history.cc

   1 #include <inttypes.h>
   2 #include "history.h"
   3 #include "action.h"
   4 #include "funcnode.h"
   5 #include "funcinst.h"
   6 #include "common.h"
   7 #include "concretepredicate.h"
   8 #include "waitobj.h"
   9
  10 #include "model.h"
  11 #include "execution.h"
  12 #include "newfuzzer.h"
  13
  14 /** @brief Constructor */
  15 ModelHistory::ModelHistory() :
  16         func_counter(1),        /* function id starts with 1 */
  17         func_map(),
  18         func_map_rev(),
  19         func_nodes()
  20 {
  21         /* The following are snapshot data structures */
  22         write_history = new HashTable<void *, value_set_t *, uintptr_t, 0>();
  23         loc_rd_func_nodes_map = new HashTable<void *, SnapVector<FuncNode *> *, uintptr_t, 0>();
  24         loc_wr_func_nodes_map = new HashTable<void *, SnapVector<FuncNode *> *, uintptr_t, 0>();
  25         loc_waiting_writes_map = new HashTable<void *, SnapVector<ConcretePredicate *> *, uintptr_t, 0>();
  26         thrd_func_act_lists = new SnapVector< SnapList<action_list_t *> *>();
  27         thrd_func_list = new SnapVector<func_id_list_t>();
  28         thrd_last_entered_func = new SnapVector<uint32_t>();
  29         thrd_waiting_write = new SnapVector<ConcretePredicate *>();
  30         thrd_wait_obj = new SnapVector<WaitObj *>();
  31         func_inst_act_maps = new HashTable<uint32_t, SnapVector<inst_act_map_t *> *, int, 0>(128);
  32 }
  33
  34 ModelHistory::~ModelHistory()
  35 {
  36         // TODO: complete deconstructor; maybe not needed
  37         for (uint i = 0;i < thrd_wait_obj->size();i++)
  38                 delete (*thrd_wait_obj)[i];
  39 }
  40
  41 void ModelHistory::enter_function(const uint32_t func_id, thread_id_t tid)
  42 {
  43         //model_print("thread %d entering func %d\n", tid, func_id);
  44         uint id = id_to_int(tid);
  45
  46         if ( thrd_func_list->size() <= id ) {
  47                 uint oldsize = thrd_func_list->size();
  48                 thrd_func_list->resize( id + 1 );
  49                 thrd_func_act_lists->resize( id + 1 );
  50
  51                 for (uint i = oldsize;i < id + 1;i++) {
  52                         // push 0 as a dummy function id to a void seg fault
  53                         new (&(*thrd_func_list)[i]) func_id_list_t();
  54                         (*thrd_func_list)[i].push_back(0);
  55
  56                         (*thrd_func_act_lists)[i] = new SnapList<action_list_t *>();
  57                         thrd_last_entered_func->push_back(0);
  58                 }
  59         }
  60
  61         SnapList<action_list_t *> * func_act_lists = (*thrd_func_act_lists)[id];
  62         func_act_lists->push_back( new action_list_t() );
  63
  64         uint32_t last_entered_func_id = (*thrd_last_entered_func)[id];
  65         (*thrd_last_entered_func)[id] = func_id;
  66         (*thrd_func_list)[id].push_back(func_id);
  67
  68         if ( func_nodes.size() <= func_id )
  69                 resize_func_nodes( func_id + 1 );
  70
  71         FuncNode * func_node = func_nodes[func_id];
  72         func_node->init_predicate_tree_position(tid);
  73         func_node->init_inst_act_map(tid);
  74
  75         /* Add edges between FuncNodes */
  76         if (last_entered_func_id != 0) {
  77                 FuncNode * last_func_node = func_nodes[last_entered_func_id];
  78                 last_func_node->add_out_edge(func_node);
  79         }
  80
  81         /* Monitor the statuses of threads waiting for tid */
  82         // monitor_waiting_thread(func_id, tid);
  83 }
  84
  85 /* @param func_id a non-zero value */
  86 void ModelHistory::exit_function(const uint32_t func_id, thread_id_t tid)
  87 {
  88         uint32_t id = id_to_int(tid);
  89
  90         SnapList<action_list_t *> * func_act_lists = (*thrd_func_act_lists)[id];
  91         uint32_t last_func_id = (*thrd_func_list)[id].back();
  92
  93         if (last_func_id == func_id) {
  94                 FuncNode * func_node = func_nodes[func_id];
  95                 func_node->set_predicate_tree_position(tid, NULL);
  96                 func_node->reset_inst_act_map(tid);
  97
  98                 action_list_t * curr_act_list = func_act_lists->back();
  99
 100                 /* defer the processing of curr_act_list until the function has exits a few times
 101                  * (currently twice) so that more information can be gathered to infer nullity predicates.
 102                  */
 103                 func_node->incr_exit_count();
 104                 if (func_node->get_exit_count() >= 2) {
 105                         SnapList<action_list_t *> * action_list_buffer = func_node->get_action_list_buffer();
 106                         while (action_list_buffer->size() > 0) {
 107                                 action_list_t * act_list = action_list_buffer->back();
 108                                 action_list_buffer->pop_back();
 109                                 func_node->update_tree(act_list);
 110                         }
 111
 112                         func_node->update_tree(curr_act_list);
 113                 } else
 114                         func_node->get_action_list_buffer()->push_front(curr_act_list);
 115
 116                 (*thrd_func_list)[id].pop_back();
 117                 func_act_lists->pop_back();
 118         } else {
 119                 model_print("trying to exit with a wrong function id\n");
 120                 model_print("--- last_func: %d, func_id: %d\n", last_func_id, func_id);
 121         }
 122         //model_print("thread %d exiting func %d\n", tid, func_id);
 123 }
 124
 125 void ModelHistory::resize_func_nodes(uint32_t new_size)
 126 {
 127         uint32_t old_size = func_nodes.size();
 128
 129         if ( old_size < new_size )
 130                 func_nodes.resize(new_size);
 131
 132         for (uint32_t id = old_size;id < new_size;id++) {
 133                 const char * func_name = func_map_rev[id];
 134                 FuncNode * func_node = new FuncNode(this);
 135                 func_node->set_func_id(id);
 136                 func_node->set_func_name(func_name);
 137                 func_nodes[id] = func_node;
 138         }
 139 }
 140
 141 void ModelHistory::process_action(ModelAction *act, thread_id_t tid)
 142 {
 143         uint32_t thread_id = id_to_int(tid);
 144         /* Return if thread tid has not entered any function that contains atomics */
 145         if ( thrd_func_list->size() <= thread_id )
 146                 return;
 147
 148         /* Monitor the statuses of threads waiting for tid */
 149         // monitor_waiting_thread_counter(tid);
 150
 151         /* Every write action should be processed, including
 152          * nonatomic writes (which have no position) */
 153         if (act->is_write()) {
 154                 void * location = act->get_location();
 155                 uint64_t value = act->get_write_value();
 156                 update_write_history(location, value);
 157
 158                 /* Notify FuncNodes that may read from this location */
 159                 SnapVector<FuncNode *> * func_node_list = getRdFuncNodes(location);
 160                 for (uint i = 0;i < func_node_list->size();i++) {
 161                         FuncNode * func_node = (*func_node_list)[i];
 162                         func_node->add_to_val_loc_map(value, location);
 163                 }
 164
 165                 // check_waiting_write(act);
 166         }
 167
 168         uint32_t func_id = (*thrd_func_list)[thread_id].back();
 169
 170         /* The following does not care about actions that are not inside
 171          * any function that contains atomics or actions without a position */
 172         if (func_id == 0 || act->get_position() == NULL)
 173                 return;
 174
 175         SnapList<action_list_t *> * func_act_lists = (*thrd_func_act_lists)[thread_id];
 176
 177         /* The list of actions that thread tid has taken in its current function */
 178         action_list_t * curr_act_list = func_act_lists->back();
 179
 180         if (skip_action(act, curr_act_list))
 181                 return;
 182
 183         /* Add to curr_inst_list */
 184         curr_act_list->push_back(act);
 185
 186         // Increment ref count for every action and reads_froms
 187         act->incr_func_ref_count();
 188         if (act->is_read()) {
 189                 ModelAction * rf = act->get_reads_from();
 190                 rf->incr_func_ref_count();
 191         }
 192
 193         FuncNode * func_node = func_nodes[func_id];
 194         func_node->add_inst(act);
 195
 196         if (act->is_read()) {
 197                 func_node->update_inst_act_map(tid, act);
 198
 199                 Fuzzer * fuzzer = model->get_execution()->getFuzzer();
 200                 Predicate * selected_branch = ((NewFuzzer *)fuzzer)->get_selected_child_branch(tid);
 201                 func_node->set_predicate_tree_position(tid, selected_branch);
 202         }
 203
 204         if (act->is_write()) {
 205                 Predicate * curr_pred = func_node->get_predicate_tree_position(tid);
 206                 FuncInst * curr_inst = func_node->get_inst(act);
 207
 208                 if (curr_pred) {
 209                         // Follow child
 210                         curr_pred = curr_pred->follow_write_child(curr_inst);
 211                 }
 212                 func_node->set_predicate_tree_position(tid, curr_pred);
 213         }
 214 }
 215
 216 /* Return the FuncNode given its func_id  */
 217 FuncNode * ModelHistory::get_func_node(uint32_t func_id)
 218 {
 219         if (func_id == 0)
 220                 return NULL;
 221
 222         // This node has not been added to func_nodes
 223         if (func_nodes.size() <= func_id)
 224                 return NULL;
 225
 226         return func_nodes[func_id];
 227 }
 228
 229 /* Return the current FuncNode when given a thread id */
 230 FuncNode * ModelHistory::get_curr_func_node(thread_id_t tid)
 231 {
 232         int thread_id = id_to_int(tid);
 233         uint32_t func_id = (*thrd_func_list)[thread_id].back();
 234
 235         if (func_id != 0) {
 236                 return func_nodes[func_id];
 237         }
 238
 239         return NULL;
 240 }
 241
 242 void ModelHistory::update_write_history(void * location, uint64_t write_val)
 243 {
 244         value_set_t * write_set = write_history->get(location);
 245
 246         if (write_set == NULL) {
 247                 write_set = new value_set_t();
 248                 write_history->put(location, write_set);
 249         }
 250
 251         write_set->add(write_val);
 252 }
 253
 254 void ModelHistory::update_loc_rd_func_nodes_map(void * location, FuncNode * node)
 255 {
 256         SnapVector<FuncNode *> * func_node_list = getRdFuncNodes(location);
 257         func_node_list->push_back(node);
 258 }
 259
 260 void ModelHistory::update_loc_wr_func_nodes_map(void * location, FuncNode * node)
 261 {
 262         SnapVector<FuncNode *> * func_node_list = getWrFuncNodes(location);
 263         func_node_list->push_back(node);
 264 }
 265
 266 SnapVector<FuncNode *> * ModelHistory::getRdFuncNodes(void * location)
 267 {
 268         SnapVector<FuncNode *> * func_node_list = loc_rd_func_nodes_map->get(location);
 269         if (func_node_list == NULL) {
 270                 func_node_list = new SnapVector<FuncNode *>();
 271                 loc_rd_func_nodes_map->put(location, func_node_list);
 272         }
 273
 274         return func_node_list;
 275 }
 276
 277 SnapVector<FuncNode *> * ModelHistory::getWrFuncNodes(void * location)
 278 {
 279         SnapVector<FuncNode *> * func_node_list = loc_wr_func_nodes_map->get(location);
 280         if (func_node_list == NULL) {
 281                 func_node_list = new SnapVector<FuncNode *>();
 282                 loc_wr_func_nodes_map->put(location, func_node_list);
 283         }
 284
 285         return func_node_list;
 286 }
 287
 288 /* When a thread is paused by Fuzzer, keep track of the condition it is waiting for */
 289 void ModelHistory::add_waiting_write(ConcretePredicate * concrete)
 290 {
 291         void * location = concrete->get_location();
 292         SnapVector<ConcretePredicate *> * waiting_conditions = loc_waiting_writes_map->get(location);
 293         if (waiting_conditions == NULL) {
 294                 waiting_conditions = new SnapVector<ConcretePredicate *>();
 295                 loc_waiting_writes_map->put(location, waiting_conditions);
 296         }
 297
 298         /* waiting_conditions should not have duplications */
 299         waiting_conditions->push_back(concrete);
 300
 301         int thread_id = id_to_int(concrete->get_tid());
 302         if (thrd_waiting_write->size() <= (uint) thread_id) {
 303                 thrd_waiting_write->resize(thread_id + 1);
 304         }
 305
 306         (*thrd_waiting_write)[thread_id] = concrete;
 307 }
 308
 309 void ModelHistory::remove_waiting_write(thread_id_t tid)
 310 {
 311         ConcretePredicate * concrete = (*thrd_waiting_write)[ id_to_int(tid) ];
 312         void * location = concrete->get_location();
 313         SnapVector<ConcretePredicate *> * concrete_preds = loc_waiting_writes_map->get(location);
 314
 315         /* Linear search should be fine because presumably not many ConcretePredicates
 316          * are at the same memory location */
 317         for (uint i = 0;i < concrete_preds->size();i++) {
 318                 ConcretePredicate * current = (*concrete_preds)[i];
 319                 if (concrete == current) {
 320                         (*concrete_preds)[i] = concrete_preds->back();
 321                         concrete_preds->pop_back();
 322                         break;
 323                 }
 324         }
 325
 326         int thread_id = id_to_int( concrete->get_tid() );
 327         (*thrd_waiting_write)[thread_id] = NULL;
 328         delete concrete;
 329 }
 330
 331 /* Check if any other thread is waiting for this write action. If so, "notify" them */
 332 void ModelHistory::check_waiting_write(ModelAction * write_act)
 333 {
 334         void * location = write_act->get_location();
 335         uint64_t value = write_act->get_write_value();
 336         SnapVector<ConcretePredicate *> * concrete_preds = loc_waiting_writes_map->get(location);
 337         if (concrete_preds == NULL)
 338                 return;
 339
 340         uint index = 0;
 341         while (index < concrete_preds->size()) {
 342                 ConcretePredicate * concrete_pred = (*concrete_preds)[index];
 343                 SnapVector<struct concrete_pred_expr> * concrete_exprs = concrete_pred->getExpressions();
 344                 bool satisfy_predicate = true;
 345                 /* Check if the written value satisfies every predicate expression */
 346                 for (uint i = 0;i < concrete_exprs->size();i++) {
 347                         struct concrete_pred_expr concrete = (*concrete_exprs)[i];
 348                         bool equality = false;
 349                         switch (concrete.token) {
 350                         case EQUALITY:
 351                                 equality = (value == concrete.value);
 352                                 break;
 353                         case NULLITY:
 354                                 equality = ((void*)value == NULL);
 355                                 break;
 356                         default:
 357                                 model_print("unknown predicate token");
 358                                 break;
 359                         }
 360
 361                         if (equality != concrete.equality) {
 362                                 satisfy_predicate = false;
 363                                 break;
 364                         }
 365                 }
 366
 367                 if (satisfy_predicate) {
 368                         /* Wake up threads */
 369                         thread_id_t tid = concrete_pred->get_tid();
 370                         Thread * thread = model->get_thread(tid);
 371
 372                         //model_print("** thread %d is woken up\n", thread->get_id());
 373                         ((NewFuzzer *)model->get_execution()->getFuzzer())->notify_paused_thread(thread);
 374                 }
 375
 376                 index++;
 377         }
 378 }
 379
 380 WaitObj * ModelHistory::getWaitObj(thread_id_t tid)
 381 {
 382         int thread_id = id_to_int(tid);
 383         int old_size = thrd_wait_obj->size();
 384         if (old_size <= thread_id) {
 385                 thrd_wait_obj->resize(thread_id + 1);
 386                 for (int i = old_size;i < thread_id + 1;i++) {
 387                         (*thrd_wait_obj)[i] = new WaitObj( int_to_id(i) );
 388                 }
 389         }
 390
 391         return (*thrd_wait_obj)[thread_id];
 392 }
 393
 394 void ModelHistory::add_waiting_thread(thread_id_t self_id,
 395                                                                                                                                                         thread_id_t waiting_for_id, FuncNode * target_node, int dist)
 396 {
 397         WaitObj * self_wait_obj = getWaitObj(self_id);
 398         self_wait_obj->add_waiting_for(waiting_for_id, target_node, dist);
 399
 400         /* Update waited-by relation */
 401         WaitObj * other_wait_obj = getWaitObj(waiting_for_id);
 402         other_wait_obj->add_waited_by(self_id);
 403 }
 404
 405 /* Thread tid is woken up (or notified), so it is not waiting for others anymore */
 406 void ModelHistory::remove_waiting_thread(thread_id_t tid)
 407 {
 408         WaitObj * self_wait_obj = getWaitObj(tid);
 409         thrd_id_set_t * waiting_for = self_wait_obj->getWaitingFor();
 410
 411         /* Remove tid from waited_by's */
 412         thrd_id_set_iter * iter = waiting_for->iterator();
 413         while (iter->hasNext()) {
 414                 thread_id_t other_id = iter->next();
 415                 WaitObj * other_wait_obj = getWaitObj(other_id);
 416                 other_wait_obj->remove_waited_by(tid);
 417         }
 418
 419         self_wait_obj->clear_waiting_for();
 420         delete iter;
 421 }
 422
 423 void ModelHistory::stop_waiting_for_node(thread_id_t self_id,
 424                                                                                                                                                                  thread_id_t waiting_for_id, FuncNode * target_node)
 425 {
 426         WaitObj * self_wait_obj = getWaitObj(self_id);
 427         bool thread_removed = self_wait_obj->remove_waiting_for_node(waiting_for_id, target_node);
 428
 429         // model_print("\t%d gives up %d on node %d\n", self_id, waiting_for_id, target_node->get_func_id());
 430
 431         /* If thread self_id is not waiting for waiting_for_id anymore */
 432         if (thread_removed) {
 433                 WaitObj * other_wait_obj = getWaitObj(waiting_for_id);
 434                 other_wait_obj->remove_waited_by(self_id);
 435
 436                 thrd_id_set_t * self_waiting_for = self_wait_obj->getWaitingFor();
 437                 if ( self_waiting_for->isEmpty() ) {
 438                         // model_print("\tthread %d waits for nobody, wake up\n", self_id);
 439                         ModelExecution * execution = model->get_execution();
 440                         Thread * thread = execution->get_thread(self_id);
 441                         ((NewFuzzer *)execution->getFuzzer())->notify_paused_thread(thread);
 442                 }
 443         }
 444 }
 445
 446 SnapVector<inst_act_map_t *> * ModelHistory::getThrdInstActMap(uint32_t func_id)
 447 {
 448         ASSERT(func_id != 0);
 449
 450         SnapVector<inst_act_map_t *> * maps = func_inst_act_maps->get(func_id);
 451         if (maps == NULL) {
 452                 maps = new SnapVector<inst_act_map_t *>();
 453                 func_inst_act_maps->put(func_id, maps);
 454         }
 455
 456         return maps;
 457 }
 458
 459 bool ModelHistory::skip_action(ModelAction * act, SnapList<ModelAction *> * curr_act_list)
 460 {
 461         ASSERT(curr_act_list != NULL);
 462
 463         bool second_part_of_rmw = act->is_rmwc() || act->is_rmw();
 464         modelclock_t curr_seq_number = act->get_seq_number();
 465
 466         /* Skip actions that are second part of a read modify write */
 467         if (second_part_of_rmw)
 468                 return true;
 469
 470         /* Skip actions with the same sequence number */
 471         if (curr_act_list->size() != 0) {
 472                 ModelAction * last_act = curr_act_list->back();
 473                 if (last_act->get_seq_number() == curr_seq_number)
 474                         return true;
 475         }
 476
 477         /* Skip actions that are paused by fuzzer (sequence number is 0) */
 478         if (curr_seq_number == 0)
 479                 return true;
 480
 481         return false;
 482 }
 483
 484 /* Monitor thread tid and decide whether other threads (that are waiting for tid)
 485  * should keep waiting for this thread or not. Shall only be called when a thread
 486  * enters a function.
 487  *
 488  * Heuristics: If the distance from the current FuncNode to some target node
 489  * ever increases, stop waiting for this thread on this target node.
 490  */
 491 void ModelHistory::monitor_waiting_thread(uint32_t func_id, thread_id_t tid)
 492 {
 493         WaitObj * wait_obj = getWaitObj(tid);
 494         thrd_id_set_t * waited_by = wait_obj->getWaitedBy();
 495         FuncNode * curr_node = func_nodes[func_id];
 496
 497         /* For each thread waiting for tid */
 498         thrd_id_set_iter * tid_iter = waited_by->iterator();
 499         while (tid_iter->hasNext()) {
 500                 thread_id_t waited_by_id = tid_iter->next();
 501                 WaitObj * other_wait_obj = getWaitObj(waited_by_id);
 502
 503                 node_set_t * target_nodes = other_wait_obj->getTargetNodes(tid);
 504                 node_set_iter * node_iter = target_nodes->iterator();
 505                 while (node_iter->hasNext()) {
 506                         FuncNode * target = node_iter->next();
 507                         int old_dist = other_wait_obj->lookup_dist(tid, target);
 508                         int new_dist = curr_node->compute_distance(target, old_dist);
 509
 510                         if (new_dist == -1) {
 511                                 stop_waiting_for_node(waited_by_id, tid, target);
 512                         }
 513                 }
 514
 515                 delete node_iter;
 516         }
 517
 518         delete tid_iter;
 519 }
 520
 521 void ModelHistory::monitor_waiting_thread_counter(thread_id_t tid)
 522 {
 523         WaitObj * wait_obj = getWaitObj(tid);
 524         thrd_id_set_t * waited_by = wait_obj->getWaitedBy();
 525
 526         // Thread tid has taken an action, update the counter for threads waiting for tid
 527         thrd_id_set_iter * tid_iter = waited_by->iterator();
 528         while (tid_iter->hasNext()) {
 529                 thread_id_t waited_by_id = tid_iter->next();
 530                 WaitObj * other_wait_obj = getWaitObj(waited_by_id);
 531
 532                 bool expire = other_wait_obj->incr_counter(tid);
 533                 if (expire) {
 534 //                      model_print("thread %d stops waiting for thread %d\n", waited_by_id, tid);
 535                         wait_obj->remove_waited_by(waited_by_id);
 536                         other_wait_obj->remove_waiting_for(tid);
 537
 538                         thrd_id_set_t * other_waiting_for = other_wait_obj->getWaitingFor();
 539                         if ( other_waiting_for->isEmpty() ) {
 540                                 // model_print("\tthread %d waits for nobody, wake up\n", self_id);
 541                                 ModelExecution * execution = model->get_execution();
 542                                 Thread * thread = execution->get_thread(waited_by_id);
 543                                 ((NewFuzzer *)execution->getFuzzer())->notify_paused_thread(thread);
 544                         }
 545                 }
 546         }
 547
 548         delete tid_iter;
 549 }
 550
 551 /* Reallocate some snapshotted memories when new executions start */
 552 void ModelHistory::set_new_exec_flag()
 553 {
 554         for (uint i = 1;i < func_nodes.size();i++) {
 555                 FuncNode * func_node = func_nodes[i];
 556                 func_node->set_new_exec_flag();
 557         }
 558 }
 559
 560 void ModelHistory::dump_func_node_graph()
 561 {
 562         model_print("digraph func_node_graph {\n");
 563         for (uint i = 1;i < func_nodes.size();i++) {
 564                 FuncNode * node = func_nodes[i];
 565                 ModelList<FuncNode *> * out_edges = node->get_out_edges();
 566
 567                 model_print("\"%p\" [label=\"%s\"]\n", node, node->get_func_name());
 568                 mllnode<FuncNode *> * it;
 569                 for (it = out_edges->begin();it != NULL;it = it->getNext()) {
 570                         FuncNode * other = it->getVal();
 571                         model_print("\"%p\" -> \"%p\"\n", node, other);
 572                 }
 573         }
 574         model_print("}\n");
 575 }
 576
 577 void ModelHistory::print_func_node()
 578 {
 579         /* function id starts with 1 */
 580         for (uint32_t i = 1;i < func_nodes.size();i++) {
 581                 FuncNode * func_node = func_nodes[i];
 582                 func_node->print_predicate_tree();
 583
 584 /*
 585                 func_inst_list_mt * entry_insts = func_node->get_entry_insts();
 586                 model_print("function %s has entry actions\n", func_node->get_func_name());
 587
 588                 mllnode<FuncInst*>* it;
 589                 for (it = entry_insts->begin();it != NULL;it=it->getNext()) {
 590                         FuncInst *inst = it->getVal();
 591                         model_print("type: %d, at: %s\n", inst->get_type(), inst->get_position());
 592                 }
 593  */
 594         }
 595 }
 596
 597 void ModelHistory::print_waiting_threads()
 598 {
 599         ModelExecution * execution = model->get_execution();
 600         for (unsigned int i = 0;i < execution->get_num_threads();i++) {
 601                 thread_id_t tid = int_to_id(i);
 602                 WaitObj * wait_obj = getWaitObj(tid);
 603                 wait_obj->print_waiting_for();
 604         }
 605
 606         for (unsigned int i = 0;i < execution->get_num_threads();i++) {
 607                 thread_id_t tid = int_to_id(i);
 608                 WaitObj * wait_obj = getWaitObj(tid);
 609                 wait_obj->print_waited_by();
 610         }
 611 }