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