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         /* 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         exploring(NULL),
  52         nextThread(THREAD_ID_T_NONE),
  53         action_trace(new action_list_t()),
  54         rootNode(new TreeNode()),
  55         currentNode(rootNode)
  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         free_action_list(action_trace);
  67
  68         delete 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 *>::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         nextThread = 0;
  85         /* scheduler reset ? */
  86 }
  87
  88 thread_id_t ModelChecker::get_next_id()
  89 {
  90         return next_thread_id++;
  91 }
  92
  93 int ModelChecker::get_next_seq_num()
  94 {
  95         return ++used_sequence_numbers;
  96 }
  97
  98 Thread * ModelChecker::schedule_next_thread()
  99 {
 100         Thread *t;
 101         if (nextThread == THREAD_ID_T_NONE)
 102                 return NULL;
 103         t = thread_map[id_to_int(nextThread)];
 104
 105         ASSERT(t != NULL);
 106
 107         return t;
 108 }
 109
 110 /*
 111  * get_next_replay_thread() - Choose the next thread in the replay sequence
 112  *
 113  * If we've reached the 'diverge' point, then we pick a thread from the
 114  *   backtracking set.
 115  * Otherwise, we simply return the next thread in the sequence.
 116  */
 117 thread_id_t ModelChecker::get_next_replay_thread()
 118 {
 119         ModelAction *next;
 120         thread_id_t tid;
 121
 122         /* Have we completed exploring the preselected path? */
 123         if (exploring == NULL)
 124                 return THREAD_ID_T_NONE;
 125
 126         /* Else, we are trying to replay an execution */
 127         exploring->advance_state();
 128
 129         ASSERT(exploring->get_state() != NULL);
 130
 131         next = exploring->get_state();
 132
 133         if (next == exploring->get_diverge()) {
 134                 TreeNode *node = next->get_treenode();
 135
 136                 /* Reached divergence point; discard our current 'exploring' */
 137                 DEBUG("*** Discard 'Backtrack' object ***\n");
 138                 tid = node->getNextBacktrack();
 139                 delete exploring;
 140                 exploring = NULL;
 141         } else {
 142                 tid = next->get_tid();
 143         }
 144         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 145         return tid;
 146 }
 147
 148 bool ModelChecker::next_execution()
 149 {
 150         DBG();
 151
 152         num_executions++;
 153         print_summary();
 154         if ((exploring = model->get_next_backtrack()) == NULL)
 155                 return false;
 156
 157         if (DBG_ENABLED()) {
 158                 printf("Next execution will diverge at:\n");
 159                 exploring->get_diverge()->print();
 160                 print_list(exploring->get_trace());
 161         }
 162
 163         model->reset_to_initial_state();
 164         return true;
 165 }
 166
 167 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 168 {
 169         action_type type = act->get_type();
 170
 171         switch (type) {
 172                 case THREAD_CREATE:
 173                 case THREAD_YIELD:
 174                 case THREAD_JOIN:
 175                         return NULL;
 176                 case ATOMIC_READ:
 177                 case ATOMIC_WRITE:
 178                 default:
 179                         break;
 180         }
 181         /* linear search: from most recent to oldest */
 182         action_list_t::reverse_iterator rit;
 183         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 184                 ModelAction *prev = *rit;
 185                 if (act->is_dependent(prev))
 186                         return prev;
 187         }
 188         return NULL;
 189 }
 190
 191 void ModelChecker::set_backtracking(ModelAction *act)
 192 {
 193         ModelAction *prev;
 194         TreeNode *node;
 195         Thread *t = get_thread(act->get_tid());
 196
 197         prev = get_last_conflict(act);
 198         if (prev == NULL)
 199                 return;
 200
 201         node = prev->get_treenode();
 202
 203         while (t && !node->is_enabled(t))
 204                 t = t->get_parent();
 205
 206         /* Check if this has been explored already */
 207         if (node->hasBeenExplored(t->get_id()))
 208                 return;
 209         /* If this is a new backtracking point, mark the tree */
 210         if (node->setBacktrack(t->get_id()) != 0)
 211                 return;
 212
 213         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 214                         prev->get_tid(), t->get_id());
 215         if (DBG_ENABLED()) {
 216                 prev->print();
 217                 act->print();
 218         }
 219
 220         Backtrack *back = new Backtrack(prev, action_trace);
 221         backtrack_list.push_back(back);
 222 }
 223
 224 Backtrack * ModelChecker::get_next_backtrack()
 225 {
 226         Backtrack *next;
 227         if (backtrack_list.empty())
 228                 return NULL;
 229         next = backtrack_list.back();
 230         backtrack_list.pop_back();
 231         return next;
 232 }
 233
 234 void ModelChecker::check_current_action(void)
 235 {
 236         ModelAction *curr = this->current_action;
 237         current_action = NULL;
 238         if (!curr) {
 239                 DEBUG("trying to push NULL action...\n");
 240                 return;
 241         }
 242
 243         nextThread = get_next_replay_thread();
 244         curr->set_node(currentNode);
 245         set_backtracking(curr);
 246         currentNode = currentNode->explore_child(curr);
 247         this->action_trace->push_back(curr);
 248 }
 249
 250 void ModelChecker::print_summary(void)
 251 {
 252         printf("\n");
 253         printf("Number of executions: %d\n", num_executions);
 254         printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
 255
 256         scheduler->print();
 257
 258         print_list(action_trace);
 259         printf("\n");
 260
 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 }