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),
37 /** @brief Destructor */
38 ModelChecker::~ModelChecker()
41 for (unsigned int i = 0; i < trace_analyses.size(); i++)
42 delete trace_analyses[i];
47 * Restores user program to initial state and resets all model-checker data
50 void ModelChecker::reset_to_initial_state()
52 DEBUG("+++ Resetting to initial state +++\n");
53 node_stack->reset_execution();
56 * FIXME: if we utilize partial rollback, we will need to free only
57 * those pending actions which were NOT pending before the rollback
60 for (unsigned int i = 0; i < get_num_threads(); i++)
61 delete get_thread(int_to_id(i))->get_pending();
63 snapshot_backtrack_before(0);
66 /** @return the number of user threads created during this execution */
67 unsigned int ModelChecker::get_num_threads() const
69 return execution->get_num_threads();
73 * Must be called from user-thread context (e.g., through the global
74 * thread_current() interface)
76 * @return The currently executing Thread.
78 Thread * ModelChecker::get_current_thread() const
80 return scheduler->get_current_thread();
84 * @brief Choose the next thread to execute.
86 * This function chooses the next thread that should execute. It can enforce
87 * execution replay/backtracking or, if the model-checker has no preference
88 * regarding the next thread (i.e., when exploring a new execution ordering),
89 * we defer to the scheduler.
91 * @return The next chosen thread to run, if any exist. Or else if the current
92 * execution should terminate, return NULL.
94 Thread * ModelChecker::get_next_thread()
99 * Have we completed exploring the preselected path? Then let the
103 return scheduler->select_next_thread(node_stack->get_head());
106 /* Else, we are trying to replay an execution */
107 ModelAction *next = node_stack->get_next()->get_action();
109 if (next == diverge) {
110 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
111 earliest_diverge = diverge;
113 Node *nextnode = next->get_node();
114 Node *prevnode = nextnode->get_parent();
115 scheduler->update_sleep_set(prevnode);
117 /* Reached divergence point */
118 if (nextnode->increment_behaviors()) {
119 /* Execute the same thread with a new behavior */
120 tid = next->get_tid();
121 node_stack->pop_restofstack(2);
124 /* Make a different thread execute for next step */
125 scheduler->add_sleep(get_thread(next->get_tid()));
126 tid = prevnode->get_next_backtrack();
127 /* Make sure the backtracked thread isn't sleeping. */
128 node_stack->pop_restofstack(1);
129 if (diverge == earliest_diverge) {
130 earliest_diverge = prevnode->get_action();
133 /* Start the round robin scheduler from this thread id */
134 scheduler->set_scheduler_thread(tid);
135 /* The correct sleep set is in the parent node. */
138 DEBUG("*** Divergence point ***\n");
142 tid = next->get_tid();
144 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
145 ASSERT(tid != THREAD_ID_T_NONE);
146 return get_thread(id_to_int(tid));
150 * We need to know what the next actions of all threads in the sleep
151 * set will be. This method computes them and stores the actions at
152 * the corresponding thread object's pending action.
154 void ModelChecker::execute_sleep_set()
156 for (unsigned int i = 0; i < get_num_threads(); i++) {
157 thread_id_t tid = int_to_id(i);
158 Thread *thr = get_thread(tid);
159 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
160 thr->get_pending()->set_sleep_flag();
166 * @brief Assert a bug in the executing program.
168 * Use this function to assert any sort of bug in the user program. If the
169 * current trace is feasible (actually, a prefix of some feasible execution),
170 * then this execution will be aborted, printing the appropriate message. If
171 * the current trace is not yet feasible, the error message will be stashed and
172 * printed if the execution ever becomes feasible.
174 * @param msg Descriptive message for the bug (do not include newline char)
175 * @return True if bug is immediately-feasible
177 bool ModelChecker::assert_bug(const char *msg, ...)
183 vsnprintf(str, sizeof(str), msg, ap);
186 return execution->assert_bug(str);
190 * @brief Assert a bug in the executing program, asserted by a user thread
191 * @see ModelChecker::assert_bug
192 * @param msg Descriptive message for the bug (do not include newline char)
194 void ModelChecker::assert_user_bug(const char *msg)
196 /* If feasible bug, bail out now */
198 switch_to_master(NULL);
201 /** @brief Print bug report listing for this execution (if any bugs exist) */
202 void ModelChecker::print_bugs() const
204 if (execution->have_bug_reports()) {
205 SnapVector<bug_message *> *bugs = execution->get_bugs();
207 model_print("Bug report: %zu bug%s detected\n",
209 bugs->size() > 1 ? "s" : "");
210 for (unsigned int i = 0; i < bugs->size(); i++)
216 * @brief Record end-of-execution stats
218 * Must be run when exiting an execution. Records various stats.
219 * @see struct execution_stats
221 void ModelChecker::record_stats()
224 if (!execution->isfeasibleprefix())
225 stats.num_infeasible++;
226 else if (execution->have_bug_reports())
227 stats.num_buggy_executions++;
228 else if (execution->is_complete_execution())
229 stats.num_complete++;
231 stats.num_redundant++;
234 * @todo We can violate this ASSERT() when fairness/sleep sets
235 * conflict to cause an execution to terminate, e.g. with:
236 * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
238 //ASSERT(scheduler->all_threads_sleeping());
242 /** @brief Print execution stats */
243 void ModelChecker::print_stats() const
245 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
246 model_print("Number of redundant executions: %d\n", stats.num_redundant);
247 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
248 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
249 model_print("Total executions: %d\n", stats.num_total);
250 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
254 * @brief End-of-exeuction print
255 * @param printbugs Should any existing bugs be printed?
257 void ModelChecker::print_execution(bool printbugs) const
259 print_program_output();
261 if (params.verbose) {
262 model_print("Earliest divergence point since last feasible execution:\n");
263 if (earliest_diverge)
264 earliest_diverge->print();
266 model_print("(Not set)\n");
272 /* Don't print invalid bugs */
277 execution->print_summary();
281 * Queries the model-checker for more executions to explore and, if one
282 * exists, resets the model-checker state to execute a new execution.
284 * @return If there are more executions to explore, return true. Otherwise,
287 bool ModelChecker::next_execution()
290 /* Is this execution a feasible execution that's worth bug-checking? */
291 bool complete = execution->isfeasibleprefix() &&
292 (execution->is_complete_execution() ||
293 execution->have_bug_reports());
295 /* End-of-execution bug checks */
297 if (execution->is_deadlocked())
298 assert_bug("Deadlock detected");
301 run_trace_analyses();
307 if (params.verbose || (complete && execution->have_bug_reports()))
308 print_execution(complete);
310 clear_program_output();
313 earliest_diverge = NULL;
315 if ((diverge = execution->get_next_backtrack()) == NULL)
319 model_print("Next execution will diverge at:\n");
323 execution->increment_execution_number();
324 reset_to_initial_state();
328 /** @brief Run trace analyses on complete trace */
329 void ModelChecker::run_trace_analyses() {
330 for (unsigned int i = 0; i < trace_analyses.size(); i++)
331 trace_analyses[i]->analyze(execution->get_action_trace());
335 * @brief Get a Thread reference by its ID
336 * @param tid The Thread's ID
337 * @return A Thread reference
339 Thread * ModelChecker::get_thread(thread_id_t tid) const
341 return execution->get_thread(tid);
345 * @brief Get a reference to the Thread in which a ModelAction was executed
346 * @param act The ModelAction
347 * @return A Thread reference
349 Thread * ModelChecker::get_thread(const ModelAction *act) const
351 return execution->get_thread(act);
355 * @brief Check if a Thread is currently enabled
356 * @param t The Thread to check
357 * @return True if the Thread is currently enabled
359 bool ModelChecker::is_enabled(Thread *t) const
361 return scheduler->is_enabled(t);
365 * @brief Check if a Thread is currently enabled
366 * @param tid The ID of the Thread to check
367 * @return True if the Thread is currently enabled
369 bool ModelChecker::is_enabled(thread_id_t tid) const
371 return scheduler->is_enabled(tid);
375 * Switch from a model-checker context to a user-thread context. This is the
376 * complement of ModelChecker::switch_to_master and must be called from the
377 * model-checker context
379 * @param thread The user-thread to switch to
381 void ModelChecker::switch_from_master(Thread *thread)
383 scheduler->set_current_thread(thread);
384 Thread::swap(&system_context, thread);
388 * Switch from a user-context to the "master thread" context (a.k.a. system
389 * context). This switch is made with the intention of exploring a particular
390 * model-checking action (described by a ModelAction object). Must be called
391 * from a user-thread context.
393 * @param act The current action that will be explored. May be NULL only if
394 * trace is exiting via an assertion (see ModelExecution::set_assert and
395 * ModelExecution::has_asserted).
396 * @return Return the value returned by the current action
398 uint64_t ModelChecker::switch_to_master(ModelAction *act)
401 Thread *old = thread_current();
402 scheduler->set_current_thread(NULL);
403 ASSERT(!old->get_pending());
404 old->set_pending(act);
405 if (Thread::swap(old, &system_context) < 0) {
406 perror("swap threads");
409 return old->get_return_value();
412 /** Wrapper to run the user's main function, with appropriate arguments */
413 void user_main_wrapper(void *)
415 user_main(model->params.argc, model->params.argv);
418 bool ModelChecker::should_terminate_execution()
420 /* Infeasible -> don't take any more steps */
421 if (execution->is_infeasible())
423 else if (execution->isfeasibleprefix() && execution->have_bug_reports()) {
424 execution->set_assert();
428 if (execution->too_many_steps())
433 /** @brief Run ModelChecker for the user program */
434 void ModelChecker::run()
438 Thread *t = new Thread(execution->get_next_id(), &user_thread, &user_main_wrapper, NULL, NULL);
439 execution->add_thread(t);
443 * Stash next pending action(s) for thread(s). There
444 * should only need to stash one thread's action--the
445 * thread which just took a step--plus the first step
446 * for any newly-created thread
448 for (unsigned int i = 0; i < execution->get_num_threads(); i++) {
449 thread_id_t tid = int_to_id(i);
450 Thread *thr = get_thread(tid);
451 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
452 switch_from_master(thr);
453 if (thr->is_waiting_on(thr))
454 assert_bug("Deadlock detected (thread %u)", i);
458 /* Don't schedule threads which should be disabled */
459 for (unsigned int i = 0; i < get_num_threads(); i++) {
460 Thread *th = get_thread(int_to_id(i));
461 ModelAction *act = th->get_pending();
462 if (act && is_enabled(th) && !execution->check_action_enabled(act)) {
463 scheduler->sleep(th);
467 /* Catch assertions from prior take_step or from
468 * between-ModelAction bugs (e.g., data races) */
469 if (execution->has_asserted())
473 t = get_next_thread();
474 if (!t || t->is_model_thread())
477 /* Consume the next action for a Thread */
478 ModelAction *curr = t->get_pending();
479 t->set_pending(NULL);
480 t = execution->take_step(curr);
481 } while (!should_terminate_execution());
483 } while (next_execution());
485 execution->fixup_release_sequences();
487 model_print("******* Model-checking complete: *******\n");