model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "action.h"
   5 #include "nodestack.h"
   6 #include "schedule.h"
   7 #include "snapshot-interface.h"
   8 #include "common.h"
   9
  10 #define INITIAL_THREAD_ID       0
  11
  12 ModelChecker *model;
  13
  14 ModelChecker::ModelChecker()
  15         :
  16         /* Initialize default scheduler */
  17         scheduler(new Scheduler()),
  18         /* First thread created will have id INITIAL_THREAD_ID */
  19         next_thread_id(INITIAL_THREAD_ID),
  20         used_sequence_numbers(0),
  21
  22         num_executions(0),
  23         current_action(NULL),
  24         diverge(NULL),
  25         nextThread(THREAD_ID_T_NONE),
  26         action_trace(new action_list_t()),
  27         thread_map(new std::map<int, class Thread *>),
  28         node_stack(new NodeStack()),
  29         next_backtrack(NULL)
  30 {
  31 }
  32
  33 ModelChecker::~ModelChecker()
  34 {
  35         std::map<int, class Thread *>::iterator it;
  36         for (it = thread_map->begin(); it != thread_map->end(); it++)
  37                 delete (*it).second;
  38         delete thread_map;
  39
  40         delete action_trace;
  41
  42         delete node_stack;
  43         delete scheduler;
  44 }
  45
  46 void ModelChecker::reset_to_initial_state()
  47 {
  48         DEBUG("+++ Resetting to initial state +++\n");
  49         node_stack->reset_execution();
  50         current_action = NULL;
  51         next_thread_id = INITIAL_THREAD_ID;
  52         used_sequence_numbers = 0;
  53         nextThread = 0;
  54         next_backtrack = NULL;
  55         /* scheduler reset ? */
  56         snapshotObject->backTrackBeforeStep(0);
  57 }
  58
  59 thread_id_t ModelChecker::get_next_id()
  60 {
  61         return next_thread_id++;
  62 }
  63
  64 int ModelChecker::get_next_seq_num()
  65 {
  66         return ++used_sequence_numbers;
  67 }
  68
  69 Thread * ModelChecker::schedule_next_thread()
  70 {
  71         Thread *t;
  72         if (nextThread == THREAD_ID_T_NONE)
  73                 return NULL;
  74         t = (*thread_map)[id_to_int(nextThread)];
  75
  76         ASSERT(t != NULL);
  77
  78         return t;
  79 }
  80
  81 /*
  82  * get_next_replay_thread() - Choose the next thread in the replay sequence
  83  *
  84  * If we've reached the 'diverge' point, then we pick a thread from the
  85  *   backtracking set.
  86  * Otherwise, we simply return the next thread in the sequence.
  87  */
  88 thread_id_t ModelChecker::get_next_replay_thread()
  89 {
  90         ModelAction *next;
  91         thread_id_t tid;
  92
  93         /* Have we completed exploring the preselected path? */
  94         if (diverge == NULL)
  95                 return THREAD_ID_T_NONE;
  96
  97         /* Else, we are trying to replay an execution */
  98         next = node_stack->get_next()->get_action();
  99
 100         if (next == diverge) {
 101                 Node *node = next->get_node();
 102
 103                 /* Reached divergence point */
 104                 DEBUG("*** Divergence point ***\n");
 105                 tid = node->get_next_backtrack();
 106                 diverge = NULL;
 107         } else {
 108                 tid = next->get_tid();
 109         }
 110         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 111         return tid;
 112 }
 113
 114 bool ModelChecker::next_execution()
 115 {
 116         DBG();
 117
 118         num_executions++;
 119         print_summary();
 120         if ((diverge = model->get_next_backtrack()) == NULL)
 121                 return false;
 122
 123         if (DBG_ENABLED()) {
 124                 printf("Next execution will diverge at:\n");
 125                 diverge->print();
 126         }
 127
 128         model->reset_to_initial_state();
 129         return true;
 130 }
 131
 132 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 133 {
 134         action_type type = act->get_type();
 135
 136         switch (type) {
 137                 case THREAD_CREATE:
 138                 case THREAD_YIELD:
 139                 case THREAD_JOIN:
 140                         return NULL;
 141                 case ATOMIC_READ:
 142                 case ATOMIC_WRITE:
 143                 default:
 144                         break;
 145         }
 146         /* linear search: from most recent to oldest */
 147         action_list_t::reverse_iterator rit;
 148         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 149                 ModelAction *prev = *rit;
 150                 if (act->is_dependent(prev))
 151                         return prev;
 152         }
 153         return NULL;
 154 }
 155
 156 void ModelChecker::set_backtracking(ModelAction *act)
 157 {
 158         ModelAction *prev;
 159         Node *node;
 160         Thread *t = get_thread(act->get_tid());
 161
 162         prev = get_last_conflict(act);
 163         if (prev == NULL)
 164                 return;
 165
 166         node = prev->get_node();
 167
 168         while (!node->is_enabled(t))
 169                 t = t->get_parent();
 170
 171         /* Check if this has been explored already */
 172         if (node->has_been_explored(t->get_id()))
 173                 return;
 174
 175         if (!next_backtrack || *prev > *next_backtrack)
 176                 next_backtrack = prev;
 177
 178         /* If this is a new backtracking point, mark the tree */
 179         if (!node->set_backtrack(t->get_id()))
 180                 return;
 181         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 182                         prev->get_tid(), t->get_id());
 183         if (DBG_ENABLED()) {
 184                 prev->print();
 185                 act->print();
 186         }
 187 }
 188
 189 ModelAction * ModelChecker::get_next_backtrack()
 190 {
 191         ModelAction *next = next_backtrack;
 192         next_backtrack = NULL;
 193         return next;
 194 }
 195
 196 void ModelChecker::check_current_action(void)
 197 {
 198         Node *currnode;
 199
 200         ModelAction *curr = this->current_action;
 201         current_action = NULL;
 202         if (!curr) {
 203                 DEBUG("trying to push NULL action...\n");
 204                 return;
 205         }
 206
 207         curr = node_stack->explore_action(curr);
 208         nextThread = get_next_replay_thread();
 209
 210         currnode = curr->get_node();
 211
 212         if (!currnode->backtrack_empty())
 213                 if (!next_backtrack || *curr > *next_backtrack)
 214                         next_backtrack = curr;
 215
 216         set_backtracking(curr);
 217         this->action_trace->push_back(curr);
 218 }
 219
 220 void ModelChecker::print_summary(void)
 221 {
 222         printf("\n");
 223         printf("Number of executions: %d\n", num_executions);
 224         printf("Total nodes created: %d\n", Node::get_total_nodes());
 225
 226         scheduler->print();
 227
 228         print_list(action_trace);
 229         printf("\n");
 230 }
 231
 232 void ModelChecker::print_list(action_list_t *list)
 233 {
 234         action_list_t::iterator it;
 235
 236         printf("---------------------------------------------------------------------\n");
 237         printf("Trace:\n");
 238
 239         for (it = list->begin(); it != list->end(); it++) {
 240                 (*it)->print();
 241         }
 242         printf("---------------------------------------------------------------------\n");
 243 }
 244
 245 int ModelChecker::add_thread(Thread *t)
 246 {
 247         (*thread_map)[id_to_int(t->get_id())] = t;
 248         scheduler->add_thread(t);
 249         return 0;
 250 }
 251
 252 void ModelChecker::remove_thread(Thread *t)
 253 {
 254         scheduler->remove_thread(t);
 255 }
 256
 257 int ModelChecker::switch_to_master(ModelAction *act)
 258 {
 259         Thread *old;
 260
 261         DBG();
 262         old = thread_current();
 263         set_current_action(act);
 264         old->set_state(THREAD_READY);
 265         return Thread::swap(old, get_system_context());
 266 }