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         /* Initialize default scheduler */
  18         this->scheduler = new Scheduler();
  19
  20         num_executions = 0;
  21         this->current_action = NULL;
  22         this->exploring = NULL;
  23         this->nextThread = THREAD_ID_T_NONE;
  24
  25         rootNode = new TreeNode(NULL);
  26         currentNode = rootNode;
  27         action_trace = new action_list_t();
  28 }
  29
  30 ModelChecker::~ModelChecker()
  31 {
  32         delete action_trace;
  33         delete this->scheduler;
  34         delete rootNode;
  35 }
  36
  37 void ModelChecker::reset_to_initial_state()
  38 {
  39         DEBUG("+++ Resetting to initial state +++\n");
  40         std::map<int, class Thread *>::iterator it;
  41         for (it = thread_map.begin(); it != thread_map.end(); it++)
  42                 delete (*it).second;
  43         thread_map.clear();
  44         action_trace = new action_list_t();
  45         currentNode = rootNode;
  46         current_action = NULL;
  47         used_thread_id = INITIAL_THREAD_ID;
  48         /* scheduler reset ? */
  49 }
  50
  51 thread_id_t ModelChecker::get_next_id()
  52 {
  53         return ++used_thread_id;
  54 }
  55
  56 Thread * ModelChecker::schedule_next_thread()
  57 {
  58         Thread *t;
  59         if (nextThread == THREAD_ID_T_NONE)
  60                 return NULL;
  61         t = thread_map[id_to_int(nextThread)];
  62         if (t == NULL)
  63                 DEBUG("*** error: thread not in thread_map: id = %d\n", nextThread);
  64         return t;
  65 }
  66
  67 /*
  68  * get_next_replay_thread() - Choose the next thread in the replay sequence
  69  *
  70  * If we've reached the 'diverge' point, then we pick a thread from the
  71  *   backtracking set.
  72  * Otherwise, we simply return the next thread in the sequence.
  73  */
  74 thread_id_t ModelChecker::get_next_replay_thread()
  75 {
  76         ModelAction *next;
  77         thread_id_t tid;
  78
  79         next = exploring->get_state();
  80
  81         if (next == exploring->get_diverge()) {
  82                 TreeNode *node = next->get_node();
  83
  84                 /* Reached divergence point; discard our current 'exploring' */
  85                 DEBUG("*** Discard 'Backtrack' object ***\n");
  86                 tid = node->getNextBacktrack();
  87                 delete exploring;
  88                 exploring = NULL;
  89         } else {
  90                 tid = next->get_tid();
  91         }
  92         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
  93         return tid;
  94 }
  95
  96 thread_id_t ModelChecker::advance_backtracking_state()
  97 {
  98         /* Have we completed exploring the preselected path? */
  99         if (exploring == NULL)
 100                 return THREAD_ID_T_NONE;
 101
 102         /* Else, we are trying to replay an execution */
 103         exploring->advance_state();
 104         if (exploring->get_state() == NULL)
 105                 DEBUG("*** error: reached end of backtrack trace\n");
 106
 107         return get_next_replay_thread();
 108 }
 109
 110 bool ModelChecker::next_execution()
 111 {
 112         num_executions++;
 113         print_summary();
 114         if ((exploring = model->get_next_backtrack()) == NULL)
 115                 return false;
 116         model->reset_to_initial_state();
 117         nextThread = get_next_replay_thread();
 118         return true;
 119 }
 120
 121 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 122 {
 123         action_type type = act->get_type();
 124
 125         switch (type) {
 126                 case THREAD_CREATE:
 127                 case THREAD_YIELD:
 128                 case THREAD_JOIN:
 129                         return NULL;
 130                 case ATOMIC_READ:
 131                 case ATOMIC_WRITE:
 132                 default:
 133                         break;
 134         }
 135         /* linear search: from most recent to oldest */
 136         action_list_t::reverse_iterator rit;
 137         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 138                 ModelAction *prev = *rit;
 139                 if (act->is_dependent(prev))
 140                         return prev;
 141         }
 142         return NULL;
 143 }
 144
 145 void ModelChecker::set_backtracking(ModelAction *act)
 146 {
 147         ModelAction *prev;
 148         TreeNode *node;
 149
 150         prev = get_last_conflict(act);
 151         if (prev == NULL)
 152                 return;
 153
 154         node = prev->get_node();
 155
 156         /* Check if this has been explored already */
 157         if (node->hasBeenExplored(act->get_tid()))
 158                 return;
 159         /* If this is a new backtracking point, mark the tree */
 160         if (node->setBacktrack(act->get_tid()) != 0)
 161                 return;
 162
 163         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 164                         prev->get_tid(), act->get_tid());
 165         if (DBG_ENABLED()) {
 166                 prev->print();
 167                 act->print();
 168         }
 169
 170         Backtrack *back = new Backtrack(prev, action_trace);
 171         backtrack_list.push_back(back);
 172 }
 173
 174 Backtrack * ModelChecker::get_next_backtrack()
 175 {
 176         Backtrack *next;
 177         if (backtrack_list.empty())
 178                 return NULL;
 179         next = backtrack_list.back();
 180         backtrack_list.pop_back();
 181         return next;
 182 }
 183
 184 void ModelChecker::check_current_action(void)
 185 {
 186         ModelAction *next = this->current_action;
 187
 188         if (!next) {
 189                 DEBUG("trying to push NULL action...\n");
 190                 return;
 191         }
 192         current_action = NULL;
 193         nextThread = advance_backtracking_state();
 194         next->set_node(currentNode);
 195         set_backtracking(next);
 196         currentNode = currentNode->exploreChild(next->get_tid());
 197         this->action_trace->push_back(next);
 198 }
 199
 200 void ModelChecker::print_summary(void)
 201 {
 202         action_list_t::iterator it;
 203
 204         printf("\n");
 205         printf("---------------------------------------------------------------------\n");
 206         printf("Number of executions: %d\n", num_executions);
 207         printf("Total nodes created: %d\n\n", TreeNode::getTotalNodes());
 208
 209         scheduler->print();
 210
 211         printf("Trace:\n\n");
 212
 213         for (it = action_trace->begin(); it != action_trace->end(); it++) {
 214                 DBG();
 215                 (*it)->print();
 216         }
 217         printf("---------------------------------------------------------------------\n");
 218 }
 219
 220 int ModelChecker::add_thread(Thread *t)
 221 {
 222         thread_map[id_to_int(t->get_id())] = t;
 223         scheduler->add_thread(t);
 224         return 0;
 225 }
 226
 227 void ModelChecker::remove_thread(Thread *t)
 228 {
 229         scheduler->remove_thread(t);
 230 }
 231
 232 int ModelChecker::switch_to_master(ModelAction *act)
 233 {
 234         Thread *old;
 235
 236         DBG();
 237         old = thread_current();
 238         set_current_action(act);
 239         old->set_state(THREAD_READY);
 240         return Thread::swap(old, get_system_context());
 241 }
 242
 243 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 244 {
 245         Thread *t = thread_current();
 246         ModelAction *act = this;
 247
 248         act->type = type;
 249         act->order = order;
 250         act->location = loc;
 251         act->tid = t->get_id();
 252         act->value = value;
 253 }
 254
 255 bool ModelAction::is_read()
 256 {
 257         return type == ATOMIC_READ;
 258 }
 259
 260 bool ModelAction::is_write()
 261 {
 262         return type == ATOMIC_WRITE;
 263 }
 264
 265 bool ModelAction::is_acquire()
 266 {
 267         switch (order) {
 268         case memory_order_acquire:
 269         case memory_order_acq_rel:
 270         case memory_order_seq_cst:
 271                 return true;
 272         default:
 273                 return false;
 274         }
 275 }
 276
 277 bool ModelAction::is_release()
 278 {
 279         switch (order) {
 280         case memory_order_release:
 281         case memory_order_acq_rel:
 282         case memory_order_seq_cst:
 283                 return true;
 284         default:
 285                 return false;
 286         }
 287 }
 288
 289 bool ModelAction::same_var(ModelAction *act)
 290 {
 291         return location == act->location;
 292 }
 293
 294 bool ModelAction::same_thread(ModelAction *act)
 295 {
 296         return tid == act->tid;
 297 }
 298
 299 bool ModelAction::is_dependent(ModelAction *act)
 300 {
 301         if (!is_read() && !is_write())
 302                 return false;
 303         if (!act->is_read() && !act->is_write())
 304                 return false;
 305         if (same_var(act) && !same_thread(act) &&
 306                         (is_write() || act->is_write()))
 307                 return true;
 308         return false;
 309 }
 310
 311 void ModelAction::print(void)
 312 {
 313         const char *type_str;
 314         switch (this->type) {
 315         case THREAD_CREATE:
 316                 type_str = "thread create";
 317                 break;
 318         case THREAD_YIELD:
 319                 type_str = "thread yield";
 320                 break;
 321         case THREAD_JOIN:
 322                 type_str = "thread join";
 323                 break;
 324         case ATOMIC_READ:
 325                 type_str = "atomic read";
 326                 break;
 327         case ATOMIC_WRITE:
 328                 type_str = "atomic write";
 329                 break;
 330         default:
 331                 type_str = "unknown type";
 332         }
 333
 334         printf("Thread: %d\tAction: %s\tMO: %d\tLoc: %#014zx\tValue: %d\n", id_to_int(tid), type_str, order, (size_t)location, value);
 335 }