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 "common.h"
   8
   9 #define INITIAL_THREAD_ID       0
  10
  11 class Backtrack {
  12 public:
  13         Backtrack(ModelAction *d, action_list_t *t) {
  14                 diverge = d;
  15                 actionTrace = t;
  16                 iter = actionTrace->begin();
  17         }
  18         ModelAction * get_diverge() { return diverge; }
  19         action_list_t * get_trace() { return actionTrace; }
  20         void advance_state() { iter++; }
  21         ModelAction * get_state() {
  22                 return iter == actionTrace->end() ? NULL : *iter;
  23         }
  24 private:
  25         ModelAction *diverge;
  26         action_list_t *actionTrace;
  27         /* points to position in actionTrace as we replay */
  28         action_list_t::iterator iter;
  29 };
  30
  31 ModelChecker *model;
  32
  33 void free_action_list(action_list_t *list)
  34 {
  35         action_list_t::iterator it;
  36         for (it = list->begin(); it != list->end(); it++)
  37                 delete (*it);
  38         delete list;
  39 }
  40
  41 ModelChecker::ModelChecker()
  42         :
  43         /* Initialize default scheduler */
  44         scheduler(new Scheduler()),
  45         /* First thread created will have id INITIAL_THREAD_ID */
  46         next_thread_id(INITIAL_THREAD_ID),
  47         used_sequence_numbers(0),
  48
  49         num_executions(0),
  50         current_action(NULL),
  51         diverge(NULL),
  52         nextThread(THREAD_ID_T_NONE),
  53         action_trace(new action_list_t()),
  54         node_stack(new NodeStack()),
  55         next_backtrack(NULL)
  56 {
  57 }
  58
  59 ModelChecker::~ModelChecker()
  60 {
  61         std::map<int, class Thread *>::iterator it;
  62         for (it = thread_map.begin(); it != thread_map.end(); it++)
  63                 delete (*it).second;
  64         thread_map.clear();
  65
  66         delete action_trace;
  67
  68         delete node_stack;
  69         delete scheduler;
  70 }
  71
  72 void ModelChecker::reset_to_initial_state()
  73 {
  74         DEBUG("+++ Resetting to initial state +++\n");
  75         std::map<int, class Thread *>::iterator it;
  76         for (it = thread_map.begin(); it != thread_map.end(); it++)
  77                 delete (*it).second;
  78         thread_map.clear();
  79         delete action_trace;
  80         action_trace = new action_list_t();
  81         node_stack->reset_execution();
  82         current_action = NULL;
  83         next_thread_id = INITIAL_THREAD_ID;
  84         used_sequence_numbers = 0;
  85         nextThread = 0;
  86         next_backtrack = NULL;
  87         /* scheduler reset ? */
  88 }
  89
  90 thread_id_t ModelChecker::get_next_id()
  91 {
  92         return next_thread_id++;
  93 }
  94
  95 int ModelChecker::get_next_seq_num()
  96 {
  97         return ++used_sequence_numbers;
  98 }
  99
 100 Thread * ModelChecker::schedule_next_thread()
 101 {
 102         Thread *t;
 103         if (nextThread == THREAD_ID_T_NONE)
 104                 return NULL;
 105         t = thread_map[id_to_int(nextThread)];
 106
 107         ASSERT(t != NULL);
 108
 109         return t;
 110 }
 111
 112 /*
 113  * get_next_replay_thread() - Choose the next thread in the replay sequence
 114  *
 115  * If we've reached the 'diverge' point, then we pick a thread from the
 116  *   backtracking set.
 117  * Otherwise, we simply return the next thread in the sequence.
 118  */
 119 thread_id_t ModelChecker::get_next_replay_thread()
 120 {
 121         ModelAction *next;
 122         thread_id_t tid;
 123
 124         /* Have we completed exploring the preselected path? */
 125         if (diverge == NULL)
 126                 return THREAD_ID_T_NONE;
 127
 128         /* Else, we are trying to replay an execution */
 129         next = node_stack->get_next()->get_action();
 130
 131         if (next == diverge) {
 132                 Node *node = next->get_node();
 133
 134                 /* Reached divergence point */
 135                 DEBUG("*** Divergence point ***\n");
 136                 tid = node->get_next_backtrack();
 137                 diverge = NULL;
 138         } else {
 139                 tid = next->get_tid();
 140         }
 141         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 142         return tid;
 143 }
 144
 145 bool ModelChecker::next_execution()
 146 {
 147         DBG();
 148
 149         num_executions++;
 150         print_summary();
 151         if ((diverge = model->get_next_backtrack()) == NULL)
 152                 return false;
 153
 154         if (DBG_ENABLED()) {
 155                 printf("Next execution will diverge at:\n");
 156                 diverge->print();
 157         }
 158
 159         model->reset_to_initial_state();
 160         return true;
 161 }
 162
 163 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 164 {
 165         action_type type = act->get_type();
 166
 167         switch (type) {
 168                 case THREAD_CREATE:
 169                 case THREAD_YIELD:
 170                 case THREAD_JOIN:
 171                         return NULL;
 172                 case ATOMIC_READ:
 173                 case ATOMIC_WRITE:
 174                 default:
 175                         break;
 176         }
 177         /* linear search: from most recent to oldest */
 178         action_list_t::reverse_iterator rit;
 179         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 180                 ModelAction *prev = *rit;
 181                 if (act->is_dependent(prev))
 182                         return prev;
 183         }
 184         return NULL;
 185 }
 186
 187 void ModelChecker::set_backtracking(ModelAction *act)
 188 {
 189         ModelAction *prev;
 190         Node *node;
 191         Thread *t = get_thread(act->get_tid());
 192
 193         prev = get_last_conflict(act);
 194         if (prev == NULL)
 195                 return;
 196
 197         node = prev->get_node();
 198
 199         while (!node->is_enabled(t))
 200                 t = t->get_parent();
 201
 202         /* Check if this has been explored already */
 203         if (node->has_been_explored(t->get_id()))
 204                 return;
 205
 206         if (!next_backtrack || *prev > *next_backtrack)
 207                 next_backtrack = prev;
 208
 209         /* If this is a new backtracking point, mark the tree */
 210         if (!node->set_backtrack(t->get_id()))
 211                 return;
 212         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 213                         prev->get_tid(), t->get_id());
 214         if (DBG_ENABLED()) {
 215                 prev->print();
 216                 act->print();
 217         }
 218 }
 219
 220 ModelAction * ModelChecker::get_next_backtrack()
 221 {
 222         ModelAction *next = next_backtrack;
 223         next_backtrack = NULL;
 224         return next;
 225 }
 226
 227 void ModelChecker::check_current_action(void)
 228 {
 229         Node *currnode;
 230
 231         ModelAction *curr = this->current_action;
 232         current_action = NULL;
 233         if (!curr) {
 234                 DEBUG("trying to push NULL action...\n");
 235                 return;
 236         }
 237
 238         curr = node_stack->explore_action(curr);
 239         nextThread = get_next_replay_thread();
 240
 241         currnode = curr->get_node();
 242
 243         if (!currnode->backtrack_empty())
 244                 if (!next_backtrack || *curr > *next_backtrack)
 245                         next_backtrack = curr;
 246
 247         set_backtracking(curr);
 248         this->action_trace->push_back(curr);
 249 }
 250
 251 void ModelChecker::print_summary(void)
 252 {
 253         printf("\n");
 254         printf("Number of executions: %d\n", num_executions);
 255         printf("Total nodes created: %d\n", Node::get_total_nodes());
 256
 257         scheduler->print();
 258
 259         print_list(action_trace);
 260         printf("\n");
 261 }
 262
 263 void ModelChecker::print_list(action_list_t *list)
 264 {
 265         action_list_t::iterator it;
 266
 267         printf("---------------------------------------------------------------------\n");
 268         printf("Trace:\n");
 269
 270         for (it = list->begin(); it != list->end(); it++) {
 271                 (*it)->print();
 272         }
 273         printf("---------------------------------------------------------------------\n");
 274 }
 275
 276 int ModelChecker::add_thread(Thread *t)
 277 {
 278         thread_map[id_to_int(t->get_id())] = t;
 279         scheduler->add_thread(t);
 280         return 0;
 281 }
 282
 283 void ModelChecker::remove_thread(Thread *t)
 284 {
 285         scheduler->remove_thread(t);
 286 }
 287
 288 int ModelChecker::switch_to_master(ModelAction *act)
 289 {
 290         Thread *old;
 291
 292         DBG();
 293         old = thread_current();
 294         set_current_action(act);
 295         old->set_state(THREAD_READY);
 296         return Thread::swap(old, get_system_context());
 297 }