model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "schedule.h"
   5 #include "common.h"
   6
   7 #define INITIAL_THREAD_ID       0
   8
   9 ModelChecker *model;
  10
  11 ModelChecker::ModelChecker()
  12 {
  13         /* First thread created will have id (INITIAL_THREAD_ID + 1) */
  14         this->used_thread_id = INITIAL_THREAD_ID;
  15         /* Initialize default scheduler */
  16         this->scheduler = new Scheduler();
  17
  18         num_executions = 0;
  19         this->current_action = NULL;
  20         this->exploring = NULL;
  21         this->nextThread = THREAD_ID_T_NONE;
  22
  23         rootNode = new TreeNode(NULL);
  24         currentNode = rootNode;
  25         action_trace = new action_list_t();
  26 }
  27
  28 ModelChecker::~ModelChecker()
  29 {
  30         delete action_trace;
  31         delete this->scheduler;
  32         delete rootNode;
  33 }
  34
  35 void ModelChecker::reset_to_initial_state()
  36 {
  37         DEBUG("+++ Resetting to initial state +++\n");
  38         std::map<thread_id_t, class Thread *>::iterator it;
  39         for (it = thread_map.begin(); it != thread_map.end(); it++) {
  40                 delete (*it).second;
  41         }
  42         thread_map.clear();
  43         action_trace = new action_list_t();
  44         currentNode = rootNode;
  45         current_action = NULL;
  46         used_thread_id = INITIAL_THREAD_ID;
  47         /* scheduler reset ? */
  48 }
  49
  50 int ModelChecker::get_next_id()
  51 {
  52         return ++used_thread_id;
  53 }
  54
  55 Thread * ModelChecker::schedule_next_thread()
  56 {
  57         Thread *t;
  58         if (nextThread == THREAD_ID_T_NONE)
  59                 return NULL;
  60         t = thread_map[nextThread];
  61         if (t == NULL)
  62                 DEBUG("*** error: thread not in thread_map: id = %d\n", nextThread);
  63         return t;
  64 }
  65
  66 /*
  67  * get_next_replay_thread() - Choose the next thread in the replay sequence
  68  *
  69  * If we've reached the 'diverge' point, then we pick a thread from the
  70  *   backtracking set.
  71  * Otherwise, we simply return the next thread in the sequence.
  72  */
  73 thread_id_t ModelChecker::get_next_replay_thread()
  74 {
  75         ModelAction *next;
  76         thread_id_t tid;
  77
  78         next = exploring->get_state();
  79
  80         if (next == exploring->get_diverge()) {
  81                 TreeNode *node = next->get_node();
  82
  83                 /* Reached divergence point; discard our current 'exploring' */
  84                 DEBUG("*** Discard 'Backtrack' object ***\n");
  85                 tid = node->getNextBacktrack();
  86                 delete exploring;
  87                 exploring = NULL;
  88         } else {
  89                 tid = next->get_tid();
  90         }
  91         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
  92         return tid;
  93 }
  94
  95 thread_id_t ModelChecker::advance_backtracking_state()
  96 {
  97         /* Have we completed exploring the preselected path? */
  98         if (exploring == NULL)
  99                 return THREAD_ID_T_NONE;
 100
 101         /* Else, we are trying to replay an execution */
 102         exploring->advance_state();
 103         if (exploring->get_state() == NULL)
 104                 DEBUG("*** error: reached end of backtrack trace\n");
 105
 106         return get_next_replay_thread();
 107 }
 108
 109 bool ModelChecker::next_execution()
 110 {
 111         num_executions++;
 112         print_summary();
 113         if ((exploring = model->get_next_backtrack()) == NULL)
 114                 return false;
 115         model->reset_to_initial_state();
 116         nextThread = get_next_replay_thread();
 117         return true;
 118 }
 119
 120 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 121 {
 122         action_type type = act->get_type();
 123
 124         switch (type) {
 125                 case THREAD_CREATE:
 126                 case THREAD_YIELD:
 127                 case THREAD_JOIN:
 128                         return NULL;
 129                 case ATOMIC_READ:
 130                 case ATOMIC_WRITE:
 131                 default:
 132                         break;
 133         }
 134         /* linear search: from most recent to oldest */
 135         action_list_t::reverse_iterator rit;
 136         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 137                 ModelAction *prev = *rit;
 138                 if (act->is_dependent(prev))
 139                         return prev;
 140         }
 141         return NULL;
 142 }
 143
 144 void ModelChecker::set_backtracking(ModelAction *act)
 145 {
 146         ModelAction *prev;
 147         TreeNode *node;
 148
 149         prev = get_last_conflict(act);
 150         if (prev == NULL)
 151                 return;
 152
 153         node = prev->get_node();
 154
 155         /* Check if this has been explored already */
 156         if (node->hasBeenExplored(act->get_tid()))
 157                 return;
 158         /* If this is a new backtracking point, mark the tree */
 159         if (node->setBacktrack(act->get_tid()) != 0)
 160                 return;
 161
 162         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 163                         prev->get_tid(), act->get_tid());
 164         if (DBG_ENABLED()) {
 165                 prev->print();
 166                 act->print();
 167         }
 168
 169         Backtrack *back = new Backtrack(prev, action_trace);
 170         backtrack_list.push_back(back);
 171 }
 172
 173 Backtrack * ModelChecker::get_next_backtrack()
 174 {
 175         Backtrack *next;
 176         if (backtrack_list.empty())
 177                 return NULL;
 178         next = backtrack_list.back();
 179         backtrack_list.pop_back();
 180         return next;
 181 }
 182
 183 void ModelChecker::check_current_action(void)
 184 {
 185         ModelAction *next = this->current_action;
 186
 187         if (!next) {
 188                 DEBUG("trying to push NULL action...\n");
 189                 return;
 190         }
 191         current_action = NULL;
 192         nextThread = advance_backtracking_state();
 193         next->set_node(currentNode);
 194         set_backtracking(next);
 195         currentNode = currentNode->exploreChild(next->get_tid());
 196         this->action_trace->push_back(next);
 197 }
 198
 199 void ModelChecker::print_summary(void)
 200 {
 201         action_list_t::iterator it;
 202
 203         printf("\n");
 204         printf("---------------------------------------------------------------------\n");
 205         printf("Number of executions: %d\n", num_executions);
 206         printf("Total nodes created: %d\n\n", TreeNode::getTotalNodes());
 207
 208         scheduler->print();
 209
 210         printf("Trace:\n\n");
 211
 212         for (it = action_trace->begin(); it != action_trace->end(); it++) {
 213                 DBG();
 214                 (*it)->print();
 215         }
 216         printf("---------------------------------------------------------------------\n");
 217 }
 218
 219 int ModelChecker::add_thread(Thread *t)
 220 {
 221         thread_map[t->get_id()] = t;
 222         scheduler->add_thread(t);
 223         return 0;
 224 }
 225
 226 void ModelChecker::remove_thread(Thread *t)
 227 {
 228         scheduler->remove_thread(t);
 229 }
 230
 231 int ModelChecker::switch_to_master(ModelAction *act)
 232 {
 233         Thread *old;
 234
 235         DBG();
 236         old = thread_current();
 237         set_current_action(act);
 238         old->set_state(THREAD_READY);
 239         return Thread::swap(old, get_system_context());
 240 }
 241
 242 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 243 {
 244         Thread *t = thread_current();
 245         ModelAction *act = this;
 246
 247         act->type = type;
 248         act->order = order;
 249         act->location = loc;
 250         act->tid = t->get_id();
 251         act->value = value;
 252 }
 253
 254 bool ModelAction::is_read()
 255 {
 256         return type == ATOMIC_READ;
 257 }
 258
 259 bool ModelAction::is_write()
 260 {
 261         return type == ATOMIC_WRITE;
 262 }
 263
 264 bool ModelAction::is_acquire()
 265 {
 266         switch (order) {
 267         case memory_order_acquire:
 268         case memory_order_acq_rel:
 269         case memory_order_seq_cst:
 270                 return true;
 271         default:
 272                 return false;
 273         }
 274 }
 275
 276 bool ModelAction::is_release()
 277 {
 278         switch (order) {
 279         case memory_order_release:
 280         case memory_order_acq_rel:
 281         case memory_order_seq_cst:
 282                 return true;
 283         default:
 284                 return false;
 285         }
 286 }
 287
 288 bool ModelAction::same_var(ModelAction *act)
 289 {
 290         return location == act->location;
 291 }
 292
 293 bool ModelAction::same_thread(ModelAction *act)
 294 {
 295         return tid == act->tid;
 296 }
 297
 298 bool ModelAction::is_dependent(ModelAction *act)
 299 {
 300         if (!is_read() && !is_write())
 301                 return false;
 302         if (!act->is_read() && !act->is_write())
 303                 return false;
 304         if (same_var(act) && !same_thread(act) &&
 305                         (is_write() || act->is_write()))
 306                 return true;
 307         return false;
 308 }
 309
 310 void ModelAction::print(void)
 311 {
 312         const char *type_str;
 313         switch (this->type) {
 314         case THREAD_CREATE:
 315                 type_str = "thread create";
 316                 break;
 317         case THREAD_YIELD:
 318                 type_str = "thread yield";
 319                 break;
 320         case THREAD_JOIN:
 321                 type_str = "thread join";
 322                 break;
 323         case ATOMIC_READ:
 324                 type_str = "atomic read";
 325                 break;
 326         case ATOMIC_WRITE:
 327                 type_str = "atomic write";
 328                 break;
 329         default:
 330                 type_str = "unknown type";
 331         }
 332
 333         printf("Thread: %d\tAction: %s\tMO: %d\tLoc: %#014zx\tValue: %d\n", tid, type_str, order, (size_t)location, value);
 334 }