model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "schedule.h"
   5 #include "common.h"
   6
   7 #define INITIAL_THREAD_ID       0
   8
   9 ModelChecker *model;
  10
  11 ModelChecker::ModelChecker()
  12 {
  13         /* First thread created will have id (INITIAL_THREAD_ID + 1) */
  14         this->used_thread_id = INITIAL_THREAD_ID;
  15         /* Initialize default scheduler */
  16         this->scheduler = new Scheduler();
  17
  18         num_executions = 0;
  19         this->current_action = NULL;
  20         this->exploring = NULL;
  21         this->nextThread = THREAD_ID_T_NONE;
  22
  23         rootNode = new TreeNode(NULL);
  24         currentNode = rootNode;
  25         action_trace = new action_list_t();
  26 }
  27
  28 ModelChecker::~ModelChecker()
  29 {
  30         delete action_trace;
  31         delete this->scheduler;
  32         delete rootNode;
  33 }
  34
  35 void ModelChecker::reset_to_initial_state()
  36 {
  37         DEBUG("+++ Resetting to initial state +++\n");
  38         std::map<thread_id_t, class Thread *>::iterator it;
  39         for (it = thread_map.begin(); it != thread_map.end(); it++) {
  40                 delete (*it).second;
  41         }
  42         thread_map.clear();
  43         action_trace = new action_list_t();
  44         currentNode = rootNode;
  45         current_action = NULL;
  46         used_thread_id = INITIAL_THREAD_ID;
  47         /* scheduler reset ? */
  48 }
  49
  50 int ModelChecker::get_next_id()
  51 {
  52         return ++used_thread_id;
  53 }
  54
  55 Thread * ModelChecker::schedule_next_thread()
  56 {
  57         Thread *t;
  58         if (nextThread == THREAD_ID_T_NONE)
  59                 return NULL;
  60         t = thread_map[nextThread];
  61         if (t == NULL)
  62                 DEBUG("*** error: thread not in thread_map: id = %d\n", nextThread);
  63         return t;
  64 }
  65
  66 /*
  67  * get_next_replay_thread() - Choose the next thread in the replay sequence
  68  *
  69  * If we've reached the 'diverge' point, then we pick a thread from the
  70  *   backtracking set.
  71  * Otherwise, we simply return the next thread in the sequence.
  72  */
  73 thread_id_t ModelChecker::get_next_replay_thread()
  74 {
  75         ModelAction *next;
  76         thread_id_t tid;
  77
  78         next = exploring->get_state();
  79
  80         if (next == exploring->get_diverge()) {
  81                 TreeNode *node = next->get_node();
  82
  83                 /* Reached divergence point; discard our current 'exploring' */
  84                 DEBUG("*** Discard 'Backtrack' object ***\n");
  85                 tid = node->getNextBacktrack();
  86                 delete exploring;
  87                 exploring = NULL;
  88         } else {
  89                 tid = next->get_tid();
  90         }
  91         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
  92         return tid;
  93 }
  94
  95 thread_id_t ModelChecker::advance_backtracking_state()
  96 {
  97         /* Have we completed exploring the preselected path? */
  98         if (exploring == NULL)
  99                 return THREAD_ID_T_NONE;
 100
 101         /* Else, we are trying to replay an execution */
 102         exploring->advance_state();
 103         if (exploring->get_state() == NULL)
 104                 DEBUG("*** error: reached end of backtrack trace\n");
 105
 106         return get_next_replay_thread();
 107 }
 108
 109 bool ModelChecker::next_execution()
 110 {
 111         num_executions++;
 112         print_summary();
 113         if ((exploring = model->get_next_backtrack()) == NULL)
 114                 return false;
 115         model->reset_to_initial_state();
 116         nextThread = get_next_replay_thread();
 117         return true;
 118 }
 119
 120 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 121 {
 122         void *loc = act->get_location();
 123         action_type type = act->get_type();
 124         thread_id_t id = act->get_tid();
 125
 126         switch (type) {
 127                 case THREAD_CREATE:
 128                 case THREAD_YIELD:
 129                 case THREAD_JOIN:
 130                         return NULL;
 131                 case ATOMIC_READ:
 132                 case ATOMIC_WRITE:
 133                 default:
 134                         break;
 135         }
 136         /* linear search: from most recent to oldest */
 137         action_list_t::reverse_iterator rit;
 138         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 139                 ModelAction *prev = *rit;
 140                 if (prev->get_location() != loc)
 141                         continue;
 142                 if (type == ATOMIC_READ && prev->get_type() != ATOMIC_WRITE)
 143                         continue;
 144                 /* Conflict from the same thread is not really a conflict */
 145                 if (id == prev->get_tid())
 146                         continue;
 147                 return prev;
 148         }
 149         return NULL;
 150 }
 151
 152 void ModelChecker::set_backtracking(ModelAction *act)
 153 {
 154         ModelAction *prev;
 155         TreeNode *node;
 156
 157         prev = get_last_conflict(act);
 158         if (prev == NULL)
 159                 return;
 160
 161         node = prev->get_node();
 162
 163         /* Check if this has been explored already */
 164         if (node->hasBeenExplored(act->get_tid()))
 165                 return;
 166         /* If this is a new backtracking point, mark the tree */
 167         if (node->setBacktrack(act->get_tid()) != 0)
 168                 return;
 169
 170         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 171                         prev->get_tid(), act->get_tid());
 172         if (DBG_ENABLED()) {
 173                 prev->print();
 174                 act->print();
 175         }
 176
 177         Backtrack *back = new Backtrack(prev, action_trace);
 178         backtrack_list.push_back(back);
 179 }
 180
 181 Backtrack * ModelChecker::get_next_backtrack()
 182 {
 183         Backtrack *next;
 184         if (backtrack_list.empty())
 185                 return NULL;
 186         next = backtrack_list.back();
 187         backtrack_list.pop_back();
 188         return next;
 189 }
 190
 191 void ModelChecker::check_current_action(void)
 192 {
 193         ModelAction *next = this->current_action;
 194
 195         if (!next) {
 196                 DEBUG("trying to push NULL action...\n");
 197                 return;
 198         }
 199         current_action = NULL;
 200         nextThread = advance_backtracking_state();
 201         next->set_node(currentNode);
 202         set_backtracking(next);
 203         currentNode = currentNode->exploreChild(next->get_tid());
 204         this->action_trace->push_back(next);
 205 }
 206
 207 void ModelChecker::print_summary(void)
 208 {
 209         action_list_t::iterator it;
 210
 211         printf("\n");
 212         printf("---------------------------------------------------------------------\n");
 213         printf("Number of executions: %d\n", num_executions);
 214         printf("Total nodes created: %d\n\n", TreeNode::getTotalNodes());
 215
 216         scheduler->print();
 217
 218         printf("Trace:\n\n");
 219
 220         for (it = action_trace->begin(); it != action_trace->end(); it++) {
 221                 DBG();
 222                 (*it)->print();
 223         }
 224         printf("---------------------------------------------------------------------\n");
 225 }
 226
 227 int ModelChecker::add_thread(Thread *t)
 228 {
 229         thread_map[t->get_id()] = t;
 230         scheduler->add_thread(t);
 231         return 0;
 232 }
 233
 234 void ModelChecker::remove_thread(Thread *t)
 235 {
 236         scheduler->remove_thread(t);
 237 }
 238
 239 int ModelChecker::switch_to_master(ModelAction *act)
 240 {
 241         Thread *old;
 242
 243         DBG();
 244         old = thread_current();
 245         set_current_action(act);
 246         old->set_state(THREAD_READY);
 247         return Thread::swap(old, get_system_context());
 248 }
 249
 250 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 251 {
 252         Thread *t = thread_current();
 253         ModelAction *act = this;
 254
 255         act->type = type;
 256         act->order = order;
 257         act->location = loc;
 258         act->tid = t->get_id();
 259         act->value = value;
 260 }
 261
 262 void ModelAction::print(void)
 263 {
 264         const char *type_str;
 265         switch (this->type) {
 266         case THREAD_CREATE:
 267                 type_str = "thread create";
 268                 break;
 269         case THREAD_YIELD:
 270                 type_str = "thread yield";
 271                 break;
 272         case THREAD_JOIN:
 273                 type_str = "thread join";
 274                 break;
 275         case ATOMIC_READ:
 276                 type_str = "atomic read";
 277                 break;
 278         case ATOMIC_WRITE:
 279                 type_str = "atomic write";
 280                 break;
 281         default:
 282                 type_str = "unknown type";
 283         }
 284
 285         printf("Thread: %d\tAction: %s\tMO: %d\tLoc: %#014zx\tValue: %d\n", tid, type_str, order, (size_t)location, value);
 286 }