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