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         std::map<int, class Thread *>::iterator it;
  54         for (it = thread_map.begin(); it != thread_map.end(); it++)
  55                 delete (*it).second;
  56         thread_map.clear();
  57
  58         delete action_trace;
  59         delete this->scheduler;
  60         delete rootNode;
  61 }
  62
  63 void ModelChecker::reset_to_initial_state()
  64 {
  65         DEBUG("+++ Resetting to initial state +++\n");
  66         std::map<int, class Thread *>::iterator it;
  67         for (it = thread_map.begin(); it != thread_map.end(); it++)
  68                 delete (*it).second;
  69         thread_map.clear();
  70         action_trace = new action_list_t();
  71         currentNode = rootNode;
  72         current_action = NULL;
  73         next_thread_id = INITIAL_THREAD_ID;
  74         used_sequence_numbers = 0;
  75         /* scheduler reset ? */
  76 }
  77
  78 thread_id_t ModelChecker::get_next_id()
  79 {
  80         return next_thread_id++;
  81 }
  82
  83 int ModelChecker::get_next_seq_num()
  84 {
  85         return ++used_sequence_numbers;
  86 }
  87
  88 Thread * ModelChecker::schedule_next_thread()
  89 {
  90         Thread *t;
  91         if (nextThread == THREAD_ID_T_NONE)
  92                 return NULL;
  93         t = thread_map[id_to_int(nextThread)];
  94
  95         ASSERT(t != NULL);
  96
  97         return t;
  98 }
  99
 100 /*
 101  * get_next_replay_thread() - Choose the next thread in the replay sequence
 102  *
 103  * If we've reached the 'diverge' point, then we pick a thread from the
 104  *   backtracking set.
 105  * Otherwise, we simply return the next thread in the sequence.
 106  */
 107 thread_id_t ModelChecker::get_next_replay_thread()
 108 {
 109         ModelAction *next;
 110         thread_id_t tid;
 111
 112         next = exploring->get_state();
 113
 114         if (next == exploring->get_diverge()) {
 115                 TreeNode *node = next->get_node();
 116
 117                 /* Reached divergence point; discard our current 'exploring' */
 118                 DEBUG("*** Discard 'Backtrack' object ***\n");
 119                 tid = node->getNextBacktrack();
 120                 delete exploring;
 121                 exploring = NULL;
 122         } else {
 123                 tid = next->get_tid();
 124         }
 125         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 126         return tid;
 127 }
 128
 129 thread_id_t ModelChecker::advance_backtracking_state()
 130 {
 131         /* Have we completed exploring the preselected path? */
 132         if (exploring == NULL)
 133                 return THREAD_ID_T_NONE;
 134
 135         /* Else, we are trying to replay an execution */
 136         exploring->advance_state();
 137
 138         ASSERT(exploring->get_state() != NULL);
 139
 140         return get_next_replay_thread();
 141 }
 142
 143 bool ModelChecker::next_execution()
 144 {
 145         DBG();
 146
 147         num_executions++;
 148         print_summary();
 149         if ((exploring = model->get_next_backtrack()) == NULL)
 150                 return false;
 151
 152         if (DBG_ENABLED()) {
 153                 printf("Next execution will diverge at:\n");
 154                 exploring->get_diverge()->print();
 155                 print_list(exploring->get_trace());
 156         }
 157
 158         model->reset_to_initial_state();
 159         nextThread = get_next_replay_thread();
 160         return true;
 161 }
 162
 163 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 164 {
 165         action_type type = act->get_type();
 166
 167         switch (type) {
 168                 case THREAD_CREATE:
 169                 case THREAD_YIELD:
 170                 case THREAD_JOIN:
 171                         return NULL;
 172                 case ATOMIC_READ:
 173                 case ATOMIC_WRITE:
 174                 default:
 175                         break;
 176         }
 177         /* linear search: from most recent to oldest */
 178         action_list_t::reverse_iterator rit;
 179         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 180                 ModelAction *prev = *rit;
 181                 if (act->is_dependent(prev))
 182                         return prev;
 183         }
 184         return NULL;
 185 }
 186
 187 void ModelChecker::set_backtracking(ModelAction *act)
 188 {
 189         ModelAction *prev;
 190         TreeNode *node;
 191         Thread *t = get_thread(act->get_tid());
 192
 193         prev = get_last_conflict(act);
 194         if (prev == NULL)
 195                 return;
 196
 197         node = prev->get_node();
 198
 199         while (t && !node->is_enabled(t))
 200                 t = t->get_parent();
 201
 202         /* Check if this has been explored already */
 203         if (node->hasBeenExplored(t->get_id()))
 204                 return;
 205         /* If this is a new backtracking point, mark the tree */
 206         if (node->setBacktrack(t->get_id()) != 0)
 207                 return;
 208
 209         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 210                         prev->get_tid(), t->get_id());
 211         if (DBG_ENABLED()) {
 212                 prev->print();
 213                 act->print();
 214         }
 215
 216         Backtrack *back = new Backtrack(prev, action_trace);
 217         backtrack_list.push_back(back);
 218 }
 219
 220 Backtrack * ModelChecker::get_next_backtrack()
 221 {
 222         Backtrack *next;
 223         if (backtrack_list.empty())
 224                 return NULL;
 225         next = backtrack_list.back();
 226         backtrack_list.pop_back();
 227         return next;
 228 }
 229
 230 void ModelChecker::check_current_action(void)
 231 {
 232         ModelAction *next = this->current_action;
 233
 234         if (!next) {
 235                 DEBUG("trying to push NULL action...\n");
 236                 return;
 237         }
 238         current_action = NULL;
 239         nextThread = advance_backtracking_state();
 240         next->set_node(currentNode);
 241         set_backtracking(next);
 242         currentNode = currentNode->explore_child(next);
 243         this->action_trace->push_back(next);
 244 }
 245
 246 void ModelChecker::print_summary(void)
 247 {
 248         printf("\n");
 249         printf("Number of executions: %d\n", num_executions);
 250         printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
 251
 252         scheduler->print();
 253
 254         print_list(action_trace);
 255         printf("\n");
 256
 257 }
 258
 259 void ModelChecker::print_list(action_list_t *list)
 260 {
 261         action_list_t::iterator it;
 262
 263         printf("---------------------------------------------------------------------\n");
 264         printf("Trace:\n");
 265
 266         for (it = list->begin(); it != list->end(); it++) {
 267                 (*it)->print();
 268         }
 269         printf("---------------------------------------------------------------------\n");
 270 }
 271
 272 int ModelChecker::add_thread(Thread *t)
 273 {
 274         thread_map[id_to_int(t->get_id())] = t;
 275         scheduler->add_thread(t);
 276         return 0;
 277 }
 278
 279 void ModelChecker::remove_thread(Thread *t)
 280 {
 281         scheduler->remove_thread(t);
 282 }
 283
 284 int ModelChecker::switch_to_master(ModelAction *act)
 285 {
 286         Thread *old;
 287
 288         DBG();
 289         old = thread_current();
 290         set_current_action(act);
 291         old->set_state(THREAD_READY);
 292         return Thread::swap(old, get_system_context());
 293 }
 294
 295 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 296 {
 297         Thread *t = thread_current();
 298         ModelAction *act = this;
 299
 300         act->type = type;
 301         act->order = order;
 302         act->location = loc;
 303         act->tid = t->get_id();
 304         act->value = value;
 305         act->seq_number = model->get_next_seq_num();
 306 }
 307
 308 bool ModelAction::is_read()
 309 {
 310         return type == ATOMIC_READ;
 311 }
 312
 313 bool ModelAction::is_write()
 314 {
 315         return type == ATOMIC_WRITE;
 316 }
 317
 318 bool ModelAction::is_acquire()
 319 {
 320         switch (order) {
 321         case memory_order_acquire:
 322         case memory_order_acq_rel:
 323         case memory_order_seq_cst:
 324                 return true;
 325         default:
 326                 return false;
 327         }
 328 }
 329
 330 bool ModelAction::is_release()
 331 {
 332         switch (order) {
 333         case memory_order_release:
 334         case memory_order_acq_rel:
 335         case memory_order_seq_cst:
 336                 return true;
 337         default:
 338                 return false;
 339         }
 340 }
 341
 342 bool ModelAction::same_var(ModelAction *act)
 343 {
 344         return location == act->location;
 345 }
 346
 347 bool ModelAction::same_thread(ModelAction *act)
 348 {
 349         return tid == act->tid;
 350 }
 351
 352 bool ModelAction::is_dependent(ModelAction *act)
 353 {
 354         if (!is_read() && !is_write())
 355                 return false;
 356         if (!act->is_read() && !act->is_write())
 357                 return false;
 358         if (same_var(act) && !same_thread(act) &&
 359                         (is_write() || act->is_write()))
 360                 return true;
 361         return false;
 362 }
 363
 364 void ModelAction::print(void)
 365 {
 366         const char *type_str;
 367         switch (this->type) {
 368         case THREAD_CREATE:
 369                 type_str = "thread create";
 370                 break;
 371         case THREAD_YIELD:
 372                 type_str = "thread yield";
 373                 break;
 374         case THREAD_JOIN:
 375                 type_str = "thread join";
 376                 break;
 377         case ATOMIC_READ:
 378                 type_str = "atomic read";
 379                 break;
 380         case ATOMIC_WRITE:
 381                 type_str = "atomic write";
 382                 break;
 383         default:
 384                 type_str = "unknown type";
 385         }
 386
 387         printf("(%4d) Thread: %d\tAction: %s\tMO: %d\tLoc: %14p\tValue: %d\n",
 388                         seq_number, id_to_int(tid), type_str, order, location, value);
 389 }