Change initialize a bit
[c11tester.git] / execution.cc
index 1691c6434e6025ece00a736a116a4dbf007c5242..8f459d172bd9a1cd8caebd3e5908be856bd889ec 100644 (file)
 #include "bugmessage.h"
 #include "history.h"
 #include "fuzzer.h"
+#include "newfuzzer.h"
 
 #define INITIAL_THREAD_ID       0
 
+#ifdef COLLECT_STAT
+static unsigned int atomic_load_count = 0;
+static unsigned int atomic_store_count = 0;
+static unsigned int atomic_rmw_count = 0;
+
+static unsigned int atomic_fence_count = 0;
+static unsigned int atomic_lock_count = 0;
+static unsigned int atomic_trylock_count = 0;
+static unsigned int atomic_unlock_count = 0;
+static unsigned int atomic_notify_count = 0;
+static unsigned int atomic_wait_count = 0;
+static unsigned int atomic_timedwait_count = 0;
+#endif
+
 /**
  * Structure for holding small ModelChecker members that should be snapshotted
  */
@@ -27,7 +42,6 @@ struct model_snapshot_members {
                next_thread_id(INITIAL_THREAD_ID),
                used_sequence_numbers(0),
                bugs(),
-               bad_synchronization(false),
                asserted(false)
        { }
 
@@ -41,7 +55,6 @@ struct model_snapshot_members {
        modelclock_t used_sequence_numbers;
        SnapVector<bug_message *> bugs;
        /** @brief Incorrectly-ordered synchronization was made */
-       bool bad_synchronization;
        bool asserted;
 
        SNAPSHOTALLOC
@@ -52,27 +65,36 @@ 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 */
        pthread_map(0),
-       pthread_counter(1),
+       pthread_counter(2),
+       action_trace(),
        obj_map(),
        condvar_waiters_map(),
        obj_thrd_map(),
+       obj_wr_thrd_map(),
+       obj_last_sc_map(),
        mutex_map(),
+       cond_map(),
        thrd_last_action(1),
        thrd_last_fence_release(),
        priv(new struct model_snapshot_members ()),
        mo_graph(new CycleGraph()),
+#ifdef NEWFUZZER
+       fuzzer(new NewFuzzer()),
+#else
        fuzzer(new Fuzzer()),
-       thrd_func_list(),
-       thrd_func_inst_lists(),
+#endif
        isfinished(false)
 {
        /* Initialize a model-checker thread, for special ModelActions */
        model_thread = new Thread(get_next_id());
        add_thread(model_thread);
+       fuzzer->register_engine(m, this);
        scheduler->register_engine(this);
+#ifdef TLS
+       pthread_key_create(&pthreadkey, tlsdestructor);
+#endif
 }
 
 /** @brief Destructor */
@@ -90,26 +112,104 @@ 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 SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<action_list_t> *, uintptr_t, 2> * hash, void * ptr)
 {
-       action_list_t *tmp = hash->get(ptr);
+       SnapVector<action_list_t> *tmp = hash->get(ptr);
        if (tmp == NULL) {
-               tmp = new action_list_t();
+               tmp = new SnapVector<action_list_t>();
                hash->put(ptr, tmp);
        }
        return tmp;
 }
 
-static SnapVector<action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
+static simple_action_list_t * get_safe_ptr_action(HashTable<const void *, simple_action_list_t *, uintptr_t, 2> * hash, void * ptr)
 {
-       SnapVector<action_list_t> *tmp = hash->get(ptr);
+       simple_action_list_t *tmp = hash->get(ptr);
        if (tmp == NULL) {
-               tmp = new SnapVector<action_list_t>();
+               tmp = new simple_action_list_t();
                hash->put(ptr, tmp);
        }
        return tmp;
 }
 
+static SnapVector<simple_action_list_t> * get_safe_ptr_vect_action(HashTable<const void *, SnapVector<simple_action_list_t> *, uintptr_t, 2> * hash, void * ptr)
+{
+       SnapVector<simple_action_list_t> *tmp = hash->get(ptr);
+       if (tmp == NULL) {
+               tmp = new SnapVector<simple_action_list_t>();
+               hash->put(ptr, tmp);
+       }
+       return tmp;
+}
+
+/**
+ * When vectors of action lists are reallocated due to resize, the root address of
+ * action lists may change. Hence we need to fix the parent pointer of the children
+ * of root.
+ */
+static void fixup_action_list(SnapVector<action_list_t> * vec)
+{
+       for (uint i = 0;i < vec->size();i++) {
+               action_list_t * list = &(*vec)[i];
+               if (list != NULL)
+                       list->fixupParent();
+       }
+}
+
+#ifdef COLLECT_STAT
+static inline void record_atomic_stats(ModelAction * act)
+{
+       switch (act->get_type()) {
+       case ATOMIC_WRITE:
+               atomic_store_count++;
+               break;
+       case ATOMIC_RMW:
+               atomic_load_count++;
+               break;
+       case ATOMIC_READ:
+               atomic_rmw_count++;
+               break;
+       case ATOMIC_FENCE:
+               atomic_fence_count++;
+               break;
+       case ATOMIC_LOCK:
+               atomic_lock_count++;
+               break;
+       case ATOMIC_TRYLOCK:
+               atomic_trylock_count++;
+               break;
+       case ATOMIC_UNLOCK:
+               atomic_unlock_count++;
+               break;
+       case ATOMIC_NOTIFY_ONE:
+       case ATOMIC_NOTIFY_ALL:
+               atomic_notify_count++;
+               break;
+       case ATOMIC_WAIT:
+               atomic_wait_count++;
+               break;
+       case ATOMIC_TIMEDWAIT:
+               atomic_timedwait_count++;
+       default:
+               return;
+       }
+}
+
+void print_atomic_accesses()
+{
+       model_print("atomic store  count: %u\n", atomic_store_count);
+       model_print("atomic load   count: %u\n", atomic_load_count);
+       model_print("atomic rmw    count: %u\n", atomic_rmw_count);
+
+       model_print("atomic fence  count: %u\n", atomic_fence_count);
+       model_print("atomic lock   count: %u\n", atomic_lock_count);
+       model_print("atomic trylock count: %u\n", atomic_trylock_count);
+       model_print("atomic unlock count: %u\n", atomic_unlock_count);
+       model_print("atomic notify count: %u\n", atomic_notify_count);
+       model_print("atomic wait   count: %u\n", atomic_wait_count);
+       model_print("atomic timedwait count: %u\n", atomic_timedwait_count);
+}
+#endif
 /** @return a thread ID for a new Thread */
 thread_id_t ModelExecution::get_next_id()
 {
@@ -128,6 +228,18 @@ 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?
  *
@@ -138,52 +250,36 @@ modelclock_t ModelExecution::get_next_seq_num()
 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)
+
+       /* 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++) {
-               Thread *thr = get_thread(int_to_id(i));
-               if (scheduler->is_sleep_set(thr)) {
-                       if (should_wake_up(curr, thr))
+               thread_id_t tid = int_to_id(i);
+               if (scheduler->is_sleep_set(tid)) {
+                       Thread *thr = get_thread(tid);
+                       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;
-}
-
-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 */
@@ -192,16 +288,6 @@ bool ModelExecution::have_bug_reports() const
        return priv->bugs.size() != 0;
 }
 
-/** @return True, if any fatal bugs have been reported for this execution.
- *  Any bug other than a data race is considered a fatal bug. Data races
- *  are not considered fatal unless the number of races is exceeds
- *  a threshold (temporarily set as 15).
- */
-bool ModelExecution::have_fatal_bug_reports() const
-{
-       return priv->bugs.size() != 0;
-}
-
 SnapVector<bug_message *> * ModelExecution::get_bugs() const
 {
        return &priv->bugs;
@@ -275,6 +361,9 @@ ModelAction * ModelExecution::convertNonAtomicStore(void * location) {
        add_normal_write_to_lists(act);
        add_write_to_lists(act);
        w_modification_order(act);
+#ifdef NEWFUZZER
+       model->get_history()->process_action(act, act->get_tid());
+#endif
        return act;
 }
 
@@ -282,21 +371,33 @@ ModelAction * ModelExecution::convertNonAtomicStore(void * location) {
  * 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.
  */
-void ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> * rf_set)
+bool ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> * rf_set)
 {
-       SnapVector<const ModelAction *> * priorset = new SnapVector<const ModelAction *>();
+       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];
 
+               ModelAction *rf = (*rf_set)[index];
 
                ASSERT(rf);
                bool canprune = false;
@@ -305,13 +406,13 @@ void ModelExecution::process_read(ModelAction *curr, SnapVector<ModelAction *> *
                                mo_graph->addEdge((*priorset)[i], rf);
                        }
                        read_from(curr, rf);
-                       get_thread(curr)->set_return_value(curr->get_return_value());
+                       get_thread(curr)->set_return_value(rf->get_write_value());
                        delete priorset;
-                       if (canprune && curr->get_type() == ATOMIC_READ) {
-                               int tid = id_to_int(curr->get_tid());
-                               (*obj_thrd_map.get(curr->get_location()))[tid].pop_back();
-                       }
-                       return;
+                       //Update acquire fence clock vector
+                       ClockVector * hbcv = get_hb_from_write(rf);
+                       if (hbcv != NULL)
+                               get_thread(curr)->get_acq_fence_cv()->merge(hbcv);
+                       return canprune && (curr->get_type() == ATOMIC_READ);
                }
                priorset->clear();
                (*rf_set)[index] = rf_set->back();
@@ -358,6 +459,8 @@ bool ModelExecution::process_mutex(ModelAction *curr)
                //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");
+
+               // TODO: lock count for recursive mutexes
                state->locked = get_thread(curr);
                ModelAction *unlock = get_last_unlock(curr);
                //synchronize with the previous unlock statement
@@ -367,37 +470,71 @@ bool ModelExecution::process_mutex(ModelAction *curr)
                }
                break;
        }
-       case ATOMIC_WAIT:
-       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...
+       case ATOMIC_WAIT: {
+               //TODO: DOESN'T REALLY IMPLEMENT SPURIOUS WAKEUPS CORRECTLY
+               if (fuzzer->shouldWait(curr)) {
+                       Thread *curr_thrd = get_thread(curr);
+                       /* wake up the other threads */
+                       for (unsigned int i = 0;i < get_num_threads();i++) {
+                               Thread *t = get_thread(int_to_id(i));
+                               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;
+
+                       /* remove old wait action and disable this thread */
+                       simple_action_list_t * waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
+                       for (sllnode<ModelAction *> * it = waiters->begin();it != NULL;it = it->getNext()) {
+                               ModelAction * wait = it->getVal();
+                               if (wait->get_tid() == curr->get_tid()) {
+                                       waiters->erase(it);
+                                       break;
+                               }
+                       }
+
+                       waiters->push_back(curr);
+                       scheduler->sleep(curr_thrd);
+               }
 
+               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...
+
+               // TODO: lock count for recursive mutexes
                /* wake up the other threads */
+               Thread *curr_thrd = get_thread(curr);
                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 */
-
                break;
        }
        case ATOMIC_NOTIFY_ALL: {
-               action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
+               simple_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());
+               simple_action_list_t *waiters = get_safe_ptr_action(&condvar_waiters_map, curr->get_location());
                if (waiters->size() != 0) {
                        Thread * thread = fuzzer->selectNotify(waiters);
                        scheduler->wake(thread);
@@ -427,7 +564,7 @@ void ModelExecution::process_write(ModelAction *curr)
  * @param curr The ModelAction to process
  * @return True if synchronization was updated
  */
-bool ModelExecution::process_fence(ModelAction *curr)
+void ModelExecution::process_fence(ModelAction *curr)
 {
        /*
         * fence-relaxed: no-op
@@ -437,36 +574,9 @@ bool ModelExecution::process_fence(ModelAction *curr)
         *   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 */
-                       ClockVector *cv = get_hb_from_write(act->get_reads_from());
-                       if (cv != NULL && curr->get_cv()->merge(cv))
-                               updated = true;
-               }
+               curr->get_cv()->merge(get_thread(curr)->get_acq_fence_cv());
        }
-       return updated;
 }
 
 /**
@@ -517,7 +627,7 @@ void ModelExecution::process_thread_action(ModelAction *curr)
                Thread *blocking = curr->get_thread_operand();
                ModelAction *act = get_last_action(blocking->get_id());
                synchronize(act, curr);
-               break;  // WL: to be add (modified)
+               break;
        }
 
        case THREADONLY_FINISH:
@@ -543,6 +653,12 @@ void ModelExecution::process_thread_action(ModelAction *curr)
        case THREAD_START: {
                break;
        }
+       case THREAD_SLEEP: {
+               Thread *th = get_thread(curr);
+               th->set_pending(curr);
+               scheduler->add_sleep(th);
+               break;
+       }
        default:
                break;
        }
@@ -622,7 +738,7 @@ void ModelExecution::read_from(ModelAction *act, 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);
@@ -640,16 +756,36 @@ bool ModelExecution::synchronize(const ModelAction *first, ModelAction *second)
  * @return a bool that indicates whether the action is enabled.
  */
 bool ModelExecution::check_action_enabled(ModelAction *curr) {
-       if (curr->is_lock()) {
+       switch (curr->get_type()) {
+       case ATOMIC_LOCK: {
                cdsc::mutex *lock = curr->get_mutex();
                struct cdsc::mutex_state *state = lock->get_state();
-               if (state->locked)
+               if (state->locked) {
+                       Thread *lock_owner = (Thread *)state->locked;
+                       Thread *curr_thread = get_thread(curr);
+                       if (lock_owner == curr_thread && state->type == PTHREAD_MUTEX_RECURSIVE) {
+                               return true;
+                       }
+
                        return false;
-       } else if (curr->is_thread_join()) {
+               }
+               break;
+       }
+       case THREAD_JOIN:
+       case PTHREAD_JOIN: {
                Thread *blocking = curr->get_thread_operand();
                if (!blocking->is_complete()) {
                        return false;
                }
+               break;
+       }
+       case THREAD_SLEEP: {
+               if (!fuzzer->shouldSleep(curr))
+                       return false;
+               break;
+       }
+       default:
+               return true;
        }
 
        return true;
@@ -669,34 +805,35 @@ bool ModelExecution::check_action_enabled(ModelAction *curr) {
 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);
 
-       /* Add the action to lists before any other model-checking tasks */
-       if (!second_part_of_rmw && curr->get_type() != NOOP)
-               add_action_to_lists(curr);
-
-       if (curr->is_write())
-               add_write_to_lists(curr);
-
        SnapVector<ModelAction *> * rf_set = NULL;
+       bool canprune = false;
        /* Build may_read_from set for newly-created actions */
-       if (newly_explored && curr->is_read())
+       if (curr->is_read() && newly_explored) {
                rf_set = build_may_read_from(curr);
-
-       process_thread_action(curr);
-
-       if (curr->is_read() && !second_part_of_rmw) {
-               process_read(curr, rf_set);
+               canprune = process_read(curr, rf_set);
                delete rf_set;
-       } else {
+       } else
                ASSERT(rf_set == NULL);
+
+       /* Add the action to lists if not the second part of a rmw */
+       if (newly_explored) {
+#ifdef COLLECT_STAT
+               record_atomic_stats(curr);
+#endif
+               add_action_to_lists(curr, canprune);
        }
 
+       if (curr->is_write())
+               add_write_to_lists(curr);
+
+       process_thread_action(curr);
+
        if (curr->is_write())
                process_write(curr);
 
@@ -709,42 +846,6 @@ ModelAction * ModelExecution::check_current_action(ModelAction *curr)
        return 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();
-}
-
-/**
- * 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 (priv->bad_synchronization)
-               ptr += sprintf(ptr, "[bad sw ordering]");
-       if (ptr != buf)
-               model_print("%s: %s", prefix ? prefix : "Infeasible", buf);
-}
-
-/**
- * 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 priv->bad_synchronization;
-}
-
 /** 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());
@@ -769,22 +870,36 @@ 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
  */
 
-bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf, SnapVector<const ModelAction *> * priorset, bool * canprune)
+bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *rf,
+                                                                                                                                                                       SnapVector<ModelAction *> * priorset, bool * canprune)
 {
        SnapVector<action_list_t> *thrd_lists = obj_thrd_map.get(curr->get_location());
-       unsigned int i;
        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);
 
        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();
+
+               fixup_action_list(thrd_lists);
+       }
+
        ModelAction *prev_same_thread = NULL;
        /* Iterate over all threads */
-       for (i = 0;i < thrd_lists->size();i++, tid = (((unsigned int)(tid+1)) == thrd_lists->size()) ? 0 : tid + 1) {
+       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 (i != 0)
@@ -804,9 +919,9 @@ bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *
 
                /* Iterate over actions in thread, starting from most recent */
                action_list_t *list = &(*thrd_lists)[tid];
-               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();
 
                        /* Skip curr */
                        if (act == curr)
@@ -862,7 +977,7 @@ bool ModelExecution::r_modification_order(ModelAction *curr, const ModelAction *
                                                return false;
                                        priorset->push_back(act);
                                } else {
-                                       const ModelAction *prevrf = act->get_reads_from();
+                                       ModelAction *prevrf = act->get_reads_from();
                                        if (!prevrf->equals(rf)) {
                                                if (mo_graph->checkReachable(rf, prevrf))
                                                        return false;
@@ -936,9 +1051,9 @@ void 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
@@ -992,43 +1107,6 @@ void ModelExecution::w_modification_order(ModelAction *curr)
 
 }
 
-/**
- * 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.
- *   If X --hb-> Y, A --rf-> Y, and A --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 = obj_thrd_map.get(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;
-}
-
 /**
  * Computes the clock vector that happens before propagates from this write.
  *
@@ -1066,9 +1144,17 @@ ClockVector * ModelExecution::get_hb_from_write(ModelAction *rf) const {
                        //operation that isn't release
                        if (rf->get_last_fence_release()) {
                                if (vec == NULL)
-                                       vec = rf->get_last_fence_release()->get_cv();
+                                       vec = new ClockVector(rf->get_last_fence_release()->get_cv(), NULL);
                                else
                                        (vec=new ClockVector(vec, NULL))->merge(rf->get_last_fence_release()->get_cv());
+                       } else {
+                               if (vec == NULL) {
+                                       if (rf->is_rmw()) {
+                                               vec = new ClockVector(NULL, NULL);
+                                       }
+                               } else {
+                                       vec = new ClockVector(vec, NULL);
+                               }
                        }
                        rf->set_rfcv(vec);
                }
@@ -1090,50 +1176,35 @@ ClockVector * ModelExecution::get_hb_from_write(ModelAction *rf) const {
  *
  * @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);
-               SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, act->get_location());
-               if (uninit_id >= (int)vec->size()) {
-                 int oldsize = (int) vec->size();
-                 vec->resize(uninit_id + 1);
-                 for(int i=oldsize; i<uninit_id+1; i++)
-                   new (&vec[i]) action_list_t(); 
-               }
-               (*vec)[uninit_id].push_front(uninit);
+       if ((act->is_fence() && act->is_seqcst()) || act->is_unlock()) {
+               simple_action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
+               act->setActionRef(list->add_back(act));
        }
-       list->push_back(act);
 
        // Update action trace, a total order of all actions
-       action_trace.push_back(act);
-       if (uninit)
-               action_trace.push_front(uninit);
+       action_trace.addAction(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(); 
+       if ((int)vec->size() <= tid) {
+               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();
+
+               fixup_action_list(vec);
        }
-       (*vec)[tid].push_back(act);
-       if (uninit)
-               (*vec)[uninit_id].push_front(uninit);
+       if (!canprune && (act->is_read() || act->is_write()))
+               (*vec)[tid].addAction(act);
 
-       // Update thrd_last_action, the last action taken by each thrad
+       // 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()) {
@@ -1144,53 +1215,17 @@ 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);
-
-               SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, mutex_loc);
-               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(); 
-               }
-               (*vec)[tid].push_back(act);
+               act->setActionRef(get_safe_ptr_action(&obj_map, mutex_loc)->add_back(act));
        }
 }
 
 void insertIntoActionList(action_list_t *list, ModelAction *act) {
-       action_list_t::reverse_iterator rit = list->rbegin();
-       modelclock_t next_seq = act->get_seq_number();
-       if (rit == list->rend() || (*rit)->get_seq_number() == next_seq)
-               list->push_back(act);
-       else {
-               for(;rit != list->rend();rit++) {
-                       if ((*rit)->get_seq_number() == next_seq) {
-                               action_list_t::iterator it = rit.base();
-                               list->insert(it, act);
-                               break;
-                       }
-               }
-       }
+       list->addAction(act);
 }
 
 void insertIntoActionListAndSetCV(action_list_t *list, ModelAction *act) {
-       action_list_t::reverse_iterator rit = list->rbegin();
-       modelclock_t next_seq = act->get_seq_number();
-       if (rit == list->rend()) {
-               act->create_cv(NULL);
-       } else if ((*rit)->get_seq_number() == next_seq) {
-               act->create_cv((*rit));
-               list->push_back(act);
-       } else {
-               for(;rit != list->rend();rit++) {
-                       if ((*rit)->get_seq_number() == next_seq) {
-                               act->create_cv((*rit));
-                               action_list_t::iterator it = rit.base();
-                               list->insert(it, act);
-                               break;
-                       }
-               }
-       }
+       act->create_cv(NULL);
+       list->addAction(act);
 }
 
 /**
@@ -1206,35 +1241,35 @@ void ModelExecution::add_normal_write_to_lists(ModelAction *act)
        int tid = id_to_int(act->get_tid());
        insertIntoActionListAndSetCV(&action_trace, act);
 
-       action_list_t *list = get_safe_ptr_action(&obj_map, act->get_location());
-       insertIntoActionList(list, 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();
+               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();
+
+               fixup_action_list(vec);
        }
        insertIntoActionList(&(*vec)[tid],act);
 
+       ModelAction * lastact = thrd_last_action[tid];
        // Update thrd_last_action, the last action taken by each thrad
-       if (thrd_last_action[tid]->get_seq_number() == act->get_seq_number())
+       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());
+       SnapVector<simple_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();
+               uint oldsize =vec->size();
+               vec->resize(priv->next_thread_id);
+               for(uint i=oldsize;i<priv->next_thread_id;i++)
+                       new (&(*vec)[i]) simple_action_list_t();
        }
-       (*vec)[tid].push_back(write);
+       write->setActionRef((*vec)[tid].add_back(write));
 }
 
 /**
@@ -1290,25 +1325,27 @@ ModelAction * ModelExecution::get_last_seq_cst_write(ModelAction *curr) const
 ModelAction * ModelExecution::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
 {
        /* All fences should have location FENCE_LOCATION */
-       action_list_t *list = obj_map.get(FENCE_LOCATION);
+       simple_action_list_t *list = obj_map.get(FENCE_LOCATION);
 
        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;
 }
 
@@ -1324,12 +1361,15 @@ ModelAction * ModelExecution::get_last_unlock(ModelAction *curr) const
 {
        void *location = curr->get_location();
 
-       action_list_t *list = obj_map.get(location);
+       simple_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;
 }
 
@@ -1377,7 +1417,7 @@ bool valequals(uint64_t val1, uint64_t val2, int size) {
  */
 SnapVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *curr)
 {
-       SnapVector<action_list_t> *thrd_lists = obj_wr_thrd_map.get(curr->get_location());
+       SnapVector<simple_action_list_t> *thrd_lists = obj_wr_thrd_map.get(curr->get_location());
        unsigned int i;
        ASSERT(curr->is_read());
 
@@ -1389,46 +1429,47 @@ SnapVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *cu
        SnapVector<ModelAction *> * rf_set = new SnapVector<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;
-
-                       if (act == curr)
-                               continue;
+       if (thrd_lists != NULL)
+               for (i = 0;i < thrd_lists->size();i++) {
+                       /* Iterate over actions in thread, starting from most recent */
+                       simple_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;
-
-                       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;
+                               /* 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 (allow_read) {
-                               /* Only add feasible reads */
-                               rf_set->push_back(act);
-                       }
+                               if (allow_read) {
+                                       /* Only add feasible reads */
+                                       rf_set->push_back(act);
+                               }
 
-                       /* 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");
@@ -1438,28 +1479,9 @@ SnapVector<ModelAction *> *  ModelExecution::build_may_read_from(ModelAction *cu
        return rf_set;
 }
 
-/**
- * @brief Get an action representing an uninitialized atomic
- *
- * This function may create a new one.
- *
- * @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(ModelAction *curr) const
-{
-       ModelAction *act = curr->get_uninit_action();
-       if (!act) {
-               act = new ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, curr->get_location(), params->uninitvalue, model_thread);
-               curr->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");
@@ -1467,18 +1489,18 @@ 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);
@@ -1487,8 +1509,8 @@ 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,
@@ -1512,7 +1534,7 @@ 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];
@@ -1523,13 +1545,11 @@ 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);
@@ -1537,6 +1557,40 @@ void ModelExecution::print_summary() const
 
 }
 
+void ModelExecution::print_tail()
+{
+       model_print("Execution trace %d:\n", get_execution_number());
+
+       sllnode<ModelAction*> *it;
+
+       model_print("------------------------------------------------------------------------------------\n");
+       model_print("#    t    Action type     MO       Location         Value               Rf  CV\n");
+       model_print("------------------------------------------------------------------------------------\n");
+
+       unsigned int hash = 0;
+
+       int length = 25;
+       int counter = 0;
+       SnapList<ModelAction *> list;
+       for (it = action_trace.end();it != NULL;it = it->getPrev()) {
+               if (counter > length)
+                       break;
+
+               ModelAction * act = it->getVal();
+               list.push_front(act);
+               counter++;
+       }
+
+       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->getVal()->hash());
+       }
+       model_print("HASH %u\n", hash);
+       model_print("------------------------------------------------------------------------------------\n");
+}
+
 /**
  * Add a Thread to the system for the first time. Should only be called once
  * per thread.
@@ -1581,14 +1635,21 @@ Thread * ModelExecution::get_thread(const ModelAction *act) const
  * @return A Thread reference
  */
 Thread * ModelExecution::get_pthread(pthread_t pid) {
+       // pid 1 is reserved for the main thread, pthread ids should start from 2
+       if (pid == 1)
+               return get_thread(pid);
+
        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;
+
+       if (thread_id < pthread_counter + 1)
+               return pthread_map[thread_id];
+       else
+               return NULL;
 }
 
 /**
@@ -1652,15 +1713,285 @@ Thread * ModelExecution::take_step(ModelAction *curr)
        curr = check_current_action(curr);
        ASSERT(curr);
 
-       /* Process this action in ModelHistory for records*/
+       /* Process this action in ModelHistory for records */
+#ifdef NEWFUZZER
        model->get_history()->process_action( curr, curr->get_tid() );
-
+#endif
        if (curr_thrd->is_blocked() || curr_thrd->is_complete())
                scheduler->remove_thread(curr_thrd);
 
        return action_select_next_thread(curr);
 }
 
+/** This method removes references to an Action before we delete it. */
+
+void ModelExecution::removeAction(ModelAction *act) {
+       {
+               action_trace.removeAction(act);
+       }
+       {
+               SnapVector<action_list_t> *vec = get_safe_ptr_vect_action(&obj_thrd_map, act->get_location());
+               (*vec)[act->get_tid()].removeAction(act);
+       }
+       if ((act->is_fence() && act->is_seqcst()) || act->is_unlock()) {
+               sllnode<ModelAction *> * listref = act->getActionRef();
+               if (listref != NULL) {
+                       simple_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<simple_action_list_t> *vec = get_safe_ptr_vect_action(&obj_wr_thrd_map, act->get_location());
+                       (*vec)[act->get_tid()].erase(listref);
+               }
+
+               //Clear it from last_sc_map
+               if (obj_last_sc_map.get(act->get_location()) == act) {
+                       obj_last_sc_map.remove(act->get_location());
+               }
+
+               //Remove from Cyclegraph
+               mo_graph->freeAction(act);
+       }
+}
+
+/** Computes clock vector that all running threads have already synchronized to.  */
+
+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->is_complete())
+                       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;
+}
+
+
+/** Sometimes we need to remove an action that is the most recent in the thread.  This happens if it is mo before action in other threads.  In that case we need to create a replacement latest ModelAction */
+
+void ModelExecution::fixupLastAct(ModelAction *act) {
+       ModelAction *newact = new ModelAction(ATOMIC_NOP, std::memory_order_seq_cst, NULL, VALUE_NONE, get_thread(act->get_tid()));
+       newact->set_seq_number(get_next_seq_num());
+       newact->create_cv(act);
+       newact->set_last_fence_release(act->get_last_fence_release());
+       add_action_to_lists(newact, false);
+}
+
+/** Compute which actions to free.  */
+
+void ModelExecution::collectActions() {
+       if (priv->used_sequence_numbers < params->traceminsize)
+               return;
+
+       //Compute minimal clock vector for all live threads
+       ClockVector *cvmin = computeMinimalCV();
+       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);
+
+               //Free if it is invisible or we have set a flag to remove visible actions.
+               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);
+                                               }
+                                       }
+                               }
+                       }
+               }
+       }
+
+       //We may need to remove read actions in the window we don't delete to preserve correctness.
+
+       for (sllnode<ModelAction*> * it2 = action_trace.end();it2 != it;) {
+               ModelAction *act = it2->getVal();
+               //Do iteration early in case we delete the act
+               it2=it2->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 (act->get_reads_from()->is_free()) {
+                               if (act->is_rmw()) {
+                                       //Weaken a RMW from a freed store to a write
+                                       act->set_type(ATOMIC_WRITE);
+                               } else {
+                                       removeAction(act);
+                                       if (islastact) {
+                                               fixupLastAct(act);
+                                       }
+
+                                       delete act;
+                                       continue;
+                               }
+                       }
+               }
+               //If we don't delete the action, we should remove references to release fences
+
+               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);
+               }
+       }
+       //Now we are in the window of old actions that we remove if possible
+       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 (act->get_reads_from()->is_free()) {
+                               if (act->is_rmw()) {
+                                       act->set_type(ATOMIC_WRITE);
+                               } else {
+                                       removeAction(act);
+                                       if (islastact) {
+                                               fixupLastAct(act);
+                                       }
+                                       delete act;
+                                       continue;
+                               }
+                       }
+               } else if (act->is_free()) {
+                       removeAction(act);
+                       if (islastact) {
+                               fixupLastAct(act);
+                       }
+                       delete act;
+                       continue;
+               } else if (act->is_write()) {
+                       //Do nothing with write that hasn't been marked to be freed
+               } else if (islastact) {
+                       //Keep the last action for non-read/write actions
+               } 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);
+                               // Remove reference to act from thrd_last_fence_release
+                               int thread_id = id_to_int( act->get_tid() );
+                               if (thrd_last_fence_release[thread_id] == act) {
+                                       thrd_last_fence_release[thread_id] = NULL;
+                               }
+                               delete act;
+                               continue;
+                       }
+               } else {
+                       //need to deal with lock, annotation, wait, notify, thread create, start, join, yield, finish, nops
+                       //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;
+                                       continue;
+                               }
+                       } else if (act->is_create()) {
+                               if (act->get_thread_operand()->is_complete()) {
+                                       removeAction(act);
+                                       delete act;
+                                       continue;
+                               }
+                       } else {
+                               removeAction(act);
+                               delete act;
+                               continue;
+                       }
+               }
+
+               //If we don't delete the action, we should remove references to release fences
+               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);
+               }
+       }
+
+       delete cvmin;
+       delete queue;
+}
+
 Fuzzer * ModelExecution::getFuzzer() {
        return fuzzer;
 }