10 #include "snapshot-interface.h"
13 #include "threads-model.h"
15 #include "traceanalysis.h"
16 #include "execution.h"
17 #include "bugmessage.h"
19 #define INITIAL_THREAD_ID 0
23 /** @brief Constructor */
24 ModelChecker::ModelChecker(struct model_params params) :
25 /* Initialize default scheduler */
27 scheduler(new Scheduler()),
28 node_stack(new NodeStack()),
29 execution(new ModelExecution(¶ms, scheduler, node_stack)),
31 earliest_diverge(NULL),
36 /** @brief Destructor */
37 ModelChecker::~ModelChecker()
40 for (unsigned int i = 0; i < trace_analyses.size(); i++)
41 delete trace_analyses[i];
46 * Restores user program to initial state and resets all model-checker data
49 void ModelChecker::reset_to_initial_state()
51 DEBUG("+++ Resetting to initial state +++\n");
52 node_stack->reset_execution();
55 * FIXME: if we utilize partial rollback, we will need to free only
56 * those pending actions which were NOT pending before the rollback
59 for (unsigned int i = 0; i < get_num_threads(); i++)
60 delete get_thread(int_to_id(i))->get_pending();
62 snapshot_backtrack_before(0);
65 /** @return the number of user threads created during this execution */
66 unsigned int ModelChecker::get_num_threads() const
68 return execution->get_num_threads();
72 * Must be called from user-thread context (e.g., through the global
73 * thread_current() interface)
75 * @return The currently executing Thread.
77 Thread * ModelChecker::get_current_thread() const
79 return scheduler->get_current_thread();
83 * @brief Choose the next thread to execute.
85 * This function chooses the next thread that should execute. It can enforce
86 * execution replay/backtracking or, if the model-checker has no preference
87 * regarding the next thread (i.e., when exploring a new execution ordering),
88 * we defer to the scheduler.
90 * @return The next chosen thread to run, if any exist. Or else if the current
91 * execution should terminate, return NULL.
93 Thread * ModelChecker::get_next_thread()
98 * Have we completed exploring the preselected path? Then let the
102 return scheduler->select_next_thread(node_stack->get_head());
105 /* Else, we are trying to replay an execution */
106 ModelAction *next = node_stack->get_next()->get_action();
108 if (next == diverge) {
109 if (earliest_diverge == NULL || *diverge < *earliest_diverge)
110 earliest_diverge = diverge;
112 Node *nextnode = next->get_node();
113 Node *prevnode = nextnode->get_parent();
114 scheduler->update_sleep_set(prevnode);
116 /* Reached divergence point */
117 if (nextnode->increment_behaviors()) {
118 /* Execute the same thread with a new behavior */
119 tid = next->get_tid();
120 node_stack->pop_restofstack(2);
123 /* Make a different thread execute for next step */
124 scheduler->add_sleep(get_thread(next->get_tid()));
125 tid = prevnode->get_next_backtrack();
126 /* Make sure the backtracked thread isn't sleeping. */
127 node_stack->pop_restofstack(1);
128 if (diverge == earliest_diverge) {
129 earliest_diverge = prevnode->get_action();
132 /* Start the round robin scheduler from this thread id */
133 scheduler->set_scheduler_thread(tid);
134 /* The correct sleep set is in the parent node. */
137 DEBUG("*** Divergence point ***\n");
141 tid = next->get_tid();
143 DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
144 ASSERT(tid != THREAD_ID_T_NONE);
145 return get_thread(id_to_int(tid));
149 * We need to know what the next actions of all threads in the sleep
150 * set will be. This method computes them and stores the actions at
151 * the corresponding thread object's pending action.
153 void ModelChecker::execute_sleep_set()
155 for (unsigned int i = 0; i < get_num_threads(); i++) {
156 thread_id_t tid = int_to_id(i);
157 Thread *thr = get_thread(tid);
158 if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
159 thr->get_pending()->set_sleep_flag();
165 * @brief Assert a bug in the executing program.
167 * Use this function to assert any sort of bug in the user program. If the
168 * current trace is feasible (actually, a prefix of some feasible execution),
169 * then this execution will be aborted, printing the appropriate message. If
170 * the current trace is not yet feasible, the error message will be stashed and
171 * printed if the execution ever becomes feasible.
173 * @param msg Descriptive message for the bug (do not include newline char)
174 * @return True if bug is immediately-feasible
176 bool ModelChecker::assert_bug(const char *msg, ...)
182 vsnprintf(str, sizeof(str), msg, ap);
185 return execution->assert_bug(str);
189 * @brief Assert a bug in the executing program, asserted by a user thread
190 * @see ModelChecker::assert_bug
191 * @param msg Descriptive message for the bug (do not include newline char)
193 void ModelChecker::assert_user_bug(const char *msg)
195 /* If feasible bug, bail out now */
197 switch_to_master(NULL);
200 /** @brief Print bug report listing for this execution (if any bugs exist) */
201 void ModelChecker::print_bugs() const
203 if (execution->have_bug_reports()) {
204 SnapVector<bug_message *> *bugs = execution->get_bugs();
206 model_print("Bug report: %zu bug%s detected\n",
208 bugs->size() > 1 ? "s" : "");
209 for (unsigned int i = 0; i < bugs->size(); i++)
215 * @brief Record end-of-execution stats
217 * Must be run when exiting an execution. Records various stats.
218 * @see struct execution_stats
220 void ModelChecker::record_stats()
223 if (!execution->isfeasibleprefix())
224 stats.num_infeasible++;
225 else if (execution->have_bug_reports())
226 stats.num_buggy_executions++;
227 else if (execution->is_complete_execution())
228 stats.num_complete++;
230 stats.num_redundant++;
233 * @todo We can violate this ASSERT() when fairness/sleep sets
234 * conflict to cause an execution to terminate, e.g. with:
235 * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
237 //ASSERT(scheduler->all_threads_sleeping());
241 /** @brief Print execution stats */
242 void ModelChecker::print_stats() const
244 model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
245 model_print("Number of redundant executions: %d\n", stats.num_redundant);
246 model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
247 model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
248 model_print("Total executions: %d\n", stats.num_total);
249 model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
253 * @brief End-of-exeuction print
254 * @param printbugs Should any existing bugs be printed?
256 void ModelChecker::print_execution(bool printbugs) const
258 print_program_output();
260 if (params.verbose) {
261 model_print("Earliest divergence point since last feasible execution:\n");
262 if (earliest_diverge)
263 earliest_diverge->print();
265 model_print("(Not set)\n");
271 /* Don't print invalid bugs */
276 execution->print_summary();
280 * Queries the model-checker for more executions to explore and, if one
281 * exists, resets the model-checker state to execute a new execution.
283 * @return If there are more executions to explore, return true. Otherwise,
286 bool ModelChecker::next_execution()
289 /* Is this execution a feasible execution that's worth bug-checking? */
290 bool complete = execution->isfeasibleprefix() &&
291 (execution->is_complete_execution() ||
292 execution->have_bug_reports());
294 /* End-of-execution bug checks */
296 if (execution->is_deadlocked())
297 assert_bug("Deadlock detected");
300 run_trace_analyses();
306 if (params.verbose || (complete && execution->have_bug_reports()))
307 print_execution(complete);
309 clear_program_output();
312 earliest_diverge = NULL;
314 if ((diverge = execution->get_next_backtrack()) == NULL)
318 model_print("Next execution will diverge at:\n");
322 execution->increment_execution_number();
323 reset_to_initial_state();
327 /** @brief Run trace analyses on complete trace */
328 void ModelChecker::run_trace_analyses() {
329 for (unsigned int i = 0; i < trace_analyses.size(); i++)
330 trace_analyses[i]->analyze(execution->get_action_trace());
334 * @brief Get a Thread reference by its ID
335 * @param tid The Thread's ID
336 * @return A Thread reference
338 Thread * ModelChecker::get_thread(thread_id_t tid) const
340 return execution->get_thread(tid);
344 * @brief Get a reference to the Thread in which a ModelAction was executed
345 * @param act The ModelAction
346 * @return A Thread reference
348 Thread * ModelChecker::get_thread(const ModelAction *act) const
350 return execution->get_thread(act);
354 * @brief Check if a Thread is currently enabled
355 * @param t The Thread to check
356 * @return True if the Thread is currently enabled
358 bool ModelChecker::is_enabled(Thread *t) const
360 return scheduler->is_enabled(t);
364 * @brief Check if a Thread is currently enabled
365 * @param tid The ID of the Thread to check
366 * @return True if the Thread is currently enabled
368 bool ModelChecker::is_enabled(thread_id_t tid) const
370 return scheduler->is_enabled(tid);
374 * Switch from a model-checker context to a user-thread context. This is the
375 * complement of ModelChecker::switch_to_master and must be called from the
376 * model-checker context
378 * @param thread The user-thread to switch to
380 void ModelChecker::switch_from_master(Thread *thread)
382 scheduler->set_current_thread(thread);
383 Thread::swap(&system_context, thread);
387 * Switch from a user-context to the "master thread" context (a.k.a. system
388 * context). This switch is made with the intention of exploring a particular
389 * model-checking action (described by a ModelAction object). Must be called
390 * from a user-thread context.
392 * @param act The current action that will be explored. May be NULL only if
393 * trace is exiting via an assertion (see ModelExecution::set_assert and
394 * ModelExecution::has_asserted).
395 * @return Return the value returned by the current action
397 uint64_t ModelChecker::switch_to_master(ModelAction *act)
400 Thread *old = thread_current();
401 scheduler->set_current_thread(NULL);
402 ASSERT(!old->get_pending());
403 old->set_pending(act);
404 if (Thread::swap(old, &system_context) < 0) {
405 perror("swap threads");
408 return old->get_return_value();
411 /** Wrapper to run the user's main function, with appropriate arguments */
412 void user_main_wrapper(void *)
414 user_main(model->params.argc, model->params.argv);
417 bool ModelChecker::should_terminate_execution()
419 /* Infeasible -> don't take any more steps */
420 if (execution->is_infeasible())
422 else if (execution->isfeasibleprefix() && execution->have_bug_reports()) {
423 execution->set_assert();
427 if (execution->too_many_steps())
432 /** @brief Run ModelChecker for the user program */
433 void ModelChecker::run()
437 Thread *t = new Thread(execution->get_next_id(), &user_thread, &user_main_wrapper, NULL, NULL);
438 execution->add_thread(t);
442 * Stash next pending action(s) for thread(s). There
443 * should only need to stash one thread's action--the
444 * thread which just took a step--plus the first step
445 * for any newly-created thread
447 for (unsigned int i = 0; i < execution->get_num_threads(); i++) {
448 thread_id_t tid = int_to_id(i);
449 Thread *thr = get_thread(tid);
450 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
451 switch_from_master(thr);
452 if (thr->is_waiting_on(thr))
453 assert_bug("Deadlock detected (thread %u)", i);
457 /* Don't schedule threads which should be disabled */
458 for (unsigned int i = 0; i < get_num_threads(); i++) {
459 Thread *th = get_thread(int_to_id(i));
460 ModelAction *act = th->get_pending();
461 if (act && is_enabled(th) && !execution->check_action_enabled(act)) {
462 scheduler->sleep(th);
466 /* Catch assertions from prior take_step or from
467 * between-ModelAction bugs (e.g., data races) */
468 if (execution->has_asserted())
472 t = get_next_thread();
473 if (!t || t->is_model_thread())
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());
482 } while (next_execution());
484 execution->fixup_release_sequences();
486 model_print("******* Model-checking complete: *******\n");