11 #include "snapshot-interface.h"
14 #include "threads-model.h"
16 #include "traceanalysis.h"
17 #include "execution.h"
18 #include "bugmessage.h"
20 #define INITIAL_THREAD_ID 0
24 /** @brief Constructor */
25 ModelChecker::ModelChecker(struct model_params params) :
26 /* Initialize default scheduler */
28 scheduler(new Scheduler()),
29 node_stack(new NodeStack()),
30 execution(new ModelExecution(¶ms, scheduler, node_stack)),
32 earliest_diverge(NULL),
33 trace_analyses(new ModelVector<TraceAnalysis *>())
37 /** @brief Destructor */
38 ModelChecker::~ModelChecker()
41 for (unsigned int i = 0; i < trace_analyses->size(); i++)
42 delete (*trace_analyses)[i];
43 delete trace_analyses;
48 * Restores user program to initial state and resets all model-checker data
51 void ModelChecker::reset_to_initial_state()
53 DEBUG("+++ Resetting to initial state +++\n");
54 node_stack->reset_execution();
57 * FIXME: if we utilize partial rollback, we will need to free only
58 * those pending actions which were NOT pending before the rollback
61 for (unsigned int i = 0; i < get_num_threads(); i++)
62 delete get_thread(int_to_id(i))->get_pending();
64 snapshot_backtrack_before(0);
67 /** @return the number of user threads created during this execution */
68 unsigned int ModelChecker::get_num_threads() const
70 return execution->get_num_threads();
74 * Must be called from user-thread context (e.g., through the global
75 * thread_current() interface)
77 * @return The currently executing Thread.
79 Thread * ModelChecker::get_current_thread() const
81 return scheduler->get_current_thread();
85 * @brief Choose the next thread to execute.
87 * This function chooses the next thread that should execute. It can enforce
88 * execution replay/backtracking or, if the model-checker has no preference
89 * regarding the next thread (i.e., when exploring a new execution ordering),
90 * we defer to the scheduler.
92 * @return The next chosen thread to run, if any exist. Or else if the current
93 * execution should terminate, return NULL.
95 Thread * ModelChecker::get_next_thread()
100 * Have we completed exploring the preselected path? Then let the
104 return scheduler->select_next_thread(node_stack->get_head());
107 /* Else, we are trying to replay an execution */
108 ModelAction *next = node_stack->get_next()->get_action();
110 if (next == diverge) {
111 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
112 earliest_diverge = diverge;
114 Node *nextnode = next->get_node();
115 Node *prevnode = nextnode->get_parent();
116 scheduler->update_sleep_set(prevnode);
118 /* Reached divergence point */
119 if (nextnode->increment_behaviors()) {
120 /* Execute the same thread with a new behavior */
121 tid = next->get_tid();
122 node_stack->pop_restofstack(2);
125 /* Make a different thread execute for next step */
126 scheduler->add_sleep(get_thread(next->get_tid()));
127 tid = prevnode->get_next_backtrack();
128 /* Make sure the backtracked thread isn't sleeping. */
129 node_stack->pop_restofstack(1);
130 if (diverge == earliest_diverge) {
131 earliest_diverge = prevnode->get_action();
134 /* Start the round robin scheduler from this thread id */
135 scheduler->set_scheduler_thread(tid);
136 /* The correct sleep set is in the parent node. */
139 DEBUG("*** Divergence point ***\n");
143 tid = next->get_tid();
145 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
146 ASSERT(tid != THREAD_ID_T_NONE);
147 return get_thread(id_to_int(tid));
151 * We need to know what the next actions of all threads in the sleep
152 * set will be. This method computes them and stores the actions at
153 * the corresponding thread object's pending action.
155 void ModelChecker::execute_sleep_set()
157 for (unsigned int i = 0; i < get_num_threads(); i++) {
158 thread_id_t tid = int_to_id(i);
159 Thread *thr = get_thread(tid);
160 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
161 thr->get_pending()->set_sleep_flag();
167 * @brief Assert a bug in the executing program.
169 * Use this function to assert any sort of bug in the user program. If the
170 * current trace is feasible (actually, a prefix of some feasible execution),
171 * then this execution will be aborted, printing the appropriate message. If
172 * the current trace is not yet feasible, the error message will be stashed and
173 * printed if the execution ever becomes feasible.
175 * @param msg Descriptive message for the bug (do not include newline char)
176 * @return True if bug is immediately-feasible
178 bool ModelChecker::assert_bug(const char *msg, ...)
184 vsnprintf(str, sizeof(str), msg, ap);
187 return execution->assert_bug(str);
191 * @brief Assert a bug in the executing program, asserted by a user thread
192 * @see ModelChecker::assert_bug
193 * @param msg Descriptive message for the bug (do not include newline char)
195 void ModelChecker::assert_user_bug(const char *msg)
197 /* If feasible bug, bail out now */
199 switch_to_master(NULL);
202 /** @brief Print bug report listing for this execution (if any bugs exist) */
203 void ModelChecker::print_bugs() const
205 if (execution->have_bug_reports()) {
206 SnapVector<bug_message *> *bugs = execution->get_bugs();
208 model_print("Bug report: %zu bug%s detected\n",
210 bugs->size() > 1 ? "s" : "");
211 for (unsigned int i = 0; i < bugs->size(); i++)
217 * @brief Record end-of-execution stats
219 * Must be run when exiting an execution. Records various stats.
220 * @see struct execution_stats
222 void ModelChecker::record_stats()
225 if (!execution->isfeasibleprefix())
226 stats.num_infeasible++;
227 else if (execution->have_bug_reports())
228 stats.num_buggy_executions++;
229 else if (execution->is_complete_execution())
230 stats.num_complete++;
232 stats.num_redundant++;
235 * @todo We can violate this ASSERT() when fairness/sleep sets
236 * conflict to cause an execution to terminate, e.g. with:
237 * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
239 //ASSERT(scheduler->all_threads_sleeping());
243 /** @brief Print execution stats */
244 void ModelChecker::print_stats() const
246 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
247 model_print("Number of redundant executions: %d\n", stats.num_redundant);
248 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
249 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
250 model_print("Total executions: %d\n", stats.num_total);
251 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
255 * @brief End-of-exeuction print
256 * @param printbugs Should any existing bugs be printed?
258 void ModelChecker::print_execution(bool printbugs) const
260 print_program_output();
262 if (params.verbose) {
263 model_print("Earliest divergence point since last feasible execution:\n");
264 if (earliest_diverge)
265 earliest_diverge->print();
267 model_print("(Not set)\n");
273 /* Don't print invalid bugs */
278 execution->print_summary();
282 * Queries the model-checker for more executions to explore and, if one
283 * exists, resets the model-checker state to execute a new execution.
285 * @return If there are more executions to explore, return true. Otherwise,
288 bool ModelChecker::next_execution()
291 /* Is this execution a feasible execution that's worth bug-checking? */
292 bool complete = execution->isfeasibleprefix() &&
293 (execution->is_complete_execution() ||
294 execution->have_bug_reports());
296 /* End-of-execution bug checks */
298 if (execution->is_deadlocked())
299 assert_bug("Deadlock detected");
302 run_trace_analyses();
308 if (params.verbose || (complete && execution->have_bug_reports()))
309 print_execution(complete);
311 clear_program_output();
314 earliest_diverge = NULL;
316 if ((diverge = execution->get_next_backtrack()) == NULL)
320 model_print("Next execution will diverge at:\n");
324 execution->increment_execution_number();
325 reset_to_initial_state();
329 /** @brief Run trace analyses on complete trace */
330 void ModelChecker::run_trace_analyses() {
331 for (unsigned int i = 0; i < trace_analyses->size(); i++)
332 (*trace_analyses)[i]->analyze(execution->get_action_trace());
336 * @brief Get a Thread reference by its ID
337 * @param tid The Thread's ID
338 * @return A Thread reference
340 Thread * ModelChecker::get_thread(thread_id_t tid) const
342 return execution->get_thread(tid);
346 * @brief Get a reference to the Thread in which a ModelAction was executed
347 * @param act The ModelAction
348 * @return A Thread reference
350 Thread * ModelChecker::get_thread(const ModelAction *act) const
352 return execution->get_thread(act);
356 * @brief Check if a Thread is currently enabled
357 * @param t The Thread to check
358 * @return True if the Thread is currently enabled
360 bool ModelChecker::is_enabled(Thread *t) const
362 return scheduler->is_enabled(t);
366 * @brief Check if a Thread is currently enabled
367 * @param tid The ID of the Thread to check
368 * @return True if the Thread is currently enabled
370 bool ModelChecker::is_enabled(thread_id_t tid) const
372 return scheduler->is_enabled(tid);
376 * Switch from a model-checker context to a user-thread context. This is the
377 * complement of ModelChecker::switch_to_master and must be called from the
378 * model-checker context
380 * @param thread The user-thread to switch to
382 void ModelChecker::switch_from_master(Thread *thread)
384 scheduler->set_current_thread(thread);
385 Thread::swap(&system_context, thread);
389 * Switch from a user-context to the "master thread" context (a.k.a. system
390 * context). This switch is made with the intention of exploring a particular
391 * model-checking action (described by a ModelAction object). Must be called
392 * from a user-thread context.
394 * @param act The current action that will be explored. May be NULL only if
395 * trace is exiting via an assertion (see ModelExecution::set_assert and
396 * ModelExecution::has_asserted).
397 * @return Return the value returned by the current action
399 uint64_t ModelChecker::switch_to_master(ModelAction *act)
402 Thread *old = thread_current();
403 scheduler->set_current_thread(NULL);
404 ASSERT(!old->get_pending());
405 old->set_pending(act);
406 if (Thread::swap(old, &system_context) < 0) {
407 perror("swap threads");
410 return old->get_return_value();
413 /** Wrapper to run the user's main function, with appropriate arguments */
414 void user_main_wrapper(void *)
416 user_main(model->params.argc, model->params.argv);
419 bool ModelChecker::should_terminate_execution()
421 /* Infeasible -> don't take any more steps */
422 if (execution->is_infeasible())
424 else if (execution->isfeasibleprefix() && execution->have_bug_reports()) {
425 execution->set_assert();
429 if (execution->too_many_steps())
434 /** @brief Run ModelChecker for the user program */
435 void ModelChecker::run()
439 Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL, NULL);
440 execution->add_thread(t);
444 * Stash next pending action(s) for thread(s). There
445 * should only need to stash one thread's action--the
446 * thread which just took a step--plus the first step
447 * for any newly-created thread
449 for (unsigned int i = 0; i < execution->get_num_threads(); i++) {
450 thread_id_t tid = int_to_id(i);
451 Thread *thr = get_thread(tid);
452 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
453 switch_from_master(thr);
454 if (thr->is_waiting_on(thr))
455 assert_bug("Deadlock detected (thread %u)", i);
459 /* Don't schedule threads which should be disabled */
460 for (unsigned int i = 0; i < get_num_threads(); i++) {
461 Thread *th = get_thread(int_to_id(i));
462 ModelAction *act = th->get_pending();
463 if (act && is_enabled(th) && !execution->check_action_enabled(act)) {
464 scheduler->sleep(th);
468 /* Catch assertions from prior take_step or from
469 * between-ModelAction bugs (e.g., data races) */
470 if (execution->has_asserted())
474 t = get_next_thread();
475 if (!t || t->is_model_thread())
478 /* Consume the next action for a Thread */
479 ModelAction *curr = t->get_pending();
480 t->set_pending(NULL);
481 t = execution->take_step(curr);
482 } while (!should_terminate_execution());
484 } while (next_execution());
486 execution->fixup_release_sequences();
488 model_print("******* Model-checking complete: *******\n");