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 #ifdef TLS
  28         model->get_execution()->getTLSSize();
  29 #endif
  30         user_main(model->params.argc, model->params.argv);
  31 }
  32
  33 /** @brief Constructor */
  34 ModelChecker::ModelChecker() :
  35         /* Initialize default scheduler */
  36         params(),
  37         restart_flag(false),
  38         scheduler(new Scheduler()),
  39         execution(new ModelExecution(this, scheduler)),
  40         history(new ModelHistory()),
  41         execution_number(1),
  42         trace_analyses(),
  43         inspect_plugin(NULL)
  44 {
  45         memset(&stats,0,sizeof(struct execution_stats));
  46         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
  47 #ifdef TLS
  48         init_thread->setTLS((char *)get_tls_addr());
  49 #endif
  50         execution->add_thread(init_thread);
  51         scheduler->set_current_thread(init_thread);
  52         execution->setParams(&params);
  53         param_defaults(&params);
  54         initRaceDetector();
  55 }
  56
  57 /** @brief Destructor */
  58 ModelChecker::~ModelChecker()
  59 {
  60         delete scheduler;
  61 }
  62
  63 /** Method to set parameters */
  64 model_params * ModelChecker::getParams() {
  65         return &params;
  66 }
  67
  68 /**
  69  * Restores user program to initial state and resets all model-checker data
  70  * structures.
  71  */
  72 void ModelChecker::reset_to_initial_state()
  73 {
  74
  75         /**
  76          * FIXME: if we utilize partial rollback, we will need to free only
  77          * those pending actions which were NOT pending before the rollback
  78          * point
  79          */
  80         for (unsigned int i = 0;i < get_num_threads();i++)
  81                 delete get_thread(int_to_id(i))->get_pending();
  82
  83         snapshot_backtrack_before(0);
  84 }
  85
  86 /** @return the number of user threads created during this execution */
  87 unsigned int ModelChecker::get_num_threads() const
  88 {
  89         return execution->get_num_threads();
  90 }
  91
  92 /**
  93  * Must be called from user-thread context (e.g., through the global
  94  * thread_current() interface)
  95  *
  96  * @return The currently executing Thread.
  97  */
  98 Thread * ModelChecker::get_current_thread() const
  99 {
 100         return scheduler->get_current_thread();
 101 }
 102
 103 /**
 104  * @brief Choose the next thread to execute.
 105  *
 106  * This function chooses the next thread that should execute. It can enforce
 107  * execution replay/backtracking or, if the model-checker has no preference
 108  * regarding the next thread (i.e., when exploring a new execution ordering),
 109  * we defer to the scheduler.
 110  *
 111  * @return The next chosen thread to run, if any exist. Or else if the current
 112  * execution should terminate, return NULL.
 113  */
 114 Thread * ModelChecker::get_next_thread()
 115 {
 116
 117         /*
 118          * Have we completed exploring the preselected path? Then let the
 119          * scheduler decide
 120          */
 121         return scheduler->select_next_thread();
 122 }
 123
 124 /**
 125  * @brief Assert a bug in the executing program.
 126  *
 127  * Use this function to assert any sort of bug in the user program. If the
 128  * current trace is feasible (actually, a prefix of some feasible execution),
 129  * then this execution will be aborted, printing the appropriate message. If
 130  * the current trace is not yet feasible, the error message will be stashed and
 131  * printed if the execution ever becomes feasible.
 132  *
 133  * @param msg Descriptive message for the bug (do not include newline char)
 134  * @return True if bug is immediately-feasible
 135  */
 136 bool ModelChecker::assert_bug(const char *msg, ...)
 137 {
 138         char str[800];
 139
 140         va_list ap;
 141         va_start(ap, msg);
 142         vsnprintf(str, sizeof(str), msg, ap);
 143         va_end(ap);
 144
 145         return execution->assert_bug(str);
 146 }
 147
 148 /**
 149  * @brief Assert a bug in the executing program, asserted by a user thread
 150  * @see ModelChecker::assert_bug
 151  * @param msg Descriptive message for the bug (do not include newline char)
 152  */
 153 void ModelChecker::assert_user_bug(const char *msg)
 154 {
 155         /* If feasible bug, bail out now */
 156         if (assert_bug(msg))
 157                 switch_to_master(NULL);
 158 }
 159
 160 /** @brief Print bug report listing for this execution (if any bugs exist) */
 161 void ModelChecker::print_bugs() const
 162 {
 163         SnapVector<bug_message *> *bugs = execution->get_bugs();
 164
 165         model_print("Bug report: %zu bug%s detected\n",
 166                                                         bugs->size(),
 167                                                         bugs->size() > 1 ? "s" : "");
 168         for (unsigned int i = 0;i < bugs->size();i++)
 169                 (*bugs)[i] -> print();
 170 }
 171
 172 /**
 173  * @brief Record end-of-execution stats
 174  *
 175  * Must be run when exiting an execution. Records various stats.
 176  * @see struct execution_stats
 177  */
 178 void ModelChecker::record_stats()
 179 {
 180         stats.num_total ++;
 181         if (!execution->isfeasibleprefix())
 182                 stats.num_infeasible ++;
 183         else if (execution->have_bug_reports())
 184                 stats.num_buggy_executions ++;
 185         else if (execution->is_complete_execution())
 186                 stats.num_complete ++;
 187         else {
 188                 stats.num_redundant ++;
 189
 190                 /**
 191                  * @todo We can violate this ASSERT() when fairness/sleep sets
 192                  * conflict to cause an execution to terminate, e.g. with:
 193                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 194                  */
 195                 //ASSERT(scheduler->all_threads_sleeping());
 196         }
 197 }
 198
 199 /** @brief Print execution stats */
 200 void ModelChecker::print_stats() const
 201 {
 202         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 203         model_print("Number of redundant executions: %d\n", stats.num_redundant);
 204         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 205         model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
 206         model_print("Total executions: %d\n", stats.num_total);
 207 }
 208
 209 /**
 210  * @brief End-of-exeuction print
 211  * @param printbugs Should any existing bugs be printed?
 212  */
 213 void ModelChecker::print_execution(bool printbugs) const
 214 {
 215         model_print("Program output from execution %d:\n",
 216                                                         get_execution_number());
 217         print_program_output();
 218
 219         if (params.verbose >= 3) {
 220                 print_stats();
 221         }
 222
 223         /* Don't print invalid bugs */
 224         if (printbugs && execution->have_bug_reports()) {
 225                 model_print("\n");
 226                 print_bugs();
 227         }
 228
 229         model_print("\n");
 230         execution->print_summary();
 231 }
 232
 233 /**
 234  * Queries the model-checker for more executions to explore and, if one
 235  * exists, resets the model-checker state to execute a new execution.
 236  *
 237  * @return If there are more executions to explore, return true. Otherwise,
 238  * return false.
 239  */
 240 bool ModelChecker::next_execution()
 241 {
 242         DBG();
 243         /* Is this execution a feasible execution that's worth bug-checking? */
 244         bool complete = execution->isfeasibleprefix() &&
 245                                                                         (execution->is_complete_execution() ||
 246                                                                          execution->have_bug_reports());
 247
 248         /* End-of-execution bug checks */
 249         if (complete) {
 250                 if (execution->is_deadlocked())
 251                         assert_bug("Deadlock detected");
 252
 253                 run_trace_analyses();
 254         }
 255
 256         record_stats();
 257         /* Output */
 258         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 259                 print_execution(complete);
 260         else
 261                 clear_program_output();
 262
 263         if (restart_flag) {
 264                 do_restart();
 265                 return true;
 266         }
 267 // test code
 268         execution_number ++;
 269         reset_to_initial_state();
 270         return false;
 271 }
 272
 273 /** @brief Run trace analyses on complete trace */
 274 void ModelChecker::run_trace_analyses() {
 275         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 276                 trace_analyses[i] -> analyze(execution->get_action_trace());
 277 }
 278
 279 /**
 280  * @brief Get a Thread reference by its ID
 281  * @param tid The Thread's ID
 282  * @return A Thread reference
 283  */
 284 Thread * ModelChecker::get_thread(thread_id_t tid) const
 285 {
 286         return execution->get_thread(tid);
 287 }
 288
 289 /**
 290  * @brief Get a reference to the Thread in which a ModelAction was executed
 291  * @param act The ModelAction
 292  * @return A Thread reference
 293  */
 294 Thread * ModelChecker::get_thread(const ModelAction *act) const
 295 {
 296         return execution->get_thread(act);
 297 }
 298
 299 /**
 300  * Switch from a model-checker context to a user-thread context. This is the
 301  * complement of ModelChecker::switch_to_master and must be called from the
 302  * model-checker context
 303  *
 304  * @param thread The user-thread to switch to
 305  */
 306 void ModelChecker::switch_from_master(Thread *thread)
 307 {
 308         scheduler->set_current_thread(thread);
 309         Thread::swap(&system_context, thread);
 310 }
 311
 312 /**
 313  * Switch from a user-context to the "master thread" context (a.k.a. system
 314  * context). This switch is made with the intention of exploring a particular
 315  * model-checking action (described by a ModelAction object). Must be called
 316  * from a user-thread context.
 317  *
 318  * @param act The current action that will be explored. May be NULL only if
 319  * trace is exiting via an assertion (see ModelExecution::set_assert and
 320  * ModelExecution::has_asserted).
 321  * @return Return the value returned by the current action
 322  */
 323 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 324 {
 325         if (forklock) {
 326                 static bool fork_message_printed = false;
 327
 328                 if (!fork_message_printed) {
 329                         model_print("Fork handler trying to call into model checker...\n");
 330                         fork_message_printed = true;
 331                 }
 332                 delete act;
 333                 return 0;
 334         }
 335         DBG();
 336         Thread *old = thread_current();
 337         scheduler->set_current_thread(NULL);
 338         ASSERT(!old->get_pending());
 339
 340         if (inspect_plugin != NULL) {
 341                 inspect_plugin->inspectModelAction(act);
 342         }
 343
 344         old->set_pending(act);
 345         if (Thread::swap(old, &system_context) < 0) {
 346                 perror("swap threads");
 347                 exit(EXIT_FAILURE);
 348         }
 349         return old->get_return_value();
 350 }
 351
 352 static void runChecker() {
 353         model->run();
 354         delete model;
 355 }
 356
 357 void ModelChecker::startChecker() {
 358         startExecution(get_system_context(), runChecker);
 359 }
 360
 361 bool ModelChecker::should_terminate_execution()
 362 {
 363         /* Infeasible -> don't take any more steps */
 364         if (execution->is_infeasible())
 365                 return true;
 366         else if (execution->isfeasibleprefix() && execution->have_fatal_bug_reports()) {
 367                 execution->set_assert();
 368                 return true;
 369         }
 370         return false;
 371 }
 372
 373 /** @brief Restart ModelChecker upon returning to the run loop of the
 374  *      model checker. */
 375 void ModelChecker::restart()
 376 {
 377         restart_flag = true;
 378 }
 379
 380 void ModelChecker::do_restart()
 381 {
 382         restart_flag = false;
 383         reset_to_initial_state();
 384         memset(&stats,0,sizeof(struct execution_stats));
 385         execution_number = 1;
 386 }
 387
 388 void ModelChecker::startMainThread() {
 389         init_thread->set_state(THREAD_RUNNING);
 390         scheduler->set_current_thread(init_thread);
 391         thread_startup();
 392 }
 393
 394 static bool is_nonsc_write(const ModelAction *act) {
 395         if (act->get_type() == ATOMIC_WRITE) {
 396                 std::memory_order order = act->get_mo();
 397                 switch(order) {
 398                 case std::memory_order_relaxed:
 399                 case std::memory_order_release:
 400                         return true;
 401                 default:
 402                         return false;
 403                 }
 404         }
 405         return false;
 406 }
 407
 408 /** @brief Run ModelChecker for the user program */
 409 void ModelChecker::run()
 410 {
 411         //Need to initial random number generator state to avoid resets on rollback
 412         char random_state[256];
 413         initstate(423121, random_state, sizeof(random_state));
 414
 415         for(int exec = 0;exec < params.maxexecutions;exec++) {
 416                 Thread * t = init_thread;
 417
 418                 do {
 419                         /*
 420                          * Stash next pending action(s) for thread(s). There
 421                          * should only need to stash one thread's action--the
 422                          * thread which just took a step--plus the first step
 423                          * for any newly-created thread
 424                          */
 425                         ModelAction * pending;
 426                         for (unsigned int i = 0;i < get_num_threads();i++) {
 427                                 thread_id_t tid = int_to_id(i);
 428                                 Thread *thr = get_thread(tid);
 429                                 if (!thr->is_model_thread() && !thr->is_complete() && ((!(pending=thr->get_pending())) || is_nonsc_write(pending)) ) {
 430                                         switch_from_master(thr);        // L: context swapped, and action type of thr changed.
 431                                         if (thr->is_waiting_on(thr))
 432                                                 assert_bug("Deadlock detected (thread %u)", i);
 433                                 }
 434                         }
 435
 436                         /* Don't schedule threads which should be disabled */
 437                         for (unsigned int i = 0;i < get_num_threads();i++) {
 438                                 Thread *th = get_thread(int_to_id(i));
 439                                 ModelAction *act = th->get_pending();
 440                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 441                                         scheduler->sleep(th);
 442                                 }
 443                         }
 444
 445                         for (unsigned int i = 1;i < get_num_threads();i++) {
 446                                 Thread *th = get_thread(int_to_id(i));
 447                                 ModelAction *act = th->get_pending();
 448                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 449                                         if (act->is_write()) {
 450                                                 std::memory_order order = act->get_mo();
 451                                                 if (order == std::memory_order_relaxed || \
 452                                                                 order == std::memory_order_release) {
 453                                                         t = th;
 454                                                         break;
 455                                                 }
 456                                         } else if (act->get_type() == THREAD_CREATE || \
 457                                                                                  act->get_type() == PTHREAD_CREATE || \
 458                                                                                  act->get_type() == THREAD_START || \
 459                                                                                  act->get_type() == THREAD_FINISH) {
 460                                                 t = th;
 461                                                 break;
 462                                         }
 463                                 }
 464                         }
 465
 466                         /* Catch assertions from prior take_step or from
 467                         * between-ModelAction bugs (e.g., data races) */
 468
 469                         if (execution->has_asserted())
 470                                 break;
 471                         if (!t)
 472                                 t = get_next_thread();
 473                         if (!t || t->is_model_thread())
 474                                 break;
 475
 476                         /* Consume the next action for a Thread */
 477                         ModelAction *curr = t->get_pending();
 478                         t->set_pending(NULL);
 479                         t = execution->take_step(curr);
 480                 } while (!should_terminate_execution());
 481                 next_execution();
 482                 //restore random number generator state after rollback
 483                 setstate(random_state);
 484         }
 485
 486         model_print("******* Model-checking complete: *******\n");
 487         print_stats();
 488
 489         /* Have the trace analyses dump their output. */
 490         for (unsigned int i = 0;i < trace_analyses.size();i++)
 491                 trace_analyses[i]->finish();
 492 }