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 void SafetyChecker::check_non_termination(const State* current_state)
35 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
36 if (api::get().snapshot_equal((*state)->system_state_.get(), current_state->system_state_.get())) {
37 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", (*state)->num_, current_state->num_);
38 XBT_INFO("******************************************");
39 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
40 XBT_INFO("******************************************");
41 XBT_INFO("Counter-example execution trace:");
42 for (auto const& s : get_textual_trace())
43 XBT_INFO(" %s", s.c_str());
44 XBT_INFO("Path = %s", get_record_trace().to_string().c_str());
45 api::get().log_state();
47 throw TerminationError();
51 RecordTrace SafetyChecker::get_record_trace() // override
54 for (auto const& state : stack_)
55 res.push_back(state->get_transition());
59 std::vector<std::string> SafetyChecker::get_textual_trace() // override
61 std::vector<std::string> trace;
62 for (auto const& state : stack_)
63 trace.push_back(state->get_transition()->to_string());
67 void SafetyChecker::log_state() // override
69 XBT_INFO("%ld unique states visited; %ld backtracks (%lu transition replays, %lu states visited overall)",
70 State::get_expanded_states(), backtrack_count_, api::get().mc_get_visited_states(),
71 Transition::get_replayed_transitions());
74 void SafetyChecker::run()
76 /* This function runs the DFS algorithm the state space.
77 * We do so iteratively instead of recursively, dealing with the call stack manually.
78 * This allows one to explore the call stack at will. */
80 while (not stack_.empty()) {
81 /* Get current state */
82 State* state = stack_.back().get();
84 XBT_DEBUG("**************************************************");
85 XBT_VERB("Exploration depth=%zu (state=%p, num %ld)(%zu interleave)", stack_.size(), state, state->num_,
88 api::get().mc_inc_visited_states();
90 // Backtrack if we reached the maximum depth
91 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
92 if (reductionMode_ == ReductionMode::dpor) {
93 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
94 _sg_mc_max_depth.get());
95 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
97 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
102 // Backtrack if we are revisiting a state we saw previously
103 if (visited_state_ != nullptr) {
104 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
105 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
107 visited_state_ = nullptr;
112 // Search for the next transition
113 int next = state->next_transition();
115 if (next < 0) { // If there is no more transition in the current state, backtrack.
117 XBT_DEBUG("There remains %zu actors, but none to interleave (depth %zu).",
118 mc_model_checker->get_remote_process().actors().size(), stack_.size() + 1);
120 if (mc_model_checker->get_remote_process().actors().empty())
121 mc_model_checker->finalize_app();
126 /* Actually answer the request: let's execute the selected request (MCed does one step) */
127 state->execute_next(next);
129 // If there are processes to interleave and the maximum depth has not been
130 // reached then perform one step of the exploration algorithm.
131 XBT_DEBUG("Execute: %s", state->get_transition()->to_string().c_str());
134 if (dot_output != nullptr)
135 req_str = api::get().request_get_dot_output(state->get_transition());
137 /* Create the new expanded state (copy the state of MCed into our MCer data) */
138 auto next_state = std::make_unique<State>();
140 if (_sg_mc_termination)
141 this->check_non_termination(next_state.get());
143 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
144 if (_sg_mc_max_visited_states > 0)
145 visited_state_ = visited_states_.addVisitedState(next_state->num_, next_state.get(), true);
147 /* If this is a new state (or if we don't care about state-equality reduction) */
148 if (visited_state_ == nullptr) {
149 /* Get an enabled process and insert it in the interleave set of the next state */
150 auto actors = api::get().get_actors();
151 for (auto& remoteActor : actors) {
152 auto actor = remoteActor.copy.get_buffer();
153 if (get_session().actor_is_enabled(actor->get_pid())) {
154 next_state->mark_todo(actor->get_pid());
155 if (reductionMode_ == ReductionMode::dpor)
156 break; // With DPOR, we take the first enabled transition
160 if (dot_output != nullptr)
161 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
163 } else if (dot_output != nullptr)
164 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_,
165 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
168 stack_.push_back(std::move(next_state));
171 XBT_INFO("No property violation found.");
172 api::get().log_state();
175 void SafetyChecker::backtrack()
178 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
181 api::get().mc_check_deadlock();
183 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
184 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
185 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
186 * interleave set of the state that executed that previous request. */
188 while (not stack_.empty()) {
189 std::unique_ptr<State> state = std::move(stack_.back());
191 if (reductionMode_ == ReductionMode::dpor) {
192 aid_t issuer_id = state->get_transition()->aid_;
193 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
194 State* prev_state = i->get();
195 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
196 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
197 prev_state->get_transition()->to_string().c_str(), issuer_id);
199 } else if (prev_state->get_transition()->depends(state->get_transition())) {
200 XBT_VERB("Dependent Transitions:");
201 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
202 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
204 if (not prev_state->actor_states_[issuer_id].is_done())
205 prev_state->mark_todo(issuer_id);
207 XBT_DEBUG("Actor %ld is in done set", issuer_id);
210 XBT_VERB("INDEPENDENT Transitions:");
211 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
212 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
217 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
218 /* We found a back-tracking point, let's loop */
219 XBT_DEBUG("Back-tracking to state %ld at depth %zu", state->num_, stack_.size() + 1);
220 stack_.push_back(std::move(state));
221 this->restore_state();
222 XBT_DEBUG("Back-tracking to state %ld at depth %zu done", stack_.back()->num_, stack_.size());
225 XBT_DEBUG("Delete state %ld at depth %zu", state->num_, stack_.size() + 1);
230 void SafetyChecker::restore_state()
232 /* Intermediate backtracking */
233 const State* last_state = stack_.back().get();
234 if (last_state->system_state_) {
235 api::get().restore_state(last_state->system_state_);
239 get_session().restore_initial_state();
241 /* Traverse the stack from the state at position start and re-execute the transitions */
242 for (std::unique_ptr<State> const& state : stack_) {
243 if (state == stack_.back())
245 state->get_transition()->replay();
246 /* Update statistics */
247 api::get().mc_inc_visited_states();
251 SafetyChecker::SafetyChecker(Session* session) : Checker(session)
253 reductionMode_ = reduction_mode;
254 if (_sg_mc_termination)
255 reductionMode_ = ReductionMode::none;
256 else if (reductionMode_ == ReductionMode::unset)
257 reductionMode_ = ReductionMode::dpor;
259 if (_sg_mc_termination)
260 XBT_INFO("Check non progressive cycles");
262 XBT_INFO("Check a safety property. Reduction is: %s.",
263 (reductionMode_ == ReductionMode::none ? "none"
264 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
266 get_session().take_initial_snapshot();
268 XBT_DEBUG("Starting the safety algorithm");
270 auto initial_state = std::make_unique<State>();
272 XBT_DEBUG("**************************************************");
274 /* Get an enabled actor and insert it in the interleave set of the initial state */
275 auto actors = api::get().get_actors();
276 XBT_DEBUG("Initial state. %zu actors to consider", actors.size());
277 for (auto& actor : actors) {
278 aid_t aid = actor.copy.get_buffer()->get_pid();
279 if (get_session().actor_is_enabled(aid)) {
280 initial_state->mark_todo(aid);
281 if (reductionMode_ == ReductionMode::dpor) {
282 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", aid);
285 XBT_DEBUG("Actor %ld is TODO", aid);
289 stack_.push_back(std::move(initial_state));
292 Checker* create_safety_checker(Session* session)
294 return new SafetyChecker(session);
298 } // namespace simgrid