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