model.cc

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