model.cc

   1 #include <stdio.h>
   2 #include <algorithm>
   3 #include <new>
   4 #include <stdarg.h>
   5 #include <string.h>
   6 #include <cstdlib>
   7
   8 #include "model.h"
   9 #include "action.h"
  10 #include "schedule.h"
  11 #include "snapshot-interface.h"
  12 #include "common.h"
  13 #include "datarace.h"
  14 #include "threads-model.h"
  15 #include "output.h"
  16 #include "traceanalysis.h"
  17 #include "execution.h"
  18 #include "history.h"
  19 #include "bugmessage.h"
  20 #include "params.h"
  21
  22 ModelChecker *model = NULL;
  23
  24 /** Wrapper to run the user's main function, with appropriate arguments */
  25 void user_main_wrapper(void *)
  26 {
  27         user_main(model->params.argc, model->params.argv);
  28 }
  29
  30 /** @brief Constructor */
  31 ModelChecker::ModelChecker() :
  32         /* Initialize default scheduler */
  33         params(),
  34         restart_flag(false),
  35         scheduler(new Scheduler()),
  36         execution(new ModelExecution(this, scheduler)),
  37         history(new ModelHistory()),
  38         execution_number(1),
  39         trace_analyses(),
  40         inspect_plugin(NULL)
  41 {
  42         memset(&stats,0,sizeof(struct execution_stats));
  43         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), &user_main_wrapper, NULL, NULL);    // L: user_main_wrapper passes the user program
  44         execution->add_thread(init_thread);
  45         scheduler->set_current_thread(init_thread);
  46         execution->setParams(&params);
  47         param_defaults(&params);
  48         initRaceDetector();
  49 }
  50
  51 /** @brief Destructor */
  52 ModelChecker::~ModelChecker()
  53 {
  54         delete scheduler;
  55 }
  56
  57 /** Method to set parameters */
  58 model_params * ModelChecker::getParams() {
  59         return &params;
  60 }
  61
  62 /**
  63  * Restores user program to initial state and resets all model-checker data
  64  * structures.
  65  */
  66 void ModelChecker::reset_to_initial_state()
  67 {
  68
  69         /**
  70          * FIXME: if we utilize partial rollback, we will need to free only
  71          * those pending actions which were NOT pending before the rollback
  72          * point
  73          */
  74         for (unsigned int i = 0;i < get_num_threads();i++)
  75                 delete get_thread(int_to_id(i))->get_pending();
  76
  77         snapshot_backtrack_before(0);
  78 }
  79
  80 /** @return the number of user threads created during this execution */
  81 unsigned int ModelChecker::get_num_threads() const
  82 {
  83         return execution->get_num_threads();
  84 }
  85
  86 /**
  87  * Must be called from user-thread context (e.g., through the global
  88  * thread_current() interface)
  89  *
  90  * @return The currently executing Thread.
  91  */
  92 Thread * ModelChecker::get_current_thread() const
  93 {
  94         return scheduler->get_current_thread();
  95 }
  96
  97 /**
  98  * @brief Choose the next thread to execute.
  99  *
 100  * This function chooses the next thread that should execute. It can enforce
 101  * execution replay/backtracking or, if the model-checker has no preference
 102  * regarding the next thread (i.e., when exploring a new execution ordering),
 103  * we defer to the scheduler.
 104  *
 105  * @return The next chosen thread to run, if any exist. Or else if the current
 106  * execution should terminate, return NULL.
 107  */
 108 Thread * ModelChecker::get_next_thread()
 109 {
 110
 111         /*
 112          * Have we completed exploring the preselected path? Then let the
 113          * scheduler decide
 114          */
 115         return scheduler->select_next_thread();
 116 }
 117
 118 /**
 119  * @brief Assert a bug in the executing program.
 120  *
 121  * Use this function to assert any sort of bug in the user program. If the
 122  * current trace is feasible (actually, a prefix of some feasible execution),
 123  * then this execution will be aborted, printing the appropriate message. If
 124  * the current trace is not yet feasible, the error message will be stashed and
 125  * printed if the execution ever becomes feasible.
 126  *
 127  * @param msg Descriptive message for the bug (do not include newline char)
 128  * @return True if bug is immediately-feasible
 129  */
 130 bool ModelChecker::assert_bug(const char *msg, ...)
 131 {
 132         char str[800];
 133
 134         va_list ap;
 135         va_start(ap, msg);
 136         vsnprintf(str, sizeof(str), msg, ap);
 137         va_end(ap);
 138
 139         return execution->assert_bug(str);
 140 }
 141
 142 /**
 143  * @brief Assert a bug in the executing program, asserted by a user thread
 144  * @see ModelChecker::assert_bug
 145  * @param msg Descriptive message for the bug (do not include newline char)
 146  */
 147 void ModelChecker::assert_user_bug(const char *msg)
 148 {
 149         /* If feasible bug, bail out now */
 150         if (assert_bug(msg))
 151                 switch_to_master(NULL);
 152 }
 153
 154 /** @brief Print bug report listing for this execution (if any bugs exist) */
 155 void ModelChecker::print_bugs() const
 156 {
 157         SnapVector<bug_message *> *bugs = execution->get_bugs();
 158
 159         model_print("Bug report: %zu bug%s detected\n",
 160                                                         bugs->size(),
 161                                                         bugs->size() > 1 ? "s" : "");
 162         for (unsigned int i = 0;i < bugs->size();i++)
 163                 (*bugs)[i]->print();
 164 }
 165
 166 /**
 167  * @brief Record end-of-execution stats
 168  *
 169  * Must be run when exiting an execution. Records various stats.
 170  * @see struct execution_stats
 171  */
 172 void ModelChecker::record_stats()
 173 {
 174         stats.num_total++;
 175         if (!execution->isfeasibleprefix())
 176                 stats.num_infeasible++;
 177         else if (execution->have_bug_reports())
 178                 stats.num_buggy_executions++;
 179         else if (execution->is_complete_execution())
 180                 stats.num_complete++;
 181         else {
 182                 stats.num_redundant++;
 183
 184                 /**
 185                  * @todo We can violate this ASSERT() when fairness/sleep sets
 186                  * conflict to cause an execution to terminate, e.g. with:
 187                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 188                  */
 189                 //ASSERT(scheduler->all_threads_sleeping());
 190         }
 191 }
 192
 193 /** @brief Print execution stats */
 194 void ModelChecker::print_stats() const
 195 {
 196         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 197         model_print("Number of redundant executions: %d\n", stats.num_redundant);
 198         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 199         model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
 200         model_print("Total executions: %d\n", stats.num_total);
 201 }
 202
 203 /**
 204  * @brief End-of-exeuction print
 205  * @param printbugs Should any existing bugs be printed?
 206  */
 207 void ModelChecker::print_execution(bool printbugs) const
 208 {
 209         model_print("Program output from execution %d:\n",
 210                                                         get_execution_number());
 211         print_program_output();
 212
 213         if (params.verbose >= 3) {
 214                 print_stats();
 215         }
 216
 217         /* Don't print invalid bugs */
 218         if (printbugs && execution->have_bug_reports()) {
 219                 model_print("\n");
 220                 print_bugs();
 221         }
 222
 223         model_print("\n");
 224         execution->print_summary();
 225 }
 226
 227 /**
 228  * Queries the model-checker for more executions to explore and, if one
 229  * exists, resets the model-checker state to execute a new execution.
 230  *
 231  * @return If there are more executions to explore, return true. Otherwise,
 232  * return false.
 233  */
 234 bool ModelChecker::next_execution()
 235 {
 236         DBG();
 237         /* Is this execution a feasible execution that's worth bug-checking? */
 238         bool complete = execution->isfeasibleprefix() &&
 239                                                                         (execution->is_complete_execution() ||
 240                                                                          execution->have_bug_reports());
 241
 242         /* End-of-execution bug checks */
 243         if (complete) {
 244                 if (execution->is_deadlocked())
 245                         assert_bug("Deadlock detected");
 246
 247                 checkDataRaces();
 248                 run_trace_analyses();
 249         }
 250
 251         record_stats();
 252         /* Output */
 253         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 254                 print_execution(complete);
 255         else
 256                 clear_program_output();
 257
 258         if (restart_flag) {
 259                 do_restart();
 260                 return true;
 261         }
 262 // test code
 263         execution_number++;
 264         reset_to_initial_state();
 265         return false;
 266 }
 267
 268 /** @brief Run trace analyses on complete trace */
 269 void ModelChecker::run_trace_analyses() {
 270         for (unsigned int i = 0;i < trace_analyses.size();i++)
 271                 trace_analyses[i]->analyze(execution->get_action_trace());
 272 }
 273
 274 /**
 275  * @brief Get a Thread reference by its ID
 276  * @param tid The Thread's ID
 277  * @return A Thread reference
 278  */
 279 Thread * ModelChecker::get_thread(thread_id_t tid) const
 280 {
 281         return execution->get_thread(tid);
 282 }
 283
 284 /**
 285  * @brief Get a reference to the Thread in which a ModelAction was executed
 286  * @param act The ModelAction
 287  * @return A Thread reference
 288  */
 289 Thread * ModelChecker::get_thread(const ModelAction *act) const
 290 {
 291         return execution->get_thread(act);
 292 }
 293
 294 /**
 295  * Switch from a model-checker context to a user-thread context. This is the
 296  * complement of ModelChecker::switch_to_master and must be called from the
 297  * model-checker context
 298  *
 299  * @param thread The user-thread to switch to
 300  */
 301 void ModelChecker::switch_from_master(Thread *thread)
 302 {
 303         scheduler->set_current_thread(thread);
 304         Thread::swap(&system_context, thread);
 305 }
 306
 307 /**
 308  * Switch from a user-context to the "master thread" context (a.k.a. system
 309  * context). This switch is made with the intention of exploring a particular
 310  * model-checking action (described by a ModelAction object). Must be called
 311  * from a user-thread context.
 312  *
 313  * @param act The current action that will be explored. May be NULL only if
 314  * trace is exiting via an assertion (see ModelExecution::set_assert and
 315  * ModelExecution::has_asserted).
 316  * @return Return the value returned by the current action
 317  */
 318 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 319 {
 320         if (forklock) {
 321                 static bool fork_message_printed = false;
 322
 323                 if (!fork_message_printed) {
 324                         model_print("Fork handler trying to call into model checker...\n");
 325                         fork_message_printed = true;
 326                 }
 327                 delete act;
 328                 return 0;
 329         }
 330         DBG();
 331         Thread *old = thread_current();
 332         scheduler->set_current_thread(NULL);
 333         ASSERT(!old->get_pending());
 334
 335         if (inspect_plugin != NULL) {
 336                 inspect_plugin->inspectModelAction(act);
 337         }
 338
 339         old->set_pending(act);
 340         if (Thread::swap(old, &system_context) < 0) {
 341                 perror("swap threads");
 342                 exit(EXIT_FAILURE);
 343         }
 344         return old->get_return_value();
 345 }
 346
 347 static void runChecker() {
 348         model->run();
 349         delete model;
 350 }
 351
 352 void ModelChecker::startChecker() {
 353         startExecution(get_system_context(), runChecker);
 354 }
 355
 356 bool ModelChecker::should_terminate_execution()
 357 {
 358         /* Infeasible -> don't take any more steps */
 359         if (execution->is_infeasible())
 360                 return true;
 361         else if (execution->isfeasibleprefix() && execution->have_bug_reports()) {
 362                 execution->set_assert();
 363                 return true;
 364         }
 365         return false;
 366 }
 367
 368 /** @brief Restart ModelChecker upon returning to the run loop of the
 369  *      model checker. */
 370 void ModelChecker::restart()
 371 {
 372         restart_flag = true;
 373 }
 374
 375 void ModelChecker::do_restart()
 376 {
 377         restart_flag = false;
 378         reset_to_initial_state();
 379         memset(&stats,0,sizeof(struct execution_stats));
 380         execution_number = 1;
 381 }
 382
 383 void ModelChecker::startMainThread() {
 384         init_thread->set_state(THREAD_RUNNING);
 385         scheduler->set_current_thread(init_thread);
 386         thread_startup();
 387 }
 388
 389 static bool is_nonsc_write(const ModelAction *act) {
 390         if (act->get_type() == ATOMIC_WRITE) {
 391                 std::memory_order order = act->get_mo();
 392                 switch(order) {
 393                 case std::memory_order_relaxed:
 394                 case std::memory_order_release:
 395                         return true;
 396                 default:
 397                         return false;
 398                 }
 399         }
 400         return false;
 401 }
 402
 403 /** @brief Run ModelChecker for the user program */
 404 void ModelChecker::run()
 405 {
 406         //Need to initial random number generator state to avoid resets on rollback
 407         char random_state[256];
 408         initstate(423121, random_state, sizeof(random_state));
 409
 410         for(int exec = 0;exec < params.maxexecutions;exec++) {
 411                 Thread * t = init_thread;
 412
 413                 do {
 414                         /*
 415                          * Stash next pending action(s) for thread(s). There
 416                          * should only need to stash one thread's action--the
 417                          * thread which just took a step--plus the first step
 418                          * for any newly-created thread
 419                          */
 420                         ModelAction * pending;
 421                         for (unsigned int i = 0;i < get_num_threads();i++) {
 422                                 thread_id_t tid = int_to_id(i);
 423                                 Thread *thr = get_thread(tid);
 424                                 if (!thr->is_model_thread() && !thr->is_complete() && ((!(pending=thr->get_pending())) || is_nonsc_write(pending)) ) {
 425                                         switch_from_master(thr);        // L: context swapped, and action type of thr changed.
 426                                         if (thr->is_waiting_on(thr))
 427                                                 assert_bug("Deadlock detected (thread %u)", i);
 428                                 }
 429                         }
 430
 431                         /* Don't schedule threads which should be disabled */
 432                         for (unsigned int i = 0;i < get_num_threads();i++) {
 433                                 Thread *th = get_thread(int_to_id(i));
 434                                 ModelAction *act = th->get_pending();
 435                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 436                                         scheduler->sleep(th);
 437                                 }
 438                         }
 439
 440                         for (unsigned int i = 1;i < get_num_threads();i++) {
 441                                 Thread *th = get_thread(int_to_id(i));
 442                                 ModelAction *act = th->get_pending();
 443                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 444                                         if (act->is_write()) {
 445                                                 std::memory_order order = act->get_mo();
 446                                                 if (order == std::memory_order_relaxed || \
 447                                                                 order == std::memory_order_release) {
 448                                                         t = th;
 449                                                         break;
 450                                                 }
 451                                         } else if (act->get_type() == THREAD_CREATE || \
 452                                                                                  act->get_type() == PTHREAD_CREATE || \
 453                                                                                  act->get_type() == THREAD_START || \
 454                                                                                  act->get_type() == THREAD_FINISH) {
 455                                                 t = th;
 456                                                 break;
 457                                         }
 458                                 }
 459                         }
 460
 461                         /* Catch assertions from prior take_step or from
 462                         * between-ModelAction bugs (e.g., data races) */
 463
 464                         if (execution->has_asserted())
 465                                 break;
 466                         if (!t)
 467                                 t = get_next_thread();
 468                         if (!t || t->is_model_thread())
 469                                 break;
 470
 471                         /* Consume the next action for a Thread */
 472                         ModelAction *curr = t->get_pending();
 473                         t->set_pending(NULL);
 474                         t = execution->take_step(curr);
 475                 } while (!should_terminate_execution());
 476                 next_execution();
 477                 //restore random number generator state after rollback
 478                 setstate(random_state);
 479         }
 480
 481         model_print("******* Model-checking complete: *******\n");
 482         print_stats();
 483
 484         /* Have the trace analyses dump their output. */
 485         for (unsigned int i = 0;i < trace_analyses.size();i++)
 486                 trace_analyses[i]->finish();
 487 }