1 /* Copyright (c) 2016-2022. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "src/mc/checker/SafetyChecker.hpp"
7 #include "src/mc/Session.hpp"
8 #include "src/mc/VisitedState.hpp"
9 #include "src/mc/api/Transition.hpp"
10 #include "src/mc/mc_config.hpp"
11 #include "src/mc/mc_exit.hpp"
12 #include "src/mc/mc_private.hpp"
13 #include "src/mc/mc_record.hpp"
15 #include "src/xbt/mmalloc/mmprivate.h"
17 #include "xbt/sysdep.h"
26 using api = simgrid::mc::Api;
28 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_safety, mc, "Logging specific to MC safety verification ");
33 xbt::signal<void()> SafetyChecker::on_exploration_start_signal;
34 xbt::signal<void()> SafetyChecker::on_backtracking_signal;
36 xbt::signal<void(State*)> SafetyChecker::on_state_creation_signal;
38 xbt::signal<void(State*)> SafetyChecker::on_restore_system_state_signal;
39 xbt::signal<void()> SafetyChecker::on_restore_initial_state_signal;
40 xbt::signal<void(Transition*)> SafetyChecker::on_transition_replay_signal;
41 xbt::signal<void(Transition*)> SafetyChecker::on_transition_execute_signal;
43 xbt::signal<void()> SafetyChecker::on_log_state_signal;
45 void SafetyChecker::check_non_termination(const State* current_state)
47 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
48 if (api::get().snapshot_equal((*state)->system_state_.get(), current_state->system_state_.get())) {
49 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", (*state)->num_, current_state->num_);
50 XBT_INFO("******************************************");
51 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
52 XBT_INFO("******************************************");
53 XBT_INFO("Counter-example execution trace:");
54 for (auto const& s : get_textual_trace())
55 XBT_INFO(" %s", s.c_str());
56 XBT_INFO("Path = %s", get_record_trace().to_string().c_str());
57 api::get().log_state();
59 throw TerminationError();
63 RecordTrace SafetyChecker::get_record_trace() // override
66 for (auto const& state : stack_)
67 res.push_back(state->get_transition());
71 std::vector<std::string> SafetyChecker::get_textual_trace() // override
73 std::vector<std::string> trace;
74 for (auto const& state : stack_)
75 trace.push_back(state->get_transition()->to_string());
79 void SafetyChecker::log_state() // override
81 on_log_state_signal();
82 XBT_INFO("DFS exploration ended. %ld unique states visited; %ld backtracks (%lu transition replays, %lu states "
84 State::get_expanded_states(), backtrack_count_, api::get().mc_get_visited_states(),
85 Transition::get_replayed_transitions());
88 void SafetyChecker::run()
90 on_exploration_start_signal();
91 /* This function runs the DFS algorithm the state space.
92 * We do so iteratively instead of recursively, dealing with the call stack manually.
93 * This allows one to explore the call stack at will. */
95 while (not stack_.empty()) {
96 /* Get current state */
97 State* state = stack_.back().get();
99 XBT_DEBUG("**************************************************");
100 XBT_VERB("Exploration depth=%zu (state=%p, num %ld)(%zu interleave)", stack_.size(), state, state->num_,
101 state->count_todo());
103 api::get().mc_inc_visited_states();
105 // Backtrack if we reached the maximum depth
106 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
107 if (reductionMode_ == ReductionMode::dpor) {
108 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
109 _sg_mc_max_depth.get());
110 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
112 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
117 // Backtrack if we are revisiting a state we saw previously
118 if (visited_state_ != nullptr) {
119 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
120 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
122 visited_state_ = nullptr;
127 // Search for the next transition
128 int next = state->next_transition();
130 if (next < 0) { // If there is no more transition in the current state, backtrack.
131 XBT_DEBUG("There remains %zu actors, but none to interleave (depth %zu).",
132 mc_model_checker->get_remote_process().actors().size(), stack_.size() + 1);
134 if (mc_model_checker->get_remote_process().actors().empty())
135 mc_model_checker->finalize_app();
140 /* Actually answer the request: let's execute the selected request (MCed does one step) */
141 state->execute_next(next);
142 on_transition_execute_signal(state->get_transition());
144 // If there are processes to interleave and the maximum depth has not been
145 // reached then perform one step of the exploration algorithm.
146 XBT_DEBUG("Execute: %s", state->get_transition()->to_string().c_str());
149 if (dot_output != nullptr)
150 req_str = api::get().request_get_dot_output(state->get_transition());
152 /* Create the new expanded state (copy the state of MCed into our MCer data) */
153 auto next_state = std::make_unique<State>();
154 on_state_creation_signal(next_state.get());
156 if (_sg_mc_termination)
157 this->check_non_termination(next_state.get());
159 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
160 if (_sg_mc_max_visited_states > 0)
161 visited_state_ = visited_states_.addVisitedState(next_state->num_, next_state.get(), true);
163 /* If this is a new state (or if we don't care about state-equality reduction) */
164 if (visited_state_ == nullptr) {
165 /* Get an enabled process and insert it in the interleave set of the next state */
166 auto actors = api::get().get_actors();
167 for (auto& remoteActor : actors) {
168 auto actor = remoteActor.copy.get_buffer();
169 if (get_session().actor_is_enabled(actor->get_pid())) {
170 next_state->mark_todo(actor->get_pid());
171 if (reductionMode_ == ReductionMode::dpor)
172 break; // With DPOR, we take the first enabled transition
176 if (dot_output != nullptr)
177 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
179 } else if (dot_output != nullptr)
180 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_,
181 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
184 stack_.push_back(std::move(next_state));
187 api::get().log_state();
190 void SafetyChecker::backtrack()
193 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
194 on_backtracking_signal();
197 api::get().mc_check_deadlock();
199 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
200 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
201 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
202 * interleave set of the state that executed that previous request. */
204 while (not stack_.empty()) {
205 std::unique_ptr<State> state = std::move(stack_.back());
207 if (reductionMode_ == ReductionMode::dpor) {
208 aid_t issuer_id = state->get_transition()->aid_;
209 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
210 State* prev_state = i->get();
211 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
212 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
213 prev_state->get_transition()->to_string().c_str(), issuer_id);
215 } else if (prev_state->get_transition()->depends(state->get_transition())) {
216 XBT_VERB("Dependent Transitions:");
217 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
218 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
220 if (not prev_state->actor_states_[issuer_id].is_done())
221 prev_state->mark_todo(issuer_id);
223 XBT_DEBUG("Actor %ld is in done set", issuer_id);
226 XBT_VERB("INDEPENDENT Transitions:");
227 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
228 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
233 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
234 /* We found a back-tracking point, let's loop */
235 XBT_DEBUG("Back-tracking to state %ld at depth %zu", state->num_, stack_.size() + 1);
236 stack_.push_back(std::move(state));
237 this->restore_state();
238 XBT_DEBUG("Back-tracking to state %ld at depth %zu done", stack_.back()->num_, stack_.size());
241 XBT_DEBUG("Delete state %ld at depth %zu", state->num_, stack_.size() + 1);
246 void SafetyChecker::restore_state()
248 /* If asked to rollback on a state that has a snapshot, restore it */
249 State* last_state = stack_.back().get();
250 if (last_state->system_state_) {
251 api::get().restore_state(last_state->system_state_);
252 on_restore_system_state_signal(last_state);
256 /* if no snapshot, we need to restore the initial state and replay the transitions */
257 get_session().restore_initial_state();
258 on_restore_initial_state_signal();
260 /* Traverse the stack from the state at position start and re-execute the transitions */
261 for (std::unique_ptr<State> const& state : stack_) {
262 if (state == stack_.back()) // If we are arrived on the target state, don't replay the outgoing transition *.
264 state->get_transition()->replay();
265 on_transition_replay_signal(state->get_transition());
266 /* Update statistics */
267 api::get().mc_inc_visited_states();
271 SafetyChecker::SafetyChecker(Session* session) : Checker(session)
273 reductionMode_ = reduction_mode;
274 if (_sg_mc_termination)
275 reductionMode_ = ReductionMode::none;
276 else if (reductionMode_ == ReductionMode::unset)
277 reductionMode_ = ReductionMode::dpor;
279 if (_sg_mc_termination)
280 XBT_INFO("Check non progressive cycles");
282 XBT_INFO("Start a DFS exploration. Reduction is: %s.",
283 (reductionMode_ == ReductionMode::none ? "none"
284 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
286 get_session().take_initial_snapshot();
288 XBT_DEBUG("Starting the safety algorithm");
290 auto initial_state = std::make_unique<State>();
292 XBT_DEBUG("**************************************************");
294 /* Get an enabled actor and insert it in the interleave set of the initial state */
295 auto actors = api::get().get_actors();
296 XBT_DEBUG("Initial state. %zu actors to consider", actors.size());
297 for (auto& actor : actors) {
298 aid_t aid = actor.copy.get_buffer()->get_pid();
299 if (get_session().actor_is_enabled(aid)) {
300 initial_state->mark_todo(aid);
301 if (reductionMode_ == ReductionMode::dpor) {
302 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", aid);
305 XBT_DEBUG("Actor %ld is TODO", aid);
309 stack_.push_back(std::move(initial_state));
312 Checker* create_safety_checker(Session* session)
314 return new SafetyChecker(session);
318 } // namespace simgrid