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/explo/SafetyChecker.hpp"
7 #include "src/mc/Session.hpp"
8 #include "src/mc/VisitedState.hpp"
9 #include "src/mc/mc_config.hpp"
10 #include "src/mc/mc_exit.hpp"
11 #include "src/mc/mc_private.hpp"
12 #include "src/mc/mc_record.hpp"
13 #include "src/mc/transition/Transition.hpp"
15 #include "src/xbt/mmalloc/mmprivate.h"
17 #include "xbt/sysdep.h"
26 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_safety, mc, "Logging specific to MC safety verification ");
31 xbt::signal<void()> SafetyChecker::on_exploration_start_signal;
32 xbt::signal<void()> SafetyChecker::on_backtracking_signal;
34 xbt::signal<void(State*)> SafetyChecker::on_state_creation_signal;
36 xbt::signal<void(State*)> SafetyChecker::on_restore_system_state_signal;
37 xbt::signal<void()> SafetyChecker::on_restore_initial_state_signal;
38 xbt::signal<void(Transition*)> SafetyChecker::on_transition_replay_signal;
39 xbt::signal<void(Transition*)> SafetyChecker::on_transition_execute_signal;
41 xbt::signal<void()> SafetyChecker::on_log_state_signal;
43 void SafetyChecker::check_non_termination(const State* current_state)
45 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
46 if (Api::get().snapshot_equal((*state)->system_state_.get(), current_state->system_state_.get())) {
47 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", (*state)->num_, current_state->num_);
48 XBT_INFO("******************************************");
49 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
50 XBT_INFO("******************************************");
51 XBT_INFO("Counter-example execution trace:");
52 for (auto const& s : get_textual_trace())
53 XBT_INFO(" %s", s.c_str());
54 XBT_INFO("Path = %s", get_record_trace().to_string().c_str());
57 throw TerminationError();
61 RecordTrace SafetyChecker::get_record_trace() // override
64 for (auto const& state : stack_)
65 res.push_back(state->get_transition());
69 std::vector<std::string> SafetyChecker::get_textual_trace() // override
71 std::vector<std::string> trace;
72 for (auto const& state : stack_)
73 trace.push_back(state->get_transition()->to_string());
77 void SafetyChecker::log_state() // override
79 on_log_state_signal();
80 XBT_INFO("DFS exploration ended. %ld unique states visited; %ld backtracks (%lu transition replays, %lu states "
82 State::get_expanded_states(), backtrack_count_, Api::get().mc_get_visited_states(),
83 Transition::get_replayed_transitions());
86 void SafetyChecker::run()
88 on_exploration_start_signal();
89 /* This function runs the DFS algorithm the state space.
90 * We do so iteratively instead of recursively, dealing with the call stack manually.
91 * This allows one to explore the call stack at will. */
93 while (not stack_.empty()) {
94 /* Get current state */
95 State* state = stack_.back().get();
97 XBT_DEBUG("**************************************************");
98 XBT_DEBUG("Exploration depth=%zu (state:%ld; %zu interleaves)", stack_.size(), state->num_, state->count_todo());
100 Api::get().mc_inc_visited_states();
102 // Backtrack if we reached the maximum depth
103 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
104 if (reductionMode_ == ReductionMode::dpor) {
105 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
106 _sg_mc_max_depth.get());
107 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
109 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
114 // Backtrack if we are revisiting a state we saw previously
115 if (visited_state_ != nullptr) {
116 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
117 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
119 visited_state_ = nullptr;
124 // Search for the next transition
125 int next = state->next_transition();
127 if (next < 0) { // If there is no more transition in the current state, backtrack.
128 XBT_DEBUG("There remains %zu actors, but none to interleave (depth %zu).",
129 mc_model_checker->get_remote_process().actors().size(), stack_.size() + 1);
131 if (mc_model_checker->get_remote_process().actors().empty())
132 mc_model_checker->finalize_app();
137 /* Actually answer the request: let's execute the selected request (MCed does one step) */
138 state->execute_next(next);
139 on_transition_execute_signal(state->get_transition());
141 // If there are processes to interleave and the maximum depth has not been
142 // reached then perform one step of the exploration algorithm.
143 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
144 state->get_transition()->to_string().c_str(), stack_.size(), state->num_, state->count_todo());
147 if (dot_output != nullptr)
148 req_str = state->get_transition()->dot_string();
150 /* Create the new expanded state (copy the state of MCed into our MCer data) */
151 auto next_state = std::make_unique<State>();
152 on_state_creation_signal(next_state.get());
154 if (_sg_mc_termination)
155 this->check_non_termination(next_state.get());
157 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
158 if (_sg_mc_max_visited_states > 0)
159 visited_state_ = visited_states_.addVisitedState(next_state->num_, next_state.get(), true);
161 /* If this is a new state (or if we don't care about state-equality reduction) */
162 if (visited_state_ == nullptr) {
163 /* Get an enabled process and insert it in the interleave set of the next state */
164 auto actors = Api::get().get_actors();
165 for (auto& remoteActor : actors) {
166 auto actor = remoteActor.copy.get_buffer();
167 if (get_session().actor_is_enabled(actor->get_pid())) {
168 next_state->mark_todo(actor->get_pid());
169 if (reductionMode_ == ReductionMode::dpor)
170 break; // With DPOR, we take the first enabled transition
174 if (dot_output != nullptr)
175 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
177 } else if (dot_output != nullptr)
178 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_,
179 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
182 stack_.push_back(std::move(next_state));
188 void SafetyChecker::backtrack()
191 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
192 on_backtracking_signal();
195 session_singleton->check_deadlock();
197 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
198 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
199 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
200 * interleave set of the state that executed that previous request. */
202 while (not stack_.empty()) {
203 std::unique_ptr<State> state = std::move(stack_.back());
205 if (reductionMode_ == ReductionMode::dpor) {
206 aid_t issuer_id = state->get_transition()->aid_;
207 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
208 State* prev_state = i->get();
209 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
210 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
211 prev_state->get_transition()->to_string().c_str(), issuer_id);
213 } else if (prev_state->get_transition()->depends(state->get_transition())) {
214 XBT_VERB("Dependent Transitions:");
215 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
216 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
218 if (not prev_state->actor_states_[issuer_id].is_done())
219 prev_state->mark_todo(issuer_id);
221 XBT_DEBUG("Actor %ld is in done set", issuer_id);
224 XBT_VERB("INDEPENDENT Transitions:");
225 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
226 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
231 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
232 /* We found a back-tracking point, let's loop */
233 XBT_DEBUG("Back-tracking to state %ld at depth %zu", state->num_, stack_.size() + 1);
235 std::move(state)); // Put it back on the stack from which it was removed earlier in this while loop
236 this->restore_state();
237 XBT_DEBUG("Back-tracking to state %ld at depth %zu done", stack_.back()->num_, stack_.size());
240 XBT_DEBUG("Delete state %ld at depth %zu", state->num_, stack_.size() + 1);
245 void SafetyChecker::restore_state()
247 /* If asked to rollback on a state that has a snapshot, restore it */
248 State* last_state = stack_.back().get();
249 if (last_state->system_state_) {
250 Api::get().restore_state(last_state->system_state_);
251 on_restore_system_state_signal(last_state);
255 /* if no snapshot, we need to restore the initial state and replay the transitions */
256 get_session().restore_initial_state();
257 on_restore_initial_state_signal();
259 /* Traverse the stack from the state at position start and re-execute the transitions */
260 for (std::unique_ptr<State> const& state : stack_) {
261 if (state == stack_.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
263 state->get_transition()->replay();
264 on_transition_replay_signal(state->get_transition());
265 /* Update statistics */
266 Api::get().mc_inc_visited_states();
270 SafetyChecker::SafetyChecker(Session* session) : Exploration(session)
272 reductionMode_ = reduction_mode;
273 if (_sg_mc_termination)
274 reductionMode_ = ReductionMode::none;
275 else if (reductionMode_ == ReductionMode::unset)
276 reductionMode_ = ReductionMode::dpor;
278 if (_sg_mc_termination)
279 XBT_INFO("Check non progressive cycles");
281 XBT_INFO("Start a DFS exploration. Reduction is: %s.",
282 (reductionMode_ == ReductionMode::none ? "none"
283 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
285 get_session().take_initial_snapshot();
287 XBT_DEBUG("Starting the safety algorithm");
289 auto initial_state = std::make_unique<State>();
291 XBT_DEBUG("**************************************************");
293 /* Get an enabled actor and insert it in the interleave set of the initial state */
294 auto actors = Api::get().get_actors();
295 XBT_DEBUG("Initial state. %zu actors to consider", actors.size());
296 for (auto& actor : actors) {
297 aid_t aid = actor.copy.get_buffer()->get_pid();
298 if (get_session().actor_is_enabled(aid)) {
299 initial_state->mark_todo(aid);
300 if (reductionMode_ == ReductionMode::dpor) {
301 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", aid);
304 XBT_DEBUG("Actor %ld is TODO", aid);
308 stack_.push_back(std::move(initial_state));
311 Exploration* create_safety_checker(Session* session)
313 return new SafetyChecker(session);
317 } // namespace simgrid