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 Thread * ModelChecker::schedule_next_thread()
  54 {
  55         Thread *t;
  56         if (nextThread == THREAD_ID_T_NONE)
  57                 return NULL;
  58         t = thread_map[nextThread];
  59         if (t == NULL)
  60                 DEBUG("*** error: thread not in thread_map: id = %d\n", nextThread);
  61         return t;
  62 }
  63
  64 /*
  65  * get_next_replay_thread() - Choose the next thread in the replay sequence
  66  *
  67  * If we've reached the 'diverge' point, then we pick a thread from the
  68  *   backtracking set.
  69  * Otherwise, we simply return the next thread in the sequence.
  70  */
  71 thread_id_t ModelChecker::get_next_replay_thread()
  72 {
  73         ModelAction *next;
  74         thread_id_t tid;
  75
  76         next = exploring->get_state();
  77
  78         if (next == exploring->get_diverge()) {
  79                 TreeNode *node = next->get_node();
  80
  81                 /* Reached divergence point; discard our current 'exploring' */
  82                 DEBUG("*** Discard 'Backtrack' object ***\n");
  83                 tid = node->getNextBacktrack();
  84                 delete exploring;
  85                 exploring = NULL;
  86         } else {
  87                 tid = next->get_tid();
  88         }
  89         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
  90         return tid;
  91 }
  92
  93 thread_id_t ModelChecker::advance_backtracking_state()
  94 {
  95         /* Have we completed exploring the preselected path? */
  96         if (exploring == NULL)
  97                 return THREAD_ID_T_NONE;
  98
  99         /* Else, we are trying to replay an execution */
 100         exploring->advance_state();
 101         if (exploring->get_state() == NULL)
 102                 DEBUG("*** error: reached end of backtrack trace\n");
 103
 104         return get_next_replay_thread();
 105 }
 106
 107 bool ModelChecker::next_execution()
 108 {
 109         num_executions++;
 110         print_summary();
 111         if ((exploring = model->get_next_backtrack()) == NULL)
 112                 return false;
 113         model->reset_to_initial_state();
 114         nextThread = get_next_replay_thread();
 115         return true;
 116 }
 117
 118 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 119 {
 120         void *loc = act->get_location();
 121         action_type type = act->get_type();
 122         thread_id_t id = act->get_tid();
 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 (prev->get_location() != loc)
 139                         continue;
 140                 if (type == ATOMIC_READ && prev->get_type() != ATOMIC_WRITE)
 141                         continue;
 142                 /* Conflict from the same thread is not really a conflict */
 143                 if (id == prev->get_tid())
 144                         continue;
 145                 return prev;
 146         }
 147         return NULL;
 148 }
 149
 150 void ModelChecker::set_backtracking(ModelAction *act)
 151 {
 152         ModelAction *prev;
 153         TreeNode *node;
 154
 155         prev = get_last_conflict(act);
 156         if (prev == NULL)
 157                 return;
 158
 159         node = prev->get_node();
 160
 161         /* Check if this has been explored already */
 162         if (node->hasBeenExplored(act->get_tid()))
 163                 return;
 164         /* If this is a new backtracking point, mark the tree */
 165         if (node->setBacktrack(act->get_tid()) != 0)
 166                 return;
 167
 168         printf("Setting backtrack: conflict = %d, instead tid = %d\n",
 169                         prev->get_tid(), act->get_tid());
 170         prev->print();
 171         act->print();
 172
 173         Backtrack *back = new Backtrack(prev, action_trace);
 174         backtrack_list.push_back(back);
 175 }
 176
 177 Backtrack * ModelChecker::get_next_backtrack()
 178 {
 179         Backtrack *next;
 180         if (backtrack_list.empty())
 181                 return NULL;
 182         next = backtrack_list.back();
 183         backtrack_list.pop_back();
 184         return next;
 185 }
 186
 187 void ModelChecker::check_current_action(void)
 188 {
 189         ModelAction *next = this->current_action;
 190
 191         if (!next) {
 192                 DEBUG("trying to push NULL action...\n");
 193                 return;
 194         }
 195         current_action = NULL;
 196         nextThread = advance_backtracking_state();
 197         next->set_node(currentNode);
 198         set_backtracking(next);
 199         currentNode = currentNode->exploreChild(next->get_tid());
 200         this->action_trace->push_back(next);
 201 }
 202
 203 void ModelChecker::print_summary(void)
 204 {
 205         action_list_t::iterator it;
 206
 207         printf("\n");
 208         printf("---------------------------------------------------------------------\n");
 209         printf("Number of executions: %d\n", num_executions);
 210         printf("Total nodes created: %d\n\n", TreeNode::getTotalNodes());
 211
 212         scheduler->print();
 213
 214         printf("Trace:\n\n");
 215
 216         for (it = action_trace->begin(); it != action_trace->end(); it++) {
 217                 DBG();
 218                 (*it)->print();
 219         }
 220         printf("---------------------------------------------------------------------\n");
 221 }
 222
 223 int ModelChecker::add_thread(Thread *t)
 224 {
 225         thread_map[t->get_id()] = t;
 226         scheduler->add_thread(t);
 227         return 0;
 228 }
 229
 230 void ModelChecker::remove_thread(Thread *t)
 231 {
 232         scheduler->remove_thread(t);
 233 }
 234
 235 int ModelChecker::switch_to_master(ModelAction *act)
 236 {
 237         Thread *old;
 238
 239         DBG();
 240         old = thread_current();
 241         set_current_action(act);
 242         old->set_state(THREAD_READY);
 243         return Thread::swap(old, get_system_context());
 244 }
 245
 246 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 247 {
 248         Thread *t = thread_current();
 249         ModelAction *act = this;
 250
 251         act->type = type;
 252         act->order = order;
 253         act->location = loc;
 254         act->tid = t->get_id();
 255         act->value = value;
 256 }
 257
 258 void ModelAction::print(void)
 259 {
 260         const char *type_str;
 261         switch (this->type) {
 262         case THREAD_CREATE:
 263                 type_str = "thread create";
 264                 break;
 265         case THREAD_YIELD:
 266                 type_str = "thread yield";
 267                 break;
 268         case THREAD_JOIN:
 269                 type_str = "thread join";
 270                 break;
 271         case ATOMIC_READ:
 272                 type_str = "atomic read";
 273                 break;
 274         case ATOMIC_WRITE:
 275                 type_str = "atomic write";
 276                 break;
 277         default:
 278                 type_str = "unknown type";
 279         }
 280
 281         printf("Thread: %d\tAction: %s\tMO: %d\tLoc: %#014zx\tValue: %d\n", tid, type_str, order, (size_t)location, value);
 282 }