Bug fix
[c11tester.git] / execution.cc
index 7d38eb43f3f721a99017d2e05d8ce243e9e4efde..504f7f52a6ee2c40c551f23d49c63d90bb6b485f 100644 (file)
@@ -6,7 +6,6 @@
 #include "model.h"
 #include "execution.h"
 #include "action.h"
-#include "nodestack.h"
 #include "schedule.h"
 #include "common.h"
 #include "clockvector.h"
 #include "datarace.h"
 #include "threads-model.h"
 #include "bugmessage.h"
+#include "history.h"
+#include "fuzzer.h"
+#include "newfuzzer.h"
 
-#define INITIAL_THREAD_ID      0
+#define INITIAL_THREAD_ID       0
 
 /**
  * Structure for holding small ModelChecker members that should be snapshotted
@@ -25,67 +27,59 @@ struct 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(),
-               too_many_reads(false),
-               no_valid_reads(false),
-               bad_synchronization(false),
-               bad_sc_read(false),
                asserted(false)
        { }
 
        ~model_snapshot_members() {
-               for (unsigned int i = 0; i < bugs.size(); i++)
+               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;
-       bool too_many_reads;
-       bool no_valid_reads;
        /** @brief Incorrectly-ordered synchronization was made */
-       bool bad_synchronization;
-       bool bad_sc_read;
        bool asserted;
 
        SNAPSHOTALLOC
 };
 
 /** @brief Constructor */
-ModelExecution::ModelExecution(ModelChecker *m,
-               Scheduler *scheduler,
-               NodeStack *node_stack) :
+ModelExecution::ModelExecution(ModelChecker *m, Scheduler *scheduler) :
        model(m),
        params(NULL),
        scheduler(scheduler),
-       action_trace(),
-       thread_map(2), /* We'll always need at least 2 threads */
+       thread_map(2),  /* We'll always need at least 2 threads */
        pthread_map(0),
-       pthread_counter(0),
+       pthread_counter(1),
+       action_trace(),
        obj_map(),
        condvar_waiters_map(),
        obj_thrd_map(),
        mutex_map(),
        thrd_last_action(1),
        thrd_last_fence_release(),
-       node_stack(node_stack),
-       priv(new struct model_snapshot_members()),
-       mo_graph(new CycleGraph())
+       priv(new struct model_snapshot_members ()),
+       mo_graph(new CycleGraph()),
+       fuzzer(new Fuzzer()),
+       isfinished(false)
 {
        /* Initialize a model-checker thread, for special ModelActions */
        model_thread = new Thread(get_next_id());
        add_thread(model_thread);
+       fuzzer->register_engine(this);
        scheduler->register_engine(this);
-       node_stack->register_engine(this);
+#ifdef TLS
+       pthread_key_create(&pthreadkey, tlsdestructor);
+#endif
 }
 
 /** @brief Destructor */
 ModelExecution::~ModelExecution()
 {
-       for (unsigned int i = 0; i < get_num_threads(); i++)
+       for (unsigned int i = 0;i < get_num_threads();i++)
                delete get_thread(int_to_id(i));
 
        delete mo_graph;
@@ -97,7 +91,7 @@ int ModelExecution::get_execution_number() const
        return model->get_execution_number();
 }
 
-static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
+static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 2> * hash, void * ptr)
 {
        action_list_t *tmp = hash->get(ptr);
        if (tmp == NULL) {
@@ -107,7 +101,7 @@ static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t
        return tmp;
 }
 
-static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
+static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<action_list_t> *, uintptr_t, 2> * hash, void * ptr)
 {
        SnapVector<action_list_t> *tmp = hash->get(ptr);
        if (tmp == NULL) {
@@ -117,18 +111,6 @@ static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, Sn
        return tmp;
 }
 
-action_list_t * ModelExecution::get_actions_on_obj(void * obj, thread_id_t tid) const
-{
-       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()
 {
@@ -147,6 +129,18 @@ modelclock_t ModelExecution::get_next_seq_num()
        return ++priv->used_sequence_numbers;
 }
 
+/** @return a sequence number for a new ModelAction */
+modelclock_t ModelExecution::get_curr_seq_num()
+{
+       return priv->used_sequence_numbers;
+}
+
+/** Restore the last used sequence number when actions of a thread are postponed by Fuzzer */
+void ModelExecution::restore_last_seq_num()
+{
+       priv->used_sequence_numbers--;
+}
+
 /**
  * @brief Should the current action wake up a given thread?
  *
@@ -172,44 +166,34 @@ bool ModelExecution::should_wake_up(const ModelAction *curr, const Thread *threa
                if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
                        return true;
        }
+       /* The sleep is literally sleeping */
+       if (asleep->is_sleep()) {
+               if (fuzzer->shouldWake(asleep))
+                       return true;
+       }
+
        return false;
 }
 
 void ModelExecution::wake_up_sleeping_actions(ModelAction *curr)
 {
-       for (unsigned int i = 0; i < get_num_threads(); i++) {
+       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))
+                       if (should_wake_up(curr, thr)) {
                                /* Remove this thread from sleep set */
                                scheduler->remove_sleep(thr);
+                               if (thr->get_pending()->is_sleep())
+                                       thr->set_wakeup_state(true);
+                       }
                }
        }
 }
 
-/** @brief Alert the model-checker that an incorrectly-ordered
- * synchronization was made */
-void ModelExecution::set_bad_synchronization()
-{
-       priv->bad_synchronization = true;
-}
-
-/** @brief Alert the model-checker that an incorrectly-ordered
- * synchronization was made */
-void ModelExecution::set_bad_sc_read()
-{
-       priv->bad_sc_read = true;
-}
-
-bool ModelExecution::assert_bug(const char *msg)
+void ModelExecution::assert_bug(const char *msg)
 {
        priv->bugs.push_back(new bug_message(msg));
-
-       if (isfeasibleprefix()) {
-               set_assert();
-               return true;
-       }
-       return false;
+       set_assert();
 }
 
 /** @return True, if any bugs have been reported for this execution */
@@ -254,7 +238,7 @@ void ModelExecution::set_assert()
 bool ModelExecution::is_deadlocked() const
 {
        bool blocking_threads = false;
-       for (unsigned int i = 0; i < get_num_threads(); i++) {
+       for (unsigned int i = 0;i < get_num_threads();i++) {
                thread_id_t tid = int_to_id(i);
                if (is_enabled(tid))
                        return false;
@@ -274,34 +258,74 @@ bool ModelExecution::is_deadlocked() const
  */
 bool ModelExecution::is_complete_execution() const
 {
-       for (unsigned int i = 0; i < get_num_threads(); i++)
+       for (unsigned int i = 0;i < get_num_threads();i++)
                if (is_enabled(int_to_id(i)))
                        return false;
        return true;
 }
 
+ModelAction * ModelExecution::convertNonAtomicStore(void * location) {
+       uint64_t value = *((const uint64_t *) location);
+       modelclock_t storeclock;
+       thread_id_t storethread;
+       getStoreThreadAndClock(location, &storethread, &storeclock);
+       setAtomicStoreFlag(location);
+       ModelAction * act = new ModelAction(NONATOMIC_WRITE, memory_order_relaxed, location, value, get_thread(storethread));
+       act->set_seq_number(storeclock);
+       add_normal_write_to_lists(act);
+       add_write_to_lists(act);
+       w_modification_order(act);
+       model->get_history()->process_action(act, act->get_tid());
+       return act;
+}
 
 /**
  * Processes a read model action.
  * @param curr is the read model action to process.
  * @param rf_set is the set of model actions we can possibly read from
- * @return True if processing this read updates the mo_graph.
+ * @return True if the read can be pruned from the thread map list.
  */
-bool ModelExecution::process_read(ModelAction *curr, ModelVector<ModelAction *> * rf_set)
+bool ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> * rf_set)
 {
-       int random_index = random() % rf_set->size();
-       bool updated = false;
-               
-       const ModelAction *rf = (*rf_set)[random_index];
-       ASSERT(rf);
-       
-       mo_graph->startChanges();
-       
-       updated = r_modification_order(curr, rf);
-       read_from(curr, rf);
-       mo_graph->commitChanges();
-       get_thread(curr)->set_return_value(curr->get_return_value());
-       return updated;
+       SnapVector<ModelAction *> * priorset = new SnapVector<ModelAction *>();
+       bool hasnonatomicstore = hasNonAtomicStore(curr->get_location());
+       if (hasnonatomicstore) {
+               ModelAction * nonatomicstore = convertNonAtomicStore(curr->get_location());
+               rf_set->push_back(nonatomicstore);
+       }
+
+       // Remove writes that violate read modification order
+       /*
+          uint i = 0;
+          while (i < rf_set->size()) {
+               ModelAction * rf = (*rf_set)[i];
+               if (!r_modification_order(curr, rf, NULL, NULL, true)) {
+                       (*rf_set)[i] = rf_set->back();
+                       rf_set->pop_back();
+               } else
+                       i++;
+          }*/
+
+       while(true) {
+               int index = fuzzer->selectWrite(curr, rf_set);
+
+               ModelAction *rf = (*rf_set)[index];
+
+               ASSERT(rf);
+               bool canprune = false;
+               if (r_modification_order(curr, rf, priorset, &canprune)) {
+                       for(unsigned int i=0;i<priorset->size();i++) {
+                               mo_graph->addEdge((*priorset)[i], rf);
+                       }
+                       read_from(curr, rf);
+                       get_thread(curr)->set_return_value(curr->get_return_value());
+                       delete priorset;
+                       return canprune && (curr->get_type() == ATOMIC_READ);
+               }
+               priorset->clear();
+               (*rf_set)[index] = rf_set->back();
+               rf_set->pop_back();
+       }
 }
 
 /**
@@ -338,10 +362,11 @@ bool ModelExecution::process_mutex(ModelAction *curr)
                }
                get_thread(curr)->set_return_value(1);
        }
-               //otherwise fall into the lock case
+       //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");
+               //TODO: FIND SOME BETTER WAY TO CHECK LOCK INITIALIZED OR NOT
+               //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
@@ -351,10 +376,40 @@ bool ModelExecution::process_mutex(ModelAction *curr)
                }
                break;
        }
-       case ATOMIC_WAIT:
+       case ATOMIC_WAIT: {
+               //TODO: DOESN'T REALLY IMPLEMENT SPURIOUS WAKEUPS CORRECTLY
+               if (fuzzer->shouldWait(curr)) {
+                       /* 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;
+
+                       /* disable this thread */
+                       get_safe_ptr_action(&condvar_waiters_map, curr->get_location())->push_back(curr);
+                       scheduler->sleep(get_thread(curr));
+               }
+
+               break;
+       }
+       case ATOMIC_TIMEDWAIT:
        case ATOMIC_UNLOCK: {
+               //TODO: FIX WAIT SITUATION...WAITS CAN SPURIOUSLY
+               //FAIL...TIMED WAITS SHOULD PROBABLY JUST BE THE SAME
+               //AS NORMAL WAITS...THINK ABOUT PROBABILITIES
+               //THOUGH....AS IN TIMED WAIT MUST FAIL TO GUARANTEE
+               //PROGRESS...NORMAL WAIT MAY FAIL...SO NEED NORMAL
+               //WAIT TO WORK CORRECTLY IN THE CASE IT SPURIOUSLY
+               //FAILS AND IN THE CASE IT DOESN'T...  TIMED WAITS
+               //MUST EVENMTUALLY RELEASE...
+
                /* wake up the other threads */
-               for (unsigned int i = 0; i < get_num_threads(); i++) {
+               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())
@@ -363,37 +418,23 @@ bool ModelExecution::process_mutex(ModelAction *curr)
 
                /* 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 */
-
                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));
+               for (sllnode<ModelAction *> * rit = waiters->begin();rit != NULL;rit=rit->getNext()) {
+                       scheduler->wake(get_thread(rit->getVal()));
                }
                waiters->clear();
                break;
        }
        case ATOMIC_NOTIFY_ONE: {
                action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
-
-               //BCD -- TOFIX FUZZER
-               //THIS SHOULD BE A RANDOM CHOICE
-               //              int wakeupthread = curr->get_node()->get_misc();
-               int wakeupthread = 0;
-               action_list_t::iterator it = waiters->begin();
-
-               // WL
-               if (it == waiters->end())
-                       break;
-
-               advance(it, wakeupthread);
-               scheduler->wake(get_thread(*it));
-               waiters->erase(it);
+               if (waiters->size() != 0) {
+                       Thread * thread = fuzzer->selectNotify(waiters);
+                       scheduler->wake(thread);
+               }
                break;
        }
 
@@ -408,15 +449,10 @@ bool ModelExecution::process_mutex(ModelAction *curr)
  * @param curr The ModelAction to process
  * @return True if the mo_graph was updated or promises were resolved
  */
-bool ModelExecution::process_write(ModelAction *curr)
+void ModelExecution::process_write(ModelAction *curr)
 {
-
-       bool updated_mod_order = w_modification_order(curr);
-
-       mo_graph->commitChanges();
-
+       w_modification_order(curr);
        get_thread(curr)->set_return_value(VALUE_NONE);
-       return updated_mod_order;
 }
 
 /**
@@ -437,10 +473,10 @@ bool ModelExecution::process_fence(ModelAction *curr)
        bool updated = false;
        if (curr->is_acquire()) {
                action_list_t *list = &action_trace;
-               action_list_t::reverse_iterator rit;
+               sllnode<ModelAction *> * rit;
                /* Find X : is_read(X) && X --sb-> curr */
-               for (rit = list->rbegin(); rit != list->rend(); rit++) {
-                       ModelAction *act = *rit;
+               for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
+                       ModelAction *act = rit->getVal();
                        if (act == curr)
                                continue;
                        if (act->get_tid() != curr->get_tid())
@@ -458,11 +494,8 @@ bool ModelExecution::process_fence(ModelAction *curr)
                                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)
+                       ClockVector *cv = get_hb_from_write(act->get_reads_from());
+                       if (cv != NULL && curr->get_cv()->merge(cv))
                                updated = true;
                }
        }
@@ -480,10 +513,8 @@ bool ModelExecution::process_fence(ModelAction *curr)
  * @param curr The current action
  * @return True if synchronization was updated or a thread completed
  */
-bool ModelExecution::process_thread_action(ModelAction *curr)
+void ModelExecution::process_thread_action(ModelAction *curr)
 {
-       bool updated = false;
-
        switch (curr->get_type()) {
        case THREAD_CREATE: {
                thrd_t *thrd = (thrd_t *)curr->get_location();
@@ -495,7 +526,7 @@ bool ModelExecution::process_thread_action(ModelAction *curr)
                break;
        }
        case PTHREAD_CREATE: {
-               (*(pthread_t *)curr->get_location()) = pthread_counter++;       
+               (*(uint32_t *)curr->get_location()) = pthread_counter++;
 
                struct pthread_params *params = (struct pthread_params *)curr->get_value();
                Thread *th = new Thread(get_next_id(), NULL, params->func, params->arg, get_thread(curr));
@@ -503,8 +534,8 @@ bool ModelExecution::process_thread_action(ModelAction *curr)
                add_thread(th);
                th->set_creation(curr);
 
-               if ( pthread_map.size() < pthread_counter )
-                       pthread_map.resize( pthread_counter );
+               if ( pthread_map.size() < pthread_counter )
+                       pthread_map.resize( pthread_counter );
                pthread_map[ pthread_counter-1 ] = th;
 
                break;
@@ -513,44 +544,53 @@ bool ModelExecution::process_thread_action(ModelAction *curr)
                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 PTHREAD_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; // WL: to be add (modified)
+               break;  // WL: to be add (modified)
        }
 
+       case THREADONLY_FINISH:
        case THREAD_FINISH: {
                Thread *th = get_thread(curr);
+               if (curr->get_type() == THREAD_FINISH &&
+                               th == model->getInitThread()) {
+                       th->complete();
+                       setFinished();
+                       break;
+               }
+
                /* Wake up any joining threads */
-               for (unsigned int i = 0; i < get_num_threads(); i++) {
+               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();
-               updated = true; /* trigger rel-seq checks */
                break;
        }
        case THREAD_START: {
                break;
        }
+       case THREAD_SLEEP: {
+               Thread *th = get_thread(curr);
+               th->set_pending(curr);
+               scheduler->add_sleep(th);
+               break;
+       }
        default:
                break;
        }
-
-       return updated;
 }
 
 /**
  * Initialize the current action by performing one or more of the following
- * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
- * in the NodeStack, manipulating backtracking sets, allocating and
+ * actions, as appropriate: merging RMWR and RMWC/RMW actions,
+ * 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
@@ -560,45 +600,23 @@ bool ModelExecution::process_thread_action(ModelAction *curr)
  */
 bool ModelExecution::initialize_curr_action(ModelAction **curr)
 {
-       ModelAction *newcurr;
-
        if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
-               newcurr = process_rmw(*curr);
+               ModelAction *newcurr = process_rmw(*curr);
                delete *curr;
 
                *curr = newcurr;
                return false;
-       }
-
-       (*curr)->set_seq_number(get_next_seq_num());
-
-       newcurr = node_stack->explore_action(*curr);
-       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;
+               ModelAction *newcurr = *curr;
 
+               newcurr->set_seq_number(get_next_seq_num());
                /* 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()));
 
-               return true; /* This was a new ModelAction */
+               return true;    /* This was a new ModelAction */
        }
 }
 
@@ -614,22 +632,18 @@ bool ModelExecution::initialize_curr_action(ModelAction **curr)
  * @return True if this read established synchronization
  */
 
-bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
+void ModelExecution::read_from(ModelAction *act, 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;
+               ClockVector *cv = get_hb_from_write(rf);
+               if (cv == NULL)
+                       return;
+               act->get_cv()->merge(cv);
        }
-       return false;
 }
 
 /**
@@ -647,7 +661,7 @@ bool ModelExecution::read_from(ModelAction *act, const ModelAction *rf)
 bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
 {
        if (*second < *first) {
-               set_bad_synchronization();
+               ASSERT(0);      //This should not happend
                return false;
        }
        return second->synchronize_with(first);
@@ -675,6 +689,9 @@ bool ModelExecution::check_action_enabled(ModelAction *curr) {
                if (!blocking->is_complete()) {
                        return false;
                }
+       } else if (curr->is_sleep()) {
+               if (!fuzzer->shouldSleep(curr))
+                       return false;
        }
 
        return true;
@@ -701,80 +718,38 @@ ModelAction * ModelExecution::check_current_action(ModelAction *curr)
 
        wake_up_sleeping_actions(curr);
 
-       /* Add the action to lists before any other model-checking tasks */
-       if (!second_part_of_rmw)
-               add_action_to_lists(curr);
-
-       ModelVector<ModelAction *> * rf_set = NULL;
+       SnapVector<ModelAction *> * rf_set = NULL;
        /* Build may_read_from set for newly-created actions */
        if (newly_explored && curr->is_read())
-         rf_set = build_may_read_from(curr);
+               rf_set = build_may_read_from(curr);
+
+       bool canprune = false;
 
-       process_thread_action(curr);
-       
        if (curr->is_read() && !second_part_of_rmw) {
-         process_read(curr, rf_set);
-         delete rf_set;
-       }
-       
+               canprune = process_read(curr, rf_set);
+               delete rf_set;
+       } else
+               ASSERT(rf_set == NULL);
+
+       /* Add the action to lists */
+       if (!second_part_of_rmw)
+               add_action_to_lists(curr, canprune);
+
        if (curr->is_write())
-         process_write(curr);
-       
-       if (curr->is_fence())
-         process_fence(curr);
-       
-       if (curr->is_mutex_op())
-         process_mutex(curr);
+               add_write_to_lists(curr);
 
-       return curr;
-}
+       process_thread_action(curr);
 
-/**
- * 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 !is_infeasible();
-}
+       if (curr->is_write())
+               process_write(curr);
 
-/**
- * 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->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 (priv->bad_sc_read)
-               ptr += sprintf(ptr, "[bad sc read]");
-       if (ptr != buf)
-               model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
-}
+       if (curr->is_fence())
+               process_fence(curr);
 
-/**
- * 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->too_many_reads ||
-               priv->bad_synchronization ||
-         priv->bad_sc_read;
+       if (curr->is_mutex_op())
+               process_mutex(curr);
+
+       return curr;
 }
 
 /** Close out a RMWR by converting previous RMWR into a RMW or READ. */
@@ -782,8 +757,7 @@ ModelAction * ModelExecution::process_rmw(ModelAction *act) {
        ModelAction *lastread = get_last_action(act->get_tid());
        lastread->process_rmw(act);
        if (act->is_rmw()) {
-         mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
-               mo_graph->commitChanges();
+               mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
        }
        return lastread;
 }
@@ -802,39 +776,56 @@ ModelAction * ModelExecution::process_rmw(ModelAction *act) {
  *
  * @param curr The current action. Must be a read.
  * @param rf The ModelAction or Promise that curr reads from. Must be a write.
+ * @param check_only If true, then only check whether the current action satisfies
+ *        read modification order or not, without modifiying priorset and canprune.
+ *        False by default.
  * @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)
+
+bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf,
+                                                                                                                                                                       SnapVector<ModelAction *> * priorset, bool * canprune, bool check_only)
 {
        SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(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);
 
+       int tid = curr->get_tid();
+
+       /* Need to ensure thrd_lists is big enough because we have not added the curr actions yet.  */
+       if ((int)thrd_lists->size() <= tid) {
+               uint oldsize = thrd_lists->size();
+               thrd_lists->resize(priv->next_thread_id);
+               for(uint i = oldsize;i < priv->next_thread_id;i++)
+                       new (&(*thrd_lists)[i]) action_list_t();
+       }
+
+       ModelAction *prev_same_thread = NULL;
        /* Iterate over all threads */
-       for (i = 0; i < thrd_lists->size(); i++) {
-               /* Last SC fence in thread i */
+       for (unsigned int i = 0;i < thrd_lists->size();i++, tid = (((unsigned int)(tid+1)) == thrd_lists->size()) ? 0 : tid + 1) {
+               /* Last SC fence in thread tid */
                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);
+               if (i != 0)
+                       last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(tid), NULL);
 
-               /* Last SC fence in thread i, before last SC fence in current thread */
+               /* Last SC fence in thread tid, 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);
+                       last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(tid), last_sc_fence_local);
+
+               //Only need to iterate if either hb has changed for thread in question or SC fence after last operation...
+               if (prev_same_thread != NULL &&
+                               (prev_same_thread->get_cv()->getClock(tid) == curr->get_cv()->getClock(tid)) &&
+                               (last_sc_fence_thread_local == NULL || *last_sc_fence_thread_local < *prev_same_thread)) {
+                       continue;
+               }
 
                /* 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;
+               action_list_t *list = &(*thrd_lists)[tid];
+               sllnode<ModelAction *> * rit;
+               for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
+                       ModelAction *act = rit->getVal();
 
                        /* Skip curr */
                        if (act == curr)
@@ -851,19 +842,28 @@ bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
                                /* 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;
+                                       if (mo_graph->checkReachable(rf, act))
+                                               return false;
+                                       if (!check_only)
+                                               priorset->push_back(act);
                                        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;
+                                                                *act < *last_sc_fence_local) {
+                                       if (mo_graph->checkReachable(rf, act))
+                                               return false;
+                                       if (!check_only)
+                                               priorset->push_back(act);
                                        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;
+                                                                *act < *last_sc_fence_thread_before) {
+                                       if (mo_graph->checkReachable(rf, act))
+                                               return false;
+                                       if (!check_only)
+                                               priorset->push_back(act);
                                        break;
                                }
                        }
@@ -873,19 +873,37 @@ bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
                         * before" curr
                         */
                        if (act->happens_before(curr)) {
+                               if (i==0) {
+                                       if (last_sc_fence_local == NULL ||
+                                                       (*last_sc_fence_local < *act)) {
+                                               prev_same_thread = act;
+                                       }
+                               }
                                if (act->is_write()) {
-                                       added = mo_graph->addEdge(act, rf) || added;
+                                       if (mo_graph->checkReachable(rf, act))
+                                               return false;
+                                       if (!check_only)
+                                               priorset->push_back(act);
                                } else {
-                                       const ModelAction *prevrf = act->get_reads_from();
-                                       if (!prevrf->equals(rf))
-                                         added = mo_graph->addEdge(prevrf, rf) || added;
+                                       ModelAction *prevrf = act->get_reads_from();
+                                       if (!prevrf->equals(rf)) {
+                                               if (mo_graph->checkReachable(rf, prevrf))
+                                                       return false;
+                                               if (!check_only)
+                                                       priorset->push_back(prevrf);
+                                       } else {
+                                               if (act->get_tid() == curr->get_tid()) {
+                                                       //Can prune curr from obj list
+                                                       if (!check_only)
+                                                               *canprune = true;
+                                               }
+                                       }
                                }
                                break;
                        }
                }
        }
-
-       return added;
+       return true;
 }
 
 /**
@@ -912,27 +930,30 @@ bool ModelExecution::r_modification_order(ModelAction *curr, const rf_type *rf)
  * 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)
+void ModelExecution::w_modification_order(ModelAction *curr)
 {
        SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
        unsigned int i;
-       bool added = false;
        ASSERT(curr->is_write());
 
+       SnapList<ModelAction *> edgeset;
+
        if (curr->is_seqcst()) {
                /* We have to at least see the last sequentially consistent write,
-                        so we are initialized. */
+                        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;
+                       edgeset.push_back(last_seq_cst);
                }
+               //update map for next query
+               obj_last_sc_map.put(curr->get_location(), curr);
        }
 
        /* 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++) {
+       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())
@@ -940,9 +961,9 @@ bool ModelExecution::w_modification_order(ModelAction *curr)
 
                /* 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;
+               sllnode<ModelAction*>* rit;
+               for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
+                       ModelAction *act = rit->getVal();
                        if (act == curr) {
                                /*
                                 * 1) If RMW and it actually read from something, then we
@@ -967,7 +988,7 @@ bool ModelExecution::w_modification_order(ModelAction *curr)
                        /* 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;
+                               edgeset.push_back(act);
                                break;
                        }
 
@@ -983,32 +1004,17 @@ bool ModelExecution::w_modification_order(ModelAction *curr)
                                 *   readfrom(act) --mo--> act
                                 */
                                if (act->is_write())
-                                       added = mo_graph->addEdge(act, curr) || added;
+                                       edgeset.push_back(act);
                                else if (act->is_read()) {
                                        //if previous read accessed a null, just keep going
-                                 added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
+                                       edgeset.push_back(act->get_reads_from());
                                }
                                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.
-
-                                */
-
                        }
                }
        }
+       mo_graph->addEdges(&edgeset, curr);
 
-       return added;
 }
 
 /**
@@ -1024,14 +1030,14 @@ bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *
        SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(reader->get_location());
        unsigned int i;
        /* Iterate over all threads */
-       for (i = 0; i < thrd_lists->size(); i++) {
+       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;
+               sllnode<ModelAction *>* rit;
+               for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
+                       ModelAction *act = rit->getVal();
 
                        /* Don't disallow due to act == reader */
                        if (!reader->happens_before(act) || reader == act)
@@ -1049,95 +1055,57 @@ bool ModelExecution::mo_may_allow(const ModelAction *writer, const ModelAction *
 }
 
 /**
- * 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.
+ * Computes the clock vector that happens before propagates from this write.
  *
  * @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
- * @return true, if the ModelExecution is certain that release_heads is complete;
- * false otherwise
+ * @return ClockVector of happens before relation.
  */
-bool ModelExecution::release_seq_heads(const ModelAction *rf,
-               rel_heads_list_t *release_heads) 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()) {
+ClockVector * ModelExecution::get_hb_from_write(ModelAction *rf) const {
+       SnapVector<ModelAction *> * processset = NULL;
+       for ( ;rf != NULL;rf = rf->get_reads_from()) {
                ASSERT(rf->is_write());
+               if (!rf->is_rmw() || (rf->is_acquire() && rf->is_release()) || rf->get_rfcv() != NULL)
+                       break;
+               if (processset == NULL)
+                       processset = new SnapVector<ModelAction *>();
+               processset->push_back(rf);
+       }
 
-               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 */
-       };
-       ASSERT(rf); // Needs to be real write
-
-       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);
-
-       return true; /* complete */
-}
-
-/**
- * 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();
-
-       release_seq_heads(rf, release_heads);
+       int i = (processset == NULL) ? 0 : processset->size();
+
+       ClockVector * vec = NULL;
+       while(true) {
+               if (rf->get_rfcv() != NULL) {
+                       vec = rf->get_rfcv();
+               } else if (rf->is_acquire() && rf->is_release()) {
+                       vec = rf->get_cv();
+               } else if (rf->is_release() && !rf->is_rmw()) {
+                       vec = rf->get_cv();
+               } else if (rf->is_release()) {
+                       //have rmw that is release and doesn't have a rfcv
+                       (vec = new ClockVector(vec, NULL))->merge(rf->get_cv());
+                       rf->set_rfcv(vec);
+               } else {
+                       //operation that isn't release
+                       if (rf->get_last_fence_release()) {
+                               if (vec == NULL)
+                                       vec = rf->get_last_fence_release()->get_cv();
+                               else
+                                       (vec=new ClockVector(vec, NULL))->merge(rf->get_last_fence_release()->get_cv());
+                       }
+                       rf->set_rfcv(vec);
+               }
+               i--;
+               if (i >= 0) {
+                       rf = (*processset)[i];
+               } else
+                       break;
+       }
+       if (processset != NULL)
+               delete processset;
+       return vec;
 }
 
 /**
@@ -1147,36 +1115,35 @@ void ModelExecution::get_release_seq_heads(ModelAction *acquire,
  *
  * @param act is the ModelAction to add.
  */
-void ModelExecution::add_action_to_lists(ModelAction *act)
+void ModelExecution::add_action_to_lists(ModelAction *act, bool canprune)
 {
        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);
+       if ((act->is_fence() && act->is_seqcst()) || act->is_unlock()) {
+               action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
+               act->setActionRef(list->add_back(act));
        }
-       list->push_back(act);
 
-       action_trace.push_back(act);
-       if (uninit)
-               action_trace.push_front(uninit);
+       // Update action trace, a total order of all actions
+       act->setTraceRef(action_trace.add_back(act));
+
 
+       // Update obj_thrd_map, a per location, per thread, order of actions
        SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
-       if (tid >= (int)vec->size())
+       if ((int)vec->size() <= tid) {
+               uint oldsize = vec->size();
                vec->resize(priv->next_thread_id);
-       (*vec)[tid].push_back(act);
-       if (uninit)
-               (*vec)[uninit_id].push_front(uninit);
+               for(uint i = oldsize;i < priv->next_thread_id;i++)
+                       new (&(*vec)[i]) action_list_t();
+       }
+       if (!canprune)
+               act->setThrdMapRef((*vec)[tid].add_back(act));
 
+       // Update thrd_last_action, the last action taken by each thread
        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;
 
+       // Update thrd_last_fence_release, the last release fence taken by each thread
        if (act->is_fence() && act->is_release()) {
                if ((int)thrd_last_fence_release.size() <= tid)
                        thrd_last_fence_release.resize(get_num_threads());
@@ -1185,13 +1152,94 @@ void ModelExecution::add_action_to_lists(ModelAction *act)
 
        if (act->is_wait()) {
                void *mutex_loc = (void *) act->get_value();
-               get_safe_ptr_action(&obj_map, mutex_loc)->push_back(act);
+               act->setActionRef(get_safe_ptr_action(&obj_map, mutex_loc)->add_back(act));
 
                SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
-               if (tid >= (int)vec->size())
+               if ((int)vec->size() <= tid) {
+                       uint oldsize = vec->size();
                        vec->resize(priv->next_thread_id);
-               (*vec)[tid].push_back(act);
+                       for(uint i = oldsize;i < priv->next_thread_id;i++)
+                               new (&(*vec)[i]) action_list_t();
+               }
+               act->setThrdMapRef((*vec)[tid].add_back(act));
+       }
+}
+
+sllnode<ModelAction *>* insertIntoActionList(action_list_t *list, ModelAction *act) {
+       sllnode<ModelAction*> * rit = list->end();
+       modelclock_t next_seq = act->get_seq_number();
+       if (rit == NULL || (rit->getVal()->get_seq_number() == next_seq))
+               return list->add_back(act);
+       else {
+               for(;rit != NULL;rit=rit->getPrev()) {
+                       if (rit->getVal()->get_seq_number() == next_seq) {
+                               return list->insertAfter(rit, act);
+                       }
+               }
+               return NULL;
+       }
+}
+
+sllnode<ModelAction *>* insertIntoActionListAndSetCV(action_list_t *list, ModelAction *act) {
+       sllnode<ModelAction*> * rit = list->end();
+       modelclock_t next_seq = act->get_seq_number();
+       if (rit == NULL) {
+               act->create_cv(NULL);
+               return NULL;
+       } else if (rit->getVal()->get_seq_number() == next_seq) {
+               act->create_cv(rit->getVal());
+               return list->add_back(act);
+       } else {
+               for(;rit != NULL;rit=rit->getPrev()) {
+                       if (rit->getVal()->get_seq_number() == next_seq) {
+                               act->create_cv(rit->getVal());
+                               return list->insertAfter(rit, act);
+                       }
+               }
+               return NULL;
+       }
+}
+
+/**
+ * Performs various bookkeeping operations for a normal write.  The
+ * complication is that we are typically inserting a normal write
+ * lazily, so we need to insert it into the middle of lists.
+ *
+ * @param act is the ModelAction to add.
+ */
+
+void ModelExecution::add_normal_write_to_lists(ModelAction *act)
+{
+       int tid = id_to_int(act->get_tid());
+       act->setTraceRef(insertIntoActionListAndSetCV(&action_trace, act));
+
+       // Update obj_thrd_map, a per location, per thread, order of actions
+       SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
+       if (tid >= (int)vec->size()) {
+               uint oldsize =vec->size();
+               vec->resize(priv->next_thread_id);
+               for(uint i=oldsize;i<priv->next_thread_id;i++)
+                       new (&(*vec)[i]) action_list_t();
        }
+       act->setThrdMapRef(insertIntoActionList(&(*vec)[tid],act));
+
+       ModelAction * lastact = thrd_last_action[tid];
+       // Update thrd_last_action, the last action taken by each thrad
+       if (lastact == NULL || lastact->get_seq_number() == act->get_seq_number())
+               thrd_last_action[tid] = act;
+}
+
+
+void ModelExecution::add_write_to_lists(ModelAction *write) {
+       SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, write->get_location());
+       int tid = id_to_int(write->get_tid());
+       if (tid >= (int)vec->size()) {
+               uint oldsize =vec->size();
+               vec->resize(priv->next_thread_id);
+               for(uint i=oldsize;i<priv->next_thread_id;i++)
+                       new (&(*vec)[i]) action_list_t();
+       }
+       write->setActionRef((*vec)[tid].add_back(write));
 }
 
 /**
@@ -1233,16 +1281,7 @@ ModelAction * ModelExecution::get_last_fence_release(thread_id_t tid) const
 ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
 {
        void *location = curr->get_location();
-       action_list_t *list = obj_map.get(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;
+       return obj_last_sc_map.get(location);
 }
 
 /**
@@ -1261,20 +1300,22 @@ ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const Mode
        if (!list)
                return NULL;
 
-       action_list_t::reverse_iterator rit = list->rbegin();
+       sllnode<ModelAction*>* rit = list->end();
 
        if (before_fence) {
-               for (; rit != list->rend(); rit++)
-                       if (*rit == before_fence)
+               for (;rit != NULL;rit=rit->getPrev())
+                       if (rit->getVal() == before_fence)
                                break;
 
-               ASSERT(*rit == before_fence);
-               rit++;
+               ASSERT(rit->getVal() == before_fence);
+               rit=rit->getPrev();
        }
 
-       for (; rit != list->rend(); rit++)
-               if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
-                       return *rit;
+       for (;rit != NULL;rit=rit->getPrev()) {
+               ModelAction *act = rit->getVal();
+               if (act->is_fence() && (tid == act->get_tid()) && act->is_seqcst())
+                       return act;
+       }
        return NULL;
 }
 
@@ -1291,11 +1332,14 @@ ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
        void *location = curr->get_location();
 
        action_list_t *list = obj_map.get(location);
+       if (list == NULL)
+               return NULL;
+
        /* 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;
+       sllnode<ModelAction*>* rit;
+       for (rit = list->end();rit != NULL;rit=rit->getPrev())
+               if (rit->getVal()->is_unlock() || rit->getVal()->is_wait())
+                       return rit->getVal();
        return NULL;
 }
 
@@ -1314,7 +1358,24 @@ ModelAction * ModelExecution::get_parent_action(thread_id_t tid) const
  */
 ClockVector * ModelExecution::get_cv(thread_id_t tid) const
 {
-       return get_parent_action(tid)->get_cv();
+       ModelAction *firstaction=get_parent_action(tid);
+       return firstaction != NULL ? firstaction->get_cv() : NULL;
+}
+
+bool valequals(uint64_t val1, uint64_t val2, int size) {
+       switch(size) {
+       case 1:
+               return ((uint8_t)val1) == ((uint8_t)val2);
+       case 2:
+               return ((uint16_t)val1) == ((uint16_t)val2);
+       case 4:
+               return ((uint32_t)val1) == ((uint32_t)val2);
+       case 8:
+               return val1==val2;
+       default:
+               ASSERT(0);
+               return false;
+       }
 }
 
 /**
@@ -1324,9 +1385,9 @@ ClockVector * ModelExecution::get_cv(thread_id_t tid) const
  * @param curr is the current ModelAction that we are exploring; it must be a
  * 'read' operation.
  */
-ModelVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *curr)
+SnapVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *curr)
 {
-       SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
+       SnapVector<action_list_t> *thrd_lists = obj_wr_thrd_map.get(curr->get_location());
        unsigned int i;
        ASSERT(curr->is_read());
 
@@ -1335,40 +1396,50 @@ ModelVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *c
        if (curr->is_seqcst())
                last_sc_write = get_last_seq_cst_write(curr);
 
-       ModelVector<ModelAction *> * rf_set = new ModelVector<ModelAction *>();
-       
-       /* 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;
+       SnapVector<ModelAction *> * rf_set = new SnapVector<ModelAction *>();
 
-                       /* Only consider 'write' actions */
-                       if (!act->is_write() || act == curr)
-                               continue;
+       /* Iterate over all threads */
+       if (thrd_lists != NULL)
+               for (i = 0;i < thrd_lists->size();i++) {
+                       /* Iterate over actions in thread, starting from most recent */
+                       action_list_t *list = &(*thrd_lists)[i];
+                       sllnode<ModelAction *> * rit;
+                       for (rit = list->end();rit != NULL;rit=rit->getPrev()) {
+                               ModelAction *act = rit->getVal();
+
+                               if (act == curr)
+                                       continue;
 
-                       /* Don't consider more than one seq_cst write if we are a seq_cst read. */
-                       bool allow_read = true;
+                               /* 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;
+
+                               /* Need to check whether we will have two RMW reading from the same value */
+                               if (curr->is_rmwr()) {
+                                       /* It is okay if we have a failing CAS */
+                                       if (!curr->is_rmwrcas() ||
+                                                       valequals(curr->get_value(), act->get_value(), curr->getSize())) {
+                                               //Need to make sure we aren't the second RMW
+                                               CycleNode * node = mo_graph->getNode_noCreate(act);
+                                               if (node != NULL && node->getRMW() != NULL) {
+                                                       //we are the second RMW
+                                                       allow_read = false;
+                                               }
+                                       }
+                               }
 
-                       if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
-                               allow_read = false;
+                               if (allow_read) {
+                                       /* Only add feasible reads */
+                                       rf_set->push_back(act);
+                               }
 
-                       if (allow_read) {
-                               /* Only add feasible reads */
-                               mo_graph->startChanges();
-                               r_modification_order(curr, act);
-                               if (!is_infeasible())
-                                 rf_set->push_back(act);
-                               mo_graph->rollbackChanges();
+                               /* Include at most one act per-thread that "happens before" curr */
+                               if (act->happens_before(curr))
+                                       break;
                        }
-
-                       /* Include at most one act per-thread that "happens before" curr */
-                       if (act->happens_before(curr))
-                               break;
                }
-       }
 
        if (DBG_ENABLED()) {
                model_print("Reached read action:\n");
@@ -1378,29 +1449,9 @@ ModelVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *c
        return rf_set;
 }
 
-/**
- * @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(const action_list_t *list)
+static void print_list(action_list_t *list)
 {
-       action_list_t::const_iterator it;
+       sllnode<ModelAction*> *it;
 
        model_print("------------------------------------------------------------------------------------\n");
        model_print("#    t    Action type     MO       Location         Value               Rf  CV\n");
@@ -1408,18 +1459,18 @@ static void print_list(const action_list_t *list)
 
        unsigned int hash = 0;
 
-       for (it = list->begin(); it != list->end(); it++) {
-               const ModelAction *act = *it;
+       for (it = list->begin();it != NULL;it=it->getNext()) {
+               const ModelAction *act = it->getVal();
                if (act->get_seq_number() > 0)
                        act->print();
-               hash = hash^(hash<<3)^((*it)->hash());
+               hash = hash^(hash<<3)^(it->getVal()->hash());
        }
        model_print("HASH %u\n", hash);
        model_print("------------------------------------------------------------------------------------\n");
 }
 
 #if SUPPORT_MOD_ORDER_DUMP
-void ModelExecution::dumpGraph(char *filename) const
+void ModelExecution::dumpGraph(char *filename)
 {
        char buffer[200];
        sprintf(buffer, "%s.dot", filename);
@@ -1428,20 +1479,20 @@ void ModelExecution::dumpGraph(char *filename) const
        mo_graph->dumpNodes(file);
        ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
 
-       for (action_list_t::const_iterator it = action_trace.begin(); it != action_trace.end(); it++) {
-               ModelAction *act = *it;
+       for (sllnode<ModelAction*>* it = action_trace.begin();it != NULL;it=it->getNext()) {
+               ModelAction *act = it->getVal();
                if (act->is_read()) {
                        mo_graph->dot_print_node(file, act);
                        mo_graph->dot_print_edge(file,
-                                               act->get_reads_from(),
-                                               act,
-                                               "label=\"rf\", color=red, weight=2");
+                                                                                                                        act->get_reads_from(),
+                                                                                                                        act,
+                                                                                                                        "label=\"rf\", color=red, weight=2");
                }
                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[id_to_int(act->get_tid())],
+                                                                                                                        act,
+                                                                                                                        "label=\"sb\", color=blue, weight=400");
                }
 
                thread_array[act->get_tid()] = act;
@@ -1453,7 +1504,7 @@ void ModelExecution::dumpGraph(char *filename) const
 #endif
 
 /** @brief Prints an execution trace summary. */
-void ModelExecution::print_summary() const
+void ModelExecution::print_summary()
 {
 #if SUPPORT_MOD_ORDER_DUMP
        char buffername[100];
@@ -1464,13 +1515,11 @@ void ModelExecution::print_summary() const
 #endif
 
        model_print("Execution trace %d:", get_execution_number());
-       if (isfeasibleprefix()) {
-               if (scheduler->all_threads_sleeping())
-                       model_print(" SLEEP-SET REDUNDANT");
-               if (have_bug_reports())
-                       model_print(" DETECTED BUG(S)");
-       } else
-               print_infeasibility(" INFEASIBLE");
+       if (scheduler->all_threads_sleeping())
+               model_print(" SLEEP-SET REDUNDANT");
+       if (have_bug_reports())
+               model_print(" DETECTED BUG(S)");
+
        model_print("\n");
 
        print_list(&action_trace);
@@ -1522,8 +1571,14 @@ Thread * ModelExecution::get_thread(const ModelAction *act) const
  * @return A Thread reference
  */
 Thread * ModelExecution::get_pthread(pthread_t pid) {
-        if (pid < pthread_counter + 1) return pthread_map[pid];
-        else return NULL;
+       union {
+               pthread_t p;
+               uint32_t v;
+       } x;
+       x.p = pid;
+       uint32_t thread_id = x.v;
+       if (thread_id < pthread_counter + 1) return pthread_map[thread_id];
+       else return NULL;
 }
 
 /**
@@ -1560,30 +1615,27 @@ bool ModelExecution::is_enabled(thread_id_t tid) const
 Thread * ModelExecution::action_select_next_thread(const ModelAction *curr) const
 {
        /* Do not split atomic RMW */
-       if (curr->is_rmwr())
+       if (curr->is_rmwr() && !paused_by_fuzzer(curr))
                return get_thread(curr);
-       if (curr->is_write()) {
-               std::memory_order order = curr->get_mo(); 
-               switch(order) {
-                       case std::memory_order_relaxed: 
-                               return get_thread(curr);
-                       case std::memory_order_release:
-                               return get_thread(curr);
-                       default:
-                               return NULL;
-               }       
-       }
-
        /* Follow CREATE with the created thread */
        /* which is not needed, because model.cc takes care of this */
        if (curr->get_type() == THREAD_CREATE)
-               return curr->get_thread_operand(); 
+               return curr->get_thread_operand();
        if (curr->get_type() == PTHREAD_CREATE) {
                return curr->get_thread_operand();
        }
        return NULL;
 }
 
+/** @param act A read atomic action */
+bool ModelExecution::paused_by_fuzzer(const ModelAction * act) const
+{
+       ASSERT(act->is_read());
+
+       // Actions paused by fuzzer have their sequence number reset to 0
+       return act->get_seq_number() == 0;
+}
+
 /**
  * Takes the next step in the execution, if possible.
  * @param curr The current step to take
@@ -1595,13 +1647,214 @@ 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? */
+       ASSERT(check_action_enabled(curr));     /* May have side effects? */
        curr = check_current_action(curr);
        ASSERT(curr);
 
+       /* Process this action in ModelHistory for records */
+       model->get_history()->process_action( curr, curr->get_tid() );
+
        if (curr_thrd->is_blocked() || curr_thrd->is_complete())
                scheduler->remove_thread(curr_thrd);
 
        return action_select_next_thread(curr);
 }
 
+void ModelExecution::removeAction(ModelAction *act) {
+       {
+               sllnode<ModelAction *> * listref = act->getTraceRef();
+               if (listref != NULL) {
+                       action_trace.erase(listref);
+               }
+       }
+       {
+               sllnode<ModelAction *> * listref = act->getThrdMapRef();
+               if (listref != NULL) {
+                       SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
+                       (*vec)[act->get_tid()].erase(listref);
+               }
+       }
+       if ((act->is_fence() && act->is_seqcst()) || act->is_unlock()) {
+               sllnode<ModelAction *> * listref = act->getActionRef();
+               if (listref != NULL) {
+                       action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
+                       list->erase(listref);
+               }
+       } else if (act->is_wait()) {
+               sllnode<ModelAction *> * listref = act->getActionRef();
+               if (listref != NULL) {
+                       void *mutex_loc = (void *) act->get_value();
+                       get_safe_ptr_action(&obj_map, mutex_loc)->erase(listref);
+               }
+       } else if (act->is_free()) {
+               sllnode<ModelAction *> * listref = act->getActionRef();
+               if (listref != NULL) {
+                       SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, act->get_location());
+                       (*vec)[act->get_tid()].erase(listref);
+               }
+               //Remove from Cyclegraph
+               mo_graph->freeAction(act);
+       }
+}
+
+ClockVector * ModelExecution::computeMinimalCV() {
+       ClockVector *cvmin = NULL;
+       //Thread 0 isn't a real thread, so skip it..
+       for(unsigned int i = 1;i < thread_map.size();i++) {
+               Thread * t = thread_map[i];
+               if (t->get_state() == THREAD_COMPLETED)
+                       continue;
+               thread_id_t tid = int_to_id(i);
+               ClockVector * cv = get_cv(tid);
+               if (cvmin == NULL)
+                       cvmin = new ClockVector(cv, NULL);
+               else
+                       cvmin->minmerge(cv);
+       }
+       return cvmin;
+}
+
+//Options...
+//How often to check for memory
+//How much of the trace to always keep
+//Whether to sacrifice completeness...i.e., remove visible writes
+
+void ModelExecution::collectActions() {
+       //Compute minimal clock vector for all live threads
+       ClockVector *cvmin = computeMinimalCV();
+       cvmin->print();
+       SnapVector<CycleNode *> * queue = new SnapVector<CycleNode *>();
+       modelclock_t maxtofree = priv->used_sequence_numbers - params->traceminsize;
+
+       //Next walk action trace...  When we hit an action, see if it is
+       //invisible (e.g., earlier than the first before the minimum
+       //clock for the thread...  if so erase it and all previous
+       //actions in cyclegraph
+       sllnode<ModelAction*> * it;
+       for (it = action_trace.begin();it != NULL;it=it->getNext()) {
+               ModelAction *act = it->getVal();
+               modelclock_t actseq = act->get_seq_number();
+
+               //See if we are done
+               if (actseq > maxtofree)
+                       break;
+
+               thread_id_t act_tid = act->get_tid();
+               modelclock_t tid_clock = cvmin->getClock(act_tid);
+               if (actseq <= tid_clock || params->removevisible) {
+                       ModelAction * write;
+                       if (act->is_write()) {
+                               write = act;
+                       } else if (act->is_read()) {
+                               write = act->get_reads_from();
+                       } else
+                               continue;
+
+                       //Mark everything earlier in MO graph to be freed
+                       CycleNode * cn = mo_graph->getNode_noCreate(write);
+                       if (cn != NULL) {
+                               queue->push_back(cn);
+                               while(!queue->empty()) {
+                                       CycleNode * node = queue->back();
+                                       queue->pop_back();
+                                       for(unsigned int i=0;i<node->getNumInEdges();i++) {
+                                               CycleNode * prevnode = node->getInEdge(i);
+                                               ModelAction * prevact = prevnode->getAction();
+                                               if (prevact->get_type() != READY_FREE) {
+                                                       prevact->set_free();
+                                                       queue->push_back(prevnode);
+                                               }
+                                       }
+                               }
+                       }
+               }
+       }
+       for (;it != NULL;) {
+               ModelAction *act = it->getVal();
+               //Do iteration early since we may delete node...
+               it=it->getPrev();
+               bool islastact = false;
+               ModelAction *lastact = get_last_action(act->get_tid());
+               if (act == lastact) {
+                       Thread * th = get_thread(act);
+                       islastact = !th->is_complete();
+               }
+
+               if (act->is_read()) {
+                       if (islastact) {
+                               act->set_read_from(NULL);
+                       }
+                       if (act->get_reads_from()->is_free()) {
+                               removeAction(act);
+                               delete act;
+                       } else {
+                               const ModelAction *rel_fence =act->get_last_fence_release();
+                               if (rel_fence != NULL) {
+                                       modelclock_t relfenceseq = rel_fence->get_seq_number();
+                                       thread_id_t relfence_tid = rel_fence->get_tid();
+                                       modelclock_t tid_clock = cvmin->getClock(relfence_tid);
+                                       //Remove references to irrelevant release fences
+                                       if (relfenceseq <= tid_clock)
+                                               act->set_last_fence_release(NULL);
+                               }
+                       }
+               }
+
+               if (islastact) {
+                       continue;
+               } else if (act->is_free()) {
+                       removeAction(act);
+                       delete act;
+               } else if (act->is_write()) {
+                       //Do nothing with write that hasn't been marked to be freed
+               } else if (act->is_fence()) {
+                       //Note that acquire fences can always be safely
+                       //removed, but could incur extra overheads in
+                       //traversals.  Removing them before the cvmin seems
+                       //like a good compromise.
+
+                       //Release fences before the cvmin don't do anything
+                       //because everyone has already synchronized.
+
+                       //Sequentially fences before cvmin are redundant
+                       //because happens-before will enforce same
+                       //orderings.
+
+                       modelclock_t actseq = act->get_seq_number();
+                       thread_id_t act_tid = act->get_tid();
+                       modelclock_t tid_clock = cvmin->getClock(act_tid);
+                       if (actseq <= tid_clock) {
+                               removeAction(act);
+                               delete act;
+                       }
+               } else {
+                       //need to deal with lock, annotation, wait, notify, thread create, start, join, yield, finish
+                       //lock, notify thread create, thread finish, yield, finish are dead as soon as they are in the trace
+                       //need to keep most recent unlock/wait for each lock
+                       if(act->is_unlock() || act->is_wait()) {
+                               ModelAction * lastlock = get_last_unlock(act);
+                               if (lastlock != act) {
+                                       removeAction(act);
+                                       delete act;
+                               }
+                       } else if (act->is_create()) {
+                               if (act->get_thread_operand()->is_complete()) {
+                                       removeAction(act);
+                                       delete act;
+                               }
+                       } else {
+                               removeAction(act);
+                               delete act;
+                       }
+               }
+       }
+
+       delete cvmin;
+       delete queue;
+}
+
+
+
+Fuzzer * ModelExecution::getFuzzer() {
+       return fuzzer;
+}