model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "action.h"
   5 #include "tree.h"
   6 #include "schedule.h"
   7 #include "common.h"
   8
   9 #define INITIAL_THREAD_ID       0
  10
  11 class Backtrack {
  12 public:
  13         Backtrack(ModelAction *d, action_list_t *t) {
  14                 diverge = d;
  15                 actionTrace = t;
  16                 iter = actionTrace->begin();
  17         }
  18         ModelAction * get_diverge() { return diverge; }
  19         action_list_t * get_trace() { return actionTrace; }
  20         void advance_state() { iter++; }
  21         ModelAction * get_state() {
  22                 return iter == actionTrace->end() ? NULL : *iter;
  23         }
  24 private:
  25         ModelAction *diverge;
  26         action_list_t *actionTrace;
  27         /* points to position in actionTrace as we replay */
  28         action_list_t::iterator iter;
  29 };
  30
  31 ModelChecker *model;
  32
  33 ModelChecker::ModelChecker()
  34 {
  35         /* First thread created will have id INITIAL_THREAD_ID */
  36         this->next_thread_id = INITIAL_THREAD_ID;
  37         used_sequence_numbers = 0;
  38         /* Initialize default scheduler */
  39         this->scheduler = new Scheduler();
  40
  41         num_executions = 0;
  42         this->current_action = NULL;
  43         this->exploring = NULL;
  44         this->nextThread = THREAD_ID_T_NONE;
  45
  46         rootNode = new TreeNode();
  47         currentNode = rootNode;
  48         action_trace = new action_list_t();
  49 }
  50
  51 ModelChecker::~ModelChecker()
  52 {
  53         delete action_trace;
  54         delete this->scheduler;
  55         delete rootNode;
  56 }
  57
  58 void ModelChecker::reset_to_initial_state()
  59 {
  60         DEBUG("+++ Resetting to initial state +++\n");
  61         std::map<int, class Thread *>::iterator it;
  62         for (it = thread_map.begin(); it != thread_map.end(); it++)
  63                 delete (*it).second;
  64         thread_map.clear();
  65         action_trace = new action_list_t();
  66         currentNode = rootNode;
  67         current_action = NULL;
  68         next_thread_id = INITIAL_THREAD_ID;
  69         used_sequence_numbers = 0;
  70         /* scheduler reset ? */
  71 }
  72
  73 thread_id_t ModelChecker::get_next_id()
  74 {
  75         return next_thread_id++;
  76 }
  77
  78 int ModelChecker::get_next_seq_num()
  79 {
  80         return ++used_sequence_numbers;
  81 }
  82
  83 Thread * ModelChecker::schedule_next_thread()
  84 {
  85         Thread *t;
  86         if (nextThread == THREAD_ID_T_NONE)
  87                 return NULL;
  88         t = thread_map[id_to_int(nextThread)];
  89         if (t == NULL)
  90                 DEBUG("*** error: thread not in thread_map: id = %d\n", nextThread);
  91         return t;
  92 }
  93
  94 /*
  95  * get_next_replay_thread() - Choose the next thread in the replay sequence
  96  *
  97  * If we've reached the 'diverge' point, then we pick a thread from the
  98  *   backtracking set.
  99  * Otherwise, we simply return the next thread in the sequence.
 100  */
 101 thread_id_t ModelChecker::get_next_replay_thread()
 102 {
 103         ModelAction *next;
 104         thread_id_t tid;
 105
 106         next = exploring->get_state();
 107
 108         if (next == exploring->get_diverge()) {
 109                 TreeNode *node = next->get_node();
 110
 111                 /* Reached divergence point; discard our current 'exploring' */
 112                 DEBUG("*** Discard 'Backtrack' object ***\n");
 113                 tid = node->getNextBacktrack();
 114                 delete exploring;
 115                 exploring = NULL;
 116         } else {
 117                 tid = next->get_tid();
 118         }
 119         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 120         return tid;
 121 }
 122
 123 thread_id_t ModelChecker::advance_backtracking_state()
 124 {
 125         /* Have we completed exploring the preselected path? */
 126         if (exploring == NULL)
 127                 return THREAD_ID_T_NONE;
 128
 129         /* Else, we are trying to replay an execution */
 130         exploring->advance_state();
 131
 132         ASSERT(exploring->get_state() != NULL);
 133
 134         return get_next_replay_thread();
 135 }
 136
 137 bool ModelChecker::next_execution()
 138 {
 139         DBG();
 140
 141         num_executions++;
 142         print_summary();
 143         if ((exploring = model->get_next_backtrack()) == NULL)
 144                 return false;
 145
 146         if (DBG_ENABLED()) {
 147                 printf("Next execution will diverge at:\n");
 148                 exploring->get_diverge()->print();
 149                 print_list(exploring->get_trace());
 150         }
 151
 152         model->reset_to_initial_state();
 153         nextThread = get_next_replay_thread();
 154         return true;
 155 }
 156
 157 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 158 {
 159         action_type type = act->get_type();
 160
 161         switch (type) {
 162                 case THREAD_CREATE:
 163                 case THREAD_YIELD:
 164                 case THREAD_JOIN:
 165                         return NULL;
 166                 case ATOMIC_READ:
 167                 case ATOMIC_WRITE:
 168                 default:
 169                         break;
 170         }
 171         /* linear search: from most recent to oldest */
 172         action_list_t::reverse_iterator rit;
 173         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 174                 ModelAction *prev = *rit;
 175                 if (act->is_dependent(prev))
 176                         return prev;
 177         }
 178         return NULL;
 179 }
 180
 181 void ModelChecker::set_backtracking(ModelAction *act)
 182 {
 183         ModelAction *prev;
 184         TreeNode *node;
 185         Thread *t = get_thread(act->get_tid());
 186
 187         prev = get_last_conflict(act);
 188         if (prev == NULL)
 189                 return;
 190
 191         node = prev->get_node();
 192
 193         while (t && !node->is_enabled(t))
 194                 t = t->get_parent();
 195
 196         /* Check if this has been explored already */
 197         if (node->hasBeenExplored(t->get_id()))
 198                 return;
 199         /* If this is a new backtracking point, mark the tree */
 200         if (node->setBacktrack(t->get_id()) != 0)
 201                 return;
 202
 203         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 204                         prev->get_tid(), t->get_id());
 205         if (DBG_ENABLED()) {
 206                 prev->print();
 207                 act->print();
 208         }
 209
 210         Backtrack *back = new Backtrack(prev, action_trace);
 211         backtrack_list.push_back(back);
 212 }
 213
 214 Backtrack * ModelChecker::get_next_backtrack()
 215 {
 216         Backtrack *next;
 217         if (backtrack_list.empty())
 218                 return NULL;
 219         next = backtrack_list.back();
 220         backtrack_list.pop_back();
 221         return next;
 222 }
 223
 224 void ModelChecker::check_current_action(void)
 225 {
 226         ModelAction *next = this->current_action;
 227
 228         if (!next) {
 229                 DEBUG("trying to push NULL action...\n");
 230                 return;
 231         }
 232         current_action = NULL;
 233         nextThread = advance_backtracking_state();
 234         next->set_node(currentNode);
 235         set_backtracking(next);
 236         currentNode = currentNode->explore_child(next);
 237         this->action_trace->push_back(next);
 238 }
 239
 240 void ModelChecker::print_summary(void)
 241 {
 242         printf("\n");
 243         printf("Number of executions: %d\n", num_executions);
 244         printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
 245
 246         scheduler->print();
 247
 248         print_list(action_trace);
 249         printf("\n");
 250
 251 }
 252
 253 void ModelChecker::print_list(action_list_t *list)
 254 {
 255         action_list_t::iterator it;
 256
 257         printf("---------------------------------------------------------------------\n");
 258         printf("Trace:\n");
 259
 260         for (it = list->begin(); it != list->end(); it++) {
 261                 (*it)->print();
 262         }
 263         printf("---------------------------------------------------------------------\n");
 264 }
 265
 266 int ModelChecker::add_thread(Thread *t)
 267 {
 268         thread_map[id_to_int(t->get_id())] = t;
 269         scheduler->add_thread(t);
 270         return 0;
 271 }
 272
 273 void ModelChecker::remove_thread(Thread *t)
 274 {
 275         scheduler->remove_thread(t);
 276 }
 277
 278 int ModelChecker::switch_to_master(ModelAction *act)
 279 {
 280         Thread *old;
 281
 282         DBG();
 283         old = thread_current();
 284         set_current_action(act);
 285         old->set_state(THREAD_READY);
 286         return Thread::swap(old, get_system_context());
 287 }
 288
 289 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 290 {
 291         Thread *t = thread_current();
 292         ModelAction *act = this;
 293
 294         act->type = type;
 295         act->order = order;
 296         act->location = loc;
 297         act->tid = t->get_id();
 298         act->value = value;
 299         act->seq_number = model->get_next_seq_num();
 300 }
 301
 302 bool ModelAction::is_read()
 303 {
 304         return type == ATOMIC_READ;
 305 }
 306
 307 bool ModelAction::is_write()
 308 {
 309         return type == ATOMIC_WRITE;
 310 }
 311
 312 bool ModelAction::is_acquire()
 313 {
 314         switch (order) {
 315         case memory_order_acquire:
 316         case memory_order_acq_rel:
 317         case memory_order_seq_cst:
 318                 return true;
 319         default:
 320                 return false;
 321         }
 322 }
 323
 324 bool ModelAction::is_release()
 325 {
 326         switch (order) {
 327         case memory_order_release:
 328         case memory_order_acq_rel:
 329         case memory_order_seq_cst:
 330                 return true;
 331         default:
 332                 return false;
 333         }
 334 }
 335
 336 bool ModelAction::same_var(ModelAction *act)
 337 {
 338         return location == act->location;
 339 }
 340
 341 bool ModelAction::same_thread(ModelAction *act)
 342 {
 343         return tid == act->tid;
 344 }
 345
 346 bool ModelAction::is_dependent(ModelAction *act)
 347 {
 348         if (!is_read() && !is_write())
 349                 return false;
 350         if (!act->is_read() && !act->is_write())
 351                 return false;
 352         if (same_var(act) && !same_thread(act) &&
 353                         (is_write() || act->is_write()))
 354                 return true;
 355         return false;
 356 }
 357
 358 void ModelAction::print(void)
 359 {
 360         const char *type_str;
 361         switch (this->type) {
 362         case THREAD_CREATE:
 363                 type_str = "thread create";
 364                 break;
 365         case THREAD_YIELD:
 366                 type_str = "thread yield";
 367                 break;
 368         case THREAD_JOIN:
 369                 type_str = "thread join";
 370                 break;
 371         case ATOMIC_READ:
 372                 type_str = "atomic read";
 373                 break;
 374         case ATOMIC_WRITE:
 375                 type_str = "atomic write";
 376                 break;
 377         default:
 378                 type_str = "unknown type";
 379         }
 380
 381         printf("(%4d) Thread: %d\tAction: %s\tMO: %d\tLoc: %14p\tValue: %d\n",
 382                         seq_number, id_to_int(tid), type_str, order, location, value);
 383 }