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