate));
+ }
+ }
+ } else {
+ /* Break release sequence with new edges:
+ * release --mo--> write --mo--> rf */
+ mo_graph->addEdge(release, write);
+ mo_graph->addEdge(write, rf);
+ }
+
+ /* See if we have realized a data race */
+ checkDataRaces();
+}
+
+/**
+ * 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, with a different
+ * action "returned" its place (pass-by-reference)
+ * @return True if curr is a newly-explored action; false otherwise
+ */
+bool ModelExecution::initialize_curr_action(ModelAction **curr)
+{
+ ModelAction *newcurr;
+
+ if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
+ newcurr = process_rmw(*curr);
+ delete *curr;
+
+ if (newcurr->is_rmw())
+ compute_promises(newcurr);
+
+ *curr = newcurr;
+ return false;
+ }
+
+ (*curr)->set_seq_number(get_next_seq_num());
+
+ newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
+ 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()));
+
+ *curr = newcurr;
+ return false; /* Action was explored previously */
+ } else {
+ newcurr = *curr;
+
+ /* Always compute new clock vector */
+ newcurr->create_cv(get_parent_action(newcurr->get_tid()));
+
+ /* Assign most recent release fence */
+ newcurr->set_last_fence_release(get_last_fence_release(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(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
+ }
+ return true; /* This was a new ModelAction */
+ }
+}
+
+/**
+ * @brief Establish reads-from relation between two actions
+ *
+ * Perform basic operations involved with establishing a concrete rf relation,
+ * including setting the ModelAction data and checking for release sequences.
+ *
+ * @param act The action that is reading (must be a read)
+ * @param rf The action from which we are reading (must be a write)
+ *
+ * @return True if this read established synchronization
+ */
+bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
+{
+ ASSERT(rf);
+ ASSERT(rf->is_write());
+
+ act->set_read_from(rf);
+ if (act->is_acquire()) {
+ rel_heads_list_t release_heads;
+ get_release_seq_heads(act, act, &release_heads);
+ int num_heads = release_heads.size();
+ for (unsigned int i = 0; i < release_heads.size(); i++)
+ if (!synchronize(release_heads[i], act))
+ num_heads--;
+ return num_heads > 0;
+ }
+ return false;
+}
+
+/**
+ * @brief Synchronizes two actions
+ *
+ * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
+ * This function performs the synchronization as well as providing other hooks
+ * for other checks along with synchronization.
+ *
+ * @param first The left-hand side of the synchronizes-with relation
+ * @param second The right-hand side of the synchronizes-with relation
+ * @return True if the synchronization was successful (i.e., was consistent
+ * with the execution order); false otherwise
+ */
+bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
+{
+ if (*second < *first) {
+ set_bad_synchronization();
+ return false;
+ }
+ check_promises(first->get_tid(), second->get_cv(), first->get_cv());
+ return second->synchronize_with(first);
+}
+
+/**
+ * Check promises and eliminate potentially-satisfying threads when a thread is
+ * blocked (e.g., join, lock). A thread which is waiting on another thread can
+ * no longer satisfy a promise generated from that thread.
+ *
+ * @param blocker The thread on which a thread is waiting
+ * @param waiting The waiting thread
+ */
+void ModelExecution::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (!promise->thread_is_available(waiting->get_id()))
+ continue;
+ for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
+ ModelAction *reader = promise->get_reader(j);
+ if (reader->get_tid() != blocker->get_id())
+ continue;
+ if (promise->eliminate_thread(waiting->get_id())) {
+ /* Promise has failed */
+ priv->failed_promise = true;
+ } else {
+ /* Only eliminate the 'waiting' thread once */
+ return;
+ }
+ }
+ }
+}
+
+/**
+ * @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 ModelExecution::check_action_enabled(ModelAction *curr) {
+ if (curr->is_lock()) {
+ std::mutex *lock = curr->get_mutex();
+ struct std::mutex_state *state = lock->get_state();
+ if (state->locked)
+ return false;
+ } else if (curr->is_thread_join()) {
+ Thread *blocking = curr->get_thread_operand();
+ if (!blocking->is_complete()) {
+ thread_blocking_check_promises(blocking, get_thread(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 ModelAction that is actually executed; may be different than
+ * curr; may be NULL, if the current action is not enabled to run
+ */
+ModelAction * ModelExecution::check_current_action(ModelAction *curr)
+{
+ ASSERT(curr);
+ bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
+ bool newly_explored = initialize_curr_action(&curr);
+
+ DBG();
+
+ wake_up_sleeping_actions(curr);
+
+ /* Compute fairness information for CHESS yield algorithm */
+ if (params->yieldon) {
+ curr->get_node()->update_yield(scheduler);
+ }
+
+ /* Add the action to lists before any other model-checking tasks */
+ if (!second_part_of_rmw)
+ add_action_to_lists(curr);
+
+ /* Build may_read_from set for newly-created actions */
+ if (newly_explored && curr->is_read())
+ build_may_read_from(curr);
+
+ /* Initialize work_queue with the "current action" work */
+ work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
+ while (!work_queue.empty() && !has_asserted()) {
+ 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() && !second_part_of_rmw && process_read(act))
+ update = true;
+
+ if (act->is_write() && process_write(act))
+ update = true;
+
+ if (act->is_fence() && process_fence(act))
+ update_all = 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();
+ const Promise *promise = act->get_reads_from_promise();
+ if (rf) {
+ if (r_modification_order(act, rf))
+ updated = true;
+ } else if (promise) {
+ if (r_modification_order(act, promise))
+ updated = true;
+ }
+ }
+ if (act->is_write()) {
+ if (w_modification_order(act, NULL))
+ 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 curr;
+}
+
+void ModelExecution::check_curr_backtracking(ModelAction *curr)
+{
+ Node *currnode = curr->get_node();
+ Node *parnode = currnode->get_parent();
+
+ if ((parnode && !parnode->backtrack_empty()) ||
+ !currnode->misc_empty() ||
+ !currnode->read_from_empty() ||
+ !currnode->promise_empty() ||
+ !currnode->relseq_break_empty()) {
+ set_latest_backtrack(curr);
+ }
+}
+
+bool ModelExecution::promises_expired() const
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->get_expiration() < priv->used_sequence_numbers)
+ return true;
+ }
+ return false;
+}
+
+/**
+ * This is the strongest feasibility check available.
+ * @return whether the current trace (partial or complete) must be a prefix of
+ * a feasible trace.
+ */
+bool ModelExecution::isfeasibleprefix() const
+{
+ return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
+}
+
+/**
+ * Print disagnostic information about an infeasible execution
+ * @param prefix A string to prefix the output with; if NULL, then a default
+ * message prefix will be provided
+ */
+void ModelExecution::print_infeasibility(const char *prefix) const
+{
+ char buf[100];
+ char *ptr = buf;
+ if (mo_graph->checkForCycles())
+ ptr += sprintf(ptr, "[mo cycle]");
+ if (priv->failed_promise)
+ ptr += sprintf(ptr, "[failed promise]");
+ if (priv->too_many_reads)
+ ptr += sprintf(ptr, "[too many reads]");
+ if (priv->no_valid_reads)
+ ptr += sprintf(ptr, "[no valid reads-from]");
+ if (priv->bad_synchronization)
+ ptr += sprintf(ptr, "[bad sw ordering]");
+ if (promises_expired())
+ ptr += sprintf(ptr, "[promise expired]");
+ if (promises->size() != 0)
+ ptr += sprintf(ptr, "[unresolved promise]");
+ if (ptr != buf)
+ model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
+}
+
+/**
+ * Returns whether the current completed trace is feasible, except for pending
+ * release sequences.
+ */
+bool ModelExecution::is_feasible_prefix_ignore_relseq() const
+{
+ return !is_infeasible() && promises->size() == 0;
+}
+
+/**
+ * Check if the current partial trace is infeasible. Does not check any
+ * end-of-execution flags, which might rule out the execution. Thus, this is
+ * useful only for ruling an execution as infeasible.
+ * @return whether the current partial trace is infeasible.
+ */
+bool ModelExecution::is_infeasible() const
+{
+ return mo_graph->checkForCycles() ||
+ priv->no_valid_reads ||
+ priv->failed_promise ||
+ priv->too_many_reads ||
+ priv->bad_synchronization ||
+ promises_expired();
+}
+
+/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
+ModelAction * ModelExecution::process_rmw(ModelAction *act) {
+ ModelAction *lastread = get_last_action(act->get_tid());
+ lastread->process_rmw(act);
+ if (act->is_rmw()) {
+ if (lastread->get_reads_from())
+ mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
+ else
+ mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
+ mo_graph->commitChanges();
+ }
+ return lastread;
+}
+
+/**
+ * A helper function for ModelExecution::check_recency, to check if the current
+ * thread is able to read from a different write/promise for 'params.maxreads'
+ * number of steps and if that write/promise should become visible (i.e., is
+ * ordered later in the modification order). This helps model memory liveness.
+ *
+ * @param curr The current action. Must be a read.
+ * @param rf The write/promise from which we plan to read
+ * @param other_rf The write/promise from which we may read
+ * @return True if we were able to read from other_rf for params.maxreads steps
+ */
+template <typename T, typename U>
+bool ModelExecution::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
+{
+ /* Need a different write/promise */
+ if (other_rf->equals(rf))
+ return false;
+
+ /* Only look for "newer" writes/promises */
+ if (!mo_graph->checkReachable(rf, other_rf))
+ return false;
+
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
+ action_list_t::reverse_iterator rit = list->rbegin();
+ ASSERT((*rit) == curr);
+ /* Skip past curr */
+ rit++;
+
+ /* Does this write/promise work for everyone? */
+ for (int i = 0; i < params->maxreads; i++, rit++) {
+ ModelAction *act = *rit;
+ if (!act->may_read_from(other_rf))
+ return false;
+ }
+ return true;
+}
+
+/**
+ * Checks whether a thread has read from the same write or Promise for too many
+ * times without seeing the effects of a later write/Promise.
+ *
+ * Basic idea:
+ * 1) there must a different write/promise that we could read from,
+ * 2) we must have read from the same write/promise in excess of maxreads times,
+ * 3) that other write/promise must have been in the reads_from set for maxreads times, and
+ * 4) that other write/promise must be mod-ordered after the write/promise we are reading.
+ *
+ * If so, we decide that the execution is no longer feasible.
+ *
+ * @param curr The current action. Must be a read.
+ * @param rf The ModelAction/Promise from which we might read.
+ * @return True if the read should succeed; false otherwise
+ */
+template <typename T>
+bool ModelExecution::check_recency(ModelAction *curr, const T *rf) const
+{
+ if (!params->maxreads)
+ return true;
+
+ //NOTE: Next check is just optimization, not really necessary....
+ if (curr->get_node()->get_read_from_past_size() +
+ curr->get_node()->get_read_from_promise_size() <= 1)
+ return true;
+
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ int tid = id_to_int(curr->get_tid());
+ ASSERT(tid < (int)thrd_lists->size());
+ action_list_t *list = &(*thrd_lists)[tid];
+ action_list_t::reverse_iterator rit = list->rbegin();
+ ASSERT((*rit) == curr);
+ /* Skip past curr */
+ rit++;
+
+ action_list_t::reverse_iterator ritcopy = rit;
+ /* See if we have enough reads from the same value */
+ for (int count = 0; count < params->maxreads; ritcopy++, count++) {
+ if (ritcopy == list->rend())
+ return true;
+ ModelAction *act = *ritcopy;
+ if (!act->is_read())
+ return true;
+ if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
+ return true;
+ if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
+ return true;
+ if (act->get_node()->get_read_from_past_size() +
+ act->get_node()->get_read_from_promise_size() <= 1)
+ return true;
+ }
+ for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
+ const ModelAction *write = curr->get_node()->get_read_from_past(i);
+ if (should_read_instead(curr, rf, write))
+ return false; /* liveness failure */
+ }
+ for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
+ const Promise *promise = curr->get_node()->get_read_from_promise(i);
+ if (should_read_instead(curr, rf, promise))
+ return false; /* liveness failure */
+ }
+ return true;
+}
+
+/**
+ * @brief 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 last action that happened before our read. Two cases:
+ *
+ * -# The action is a write: that write must either occur before
+ * the write we read from or be the write we read from.
+ * -# 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 ModelAction or Promise that curr reads from. Must be a write.
+ * @return True if modification order edges were added; false otherwise
+ */
+template <typename rf_type>
+bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
+{
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ unsigned int i;
+ bool added = false;
+ ASSERT(curr->is_read());
+
+ /* Last SC fence in the current thread */
+ ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
+ ModelAction *last_sc_write = NULL;
+ if (curr->is_seqcst())
+ last_sc_write = get_last_seq_cst_write(curr);
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Last SC fence in thread i */
+ ModelAction *last_sc_fence_thread_local = NULL;
+ if (int_to_id((int)i) != curr->get_tid())
+ last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
+
+ /* Last SC fence in thread i, before last SC fence in current thread */
+ ModelAction *last_sc_fence_thread_before = NULL;
+ if (last_sc_fence_local)
+ last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
+
+ /* 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;
+
+ /* Skip curr */
+ if (act == curr)
+ continue;
+ /* Don't want to add reflexive edges on 'rf' */
+ if (act->equals(rf)) {
+ if (act->happens_before(curr))
+ break;
+ else
+ continue;
+ }
+
+ if (act->is_write()) {
+ /* C++, Section 29.3 statement 5 */
+ if (curr->is_seqcst() && last_sc_fence_thread_local &&
+ *act < *last_sc_fence_thread_local) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+ /* C++, Section 29.3 statement 4 */
+ else if (act->is_seqcst() && last_sc_fence_local &&
+ *act < *last_sc_fence_local) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+ /* C++, Section 29.3 statement 6 */
+ else if (last_sc_fence_thread_before &&
+ *act < *last_sc_fence_thread_before) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+ }
+
+ /* C++, Section 29.3 statement 3 (second subpoint) */
+ if (curr->is_seqcst() && last_sc_write && act == last_sc_write) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+
+ /*
+ * Include at most one act per-thread that "happens
+ * before" curr
+ */
+ if (act->happens_before(curr)) {
+ if (act->is_write()) {
+ added = mo_graph->addEdge(act, rf) || added;
+ } else {
+ const ModelAction *prevrf = act->get_reads_from();
+ const Promise *prevrf_promise = act->get_reads_from_promise();
+ if (prevrf) {
+ if (!prevrf->equals(rf))
+ added = mo_graph->addEdge(prevrf, rf) || added;
+ } else if (!prevrf_promise->equals(rf)) {
+ added = mo_graph->addEdge(prevrf_promise, rf) || added;
+ }
+ }
+ break;
+ }
+ }
+ }
+
+ /*
+ * All compatible, thread-exclusive promises must be ordered after any
+ * concrete loads from the same thread
+ */
+ for (unsigned int i = 0; i < promises->size(); i++)
+ if ((*promises)[i]->is_compatible_exclusive(curr))
+ added = mo_graph->addEdge(rf, (*promises)[i]) || added;
+
+ return added;
+}
+
+/**
+ * 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.
+ * @param send_fv A vector for stashing reads to which we may pass our future
+ * value. If NULL, then don't record any future values.
+ * @return True if modification order edges were added; false otherwise
+ */
+bool ModelExecution::w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv)
+{
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, 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_write(curr);
+ if (last_seq_cst != NULL) {
+ added = mo_graph->addEdge(last_seq_cst, curr) || added;
+ }
+ }
+
+ /* Last SC fence in the current thread */
+ ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Last SC fence in thread i, before last SC fence in current thread */
+ ModelAction *last_sc_fence_thread_before = NULL;
+ if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
+ last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
+
+ /* 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;
+ 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;
+ }
+
+ /* C++, Section 29.3 statement 7 */
+ if (last_sc_fence_thread_before && act->is_write() &&
+ *act < *last_sc_fence_thread_before) {
+ added = mo_graph->addEdge(act, curr) || added;
+ break;
+ }
+
+ /*
+ * Include at most one act per-thread that "happens
+ * before" curr
+ */
+ if (act->happens_before(curr)) {
+ /*
+ * 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())
+ added = mo_graph->addEdge(act, curr) || added;
+ else if (act->is_read()) {
+ //if previous read accessed a null, just keep going
+ if (act->get_reads_from() == NULL)
+ continue;
+ added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
+ }
+ break;
+ } 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
+ (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. Note that
+ these checks are overly conservative at this point, we'll
+ do more checks before actually removing the
+ pendingfuturevalue.
+
+ */
+ if (send_fv && thin_air_constraint_may_allow(curr, act)) {
+ if (!is_infeasible())
+ send_fv->push_back(act);
+ else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
+ add_future_value(curr, act);
+ }
+ }
+ }
+ }
+
+ /*
+ * All compatible, thread-exclusive promises must be ordered after any
+ * concrete stores to the same thread, or else they can be merged with
+ * this store later
+ */
+ for (unsigned int i = 0; i < promises->size(); i++)
+ if ((*promises)[i]->is_compatible_exclusive(curr))
+ added = mo_graph->addEdge(curr, (*promises)[i]) || added;
+
+ 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 ModelExecution::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader) const
+{
+ 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 the following constraint (others
+ * require compiler support):
+ *
+ * If X --hb-> Y --mo-> Z, then X should not read from Z.
+ */
+bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
+{
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
+ unsigned int i;
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ const ModelAction *write_after_read = NULL;
+
+ /* 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;
+
+ /* Don't disallow due to act == reader */
+ if (!reader->happens_before(act) || reader == act)
+ break;
+ else if (act->is_write())
+ write_after_read = act;
+ else if (act->is_read() && act->get_reads_from() != NULL)
+ write_after_read = act->get_reads_from();
+ }
+
+ if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
+ return false;
+ }
+ return true;
+}
+
+/**
+ * Finds the head(s) of the release sequence(s) containing a given ModelAction.
+ * The ModelAction under consideration is expected to be taking part in
+ * 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 ModelExecution is certain that release_heads is complete;
+ * false otherwise
+ */
+bool ModelExecution::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;
+
+ for ( ; rf != NULL; rf = rf->get_reads_from()) {
+ ASSERT(rf->is_write());
+
+ if (rf->is_release())
+ release_heads->push_back(rf);
+ else if (rf->get_last_fence_release())
+ release_heads->push_back(rf->get_last_fence_release());
+ 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 */
+ };
+ 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 for fence-release in the same thread (29.8, stmt. 3)
+ * - check modification order for contiguous subsequence
+ * -> rf must be same thread as release */
+
+ const ModelAction *fence_release = rf->get_last_fence_release();
+ /* Synchronize with a fence-release unconditionally; we don't need to
+ * find any more "contiguous subsequence..." for it */
+ if (fence_release)
+ release_heads->push_back(fence_release);
+
+ int tid = id_to_int(rf->get_tid());
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, 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,fence}-release */
+ for (; rit != list->rend(); rit++) {
+ if (fence_release && *(*rit) < *fence_release)
+ break;
+ if ((*rit)->is_release())
+ break;
+ }
+ if (rit == list->rend()) {
+ /* No write-release in this thread */
+ return true; /* complete */
+ } else if (fence_release && *(*rit) < *fence_release) {
+ /* The fence-release is more recent (and so, "stronger") than
+ * the most recent write-release */
+ return true; /* complete */
+ } /* else, need to establish contiguous release sequence */
+ 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)) ||
+ !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;
+}
+
+/**
+ * An 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 ModelExecution so that it will handle
+ * the release sequence at a later time, causing @a acquire to update its
+ * synchronization at some later point in execution.
+ *
+ * @param acquire The 'acquire' action that may synchronize with a release
+ * sequence
+ * @param read The read action that may read from a release sequence; this may
+ * be the same as acquire, or else an earlier action in the same thread (i.e.,
+ * when 'acquire' is a fence-acquire)
+ * @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 ModelExecution::release_seq_heads
+ */
+void ModelExecution::get_release_seq_heads(ModelAction *acquire,
+ ModelAction *read, rel_heads_list_t *release_heads)
+{
+ const ModelAction *rf = read->get_reads_from();
+ struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
+ sequence->acquire = acquire;
+ sequence->read = read;
+
+ 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 ModelExecution::resolve_release_sequences(void *location, work_queue_t *work_queue)
+{
+ bool updated = false;
+ SnapVector<struct release_seq *>::iterator it = pending_rel_seqs->begin();
+ while (it != pending_rel_seqs->end()) {
+ struct release_seq *pending = *it;
+ ModelAction *acquire = pending->acquire;
+ const ModelAction *read = pending->read;
+
+ /* Only resolve sequences on the given location, if provided */
+ if (location && read->get_location() != location) {
+ it++;
+ continue;
+ }
+
+ const ModelAction *rf = read->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 (!acquire->has_synchronized_with(release_heads[i]))
+ if (synchronize(release_heads[i], acquire))
+ updated = true;
+
+ if (updated) {
+ /* Re-check all pending release sequences */
+ work_queue->push_back(CheckRelSeqWorkEntry(NULL));
+ /* Re-check read-acquire for mo_graph edges */
+ if (acquire->is_read())
+ 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)) {
+ synchronize(acquire, propagate);
+ /* 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.
+ checkDataRaces();
+
+ return updated;
+}
+
+/**
+ * Performs various bookkeeping operations for the current ModelAction. For
+ * instance, adds action to the per-object, per-thread action vector and to the
+ * action trace list of all thread actions.
+ *
+ * @param act is the ModelAction to add.
+ */
+void ModelExecution::add_action_to_lists(ModelAction *act)
+{
+ int tid = id_to_int(act->get_tid());
+ ModelAction *uninit = NULL;
+ int uninit_id = -1;
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
+ if (list->empty() && act->is_atomic_var()) {
+ uninit = get_uninitialized_action(act);
+ uninit_id = id_to_int(uninit->get_tid());
+ list->push_front(uninit);
+ }
+ list->push_back(act);
+
+ action_trace->push_back(act);
+ if (uninit)
+ action_trace->push_front(uninit);
+
+ SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
+ if (tid >= (int)vec->size())
+ vec->resize(priv->next_thread_id);
+ (*vec)[tid].push_back(act);
+ if (uninit)
+ (*vec)[uninit_id].push_front(uninit);
+
+ if ((int)thrd_last_action->size() <= tid)
+ thrd_last_action->resize(get_num_threads());
+ (*thrd_last_action)[tid] = act;
+ if (uninit)
+ (*thrd_last_action)[uninit_id] = uninit;
+
+ if (act->is_fence() && act->is_release()) {
+ if ((int)thrd_last_fence_release->size() <= tid)
+ thrd_last_fence_release->resize(get_num_threads());
+ (*thrd_last_fence_release)[tid] = act;
+ }
+
+ if (act->is_wait()) {
+ void *mutex_loc = (void *) act->get_value();
+ get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
+
+ SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
+ if (tid >= (int)vec->size())
+ vec->resize(priv->next_thread_id);
+ (*vec)[tid].push_back(act);
+ }
+}
+
+/**
+ * @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 * ModelExecution::get_last_action(thread_id_t tid) const
+{
+ int threadid = id_to_int(tid);
+ if (threadid < (int)thrd_last_action->size())
+ return (*thrd_last_action)[id_to_int(tid)];
+ else
+ return NULL;
+}
+
+/**
+ * @brief Get the last fence release performed by a particular Thread
+ * @param tid The thread ID of the Thread in question
+ * @return The last fence release in the thread, if one exists; NULL otherwise
+ */
+ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
+{
+ int threadid = id_to_int(tid);
+ if (threadid < (int)thrd_last_fence_release->size())
+ return (*thrd_last_fence_release)[id_to_int(tid)];
+ else
+ return NULL;
+}
+
+/**
+ * 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 * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
+{
+ void *location = curr->get_location();
+ action_list_t *list = get_safe_ptr_action(obj_map, location);
+ /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); (*rit) != curr; rit++)
+ ;
+ rit++; /* Skip past curr */
+ for ( ; rit != list->rend(); rit++)
+ if ((*rit)->is_write() && (*rit)->is_seqcst())
+ return *rit;
+ return NULL;
+}
+
+/**
+ * Gets the last memory_order_seq_cst fence (in the total global sequence)
+ * performed in a particular thread, prior to a particular fence.
+ * @param tid The ID of the thread to check
+ * @param before_fence The fence from which to begin the search; if NULL, then
+ * search for the most recent fence in the thread.
+ * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
+ */
+ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
+{
+ /* All fences should have NULL location */
+ action_list_t *list = get_safe_ptr_action(obj_map, NULL);
+ action_list_t::reverse_iterator rit = list->rbegin();
+
+ if (before_fence) {
+ for (; rit != list->rend(); rit++)
+ if (*rit == before_fence)
+ break;
+
+ ASSERT(*rit == before_fence);
+ rit++;
+ }
+
+ for (; rit != list->rend(); rit++)
+ if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
+ 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 * ModelExecution::get_last_unlock(ModelAction *curr) const
+{
+ void *location = curr->get_location();
+ action_list_t *list = get_safe_ptr_action(obj_map, 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;
+}
+
+ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
+{
+ ModelAction *parent = get_last_action(tid);
+ if (!parent)
+ parent = get_thread(tid)->get_creation();
+ return parent;
+}
+
+/**
+ * Returns the clock vector for a given thread.
+ * @param tid The thread whose clock vector we want
+ * @return Desired clock vector
+ */
+ClockVector * ModelExecution::get_cv(thread_id_t tid) const
+{
+ return get_parent_action(tid)->get_cv();
+}
+
+/**
+ * @brief Find the promise (if any) to resolve for the current action and
+ * remove it from the pending promise vector
+ * @param curr The current ModelAction. Should be a write.
+ * @return The Promise to resolve, if any; otherwise NULL
+ */
+Promise * ModelExecution::pop_promise_to_resolve(const ModelAction *curr)
+{
+ for (unsigned int i = 0; i < promises->size(); i++)
+ if (curr->get_node()->get_promise(i)) {
+ Promise *ret = (*promises)[i];
+ promises->erase(promises->begin() + i);
+ return ret;
+ }
+ return NULL;
+}
+
+/**
+ * Resolve a Promise with a current write.
+ * @param write The ModelAction that is fulfilling Promises
+ * @param promise The Promise to resolve
+ * @return True if the Promise was successfully resolved; false otherwise
+ */
+bool ModelExecution::resolve_promise(ModelAction *write, Promise *promise)
+{
+ ModelVector<ModelAction *> actions_to_check;
+
+ for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
+ ModelAction *read = promise->get_reader(i);
+ read_from(read, write);
+ actions_to_check.push_back(read);
+ }
+ /* Make sure the promise's value matches the write's value */
+ ASSERT(promise->is_compatible(write) && promise->same_value(write));
+ if (!mo_graph->resolvePromise(promise, write))
+ priv->failed_promise = true;
+
+ /**
+ * @todo It is possible to end up in an inconsistent state, where a
+ * "resolved" promise may still be referenced if
+ * CycleGraph::resolvePromise() failed, so don't delete 'promise'.
+ *
+ * Note that the inconsistency only matters when dumping mo_graph to
+ * file.
+ *
+ * delete promise;
+ */
+
+ //Check whether reading these writes has made threads unable to
+ //resolve promises
+ for (unsigned int i = 0; i < actions_to_check.size(); i++) {
+ ModelAction *read = actions_to_check[i];
+ mo_check_promises(read, true);
+ }
+
+ return true;
+}
+
+/**
+ * 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
+ * ModelExecution.
+ * @param curr The ModelAction that may satisfy promises
+ */
+void ModelExecution::compute_promises(ModelAction *curr)
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (!promise->is_compatible(curr) || !promise->same_value(curr))
+ continue;
+
+ bool satisfy = true;
+ for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
+ const ModelAction *act = promise->get_reader(j);
+ if (act->happens_before(curr) ||
+ act->could_synchronize_with(curr)) {
+ satisfy = false;
+ break;
+ }
+ }
+ if (satisfy)
+ curr->get_node()->set_promise(i);
+ }
+}
+
+/** Checks promises in response to change in ClockVector Threads. */
+void ModelExecution::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];
+ if (!promise->thread_is_available(tid))
+ continue;
+ for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
+ const ModelAction *act = promise->get_reader(j);
+ if ((!old_cv || !old_cv->synchronized_since(act)) &&
+ merge_cv->synchronized_since(act)) {
+ if (promise->eliminate_thread(tid)) {
+ /* Promise has failed */
+ priv->failed_promise = true;
+ return;
+ }
+ }
+ }
+ }
+}
+
+void ModelExecution::check_promises_thread_disabled()
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->has_failed()) {
+ priv->failed_promise = true;
+ return;
+ }
+ }
+}
+
+/**
+ * @brief Checks promises in response to addition to modification order for
+ * threads.
+ *
+ * We test whether threads are still available for satisfying promises after an
+ * addition to our modification order constraints. Those that are unavailable
+ * are "eliminated". Once all threads are eliminated from satisfying a promise,
+ * that promise has failed.
+ *
+ * @param act The ModelAction which updated the modification order
+ * @param is_read_check Should be true if act is a read and we must check for
+ * updates to the store from which it read (there is a distinction here for
+ * RMW's, which are both a load and a store)
+ */
+void ModelExecution::mo_check_promises(const ModelAction *act, bool is_read_check)
+{
+ const ModelAction *write = is_read_check ? act->get_reads_from() : act;
+
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+
+ // Is this promise on the same location?
+ if (!promise->same_location(write))
+ continue;
+
+ for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
+ const ModelAction *pread = promise->get_reader(j);
+ if (!pread->happens_before(act))
+ continue;
+ if (mo_graph->checkPromise(write, promise)) {
+ priv->failed_promise = true;
+ return;
+ }
+ break;
+ }
+
+ // Don't do any lookups twice for the same thread
+ if (!promise->thread_is_available(act->get_tid()))
+ continue;
+
+ if (mo_graph->checkReachable(promise, write)) {
+ if (mo_graph->checkPromise(write, promise)) {
+ priv->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 ModelExecution::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, as well as any previously-observed future values that must still be valid.
+ *
+ * @param curr is the current ModelAction that we are exploring; it must be a
+ * 'read' operation.
+ */
+void ModelExecution::build_may_read_from(ModelAction *curr)
+{
+ SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ unsigned int i;
+ ASSERT(curr->is_read());
+
+ ModelAction *last_sc_write = NULL;
+
+ if (curr->is_seqcst())
+ last_sc_write = get_last_seq_cst_write(curr);
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Iterate over actions in thread, starting from most recent */
+ action_list_t *list = &(*thrd_lists)[i];
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+
+ /* Only consider 'write' actions */
+ if (!act->is_write() || act == curr)
+ continue;
+
+ /* Don't consider more than one seq_cst write if we are a seq_cst read. */
+ bool allow_read = true;
+
+ if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
+ allow_read = false;
+ else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
+ allow_read = false;
+
+ if (allow_read) {
+ /* Only add feasible reads */
+ mo_graph->startChanges();
+ r_modification_order(curr, act);
+ if (!is_infeasible())
+ curr->get_node()->add_read_from_past(act);
+ mo_graph->rollbackChanges();
+ }
+
+ /* Include at most one act per-thread that "happens before" curr */
+ if (act->happens_before(curr))
+ break;
+ }
+ }
+
+ /* Inherit existing, promised future values */
+ for (i = 0; i < promises->size(); i++) {
+ const Promise *promise = (*promises)[i];
+ const ModelAction *promise_read = promise->get_reader(0);
+ if (promise_read->same_var(curr)) {
+ /* Only add feasible future-values */
+ mo_graph->startChanges();
+ r_modification_order(curr, promise);
+ if (!is_infeasible())
+ curr->get_node()->add_read_from_promise(promise_read);
+ mo_graph->rollbackChanges();
+ }
+ }
+
+ /* We may find no valid may-read-from only if the execution is doomed */
+ if (!curr->get_node()->read_from_size()) {
+ priv->no_valid_reads = true;
+ set_assert();
+ }
+
+ if (DBG_ENABLED()) {
+ model_print("Reached read action:\n");
+ curr->print();
+ model_print("Printing read_from_past\n");
+ curr->get_node()->print_read_from_past();
+ model_print("End printing read_from_past\n");
+ }
+}
+
+bool ModelExecution::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
+{
+ for ( ; write != NULL; write = write->get_reads_from()) {
+ /* UNINIT actions don't have a Node, and they never sleep */
+ if (write->is_uninitialized())
+ return true;
+ Node *prevnode = write->get_node()->get_parent();
+
+ bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
+ if (write->is_release() && thread_sleep)
+ return true;
+ if (!write->is_rmw())
+ return false;
+ }
+ return true;
+}
+
+/**
+ * @brief Get an action representing an uninitialized atomic
+ *
+ * This function may create a new one or try to retrieve one from the NodeStack
+ *
+ * @param curr The current action, which prompts the creation of an UNINIT action
+ * @return A pointer to the UNINIT ModelAction
+ */
+ModelAction * ModelExecution::get_uninitialized_action(const ModelAction *curr) const
+{
+ Node *node = curr->get_node();
+ ModelAction *act = node->get_uninit_action();
+ if (!act) {
+ act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
+ node->set_uninit_action(act);
+ }
+ act->create_cv(NULL);
+ return act;
+}
+
+static void print_list(action_list_t *list)
+{
+ action_list_t::iterator it;
+
+ model_print("---------------------------------------------------------------------\n");
+
+ unsigned int hash = 0;
+
+ for (it = list->begin(); it != list->end(); it++) {
+ const ModelAction *act = *it;
+ if (act->get_seq_number() > 0)
+ act->print();
+ hash = hash^(hash<<3)^((*it)->hash());
+ }
+ model_print("HASH %u\n", hash);
+ model_print("---------------------------------------------------------------------\n");
+}
+
+#if SUPPORT_MOD_ORDER_DUMP
+void ModelExecution::dumpGraph(char *filename) const
+{
+ 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 *act = *it;
+ if (act->is_read()) {
+ mo_graph->dot_print_node(file, act);
+ if (act->get_reads_from())
+ mo_graph->dot_print_edge(file,
+ act->get_reads_from(),
+ act,
+ "label=\"rf\", color=red, weight=2");
+ else
+ mo_graph->dot_print_edge(file,
+ act->get_reads_from_promise(),
+ act,
+ "label=\"rf\", color=red");
+ }
+ if (thread_array[act->get_tid()]) {
+ mo_graph->dot_print_edge(file,
+ thread_array[id_to_int(act->get_tid())],
+ act,
+ "label=\"sb\", color=blue, weight=400");
+ }
+
+ thread_array[act->get_tid()] = act;
+ }
+ fprintf(file, "}\n");
+ model_free(thread_array);
+ fclose(file);
+}
+#endif
+
+/** @brief Prints an execution trace summary. */
+void ModelExecution::print_summary() const
+{
+#if SUPPORT_MOD_ORDER_DUMP
+ char buffername[100];
+ sprintf(buffername, "exec%04u", execution_number);
+ mo_graph->dumpGraphToFile(buffername);
+ sprintf(buffername, "graph%04u", execution_number);
+ dumpGraph(buffername);
+#endif
+
+ model_print("Execution %d:", execution_number);
+ if (isfeasibleprefix()) {
+ if (scheduler->all_threads_sleeping())
+ model_print(" SLEEP-SET REDUNDANT");
+ model_print("\n");
+ } else
+ print_infeasibility(" INFEASIBLE");
+ print_list(action_trace);
+ model_print("\n");
+ if (!promises->empty()) {
+ model_print("Pending promises:\n");
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ model_print(" [P%u] ", i);
+ (*promises)[i]->print();
+ }
+ model_print("\n");
+ }
+}
+
+/**
+ * Add a Thread to the system for the first time. Should only be called once
+ * per thread.
+ * @param t The Thread to add
+ */
+void ModelExecution::add_thread(Thread *t)
+{
+ thread_map->put(id_to_int(t->get_id()), t);
+ if (!t->is_model_thread())
+ scheduler->add_thread(t);
+}
+
+/**
+ * @brief Get a Thread reference by its ID
+ * @param tid The Thread's ID
+ * @return A Thread reference
+ */
+Thread * ModelExecution::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 * ModelExecution::get_thread(const ModelAction *act) const
+{
+ return get_thread(act->get_tid());
+}
+
+/**
+ * @brief Get a Promise's "promise number"
+ *
+ * A "promise number" is an index number that is unique to a promise, valid
+ * only for a specific snapshot of an execution trace. Promises may come and go
+ * as they are generated an resolved, so an index only retains meaning for the
+ * current snapshot.
+ *
+ * @param promise The Promise to check
+ * @return The promise index, if the promise still is valid; otherwise -1
+ */
+int ModelExecution::get_promise_number(const Promise *promise) const
+{
+ for (unsigned int i = 0; i < promises->size(); i++)
+ if ((*promises)[i] == promise)
+ return i;
+ /* Not found */
+ return -1;
+}
+
+/**
+ * @brief Check if a Thread is currently enabled
+ * @param t The Thread to check
+ * @return True if the Thread is currently enabled
+ */
+bool ModelExecution::is_enabled(Thread *t) const
+{
+ return scheduler->is_enabled(t);
+}
+
+/**
+ * @brief Check if a Thread is currently enabled
+ * @param tid The ID of the Thread to check
+ * @return True if the Thread is currently enabled
+ */
+bool ModelExecution::is_enabled(thread_id_t tid) const
+{
+ return scheduler->is_enabled(tid);
+}
+
+/**
+ * @brief Select the next thread to execute based on the curren action
+ *
+ * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
+ * actions should be followed by the execution of their child thread. In either
+ * case, the current action should determine the next thread schedule.
+ *
+ * @param curr The current action
+ * @return The next thread to run, if the current action will determine this
+ * selection; otherwise NULL
+ */
+Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
+{
+ /* Do not split atomic RMW */
+ if (curr->is_rmwr())
+ return get_thread(curr);
+ /* Follow CREATE with the created thread */
+ if (curr->get_type() == THREAD_CREATE)
+ return curr->get_thread_operand();
+ return NULL;
+}
+
+/** @return True if the execution has taken too many steps */
+bool ModelExecution::too_many_steps() const
+{
+ return params->bound != 0 && priv->used_sequence_numbers > params->bound;
+}
+
+/**
+ * Takes the next step in the execution, if possible.
+ * @param curr The current step to take
+ * @return Returns the next Thread to run, if any; NULL if this execution
+ * should terminate
+ */
+Thread * ModelExecution::take_step(ModelAction *curr)
+{
+ Thread *curr_thrd = get_thread(curr);
+ ASSERT(curr_thrd->get_state() == THREAD_READY);
+
+ ASSERT(check_action_enabled(curr)); /* May have side effects? */
+ curr = check_current_action(curr);
+ ASSERT(curr);
+
+ if (curr_thrd->is_blocked() || curr_thrd->is_complete())
+ scheduler->remove_thread(curr_thrd);
+
+ return action_select_next_thread(curr);
+}
+
+/**
+ * Launch end-of-execution release sequence fixups only when
+ * the execution is otherwise feasible AND there are:
+ *
+ * (1) pending release sequences
+ * (2) pending assertions that could be invalidated by a change
+ * in clock vectors (i.e., data races)
+ * (3) no pending promises
+ */
+void ModelExecution::fixup_release_sequences()
+{
+ while (!pending_rel_seqs->empty() &&
+ is_feasible_prefix_ignore_relseq() &&
+ !unrealizedraces.empty()) {
+ model_print("*** WARNING: release sequence fixup action "
+ "(%zu pending release seuqence(s)) ***\n",
+ pending_rel_seqs->size());
+ ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
+ std::memory_order_seq_cst, NULL, VALUE_NONE,
+ model_thread);
+ take_step(fixup);
+ };
+}
--- /dev/null
+/** @file execution.h
+ * @brief Model-checker core
+ */
+
+#ifndef __EXECUTION_H__
+#define __EXECUTION_H__
+
+#include <cstddef>
+#include <inttypes.h>
+
+#include "mymemory.h"
+#include "hashtable.h"
+#include "workqueue.h"
+#include "config.h"
+#include "modeltypes.h"
+#include "stl-model.h"
+#include "context.h"
+#include "params.h"
+
+/* Forward declaration */
+class Node;
+class NodeStack;
+class CycleGraph;
+class Promise;
+class Scheduler;
+class Thread;
+class ClockVector;
+struct model_snapshot_members;
+class ModelChecker;
+struct bug_message;
+
+/** @brief Shorthand for a list of release sequence heads */
+typedef ModelVector<const ModelAction *> rel_heads_list_t;
+typedef SnapList<ModelAction *> action_list_t;
+
+struct PendingFutureValue {
+ PendingFutureValue(ModelAction *writer, ModelAction *reader) :
+ writer(writer), reader(reader)
+ { }
+ const ModelAction *writer;
+ ModelAction *reader;
+};
+
+/** @brief Records information regarding a single pending release sequence */
+struct release_seq {
+ /** @brief The acquire operation */
+ ModelAction *acquire;
+ /** @brief The read operation that may read from a release sequence;
+ * may be the same as acquire, or else an earlier action in the same
+ * thread (i.e., when 'acquire' is a fence-acquire) */
+ const ModelAction *read;
+ /** @brief The head of the RMW chain from which 'read' reads; may be
+ * equal to 'release' */
+ const ModelAction *rf;
+ /** @brief The head of the potential longest release sequence chain */
+ const ModelAction *release;
+ /** @brief The write(s) that may break the release sequence */
+ SnapVector<const ModelAction *> writes;
+};
+
+/** @brief The central structure for model-checking */
+class ModelExecution {
+public:
+ ModelExecution(struct model_params *params, Scheduler *scheduler, NodeStack *node_stack);
+ ~ModelExecution();
+
+ Thread * take_step(ModelAction *curr);
+ void fixup_release_sequences();
+
+ void print_summary() const;
+#if SUPPORT_MOD_ORDER_DUMP
+ void dumpGraph(char *filename) const;
+#endif
+
+ void add_thread(Thread *t);
+ Thread * get_thread(thread_id_t tid) const;
+ Thread * get_thread(const ModelAction *act) const;
+ int get_promise_number(const Promise *promise) const;
+
+ bool is_enabled(Thread *t) const;
+ bool is_enabled(thread_id_t tid) const;
+
+ thread_id_t get_next_id();
+ unsigned int get_num_threads() const;
+
+ ClockVector * get_cv(thread_id_t tid) const;
+ ModelAction * get_parent_action(thread_id_t tid) const;
+ void check_promises_thread_disabled();
+ bool isfeasibleprefix() const;
+
+ action_list_t * get_actions_on_obj(void * obj, thread_id_t tid);
+ ModelAction * get_last_action(thread_id_t tid) const;
+
+ bool check_action_enabled(ModelAction *curr);
+
+ bool assert_bug(const char *msg);
+ bool have_bug_reports() const;
+ SnapVector<bug_message *> * get_bugs() const;
+
+ bool has_asserted() const;
+ void set_assert();
+ bool is_complete_execution() const;
+
+ void print_infeasibility(const char *prefix) const;
+ bool is_feasible_prefix_ignore_relseq() const;
+ bool is_infeasible() const;
+ bool is_deadlocked() const;
+ bool too_many_steps() const;
+
+ ModelAction * get_next_backtrack();
+
+ action_list_t * get_action_trace() const { return action_trace; }
+
+ void increment_execution_number() { execution_number++; }
+
+ MEMALLOC
+private:
+ const model_params * const params;
+
+ /** The scheduler to use: tracks the running/ready Threads */
+ Scheduler * const scheduler;
+
+ bool sleep_can_read_from(ModelAction *curr, const ModelAction *write);
+ bool thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader) const;
+ bool mo_may_allow(const ModelAction *writer, const ModelAction *reader);
+ bool promises_may_allow(const ModelAction *writer, const ModelAction *reader) const;
+ void set_bad_synchronization();
+ bool promises_expired() const;
+ bool should_wake_up(const ModelAction *curr, const Thread *thread) const;
+ void wake_up_sleeping_actions(ModelAction *curr);
+ modelclock_t get_next_seq_num();
+
+ bool next_execution();
+ ModelAction * check_current_action(ModelAction *curr);
+ bool initialize_curr_action(ModelAction **curr);
+ bool process_read(ModelAction *curr);
+ bool process_write(ModelAction *curr);
+ bool process_fence(ModelAction *curr);
+ bool process_mutex(ModelAction *curr);
+ bool process_thread_action(ModelAction *curr);
+ void process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue);
+ bool read_from(ModelAction *act, const ModelAction *rf);
+ bool synchronize(const ModelAction *first, ModelAction *second);
+
+ template <typename T>
+ bool check_recency(ModelAction *curr, const T *rf) const;
+
+ template <typename T, typename U>
+ bool should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const;
+
+ ModelAction * get_last_fence_conflict(ModelAction *act) const;
+ ModelAction * get_last_conflict(ModelAction *act) const;
+ void set_backtracking(ModelAction *act);
+ bool set_latest_backtrack(ModelAction *act);
+ Promise * pop_promise_to_resolve(const ModelAction *curr);
+ bool resolve_promise(ModelAction *curr, Promise *promise);
+ void compute_promises(ModelAction *curr);
+ void compute_relseq_breakwrites(ModelAction *curr);
+
+ void check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv);
+ void mo_check_promises(const ModelAction *act, bool is_read_check);
+ void thread_blocking_check_promises(Thread *blocker, Thread *waiting);
+
+ void check_curr_backtracking(ModelAction *curr);
+ void add_action_to_lists(ModelAction *act);
+ ModelAction * get_last_fence_release(thread_id_t tid) const;
+ ModelAction * get_last_seq_cst_write(ModelAction *curr) const;
+ ModelAction * get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const;
+ ModelAction * get_last_unlock(ModelAction *curr) const;
+ void build_may_read_from(ModelAction *curr);
+ ModelAction * process_rmw(ModelAction *curr);
+
+ template <typename rf_type>
+ bool r_modification_order(ModelAction *curr, const rf_type *rf);
+
+ bool w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv);
+ void get_release_seq_heads(ModelAction *acquire, ModelAction *read, rel_heads_list_t *release_heads);
+ bool release_seq_heads(const ModelAction *rf, rel_heads_list_t *release_heads, struct release_seq *pending) const;
+ bool resolve_release_sequences(void *location, work_queue_t *work_queue);
+ void add_future_value(const ModelAction *writer, ModelAction *reader);
+
+ ModelAction * get_uninitialized_action(const ModelAction *curr) const;
+
+ action_list_t * const action_trace;
+ HashTable<int, Thread *, int> * const thread_map;
+
+ /** Per-object list of actions. Maps an object (i.e., memory location)
+ * to a trace of all actions performed on the object. */
+ HashTable<const void *, action_list_t *, uintptr_t, 4> * const obj_map;
+
+ /** Per-object list of actions. Maps an object (i.e., memory location)
+ * to a trace of all actions performed on the object. */
+ HashTable<const void *, action_list_t *, uintptr_t, 4> * const condvar_waiters_map;
+
+ HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4 > * const obj_thrd_map;
+ SnapVector<Promise *> * const promises;
+ SnapVector<struct PendingFutureValue> * const futurevalues;
+
+ /**
+ * List of pending release sequences. Release sequences might be
+ * determined lazily as promises are fulfilled and modification orders
+ * are established. Each entry in the list may only be partially
+ * filled, depending on its pending status.
+ */
+ SnapVector<struct release_seq *> * const pending_rel_seqs;
+
+ SnapVector<ModelAction *> * const thrd_last_action;
+ SnapVector<ModelAction *> * const thrd_last_fence_release;
+ NodeStack * const node_stack;
+
+ /** A special model-checker Thread; used for associating with
+ * model-checker-related ModelAcitons */
+ Thread *model_thread;
+
+ /** Private data members that should be snapshotted. They are grouped
+ * together for efficiency and maintainability. */
+ struct model_snapshot_members * const priv;
+
+ /**
+ * @brief The modification order graph
+ *
+ * A directed acyclic graph recording observations of the modification
+ * order on all the atomic objects in the system. This graph should
+ * never contain any cycles, as that represents a violation of the
+ * memory model (total ordering). This graph really consists of many
+ * disjoint (unconnected) subgraphs, each graph corresponding to a
+ * separate ordering on a distinct object.
+ *
+ * The edges in this graph represent the "ordered before" relation,
+ * such that <tt>a --> b</tt> means <tt>a</tt> was ordered before
+ * <tt>b</tt>.
+ */
+ CycleGraph * const mo_graph;
+
+ int execution_number;
+
+ Thread * action_select_next_thread(const ModelAction *curr) const;
+};
+
+#endif /* __EXECUTION_H__ */
#include "schedule.h"
#include "snapshot-interface.h"
#include "common.h"
-#include "clockvector.h"
-#include "cyclegraph.h"
-#include "promise.h"
#include "datarace.h"
#include "threads-model.h"
#include "output.h"
#include "traceanalysis.h"
+#include "execution.h"
#include "bugmessage.h"
#define INITIAL_THREAD_ID 0
ModelChecker *model;
-/**
- * Structure for holding small ModelChecker members that should be snapshotted
- */
-struct model_snapshot_members {
- model_snapshot_members() :
- /* First thread created will have id INITIAL_THREAD_ID */
- next_thread_id(INITIAL_THREAD_ID),
- used_sequence_numbers(0),
- next_backtrack(NULL),
- bugs(),
- stats(),
- failed_promise(false),
- too_many_reads(false),
- no_valid_reads(false),
- bad_synchronization(false),
- asserted(false)
- { }
-
- ~model_snapshot_members() {
- for (unsigned int i = 0; i < bugs.size(); i++)
- delete bugs[i];
- bugs.clear();
- }
-
- unsigned int next_thread_id;
- modelclock_t used_sequence_numbers;
- ModelAction *next_backtrack;
- SnapVector<bug_message *> bugs;
- struct execution_stats stats;
- bool failed_promise;
- bool too_many_reads;
- bool no_valid_reads;
- /** @brief Incorrectly-ordered synchronization was made */
- bool bad_synchronization;
- bool asserted;
-
- SNAPSHOTALLOC
-};
-
/** @brief Constructor */
ModelChecker::ModelChecker(struct model_params params) :
/* Initialize default scheduler */
params(params),
scheduler(new Scheduler()),
+ node_stack(new NodeStack()),
+ execution(new ModelExecution(¶ms, scheduler, node_stack)),
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>()),
- condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
- obj_thrd_map(new HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4 >()),
- promises(new SnapVector<Promise *>()),
- futurevalues(new SnapVector<struct PendingFutureValue>()),
- pending_rel_seqs(new SnapVector<struct release_seq *>()),
- thrd_last_action(new SnapVector<ModelAction *>(1)),
- thrd_last_fence_release(new SnapVector<ModelAction *>()),
- node_stack(new NodeStack()),
- trace_analyses(new ModelVector<TraceAnalysis *>()),
- priv(new struct model_snapshot_members()),
- mo_graph(new CycleGraph())
+ trace_analyses(new ModelVector<TraceAnalysis *>())
{
- /* 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 (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 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 thrd_last_fence_release;
delete node_stack;
for (unsigned int i = 0; i < trace_analyses->size(); i++)
delete (*trace_analyses)[i];
delete trace_analyses;
delete scheduler;
- delete mo_graph;
- delete priv;
-}
-
-static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
-{
- action_list_t *tmp = hash->get(ptr);
- if (tmp == NULL) {
- tmp = new action_list_t();
- hash->put(ptr, tmp);
- }
- return tmp;
-}
-
-static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
-{
- SnapVector<action_list_t> *tmp = hash->get(ptr);
- if (tmp == NULL) {
- tmp = new SnapVector<action_list_t>();
- hash->put(ptr, tmp);
- }
- return tmp;
-}
-
-action_list_t * ModelChecker::get_actions_on_obj(void * obj, thread_id_t tid) {
- SnapVector<action_list_t> *wrv=obj_thrd_map->get(obj);
- if (wrv==NULL)
- return NULL;
- unsigned int thread=id_to_int(tid);
- if (thread < wrv->size())
- return &(*wrv)[thread];
- else
- return NULL;
}
-
/**
* Restores user program to initial state and resets all model-checker data
* structures.
snapshot_backtrack_before(0);
}
-/** @return a thread ID for a new Thread */
-thread_id_t ModelChecker::get_next_id()
-{
- return priv->next_thread_id++;
-}
-
/** @return the number of user threads created during this execution */
unsigned int ModelChecker::get_num_threads() const
{
- return priv->next_thread_id;
+ return execution->get_num_threads();
}
/**
return scheduler->get_current_thread();
}
-/** @return a sequence number for a new ModelAction */
-modelclock_t ModelChecker::get_next_seq_num()
-{
- return ++priv->used_sequence_numbers;
-}
-
-/**
- * @brief Select the next thread to execute based on the curren action
- *
- * RMW actions occur in two parts, and we cannot split them. And THREAD_CREATE
- * actions should be followed by the execution of their child thread. In either
- * case, the current action should determine the next thread schedule.
- *
- * @param curr The current action
- * @return The next thread to run, if the current action will determine this
- * selection; otherwise NULL
- */
-Thread * ModelChecker::action_select_next_thread(const ModelAction *curr) const
-{
- /* Do not split atomic RMW */
- if (curr->is_rmwr())
- return get_thread(curr);
- /* Follow CREATE with the created thread */
- if (curr->get_type() == THREAD_CREATE)
- return curr->get_thread_operand();
- return NULL;
-}
-
/**
* @brief Choose the next thread to execute.
*
if (diverge == NULL)
return scheduler->select_next_thread(node_stack->get_head());
+
/* Else, we are trying to replay an execution */
ModelAction *next = node_stack->get_next()->get_action();
* 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++) {
}
}
-/**
- * @brief Should the current action wake up a given thread?
- *
- * @param curr The current action
- * @param thread The thread that we might wake up
- * @return True, if we should wake up the sleeping thread; false otherwise
- */
-bool ModelChecker::should_wake_up(const ModelAction *curr, const Thread *thread) const
-{
- const ModelAction *asleep = thread->get_pending();
- /* Don't allow partial RMW to wake anyone up */
- if (curr->is_rmwr())
- return false;
- /* Synchronizing actions may have been backtracked */
- if (asleep->could_synchronize_with(curr))
- return true;
- /* All acquire/release fences and fence-acquire/store-release */
- if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
- return true;
- /* Fence-release + store can awake load-acquire on the same location */
- if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
- ModelAction *fence_release = get_last_fence_release(curr->get_tid());
- if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
- return true;
- }
- return false;
-}
-
-void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
-{
- for (unsigned int i = 0; i < get_num_threads(); i++) {
- Thread *thr = get_thread(int_to_id(i));
- if (scheduler->is_sleep_set(thr)) {
- if (should_wake_up(curr, thr))
- /* Remove this thread from sleep set */
- scheduler->remove_sleep(thr);
- }
- }
-}
-
-/** @brief Alert the model-checker that an incorrectly-ordered
- * synchronization was made */
-void ModelChecker::set_bad_synchronization()
-{
- priv->bad_synchronization = true;
-}
-
-/**
- * Check whether the current trace has triggered an assertion which should halt
- * its execution.
- *
- * @return True, if the execution should be aborted; false otherwise
- */
-bool ModelChecker::has_asserted() const
-{
- return priv->asserted;
-}
-
-/**
- * Trigger a trace assertion which should cause this execution to be halted.
- * This can be due to a detected bug or due to an infeasibility that should
- * halt ASAP.
- */
-void ModelChecker::set_assert()
-{
- priv->asserted = true;
-}
-
-/**
- * Check if we are in a deadlock. Should only be called at the end of an
- * execution, although it should not give false positives in the middle of an
- * execution (there should be some ENABLED thread).
- *
- * @return True if program is in a deadlock; false otherwise
- */
-bool ModelChecker::is_deadlocked() const
-{
- bool blocking_threads = false;
- for (unsigned int i = 0; i < get_num_threads(); i++) {
- thread_id_t tid = int_to_id(i);
- if (is_enabled(tid))
- return false;
- Thread *t = get_thread(tid);
- if (!t->is_model_thread() && t->get_pending())
- blocking_threads = true;
- }
- return blocking_threads;
-}
-
-/**
- * Check if this is a complete execution. That is, have all thread completed
- * execution (rather than exiting because sleep sets have forced a redundant
- * execution).
- *
- * @return True if the execution is complete.
- */
-bool ModelChecker::is_complete_execution() const
-{
- for (unsigned int i = 0; i < get_num_threads(); i++)
- if (is_enabled(int_to_id(i)))
- return false;
- return true;
-}
-
/**
* @brief Assert a bug in the executing program.
*
vsnprintf(str, sizeof(str), msg, ap);
va_end(ap);
- priv->bugs.push_back(new bug_message(str));
-
- if (isfeasibleprefix()) {
- set_assert();
- return true;
- }
- return false;
+ return execution->assert_bug(str);
}
/**
switch_to_master(NULL);
}
-/** @return True, if any bugs have been reported for this execution */
-bool ModelChecker::have_bug_reports() const
-{
- return priv->bugs.size() != 0;
-}
-
/** @brief Print bug report listing for this execution (if any bugs exist) */
void ModelChecker::print_bugs() const
{
- if (have_bug_reports()) {
+ if (execution->have_bug_reports()) {
+ SnapVector<bug_message *> *bugs = execution->get_bugs();
+
model_print("Bug report: %zu bug%s detected\n",
- priv->bugs.size(),
- priv->bugs.size() > 1 ? "s" : "");
- for (unsigned int i = 0; i < priv->bugs.size(); i++)
- priv->bugs[i]->print();
+ bugs->size(),
+ bugs->size() > 1 ? "s" : "");
+ for (unsigned int i = 0; i < bugs->size(); i++)
+ (*bugs)[i]->print();
}
}
void ModelChecker::record_stats()
{
stats.num_total++;
- if (!isfeasibleprefix())
+ if (!execution->isfeasibleprefix())
stats.num_infeasible++;
- else if (have_bug_reports())
+ else if (execution->have_bug_reports())
stats.num_buggy_executions++;
- else if (is_complete_execution())
+ else if (execution->is_complete_execution())
stats.num_complete++;
else {
stats.num_redundant++;
print_bugs();
model_print("\n");
- print_summary();
+ execution->print_summary();
}
/**
{
DBG();
/* Is this execution a feasible execution that's worth bug-checking? */
- bool complete = isfeasibleprefix() && (is_complete_execution() ||
- have_bug_reports());
+ bool complete = execution->isfeasibleprefix() &&
+ (execution->is_complete_execution() ||
+ execution->have_bug_reports());
/* End-of-execution bug checks */
if (complete) {
- if (is_deadlocked())
+ if (execution->is_deadlocked())
assert_bug("Deadlock detected");
checkDataRaces();
record_stats();
/* Output */
- if (params.verbose || (complete && have_bug_reports()))
+ if (params.verbose || (complete && execution->have_bug_reports()))
print_execution(complete);
else
clear_program_output();
if (complete)
earliest_diverge = NULL;
- if ((diverge = get_next_backtrack()) == NULL)
+ if ((diverge = execution->get_next_backtrack()) == NULL)
return false;
if (DBG_ENABLED()) {
diverge->print();
}
+ execution->increment_execution_number();
reset_to_initial_state();
return true;
}
/** @brief Run trace analyses on complete trace */
void ModelChecker::run_trace_analyses() {
for (unsigned int i = 0; i < trace_analyses->size(); i++)
- (*trace_analyses)[i]->analyze(action_trace);
+ (*trace_analyses)[i]->analyze(execution->get_action_trace());
}
/**
- * @brief Find the last fence-related backtracking conflict for a ModelAction
- *
- * This function performs the search for the most recent conflicting action
- * against which we should perform backtracking, as affected by fence
- * operations. This includes pairs of potentially-synchronizing actions which
- * occur due to fence-acquire or fence-release, and hence should be explored in
- * the opposite execution order.
- *
- * @param act The current action
- * @return The most recent action which conflicts with act due to fences
+ * @brief Get a Thread reference by its ID
+ * @param tid The Thread's ID
+ * @return A Thread reference
*/
-ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const
+Thread * ModelChecker::get_thread(thread_id_t tid) const
{
- /* Only perform release/acquire fence backtracking for stores */
- if (!act->is_write())
- return NULL;
-
- /* Find a fence-release (or, act is a release) */
- ModelAction *last_release;
- if (act->is_release())
- last_release = act;
- else
- last_release = get_last_fence_release(act->get_tid());
- if (!last_release)
- return NULL;
-
- /* Skip past the release */
- action_list_t *list = action_trace;
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++)
- if (*rit == last_release)
- break;
- ASSERT(rit != list->rend());
-
- /* Find a prior:
- * load-acquire
- * or
- * load --sb-> fence-acquire */
- ModelVector<ModelAction *> acquire_fences(get_num_threads(), NULL);
- ModelVector<ModelAction *> prior_loads(get_num_threads(), NULL);
- bool found_acquire_fences = false;
- for ( ; rit != list->rend(); rit++) {
- ModelAction *prev = *rit;
- if (act->same_thread(prev))
- continue;
-
- int tid = id_to_int(prev->get_tid());
-
- if (prev->is_read() && act->same_var(prev)) {
- if (prev->is_acquire()) {
- /* Found most recent load-acquire, don't need
- * to search for more fences */
- if (!found_acquire_fences)
- return NULL;
- } else {
- prior_loads[tid] = prev;
- }
- }
- if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
- found_acquire_fences = true;
- acquire_fences[tid] = prev;
- }
- }
-
- ModelAction *latest_backtrack = NULL;
- for (unsigned int i = 0; i < acquire_fences.size(); i++)
- if (acquire_fences[i] && prior_loads[i])
- if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
- latest_backtrack = acquire_fences[i];
- return latest_backtrack;
+ return execution->get_thread(tid);
}
/**
- * @brief Find the last backtracking conflict for a ModelAction
- *
- * This function performs the search for the most recent conflicting action
- * against which we should perform backtracking. This primary includes pairs of
- * synchronizing actions which should be explored in the opposite execution
- * order.
- *
- * @param act The current action
- * @return The most recent action which conflicts with act
- */
-ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const
-{
- switch (act->get_type()) {
- /* case ATOMIC_FENCE: fences don't directly cause backtracking */
- case ATOMIC_READ:
- case ATOMIC_WRITE:
- case ATOMIC_RMW: {
- ModelAction *ret = NULL;
-
- /* linear search: from most recent to oldest */
- action_list_t *list = get_safe_ptr_action(obj_map, 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)) {
- ret = prev;
- break;
- }
- }
-
- ModelAction *ret2 = get_last_fence_conflict(act);
- if (!ret2)
- return ret;
- if (!ret)
- return ret2;
- if (*ret < *ret2)
- return ret2;
- return ret;
- }
- case ATOMIC_LOCK:
- case ATOMIC_TRYLOCK: {
- /* linear search: from most recent to oldest */
- action_list_t *list = get_safe_ptr_action(obj_map, 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 = get_safe_ptr_action(obj_map, 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 = get_safe_ptr_action(obj_map, 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;
- }
-
- case ATOMIC_NOTIFY_ALL:
- case ATOMIC_NOTIFY_ONE: {
- /* linear search: from most recent to oldest */
- action_list_t *list = get_safe_ptr_action(obj_map, 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;
- }
- 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.
+ * @brief Get a reference to the Thread in which a ModelAction was executed
+ * @param act The ModelAction
+ * @return A Thread reference
*/
-void ModelChecker::set_backtracking(ModelAction *act)
+Thread * ModelChecker::get_thread(const ModelAction *act) const
{
- Thread *t = get_thread(act);
- ModelAction *prev = get_last_conflict(act);
- if (prev == NULL)
- return;
-
- Node *node = prev->get_node()->get_parent();
-
- /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
- int low_tid, high_tid;
- if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
- low_tid = id_to_int(act->get_tid());
- high_tid = low_tid + 1;
- } else {
- low_tid = 0;
- high_tid = get_num_threads();
- }
-
- for (int i = low_tid; i < high_tid; i++) {
- thread_id_t tid = int_to_id(i);
-
- /* Make sure this thread can be enabled here. */
- if (i >= node->get_num_threads())
- break;
-
- /* See Dynamic Partial Order Reduction (addendum), POPL '05 */
- /* Don't backtrack into a point where the thread is disabled or sleeping. */
- if (node->enabled_status(tid) != 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;
- }
-
- /* See if CHESS-like yield fairness allows */
- if (model->params.yieldon) {
- 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_over(tid, tother)) {
- unfair = true;
- break;
- }
- }
- if (unfair)
- continue;
- }
-
- /* Cache the latest backtracking point */
- set_latest_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();
- }
- }
+ return execution->get_thread(act);
}
/**
- * @brief Cache the a backtracking point as the "most recent", if eligible
- *
- * Note that this does not prepare the NodeStack for this backtracking
- * operation, it only caches the action on a per-execution basis
- *
- * @param act The operation at which we should explore a different next action
- * (i.e., backtracking point)
- * @return True, if this action is now the most recent backtracking point;
- * false otherwise
+ * @brief Check if a Thread is currently enabled
+ * @param t The Thread to check
+ * @return True if the Thread is currently enabled
*/
-bool ModelChecker::set_latest_backtrack(ModelAction *act)
+bool ModelChecker::is_enabled(Thread *t) const
{
- if (!priv->next_backtrack || *act > *priv->next_backtrack) {
- priv->next_backtrack = act;
- return true;
- }
- return false;
+ return scheduler->is_enabled(t);
}
/**
- * 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.
+ * @brief Check if a Thread is currently enabled
+ * @param tid The ID of the Thread to check
+ * @return True if the Thread is currently enabled
*/
-ModelAction * ModelChecker::get_next_backtrack()
+bool ModelChecker::is_enabled(thread_id_t tid) const
{
- ModelAction *next = priv->next_backtrack;
- priv->next_backtrack = NULL;
- return next;
+ return scheduler->is_enabled(tid);
}
/**
- * Processes a read model action.
- * @param curr is the read model action to process.
- * @return True if processing this read updates the mo_graph.
+ * Switch from a model-checker context to a user-thread context. This is the
+ * complement of ModelChecker::switch_to_master and must be called from the
+ * model-checker context
+ *
+ * @param thread The user-thread to switch to
*/
-bool ModelChecker::process_read(ModelAction *curr)
+void ModelChecker::switch_from_master(Thread *thread)
{
- Node *node = curr->get_node();
- while (true) {
- bool updated = false;
- switch (node->get_read_from_status()) {
- case READ_FROM_PAST: {
- const ModelAction *rf = node->get_read_from_past();
- ASSERT(rf);
-
- mo_graph->startChanges();
-
- ASSERT(!is_infeasible());
- if (!check_recency(curr, rf)) {
- if (node->increment_read_from()) {
- mo_graph->rollbackChanges();
- continue;
- } else {
- priv->too_many_reads = true;
- }
- }
-
- updated = r_modification_order(curr, rf);
- read_from(curr, rf);
- mo_graph->commitChanges();
- mo_check_promises(curr, true);
- break;
- }
- case READ_FROM_PROMISE: {
- Promise *promise = curr->get_node()->get_read_from_promise();
- if (promise->add_reader(curr))
- priv->failed_promise = true;
- curr->set_read_from_promise(promise);
- mo_graph->startChanges();
- if (!check_recency(curr, promise))
- priv->too_many_reads = true;
- updated = r_modification_order(curr, promise);
- mo_graph->commitChanges();
- break;
- }
- case READ_FROM_FUTURE: {
- /* Read from future value */
- struct future_value fv = node->get_future_value();
- Promise *promise = new Promise(curr, fv);
- curr->set_read_from_promise(promise);
- promises->push_back(promise);
- mo_graph->startChanges();
- updated = r_modification_order(curr, promise);
- mo_graph->commitChanges();
- break;
- }
- default:
- ASSERT(false);
- }
- get_thread(curr)->set_return_value(curr->get_return_value());
- return updated;
- }
+ scheduler->set_current_thread(thread);
+ Thread::swap(&system_context, thread);
}
/**
- * 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.
+ * 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.
*
- * @return True if synchronization was updated; false otherwise
+ * @param act The current action that will be explored. May be NULL only if
+ * trace is exiting via an assertion (see ModelExecution::set_assert and
+ * ModelExecution::has_asserted).
+ * @return Return the value returned by the current action
*/
-bool ModelChecker::process_mutex(ModelAction *curr)
+uint64_t ModelChecker::switch_to_master(ModelAction *act)
{
- std::mutex *mutex = curr->get_mutex();
- struct std::mutex_state *state = NULL;
-
- if (mutex)
- state = mutex->get_state();
-
- switch (curr->get_type()) {
- case ATOMIC_TRYLOCK: {
- bool success = !state->locked;
- 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)
- assert_bug("Lock access before initialization");
- state->locked = get_thread(curr);
- ModelAction *unlock = get_last_unlock(curr);
- //synchronize with the previous unlock statement
- if (unlock != NULL) {
- synchronize(unlock, curr);
- return true;
- }
- break;
- }
- case ATOMIC_WAIT:
- case ATOMIC_UNLOCK: {
- /* wake up the other threads */
- for (unsigned int i = 0; i < get_num_threads(); i++) {
- Thread *t = get_thread(int_to_id(i));
- Thread *curr_thrd = get_thread(curr);
- if (t->waiting_on() == curr_thrd && t->get_pending()->is_lock())
- scheduler->wake(t);
- }
-
- /* unlock the lock - after checking who was waiting on it */
- state->locked = NULL;
-
- if (!curr->is_wait())
- break; /* The rest is only for ATOMIC_WAIT */
-
- /* Should we go to sleep? (simulate spurious failures) */
- if (curr->get_node()->get_misc() == 0) {
- get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
- /* disable us */
- scheduler->sleep(get_thread(curr));
- }
- break;
- }
- case ATOMIC_NOTIFY_ALL: {
- action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, 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 = get_safe_ptr_action(condvar_waiters_map, 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;
+ DBG();
+ Thread *old = thread_current();
+ scheduler->set_current_thread(NULL);
+ ASSERT(!old->get_pending());
+ old->set_pending(act);
+ if (Thread::swap(old, &system_context) < 0) {
+ perror("swap threads");
+ exit(EXIT_FAILURE);
}
+ return old->get_return_value();
+}
- default:
- ASSERT(0);
- }
- return false;
+/** Wrapper to run the user's main function, with appropriate arguments */
+void user_main_wrapper(void *)
+{
+ user_main(model->params.argc, model->params.argv);
}
-/**
- * @brief Check if the current pending promises allow a future value to be sent
- *
- * If one of the following is true:
- * (a) there are no pending promises
- * (b) the reader and writer do not cross any promises
- * Then, it is safe to pass a future value back now.
- *
- * Otherwise, we must save the pending future value until (a) or (b) is true
- *
- * @param writer The operation which sends the future value. Must be a write.
- * @param reader The operation which will observe the value. Must be a read.
- * @return True if the future value can be sent now; false if it must wait.
- */
-bool ModelChecker::promises_may_allow(const ModelAction *writer,
- const ModelAction *reader) const
+bool ModelChecker::should_terminate_execution()
{
- if (promises->empty())
+ /* Infeasible -> don't take any more steps */
+ if (execution->is_infeasible())
+ return true;
+ else if (execution->isfeasibleprefix() && execution->have_bug_reports()) {
+ execution->set_assert();
return true;
- for(int i=promises->size()-1;i>=0;i--) {
- ModelAction *pr=(*promises)[i]->get_reader(0);
- //reader is after promise...doesn't cross any promise
- if (*reader > *pr)
- return true;
- //writer is after promise, reader before...bad...
- if (*writer > *pr)
- return false;
}
- return true;
+
+ if (execution->too_many_steps())
+ return true;
+ return false;
}
-/**
- * @brief Add a future value to a reader
- *
- * This function performs a few additional checks to ensure that the future
- * value can be feasibly observed by the reader
- *
- * @param writer The operation whose value is sent. Must be a write.
- * @param reader The read operation which may read the future value. Must be a read.
- */
-void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
+/** @brief Run ModelChecker for the user program */
+void ModelChecker::run()
{
- /* Do more ambitious checks now that mo is more complete */
- if (!mo_may_allow(writer, reader))
- return;
-
- Node *node = reader->get_node();
-
- /* Find an ancestor thread which exists at the time of the reader */
- Thread *write_thread = get_thread(writer);
- while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
- write_thread = write_thread->get_parent();
-
- struct future_value fv = {
- writer->get_write_value(),
- writer->get_seq_number() + params.maxfuturedelay,
- write_thread->get_id(),
- };
- if (node->add_future_value(fv))
- set_latest_backtrack(reader);
-}
-
-/**
- * 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)
-{
- /* Readers to which we may send our future value */
- ModelVector<ModelAction *> send_fv;
-
- const ModelAction *earliest_promise_reader;
- bool updated_promises = false;
-
- bool updated_mod_order = w_modification_order(curr, &send_fv);
- Promise *promise = pop_promise_to_resolve(curr);
-
- if (promise) {
- earliest_promise_reader = promise->get_reader(0);
- updated_promises = resolve_promise(curr, promise);
- } else
- earliest_promise_reader = NULL;
-
- for (unsigned int i = 0; i < send_fv.size(); i++) {
- ModelAction *read = send_fv[i];
-
- /* Don't send future values to reads after the Promise we resolve */
- if (!earliest_promise_reader || *read < *earliest_promise_reader) {
- /* Check if future value can be sent immediately */
- if (promises_may_allow(curr, read)) {
- add_future_value(curr, read);
- } else {
- futurevalues->push_back(PendingFutureValue(curr, read));
- }
- }
- }
-
- /* Check the pending future values */
- for (int i = (int)futurevalues->size() - 1; i >= 0; i--) {
- struct PendingFutureValue pfv = (*futurevalues)[i];
- if (promises_may_allow(pfv.writer, pfv.reader)) {
- add_future_value(pfv.writer, pfv.reader);
- futurevalues->erase(futurevalues->begin() + i);
- }
- }
-
- mo_graph->commitChanges();
- mo_check_promises(curr, false);
-
- get_thread(curr)->set_return_value(VALUE_NONE);
- return updated_mod_order || updated_promises;
-}
-
-/**
- * Process a fence ModelAction
- * @param curr The ModelAction to process
- * @return True if synchronization was updated
- */
-bool ModelChecker::process_fence(ModelAction *curr)
-{
- /*
- * fence-relaxed: no-op
- * fence-release: only log the occurence (not in this function), for
- * use in later synchronization
- * fence-acquire (this function): search for hypothetical release
- * sequences
- * fence-seq-cst: MO constraints formed in {r,w}_modification_order
- */
- bool updated = false;
- if (curr->is_acquire()) {
- action_list_t *list = action_trace;
- action_list_t::reverse_iterator rit;
- /* Find X : is_read(X) && X --sb-> curr */
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
- if (act == curr)
- continue;
- if (act->get_tid() != curr->get_tid())
- continue;
- /* Stop at the beginning of the thread */
- if (act->is_thread_start())
- break;
- /* Stop once we reach a prior fence-acquire */
- if (act->is_fence() && act->is_acquire())
- break;
- if (!act->is_read())
- continue;
- /* read-acquire will find its own release sequences */
- if (act->is_acquire())
- continue;
-
- /* Establish hypothetical release sequences */
- rel_heads_list_t release_heads;
- get_release_seq_heads(curr, act, &release_heads);
- for (unsigned int i = 0; i < release_heads.size(); i++)
- synchronize(release_heads[i], curr);
- if (release_heads.size() != 0)
- updated = true;
- }
- }
- return updated;
-}
-
-/**
- * @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: {
- thrd_t *thrd = (thrd_t *)curr->get_location();
- struct thread_params *params = (struct thread_params *)curr->get_value();
- Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
- add_thread(th);
- th->set_creation(curr);
- /* Promises can be satisfied by children */
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->thread_is_available(curr->get_tid()))
- promise->add_thread(th->get_id());
- }
- break;
- }
- case THREAD_JOIN: {
- Thread *blocking = curr->get_thread_operand();
- ModelAction *act = get_last_action(blocking->get_id());
- synchronize(act, curr);
- updated = true; /* trigger rel-seq checks */
- break;
- }
- case THREAD_FINISH: {
- Thread *th = get_thread(curr);
- /* Wake up any joining threads */
- for (unsigned int i = 0; i < get_num_threads(); i++) {
- Thread *waiting = get_thread(int_to_id(i));
- if (waiting->waiting_on() == th &&
- waiting->get_pending()->is_thread_join())
- scheduler->wake(waiting);
- }
- th->complete();
- /* Completed thread can't satisfy promises */
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->thread_is_available(th->get_id()))
- if (promise->eliminate_thread(th->get_id()))
- priv->failed_promise = true;
- }
- updated = true; /* trigger rel-seq checks */
- break;
- }
- case THREAD_START: {
- check_promises(curr->get_tid(), NULL, curr->get_cv());
- break;
- }
- default:
- break;
- }
-
- return updated;
-}
-
-/**
- * @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 (!synchronize(release, acquire))
- 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)) {
- synchronize(acquire, propagate);
- /* Re-check 'propagate' for mo_graph edges */
- work_queue->push_back(MOEdgeWorkEntry(propagate));
- }
- }
- } else {
- /* Break release sequence with new edges:
- * release --mo--> write --mo--> rf */
- mo_graph->addEdge(release, write);
- mo_graph->addEdge(write, rf);
- }
-
- /* See if we have realized a data race */
- checkDataRaces();
-}
-
-/**
- * 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, with a different
- * action "returned" its place (pass-by-reference)
- * @return True if curr is a newly-explored action; false otherwise
- */
-bool ModelChecker::initialize_curr_action(ModelAction **curr)
-{
- ModelAction *newcurr;
-
- if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
- newcurr = process_rmw(*curr);
- delete *curr;
-
- if (newcurr->is_rmw())
- compute_promises(newcurr);
-
- *curr = newcurr;
- return false;
- }
-
- (*curr)->set_seq_number(get_next_seq_num());
-
- newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
- 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()));
-
- *curr = newcurr;
- return false; /* Action was explored previously */
- } else {
- newcurr = *curr;
-
- /* Always compute new clock vector */
- newcurr->create_cv(get_parent_action(newcurr->get_tid()));
-
- /* Assign most recent release fence */
- newcurr->set_last_fence_release(get_last_fence_release(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(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
- }
- return true; /* This was a new ModelAction */
- }
-}
-
-/**
- * @brief Establish reads-from relation between two actions
- *
- * Perform basic operations involved with establishing a concrete rf relation,
- * including setting the ModelAction data and checking for release sequences.
- *
- * @param act The action that is reading (must be a read)
- * @param rf The action from which we are reading (must be a write)
- *
- * @return True if this read established synchronization
- */
-bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
-{
- ASSERT(rf);
- ASSERT(rf->is_write());
-
- act->set_read_from(rf);
- if (act->is_acquire()) {
- rel_heads_list_t release_heads;
- get_release_seq_heads(act, act, &release_heads);
- int num_heads = release_heads.size();
- for (unsigned int i = 0; i < release_heads.size(); i++)
- if (!synchronize(release_heads[i], act))
- num_heads--;
- return num_heads > 0;
- }
- return false;
-}
-
-/**
- * @brief Synchronizes two actions
- *
- * When A synchronizes with B (or A --sw-> B), B inherits A's clock vector.
- * This function performs the synchronization as well as providing other hooks
- * for other checks along with synchronization.
- *
- * @param first The left-hand side of the synchronizes-with relation
- * @param second The right-hand side of the synchronizes-with relation
- * @return True if the synchronization was successful (i.e., was consistent
- * with the execution order); false otherwise
- */
-bool ModelChecker::synchronize(const ModelAction *first, ModelAction *second)
-{
- if (*second < *first) {
- set_bad_synchronization();
- return false;
- }
- check_promises(first->get_tid(), second->get_cv(), first->get_cv());
- return second->synchronize_with(first);
-}
-
-/**
- * Check promises and eliminate potentially-satisfying threads when a thread is
- * blocked (e.g., join, lock). A thread which is waiting on another thread can
- * no longer satisfy a promise generated from that thread.
- *
- * @param blocker The thread on which a thread is waiting
- * @param waiting The waiting thread
- */
-void ModelChecker::thread_blocking_check_promises(Thread *blocker, Thread *waiting)
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (!promise->thread_is_available(waiting->get_id()))
- continue;
- for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
- ModelAction *reader = promise->get_reader(j);
- if (reader->get_tid() != blocker->get_id())
- continue;
- if (promise->eliminate_thread(waiting->get_id())) {
- /* Promise has failed */
- priv->failed_promise = true;
- } else {
- /* Only eliminate the 'waiting' thread once */
- return;
- }
- }
- }
-}
-
-/**
- * @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 = curr->get_mutex();
- struct std::mutex_state *state = lock->get_state();
- if (state->locked)
- return false;
- } else if (curr->is_thread_join()) {
- Thread *blocking = curr->get_thread_operand();
- if (!blocking->is_complete()) {
- thread_blocking_check_promises(blocking, get_thread(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 ModelAction that is actually executed; may be different than
- * curr; may be NULL, if the current action is not enabled to run
- */
-ModelAction * ModelChecker::check_current_action(ModelAction *curr)
-{
- ASSERT(curr);
- bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
- bool newly_explored = initialize_curr_action(&curr);
-
- DBG();
-
- wake_up_sleeping_actions(curr);
-
- /* Compute fairness information for CHESS yield algorithm */
- if (model->params.yieldon) {
- curr->get_node()->update_yield(scheduler);
- }
-
- /* Add the action to lists before any other model-checking tasks */
- if (!second_part_of_rmw)
- add_action_to_lists(curr);
-
- /* Build may_read_from set for newly-created actions */
- if (newly_explored && curr->is_read())
- build_may_read_from(curr);
-
- /* Initialize work_queue with the "current action" work */
- work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
- while (!work_queue.empty() && !has_asserted()) {
- 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() && !second_part_of_rmw && process_read(act))
- update = true;
-
- if (act->is_write() && process_write(act))
- update = true;
-
- if (act->is_fence() && process_fence(act))
- update_all = 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();
- const Promise *promise = act->get_reads_from_promise();
- if (rf) {
- if (r_modification_order(act, rf))
- updated = true;
- } else if (promise) {
- if (r_modification_order(act, promise))
- updated = true;
- }
- }
- if (act->is_write()) {
- if (w_modification_order(act, NULL))
- 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 curr;
-}
-
-void ModelChecker::check_curr_backtracking(ModelAction *curr)
-{
- Node *currnode = curr->get_node();
- Node *parnode = currnode->get_parent();
-
- if ((parnode && !parnode->backtrack_empty()) ||
- !currnode->misc_empty() ||
- !currnode->read_from_empty() ||
- !currnode->promise_empty() ||
- !currnode->relseq_break_empty()) {
- set_latest_backtrack(curr);
- }
-}
-
-bool ModelChecker::promises_expired() const
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->get_expiration() < priv->used_sequence_numbers)
- return true;
- }
- return false;
-}
-
-/**
- * This is the strongest feasibility check available.
- * @return whether the current trace (partial or complete) must be a prefix of
- * a feasible trace.
- */
-bool ModelChecker::isfeasibleprefix() const
-{
- return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
-}
-
-/**
- * Print disagnostic information about an infeasible execution
- * @param prefix A string to prefix the output with; if NULL, then a default
- * message prefix will be provided
- */
-void ModelChecker::print_infeasibility(const char *prefix) const
-{
- char buf[100];
- char *ptr = buf;
- if (mo_graph->checkForCycles())
- ptr += sprintf(ptr, "[mo cycle]");
- if (priv->failed_promise)
- ptr += sprintf(ptr, "[failed promise]");
- if (priv->too_many_reads)
- ptr += sprintf(ptr, "[too many reads]");
- if (priv->no_valid_reads)
- ptr += sprintf(ptr, "[no valid reads-from]");
- if (priv->bad_synchronization)
- ptr += sprintf(ptr, "[bad sw ordering]");
- if (promises_expired())
- ptr += sprintf(ptr, "[promise expired]");
- if (promises->size() != 0)
- ptr += sprintf(ptr, "[unresolved promise]");
- if (ptr != buf)
- model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
-}
-
-/**
- * Returns whether the current completed trace is feasible, except for pending
- * release sequences.
- */
-bool ModelChecker::is_feasible_prefix_ignore_relseq() const
-{
- return !is_infeasible() && promises->size() == 0;
-}
-
-/**
- * Check if the current partial trace is infeasible. Does not check any
- * end-of-execution flags, which might rule out the execution. Thus, this is
- * useful only for ruling an execution as infeasible.
- * @return whether the current partial trace is infeasible.
- */
-bool ModelChecker::is_infeasible() const
-{
- return mo_graph->checkForCycles() ||
- priv->no_valid_reads ||
- priv->failed_promise ||
- priv->too_many_reads ||
- priv->bad_synchronization ||
- promises_expired();
-}
-
-/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
-ModelAction * ModelChecker::process_rmw(ModelAction *act) {
- ModelAction *lastread = get_last_action(act->get_tid());
- lastread->process_rmw(act);
- if (act->is_rmw()) {
- if (lastread->get_reads_from())
- mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
- else
- mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
- mo_graph->commitChanges();
- }
- return lastread;
-}
-
-/**
- * A helper function for ModelChecker::check_recency, to check if the current
- * thread is able to read from a different write/promise for 'params.maxreads'
- * number of steps and if that write/promise should become visible (i.e., is
- * ordered later in the modification order). This helps model memory liveness.
- *
- * @param curr The current action. Must be a read.
- * @param rf The write/promise from which we plan to read
- * @param other_rf The write/promise from which we may read
- * @return True if we were able to read from other_rf for params.maxreads steps
- */
-template <typename T, typename U>
-bool ModelChecker::should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const
-{
- /* Need a different write/promise */
- if (other_rf->equals(rf))
- return false;
-
- /* Only look for "newer" writes/promises */
- if (!mo_graph->checkReachable(rf, other_rf))
- return false;
-
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- action_list_t *list = &(*thrd_lists)[id_to_int(curr->get_tid())];
- action_list_t::reverse_iterator rit = list->rbegin();
- ASSERT((*rit) == curr);
- /* Skip past curr */
- rit++;
-
- /* Does this write/promise work for everyone? */
- for (int i = 0; i < params.maxreads; i++, rit++) {
- ModelAction *act = *rit;
- if (!act->may_read_from(other_rf))
- return false;
- }
- return true;
-}
-
-/**
- * Checks whether a thread has read from the same write or Promise for too many
- * times without seeing the effects of a later write/Promise.
- *
- * Basic idea:
- * 1) there must a different write/promise that we could read from,
- * 2) we must have read from the same write/promise in excess of maxreads times,
- * 3) that other write/promise must have been in the reads_from set for maxreads times, and
- * 4) that other write/promise must be mod-ordered after the write/promise we are reading.
- *
- * If so, we decide that the execution is no longer feasible.
- *
- * @param curr The current action. Must be a read.
- * @param rf The ModelAction/Promise from which we might read.
- * @return True if the read should succeed; false otherwise
- */
-template <typename T>
-bool ModelChecker::check_recency(ModelAction *curr, const T *rf) const
-{
- if (!params.maxreads)
- return true;
-
- //NOTE: Next check is just optimization, not really necessary....
- if (curr->get_node()->get_read_from_past_size() +
- curr->get_node()->get_read_from_promise_size() <= 1)
- return true;
-
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- int tid = id_to_int(curr->get_tid());
- ASSERT(tid < (int)thrd_lists->size());
- action_list_t *list = &(*thrd_lists)[tid];
- action_list_t::reverse_iterator rit = list->rbegin();
- ASSERT((*rit) == curr);
- /* Skip past curr */
- rit++;
-
- action_list_t::reverse_iterator ritcopy = rit;
- /* See if we have enough reads from the same value */
- for (int count = 0; count < params.maxreads; ritcopy++, count++) {
- if (ritcopy == list->rend())
- return true;
- ModelAction *act = *ritcopy;
- if (!act->is_read())
- return true;
- if (act->get_reads_from_promise() && !act->get_reads_from_promise()->equals(rf))
- return true;
- if (act->get_reads_from() && !act->get_reads_from()->equals(rf))
- return true;
- if (act->get_node()->get_read_from_past_size() +
- act->get_node()->get_read_from_promise_size() <= 1)
- return true;
- }
- for (int i = 0; i < curr->get_node()->get_read_from_past_size(); i++) {
- const ModelAction *write = curr->get_node()->get_read_from_past(i);
- if (should_read_instead(curr, rf, write))
- return false; /* liveness failure */
- }
- for (int i = 0; i < curr->get_node()->get_read_from_promise_size(); i++) {
- const Promise *promise = curr->get_node()->get_read_from_promise(i);
- if (should_read_instead(curr, rf, promise))
- return false; /* liveness failure */
- }
- return true;
-}
-
-/**
- * @brief 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 last action that happened before our read. Two cases:
- *
- * -# The action is a write: that write must either occur before
- * the write we read from or be the write we read from.
- * -# 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 ModelAction or Promise that curr reads from. Must be a write.
- * @return True if modification order edges were added; false otherwise
- */
-template <typename rf_type>
-bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
-{
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- unsigned int i;
- bool added = false;
- ASSERT(curr->is_read());
-
- /* Last SC fence in the current thread */
- ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
- ModelAction *last_sc_write = NULL;
- if (curr->is_seqcst())
- last_sc_write = get_last_seq_cst_write(curr);
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Last SC fence in thread i */
- ModelAction *last_sc_fence_thread_local = NULL;
- if (int_to_id((int)i) != curr->get_tid())
- last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
-
- /* Last SC fence in thread i, before last SC fence in current thread */
- ModelAction *last_sc_fence_thread_before = NULL;
- if (last_sc_fence_local)
- last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
-
- /* 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;
-
- /* Skip curr */
- if (act == curr)
- continue;
- /* Don't want to add reflexive edges on 'rf' */
- if (act->equals(rf)) {
- if (act->happens_before(curr))
- break;
- else
- continue;
- }
-
- if (act->is_write()) {
- /* C++, Section 29.3 statement 5 */
- if (curr->is_seqcst() && last_sc_fence_thread_local &&
- *act < *last_sc_fence_thread_local) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
- /* C++, Section 29.3 statement 4 */
- else if (act->is_seqcst() && last_sc_fence_local &&
- *act < *last_sc_fence_local) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
- /* C++, Section 29.3 statement 6 */
- else if (last_sc_fence_thread_before &&
- *act < *last_sc_fence_thread_before) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
- }
-
- /* C++, Section 29.3 statement 3 (second subpoint) */
- if (curr->is_seqcst() && last_sc_write && act == last_sc_write) {
- added = mo_graph->addEdge(act, rf) || added;
- break;
- }
-
- /*
- * Include at most one act per-thread that "happens
- * before" curr
- */
- if (act->happens_before(curr)) {
- if (act->is_write()) {
- added = mo_graph->addEdge(act, rf) || added;
- } else {
- const ModelAction *prevrf = act->get_reads_from();
- const Promise *prevrf_promise = act->get_reads_from_promise();
- if (prevrf) {
- if (!prevrf->equals(rf))
- added = mo_graph->addEdge(prevrf, rf) || added;
- } else if (!prevrf_promise->equals(rf)) {
- added = mo_graph->addEdge(prevrf_promise, rf) || added;
- }
- }
- break;
- }
- }
- }
-
- /*
- * All compatible, thread-exclusive promises must be ordered after any
- * concrete loads from the same thread
- */
- for (unsigned int i = 0; i < promises->size(); i++)
- if ((*promises)[i]->is_compatible_exclusive(curr))
- added = mo_graph->addEdge(rf, (*promises)[i]) || added;
-
- return added;
-}
-
-/**
- * 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.
- * @param send_fv A vector for stashing reads to which we may pass our future
- * value. If NULL, then don't record any future values.
- * @return True if modification order edges were added; false otherwise
- */
-bool ModelChecker::w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv)
-{
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, 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_write(curr);
- if (last_seq_cst != NULL) {
- added = mo_graph->addEdge(last_seq_cst, curr) || added;
- }
- }
-
- /* Last SC fence in the current thread */
- ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Last SC fence in thread i, before last SC fence in current thread */
- ModelAction *last_sc_fence_thread_before = NULL;
- if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
- last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
-
- /* 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;
- 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;
- }
-
- /* C++, Section 29.3 statement 7 */
- if (last_sc_fence_thread_before && act->is_write() &&
- *act < *last_sc_fence_thread_before) {
- added = mo_graph->addEdge(act, curr) || added;
- break;
- }
-
- /*
- * Include at most one act per-thread that "happens
- * before" curr
- */
- if (act->happens_before(curr)) {
- /*
- * 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())
- added = mo_graph->addEdge(act, curr) || added;
- else if (act->is_read()) {
- //if previous read accessed a null, just keep going
- if (act->get_reads_from() == NULL)
- continue;
- added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
- }
- break;
- } 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
- (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. Note that
- these checks are overly conservative at this point, we'll
- do more checks before actually removing the
- pendingfuturevalue.
-
- */
- if (send_fv && thin_air_constraint_may_allow(curr, act)) {
- if (!is_infeasible())
- send_fv->push_back(act);
- else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
- add_future_value(curr, act);
- }
- }
- }
- }
-
- /*
- * All compatible, thread-exclusive promises must be ordered after any
- * concrete stores to the same thread, or else they can be merged with
- * this store later
- */
- for (unsigned int i = 0; i < promises->size(); i++)
- if ((*promises)[i]->is_compatible_exclusive(curr))
- added = mo_graph->addEdge(curr, (*promises)[i]) || added;
-
- 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) const
-{
- 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 the following constraint (others
- * require compiler support):
- *
- * If X --hb-> Y --mo-> Z, then X should not read from Z.
- */
-bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
-{
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
- unsigned int i;
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- const ModelAction *write_after_read = NULL;
-
- /* 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;
-
- /* Don't disallow due to act == reader */
- if (!reader->happens_before(act) || reader == act)
- break;
- else if (act->is_write())
- write_after_read = act;
- else if (act->is_read() && act->get_reads_from() != NULL)
- write_after_read = act->get_reads_from();
- }
-
- if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
- return false;
- }
- return true;
-}
-
-/**
- * Finds the head(s) of the release sequence(s) containing a given ModelAction.
- * The ModelAction under consideration is expected to be taking part in
- * 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;
-
- for ( ; rf != NULL; rf = rf->get_reads_from()) {
- ASSERT(rf->is_write());
-
- if (rf->is_release())
- release_heads->push_back(rf);
- else if (rf->get_last_fence_release())
- release_heads->push_back(rf->get_last_fence_release());
- 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 */
- };
- 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 for fence-release in the same thread (29.8, stmt. 3)
- * - check modification order for contiguous subsequence
- * -> rf must be same thread as release */
-
- const ModelAction *fence_release = rf->get_last_fence_release();
- /* Synchronize with a fence-release unconditionally; we don't need to
- * find any more "contiguous subsequence..." for it */
- if (fence_release)
- release_heads->push_back(fence_release);
-
- int tid = id_to_int(rf->get_tid());
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, 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,fence}-release */
- for (; rit != list->rend(); rit++) {
- if (fence_release && *(*rit) < *fence_release)
- break;
- if ((*rit)->is_release())
- break;
- }
- if (rit == list->rend()) {
- /* No write-release in this thread */
- return true; /* complete */
- } else if (fence_release && *(*rit) < *fence_release) {
- /* The fence-release is more recent (and so, "stronger") than
- * the most recent write-release */
- return true; /* complete */
- } /* else, need to establish contiguous release sequence */
- 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)) ||
- !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;
-}
-
-/**
- * An 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 acquire to update its
- * synchronization at some later point in execution.
- *
- * @param acquire The 'acquire' action that may synchronize with a release
- * sequence
- * @param read The read action that may read from a release sequence; this may
- * be the same as acquire, or else an earlier action in the same thread (i.e.,
- * when 'acquire' is a fence-acquire)
- * @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 *acquire,
- ModelAction *read, rel_heads_list_t *release_heads)
-{
- const ModelAction *rf = read->get_reads_from();
- struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
- sequence->acquire = acquire;
- sequence->read = read;
-
- 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;
- SnapVector<struct release_seq *>::iterator it = pending_rel_seqs->begin();
- while (it != pending_rel_seqs->end()) {
- struct release_seq *pending = *it;
- ModelAction *acquire = pending->acquire;
- const ModelAction *read = pending->read;
-
- /* Only resolve sequences on the given location, if provided */
- if (location && read->get_location() != location) {
- it++;
- continue;
- }
-
- const ModelAction *rf = read->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 (!acquire->has_synchronized_with(release_heads[i]))
- if (synchronize(release_heads[i], acquire))
- updated = true;
-
- if (updated) {
- /* Re-check all pending release sequences */
- work_queue->push_back(CheckRelSeqWorkEntry(NULL));
- /* Re-check read-acquire for mo_graph edges */
- if (acquire->is_read())
- 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)) {
- synchronize(acquire, propagate);
- /* 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.
- checkDataRaces();
-
- return updated;
-}
-
-/**
- * Performs various bookkeeping operations for the current ModelAction. For
- * instance, adds action to the per-object, per-thread action vector and to the
- * action trace list of all thread actions.
- *
- * @param act is the ModelAction to add.
- */
-void ModelChecker::add_action_to_lists(ModelAction *act)
-{
- int tid = id_to_int(act->get_tid());
- ModelAction *uninit = NULL;
- int uninit_id = -1;
- action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
- if (list->empty() && act->is_atomic_var()) {
- uninit = get_uninitialized_action(act);
- uninit_id = id_to_int(uninit->get_tid());
- list->push_front(uninit);
- }
- list->push_back(act);
-
- action_trace->push_back(act);
- if (uninit)
- action_trace->push_front(uninit);
-
- SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
- if (tid >= (int)vec->size())
- vec->resize(priv->next_thread_id);
- (*vec)[tid].push_back(act);
- if (uninit)
- (*vec)[uninit_id].push_front(uninit);
-
- if ((int)thrd_last_action->size() <= tid)
- thrd_last_action->resize(get_num_threads());
- (*thrd_last_action)[tid] = act;
- if (uninit)
- (*thrd_last_action)[uninit_id] = uninit;
-
- if (act->is_fence() && act->is_release()) {
- if ((int)thrd_last_fence_release->size() <= tid)
- thrd_last_fence_release->resize(get_num_threads());
- (*thrd_last_fence_release)[tid] = act;
- }
-
- if (act->is_wait()) {
- void *mutex_loc = (void *) act->get_value();
- get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
-
- SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
- if (tid >= (int)vec->size())
- vec->resize(priv->next_thread_id);
- (*vec)[tid].push_back(act);
- }
-}
-
-/**
- * @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())
- return (*thrd_last_action)[id_to_int(tid)];
- else
- return NULL;
-}
-
-/**
- * @brief Get the last fence release performed by a particular Thread
- * @param tid The thread ID of the Thread in question
- * @return The last fence release in the thread, if one exists; NULL otherwise
- */
-ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
-{
- int threadid = id_to_int(tid);
- if (threadid < (int)thrd_last_fence_release->size())
- return (*thrd_last_fence_release)[id_to_int(tid)];
- else
- return NULL;
-}
-
-/**
- * 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_write(ModelAction *curr) const
-{
- void *location = curr->get_location();
- action_list_t *list = get_safe_ptr_action(obj_map, location);
- /* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); (*rit) != curr; rit++)
- ;
- rit++; /* Skip past curr */
- for ( ; rit != list->rend(); rit++)
- if ((*rit)->is_write() && (*rit)->is_seqcst())
- return *rit;
- return NULL;
-}
-
-/**
- * Gets the last memory_order_seq_cst fence (in the total global sequence)
- * performed in a particular thread, prior to a particular fence.
- * @param tid The ID of the thread to check
- * @param before_fence The fence from which to begin the search; if NULL, then
- * search for the most recent fence in the thread.
- * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
- */
-ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
-{
- /* All fences should have NULL location */
- action_list_t *list = get_safe_ptr_action(obj_map, NULL);
- action_list_t::reverse_iterator rit = list->rbegin();
-
- if (before_fence) {
- for (; rit != list->rend(); rit++)
- if (*rit == before_fence)
- break;
-
- ASSERT(*rit == before_fence);
- rit++;
- }
-
- for (; rit != list->rend(); rit++)
- if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
- 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 = get_safe_ptr_action(obj_map, 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;
-}
-
-ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
-{
- ModelAction *parent = get_last_action(tid);
- if (!parent)
- parent = get_thread(tid)->get_creation();
- return parent;
-}
-
-/**
- * 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) const
-{
- return get_parent_action(tid)->get_cv();
-}
-
-/**
- * @brief Find the promise (if any) to resolve for the current action and
- * remove it from the pending promise vector
- * @param curr The current ModelAction. Should be a write.
- * @return The Promise to resolve, if any; otherwise NULL
- */
-Promise * ModelChecker::pop_promise_to_resolve(const ModelAction *curr)
-{
- for (unsigned int i = 0; i < promises->size(); i++)
- if (curr->get_node()->get_promise(i)) {
- Promise *ret = (*promises)[i];
- promises->erase(promises->begin() + i);
- return ret;
- }
- return NULL;
-}
-
-/**
- * Resolve a Promise with a current write.
- * @param write The ModelAction that is fulfilling Promises
- * @param promise The Promise to resolve
- * @return True if the Promise was successfully resolved; false otherwise
- */
-bool ModelChecker::resolve_promise(ModelAction *write, Promise *promise)
-{
- ModelVector<ModelAction *> actions_to_check;
-
- for (unsigned int i = 0; i < promise->get_num_readers(); i++) {
- ModelAction *read = promise->get_reader(i);
- read_from(read, write);
- actions_to_check.push_back(read);
- }
- /* Make sure the promise's value matches the write's value */
- ASSERT(promise->is_compatible(write) && promise->same_value(write));
- if (!mo_graph->resolvePromise(promise, write))
- priv->failed_promise = true;
-
- /**
- * @todo It is possible to end up in an inconsistent state, where a
- * "resolved" promise may still be referenced if
- * CycleGraph::resolvePromise() failed, so don't delete 'promise'.
- *
- * Note that the inconsistency only matters when dumping mo_graph to
- * file.
- *
- * delete promise;
- */
-
- //Check whether reading these writes has made threads unable to
- //resolve promises
- for (unsigned int i = 0; i < actions_to_check.size(); i++) {
- ModelAction *read = actions_to_check[i];
- mo_check_promises(read, true);
- }
-
- return true;
-}
-
-/**
- * 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];
- if (!promise->is_compatible(curr) || !promise->same_value(curr))
- continue;
-
- bool satisfy = true;
- for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
- const ModelAction *act = promise->get_reader(j);
- if (act->happens_before(curr) ||
- act->could_synchronize_with(curr)) {
- satisfy = false;
- break;
- }
- }
- if (satisfy)
- curr->get_node()->set_promise(i);
- }
-}
-
-/** Checks promises in response to change in ClockVector Threads. */
-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];
- if (!promise->thread_is_available(tid))
- continue;
- for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
- const ModelAction *act = promise->get_reader(j);
- if ((!old_cv || !old_cv->synchronized_since(act)) &&
- merge_cv->synchronized_since(act)) {
- if (promise->eliminate_thread(tid)) {
- /* Promise has failed */
- priv->failed_promise = true;
- return;
- }
- }
- }
- }
-}
-
-void ModelChecker::check_promises_thread_disabled()
-{
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
- if (promise->has_failed()) {
- priv->failed_promise = true;
- return;
- }
- }
-}
-
-/**
- * @brief Checks promises in response to addition to modification order for
- * threads.
- *
- * We test whether threads are still available for satisfying promises after an
- * addition to our modification order constraints. Those that are unavailable
- * are "eliminated". Once all threads are eliminated from satisfying a promise,
- * that promise has failed.
- *
- * @param act The ModelAction which updated the modification order
- * @param is_read_check Should be true if act is a read and we must check for
- * updates to the store from which it read (there is a distinction here for
- * RMW's, which are both a load and a store)
- */
-void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
-{
- const ModelAction *write = is_read_check ? act->get_reads_from() : act;
-
- for (unsigned int i = 0; i < promises->size(); i++) {
- Promise *promise = (*promises)[i];
-
- // Is this promise on the same location?
- if (!promise->same_location(write))
- continue;
-
- for (unsigned int j = 0; j < promise->get_num_readers(); j++) {
- const ModelAction *pread = promise->get_reader(j);
- if (!pread->happens_before(act))
- continue;
- if (mo_graph->checkPromise(write, promise)) {
- priv->failed_promise = true;
- return;
- }
- break;
- }
-
- // Don't do any lookups twice for the same thread
- if (!promise->thread_is_available(act->get_tid()))
- continue;
-
- if (mo_graph->checkReachable(promise, write)) {
- if (mo_graph->checkPromise(write, promise)) {
- priv->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, as well as any previously-observed future values that must still be valid.
- *
- * @param curr is the current ModelAction that we are exploring; it must be a
- * 'read' operation.
- */
-void ModelChecker::build_may_read_from(ModelAction *curr)
-{
- SnapVector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
- unsigned int i;
- ASSERT(curr->is_read());
-
- ModelAction *last_sc_write = NULL;
-
- if (curr->is_seqcst())
- last_sc_write = get_last_seq_cst_write(curr);
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
-
- /* Only consider 'write' actions */
- if (!act->is_write() || act == curr)
- continue;
-
- /* Don't consider more than one seq_cst write if we are a seq_cst read. */
- bool allow_read = true;
-
- if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
- allow_read = false;
- else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
- allow_read = false;
-
- if (allow_read) {
- /* Only add feasible reads */
- mo_graph->startChanges();
- r_modification_order(curr, act);
- if (!is_infeasible())
- curr->get_node()->add_read_from_past(act);
- mo_graph->rollbackChanges();
- }
-
- /* Include at most one act per-thread that "happens before" curr */
- if (act->happens_before(curr))
- break;
- }
- }
-
- /* Inherit existing, promised future values */
- for (i = 0; i < promises->size(); i++) {
- const Promise *promise = (*promises)[i];
- const ModelAction *promise_read = promise->get_reader(0);
- if (promise_read->same_var(curr)) {
- /* Only add feasible future-values */
- mo_graph->startChanges();
- r_modification_order(curr, promise);
- if (!is_infeasible())
- curr->get_node()->add_read_from_promise(promise_read);
- mo_graph->rollbackChanges();
- }
- }
-
- /* We may find no valid may-read-from only if the execution is doomed */
- if (!curr->get_node()->read_from_size()) {
- priv->no_valid_reads = true;
- set_assert();
- }
-
- if (DBG_ENABLED()) {
- model_print("Reached read action:\n");
- curr->print();
- model_print("Printing read_from_past\n");
- curr->get_node()->print_read_from_past();
- model_print("End printing read_from_past\n");
- }
-}
-
-bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
-{
- for ( ; write != NULL; write = write->get_reads_from()) {
- /* UNINIT actions don't have a Node, and they never sleep */
- if (write->is_uninitialized())
- return true;
- Node *prevnode = write->get_node()->get_parent();
-
- bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
- if (write->is_release() && thread_sleep)
- return true;
- if (!write->is_rmw())
- return false;
- }
- return true;
-}
-
-/**
- * @brief Get an action representing an uninitialized atomic
- *
- * This function may create a new one or try to retrieve one from the NodeStack
- *
- * @param curr The current action, which prompts the creation of an UNINIT action
- * @return A pointer to the UNINIT ModelAction
- */
-ModelAction * ModelChecker::get_uninitialized_action(const ModelAction *curr) const
-{
- Node *node = curr->get_node();
- ModelAction *act = node->get_uninit_action();
- if (!act) {
- act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), model->params.uninitvalue, model_thread);
- node->set_uninit_action(act);
- }
- act->create_cv(NULL);
- return act;
-}
-
-static void print_list(action_list_t *list)
-{
- action_list_t::iterator it;
-
- model_print("---------------------------------------------------------------------\n");
-
- unsigned int hash = 0;
-
- for (it = list->begin(); it != list->end(); it++) {
- const ModelAction *act = *it;
- if (act->get_seq_number() > 0)
- act->print();
- hash = hash^(hash<<3)^((*it)->hash());
- }
- model_print("HASH %u\n", hash);
- model_print("---------------------------------------------------------------------\n");
-}
-
-#if SUPPORT_MOD_ORDER_DUMP
-void ModelChecker::dumpGraph(char *filename) const
-{
- 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 *act = *it;
- if (act->is_read()) {
- mo_graph->dot_print_node(file, act);
- if (act->get_reads_from())
- mo_graph->dot_print_edge(file,
- act->get_reads_from(),
- act,
- "label=\"rf\", color=red, weight=2");
- else
- mo_graph->dot_print_edge(file,
- act->get_reads_from_promise(),
- act,
- "label=\"rf\", color=red");
- }
- if (thread_array[act->get_tid()]) {
- mo_graph->dot_print_edge(file,
- thread_array[id_to_int(act->get_tid())],
- act,
- "label=\"sb\", color=blue, weight=400");
- }
-
- thread_array[act->get_tid()] = act;
- }
- fprintf(file, "}\n");
- model_free(thread_array);
- fclose(file);
-}
-#endif
-
-/** @brief Prints an execution trace summary. */
-void ModelChecker::print_summary() const
-{
-#if SUPPORT_MOD_ORDER_DUMP
- char buffername[100];
- sprintf(buffername, "exec%04u", stats.num_total);
- mo_graph->dumpGraphToFile(buffername);
- sprintf(buffername, "graph%04u", stats.num_total);
- dumpGraph(buffername);
-#endif
-
- model_print("Execution %d:", stats.num_total);
- if (isfeasibleprefix()) {
- if (scheduler->all_threads_sleeping())
- model_print(" SLEEP-SET REDUNDANT");
- model_print("\n");
- } else
- print_infeasibility(" INFEASIBLE");
- print_list(action_trace);
- model_print("\n");
- if (!promises->empty()) {
- model_print("Pending promises:\n");
- for (unsigned int i = 0; i < promises->size(); i++) {
- model_print(" [P%u] ", i);
- (*promises)[i]->print();
- }
- model_print("\n");
- }
-}
-
-/**
- * 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->put(id_to_int(t->get_id()), t);
- scheduler->add_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(const ModelAction *act) const
-{
- return get_thread(act->get_tid());
-}
-
-/**
- * @brief Get a Promise's "promise number"
- *
- * A "promise number" is an index number that is unique to a promise, valid
- * only for a specific snapshot of an execution trace. Promises may come and go
- * as they are generated an resolved, so an index only retains meaning for the
- * current snapshot.
- *
- * @param promise The Promise to check
- * @return The promise index, if the promise still is valid; otherwise -1
- */
-int ModelChecker::get_promise_number(const Promise *promise) const
-{
- for (unsigned int i = 0; i < promises->size(); i++)
- if ((*promises)[i] == promise)
- return i;
- /* Not found */
- return -1;
-}
-
-/**
- * @brief Check if a Thread is currently enabled
- * @param t The Thread to check
- * @return True if the Thread is currently enabled
- */
-bool ModelChecker::is_enabled(Thread *t) const
-{
- return scheduler->is_enabled(t);
-}
-
-/**
- * @brief Check if a Thread is currently enabled
- * @param tid The ID of the Thread to check
- * @return True if the Thread is currently enabled
- */
-bool ModelChecker::is_enabled(thread_id_t tid) const
-{
- return scheduler->is_enabled(tid);
-}
-
-/**
- * Switch from a model-checker context to a user-thread context. This is the
- * complement of ModelChecker::switch_to_master and must be called from the
- * model-checker context
- *
- * @param thread The user-thread to switch to
- */
-void ModelChecker::switch_from_master(Thread *thread)
-{
- scheduler->set_current_thread(thread);
- Thread::swap(&system_context, thread);
-}
-
-/**
- * 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 only if
- * trace is exiting via an assertion (see ModelChecker::set_assert and
- * ModelChecker::has_asserted).
- * @return Return the value returned by the current action
- */
-uint64_t ModelChecker::switch_to_master(ModelAction *act)
-{
- DBG();
- Thread *old = thread_current();
- scheduler->set_current_thread(NULL);
- ASSERT(!old->get_pending());
- old->set_pending(act);
- if (Thread::swap(old, &system_context) < 0) {
- perror("swap threads");
- exit(EXIT_FAILURE);
- }
- return old->get_return_value();
-}
-
-/**
- * Takes the next step in the execution, if possible.
- * @param curr The current step to take
- * @return Returns the next Thread to run, if any; NULL if this execution
- * should terminate
- */
-Thread * ModelChecker::take_step(ModelAction *curr)
-{
- Thread *curr_thrd = get_thread(curr);
- ASSERT(curr_thrd->get_state() == THREAD_READY);
-
- ASSERT(check_action_enabled(curr)); /* May have side effects? */
- curr = check_current_action(curr);
- ASSERT(curr);
-
- if (curr_thrd->is_blocked() || curr_thrd->is_complete())
- scheduler->remove_thread(curr_thrd);
-
- return action_select_next_thread(curr);
-}
-
-/** Wrapper to run the user's main function, with appropriate arguments */
-void user_main_wrapper(void *)
-{
- user_main(model->params.argc, model->params.argv);
-}
-
-/** @return True if the execution has taken too many steps */
-bool ModelChecker::too_many_steps() const
-{
- return params.bound != 0 && priv->used_sequence_numbers > params.bound;
-}
-
-bool ModelChecker::should_terminate_execution()
-{
- /* Infeasible -> don't take any more steps */
- if (is_infeasible())
- return true;
- else if (isfeasibleprefix() && have_bug_reports()) {
- set_assert();
- return true;
- }
-
- if (too_many_steps())
- return true;
- return false;
-}
-
-/** @brief Run ModelChecker for the user program */
-void ModelChecker::run()
-{
- do {
- thrd_t user_thread;
- Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
- add_thread(t);
+ do {
+ thrd_t user_thread;
+ Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
+ execution->add_thread(t);
do {
/*
* thread which just took a step--plus the first step
* for any newly-created thread
*/
- for (unsigned int i = 0; i < get_num_threads(); i++) {
+ for (unsigned int i = 0; i < execution->get_num_threads(); i++) {
thread_id_t tid = int_to_id(i);
Thread *thr = get_thread(tid);
if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
for (unsigned int i = 0; i < get_num_threads(); i++) {
Thread *th = get_thread(int_to_id(i));
ModelAction *act = th->get_pending();
- if (act && is_enabled(th) && !check_action_enabled(act)) {
+ if (act && is_enabled(th) && !execution->check_action_enabled(act)) {
scheduler->sleep(th);
}
}
/* Catch assertions from prior take_step or from
* between-ModelAction bugs (e.g., data races) */
- if (has_asserted())
+ if (execution->has_asserted())
break;
if (!t)
/* Consume the next action for a Thread */
ModelAction *curr = t->get_pending();
t->set_pending(NULL);
- t = take_step(curr);
+ t = execution->take_step(curr);
} while (!should_terminate_execution());
- /*
- * Launch end-of-execution release sequence fixups only when
- * the execution is otherwise feasible AND there are:
- *
- * (1) pending release sequences
- * (2) pending assertions that could be invalidated by a change
- * in clock vectors (i.e., data races)
- * (3) no pending promises
- */
- while (!pending_rel_seqs->empty() &&
- is_feasible_prefix_ignore_relseq() &&
- !unrealizedraces.empty()) {
- model_print("*** WARNING: release sequence fixup action "
- "(%zu pending release seuqence(s)) ***\n",
- pending_rel_seqs->size());
- ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
- std::memory_order_seq_cst, NULL, VALUE_NONE,
- model_thread);
- take_step(fixup);
- };
} while (next_execution());
+ execution->fixup_release_sequences();
+
model_print("******* Model-checking complete: *******\n");
print_stats();
}
#include "mymemory.h"
#include "hashtable.h"
-#include "workqueue.h"
#include "config.h"
#include "modeltypes.h"
#include "stl-model.h"
class Thread;
class ClockVector;
class TraceAnalysis;
-struct model_snapshot_members;
+class ModelExecution;
+class ModelAction;
-/** @brief Shorthand for a list of release sequence heads */
-typedef ModelVector<const ModelAction *> rel_heads_list_t;
typedef SnapList<ModelAction *> action_list_t;
/** @brief Model checker execution stats */
int num_redundant; /**< @brief Number of redundant, aborted executions */
};
-struct PendingFutureValue {
- PendingFutureValue(ModelAction *writer, ModelAction *reader) :
- writer(writer), reader(reader)
- { }
- const ModelAction *writer;
- ModelAction *reader;
-};
-
-/** @brief Records information regarding a single pending release sequence */
-struct release_seq {
- /** @brief The acquire operation */
- ModelAction *acquire;
- /** @brief The read operation that may read from a release sequence;
- * may be the same as acquire, or else an earlier action in the same
- * thread (i.e., when 'acquire' is a fence-acquire) */
- const ModelAction *read;
- /** @brief The head of the RMW chain from which 'read' reads; may be
- * equal to 'release' */
- const ModelAction *rf;
- /** @brief The head of the potential longest release sequence chain */
- const ModelAction *release;
- /** @brief The write(s) that may break the release sequence */
- SnapVector<const ModelAction *> writes;
-};
-
/** @brief The central structure for model-checking */
class ModelChecker {
public:
/** @returns the context for the main model-checking system thread */
ucontext_t * get_system_context() { return &system_context; }
- void print_summary() const;
-#if SUPPORT_MOD_ORDER_DUMP
- void dumpGraph(char *filename) const;
-#endif
-
Thread * get_thread(thread_id_t tid) const;
Thread * get_thread(const ModelAction *act) const;
int get_promise_number(const Promise *promise) const;
private:
/** The scheduler to use: tracks the running/ready Threads */
Scheduler * const scheduler;
+ NodeStack * const node_stack;
+ ModelExecution *execution;
- void add_thread(Thread *t);
-
- bool sleep_can_read_from(ModelAction *curr, const ModelAction *write);
- bool thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader) const;
- bool mo_may_allow(const ModelAction *writer, const ModelAction *reader);
- bool promises_may_allow(const ModelAction *writer, const ModelAction *reader) const;
- bool has_asserted() const;
- void set_assert();
- void set_bad_synchronization();
- bool promises_expired() const;
void execute_sleep_set();
- bool should_wake_up(const ModelAction *curr, const Thread *thread) const;
- void wake_up_sleeping_actions(ModelAction *curr);
- modelclock_t get_next_seq_num();
bool next_execution();
- ModelAction * check_current_action(ModelAction *curr);
- bool initialize_curr_action(ModelAction **curr);
- bool process_read(ModelAction *curr);
- bool process_write(ModelAction *curr);
- bool process_fence(ModelAction *curr);
- bool process_mutex(ModelAction *curr);
- bool process_thread_action(ModelAction *curr);
- void process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue);
- bool read_from(ModelAction *act, const ModelAction *rf);
- bool synchronize(const ModelAction *first, ModelAction *second);
- bool check_action_enabled(ModelAction *curr);
-
- Thread * take_step(ModelAction *curr);
bool should_terminate_execution();
- template <typename T>
- bool check_recency(ModelAction *curr, const T *rf) const;
-
- template <typename T, typename U>
- bool should_read_instead(const ModelAction *curr, const T *rf, const U *other_rf) const;
-
- ModelAction * get_last_fence_conflict(ModelAction *act) const;
- ModelAction * get_last_conflict(ModelAction *act) const;
- void set_backtracking(ModelAction *act);
- Thread * action_select_next_thread(const ModelAction *curr) const;
Thread * get_next_thread();
- bool set_latest_backtrack(ModelAction *act);
- ModelAction * get_next_backtrack();
void reset_to_initial_state();
- Promise * pop_promise_to_resolve(const ModelAction *curr);
- bool resolve_promise(ModelAction *curr, Promise *promise);
- void compute_promises(ModelAction *curr);
- void compute_relseq_breakwrites(ModelAction *curr);
-
- void check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv);
- void mo_check_promises(const ModelAction *act, bool is_read_check);
- void thread_blocking_check_promises(Thread *blocker, Thread *waiting);
-
- void check_curr_backtracking(ModelAction *curr);
- void add_action_to_lists(ModelAction *act);
- ModelAction * get_last_fence_release(thread_id_t tid) const;
- ModelAction * get_last_seq_cst_write(ModelAction *curr) const;
- ModelAction * get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const;
- ModelAction * get_last_unlock(ModelAction *curr) const;
- void build_may_read_from(ModelAction *curr);
- ModelAction * process_rmw(ModelAction *curr);
- template <typename rf_type>
- bool r_modification_order(ModelAction *curr, const rf_type *rf);
-
- bool w_modification_order(ModelAction *curr, ModelVector<ModelAction *> *send_fv);
- void get_release_seq_heads(ModelAction *acquire, ModelAction *read, rel_heads_list_t *release_heads);
- bool release_seq_heads(const ModelAction *rf, rel_heads_list_t *release_heads, struct release_seq *pending) const;
- bool resolve_release_sequences(void *location, work_queue_t *work_queue);
- void add_future_value(const ModelAction *writer, ModelAction *reader);
-
- ModelAction * get_uninitialized_action(const ModelAction *curr) const;
ModelAction *diverge;
ModelAction *earliest_diverge;
ucontext_t system_context;
- action_list_t * const action_trace;
- HashTable<int, Thread *, int> * const thread_map;
-
- /** Per-object list of actions. Maps an object (i.e., memory location)
- * to a trace of all actions performed on the object. */
- HashTable<const void *, action_list_t *, uintptr_t, 4> * const obj_map;
-
- /** Per-object list of actions. Maps an object (i.e., memory location)
- * to a trace of all actions performed on the object. */
- HashTable<const void *, action_list_t *, uintptr_t, 4> * const condvar_waiters_map;
-
- HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4 > * const obj_thrd_map;
- SnapVector<Promise *> * const promises;
- SnapVector<struct PendingFutureValue> * const futurevalues;
-
- /**
- * List of pending release sequences. Release sequences might be
- * determined lazily as promises are fulfilled and modification orders
- * are established. Each entry in the list may only be partially
- * filled, depending on its pending status.
- */
- SnapVector<struct release_seq *> * const pending_rel_seqs;
- SnapVector<ModelAction *> * const thrd_last_action;
- SnapVector<ModelAction *> * const thrd_last_fence_release;
- NodeStack * const node_stack;
ModelVector<TraceAnalysis *> * trace_analyses;
-
- /** Private data members that should be snapshotted. They are grouped
- * together for efficiency and maintainability. */
- struct model_snapshot_members * const priv;
-
- /** A special model-checker Thread; used for associating with
- * model-checker-related ModelAcitons */
- Thread *model_thread;
-
- /**
- * @brief The modification order graph
- *
- * A directed acyclic graph recording observations of the modification
- * order on all the atomic objects in the system. This graph should
- * never contain any cycles, as that represents a violation of the
- * memory model (total ordering). This graph really consists of many
- * disjoint (unconnected) subgraphs, each graph corresponding to a
- * separate ordering on a distinct object.
- *
- * The edges in this graph represent the "ordered before" relation,
- * such that <tt>a --> b</tt> means <tt>a</tt> was ordered before
- * <tt>b</tt>.
- */
- CycleGraph * const mo_graph;
-
/** @brief The cumulative execution stats */
struct execution_stats stats;
void record_stats();
void run_trace_analyses();
- void print_infeasibility(const char *prefix) const;
- bool is_feasible_prefix_ignore_relseq() const;
- bool is_infeasible() const;
- bool is_deadlocked() const;
- bool too_many_steps() const;
- bool is_complete_execution() const;
- bool have_bug_reports() const;
void print_bugs() const;
void print_execution(bool printbugs) const;
void print_stats() const;
projects / model-checker.git / commitdiff