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 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         /* First thread created will have id INITIAL_THREAD_ID */
  44         this->next_thread_id = INITIAL_THREAD_ID;
  45         used_sequence_numbers = 0;
  46         /* Initialize default scheduler */
  47         this->scheduler = new Scheduler();
  48
  49         num_executions = 0;
  50         this->current_action = NULL;
  51         this->exploring = NULL;
  52         this->nextThread = THREAD_ID_T_NONE;
  53
  54         rootNode = new TreeNode();
  55         currentNode = rootNode;
  56         action_trace = new action_list_t();
  57 }
  58
  59 ModelChecker::~ModelChecker()
  60 {
  61         std::map<int, class Thread *, std::less< int >, MyAlloc< std::pair< 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         free_action_list(action_trace);
  67
  68         delete this->scheduler;
  69         delete rootNode;
  70 }
  71
  72 void ModelChecker::reset_to_initial_state()
  73 {
  74         DEBUG("+++ Resetting to initial state +++\n");
  75         std::map<int, class Thread *, std::less< int >, MyAlloc< std::pair< 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         action_trace = new action_list_t();
  80         currentNode = rootNode;
  81         current_action = NULL;
  82         next_thread_id = INITIAL_THREAD_ID;
  83         used_sequence_numbers = 0;
  84         /* scheduler reset ? */
  85 }
  86
  87 thread_id_t ModelChecker::get_next_id()
  88 {
  89         return next_thread_id++;
  90 }
  91
  92 int ModelChecker::get_next_seq_num()
  93 {
  94         return ++used_sequence_numbers;
  95 }
  96
  97 Thread * ModelChecker::schedule_next_thread()
  98 {
  99         Thread *t;
 100         if (nextThread == THREAD_ID_T_NONE)
 101                 return NULL;
 102         t = thread_map[id_to_int(nextThread)];
 103
 104         ASSERT(t != NULL);
 105
 106         return t;
 107 }
 108
 109 /*
 110  * get_next_replay_thread() - Choose the next thread in the replay sequence
 111  *
 112  * If we've reached the 'diverge' point, then we pick a thread from the
 113  *   backtracking set.
 114  * Otherwise, we simply return the next thread in the sequence.
 115  */
 116 thread_id_t ModelChecker::get_next_replay_thread()
 117 {
 118         ModelAction *next;
 119         thread_id_t tid;
 120
 121         next = exploring->get_state();
 122
 123         if (next == exploring->get_diverge()) {
 124                 TreeNode *node = next->get_node();
 125
 126                 /* Reached divergence point; discard our current 'exploring' */
 127                 DEBUG("*** Discard 'Backtrack' object ***\n");
 128                 tid = node->getNextBacktrack();
 129                 delete exploring;
 130                 exploring = NULL;
 131         } else {
 132                 tid = next->get_tid();
 133         }
 134         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 135         return tid;
 136 }
 137
 138 thread_id_t ModelChecker::advance_backtracking_state()
 139 {
 140         /* Have we completed exploring the preselected path? */
 141         if (exploring == NULL)
 142                 return THREAD_ID_T_NONE;
 143
 144         /* Else, we are trying to replay an execution */
 145         exploring->advance_state();
 146
 147         ASSERT(exploring->get_state() != NULL);
 148
 149         return get_next_replay_thread();
 150 }
 151
 152 bool ModelChecker::next_execution()
 153 {
 154         DBG();
 155
 156         num_executions++;
 157         print_summary();
 158         if ((exploring = model->get_next_backtrack()) == NULL)
 159                 return false;
 160
 161         if (DBG_ENABLED()) {
 162                 printf("Next execution will diverge at:\n");
 163                 exploring->get_diverge()->print();
 164                 print_list(exploring->get_trace());
 165         }
 166
 167         model->reset_to_initial_state();
 168         nextThread = get_next_replay_thread();
 169         return true;
 170 }
 171
 172 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 173 {
 174         action_type type = act->get_type();
 175
 176         switch (type) {
 177                 case THREAD_CREATE:
 178                 case THREAD_YIELD:
 179                 case THREAD_JOIN:
 180                         return NULL;
 181                 case ATOMIC_READ:
 182                 case ATOMIC_WRITE:
 183                 default:
 184                         break;
 185         }
 186         /* linear search: from most recent to oldest */
 187         action_list_t::reverse_iterator rit;
 188         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 189                 ModelAction *prev = *rit;
 190                 if (act->is_dependent(prev))
 191                         return prev;
 192         }
 193         return NULL;
 194 }
 195
 196 void ModelChecker::set_backtracking(ModelAction *act)
 197 {
 198         ModelAction *prev;
 199         TreeNode *node;
 200         Thread *t = get_thread(act->get_tid());
 201
 202         prev = get_last_conflict(act);
 203         if (prev == NULL)
 204                 return;
 205
 206         node = prev->get_node();
 207
 208         while (t && !node->is_enabled(t))
 209                 t = t->get_parent();
 210
 211         /* Check if this has been explored already */
 212         if (node->hasBeenExplored(t->get_id()))
 213                 return;
 214         /* If this is a new backtracking point, mark the tree */
 215         if (node->setBacktrack(t->get_id()) != 0)
 216                 return;
 217
 218         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 219                         prev->get_tid(), t->get_id());
 220         if (DBG_ENABLED()) {
 221                 prev->print();
 222                 act->print();
 223         }
 224
 225         Backtrack *back = new Backtrack(prev, action_trace);
 226         backtrack_list.push_back(back);
 227 }
 228
 229 Backtrack * ModelChecker::get_next_backtrack()
 230 {
 231         Backtrack *next;
 232         if (backtrack_list.empty())
 233                 return NULL;
 234         next = backtrack_list.back();
 235         backtrack_list.pop_back();
 236         return next;
 237 }
 238
 239 void ModelChecker::check_current_action(void)
 240 {
 241         ModelAction *next = this->current_action;
 242
 243         if (!next) {
 244                 DEBUG("trying to push NULL action...\n");
 245                 return;
 246         }
 247         current_action = NULL;
 248         nextThread = advance_backtracking_state();
 249         next->set_node(currentNode);
 250         set_backtracking(next);
 251         currentNode = currentNode->explore_child(next);
 252         this->action_trace->push_back(next);
 253 }
 254
 255 void ModelChecker::print_summary(void)
 256 {
 257         printf("\n");
 258         printf("Number of executions: %d\n", num_executions);
 259         printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
 260
 261         scheduler->print();
 262
 263         print_list(action_trace);
 264         printf("\n");
 265
 266 }
 267
 268 void ModelChecker::print_list(action_list_t *list)
 269 {
 270         action_list_t::iterator it;
 271
 272         printf("---------------------------------------------------------------------\n");
 273         printf("Trace:\n");
 274
 275         for (it = list->begin(); it != list->end(); it++) {
 276                 (*it)->print();
 277         }
 278         printf("---------------------------------------------------------------------\n");
 279 }
 280
 281 int ModelChecker::add_thread(Thread *t)
 282 {
 283         thread_map[id_to_int(t->get_id())] = t;
 284         scheduler->add_thread(t);
 285         return 0;
 286 }
 287
 288 void ModelChecker::remove_thread(Thread *t)
 289 {
 290         scheduler->remove_thread(t);
 291 }
 292
 293 int ModelChecker::switch_to_master(ModelAction *act)
 294 {
 295         Thread *old;
 296
 297         DBG();
 298         old = thread_current();
 299         set_current_action(act);
 300         old->set_state(THREAD_READY);
 301         return Thread::swap(old, get_system_context());
 302 }